Please read the Preoperative Fasting article by Crenshaw (2011) located in the eReserve. This article was written about a decade ago. Consider what the aut

HOURS

Continuing Education 2.4

By Jeannette T. Crenshaw, DNP, RN, IBCLC, LCCE, NEA-BC

Preoperative Fasting: Will the Evidence Ever Be Put into Practice?

In 1999, the American Society of Anesthesiologists called for less restrictive preoperative fasting, yet clinicians continue to prescribe NPO after midnight.

Overview: Decades of research support the safety and

health benefits of consuming clear liquids, including those that

are carbohydrate rich, until a few hours before elective surgery

or other procedures requiring sedation or anesthesia. Still, U.S.

clinicians routinely instruct patients to fast for excessively long

preoperative periods. Evidence-based guidelines, published over

the past 25 years in the United States, Canada, and throughout

Europe, recommend liberalizing preoperative fasting policies. To

improve patient safety and health care quality, it’s essential that

health care professionals abandon outdated preoperative fast-

ing policies and allow available evidence to guide preanesthetic

practices.

Keywords: aspiration, fasting, gastric fluid volume, pneumo-

nia, preoperative care, preprocedural fasting, preoperative carbo-

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38 AJN ! October 2011 ! Vol. 111, No. 10 ajnonline.com

show a progressive decline in aspiration incidence, from 0.15% in 194613 to 0.006% in 2002.14 As for stomach contents at the time of surgery, rates of gastric emp- tying vary widely, depending on the type of liquid or food consumed.3-5 Clear liquids leave the stomach al- most immediately, while full liquids and solids remain for significantly longer periods. It’s long been estab- lished that patients who drink clear liquids a few hours before surgery have significantly lower gastric volumes and similar or higher pH values compared with those who fast overnight, suggesting that drinking clear liq- uids may stimulate gastric emptying and dilute acidic gastric secretions, thereby lowering the risk of pulmo- nary aspiration and increasing patient safety.15-17

The custom of preoperative fasting was introduced in the mid-1800s to minimize vomiting associated with the anesthetic chloroform.9 Although physicians of that era recognized that a recent meal increased the risk of chloroform-associated vomiting, they encouraged pa- tients to drink clear liquids until a few hours before surgery. In fact, the 19th-century British surgeon Joseph Lister, who founded antiseptic medicine and wrote what may be the first published preoperative fasting guide- lines, clearly distinguished between the effects of solids and liquids on chloroform-anesthetized patients. He ad- vised surgeons, “While it is desirable that there should be no solid matter in the stomach when chloroform is administered, it will be found very salutary to give a cup of tea or beef-tea about two hours previously.”9

By the end of the 19th century, Lister’s advice was being followed and patients were commonly permitted a cup of “beef tea” (beef bouillon) a few hours before surgery.12 This practice of differentiating liquids from solids in preoperative instruction prevailed until after World War II, when Mendelson documented an asthma- like syndrome of expiratory wheezing, dyspnea, cyano- sis, and pulmonary lesions following the aspiration of stomach contents by obstetric and laboring patients who were under general anesthesia and not intubated.9, 13 Soon after, the standard of care for surgical patients was to prescribe npo after midnight.9, 10, 12, 18

RESISTANCE TO REVISED GUIDELINES Over the past 25 years, professional organizations of anesthesiologists and anesthetists in Canada, the United States, and Europe revised their guidelines on preop- erative fasting in light of a growing body of evidence that healthy patients who consume clear liquids until

Imagine two patients diagnosed with colon cancer, both scheduled for colectomy tomorrow morn- ing: Susan Moore, who lives in New York City, and Paul Shaw, who lives in London. In all like-

lihood, Ms. Moore will be instructed to stop eating and drinking at midnight, whereas Mr. Shaw will proba- bly be advised to drink a carbohydrate-rich clear liquid this evening as well as tomorrow morning and continue drinking clear liquids until two hours before surgery. Why the disparity? Preoperative fasting practices in the United States often disregard both the guidelines of the American Society of Anesthesiologists (ASA)1, 2 and the most current available evidence on the subject. The ASA recommends that healthy patients consume clear

liquids up to two hours before elective surgery or con- scious sedation but cautions that their guidelines aren’t intended for women in labor and may need to be mod- ified for patients with conditions that affect gastric emptying or fluid volume and those in whom airway management may be difficult.3-5 Evidence gathered throughout the world over the past 25 years not only supports the ASA guidelines, but establishes the health benefits of preoperative carbohydrate loading (through the consumption of carbohydrate-rich clear liquids) the evening before and the morning of surgery.6, 7 So why does the practice of prescribing npo (non per os, or nothing by mouth) from midnight preceding a sched- uled surgery persist—and how can clinicians promote a change?

