Preoperative Fasting

Review

Preoperative fasting

O. Ljungqvist1 and E. Søreide2

1Centre of Gastrointestinal Disease, Ersta Hospital and Department of Surgery, Huddinge University Hospital, Karolinska Institute, Stockholm, Sweden and 2Department of Anaesthesia and Intensive Care Medicine, Rogaland Central and University Hospital, Stavanger, Norway Correspondence to: Dr O. Ljungqvist, Centre of Gastrointestinal Disease, Ersta Hospital, PO Box 4622, SE-116 91 Stockholm, Sweden (e-mail: [email protected]) Downloaded from https://academic.oup.com/bjs/article/90/4/400/6143199 by guest on 27 September 2021

Background and methods: To avoid pulmonary aspiration, fasting after midnight has become standard in elective surgery, but recent studies have found no scientific support for this practice. Several anaesthesia societies now recommend a 2-h preoperative fast for clear fluids and a 6-h fast for solids in most elective patients. The literature supporting such fasting recommendations was reviewed. Results: The recommendations are safe and improve well-being before operation, mainly by reducing thirst. A carbohydrate-rich beverage given before anaesthesia and surgery alters metabolism from the overnight fasted to the fed state. This reduces the catabolic response (insulin resistance) after operation, which may have implications for postoperative recovery. Conclusion: Most patients having elective operations can be allowed a free intake of clear fluids up to 2 h before anaesthesia. Preoperative carbohydrates reduce postoperative insulin resistance.

Paper accepted 22 October 2002 Published online 29 January 2003 in Wiley InterScience (www.bjs.co.uk). DOI: 10.1002/bjs.4066

Introduction increasingly stricter preoperative fasting rules5. For prac- The main reason for the traditional strict rule of ‘nil by tical purposes, patients were informed not to eat or drink mouth’ from midnight of the day before operation has been anything – nil by mouth – after midnight of the day before to ensure an empty stomach at the time of anaesthesia. It operation. No distinction was made between intake of is well documented that general anaesthesia attenuates solids and fluids. the protective laryngeal reflexes and increases the risk of Over the past two decades, several authors have pulmonary aspiration in all kinds of surgical patient1–4. questioned the scientific merit of such rigid fasting The clinical picture following aspiration varies with routines. A series of studies has addressed this issue and the volume and constitution of the aspirated content3. shown that less strict guidelines can be used without 11–13 If larger chunks of food enter the tracheobronchial tree, placing the patient at risk . Several national anaesthesia airway obstruction, sudden asphyxia and death may result1; societies now recommend more liberal fasting rules in 14–16 aspiration of gastric fluids may cause bronchoconstriction respect of clear fluids (water, clear juices, coffee, tea) . and a chemical inflammation in the lower airways Recent studies also indicate that feeding patients with (pneumonitis), referred to as aspiration pneumonitis or a specially designed high-carbohydrate beverage in the Mendelson’s syndrome3,5. With increasing severity of the immediate preoperative period is not only safe, but may pulmonary reaction, the symptoms range from transient also reduce the catabolic stress response to surgery and so 17,18 wheezing and coughing to severe hypoxia, dyspnoea and enhance postoperative recovery . All this constitutes a fulminant respiratory failure1,6–9. major change to well established clinical practice. Even in the early days of the anaesthetic era it was under- stood by most that intake of solids should be avoided in the Methods immediate preoperative period. On the other hand, preoperative oral intake of calorie-containing fluids (e.g. beef tea) Over the past 10 years or so, several national societies of was actually recommended by some surgical authorities10. anaesthetists have revised their guidelines on preoperative Later studies documented anaesthesia-related aspiration fasting. These countries include, but are not limited to, pneumonitis in many surgical settings1–3,11, resulting in Norway and Sweden14,15,theUSA16, Canada19 and the

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UK20. The literature forming the basis for these changes If gastric fluid volumes that are able to induce passive was reviewed and summarized. Data assembled by one of regurgitation are extremely rare in otherwise healthy the authors (E.S.) while working on task forces for the elective patients, why has the matter received so much national anaesthesiology societies in both Norway15 and attention? One reason is that airway management problems the USA16 on this matter are also included. These processes frequently precipitate pulmonary aspiration6,8,9,33.Air included a search of Medline using appropriate search blown into the stomach, bucking and coughing may words, as well as accessing old references and textbooks to all cause episodes of gastro-oesophageal reflux. Hence, broaden the search for original references. pulmonary aspiration may happen even in patients with a low gastric fluid volume. Still, the incidence of

Pulmonary aspiration and preoperative fasting: perioperative pulmonary aspiration is extremely low and Downloaded from https://academic.oup.com/bjs/article/90/4/400/6143199 by guest on 27 September 2021 fact and ﬁction overall carries a good prognosis in elective patients6–9,33.

