The first case of possible aspiration from general anesthesia occurred in 1848, when Hannah Greener, a 15-year-old girl underwent chloroform anesthesia for the removal of a toenail. Her surgeon, Dr. Meggison, who conducted the anesthetic, administered an extra dose of chloroform dropped through a handkerchief placed over her face. However, she began to cough and her lips turned blue. Dr. Meggison tried to revive her with water and a few drops of brandy; in spite of his best efforts, she choked and died. Subsequently, Simpson, one of the early proponents of chloroform anesthesia, extensively investigated the case. He came to the conclusion that Hannah had probably died of pulmonary aspiration, that had little to do with any toxic effect of chloroform. Seven years later, John Snow recommended 6 hours of fasting before chloroform anesthesia. The text books of that era followed this up and stipulated variable periods of fasting for patients undergoing procedures under anesthesia.
Fasting in the ICU
Feeding is commonly interrupted in critically ill patients for presumed intolerance, performance of investigations, and surgical procedures that may be airway or non-airway related. Fasting may occur for extended periods on a regular basis in ICU patients in spite of the airway protection offered by a cuffed endotracheal tube or a tracheostomy. Fasting prior to extubation in the ICU is a typical example. Extubation rarely takes place at a fixed time, resulting in unduly prolonged periods of fasting. It may not occur at all and may be reconsidered the following day. The fasting protocol may get repeated day after day for several days until the patient finally gets extubated, leading to a significantly reduced delivery of nutrition.
Fasting guidelines are highly variable; besides, adherence to the guidelines is also not consistent. The American Society of Anesthesiology recommends fasting for solid food of 8 hours, while the European Society of Anesthesia stipulates a 6-hour fasting period.1 A UK survey revealed only 20% of institutions had clear cut guidelines, with a relatively low adherence of 66%.2
Possible harmful effects of fasting
A large international multi-center study observed that critically ill patients were uniformly underfed, receiving an average of only 59% of the prescribed energy.3 This was also evident in the CALORIES trial, where the calorie target was not achieved with either the enteral (62% of target) or the parenteral route (73% of target). Undernutrition may lead to an increase in the rate of nosocomial infections, besides leading to higher all-cause mortality, bloodstream infections, and prolonged ICU and hospital stay.4,5 Besides meeting nutritional requirements, enteral feeds maintain the integrity of the gut mucosal barrier and reduce the incidence of infections through bacterial translocation.6 Enteral nutrition also plays an important part in modulating the stress response to critical illness.7
Pre-procedural fasting in critically ill patients with protected airway
Historically, fasting has been recommended to reduce the incidence of aspiration. Traditional fasting guidelines are intended for awake, otherwise healthy patients, eating normal food who are scheduled to undergo elective surgical procedures. Do we need to religiously apply the same rigid guidelines in our ICU patients who undergo non-airway related procedures, who have their airways protected to the maximal extent possible by endotracheal intubation or tracheostomy? Unfortunately, no standard fasting guidelines exist for critically ill patients with protected airways. Malnutrition may lead to an increase in the incidence of infectious complications, which in turn may lead to prolongation of the duration of mechanical ventilation, ICU, and hospital stay.8,9
Is it time to reconsider the duration of fasting in ICU patients – what is the evidence?
Uninterrupted enteral nutrition is an important facet of care of burns patients, who often need to undergo repeated, prolonged surgical procedures, during which significant nutritional deficits occur due to interruption of enteral feeding. In a retrospective study, Varon et al. evaluated the feasibility and safety of intraoperative feeding in burns patients. Thirty-three patients were included; 17 patients received intraoperative enteral feeds while 16 did not. Feeding was carried out through a post-pyloric tube and continued throughout the intraoperative period. No difference in mortality was observed between the two groups; besides, there was no intraoperative incidence of regurgitation or aspiration in either group. Patients who continued to be fed intraoperatively received 98% of the prescribed nutrition, compared to 70–73% among those who were not fed. The authors concluded that continued intraoperative enteral feeding in burns patients was feasible without an increase in the incidence of intraoperative regurgitation, aspiration, or increase in mortality while maintaining nutritional targets.10
In a study among surgical ICU patients, 14 received continued feeding through a postpyloric tube until the commencement of the procedure. The procedures included debridement of necrotizing fasciitis, bowel surgery, and orthopedic procedures. The mean duration of interruption of feeding per procedure was only 222.4 minutes; an additional 4.7 hours of feeding was provided through avoidance of the conventional period of NPO.