A PRACTICE BASED ON MYTH The U.S. practice of requiring an extended fast before scheduled anesthesia or sedation is based primarily on the following three myths8-12: • Myth: Overnight fasting from all solids and liquids

is the optimal approach to reduce the risk of pul- monary aspiration during anesthesia.

• Myth: Gastric emptying time is the same for clear liquids as for full liquids (those that are not transpar- ent, such as milk, creamed soup, and nonstrained fruit juice) and solids.

• Myth: Clear liquids ingested up to two hours be- fore surgery increase the risk of vomiting and pul- monary aspiration.

In fact, increased awareness of risk factors for as- piration, together with modern anesthetic practices10 and improved anesthetic agents, has dramatically re- duced the risk of pulmonary aspiration. Large studies

Fasting instructions for healthy presurgical patients should be based on the known differences in gastric transit times of

clear liquids, full liquids, and other foods.

[email protected] AJN ! October 2011 ! Vol. 111, No. 10 39

of the ASA guidelines—found that the majority of pa- tients (91%) were instructed to remain npo after mid- night.1 On average, patients fasted 12 hours from liquids and over 14 hours from solids, but some fasted for up to 20 hours from liquids. A follow-up quality im- provement study involving 275 surgical patients was conducted at the same institution between June and October 2004—two years after a liberalized preop- erative fasting policy had been put into effect and in- troduced through an intensive education program.2 Findings revealed little improvement in practice. Again, most patients (85%) were instructed to remain npo after midnight, and fasting times were similar to those in the 2000 study: patients fasted from clear liquids for an average of 11 hours and from solids for an average of over 14 hours.

EMERGING EVIDENCE ON PREOPERATIVE CARBOHYDRATE LOADING U.S. preoperative fasting instructions for healthy pa- tients should be based on the known differences in gastric transit times of clear liquids, full liquids, and other foods (see Table 1).3-5 Instructions should at first focus on liberalizing clear liquid policies because it’s here that we see the greatest difference between rou- tine preoperative instructions (npo after midnight) and evidence-based guidelines.1, 2 But that’s not enough. Updated guidelines, based on current literature, clin- ical data, and expert opinion, show that having a light meal, such as toast and a clear liquid, up to six hours before surgery poses no greater risk of aspiration for healthy presurgical patients than remaining npo af- ter midnight.3-5 Moreover, studies have shown that pro- longed fasting is not benign.

In addition to discomforts such as thirst, hunger, anx- iety, drowsiness, and dizziness, excessive preoperative fasting may have adverse physiologic effects, includ- ing dehydration, insulin resistance, postoperative hy- perglycemia, muscle wasting, and a weakened immune response.18, 23-25 Clear liquids, taken alone, may be in- sufficient to ward off such effects. Emerging evidence suggests that, in addition to offering clear liquids up until two hours before anesthesia or sedation, the best way to avert the harmful consequences of preoperative fasting is to prescribe a carbohydrate-rich clear bev- erage to be consumed two to three hours before the scheduled procedure (see The Benefits of Preoperative Carbohydrate Loading 6, 23, 24, 26-29). This type of preop- erative preparation has been shown to reduce post- operative insulin resistance,24, 30-34 nausea and vomiting,35 and loss of muscle strength.29, 36 It’s also associated with a shorter hospital length of stay.24 Based on evidence from the past decade that strongly supports the ben- efits of preoperative carbohydrate loading, the Euro- pean Society for Clinical Nutrition and Metabolism,6 the British Association for Parenteral and Enteral Nu- trition, the Association for Clinical Biochemistry, the Association of Surgeons of Great Britain and Ireland,

a few hours before anesthesia or sedation are as safe as and more comfortable than patients who fast for six to eight hours beforehand.3, 5, 19-21 In 2003, a system- atic review of 22 randomized controlled trials found that patients who drank clear liquids up to 90 minutes before surgery were at no greater risk of vomiting, as- piration, or related morbidity during anesthesia or sedation than were fasting patients, regardless of the volume of clear liquids they consumed.20 In 2009, the American College of Gastroenterology revised its guide- lines for colorectal cancer screening, emphasizing the importance of “aggressive hydration before and dur- ing” colonoscopy preparation and referencing ASA guidelines that support clear liquids until two hours before procedures requiring sedation.4, 22

