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Saturday, April 24, 2021

Surgery

From Wikipedia, the free encyclopedia
 

Surgeons conducting Operations

Surgery is a medical or dental specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pathological condition such as a disease or injury, to help improve bodily function, appearance, or to repair unwanted ruptured areas.

The act of performing surgery may be called a surgical procedure, operation, or simply "surgery". In this context, the verb "operate" means to perform surgery. The adjective surgical means pertaining to surgery; e.g. surgical instruments or surgical nurse. The person or subject on which the surgery is performed can be a person or an animal. A surgeon is a person who practices surgery and a surgeon's assistant is a person who practices surgical assistance. A surgical team is made up of the surgeon, the surgeon's assistant, an anaesthetist, a circulating nurse and a surgical technologist. Surgery usually spans from minutes to hours, but it is typically not an ongoing or periodic type of treatment. The term "surgery" can also refer to the place where surgery is performed, or, in British English, simply the office of a physician, dentist, or veterinarian.

Definitions

Surgery is an invasive technique with the fundamental principle of physical intervention on organs/organ systems/tissues for diagnostic or therapeutic reasons.

As a general rule, a procedure is considered surgical when it involves cutting of a person's tissues or closure of a previously sustained wound. Other procedures that do not necessarily fall under this rubric, such as angioplasty or endoscopy, may be considered surgery if they involve "common" surgical procedure or settings, such as use of a sterile environment, anesthesia, antiseptic conditions, typical surgical instruments, and suturing or stapling. All forms of surgery are considered invasive procedures; so-called "noninvasive surgery" usually refers to an excision that does not penetrate the structure being excised (e.g. laser ablation of the cornea) or to a radiosurgical procedure (e.g. irradiation of a tumor).

Types of surgery

Surgical procedures are commonly categorized by urgency, type of procedure, body system involved, the degree of invasiveness, and special instrumentation.

  • Based on timing: Elective surgery is done to correct a non-life-threatening condition, and is carried out at the person's request, subject to the surgeon's and the surgical facility's availability. A semi-elective surgery is one that must be done to avoid permanent disability or death, but can be postponed for a short time. Emergency surgery is surgery which must be done without any delay to prevent death or serious disabilities and/or loss of limbs and functions.
  • Based on purpose: Exploratory surgery is performed to aid or confirm a diagnosis. Therapeutic surgery treats a previously diagnosed condition. Cosmetic surgery is done to subjectively improve the appearance of an otherwise normal structure.
  • By type of procedure: Amputation involves cutting off a body part, usually a limb or digit; castration is also an example. Resection is the removal of all of an internal organ or body part, or a key part (lung lobe; liver quadrant) of such an organ or body part that has its own name or code designation. A segmental resection can be of a smaller region of an organ such as a hepatic segment or a bronchopulmonary segment. Excision is the cutting out or removal of only part of an organ, tissue, or other body part from the person. Extirpation is the complete excision or surgical destruction of a body part. Replantation involves reattaching a severed body part. Reconstructive surgery involves reconstruction of an injured, mutilated, or deformed part of the body. Transplant surgery is the replacement of an organ or body part by insertion of another from different human (or animal) into the person undergoing surgery. Removing an organ or body part from a live human or animal for use in transplant is also a type of surgery.
  • By body part: When surgery is performed on one organ system or structure, it may be classed by the organ, organ system or tissue involved. Examples include cardiac surgery (performed on the heart), gastrointestinal surgery (performed within the digestive tract and its accessory organs), and orthopedic surgery (performed on bones or muscles).
  • By degree of invasiveness of surgical procedures: Minimally-invasive surgery involves smaller outer incisions to insert miniaturized instruments within a body cavity or structure, as in laparoscopic surgery or angioplasty. By contrast, an open surgical procedure such as a laparotomy requires a large incision to access the area of interest.
  • By equipment used: Laser surgery involves use of a laser for cutting tissue instead of a scalpel or similar surgical instruments. Microsurgery involves the use of an operating microscope for the surgeon to see small structures. Robotic surgery makes use of a surgical robot, such as the Da Vinci or the ZEUS robotic surgical systems, to control the instrumentation under the direction of the surgeon.

Terminology

  • Excision surgery names often start with a name for the organ to be excised (cut out) and end in -ectomy.
  • Procedures involving cutting into an organ or tissue end in -otomy. A surgical procedure cutting through the abdominal wall to gain access to the abdominal cavity is a laparotomy.
  • Minimally invasive procedures, involving small incisions through which an endoscope is inserted, end in -oscopy. For example, such surgery in the abdominal cavity is called laparoscopy.
  • Procedures for formation of a permanent or semi-permanent opening called a stoma in the body end in -ostomy.
  • Reconstruction, plastic or cosmetic surgery of a body part starts with a name for the body part to be reconstructed and ends in -oplasty. Rhino is used as a prefix for "nose", therefore a rhinoplasty is reconstructive or cosmetic surgery for the nose.
  • Repair of damaged or congenital abnormal structure ends in -rraphy.
  • Reoperation (return to the operating room) refers to a return to the operating theater after an initial surgery is performed to re-address an aspect of patient care best treated surgically. Reasons for reoperation include persistent bleeding after surgery, development of or persistence of infection.

Description of surgical procedure

Location

Inpatient surgery is performed in a hospital, and the person undergoing surgery stays at least one night in the hospital after the surgery. Outpatient surgery occurs in a hospital outpatient department or freestanding ambulatory surgery center, and the person who had surgery is discharged the same working day. Office surgery occurs in a physician's office, and the person is discharged the same working day.

At a hospital, modern surgery is often performed in an operating theater using surgical instruments, an operating table, and other equipment. Among United States hospitalizations for non-maternal and non-neonatal conditions in 2012, more than one-fourth of stays and half of hospital costs involved stays that included operating room (OR) procedures. The environment and procedures used in surgery are governed by the principles of aseptic technique: the strict separation of "sterile" (free of microorganisms) things from "unsterile" or "contaminated" things. All surgical instruments must be sterilized, and an instrument must be replaced or re-sterilized if, it becomes contaminated (i.e. handled in an unsterile manner, or allowed to touch an unsterile surface). Operating room staff must wear sterile attire (scrubs, a scrub cap, a sterile surgical gown, sterile latex or non-latex polymer gloves and a surgical mask), and they must scrub hands and arms with an approved disinfectant agent before each procedure.

Preoperative care

Prior to surgery, the person is given a medical examination, receives certain pre-operative tests, and their physical status is rated according to the ASA physical status classification system. If these results are satisfactory, the person requiring surgery signs a consent form and is given a surgical clearance. If the procedure is expected to result in significant blood loss, an autologous blood donation may be made some weeks prior to surgery. If the surgery involves the digestive system, the person requiring surgery may be instructed to perform a bowel prep by drinking a solution of polyethylene glycol the night before the procedure. People preparing for surgery are also instructed to abstain from food or drink (an NPO order after midnight on the night before the procedure), to minimize the effect of stomach contents on pre-operative medications and reduce the risk of aspiration if the person vomits during or after the procedure.

