NPO for sedation? Don’t swallow the myth

A brief review of the evidence for fasting in sedation

When was your last meal? Yes, I know that your leg is currently bent at about a 90 degree angle, but I must know, when did you last eat? You had some chips an hour ago? Well I’m very sorry, but you are just going to have to wait. Next time, remember that you need an empty stomach if you are going to have an emergency…

The myth that fasting is required for emergency department procedural sedation has been frustrating physicians and patients for years. We don’t give activated charcoal to patients 90 minutes after their ingestion, because we assume that their stomachs are empty, but for some reason we make the poor child with a broken arm sit around for hours before we are willing to fix them.

Honestly, this rule has been mostly ignored by emergency physicians for years, but it still occasionally rears its ugly head. Timing of last meal is still a question on my sedation sheets. Unfortunately, sometimes patients still get caught in this myth. So let’s review the evidence, and understand why we should just stop asking this question.

Emergency Department Evidence

Agrawal D, Manzi SF, Gupta R, Krauss B. Preprocedural fasting state and adverse events in children undergoing procedural sedation and analgesia in a pediatric emergency department. Annals of emergency medicine. 2003; 42(5):636-46. PMID: 14581915

Quick summary: A prospective observational trial looking at 1014 children undering procedural sedation in the ED, of whom 905 had data on fasting status available. More than half the patients (509) did not meeting fasting guidelines. There was no difference in adverse events between the fasting and non-fasting groups. There was no difference in vomiting between the fasting and non-fasting groups. There were no cases of aspiration.

Roback MG, Bajaj L, Wathen JE, Bothner J. Preprocedural fasting and adverse events in procedural sedation and analgesia in a pediatric emergency department: are they related? Annals of emergency medicine. 2004; 44(5):454-9. PMID: 15520704

Quick summary: This is a retrospective analysis of prospectively gathered observational data. They looked at 2085 procedural sedations, for which fasting time was documented in 1555 cases. The incidence of adverse events was the same whether fasting was less than 2 hours, 2-4 hours, 4-6 hours, 6-8 hours, or over 8 hours. There were no clinically apparent aspiration events among these 2000 patients.

Treston G. Prolonged pre-procedure fasting time is unnecessary when using titrated intravenous ketamine for paediatric procedural sedation. Emergency medicine Australasia : EMA. 2004; 16(2):145-50. PMID: 15239730

Quick summary: This is a prospective observational study looking at 257 pediatric patients undergoing emergency department procedural sedation. There were no aspirations or vomiting during the procedures. There was no statistical relationship between fasting time and vomiting, but children who were fasted for more than 3 hours vomited twice as often as the un-fasted children (16% vs 7%).

Babl FE, Puspitadewi A, Barnett P, Oakley E, Spicer M. Preprocedural fasting state and adverse events in children receiving nitrous oxide for procedural sedation and analgesia. Pediatric emergency care. 2005; 21(11):736-43. PMID: 16280947

Quick summary: This is a prospective observational study of 220 children undergoing procedural sedation in the ED with nitrous oxide. Most (71%) did not meet fasting guidelines. There were no serious adverse events or aspirations. Vomiting occurred 7% of the time, with no difference between the two groups.

Bell A, Treston G, McNabb C, Monypenny K, Cardwell R. Profiling adverse respiratory events and vomiting when using propofol for emergency department procedural sedation. Emergency medicine Australasia : EMA. 2007; 19(5):405-10. PMID: 17919212

Quick summary: This is a prospective observational study of 400 patients (adult and pediatric) undergoing procedural sedation in the ED with propofol. Most (71%) patients did not meet the ASA guidelines for fasting. There was not difference in adverse events between the two groups. Vomiting occurred in 0.4% of fasted patients as compared to 0.8% of non-fasted patients (1 patient in each group). There were no aspirations.

McKee MR, Sharieff GQ, Kanegaye JT, Stebel M. Oral analgesia before pediatric ketamine sedation is not associated with an increased risk of emesis and other adverse events. The Journal of emergency medicine. 2008; 35(1):23-8. PMID: 18343079

Quick summary: This is a retrospective chart review looking at 471 pediatric patients undergoing emergency department procedural sedation. 43% of children received oral medication before sedation (and therefore were not NPO). There was no difference in adverse events whether or not you received oral analgesics within 6 hours of sedation.

Taylor DM, Bell A, Holdgate A. Risk factors for sedation-related events during procedural sedation in the emergency department. Emergency medicine Australasia : EMA. 2011; 23(4):466-73. PMID: 21824314

Quick summary: This as a prospective observational study of 2623 patients undergoing emergency department procedural sedation looking at adverse events. There was only 1 aspiration event (0.05%), and that patient had been fasting for 24 hours. There was no association between time of last oral intake and vomiting (which overall occured 1.6% of the time) or any other adverse event.

Wenzel-Smith G, Schweitzer B. Safety and efficiency of procedural sedation and analgesia (PSA) conducted by medical officers in a level 1 hospital in Cape Town. South African medical journal = Suid-Afrikaanse tydskrif vir geneeskunde. 2011; 101(12):895-8. PMID: 22273033

Quick summary: An observational study of 166 procedural sedations performed by an ED house officer in South Africa. The vast majority of patients (78%) were not fasted. There was no increase in complications among the unfasted patients (4.7% vs 6.9% if fasted).