Unfortunately, the publication of new evidence and revised practice guidelines doesn’t ensure their dissem- ination and implementation. Colleagues at hospitals throughout the United States have indicated that “npo after midnight” is commonly prescribed for presurgical patients. A study of 155 adults at one U.S. medical cen- ter who underwent surgery between November 1999 and May 2000—eight to 14 months after publication

40 AJN ! October 2011 ! Vol. 111, No. 10 ajnonline.com

Table 1. Summary of the American Society of Anesthesiologists Preoperative Fasting Guidelines for Healthy Patients of All Agesa

a The guidelines are intended only for healthy patients who are undergo- ing elective procedures with anesthesia (general or regional), sedation, or analgesia. They are not intended for women in labor and may need to be modified for patients in whom airway management may be difficult and for patients with reduced gastric emptying or conditions that affect fluid volume (such as pregnancy, obesity, diabetes, hiatal hernia, gastro- esophageal reflux disease, and ileus or bowel obstruction).3-5 b Clear liquids include water, fruit juices without pulp, carbonated bever- ages, clear tea, and black coffee. c Since nonhuman milk is similar to solids in gastric emptying time, the amount ingested must be considered when determining an appropriate fasting period. d A light meal might consist of clear liquids and toast. Source: Practice guidelines for preoperative fasting and the use of phar- macologic agents to reduce the risk of pulmonary aspiration: application to healthy patients undergoing elective procedures: an updated report by the American Society of Anesthesiologists Committee on Standards and Practice Parameters. Anesthesiology 2011;114(3):495-511.

Ingested Material Minimum Fasting

Period (hr)

Clear liquidsb 2

Breast milk 4

Infant formula 6

Nonhuman milkc 6

Light meald 6

Regular meal 8

[email protected] AJN ! October 2011 ! Vol. 111, No. 10 41

While U.S. surgeons have described preopera- tive carbohydrate loading as “promising” but

preliminary,26 the European Society for Clinical Nutri- tion and Metabolism recommends oral preoperative carbohydrate loading for most patients.6 Here’s how it can mitigate some of the more dangerous conse- quences of preoperative fasting.

Insulin resistance. Even after brief periods of fast- ing, metabolism slows to forestall starvation, dramat- ically reducing insulin sensitivity.24, 27 The trauma of surgery also produces insulin resistance, but unlike fasting, surgery speeds the metabolic rate, accelerat- ing catabolism. Insulin levels rise in compensation, but because cells are resistant to it, blood glucose levels rise as well, lowering the ratio of insulin to glucagon and intensifying gluconeogenesis. By reducing insulin sensitivity, prolonged preoperative fasting exacer- bates the metabolic stress of surgery, both during the procedure and—depending on the scale of the sur- gery and the recovery period—for up to several weeks thereafter. The resultant hyperglycemia is associated with increased morbidity and hospital length of stay.

Providing the patient with a carbohydrate-rich bev- erage two to three hours before surgery ameliorates the metabolic response to the fasting state. In a se- ries of randomized studies, patients were given either a glucose infusion or a 400 mL drink containing 50 g of glucose two to three hours before surgery.24 Gastric emptying occurred within two hours of consumption; two to three hours afterward, insulin was measured at normal postprandial levels with insulin action having increased by 50%.

A double-blind, randomized controlled trial of 252 Swedish patients scheduled for abdominal surgery examined plasma glucose and serum insulin levels, preop erative discomfort, residual gastric volume, and gastric acidity in those who fasted from midnight and those who consumed either flavored water (placebo) or a carbohydrate-rich clear liquid the evening before surgery (800 mL) and at the hospital about two hours before anesthesia induction (400 mL).28 Glucose and insulin levels were measured in all three groups before the beverages were consumed, 40 and 90 minutes afterward, and following induction, when stomach contents were aspirated and analyzed.

