Preoperative Fasting Guidelines

Copyright © 2017 International Anesthesia Research Society. Unauthorized reproduction of this article is prohibited. April 2017 • Volume 124 • Number 4 1041

Copyright © 2017 International Anesthesia Research Society DOI: 10.1213/ANE.0000000000001964

Your patients should be drinking clear liquids until 2 hours before surgery. If they are not, you should stop reading and change your hospital practices. Your patients will thank you. They will be less thirsty, be less anxious, and have improved patient satisfaction with- out an increase in the rate of pulmonary aspiration.1 These practices have been recommended by the American Society of Anesthesiologists preoperative fasting guidelines since 1999. Therefore, the question is “why are not we doing this?” The accompanying manuscript by Shiraishi et al2 pro- vides evidence that you should feel safe in allowing your patients to do so. The interesting questions that follow are (1) What should patients drink preoperatively? (2) What are the outcome benefits of preoperative oral hydration?

In this trial, magnetic resonance imaging studies were conducted preoperatively to measure gastric volumes. The study enrolled 10 normal weight and 10 morbidly obese patients (average body mass index 45 kg/m2). After a 9-hour fast, the morbidly obese patient had larger volumes of gas- tric content (73 vs 31 mL). However, 2 hours after drink- ing 500 mL of a carbohydrate beverage (OS-1), stomach volumes had returned to baseline levels (50 and 30 mL) in both the obese and nonobese patients, respectively. In fact, gastric content volume was significantly lower at 2 hours after fluid ingestion than that at preingestion, after a 9-hour fast, in the morbidly obese group. This study suggests that gastric emptying may not be delayed in the morbidly obese, and a preoperative carbohydrate beverage decreases gastric volume in these patients compared with an overnight fast.

These authors used a carbohydrate beverage, OS-1, typi- cally used for rehydration, which is only available in Japan. This potentially limits the generalizability of these results to other countries. Another drawback of this study is its small sample size. In addition, OS-1 is a simple carbohydrate bev- erage of fructose and glucose, and these results may not apply to the maltodextrin-containing solutions with com- plex carbohydrate used in various enhanced recovery after

surgery (ERAS) protocols. In addition, we also cannot nec- essarily assume that these findings will apply to the super- obese patients (body mass index >50 kg/m2).

ERAS is defined as the development of multidisciplinary perioperative protocols that incorporate multiple best prac- tices to improve patient outcomes.3 One of the key princi- ples of ERAS is to reduce the stress of surgery to a patient. Allowing patients to drink clear fluids 2 hours before sur- gery decreases their thirst, anxiety, and improves their strength.1 With a patient who is nil per os (NPO) after mid- night, we are essentially starving our patients of food and drink and then challenging them with the stress of surgery. Carbohydrate beverages given preoperatively have the ben- efit of decreasing the catabolic state associated with starva- tion.4 Studies have shown decreased insulin resistance and decreased hyperglycemia after a preoperative carbohy- drate beverage.5,6 This is important for our surgical patients because elevated glucose levels in the postoperative period are associated with increased surgical complications.7

The American Society of Anesthesiologists guidelines for preoperative fasting state that it is appropriate to fast from intake of clear liquids at least 2 hours before elective procedures requiring anesthesia.8 Surveys have shown that only a few hospitals still keep their patients NPO after mid- night, but any culture change in medicine is a slow process.9 Surveys at 2 US hospitals in 2004 and 2008 reported preop- erative fasting times of 6 to 11 hours for liquids and 11 to 14 hours for solids.10,11 A 2010 survey of German anesthesiolo- gists found only a few (7%) hospitals practiced strict NPO after midnight, but only one-third (34%) followed the full preoperative fasting guidelines of 2 hours for clear liquids and 6 hours for solid food.12 Most followed a more relaxed regimen in between these 2 options. A 2015 study in Iran found that patients undergoing elective surgery were kept NPO from liquids for 11.54 hours and from a light meal for 12.46 hours.13 These studies show that we have been slow to adopt the 2-hour allowance of clear liquids before surgery.

One barrier to allowing patients to drink before surgery has been the fear of pulmonary aspiration. A concern is that oral intake before surgery will increase residual gastric vol- ume and a decrease in gastric pH, causing a higher risk of aspiration pneumonitis. However, studies have found that ingestion of clear liquids 2 hours before surgery results in smaller residual gastric volumes and higher gastric pH levels compared with longer fasts.8 In multiple trials, there was no occurrence of pulmonary complications with pre- operative carbohydrate beverage treatment.5 In healthy

Preoperative Fasting Guidelines: Why Are We Not Following Them?: The Time to Act Is NOW Ramon E. Abola, MD, and Tong J. Gan, MD, MHS, FRCA

From the Department of Anesthesiology, Stony Brook Medicine, Stony Brook, New York.

