Preoperative fasting

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Preoperative fasting is the practice of a surgical patient abstaining from eating or drinking ("nothing by mouth") for some time before having an operation. This is intended to prevent stomach contents from getting into the windpipe and lungs (known as a pulmonary aspiration) while the patient is under general anesthesia. [1] The latest guidelines do not support preoperative fasting, as there is no difference in residual gastric fluid volume, pH or gastric emptying rate following semi-solid meals or drinks, whether in obese or lean individuals. [2] [ failed verification see discussion ]

Contents

Pulmonary aspiration

The main hypothesized benefit of preoperative fasting is to prevent pulmonary aspiration of stomach contents while under the effects of general anesthesia. Aspiration of as little as 30–40 mL can be a significant cause of suffering and death during an operation and therefore fasting is performed to reduce the volume of stomach contents as much as possible. Several factors can predispose to aspiration of stomach contents including inadequate anesthesia, pregnancy, obesity, difficult airways, emergency surgery (since fasting time is reduced), full stomach and altered gastrointestinal mobility. Increased fasting times leads to decreased injury if aspiration occurs. [1]

The latest guidelines do not support preoperative fasting, as there is no difference in residual gastric fluid volume, pH or gastric emptying rate following semi-solid meals or drinks, whether in obese or lean individuals. [2] [3] [ failed verification see discussion ]

Gastric conditions

In addition to fasting, antacids are administered the night before (or in the morning of an afternoon operation) and then once again two hours prior to surgery. This is to increase the pH (make more neutral) of the acid present in the stomach, helping to reduce the damage caused by pulmonary aspiration, should it occur. H2 receptor blockers should be used in high-risk situations and should be administered in the same timing intervals as antacids. [1]

Gastroparesis (delayed gastric emptying) may occur and is due to metabolic causes (e.g. poorly controlled diabetes mellitus), decreased gastric motility (e.g. due to head injury) or pyloric obstruction (e.g. pyloric stenosis). Delayed gastric emptying usually only affects the emptying of the stomach of high-cellulose foods such as vegetables. Gastric emptying of clear fluids such as water or black coffee is only affected in highly progressed delayed gastric emptying. [1]

Usually, gastroesophageal reflux (GERD) may be associated with delayed gastric emptying of solids, but clear liquids are not affected. Raised intra-abdominal pressure (e.g. in pregnancy or obesity) predisposes to regurgitation. Certain drugs such as opiates can cause marked delays in gastric emptying, as can trauma, which can be determined by certain indicators such as normal bowel sounds and patient hunger. [1]

Minimum fasting times

The minimum fasting times prior to surgery have long been debated. The first proposition came from British anesthetists stating that patients should have nothing by mouth from midnight. [4] However, since then, the American Society of Anesthesiologists (ASA), followed by the Association of Anaesthestists of Great Britain and Ireland (AAGBI), recommended new fasting guidelines for the minimum fast prior to surgery. [1] This was based upon evidence by Canadian anesthesiologists who found that drinking clear fluids two hours prior to surgery decreased pulmonary aspiration compared to those nil by mouth since midnight. [4] The following are the recommended guidelines for nil by mouth prior to surgery in healthy patients: [5]

AgeSolidsClear liquids
<6 months4 hours2 hours
6–36 months6 hours3 hours
>36 months (including adults)6 hours2 hours

When anaesthesia is required in an emergency, nasogastric aspiration is usually performed to reduce gastric contents and the risk of its pulmonary aspiration. [6]

Unrestricted clear fluids

Fasting guidelines often restrict the intake of any oral fluid after two to six hours preoperatively. However, it has been demonstrated in a large retrospective analysis in Torbay Hospital that unrestricted clear oral fluids right up until transfer to theatre could significantly reduce the incidence of postoperative nausea and vomiting without an increased risk in the adverse outcomes for which such conservative guidance exists. [7]

Public information

A 2016 systematic review found that the information on the internet often provided inaccurate and out-of-date recommendations on preoperative fasting. [8]

Related Research Articles

Antacid Substance that relieves stomach problems

An antacid is a substance which neutralizes stomach acidity and is used to relieve heartburn, indigestion or an upset stomach. Some antacids have been used in the treatment of constipation and diarrhea. Marketed antacids contain salts of aluminum, calcium, magnesium, or sodium. Some preparations contain a combination of two salts, such as magnesium carbonate and aluminium hydroxide.

Tracheal intubation Placement of a tube into the trachea

Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic tube into the trachea (windpipe) to maintain an open airway or to serve as a conduit through which to administer certain drugs. It is frequently performed in critically injured, ill, or anesthetized patients to facilitate ventilation of the lungs, including mechanical ventilation, and to prevent the possibility of asphyxiation or airway obstruction.