The researchers found no significant differences in gastric volumes or pH between the groups and

reported no adverse outcomes from consuming the beverages. After drinking the carbohydrate beverage, patients reported thirst, hunger, and anxiety that was significantly less than the thirst, hunger, and anxiety reported by the water and control groups. Before morning beverages were consumed, glucose and in- sulin levels didn’t differ between the groups. As ex- pected, 40 and 90 minutes after consumption of the carbohydrate beverage, glucose and insulin levels were significantly higher in the carbohydrate group than in the other two groups. At induction, however, the carbohydrate group had significantly lower glu- cose levels than the others, although their insulin lev- els remained significantly higher.

Immune function. The stress response to surgery substantially weakens a patient’s immune system. To explore the effects of preoperative carbohydrate-rich beverages on the immune response to surgery, Dutch researchers measured human leukocyte antigen (HLA)- DR expression on monocytes in blood samples col- lected from 30 healthy patients the day before and the day after they underwent elective orthopedic sur- gery.23 Patients had been randomly assigned to fast overnight or to consume one of two carbohydrate-rich beverages with equivalent carbohydrate content. Af- ter surgery, the HLA-DR expression on monocytes had decreased significantly in the fasting group, but there was no drop in the two carbohydrate groups, suggesting that the carbohydrate-rich beverages pre- served immune function.

Muscle wasting. Because fasting depletes gly- cogen stores, requiring the body to generate glucose from noncarbohydrate sources, it may contribute to post- operative muscle wasting, a clear risk to frail patients and a potential impediment to rehabilitation in all pa- tients.29 A group of Scottish researchers studied whether providing usable energy in the form of preoperative carbohydrate-rich beverages could protect against post- operative muscle loss.29 Investigators randomly assigned 65 patients, who’d been admitted for major elective abdominal surgery, to receive 800 mL of either a pla- cebo drink (n = 34) or a carbohydrate-rich drink (n = 31) 12 hours before surgery and an additional 400 mL of the assigned beverage two to three hours before anesthesia induction. Loss of muscle mass, indicated by reduced arm muscle circumference, was significantly greater in the placebo group than in the carbohydrate group.

The benefits of preoperative carbohydrate loading Some of the science behind the practice.

• establish benchmarks to increase the number of patients instructed to have clear liquids until two hours before surgery.

• use the electronic health record as a tracking tool. • employ decision support tools to remind clinicians

of evidence-based fasting guidelines and help them identify the patients to whom they apply.

• provide patients with both verbal and written preoperative fasting instructions, specifying the scheduled time of surgery and the times to stop consuming solids, full liquids (describe and give examples), and clear liquids (describe and give ex- amples).

• confirm that patients understand preoperative instructions by asking them to repeat them back.

Efforts must be ongoing and evaluated for effective- ness. Quality improvement projects that track patients’ preoperative fasting instructions and actual fasting du- rations can be used to identify health care providers whose instructions aren’t evidence based. Focus qual- ity improvement efforts on patients scheduled for late morning or early afternoon surgery, ensuring that they’re told to have clear liquids or a light breakfast on the morning of their surgery or procedure. These patients are at greatest risk for discomfort and the adverse ef- fects of prolonged fasting. If a surgery or procedure is delayed, offer the patient clear liquids.

RECOMMENDATIONS FOR RESEARCH Current preoperative fasting guidelines are recom- mended only for healthy patients undergoing elective procedures involving anesthesia (general or regional), sedation, or analgesia.3-5 More research is needed to de- termine optimal practices for other patient popula- tions, such as those undergoing gastrointestinal surgery and overweight or obese patients.11 Studies conducted outside the United States have found that patients hav- ing elective gastrointestinal surgery, including colo- rectal surgery, are at no greater risk for aspiration than are other patients28, 29, 36 and that gastric emptying of clear liquids is not delayed in obese patients.42-44 Other potential areas of investigation include the safety and efficacy of clear liquids for presurgical patients with dia betes or gastroesophageal reflux disease; the effects of clear liquids on intraoperative and postoperative fluid balance; and the effects of carbohydrate-rich clear liquids on preoperative care and postoperative recov- ery.11 ▼

Jeannette T. Crenshaw is a clinical assistant professor and a mem- ber of the graduate faculty for the master’s in nursing administra- tion program at the University of Texas at Arlington College of Nursing. She is also a family educator at Texas Health Presbyterian

the Society of Academic and Research Surgery, the Renal Association, the Intensive Care Society,37 and the Scandinavian Society of Anaesthesiology and In- tensive Care Medicine11 have all endorsed guidelines that recommend providing a carbohydrate-rich clear beverage two to three hours before surgery, in addi- tion to other clear liquids.

