There’s a little part of me that likes to swim upstream and question commonly held beliefs to see if they hold up to scrutiny. Maybe I was a trout in my past life. I’m sure I made a grizzly bear a delicious breakfast (I like to think I was breakfast and not dinner. Breakfast is such a nice time of day….)

Anyway, despite my qualities as a mammalian breakfast item, I like to test common mores because whenever I do, I find something lacking in them. There’s usually either an illogical basis for a practice, or a reason for doing that practice that is contrary to its original conception. Take as an example, the use of surgical gloves. We currently use gloves as a standard and universal procedure to prevent infection either to patients or providers. Now, despite the fact that I agree with their use and practice universal precautions, it may be interesting to note that the surgical glove was invented not to prevent infection but rather dermatitis.

Back in the late 1800s, Dr William Steward Halstead, the renowned surgeon at Johns Hopkins Hospital and Medical School, considered by some the father of modern surgery, was performing his surgical procedures without gloves. His surgical assistant, Caroline Hampton, was suffering from a chronic dermatitis of the hands as a result of the carboxylic acid (AKA phenol) then used at the time to maintain antisepsis. In order to prevent this reaction, Dr Halstead had a pair of rubber gloves created for Ms Hampton, and many years later, we all use surgical gloves. The two later married. I like to imagine Dr Halstead and Ms Hampton working side-by-side while he invented modern surgery, and perhaps their burgeoning love affair was solidified by his gift of rubber gloves. Ah, the romance.

For starters, let’s talk first about clear fluids. How long before surgery should a patient stop drinking? This is actually a more important question than when to stop solid foods because dehydration plays a significant role in many diseases, and it would be nice to have hydrated patients. Delal and colleagues prospectively randomized 100 patients undergoing elective surgery to one of two groups, fasting overnight (50 patients) versus those given 150 mL of water two hours prior to surgery (50 patients). While undergoing general anesthesia, they inserted a nasogastic tube, collecting gastric fluids looking at fluid volume and pH.

These researchers found the gastric volume was less in the patients who drank water two hours preop (5.5 +/- 3.70 mL versus 17.1 +/- 8.2 mL). Yes, less volume in the patients who drank water before surgery! They found the mean pH to be similar between the groups. One critique of the study could be that the authors did not report the incidence of actual aspiration (pH and fluid volume are indirect measures of aspiration risk). However, given the incidence of aspiration during anesthesia is one in 7000-8000 ASA 1 and II level patients,² this small experimental group of 100 patients isn’t powered to find aspiration episodes.

Other studies seem to point to this same conclusion,² so let’s ask the gods of systematic reviews (No, not Zeus…the Cochrane Collaboration) and see what they say.

After systematically reviewing 38 randomized controlled comparisons, they found the following: “There was no indication that the volume of fluid permitted during the preoperative period (ie, low or high) resulted in a difference in outcomes from those participants that followed a standard fast” and concluded “there was no evidence to suggest a shortened fluid fast results in an increased risk of aspiration, regurgitation or related morbidity compared with the standard ’nil by mouth from midnight’ fasting policy.”³

Drink up, my preoperative friends!

Seriously, though, keep in mind these studies included mostly healthy patients in non-emergent situations, so exercise caution with extrapolation. If patients have disorders that increase gastric transit time, then by all means be cautious and increase your fluid NPO time. Additionally, we have to adhere to hospital policies, and if their policy doesn’t agree with current evidence, then join a committee to help make a change (that’s also a good practice builder).

By the way, in case you’re wondering, “clear fluid” means water, coffee, pulp-free juice, tea, or broth.

What about solid foods? Let’s take a mental trip to Europe to look into this one. In 1983, Miller and associates prospectively looked at 45 English patients undergoing gynecologic surgery. Patients were randomly assigned to one of four groups based on preanesthesia medications. However, they grouped these patients into either an overnight fast or a light breakfast consisting of one slice of buttered toast and tea or coffee four hours before surgery. Immediately after general anesthesia induction, the patients underwent aspiration of their stomach contents via nasogastric tube. They measured the gastric volume and pH. Mean gastric volume was approximately the same for both groups (approximately 11 mL). Additionally, there was no difference between levels of acidity in either group.⁴ As in the other study, these researchers did not look at complications. Additionally, any large pieces of solid food left in the stomach would not have been aspirated by the nasogastric tube. So, these findings actually reflect the liquid portions in the stomach.

Are you seeing the trend my fellow NPOers? NPO doesn’t seem to matter much, whether we’re talking about liquids or food.

Let’s stay in Europe and finish up our meal with a short summary of the European Society of Anesthesiology Guidelines⁵:

Feeling hungry my fasting preoperative friends? Me too. This sacred cow, NPO after midnight, is ready to go to the barbeque. Let’s serve that up with a nice helping of preoperative toast and clear liquids. Why doesn’t that sound appetizing? Oh well.