NPO GUIDELINES are they “bubbameisters”?

Myron Yaster MD and Libby Elliott MD

Original article

Jennifer J Lee, Jerri C Price, Andrew Duren, Alon Shertzer, Robert Hannum, Francis A Akita, Shuang Wang, Judy H Squires, Oliver Panzer, Jacquelin Herrera, Lena S Sun, Nicholas A Davis. Ultrasound Evaluation of Gastric Emptying Time in Healthy Term Neonates after Formula Feeding. Anesthesiology. 2021 Jun 1;134(6):845-851. PMID: 33861856


Laszlo Vutskits. Neonatal Preoperative Fasting: Time for a Change? Anesthesiology. 2021 Jun 1;134(6):823-825. PMID: 3386185

My mother Sally, of blessed memory, was absolutely convinced that if I (MY) went out to play with wet hair, I would catch a cold.  I have no idea where or how this old wive’s tale (in Yiddish a “bubbameister”) came from, but it was “truth” in Sally’s home until her dying day. No amount of arguing or explaining that colds came from viruses would change her mind.  Which brings us to preprocedural nil per os (NPO) guidelines.  Are our fasting guidelines bubbameisters? Is it time to revisit them, and embrace more than 20 years of data demonstrating the safety of reduced fasting times?1

Because general anesthetics blunt or abolish protective reflexes, pre‐operative and pre-procedural fasting is employed to minimize gastric contents and in turn, decrease the risk of pulmonary aspiration (“Mendelson syndrome”).2 By and large fasting guidelines appear to have worked. Aspiration is extremely rare, however, our current concerns about aspiration may be out of proportion to the actual risk, particularly for clear liquids.  Rebecca Isserman and I (LE) and our colleagues at the Children’s Hospital of Philadelphia’s published our experience with changing fasting guidelines for clear liquids to one hour.3   Making this a national guideline change is currently under discussion at the Society for Pediatric Anesthesia’s Quality and Safety Committee and at the ASA.4   Other organizations have already made this change.5, 6

The article by Lee et al. from Columbia University’s Morgan Stanley Children’s Hospital puts yet another nail in the NPO guideline coffin.  The most current ASA based NPO guidelines (clear fluid intake for up to 2 hours, breast milk up to 4, infant formula up to 6, and milk or solid food for up to 6-8  hours) made no substantive changes to the guidelines previously published in 1999.7,8 Much evidence of the safety of reduced fasting times has been published over the last 20 plus years. In today’s PAAD, Lee, et al, used gastric ultrasound to measure gastric emptying time in formula fed infants “to support or refute current preprocedural NPO guidelines for neonates”. Their stated goal was to “optimize patient safety and well-being in addition to patient/parental satisfaction. [Our] hypothesis is that the gastric emptying time in healthy neonates after formula feeding is less than the current guideline of 6 h of fasting.”3  

Indeed, their hypothesis was correct. Lee, et al. “found the time to return to baseline antral cross-sectional area was 92.9 ± 42.6 min in 46 healthy full-term neonates aged 0 to 5 days. The upper range of gastric emptying time was 150 min, while the upper limit at the 99% CI was 109.8 min. There were no significant differences in gastric emptying time in subgroup analyses according to sex or mode of delivery. These findings suggest that the current fasting guidelines (6 hours) may be more stringent than necessary by more than 3 h”. They conclude: “gastric emptying time, as assessed by serial ultrasound after formula feeding in healthy full-term neonates, was determined to never exceed 2.5 h using upper range or 99% CI.” Intuitively, this makes sense and explains why babies feed about every 2.5- 3 hours!

The findings in this study validate the guidelines long used (without reported adverse events) at the Children’s Hospital of Philadelphia: formula fed neonates may safely feed up to 4 hours prior to anesthesia. Changing fasting guidelines will be a difficult and slow process: the bubbameister lives on in our regulatory and professional society guidelines.  Until our professional societies embrace the abundance of evidence accumulated over the last 20-30 years, and put these changes into writing, individual practitioners and groups may be exposing themselves to legal risk.  On the other hand, it may be time to pick up our pitchforks and storm the castle to force these changes. 

What do you think?

Myron Yaster MD and Libby Elliott MD

PS: In keeping with Ron Litman’s spirit and guidance before he died, I’ve (MY) tried to keep these PAADs brief, really brief.  In working with Libby, Mel Brooks, and others I’ve started to include some references too.  Should I continue?  What are your thoughts?


1.       Friedrich S, Meybohm P, Kranke P: Nulla Per Os (NPO) guidelines: time to revisit? Curr Opin Anaesthesiol 2020; 33: 740-745

2.       Mendelson CL: The aspiration of stomach contents into the lungs during obstetric anesthesia. Am J Obstet Gynecol 1946; 52: 191-205

3.       Isserman R, Elliott E, Subramanyam R, Kraus B, Sutherland T, Madu C, Stricker PA: Quality improvement project to reduce pediatric clear liquid fasting times prior to anesthesia. Paediatr Anaesth 2019; 29: 698-704

4.       Vutskits L, Davidson A: Fluid Fasting in Children: Solid Science? Anesthesiology 2020; 133: 493-494

5.       Green SM, Leroy PL, Roback MG, Irwin MG, Andolfatto G, Babl FE, Barbi E, Costa LR, Absalom A, Carlson DW, Krauss BS, Roelofse J, Yuen VM, Alcaino E, Costa PS, Mason KP: An international multidisciplinary consensus statement on fasting before procedural sedation in adults and children. Anaesthesia 2020; 75: 374-385

6.       Thomas, M; Morrison, C; Newton, R; Schindler, E. Consensus statement on clear fluids fasting for elective pediatric general anesthesia. Pediatric Anesthesia 2018, 28(5): 411-414

7.       Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration: Application to Healthy Patients Undergoing Elective Procedures: An Updated Report by the American Society of Anesthesiologists Task Force on Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration. Anesthesiology 2017 126(3): 376-393

8.       Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients undergoing elective procedures: a report by the American Society of Anesthesiologist Task Force on Preoperative Fasting. Anesthesiology. 1999 Mar;90(3):896-905.