Literature Review

Reviewed by Corrie E. Chumpitazi, MD

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

Beach ML, Cohen DM, Gallagher SM, Cravero JP. Anesthesiology. 2016 Jan;124(1):80-8. doi: 10.1097/ALN.0000000000000933.


Studies that have attempted to define the incidence of aspiration or pulmonary complications during sedation/anesthesia of children with respect to nil per os (NPO) status or other factors are difficult because of the relatively infrequent rate of these complications.

The Pediatric Sedation Research Consortium consists of 42 participating institutions with elective sedation services that submit consecutive patient encounter information to a central database. The authors evaluated aspiration episodes and a combined outcome of major adverse events (defined as aspiration, death, cardiac arrest, or unplanned hospital admission) with respect to NPO status, American Society of Anesthesiologists physical status, age, propofol use, procedure types, and urgency of the procedure.

A total of 139,142 procedural sedation/anesthesia encounters were collected between September 2, 2007 and November 9, 2011. There were 0 deaths, 10 aspirations, and 75 major complications. NPO status was known for 107,947 patients, of whom 25,401 (23.5 %) were not NPO. Aspiration occurred in 8 of 82,546 (0.97 events per 10,000) versus 2 of 25,401 (0.79 events per 10,000) patients who were NPO and not NPO, respectively (odds ratio, 0.81; 95% CI, 0.08 to 4.08; P = 0.79). Major complications occurred in 46 of 82,546 (5.57 events per 10,000) versus 15 of 25,401 (5.91 events per 10,000) (odds ratio, 1.06; 95% CI, 0.55 to 1.93; P = 0.88). Multivariate adjustment did not appreciably impact the effect of NPO status.

The analysis suggests that aspiration is uncommon. NPO status for liquids and solids is not an independent predictor of major complications or aspiration in this sedation/anesthesia data set.

Stringent nil per os (NPO) guidelines from the American Society of Anesthesiology (ASA) have been applied to the area of procedural sedation (1,2).  These guidelines have been adopted by the American Academy of Pediatrics (AAP) and were last updated in 2006 (3).  However, the ASA/AAP guideline is not evidence-based and can be difficult to follow for nonelective procedures.  NPO, as defined in this study, is no solid food for at least eight hours, no nonclear fluids for at least six hours, and no clear fluids for at least two hours prior to the sedation.

Emergency department preprocedural fasting guidelines have been informed by such studies as Green et al. which suggested the ability to perform dissociative sedation, non-extended moderate sedation, and brief deep sedation for semi-urgent procedures when children have been NPO three hours (4).

Application of shortened fasting guidelines to the area of monitored anesthesia care has been controversial, and previous retrospective studies have been unable to more broadly inform practice due to the relative infrequent rate of serious complications.  The rate of aspiration in this study remained low, 1 per 10,000, with aspiration defined as an event where emesis was noted or food material was found in the oral/pharyngeal cavity- associated with any of the following: new cough, wheeze, increase in respiratory effort, change in chest radiograph indicative of aspiration or new need for oxygen therapy after recovery from sedation.

This study adds the largest number of prospectively collected non-fasted children reported in the literature; 25,401, without a statistically significant increased major adverse event: aspiration, death, cardiac arrest or unplanned admission to a hospital.  As expected infants less than one year, ASA physical class III or IV status, gastrointestinal diagnosis, obstructive sleep apnea, upper respiratory infection, and those undergoing an airway or gastroenterology procedure were at increased risk for major adverse events. 

This study dichotomized patients as fasted or not, thus additional information may be gained by closer evaluation as to whether, for example, a patient fasted seven hours and 59 minutes was different from a patient fasted 20 minutes. This study is also limited by the fact that NPO information for nonclear liquids was not available.  This important study of the PSRC adds further weight that the relationship between NPO status and patient injury is uncertain. Within the setting of these high quality sedation practices, NPO time did not increase adverse events.  With this additional information, many pediatric emergency centers will continue to use the shortened fasting guidelines in the emergency center if approved by their institutional policies/procedures. However, further studies are needed prior to broad application to other procedural sedation sites (4,5).     


  1. American Society of Anesthesiologists Task Force on Sedation and Analgesia by Non-Anesthesiologists Practice guidelines for sedation and analgesia by non-anesthesiologists. (2002). Anesthesiology. 96(4), 1004-1017.