Some medical systems have a practice of routinely performing chest x-rays before surgery. The premise behind this practice is that the physician might discover some unknown medical condition which would complicate the surgery, and that upon discovering this with the chest x-ray, the physician would adapt the surgery practice accordingly. However, medical specialty professional organizations recommend against routine pre-operative chest x-rays for people who have an unremarkable medical history and presented with a physical exam which did not indicate a chest x-ray. Routine x-ray examination is more likely to result in problems like misdiagnosis, overtreatment, or other negative outcomes than it is to result in a benefit to the person. Likewise, other tests including complete blood count, prothrombin time, partial thromboplastin time, basic metabolic panel, and urinalysis should not be done unless the results of these tests can help evaluate surgical risk.

Staging for surgery

The pre-operative holding area is so important in the surgical phase since here is where most of the family members can see who the staff of the surgery will be, also this area is where the nurses in charge to give information to the family members of the patient. In the pre-operative holding area, the person preparing for surgery changes out of his or her street clothes and is asked to confirm the details of his or her surgery. A set of vital signs are recorded, a peripheral IV line is placed, and pre-operative medications (antibiotics, sedatives, etc.) are given. When the person enters the operating room, the skin surface to be operated on, called the operating field, is cleaned and prepared by applying an antiseptic (ideally chlorhexidine gluconate in alcoholic, as this is twice as effective as povidone-iodine for reduce the risk of infection. If hair is present at the surgical site, it is clipped off prior to prep application. The person is assisted by an anesthesiologist or resident to make a specific surgical position, then sterile drapes are used to cover the surgical site or at least a wide area surrounding the operating field; the drapes are clipped to a pair of poles near the head of the bed to form an "ether screen", which separates the anesthetist/anesthesiologist's working area (unsterile) from the surgical site (sterile).

Anesthesia is administered to prevent pain from an incision, tissue manipulation and suturing. Depending on the kind of operation, anesthesia may be provided locally or as general anesthesia. Spinal anesthesia may be used when the surgical site is too large or deep for a local block, but general anesthesia may not be desirable. With local and spinal anesthesia, the surgical site is anesthetized, but the person can remain conscious or minimally sedated. In contrast, general anesthesia renders the person unconscious and paralyzed during surgery. The person is intubated and is placed on a mechanical ventilator, and anesthesia is produced by a combination of injected and inhaled agents. Choice of surgical method and anesthetic technique aims to reduce the risk of complications, shorten the time needed for recovery and minimise the surgical stress response.

Intraoperative phase

The intraoperative phase begins when the surgery subject is received in the surgical area (such as the operating theater or surgical department), and lasts until the subject is transferred to a recovery area (such as a post-anesthesia care unit).

An incision is made to access the surgical site. Blood vessels may be clamped or cauterized to prevent bleeding, and retractors may be used to expose the site or keep the incision open. The approach to the surgical site may involve several layers of incision and dissection, as in abdominal surgery, where the incision must traverse skin, subcutaneous tissue, three layers of muscle and then the peritoneum. In certain cases, bone may be cut to further access the interior of the body; for example, cutting the skull for brain surgery or cutting the sternum for thoracic (chest) surgery to open up the rib cage. Whilst in surgery aseptic technique is used to prevent infection or further spreading of the disease. The surgeons' and assistants' hands, wrists and forearms are washed thoroughly for at least 4 minutes to prevent germs getting into the operative field, then sterile gloves are placed onto their hands. An antiseptic solution is applied to the area of the person's body that will be operated on. Sterile drapes are placed around the operative site. Surgical masks are worn by the surgical team to avoid germs on droplets of liquid from their mouths and noses from contaminating the operative site.

Work to correct the problem in body then proceeds. This work may involve:

  • excision – cutting out an organ, tumor, or other tissue.
  • resection – partial removal of an organ or other bodily structure.
  • reconnection of organs, tissues, etc., particularly if severed. Resection of organs such as intestines involves reconnection. Internal suturing or stapling may be used. Surgical connection between blood vessels or other tubular or hollow structures such as loops of intestine is called anastomosis.
  • reduction – the movement or realignment of a body part to its normal position. e.g. Reduction of a broken nose involves the physical manipulation of the bone or cartilage from their displaced state back to their original position to restore normal airflow and aesthetics.
  • ligation – tying off blood vessels, ducts, or "tubes".
  • grafts – may be severed pieces of tissue cut from the same (or different) body or flaps of tissue still partly connected to the body but resewn for rearranging or restructuring of the area of the body in question. Although grafting is often used in cosmetic surgery, it is also used in other surgery. Grafts may be taken from one area of the person's body and inserted to another area of the body. An example is bypass surgery, where clogged blood vessels are bypassed with a graft from another part of the body. Alternatively, grafts may be from other persons, cadavers, or animals.
  • insertion of prosthetic parts when needed. Pins or screws to set and hold bones may be used. Sections of bone may be replaced with prosthetic rods or other parts. Sometimes a plate is inserted to replace a damaged area of skull. Artificial hip replacement has become more common. Heart pacemakers or valves may be inserted. Many other types of prostheses are used.
  • creation of a stoma, a permanent or semi-permanent opening in the body
  • in transplant surgery, the donor organ (taken out of the donor's body) is inserted into the recipient's body and reconnected to the recipient in all necessary ways (blood vessels, ducts, etc.).
  • arthrodesis – surgical connection of adjacent bones so the bones can grow together into one. Spinal fusion is an example of adjacent vertebrae connected allowing them to grow together into one piece.
  • modifying the digestive tract in bariatric surgery for weight loss.
  • repair of a fistula, hernia, or prolapse.
  • repair according to the ICD-10-PCS, in the Medical and Surgical Section 0, root operation Q, means restoring, to the extent possible, a body part to its normal anatomic structure and function. This definition, repair, is used only when the method used to accomplish the repair is not one of the other root operations. Examples would be colostomy takedown, herniorrhaphy of a hernia, and the surgical suture of a laceration.
  • other procedures, including:
  • clearing clogged ducts, blood or other vessels
  • removal of calculi (stones)
  • draining of accumulated fluids
  • debridement – removal of dead, damaged, or diseased tissue

Blood or blood expanders may be administered to compensate for blood lost during surgery. Once the procedure is complete, sutures or staples are used to close the incision. Once the incision is closed, the anesthetic agents are stopped or reversed, and the person is taken off ventilation and extubated (if general anesthesia was administered).

Postoperative care

After completion of surgery, the person is transferred to the post anesthesia care unit and closely monitored. When the person is judged to have recovered from the anesthesia, he/she is either transferred to a surgical ward elsewhere in the hospital or discharged home. During the post-operative period, the person's general function is assessed, the outcome of the procedure is assessed, and the surgical site is checked for signs of infection. There are several risk factors associated with postoperative complications, such as immune deficiency and obesity. Obesity has long been considered a risk factor for adverse post-surgical outcomes. It has been linked to many disorders such as obesity hypoventilation syndrome, atelectasis and pulmonary embolism, adverse cardiovascular effects, and wound healing complications. If removable skin closures are used, they are removed after 7 to 10 days post-operatively, or after healing of the incision is well under way.

