NPO for clear liquids: Star Wars edition

Myron Yaster MD, Lynne Maxell MD, and Melissa Brooks Peterson MD

Original Article

Disma N, Frykholm P, Cook-Sather SD, Lerman J. Pro-Con Debate: 1- vs 2-hour fast for clear liquids before anesthesia in children. Anesth Analg. 2021;133:581–591 PMID: 34403386

Editorial

Nguyen, Khoa N. MD Davis, Peter J. MD. The 1-Hour Versus 2-Hour Clear Liquid Fasting Pro-Con Debate: What Problem Are We Solving? Anesth Analg 2021;133:578–580  PMID: 34403385

“I find your lack of faith disturbing.” — Darth Vader

Should the current clear liquid fasting period remain 2-hours or be reduced to one?  I (Myron) am increasingly convinced that those pushing for change (1 hour) or maintaining the status quo (2 hours) are the pediatric anesthesia equivalence of the rebel alliance versus the empire….

Of the many Pediatric Anesthesia Articles of the Day that have been published since Ron Litman’s untimely death, the one that generated the MOST reader comment was “NPO guidelines are they bubbameisas?” (“old wives tales”) (July 19). So, when I read the pro-con debate on clear liquid fasting guidelines and an accompanying editorial in the September issue of Anesthesia and Analgesia by some of the biggest “waring stars” in the pediatric anesthesia universe, I pushed this review to the front of the PAAD publishing line. 

Before discussing the pros and cons of the 1- vs 2-hour NPO for clears debate, the editorial by Drs. Khoa and Davis point out that no one -- not OR nurses, surgeons and their schedulers, anesthesiologists, nor the patients given fasting instructions -- can agree on or fully understand what a clear liquid actually is.  As the editorial points out: “Patients have choices of clear liquids ranging from water, juice (with or) without pulp, and tea or black coffee, to energy drinks, fortified water, and clear nutritional supplements. Each of those clear liquids have a wide range of concentrations of carbohydrates, proteins, or additives that may alter their clearance. Because Jell-O contains gelatin, is Jell-O a clear liquid, does it matter if it is red or green? What about chicken broth? Is chicken broth acceptable as a clear liquid, or does it depend on its fat content? To complicate matters, are there differences in gastric emptying time between various clear and nonclear liquids?” Our personal favorite: is chewing gum or a hard candy a clear? And, don’t even ask us what to do if the gum was swallowed! 

The goal of fasting guidelines is to minimize the risk of pulmonary aspiration of gastric contents.  There are essentially 3 issues with aspiration of gastric contents: particulates, pH, and volume.  Of the 3, the least important is volume. We want to emphasize that this debate is about clear liquids and not particulate-producing solids or milk! Everyone pretty much agrees that prolonged clear liquid fasting times are common and not a good idea (prolonged overnight fasts, scheduling delays, etc). Indeed, as the editorial suggests our focus should be “on having patients drink up until 2 hours before surgery rather than emphasizing not drinking after a certain time period”. In fact, the guidelines would more correctly called “feeding (or drinking) guidelines” rather than “fasting guidelines”. It would be less confusing. As the editorial and the “Con” argument point out, communication is the key to avoiding excessively long fasting intervals, by clearly instructing families to encourage fluid intake until 2 hours prior to arrival. The actual fasting time is frequently much longer than minimally acceptable time for clear liquids because of the emphasis on fasting rather than drinking until the accepted time.

The “Pro” side (the “rebel alliance”) for reducing the fasting time to one hour: The 2-hour fast creates patient/parent dissatisfaction, hemodynamic instability, difficulty achieving vascular access, and perioperative energy imbalance.  Further, the one hour fast is more than enough to achieve an empty stomach and does not increase the risk of pulmonary aspiration of gastric contents.

The “Con” side (the “EMPIRE”) for keeping the 2-hour clear liquid fasting time: It works! Utilizing the current guidelines, the risk of aspiration is about 1:10,000.  Why fix something that isn’t broken? Indeed, “there is mounting published evidence of aspiration after recent implementation of 1-hour fasting guidelines …In a retrospective study of 10,015 anesthetics where children ingested unlimited fluids up to the time of surgery, pulmonary aspiration occurred in 3 children and was suspected in an additional 14 cases, yielding a total incidence of 17:10,000”. The type of the clear liquid also really matters and may delay gastric emptying. Although plain water reliably leaves little residual gastric volume after about an hour, carbohydrate laden fluids do not!! Thus, “it is imprudent to allow children to drink uncontrolled volumes of liquids with uncontrolled caloric content 1 hour before anesthesia”. Finally, the “Con” proponents point out that there is very little evidence supporting the claim that the 2 hour clear liquid fast leads to hemodynamic instability, inability to achieve vascular access or produces energy imbalance.

Our final take.  NPO violations are amongst the most common reasons for cancelling scheduled OR cases.  Precision in defining “what is a clear liquid is probably more important than the duration of the fast.  We wonder, why not simply change “clear liquids” to “water”? 

Although it’s been done before, We’d suggest that we reprise a “Pro-Con” session on this topic at a future SPA meeting, given the shifts in the literature we have seen in the last 5 years.

Myron Yaster MD, Lynne Maxwell MD, and Melissa Brooks Peterson MD

Note from Myron: Why not simply change to water? W C Fields, the notoriously and famously drunk comedian of the 1920-30’s, was asked “why he drank so much whiskey…why not drink water”, a reporter asked?  He replied: “Water? Fish f..ck in water”…