REASONS FOR RESISTANCE Restrictive preoperative fasting instructions are slow to change for a number of reasons. Some U.S. health care providers may be unaware of the ASA guidelines and the numerous studies supporting liberalized preop- erative guidelines.38 Others may have an unwarranted fear of pulmonary aspiration risk in healthy patients undergoing elective procedures and false perceptions that fasting from midnight is safer than not and that in- travenous fluids sufficiently compensate for prolonged fasting.8, 10, 20 Some clinicians believe that patients would be confused by instructions specifying different fast- ing durations for solids, liquids, and clear liquids,39 or that implementing individualized instructions would require more time and personnel than relying on the single instruction, “npo after midnight.”40 Lengthy preoperative fasts are also commonly perceived as of- fering greater flexibility in surgical scheduling (the ra- tionale being that if a cancellation occurs, a patient who’s been fasting for a longer period can be safely moved to an earlier spot on the surgery schedule).12, 40 The likelihood of schedule variation, however, tends to be exaggerated.41 Two studies found that fewer than 10% of surgeries moved to an earlier time slot, starting an average of 33 minutes early in one1 and 56 minutes early in the other.2 In a prospective study of 5,420 con- secutive patients scheduled for surgery 15 weeks before or 15 weeks after liberalized fasting instructions were implemented, there were no surgery cancellations and there was no difference in the incidence of surgical de- lays because of nonadherence to fasting instructions.39

CAMPAIGN FOR CHANGE Education alone cannot overcome the complex and multifactorial barriers to implementing evidence- based guidelines. Liberalizing preoperative fasting prac- tices requires nothing short of a campaign by nurses, surgeons, anesthesiologists, and other health care pro- fessionals to inform colleagues and patients about the current guidelines; to encourage colleagues and pa- tients to discuss the guidelines and supporting clini- cal data; and, ultimately, to help their facilities revise protocols and procedures in accordance with current evidence.

Such revisions require clinicians to • develop preoperative order sets that include the

option of “clear liquids until _______” and “con- sume _______ ounces of the carbohydrate-rich clear liquid beverage _______ at the following time: _______.”

42 AJN ! October 2011 ! Vol. 111, No. 10 ajnonline.com

For 62 additional continuing nursing educa- tion articles on surgery topics, go to www. nursingcenter.com/ce.

21. Eriksson LI, Sandin R. Fasting guidelines in different coun- tries. Acta Anaesthesiol Scand 1996;40(8 Pt 2):971-4.

22. Rex DK, et al. American College of Gastroenterology guide- lines for colorectal cancer screening 2009 [corrected]. Am J Gastroenterol 2009;104(3):739-50.

23. Melis GC, et al. A carbohydrate-rich beverage prior to sur- gery prevents surgery-induced immunodepression: a ran- domized, controlled, clinical trial. JPEN J Parenter Enteral Nutr 2006;30(1):21-6.

24. Nygren J. The metabolic effects of fasting and surgery. Best Pract Res Clin Anaesthesiol 2006;20(3):429-38.

25. Nygren J, et al. Are there any benefits from minimizing fast- ing and optimization of nutrition and fluid management for patients undergoing day surgery? Curr Opin Anaesthesiol 2007;20(6):540-4.

26. Kehlet H, Wilmore DW. Evidence-based surgical care and the evolution of fast-track surgery. Ann Surg 2008;248(2):189-98.

27. Ljungqvist O. Modulating postoperative insulin resistance by preoperative carbohydrate loading. Best Pract Res Clin Anaesthesiol 2009;23(4):401-9.

28. Hausel J, et al. A carbohydrate-rich drink reduces preopera- tive discomfort in elective surgery patients. Anesth Analg 2001;93(5):1344-50.