It is not uncommon for surgical drains to be required to remove blood or fluid from the surgical wound during recovery. Mostly these drains stay in until the volume tapers off, then they are removed. These drains can become clogged, leading to abscess.

Postoperative therapy may include adjuvant treatment such as chemotherapy, radiation therapy, or administration of medication such as anti-rejection medication for transplants. Other follow-up studies or rehabilitation may be prescribed during and after the recovery period.

The use of topical antibiotics on surgical wounds to reduce infection rates has been questioned. Antibiotic ointments are likely to irritate the skin, slow healing, and could increase risk of developing contact dermatitis and antibiotic resistance. It has also been suggested that topical antibiotics should only be used when a person shows signs of infection and not as a preventative. A systematic review published by Cochrane (organisation) in 2016, though, concluded that topical antibiotics applied over certain types of surgical wounds reduce the risk of surgical site infections, when compared to no treatment or use of antiseptics. The review also did not find conclusive evidence to suggest that topical antibiotics increased the risk of local skin reactions or antibiotic resistance.

Through a retrospective analysis of national administrative data, the association between mortality and day of elective surgical procedure suggests a higher risk in procedures carried out later in the working week and on weekends. The odds of death were 44% and 82% higher respectively when comparing procedures on a Friday to a weekend procedure. This "weekday effect" has been postulated to be from several factors including poorer availability of services on a weekend, and also, decrease number and level of experience over a weekend.

While pain is universal and expected after surgery, there is growing evidence that pain may be inadequately treated in many people in the acute period immediately after surgery. It has been reported that incidence of inadequately controlled pain after surgery ranged from 25.1% to 78.4% across all surgical disciplines.

Postoperative recovery has been defined as an energy‐requiring process to decrease physical symptoms, reach a level of emotional well‐being, regain functions, and re‐establish activities. Moreover, it has been identified that patients who have undergone surgery are often not fully recovered on discharge.

Epidemiology

United States

In 2011, of the 38.6 million hospital stays in U.S. hospitals, 29% included at least one operating room procedure. These stays accounted for 48% of the total $387 billion in hospital costs.

The overall number of procedures remained stable from 2001 to 2011. In 2011, over 15 million operating room procedures were performed in U.S. hospitals.

Data from 2003 to 2011 showed that U.S. hospital costs were highest for the surgical service line; the surgical service line costs were $17,600 in 2003 and projected to be $22,500 in 2013. For hospital stays in 2012 in the United States, private insurance had the highest percentage of surgical expenditure. in 2012, mean hospital costs in the United States were highest for surgical stays.

Special populations

Elderly people

Older adults have widely varying physical health. Frail elderly people are at significant risk of post-surgical complications and the need for extended care. Assessment of older people before elective surgery can accurately predict the person's recovery trajectories. One frailty scale uses five items: unintentional weight loss, muscle weakness, exhaustion, low physical activity, and slowed walking speed. A healthy person scores 0; a very frail person scores 5. Compared to non-frail elderly people, people with intermediate frailty scores (2 or 3) are twice as likely to have post-surgical complications, spend 50% more time in the hospital, and are three times as likely to be discharged to a skilled nursing facility instead of to their own homes. People who are frail and elderly (score of 4 or 5) have even worse outcomes, with the risk of being discharged to a nursing home rising to twenty times the rate for non-frail elderly people.

Children

Surgery on children requires considerations that are not common in adult surgery. Children and adolescents are still developing physically and mentally making it difficult for them to make informed decisions and give consent for surgical treatments. Bariatric surgery in youth is among the controversial topics related to surgery in children.

Vulnerable populations

Doctors perform surgery with the consent of the person undergoing surgery. Some people are able to give better informed consent than others. Populations such as incarcerated persons, people living with dementia, the mentally incompetent, persons subject to coercion, and other people who are not able to make decisions with the same authority as others, have special needs when making decisions about their personal healthcare, including surgery.

'Global Surgery' in low- and middle-income countries

Surgery remains grossly neglected in global health, famously described by Halfdan T. Mahler as the 'neglected stepchild of global health'. This particularly affects low-resource settings with weak surgical health systems. 'Global surgery' is the term now adopted to describe the rapidly developing field seeking to address this, and has been defined as 'the multidisciplinary enterprise of providing improved and equitable surgical care to the world's population, with its core tenets as the issues of need, access and quality'.

In 2014, The Lancet Commission on Global Surgery was launched to examine the case for surgery as an integral component of global health care and to provide recommendations regarding the delivery of surgical and anesthesia services in low and middle income countries. In this study, two primary conclusions were reached:

  • Five billion people worldwide lack access to safe, timely, and affordable surgical and anesthesia care. Areas in which especially large proportions of the population lack access include Sub-Saharan Africa, the Indian Subcontinent, Central Asia and, to a lesser extent, Russia and China. Of the estimated 312.9 million surgical procedures undertaken worldwide in 2012, only 6.3% were done in countries comprising the poorest 37.3% of the world's population.
  • An additional 143 million surgical procedures are needed each year to prevent unnecessary death and disability.

Globally, 4.2 million people are estimated to die within 30 days of surgery each year, with half of these occurring in low- and middle-income countries. A prospective study of 10,745 adults undergoing emergency abdominal surgery from 357 centres across 58 countries found that mortality is three times higher in low- compared with high-human development index (HDI) countries even when adjusted for prognostic factors. In this study the overall global mortality rate was 1·6 per cent at 24 hours (high HDI 1·1 per cent, middle HDI 1·9 per cent, low HDI 3·4 per cent), increasing to 5·4 per cent by 30 days (high HDI 4·5 per cent, middle HDI 6·0 per cent, low HDI 8·6 per cent; P < 0·001). A sub-study of 1,409 children undergoing emergency abdominal surgery from 253 centres across 43 countries found that adjusted mortality in children following surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. This translates to 40 excess deaths per 1000 procedures performed in these settings. Patient safety factors were suggested to play an important role, with use of the WHO Surgical Safety Checklist associated with reduced mortality at 30 days.

Introducing novel or new surgical techniques in low- and middle-income countries is a challenge. Challenges include knowledge (awareness), fear, costs, and cultural beliefs.

Human rights

Access to surgical care is increasingly recognized as an integral aspect of healthcare, and therefore is evolving into a normative derivation of human right to health. The ICESCR Article 12.1 and 12.2 define the human right to health as "the right of everyone to the enjoyment of the highest attainable standard of physical and mental health" In the August 2000, the UN Committee on Economic, Social and Cultural Rights (CESCR) interpreted this to mean "right to the enjoyment of a variety of facilities, goods, services, and conditions necessary for the realization of the highest attainable health". Surgical care can be thereby viewed as a positive right – an entitlement to protective healthcare.

