Fasting For Surgery – What’s the Deal with That?

pre-operative fasting

If you have undertaken a surgical operation before, it is common to be asked to “fast at least for six hours before your operation.” While this may present some important benefits and serve as a precautionary measure before anesthetics, the reasons behind doing so remains a mystery for many people.

What is fasting?

Fasting is an act of abstinence from food or drinks for a set period of time. Prior to the advent of general anaesthesia, fasting was strictly considered a spiritual (religious) exercise. but fasting prior to surgery has shown to be crucial in the prevention of medical complications.

Benefits Of Preoperative Fasting

Fasting serves as a precautionary measure to prevent lung injuries.

An unfasted patient places themselves at great risk of a condition known as ‘pulmonary aspiration.’ This is a situation when the stomach contents travels up the oesophagus (gullet) and enters the lungs. When this content enters the lungs the gastric fluid itself can create a chemical burn of the lungs. In addition food particles can block the flow of air into the lungs placing the patient as immediate life threatening risks. The chemical burn of gastric fluid damages the ability of the lungs to allow oxygen from the air to enter the blood stream.  This can result in patients having very low oxygen levels in their body, a condition known as ‘hypoxia.’  The management of hypoxia will require supplemental oxygen for the patient for hours to days in some cases.

This is the primary reason why anesthetists will insist on the recommendations of preoperative fasting guidelines. It is believed that this precaution will help to promote gastric emptying prior to induction of anesthesia.

Who is at risk of pulmonary aspiration?

Even though a patient have taken the necessary steps of following the fasting guidelines, there are still some people who are at increased risks of pulmonary aspiration. These are patients that have a medical condition that delays the emptying of the stomach. Some examples of medical conditions that delay stomach emptying are diabetes, obesity and Parkinsons Disease.

Some medications can also promote poor stomach emptying. The most common medications that can delay the stomach emptying are opiate medications. Opiate medications are used to manage pain with an example being oxycodone.

Are there side effects associated with preoperative fasting?

Although there is solid evidence in fasting prior to surgery, it does not come without side effects. Anaesthetists from the Anaesthetic Billing company ‘Fast Tracking Anaesthetic Billing Services’ have noted the main disadvantage of prolonged fasting is that it increases the level of discomfort of patients. This is more pronounced in extremities of ages such as infants and the elderly. Symptoms that patients may experience are headaches and dizziness.

What do the experts recommend?

The American Society of Anesthesiologists have provided guidelines for patients in preparation for surgery. These are:

  • Clear liquids like carbonated beverages, black coffee, clear tea, fruit juice without pulp, and water, two hours prior to surgery.
  • Light meals such as toast and tea with milk six hours prior to surgery.

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