29. Yuill KA, et al. The administration of an oral carbohydrate- containing fluid prior to major elective upper-gastrointestinal surgery preserves skeletal muscle mass postoperatively—a randomised clinical trial. Clin Nutr 2005;24(1):32-7.

30. Ljungqvist O, et al. Modulation of post-operative insulin re- sistance by pre-operative carbohydrate loading. Proc Nutr Soc 2002;61(3):329-36.

31. Ljungqvist O, et al. Preoperative nutrition—elective surgery in the fed or the overnight fasted state. Clin Nutr 2001; 20(Suppl 1):167-71.

32. Soop M, et al. Preoperative oral carbohydrate treatment at- tenuates immediate postoperative insulin resistance. Am J Physiol Endocrinol Metab 2001;280(4):E576-E583.

33. Svanfeldt M, et al. Effect of “preoperative” oral carbohy- drate treatment on insulin action—a randomised cross-over unblinded study in healthy subjects. Clin Nutr 2005;24(5): 815-21.

34. Svanfeldt M, 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(11):1342-50.

35. Hausel J, et al. Randomized clinical trial of the effects of oral preoperative carbohydrates on postoperative nausea and vomiting after laparoscopic cholecystectomy. Br J Surg 2005;92(4):415-21.

36. Noblett SE, et al. Pre-operative oral carbohydrate loading in colorectal surgery: a randomized controlled trial. Colorectal Dis 2006;8(7):563-9.

37. Powell-Tuck J, et al. British consensus guidelines on intravenous fluid therapy for adult surgical patients. Redditch, Worcs: BAPEN: The British Association for Parenteral and Enteral Nutrition; 2011 Mar. www.bapen.org.uk/pdfs/bapen_pubs/ giftasup.pdf.

38. Bosse G, et al. The resistance to changing guidelines—what are the challenges and how to meet them. Best Pract Res Clin Anaesthesiol 2006;20(3):379-95.

39. Murphy GS, et al. The effect of a new NPO policy on oper- ating room utilization. J Clin Anesth 2000;12(1):48-51.

40. Doswell WM, et al. One size may not fit all: it’s not always possible—or appropriate—to use the ASA guidelines for preoperative fasting. Am J Nurs 2002;102(6):58, 61.

41. Chapman A. Current theory and practice: a study of pre- operative fasting. Nurs Stand 1996;10(18):33-6.

42. Harter RL, et al. A comparison of the volume and pH of gastric contents of obese and lean surgical patients. Anesth Analg 1998;86(1):147-52.

43. Horowitz M, et al. Abnormalities of gastric emptying in obese patients. Int J Obes 1983;7(5):415-21.

44. Maltby JR, et al. Drinking 300 mL of clear fluid two hours before surgery has no effect on gastric fluid volume and pH in fasting and non-fasting obese patients. Can J Anaesth 2004;51(2):111-5.

Hospital Dallas. Contact author: [email protected]. The author has disclosed no potential conflicts of interest, finan- cial or otherwise.

The author would like to thank Elizabeth H. Winslow, PhD, RN, FAAN, M. Lou Marsh, MD, ABA, and Rodney Hicks, PhD, RN, FNP, FAANP, FAAN, for reviewing earlier versions of the manuscript.

REFERENCES 1. Crenshaw JT, Winslow EH. Preoperative fasting: old habits

die hard. Am J Nurs 2002;102(5):36-44. 2. Crenshaw JT, Winslow EH. Preoperative fasting duration and

medication instruction: are we improving? AORN J 2008; 88(6):963-76.

3. American Society of Anesthesiologists Committee on Standards and Practice Parameters. Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients un- dergoing elective procedures: an updated report by the Ameri- can Society of Anesthesiologists Committee on Standards and Practice Parameters. Anesthesiology 2011;114(3):495-511.

4. American Society of Anesthesiologists Task Force on Preop- erative Fasting. Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients under- going elective procedures: a report by the American Society of Anesthesiologist Task Force on Preoperative Fasting. An- esthesiology 1999;90(3):896-905.

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

6. Braga M, et al. ESPEN Guidelines on Parenteral Nutrition: surgery. Clin Nutr 2009;28(4):378-86.