Woven through the International Human and Health Rights literature is the right to be free from surgical disease. The 1966 ICESCR Article 12.2a described the need for "provision for the reduction of the stillbirth-rate and of infant mortality and for the healthy development of the child" which was subsequently interpreted to mean "requiring measures to improve… emergency obstetric services". Article 12.2d of the ICESCR stipulates the need for "the creation of conditions which would assure to all medical service and medical attention in the event of sickness", and is interpreted in the 2000 comment to include timely access to "basic preventative, curative services… for appropriate treatment of injury and disability.". Obstetric care shares close ties with reproductive rights, which includes access to reproductive health.

Surgeons and public health advocates, such as Kelly McQueen, have described surgery as "Integral to the right to health". This is reflected in the establishment of the WHO Global Initiative for Emergency and Essential Surgical Care in 2005, the 2013 formation of the Lancet Commission for Global Surgery, the 2015 World Bank Publication of Volume 1 of its Disease Control Priorities "Essential Surgery", and the 2015 World Health Assembly 68.15 passing of the Resolution for Strengthening Emergency and Essential Surgical Care and Anesthesia as a Component of Universal Health Coverage. The Lancet Commission for Global Surgery outlined the need for access to "available, affordable, timely and safe" surgical and anesthesia care; dimensions paralleled in ICESCR General Comment No. 14, which similarly outlines need for available, accessible, affordable and timely healthcare.

History

Plates vi & vii of the Edwin Smith Papyrus, an Egyptian surgical treatise

Trepanation

Surgical treatments date back to the prehistoric era. The oldest for which there is evidence is trepanation, in which a hole is drilled or scraped into the skull, thus exposing the dura mater in order to treat health problems related to intracranial pressure and other diseases.

Ancient Egypt

Prehistoric surgical techniques are seen in Ancient Egypt, where a mandible dated to approximately 2650 BC shows two perforations just below the root of the first molar, indicating the draining of an abscessed tooth. Surgical texts from ancient Egypt date back about 3500 years ago. Surgical operations were performed by priests, specialized in medical treatments similar to today, and used sutures to close wounds. Infections were treated with honey.

India

Sushruta, the author of Sushruta Samhita, one of the oldest texts on surgery

Remains from the early Harappan periods of the Indus Valley Civilization (c. 3300 BC) show evidence of teeth having been drilled dating back 9,000 years. Susruta was an ancient Indian surgeon commonly credited as the author of the treatise Sushruta Samhita. He is well known as the "father of surgery", and his period is usually placed around 1200–600 BC. One of the earliest known mentions of the name is from the Bower Manuscript, in which Sushruta is listed as one of the ten sages residing in the Himalayas. Texts suggest that he learned surgery at Kasi from Lord Dhanvantari, the god of medicine in Hindu mythology. It is one of the oldest known surgical texts and it describes in detail the examination, diagnosis, treatment, and prognosis of numerous ailments, as well as procedures for various forms of cosmetic surgery, plastic surgery and rhinoplasty.

Ancient Greece

Hippocrates stated in the oath (c. 400 BC) that general physicians must never practice surgery and that surgical procedures are to be conducted by specialists

In ancient Greece, temples dedicated to the healer-god Asclepius, known as Asclepieia (Greek: Ασκληπιεία, sing. Asclepieion Ασκληπιείον), functioned as centers of medical advice, prognosis, and healing. In the Asclepieion of Epidaurus, some of the surgical cures listed, such as the opening of an abdominal abscess or the removal of traumatic foreign material, are realistic enough to have taken place. The Greek Galen was one of the greatest surgeons of the ancient world and performed many audacious operations – including brain and eye surgery – that were not tried again for almost two millennia.

Researchers from the Adelphi University discovered in the Paliokastro on Thasos ten skeletal remains, four women and six men, who were buried between the fourth and seventh centuries A.D. Their bones illuminated their physical activities, traumas, and even a complex form of brain surgery. According to the researchers: "The very serious trauma cases sustained by both males and females had been treated surgically or orthopedically by a very experienced physician/surgeon with great training in trauma care. We believe it to have been a military physician". The researchers were impressed by the complexity of the brain surgical operation.

Islamic World

During the Islamic Golden Age, largely based upon Paul of Aegina's Pragmateia, the writings of Abulcasis (Abu al-Qasim Khalaf ibn al-Abbas Al-Zahrawi), an Andalusian-Arab physician and scientist who practiced in the Zahra suburb of Córdoba, were influential. Al-Zahrawi specialized in curing disease by cauterization. He invented several surgical instruments for purposes such as inspection of the interior of the urethra and for removing foreign bodies from the throat, the ear, and other body organs. He was also the first to illustrate the various cannulae and to treat warts with an iron tube and caustic metal as a boring instrument. He describes what is thought to be the first attempt at reduction mammaplasty for the management of gynaecomastia and the first mastectomy to treat breast cancer. He is credited with the performance of the first thyroidectomy. Al-Zahrawi pioneered techniques of neurosurgery and neurological diagnosis, treating head injuries, skull fractures, spinal injuries, hydrocephalus, subdural effusions and headache. The first clinical description of an operative procedure for hydrocephalus was given by Al-Zahrawi, who clearly describes the evacuation of superficial intracranial fluid in hydrocephalic children.

Early modern Europe

Ambroise Paré (c. 1510–1590), father of modern military surgery.
 
12th century medieval eye surgery in Italy

In Europe, the demand grew for surgeons to formally study for many years before practicing; universities such as Montpellier, Padua and Bologna were particularly renowned. In the 12th century, Rogerius Salernitanus composed his Chirurgia, laying the foundation for modern Western surgical manuals. Barber-surgeons generally had a bad reputation that was not to improve until the development of academic surgery as a specialty of medicine, rather than an accessory field. Basic surgical principles for asepsis etc., are known as Halsteads principles.

There were some important advances to the art of surgery during this period. The professor of anatomy at the University of Padua, Andreas Vesalius, was a pivotal figure in the Renaissance transition from classical medicine and anatomy based on the works of Galen, to an empirical approach of 'hands-on' dissection. In his anatomic treaties De humani corporis fabrica, he exposed the many anatomical errors in Galen and advocated that all surgeons should train by engaging in practical dissections themselves.

The second figure of importance in this era was Ambroise Paré (sometimes spelled "Ambrose"), a French army surgeon from the 1530s until his death in 1590. The practice for cauterizing gunshot wounds on the battlefield had been to use boiling oil; an extremely dangerous and painful procedure. Paré began to employ a less irritating emollient, made of egg yolk, rose oil and turpentine. He also described more efficient techniques for the effective ligation of the blood vessels during an amputation.