Nasogastric intubation Feeding tube going into the stomach through the nose and throat

Nasogastric intubation is a medical process involving the insertion of a plastic tube through the nose, past the throat, and down into the stomach. Orogastric intubation is a similar process involving the insertion of a plastic tube through the mouth. Abraham Louis Levin invented the NG tube. Nasogastric tube is also known as Ryle's tube in Commonwealth countries, after John Alfred Ryle.

Pulmonary aspiration Entry of materials into the larynx (voice box) and lower respiratory tract

Pulmonary aspiration is the entry of material such as pharyngeal secretions, food or drink, or stomach contents from the oropharynx or gastrointestinal tract, into the larynx and lower respiratory tract, the portions of the respiratory system from the trachea (windpipe) to the lungs. A person may inhale the material, or it may be delivered into the tracheobronchial tree during positive pressure ventilation. When pulmonary aspiration occurs during eating and drinking, the aspirated material is often colloquially referred to as "going down the wrong pipe."

Feeding tube Medical device used to provide nutrition to people

A feeding tube is a medical device used to provide nutrition to people who cannot obtain nutrition by mouth, are unable to swallow safely, or need nutritional supplementation. The state of being fed by a feeding tube is called gavage, enteral feeding or tube feeding. Placement may be temporary for the treatment of acute conditions or lifelong in the case of chronic disabilities. A variety of feeding tubes are used in medical practice. They are usually made of polyurethane or silicone. The diameter of a feeding tube is measured in French units. They are classified by the site of insertion and intended use.

Pyloric stenosis Medical condition

Pyloric stenosis is a narrowing of the opening from the stomach to the first part of the small intestine. Symptoms include projectile vomiting without the presence of bile. This most often occurs after the baby is fed. The typical age that symptoms become obvious is two to twelve weeks old.

Postoperative nausea and vomiting (PONV) is the phenomenon of nausea, vomiting, or retching experienced by a patient in the postanesthesia care unit (PACU) or within 24 hours following a surgical procedure. PONV affects about 10% of the population undergoing general anaesthesia each year. PONV can be unpleasant and lead to a delay in mobilization and food, fluid, and medication intake following surgery.

Transesophageal echocardiogram Type of echocardiogram

A transesophageal echocardiogram, or TEE, is an alternative way to perform an echocardiogram. A specialized probe containing an ultrasound transducer at its tip is passed into the patient's esophagus. This allows image and Doppler evaluation which can be recorded. It is commonly used during cardiac surgery and is an excellent modality for assessing the aorta, although there are some limitations.

Perioperative mortality has been defined as any death, regardless of cause, occurring within 30 days after surgery in or out of the hospital. Globally, 4.2 million people are estimated to die within 30 days of surgery each year. An important consideration in the decision to perform any surgical procedure is to weigh the benefits against the risks. Anesthesiologists and surgeons employ various methods in assessing whether a patient is in optimal condition from a medical standpoint prior to undertaking surgery, and various statistical tools are available. ASA score is the most well known of these.

Aspiration pneumonia Medical condition

Aspiration pneumonia is a type of lung infection that is due to a relatively large amount of material from the stomach or mouth entering the lungs. Signs and symptoms often include fever and cough of relatively rapid onset. Complications may include lung abscess. Some include chemical induced inflammation of the lungs as a subtype, which occurs from acidic but non-infectious stomach contents entering the lungs.

The duodenal switch (DS) procedure, gastric reduction duodenal switch (GRDS), is a weight loss surgery procedure that is composed of a restrictive and a malabsorptive aspect.

Gastric lavage, also commonly called stomach pumping or gastric irrigation, is the process of cleaning out the contents of the stomach. Since its first recorded use in early 19th century, it has become one of the most routine means of eliminating poisons from the stomach. Such devices are normally used on a person who has ingested a poison or overdosed on a drug such as ethanol. They may also be used before surgery, to clear the contents of the digestive tract before it is opened.

Adjustable gastric band Inflatable silicone device

A laparoscopic adjustable gastric band, commonly called a lap-band, A band, or LAGB, is an inflatable silicone device placed around the top portion of the stomach to treat obesity, intended to decrease food consumption.

Nothing by mouth is a medical instruction meaning to withhold food and fluids. It is also known as nil per os, a Latin phrase that translates to English as "nothing through the mouth". Variants include nil by mouth (NBM), nihil/non/nulla per os, or complete bowel rest. A liquid-only diet may also be referred to as bowel rest.