  2. Hoffman, G.M., Nowakowski, R., Troshynski, T.J., Berens RJ, & Weisman, S.J. (2002). Risk reduction in pediatric procedural sedation by application of an American Academy of Pediatrics/American Society of Anesthesiologists process model.Pediatrics,109(2), 236-243.

  3. Coté, C.J., & Wilson, S.  American Academy of Pediatrics; American Academy of Pediatric Dentistry, Work Group on Sedation. (2006). Guidelines for monitoring and management of pediatric patients during and after sedation for diagnostic and therapeutic procedures: an update. Pediatrics. 118(6), 2587-2602.

  4. Green, S.M., Roback, M.G., Miner, J.R., Burton, J.H., & Krauss, B. (2007). Fasting and emergency department procedural sedation and analgesia: a consensus-based clinical practice advisory. Annuals of Emergency Medicine. 49(4), 454-461.

  5. Godwin, S.A., Caro, D.A., Wolf, S.J., Jagoda. A.S., Charles, R., Marett, B.E., Moore, J. (2005). Clinical policy: procedural sedation and analgesia in the emergency department. Annuals of Emergency Medicine, 45(2), 177-196.

Figure 1. Green et al.

Fig 1

Figure: Prudent Limits of Targeted Depth and Length of Ed Procedural Sedation and Analgesia According to Presedation Assessment of Aspiration Risk

Figure Footnotes

A - Higher-risk patients are those with one or more of the following present to a degree individually or cumulatively judged clinically important by the treating physician

  • Potential for difficult or prolonged assisted ventilation should an airway complication occur (eg, short neck, small mandible/micrognathia, large tongue, tracheomalacia, laryngomalacia, history of difficult intubation, congenital anomalies of the airway and neck, sleep apnea)
  • Conditions predisposing to esophageal reflux (eg, elevated intracranial pressure, esophageal disease, hiatal hernia, peptic ulcer disease, gastritis, bowel obstruction, ileus, tracheo-esophageal fistula)
  • Extremes of age (eg, >70 years or <6 months)
  • Severe systemic disease with definite functional limitation (ie, ASA physical status 3 or greater)
  • Other clinical findings leading the EP to judge the patient to be at higher than standard risk (eg, altered level of consciousness, frail appearance)

B - Procedural urgency

  • Emergent (eg, cardioversion for life-threatening dysrhythmia, reduction of markedly angulated fracture or dislocation with soft tissue or vascular compromise, intractable pain or suffering).
  • Urgent (eg, care of dirty wounds and lacerations, animal and human bites, abscess incision and drainage, fracture reduction, hip reduction, lumbar puncture for suspected meningitis, arthrocentesis, neuroimaging for trauma)
  • Semi-urgent (eg, care of clean wounds and lacerations, shoulder reduction, neuroimaging for new-onset seizure, foreign body removal, sexual assault examination)
  • Non-urgent or elective (eg, non-vegetable foreign body in external auditory canal, chronic embedded soft tissue foreign body, ingrown toenail)

C - Procedural sedation and analgesia terminology and definitions:

  • Minimal sedation (anxiolysis):1 and 15 A drug-induced state during which patients respond normally to verbal commands. Although cognitive function and coordination may be impaired, ventilatory and cardiovascular functions are unaffected.
  • Moderate sedation (formerly “conscious sedation”):1 and 15 A drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation. Reflex withdrawal from a painful stimulus is not considered a purposeful response. No interventions are required to maintain a patent airway, and spontaneous ventilation is adequate. Cardiovascular function is usually maintained.
  • Dissociative Sedation:15 and 17 A trance-like cataleptic state induced by the dissociative agent ketamine characterized by profound analgesia and amnesia, with retention of protective airway reflexes, spontaneous respirations, and cardiopulmonary stability.
  • Deep sedation:1 and 15 A drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully following repeated or painful stimulation. The ability to independently maintain ventilatory function may be impaired. Patients may require assistance in maintaining a patent airway and spontaneous ventilation may be inadequate. Cardiovascular function is usually maintained.
  • General anesthesia:1 and 15 A drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation. The ability to independently maintain ventilatory function is often impaired. Patients often require assistance in maintaining a patent airway, and positive pressure ventilation may be required because of depressed spontaneous ventilation or drug-induced depression of neuromuscular function. Cardiovascular function may be impaired.

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