Modern surgery

The discipline of surgery was put on a sound, scientific footing during the Age of Enlightenment in Europe. An important figure in this regard was the Scottish surgical scientist, John Hunter, generally regarded as the father of modern scientific surgery. He brought an empirical and experimental approach to the science and was renowned around Europe for the quality of his research and his written works. Hunter reconstructed surgical knowledge from scratch; refusing to rely on the testimonies of others, he conducted his own surgical experiments to determine the truth of the matter. To aid comparative analysis, he built up a collection of over 13,000 specimens of separate organ systems, from the simplest plants and animals to humans.

He greatly advanced knowledge of venereal disease and introduced many new techniques of surgery, including new methods for repairing damage to the Achilles tendon and a more effective method for applying ligature of the arteries in case of an aneurysm. He was also one of the first to understand the importance of pathology, the danger of the spread of infection and how the problem of inflammation of the wound, bone lesions and even tuberculosis often undid any benefit that was gained from the intervention. He consequently adopted the position that all surgical procedures should be used only as a last resort.

Other important 18th- and early 19th-century surgeons included Percival Pott (1713–1788) who described tuberculosis on the spine and first demonstrated that a cancer may be caused by an environmental carcinogen (he noticed a connection between chimney sweep's exposure to soot and their high incidence of scrotal cancer). Astley Paston Cooper (1768–1841) first performed a successful ligation of the abdominal aorta, and James Syme (1799–1870) pioneered the Symes Amputation for the ankle joint and successfully carried out the first hip disarticulation.

Modern pain control through anesthesia was discovered in the mid-19th century. Before the advent of anesthesia, surgery was a traumatically painful procedure and surgeons were encouraged to be as swift as possible to minimize patient suffering. This also meant that operations were largely restricted to amputations and external growth removals. Beginning in the 1840s, surgery began to change dramatically in character with the discovery of effective and practical anaesthetic chemicals such as ether, first used by the American surgeon Crawford Long, and chloroform, discovered by Scottish obstetrician James Young Simpson and later pioneered by John Snow, physician to Queen Victoria. In addition to relieving patient suffering, anaesthesia allowed more intricate operations in the internal regions of the human body. In addition, the discovery of muscle relaxants such as curare allowed for safer applications.

Infection and antisepsis

Unfortunately, the introduction of anesthetics encouraged more surgery, which inadvertently caused more dangerous patient post-operative infections. The concept of infection was unknown until relatively modern times. The first progress in combating infection was made in 1847 by the Hungarian doctor Ignaz Semmelweis who noticed that medical students fresh from the dissecting room were causing excess maternal death compared to midwives. Semmelweis, despite ridicule and opposition, introduced compulsory handwashing for everyone entering the maternal wards and was rewarded with a plunge in maternal and fetal deaths; however, the Royal Society dismissed his advice.

Until the pioneering work of British surgeon Joseph Lister in the 1860s, most medical men believed that chemical damage from exposures to bad air (see "miasma") was responsible for infections in wounds, and facilities for washing hands or a patient's wounds were not available. Lister became aware of the work of French chemist Louis Pasteur, who showed that rotting and fermentation could occur under anaerobic conditions if micro-organisms were present. Pasteur suggested three methods to eliminate the micro-organisms responsible for gangrene: filtration, exposure to heat, or exposure to chemical solutions. Lister confirmed Pasteur's conclusions with his own experiments and decided to use his findings to develop antiseptic techniques for wounds. As the first two methods suggested by Pasteur were inappropriate for the treatment of human tissue, Lister experimented with the third, spraying carbolic acid on his instruments. He found that this remarkably reduced the incidence of gangrene and he published his results in The Lancet. Later, on 9 August 1867, he read a paper before the British Medical Association in Dublin, on the Antiseptic Principle of the Practice of Surgery, which was reprinted in the British Medical Journal. His work was groundbreaking and laid the foundations for a rapid advance in infection control that saw modern antiseptic operating theatres widely used within 50 years.

Lister continued to develop improved methods of antisepsis and asepsis when he realised that infection could be better avoided by preventing bacteria from getting into wounds in the first place. This led to the rise of sterile surgery. Lister introduced the Steam Steriliser to sterilize equipment, instituted rigorous hand washing and later implemented the wearing of rubber gloves. These three crucial advances – the adoption of a scientific methodology toward surgical operations, the use of anaesthetic and the introduction of sterilised equipment – laid the groundwork for the modern invasive surgical techniques of today.

The use of X-rays as an important medical diagnostic tool began with their discovery in 1895 by German physicist Wilhelm Röntgen. He noticed that these rays could penetrate the skin, allowing the skeletal structure to be captured on a specially treated photographic plate.

 

General anaesthesia

From Wikipedia, the free encyclopedia
 
General anaesthesia
Ana arbeitsplatz.JPG
Equipment used for anaesthesia in the operating theatre
MeSHD000768
MedlinePlus007410

General anaesthesia or general anesthesia (see spelling differences) is a medically induced coma with loss of protective reflexes, resulting from the administration of one or more general anaesthetic agents. It is carried out to allow medical procedures that would otherwise be intolerably painful for the patient; or where the nature of the procedure itself precludes the patient being awake.

A variety of drugs may be administered, with the overall aim of ensuring unconsciousness, amnesia, analgesia, loss of reflexes of the autonomic nervous system, and in some cases paralysis of skeletal muscles. The optimal combination of drugs for any given patient and procedure is typically selected by an anaesthetist, or another provider such as an operating department practitioner, anaesthetist practitioner, physician assistant or nurse anaesthetist (depending on local practice), in consultation with the patient and the surgeon, dentist, or other practitioner performing the operative procedure.

History

Attempts at producing a state of general anaesthesia can be traced throughout recorded history in the writings of the ancient Sumerians, Babylonians, Assyrians, Egyptians, Greeks, Romans, Indians, and Chinese. During the Middle Ages, scientists and other scholars made significant advances in the Eastern world, while their European counterparts also made important advances.

The Renaissance saw significant advances in anatomy and surgical technique. However, despite all this progress, surgery remained a treatment of last resort. Largely because of the associated pain, many patients chose certain death rather than undergo surgery. Although there has been a great deal of debate as to who deserves the most credit for the discovery of general anaesthesia, several scientific discoveries in the late 18th and early 19th centuries were critical to the eventual introduction and development of modern anaesthetic techniques.

Two enormous leaps occurred in the late 19th century, which together allowed the transition to modern surgery. An appreciation of the germ theory of disease led rapidly to the development and application of antiseptic techniques in surgery. Antisepsis, which soon gave way to asepsis, reduced the overall morbidity and mortality of surgery to a far more acceptable rate than in previous eras. Concurrent with these developments were the significant advances in pharmacology and physiology which led to the development of general anaesthesia and the control of pain. On 14 November 1804, Hanaoka Seishū, a Japanese doctor, became the first person to successfully perform surgery using general anaesthesia.

In the 20th century, the safety and efficacy of general anaesthesia was improved by the routine use of tracheal intubation and other advanced airway management techniques. Significant advances in monitoring and new anaesthetic agents with improved pharmacokinetic and pharmacodynamic characteristics also contributed to this trend. Finally, standardized training programs for anaesthesiologists and nurse anaesthetists emerged during this period.