Accepted for publication January 12, 2017.

Funding: None.

The authors declare no conflicts of interest.

Reprints will not be available from the authors.

Address correspondence to Tong J. Gan, MD, MHS, FRCA, Department of Anesthesiology, Stony Brook Medicine, HSC-4–060, Stony Brook, NY 11764. Address e-mail to [email protected]




Copyright © 2017 International Anesthesia Research Society. Unauthorized reproduction of this article is prohibited.



volunteers, gastric content returned to baseline in 120 minutes after receiving a clear carbohydrate beverage pre- operatively.14 However, the addition of protein in the pre- operative solution lengthened the time to baseline gastric volume to 3 hours. This study by Shiraishi et al2 provides evidence that is consistent with these previous findings. All patients had residual gastric volumes that were similar or less than an overnight fast after drinking 2 hours before sur- gery. It further provides evidence that gastric emptying to clear liquids is not delayed in the morbidly obese patient. Barrier pressure, the difference between lower esophageal sphincter pressure and gastric pressure, remains positive in obese patients throughout the induction of anesthesia.15 All of these studies suggest that fasting obese patients are at low risk of aspiration, similar to nonobese patients.

The second barrier has been in determining what is the optimal drink for patients to have before surgery. Complex carbohydrate beverages with maltodextrin have been shown to decrease insulin resistance. The American Society of Enhanced Recovery published a consensus statement for colorectal surgery recommending unrestricted access to clear fluids up to 2 hours before surgery to maintain hydration. They recommend oral hydration with solutions containing 45 g of carbohydrate to improve insulin sensi- tivity, preferably complex carbohydrate (maltodextrin).16 A Cochrane review including 1976 participants in 27 trials found preoperative carbohydrate loading (>45 g of either simple or complex carbohydrates) before surgery trended toward improved postoperative insulin resistance.17 Preoperative carbohydrate beverages may also be associ- ated with decreased length of stay after major abdominal surgery.5 Historically, recommendations for preoperative carbohydrate beverage treatment have excluded diabetic patients; however, this may be incorrect. Gustafsson et al18 found that patients with type 2 diabetes showed no signs of delayed gastric emptying and that a carbohydrate-rich drink could be administered 180 minutes before anesthesia without risk of hyperglycemia or aspiration.

One of the drawbacks of maltodextrin carbohydrate solu- tions is their cost. Sports drinks or rehydration fluid are less expensive and have been suggested as an alternative source for preoperative carbohydrates. OS-1, used in the study by Shiraishi et al,2 is a rehydration solution recommended for use with vomiting, diarrhea, fever, or excess sweating. Comparing the two, sports beverages typically contain higher carbohy- drate amounts compared with rehydration fluids. OS-1 has a carbohydrate content of 2.5 g/100 mL, whereas a typical sports drink such as Gatorade has a carbohydrate content of 6 g/100 mL. What is not known is the effect of these preopera- tive simple carbohydrate solutions on insulin resistance after surgery and the incidence of postoperative hyperglycemia. Seven-day exposure of sucrose, but not glucose, in healthy volunteers was associated with decreased insulin sensitivity.19

The question about appropriate oral intake also includes the labor and delivery ward. Starving pregnant mothers results in increased ketoacidosis, which is decreased when given carbohydrate fluids. Ingestion of sports drink when in labor was not found to increase gastric volumes.20 Oral intake of modest amounts of clear liquid in uncompli- cated patients is recommended by the American College of

Obstetrics and Gynecology.21 Restrictive oral intake policies and NPO policies during labor put in place because of con- cerns of aspiration should be re-evaluated.

The American Society of Anesthesiologists guidelines allowing for clear liquids until 2 hours before surgery have been in place since 1999. These authors should be com- mended for providing further evidence of the safety of oral hydration 2 hours before surgery. To determine if this is an issue in your hospital, ask your next patient how long they have fasted. If it has been longer than 2 hours, you should change your practice. The time to act is NOW. E

DISCLOSURES Name: Ramon E. Abola, MD. Contribution: This author helped prepare the manuscript. Name: Tong J. Gan, MD, MHS, FRCA. Contribution: This author helped prepare the manuscript. This manuscript was handled by: Richard C. Prielipp, MD.