Critically ill trauma patients on invasive mechanical ventilation who underwent surgical or non-surgical procedures were the subjects of the study by Pousman et al. Enteral feeds administered through a gastric tube were continued for up to 45 min of the procedure; feeding through a small bowel feeding tube was continued until the time of commencement of the procedure. The investigators specifically evaluated the incidence of complications related to continued enteral feeding, including ventilated associated pneumonia, urinary infections, catheter-related bloodstream infections, wound infections, hypoglycemia, and intraoperative vomiting and regurgitation. There was no increase in the incidence of complications compared to a control group who underwent a conventional duration of fasting before the procedure. The authors concluded that continued feeding up until the commencement of the procedure was safe and allowed to meet nutritional targets better.11
How about fasting prior to bedside percutaneous tracheostomy? Yeh et al. compared ten patients who were continued on routine enteral feeding with 22 patients who were fasted according to American Society of Anesthesiology NPO guidelines.12 Patients who continued to be fed received higher median calories and had less calorie deficit on the day of the procedure compared to the control group. The overall incidence of complications was not different between groups, including airway-related, gastrointestinal and infectious complications.
Continuing enteral nutrition in patients with a protected airway who do not undergo airway-related procedures does not lead to an increase in the incidence of complications or adverse clinical outcomes. Continued feeding enables more efficient achievement of nutritional goals with a reduced incidence of nutritional deficiencies.
Feeds are interrupted for varying periods of time in patients with protected airways based on an archaic belief that complications related to regurgitation and aspiration may ensue. This tradition-borne practice is based on recommendations meant for otherwise healthy patients, who eat normal food and present for elective procedures. The presumed higher incidence of aspiration-related complications related to continued enteral feeding in patients with protected airways is not supported by the available evidence. A shorter period of fasting allows more optimal achievement of nutritional goals; prolonged 8-hour fasting, or NPO from midnight may be inappropriate in critically ill patients with protected airways. The available evidence suggests that a reduced duration of fasting or even no routine fasting prior to general anesthesia in critically ill adult patients who have a cuffed endotracheal or tracheostomy tube in place may be safe and appropriate, especially in the context of non-airway-related and non-abdominal surgery. Continued feeding, in addition to improved achievement of nutritional goals, may also lead to more favourable clinical outcomes. Needless to emphasize, patients must be closely observed during and after the procedure for subclinical signs of aspiration.
1. López Muñoz AC, Busto Aguirreurreta N, Tomás Braulio J. [Preoperative fasting guidelines: an update]. Rev Esp Anestesiol Reanim. 2015;62(3):145-156. doi:10.1016/j.redar.2014.09.006
2. Segaran E, Lovejoy TD, Proctor C, et al. Exploring fasting practices for critical care patients – A web-based survey of UK intensive care units. J Intensive Care Soc. 2018;19(3):188-195. doi:10.1177/1751143717748555
3. Alberda C, Gramlich L, Jones N, et al. The relationship between nutritional intake and clinical outcomes in critically ill patients: results of an international multicenter observational study. Intensive Care Med. 2009;35(10):1728-1737. doi:10.1007/s00134-009-1567-4
4. Villet S, Chiolero RL, Bollmann MD, et al. Negative impact of hypocaloric feeding and energy balance on clinical outcome in ICU patients. Clin Nutr. 2005;24(4):502-509. doi:10.1016/j.clnu.2005.03.006
5. Strack van Schijndel RJM, Weijs PJM, Koopmans RH, Sauerwein HP, Beishuizen A, Girbes ARJ. Optimal nutrition during the period of mechanical ventilation decreases mortality in critically ill, long-term acute female patients: a prospective observational cohort study. Crit Care. 2009;13(4):R132. doi:10.1186/cc7993
6. Alpers DH. Enteral feeding and gut atrophy. Curr Opin Clin Nutr Metab Care. 2002;5(6):679-683. doi:10.1097/00075197-200211000-00011
7. McClave SA, Sexton LK, Spain DA, et al. Enteral tube feeding in the intensive care unit: factors impeding adequate delivery. Crit Care Med. 1999;27(7):1252-1256. doi:10.1097/00003246-199907000-00003
8. Seron-Arbeloa C, Zamora-Elson M, Labarta-Monzon L, Mallor-Bonet T. Enteral nutrition in critical care. J Clin Med Res. 2013;5(1):1-11. doi:10.4021/jocmr1210w
9. Marik PE, Zaloga GP. Early enteral nutrition in acutely ill patients: a systematic review. Crit Care Med. 2001;29(12):2264-2270. doi:10.1097/00003246-200112000-00005
10. Varon DE, Freitas G, Goel N, et al. Intraoperative Feeding Improves Calorie and Protein Delivery in Acute Burn Patients. J Burn Care Res. 2017;38(5):299-303. doi:10.1097/BCR.0000000000000514
11. Pousman RM, Pepper C, Pandharipande P, et al. Feasibility of implementing a reduced fasting protocol for critically ill trauma patients undergoing operative and nonoperative procedures. JPEN J Parenter Enteral Nutr. 2009;33(2):176-180. doi:10.1177/0148607108327527
12. Yeh DD, Cropano C, Quraishi SA, et al. Periprocedural nutrition in the intensive care unit: a pilot study. J Surg Res. 2015;198(2):346-350. doi:10.1016/j.jss.2015.06.039