Purpose

General anaesthesia has many purposes, including:

  1. Unconsciousness (loss of awareness)
  2. Analgesia (loss of response to pain)
  3. Amnesia (loss of memory)
  4. Immobility (loss of motor reflexes)
  5. Paralysis (skeletal muscle relaxation and normal muscle relaxation)

General anaesthesia should not be used as prophylaxis in patients with a history of contrast medium-induced anaphylaxis.

Biochemical mechanism of action

The biochemical mechanism of action of general anaesthetics is not well understood. Theories need to explain the function of anaesthesia in animals and plants. To induce unconsciousness, anaesthetics have myriad sites of action and affect the central nervous system (CNS) at multiple levels. Common areas of the central nervous system whose functions are interrupted or changed during general anaesthesia include the cerebral cortex, thalamus, reticular activating system, and spinal cord. Current theories on the anaesthetized state identify not only target sites in the CNS but also neural networks and loops whose interruption is linked with unconsciousness. Potential pharmacologic targets of general anaesthetics are GABA, glutamate receptors, voltage-gated ion channels, and glycine and serotonin receptors.

Halothane has been found to be a GABA agonist, and ketamine is an NMDA receptor antagonist.

Preanaesthetic evaluation

Prior to a planned procedure, the anesthesiologist reviews medical records and/or interviews the patient to determine the best combination of drugs and dosages and the degree to which monitoring will be required to ensure a safe and effective procedure. Key factors in this evaluation are the patient's age, body mass index, medical and surgical history, current medications, and fasting time. Thorough and accurate answering of the questions is important so that the anaesthetist can select the proper drugs and procedures. For example, a patient who consumes significant quantities of alcohol or illicit drugs could be undermedicated if they fail to disclose this fact, and this could lead to anaesthesia awareness or intraoperative hypertension. Commonly used medications can interact with anaesthetics, and failure to disclose such usage can increase the risk to the patient.

An important aspect of pre-anaesthetic evaluation is an assessment of the patient's airway, involving inspection of the mouth opening and visualisation of the soft tissues of the pharynx. The condition of teeth and location of dental crowns are checked, and neck flexibility and head extension are observed.

Premedication

Prior to administration of a general anaesthetic, the anaesthetist may administer one or more drugs that complement or improve the quality or safety of the anaesthetic.

One commonly used premedication is clonidine, an alpha-2 adrenergic agonist. Clonidine premedication reduces the need for anaesthetic induction agents, for volatile agents to maintain general anaesthesia, and for postoperative analgesics. It also reduces postoperative shivering, postoperative nausea and vomiting, and emergence delirium. In children, clonidine premedication is at least as effective as benzodiazepines and has less serious side effects. However, oral clonidine can take up to 45 minutes to take full effect, and drawbacks include hypotension and bradycardia.

Midazolam, a benzodiazepine characterized by a rapid onset and short duration, is effective in reducing preoperative anxiety, including separation anxiety in children. Dexmedetomidine and certain atypical antipsychotic agents may be used in uncooperative children.

Melatonin has been found to be effective as an anaesthetic premedication in both adults and children because of its hypnotic, anxiolytic, sedative, antinociceptive, and anticonvulsant properties. Unlike midazolam, melatonin does not impair psychomotor skills or hinder recovery. Recovery is more rapid after premedication with melatonin than with midazolam, and there is also a reduced incidence of post-operative agitation and delirium. Melatonin premedication also reduces the required induction dose of propofol and sodium thiopental.

Another example of anaesthetic premedication is the preoperative administration of beta adrenergic antagonists to reduce the incidence of postoperative hypertension, cardiac dysrhythmia, or myocardial infarction. Anaesthesiologists may administer an antiemetic agent such as ondansetron, droperidol, or dexamethasone to prevent postoperative nausea and vomiting, or subcutaneous heparin or enoxaparin to reduce the incidence of deep vein thrombosis. Other commonly used premedication agents include opioids such as fentanyl or sufentanil, gastrokinetic agents such as metoclopramide, and histamine antagonists such as famotidine.

Non-pharmacologic preanaesthetic interventions include playing relaxing music, massage, and reducing ambient light and noise levels in order to maintain the sleep-wake cycle. These techniques are particularly useful for children and patients with intellectual disabilities. Minimizing sensory stimulation or distraction by video games may help to reduce anxiety prior to or during induction of general anaesthesia. Larger high-quality studies are needed to confirm the most effective non-pharmacological approaches for reducing this type of anxiety. Parental presence during premedication and induction of anaesthesia has not been shown to reduce anxiety in children. It is suggested that parents who wish to attend should not be actively discouraged, and parents who prefer not to be present should not be actively encouraged to attend.

Stages of anaesthesia

Guedel's classification, introduced by Arthur Ernest Guedel in 1937, describes four stages of anaesthesia. Despite newer anaesthetic agents and delivery techniques, which have led to more rapid onset of—and recovery from—anaesthesia (in some cases bypassing some of the stages entirely), the principles remain.

Stage 1
Stage 1, also known as induction, is the period between the administration of induction agents and loss of consciousness. During this stage, the patient progresses from analgesia without amnesia to analgesia with amnesia. Patients can carry on a conversation at this time.
Stage 2
Stage 2, also known as the excitement stage, is the period following loss of consciousness and marked by excited and delirious activity. During this stage, the patient's respiration and heart rate may become irregular. In addition, there may be uncontrolled movements, vomiting, suspension of breathing, and pupillary dilation. Because the combination of spastic movements, vomiting, and irregular respiration may compromise the patient's airway, rapidly acting drugs are used to minimize time in this stage and reach Stage 3 as fast as possible.

Stage 3
In Stage 3, also known as surgical anaesthesia, the skeletal muscles relax, vomiting stops, respiratory depression occurs, and eye movements slow and then stop. The patient is unconscious and ready for surgery. This stage is divided into four planes:
  1. The eyes roll, then become fixed;
  2. Corneal and laryngeal reflexes are lost;
  3. The pupils dilate and light reflex is lost;
  4. Intercostal paralysis and shallow abdominal respiration occur.
Stage 4
Stage 4, also known as overdose, occurs when too much anaesthetic medication is given relative to the amount of surgical stimulation and the patient has severe brainstem or medullary depression, resulting in a cessation of respiration and potential cardiovascular collapse. This stage is lethal without cardiovascular and respiratory support.

Induction

General anaesthesia is usually induced in a medical facility, most commonly in an operating theatre or in a dedicated anaesthetic room adjacent to the theatre. However, it may also be conducted in other locations, such as an endoscopy suite, radiology or cardiology department, emergency department, or ambulance, or at the site of a disaster where extrication of the patient may be impossible or impractical.

Anaesthetic agents may be administered by various routes, including inhalation, injection (intravenous, intramuscular, or subcutaneous), oral, and rectal. Once they enter the circulatory system, the agents are transported to their biochemical sites of action in the central and autonomic nervous systems.