A post-anesthesia care unit, often abbreviated PACU and sometimes referred to as post-anesthesia recovery or PAR, or simply Recovery, is a vital part of hospitals, ambulatory care centers, and other medical facilities. Patients who received general anesthesia, regional anesthesia, or local anesthesia are transferred from the operating room suites to the recovery area. The patients are monitored typically by anesthesiologists, certified registered nurse anesthetists, and other medical staff. Providers follow a standardized handoff to the medical PACU staff that includes, which medications were given in the operating room suites, how hemodynamics were during the procedures, and what is expected for their recovery. After initial assessment and stabilization, patients are monitored for any potential complications, until the patient is transferred back to their hospital rooms.

Vagotomy Surgical procedure

A vagotomy is a surgical procedure that involves removing part of the vagus nerve.

Mendelson's syndrome, named in 1946 for American obstetrician and cardiologist Curtis Lester Mendelson, is a form of chemical pneumonitis or aspiration pneumonitis caused by aspiration of stomach contents during anaesthesia in childbirth. This complication of anaesthesia led, in part, to the longstanding nil per os recommendation for women in labour.

Bariatric surgery includes a variety of procedures performed on people who are obese. Long term weight loss through the standard of care procedures is largely achieved by altering gut hormone levels responsible for hunger and satiety, leading to a new hormonal weight set point. Bariatric surgery is a hormonal surgery in these procedures, for which the alteration in gut hormones develops as a result of the procedure's restriction and malabsorption.

Procedural sedation and analgesia (PSA) is a technique in which a sedating/dissociative medication is given, usually along with an analgesic medication, in order to perform non-surgical procedures on a patient. The overall goal is to induce a decreased level of consciousness while maintaining the patient's ability to breathe on their own. Airway protective reflexes are not compromised by this process and therefore endotracheal intubation is not required. PSA is commonly used in the emergency department, in addition to the operating room.

Pyloroplasty

Pyloroplasty is a surgery performed to widen the opening at the lower part of the stomach, also known as the pylorus. When the pylorus thickens, it becomes difficult for food to pass through. The surgery is performed to widen the band of muscle known as the pyloric sphincter, a ring of smooth, muscular fibers that surrounds the pylorus and helps to regulate digestion and prevent reflux. The widening of the pyloric sphincter enables the contents of the stomach to pass into the first part of the small intestine known as the duodenum.

References

  1. 1 2 3 4 5 6 Allman, Keith G.; Iain H. Wilson (2006). Oxford Handbook of Anaesthesia (2nd ed.). Oxford University Press. ISBN   978-0-19-856609-0.
  2. 1 2 Thorell, A; MacCormick, AD; Awad, S; Reynolds, N; Roulin, D; Demartines, N; Vignaud, M; Alvarez, A; Singh, PM; Lobo, DN (September 2016). "Guidelines for Perioperative Care in Bariatric Surgery: Enhanced Recovery After Surgery (ERAS) Society Recommendations". World Journal of Surgery (Professional society guidelines). 40 (9): 2065–83. doi: 10.1007/s00268-016-3492-3 . PMID   26943657.
  3. Crowley, Marianna (20 September 2019). "UpToDate". www.uptodate.com.
  4. 1 2 Maltby JR (April 2006). "Preoperative fasting guidelines" (PDF). Can J Surg. 49 (2): 138–9, author reply 139. PMC   3207537 . PMID   16630428. Archived from the original (PDF) on 2015-12-23. Retrieved 2008-08-20.
  5. Coté CJ (July 1999). "Preoperative preparation and premedication". Br J Anaesth. 83 (1): 16–28. doi: 10.1093/bja/83.1.16 . PMID   10616330.
  6. Legal review of need to place NG tube Archived 2012-02-16 at the Wayback Machine
  7. McCracken, Graham C.; Montgomery, Jane (2017-11-06). "Postoperative nausea and vomiting after unrestricted clear fluids before day surgery: A retrospective analysis". European Journal of Anaesthesiology. 35 (5): 337–342. doi:10.1097/EJA.0000000000000760. ISSN   0265-0215. PMID   29232253. S2CID   4486702.
  8. Roughead, Taren; Sewell, Darreul; Ryerson, Christopher J.; Fisher, Jolene H.; Flexman, Alana M. (December 2016). "Internet-Based Resources Frequently Provide Inaccurate and Out-of-Date Recommendations on Preoperative Fasting". Anesthesia & Analgesia. 123 (6): 1463–1468. doi:10.1213/ANE.0000000000001590. PMID   27644057. S2CID   13452428.