No Need for Long Fast Before General Anesthesia

By Ellen Kuwana
Neuroscience for Kids Staff Writer
May 20, 2002

If you will have a general anesthestic during surgery and are told not to eat or drink anything in the hours before the surgery, make sure you understand your doctor's advice. The practice of fasting before surgery was adopted decades ago to prevent food from being breathed into the lungs while the patient was under general anesthesia. This problem used to be one of the most common causes of death associated with surgery under general anesthesia. Now that anesthetics have improved, this is no longer a major concern.

A study published in The American Journal of Nursing reported that 91% of 155 patients surveyed had been told to not eat or drink anything after midnight prior to surgery. In fact, the patients fasted for a longer duration than required, on average for 12-14 hours. Some patients had surgery when they had not had anything to drink for 20 hours or anything to eat for 37 hours! Such fasting caused patients to be significantly thirsty and some suffered from headaches and hypoglycemia (low blood sugar level).

The American Society of Anesthesiologists established new guidelines in 1999 that recommend that patients be allowed to drink clear liquids up to two hours before the surgery and to eat a light meal up to six hours before the surgery. The main problem with asking patients to fast for a certain period before surgery is that the actual time for the surgery is unpredictable. Although you may be scheduled for surgery at 10 a.m., your case may take more time than anticipated. Thus, you may not have surgery until 1 p.m. It's also possible that your case may go faster than expected or may be cancelled. You might be wheeled into surgery at 8 a.m.! You can see how this variability would affect the number of hours that you had fasted.

There are some patients who should fast longer than the general recommendation of six hours. These include patients who are diabetic, morbidly obese, pregnant, or those taking opioid pain medications. These patients, for physiological reasons, would have delayed emptying of the stomach contents.

Bottom line: While pre-surgery fasting is still an important part of preparing to have surgery under general anesthesia, it is not necessary to go into surgery extremely hungry or thirsty--in fact, it may be better for your recovery if you don't. Talk to your doctors and make sure that you understand their instructions completely.

Note: special thanks to Dr. Christopher Bernards of the University of Washington Department of Anesthesiology for his insightful comments on this topic.

References and further information:

  1. Crenshaw, J. and Winslow, E.H. Preoperative Fasting: Old Habits Die Hard: Research and published guidelines no longer support the routine use of 'NPO after midnight,' but the practice persists. American Journal of Nursing, 102:36-44, 2002.
  2. Anesthesia - American Society of Anesthesiologists

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