Most general anaesthetics are induced either intravenously or by inhalation. Intravenous injection works faster than inhalation, taking about 10–20 seconds to induce total unconsciousness. This minimizes the excitatory phase (Stage 2) and thus reduces complications related to the induction of anaesthesia. Commonly used intravenous induction agents include propofol, sodium thiopental, etomidate, methohexital, and ketamine. Inhalational anaesthesia may be chosen when intravenous access is difficult to obtain (e.g., children), when difficulty maintaining the airway is anticipated, or when the patient prefers it. Sevoflurane is the most commonly used agent for inhalational induction, because it is less irritating to the tracheobronchial tree than other agents.

As an example sequence of induction drugs:

  1. Pre-oxygenation to fill lungs with oxygen to permit a longer period of apnea during intubation without affecting blood oxygen levels
  2. Fentanyl for systemic analgesia for intubation
  3. Propofol for sedation for intubation
  4. Switching from oxygen to a mixture of oxygen and inhalational anesthetic

Laryngoscopy and intubation are both very stimulating and induction blunts the response to these maneuvers while simultaneously inducing a near-coma state to prevent awareness.

Physiologic monitoring

Several monitoring technologies allow for a controlled induction of, maintenance of, and emergence from general anaesthesia.

  1. Continuous electrocardiography (ECG or EKG): Electrodes are placed on the patient's skin to monitor heart rate and rhythm. This may also help the anaesthesiologist to identify early signs of heart ischaemia. Typically lead II and V5 are monitored for arrhythmias and ischemia, respectively.
  2. Continuous pulse oximetry (SpO2): A device is placed, usually on a finger, to allow for early detection of a fall in a patient's haemoglobin saturation with oxygen (hypoxaemia).
  3. Blood pressure monitoring: There are two methods of measuring the patient's blood pressure. The first, and most common, is non-invasive blood pressure (NIBP) monitoring. This involves placing a blood pressure cuff around the patient's arm, forearm, or leg. A machine takes blood pressure readings at regular, preset intervals throughout the surgery. The second method is invasive blood pressure (IBP) monitoring. This method is reserved for patients with significant heart or lung disease, the critically ill, and those undergoing major procedures such as cardiac or transplant surgery, or when large blood loss is expected. It involves placing a special type of plastic cannula in an artery, usually in the wrist (radial artery) or groin (femoral artery).
  4. Agent concentration measurement: anaesthetic machines typically have monitors to measure the percentage of inhalational anaesthetic agents used as well as exhalation concentrations. These monitors include measuring oxygen, carbon dioxide, and inhalational anaesthetics (e.g., nitrous oxide, isoflurane).
  5. Oxygen measurement: Almost all circuits have an alarm in case oxygen delivery to the patient is compromised. The alarm goes off if the fraction of inspired oxygen drops below a set threshold.
  6. A circuit disconnect alarm or low pressure alarm indicates failure of the circuit to achieve a given pressure during mechanical ventilation.
  7. Capnography measures the amount of carbon dioxide exhaled by the patient in percent or mmHg, allowing the anaesthesiologist to assess the adequacy of ventilation. MmHg is usually used to allow the provider to see more subtle changes.
  8. Temperature measurement to discern hypothermia or fever, and to allow early detection of malignant hyperthermia.
  9. Electroencephalography, entropy monitoring, or other systems may be used to verify the depth of anaesthesia. This reduces the likelihood of anaesthesia awareness and of overdose.

Airway management

Anaesthetized patients lose protective airway reflexes (such as coughing), airway patency, and sometimes a regular breathing pattern due to the effects of anaesthetics, opioids, or muscle relaxants. To maintain an open airway and regulate breathing, some form of breathing tube is inserted after the patient is unconscious. To enable mechanical ventilation, an endotracheal tube is often used, although there are alternative devices that can assist respiration, such as face masks or laryngeal mask airways. Generally, full mechanical ventilation is only used if a very deep state of general anaesthesia is to be induced for a major procedure, and/or with a profoundly ill or injured patient. That said, induction of general anaesthesia usually results in apnea and requires ventilation until the drugs wear off and spontaneous breathing starts. In other words, ventilation may be required for both induction and maintenance of general anaesthesia or just during the induction. However, mechanical ventilation can provide ventilatory support during spontaneous breathing to ensure adequate gas exchange.

General anaesthesia can also be induced with the patient spontaneously breathing and therefore maintaining their own oxygenation which can be beneficial in certain scenarios (e.g. difficult airway or tubeless surgery). Spontaneous ventilation has been traditionally maintained with inhalational agents (i.e. halothane or sevoflurane) which is called a gas or inhalational induction. Spontaneous ventilation can also be maintained using intravenous anaesthesia (e.g. propofol). Intravenous anaesthesia to maintain spontaneous respiration has certain advantages over inhalational agents (i.e. suppressed laryngeal reflexes) however it requires careful titration. Spontaneous Respiration using Intravenous anaesthesia and High-flow nasal oxygen (STRIVE Hi) is a technique that has been used in difficult and obstructed airways.

Eye management

General anaesthesia reduces the tonic contraction of the orbicularis oculi muscle, causing lagophthalmos, or incomplete eye closure, in 59% of patients. In addition, tear production and tear-film stability are reduced, resulting in corneal epithelial drying and reduced lysosomal protection. The protection afforded by Bell's phenomenon (in which the eyeball turns upward during sleep, protecting the cornea) is also lost. Careful management is required to reduce the likelihood of eye injuries during general anaesthesia.

Neuromuscular blockade

Syringes prepared with medications that are expected to be used during an operation under general anaesthesia maintained by sevoflurane gas:
- Propofol, a hypnotic
- Ephedrine, in case of hypotension
- Fentanyl, for analgesia
- Atracurium, for neuromuscular block
- Glycopyrronium bromide (here under trade name Robinul), reducing secretions

Paralysis, or temporary muscle relaxation with a neuromuscular blocker, is an integral part of modern anaesthesia. The first drug used for this purpose was curare, introduced in the 1940s, which has now been superseded by drugs with fewer side effects and, generally, shorter duration of action. Muscle relaxation allows surgery within major body cavities, such as the abdomen and thorax, without the need for very deep anaesthesia, and also facilitates endotracheal intubation.

Acetylcholine, the natural neurotransmitter at the neuromuscular junction, causes muscles to contract when it is released from nerve endings. Muscle relaxants work by preventing acetylcholine from attaching to its receptor. Paralysis of the muscles of respiration—the diaphragm and intercostal muscles of the chest—requires that some form of artificial respiration be implemented. Because the muscles of the larynx are also paralysed, the airway usually needs to be protected by means of an endotracheal tube.

Paralysis is most easily monitored by means of a peripheral nerve stimulator. This device intermittently sends short electrical pulses through the skin over a peripheral nerve while the contraction of a muscle supplied by that nerve is observed. The effects of muscle relaxants are commonly reversed at the end of surgery by anticholinesterase drugs, which are administered in combination with muscarinic anticholinergic drugs to minimize side effects. Novel neuromuscular blockade reversal agents such as sugammadex may also be used. Examples of skeletal muscle relaxants in use today are pancuronium, rocuronium, vecuronium, cisatracurium, atracurium, mivacurium, and succinylcholine.