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liberal preoperative fasting regimen improves patient comfort and satisfaction with anesthesia care in day-stay minor surgery. Minerva Anestesiol. 2011;77:680–686.

2. Shiraishi T, Kurosaki D, Nakamura M, et al. Gastric fluid vol- ume change after oral rehydration solution intake in morbidly obese and normal controls: a magnetic resonance imaging- based analysis. Anesth Analg. 2017;124:1174–1178.

3. Kehlet H. Fast-track colorectal surgery. Lancet. 2008;371:791–793. 4. Bilku DK, Dennison AR, Hall TC, Metcalfe MS, Garcea G. Role

of preoperative carbohydrate loading: a systematic review. Ann R Coll Surg Engl. 2014;96:15–22.

5. Awad S, Varadhan KK, Ljungqvist O, Lobo DN. A meta- analysis of randomised controlled trials on preoperative oral carbohydrate treatment in elective surgery. Clin Nutr. 2013;32:34–44.

6. Svanfeldt M, Thorell A, Hausel J, et al. Randomized clinical trial of the effect of preoperative oral carbohydrate treatment on postoperative whole-body protein and glucose kinetics. Br J Surg. 2007;94:1342–1350.

7. Kwon S, Thompson R, Dellinger P, Yanez D, Farrohki E, Flum D. Importance of perioperative glycemic control in general sur- gery: a report from the Surgical Care and Outcomes Assessment Program. Ann Surg. 2013;257:8–14.

8. American Society of Anesthesiologists Committee. Practice guidelines for preoperative fasting and the use of pharmaco- logic agents to reduce the risk of pulmonary aspiration: appli- cation to healthy patients undergoing elective procedures. Anesthesiology. 2011;114:495–511.

9. Pandit SK, Loberg KW, Pandit UA. Toast and tea before elective surgery? A national survey on current practice. Anesth Analg. 2000;90:1348–1351.

10. Crenshaw JT, Winslow EH. Preoperative fasting duration and medication instruction: are we improving? AORN J. 2008;88:963–976.

11. Wachtel RE, Dexter F. Reducing surgical patient fasting times. AORN J. 2009;89:830–831.

12. Breuer JP, Bosse G, Seifert S, et al. Pre-operative fasting: a nationwide survey of German anaesthesia departments. Acta Anaesthesiol Scand. 2010;54:313–320.

13. Bilehjani E, Fakhari S, Yavari S, et al. Adjustment of preopera- tive fasting guidelines for adult patients undergoing elective surgery. Open J Intern Med. 2015;5:115–118.

14. Lobo DN, Hendry PO, Rodrigues G, et al. Gastric emptying of three liquid oral preoperative metabolic preconditioning regimens measured by magnetic resonance imaging in healthy adult volunteers: a randomised double-blind, crossover study. Clin Nutr. 2009;28:636–641.

15. de Leon A, Thörn SE, Wattwil M. High-resolution solid-state manometry of the upper and lower esophageal sphincters



Copyright © 2017 International Anesthesia Research Society. Unauthorized reproduction of this article is prohibited.

Preoperative Fasting Guidelines

April 2017 • Volume 124 • Number 4 1043

during anesthesia induction: a comparison between obese and non-obese patients. Anesth Analg. 2010;111:149–153.

16. Thiele RH, Raghunathan K, Brudney CS, et al; Perioperative Quality Initiative (POQI) I Workgroup. American Society for Enhanced Recovery (ASER) and Perioperative Quality Initiative (POQI) joint consensus statement on perioperative fluid management within an enhanced recovery pathway for colorectal surgery. Perioper Med (Lond). 2016;5:24.

17. Smith MD, McCall J, Plank L, Herbison GP, Soop M, Nygren J. Preoperative carbohydrate treatment for enhancing recovery after elective surgery. Cochrane Database Syst Rev. 2014;8:CD009161.

18. Gustafsson UO, Nygren J, Thorell A, et al. Pre-operative carbo- hydrate loading may be used in type 2 diabetes patients. Acta Anaesthesiol Scand. 2008;52:946–951.

19. Beck-Nielsen H, Pedersen O, Lindskov HO. Impaired cellular insulin binding and insulin sensitivity induced by high-fructose feeding in normal subjects. Am J Clin Nutr. 1980;33:273–278.

20. Kubli M, Scrutton MJ, Seed PT, O’Sullivan G. An evalua- tion of isotonic ‘sport drinks’ during labor. Anesth Analg. 2002;94:404–408.

21. American College of Obstetricians and Gynecologists. Oral intake during labor. ACOG Committee Opinion No. 441. Obstet Gynecol. 2009;114:714.


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