Beach ML et al. Major Adverse Events and Relationship to Nil per Os Status in Pediatric Sedation/Anesthesia Outside the Operating Room: A Report of the Pediatric Sedation Research Consortium. Anesthesiology. 124(1):80-8. 2016. PMID: 26551974

Quick summary: This is data from the Pediatric Sedation Research Consortium. It is prospectively collected data on a huge number of sedations (139,142) over 4 years at 42 hospitals. There were 25,401 patients who were not NPO prior to their sedation. Aspiration occurred in 8 patients who were NPO and 2 who weren’t, event rates of 0.8/10,000 and 1/10,000 respectively (odds ratio, 0.81; 95% CI, 0.08 to 4.08; P = 0.79). There also wasn’t any difference in major complications.

UPDATE

A new paper was published on the exact same day as this post:

Bhatt M, Johnson DW, Taljaard M, et al. Association of Preprocedural Fasting With Outcomes of Emergency Department Sedation in Children. JAMA Pediatr. 2018.

Quick summary: This is  planned secondary analysis of a large prospective observational study of pediatric sedation at 6 Canadian pediatric EDs. There were 6183 sedations, and more than 50% did not meet the ASA guidelines for fasting. There were no cases of aspiration. There was no association between time spent fasting and adverse events or vomiting.

Systematic Reviews

Thorpe RJ, Benger J. Pre-procedural fasting in emergency sedation. Emergency medicine journal : EMJ. 2010; 27(4):254-61. PMID: 20385672

Quick summary: This is a systematic review looking at the risk of aspiration during procedural sedation in the emergency department. They identified reports of 4657 adult ED procedural sedations and 17672 pediatric ED procedural sedations, and among all those cases there was a single case of aspiration (in a patient who was fasted for 5 hours and require 2 separate sedations). They did not identify any association between fasting time and any other adverse event.

Some OR evidence

Brady M, Kinn S, O’Rourke K, Randhawa N, Stuart P. Preoperative fasting for preventing perioperative complications in children. The Cochrane database of systematic reviews. 2005; PMID: 15846750

Quick summary: This is a systematic review that looked at the RCTs of fasting regimens preoperatively in a pediatric population. There are 23 trials looking at 2350 children. There was only one case of aspiration among these 2350 children, and the authors thought it was the result of airway management rather than NPO (but it did occur in a group that was allowed clear fluids up to 2 hours before surgery). There was no difference in gastric volume or pH among children that were allowed to drink fluids up to 2 hours pre-op as compared to those kept fasting, but not surprisingly, children allowed to drink were more comfortable and better behaved than those starved.

Guidelines

Godwin SA et al. Clinical policy: procedural sedation and analgesia in the emergency department. Ann Emerg Med. 2014;63(2):247-58.PMID: 24438649

As part of the ACEP clinical policy process, they did a systematic review. They found 5 studies that cover thousands of patients, and found no evidence that fasting decreased aspiration or other adverse events. The official policy is “Level B: Do not delay procedural sedation in adults or pediatrics in the ED based on fasting time. Preprocedural fasting for any duration has not demonstrated a reduction in the risk of emesis or aspiration when administering procedural sedation and analgesia.”

American Society of Anesthesiologists Task Force on Sedation and Analgesia by Non-anesthesiologists. Practice guidelines for sedation and analgesia by non-anesthesiologists. Anesthesiology. 2002 Apr;96(4):1004-17. PMID:11964611

A quote from the anesthesiologists: “The literature does not provide sufficient evidence to test the hypothesis that preprocedure fasting results in a decreased incidence of adverse outcomes in patients undergoing either moderate or deep sedation.”

Summary

Procedural sedation is incredibly safe. The primary reason for fasting patients is to prevent aspiration, and in these studies it occurs in about 1 in 10,000 sedations, whether or not you are fasted. Fasting also had no effect on any other adverse events, such as vomiting.

The emphasis on aspiration often overlooks the many harms of fasting. Many patients are forced to stay NPO while waiting to be assessed, and very few of these patients end up requiring sedation. Depending on your wait times, this could result in dehydration in small children, but even if it isn’t that extreme, eating and drinking are an important part of being human. Adding hunger pains to the pain of a broken arm seems needless and cruel.

Delaying procedures increases pain. Delaying procedures can make the procedures more difficult, as swelling or spasm makes reduction more difficult, or prolonged atrial fibrillation becomes more resistant to cardioversion. Delaying procedures also clogs emergency department beds, making it harder to see other patients who need emergency care.

We should not be cavalier. We still need to use clinical judgement. It might make sense to delay sedation in an intoxicated patient who just finished eating 25 tacos as a dare. Furthermore, not every patient requires sedation, and we should be facile in other options, including a variety of nerve blocks.

However, for the most part, we just need to stop asking. The ACEP guideline is clear – do not delay procedural sedation based on ED fasting time. It is time that we stop swallowing this myth.

 

Other FOAMed

SGEM summary of the Beach paper

LIFTL Peri-procedural fasting

EM Updates: The harms of fasting

Cite this article as: Justin Morgenstern, "NPO for sedation? Don’t swallow the myth", First10EM blog, May 7, 2018. Available at: https://first10em.com/npo-for-sedation/.

Author: Justin Morgenstern

Emergency doctor working in the community. FOAM enthusiast. Evidence based medicine junkie. “One special advantage of the skeptical attitude of mind is that a man is never vexed to find that after all he has been in the wrong.” - William Osler

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