Maintenance

The duration of action of intravenous induction agents is generally 5 to 10 minutes, after which spontaneous recovery of consciousness will occur. In order to prolong unconsciousness for the required duration (usually the duration of surgery), anaesthesia must be maintained. This is achieved by allowing the patient to breathe a carefully controlled mixture of oxygen, sometimes nitrous oxide, and a volatile anaesthetic agent, or by administering medication (usually propofol) through an intravenous catheter. Inhaled agents are frequently supplemented by intravenous anaesthetics, such as opioids (usually fentanyl or a fentanyl derivative) and sedatives (usually propofol or midazolam). With propofol-based anaesthetics, however, supplementation by inhalation agents is not required. General anesthesia is usually considered safe; however, there are reported cases of patients with distortion of taste and/or smell due to local anesthetics, stroke, nerve damage, or as a side effect of general anesthesia.

At the end of surgery, administration of anaesthetic agents is discontinued. Recovery of consciousness occurs when the concentration of anaesthetic in the brain drops below a certain level (usually within 1 to 30 minutes, depending on the duration of surgery).

In the 1990s, a novel method of maintaining anaesthesia was developed in Glasgow, Scotland. Called target controlled infusion (TCI), it involves using a computer-controlled syringe driver (pump) to infuse propofol throughout the duration of surgery, removing the need for a volatile anaesthetic and allowing pharmacologic principles to more precisely guide the amount of the drug used by setting the desired drug concentration. Advantages include faster recovery from anaesthesia, reduced incidence of postoperative nausea and vomiting, and absence of a trigger for malignant hyperthermia. At present, TCI is not permitted in the United States, but a syringe pump delivering a specific rate of medication is commonly used instead.

Other medications are occasionally used to treat side effects or prevent complications. They include antihypertensives to treat high blood pressure; ephedrine or phenylephrine to treat low blood pressure; salbutamol to treat asthma, laryngospasm, or bronchospasm; and epinephrine or diphenhydramine to treat allergic reactions. Glucocorticoids or antibiotics are sometimes given to prevent inflammation and infection, respectively.

Emergence

Emergence is the return to baseline physiologic function of all organ systems after the cessation of general anaesthetics. This stage may be accompanied by temporary neurologic phenomena, such as agitated emergence (acute mental confusion), aphasia (impaired production or comprehension of speech), or focal impairment in sensory or motor function. Shivering is also fairly common and can be clinically significant because it causes an increase in oxygen consumption, carbon dioxide production, cardiac output, heart rate, and systemic blood pressure. The proposed mechanism is based on the observation that the spinal cord recovers at a faster rate than the brain. This results in uninhibited spinal reflexes manifested as clonic activity (shivering). This theory is supported by the fact that doxapram, a CNS stimulant, is somewhat effective in abolishing postoperative shivering. Cardiovascular events such as increased or decreased blood pressure, rapid heart rate, or other cardiac dysrhythmias are also common during emergence from general anaesthesia, as are respiratory symptoms such as dyspnoea.

Postoperative care

Anaesthetized patient in postoperative recovery.

Hospitals strive for pain-free awakening from anaesthesia. Although not a direct result of general anaesthesia, postoperative pain is managed in the anaesthesia recovery unit with regional analgesia or oral, transdermal, or parenteral medication. Patients may be given opioids, as well as other medications like non steroidal anti-inflammatory drugs and acetaminophen. Sometimes, opioid medication is administered by the patient themselves using a system called a patient controlled analgesic. The patient presses a button to activate a syringe device and receive a preset dose or "bolus" of the drug, usually a strong opioid such as morphine, fentanyl, or oxycodone (e.g., one milligram of morphine). The PCA device then "locks out" for a preset period to allow the drug to take effect. If the patient becomes too sleepy or sedated, he or she makes no more requests. This confers a fail-safe aspect that is lacking in continuous-infusion techniques. If these medications cannot effectively manage the pain, local anesthetic may be directly injected to the nerve in a procedure called a nerve block.

In the recovery unit, many vital signs are monitored, including oxygen saturation, heart rhythm and respiration, blood pressure, and core body temperature.

Postanesthetic shivering is common. Apart from causing discomfort and exacerbating pain, shivering has been shown to increase oxygen consumption, catecholamine release, cardiac output, heart rate, blood pressure, and intraocular pressure. A number of techniques are used to reduce shivering, such as warm blankets, or wrapping the patient in a sheet that circulates warmed air, called a bair hugger. If the shivering cannot be managed with external warming devices, drugs such as dexmedetomidine, or other α2-agonists, anticholinergics, central nervous system stimulants, or corticosteroids may be used.

In many cases, opioids used in general anaesthesia can cause postoperative ileus, even after non-abdominal surgery. Administration of a μ-opioid antagonist such as alvimopan immediately after surgery can help reduce the severity and duration of ileus.

The major complication of general anaesthesia is malignant hyperthermia. Hospitals have procedures in place and emergency drugs to manage this dangerous complication.

Perioperative mortality

Most perioperative mortality is attributable to complications from the operation, such as haemorrhage, sepsis, and failure of vital organs. Current estimates of perioperative mortality in procedures involving general anaesthesia range from one in 53 to one in 5,417. However, a 1997 Canadian retrospective review of 2,830,000 oral surgical procedures in Ontario between 1973 and 1995 reported only four deaths in cases in which an oral and maxillofacial surgeon or a dentist with specialized training in anaesthesia administered the general anaesthetic or deep sedation. The authors calculated an overall mortality rate of 1.4 per 1,000,000.

Mortality directly related to anaesthetic management is very uncommon but may be caused by pulmonary aspiration of gastric contents, asphyxiation, or anaphylaxis. These in turn may result from malfunction of anaesthesia-related equipment or, more commonly, human error. A 1978 study found that 82% of preventable anaesthesia mishaps were the result of human error. In a 1954 review of 599,548 surgical procedures at 10 hospitals in the United States between 1948 and 1952, 384 deaths were attributed to anaesthesia, for an overall mortality rate of 0.064%. In 1984, after a television programme highlighting anaesthesia mishaps aired in the United States, American anaesthesiologist Ellison C. Pierce appointed the Anesthesia Patient Safety and Risk Management Committee within the American Society of Anesthesiologists. This committee was tasked with determining and reducing the causes of anaesthesia-related morbidity and mortality. An outgrowth of this committee, the Anesthesia Patient Safety Foundation, was created in 1985 as an independent, nonprofit corporation with the goal "that no patient shall be harmed by anesthesia".

As with perioperative mortality rates in general, mortality attributable to the management of general anaesthesia is controversial. Estimates of the incidence of perioperative mortality directly attributable to anaesthesia range from one in 6,795 to one in 200,200.

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