When the scientific basis of rigid fasting rules started to be questioned in the 1980s, it was already known From prolonged preoperative fasting to liberal fasting rules for clear fluids that gastric emptying of water and other inert, non- caloric fluids followed an extremely fast exponential curve Several randomized controlled studies11,12,28–30 and meta- in volunteers21,22 (Fig. 1). However, concern had been analyses13,16 in otherwise healthy adults scheduled for raised about the extent to which these results could be elective surgery have documented that oral intake of applied in the immediate preoperative period with its water and other clear fluids (tea, coffee, soda water, apple increased anxiety and stress5. However, neither anxiolytic and pulp-free orange juice) up to 2 h before induction of medication nor the degree of preoperative anxiolysis affects anaesthesia does not increase gastric fluid volume or acidity. gastric emptying of clear fluids or gastric fluid volume and Thus, the risk of aspiration pneumonitis should vomiting acidity in preoperative patients23,24. It seems that clinically or regurgitation occur is not increased compared with the significant delayed gastric emptying is not present in the situation in totally fasted patients. For obvious reasons, immediate preoperative period. these findings do not apply to patients with peritonitis For passive regurgitation and pulmonary aspiration to and gastrointestinal stasis. Diabetes and other medical occur during anaesthesia, a certain gastric volume must conditions affect gastric emptying, but much more so for be present; a minimum of 200 ml is probably a fair solids than for fluids34,35. estimate25–27. This contrasts with the gastric volumes Preoperative fluid intake is associated with an increased generally found in otherwise healthy elective patients. feeling of well-being, a reduced thirst and dryness of Numerous studies have reported a mean gastric fluid the mouth and, in some studies, less anxiety11,12,30,36,37. volume in the range of 10–30 ml, with 120 ml rarely Allowing habitual coffee drinkers their morning coffee exceeded irrespective of intake of clear fluids12,13,28–30. may also reduce postoperative headache due to caffeine Outliers probably represent patients with an undetected withdrawal38. gastric disorder such as functional dyspepsia, in which a fasting gastric volume of up to 200 ml can be found31,32. Fasting guidelines and solids 100 Solids Clear fluids Some authors have also considered whether preoperative fasting times for solids can be safely reduced to 2–3 h. Miller et al.39 concluded that it was appropriate to allow a light breakfast, consisting of two slices of toasted bread 50 with butter and jam, and one cup of tea, 2–3 h before anaesthesia; this was based on their finding that this regimen had no effect on gastric fluid volume. However, 10 particulate matter was found 4 h after the light breakfast Gastric content volume (%) Gastric content volume in one of their patients and the number of patients studied (10 min) 1 2 3 was small. In an ultrasonographic study of gastric emptying Time (h) after a light breakfast (one slice of white bread with Fig. 1 Gastric emptying of solids and clear fluids in healthy butter and jam, with one cup of coffee and one cup volunteers. Adapted from data in references 21 (n = 180) and 22 of pulp-free orange juice) in healthy women volunteers, (n = 4) Søreide et al.40 showed that 4 h of fasting was needed

Copyright  2003 British Journal of Surgery Society Ltd www.bjs.co.uk British Journal of Surgery 2003; 90: 400–406 Published by John Wiley & Sons Ltd 402 Preoperative fasting ž O. Ljungqvist and E. Søreide to guarantee complete emptying of solid particles. Quite ingested this close to anaesthesia and operation may in different from clear fluids, solids empty according to a some patients induce an unwanted water diuresis and linear curve (Fig. 1). Factors such as smoking, functional problems with a full urinary bladder30. Based on the well dyspepsia, psychological stress and female hormones may documented prolonged gastric emptying encountered with further prolong gastric emptying times for solids34,35,41,42. the use of opiates, it seems reasonable to stop fluid intake So, to provide a sufficient margin of safety, the fasting at least 1 h before the use of opiate premedication28. period after intake of solids should probably be not less 15,16,43,44 than 6 h . Exceptions to liberal fasting guidelines

Modern recommendations for preoperative While the new guidelines can be used safely for most Downloaded from https://academic.oup.com/bjs/article/90/4/400/6143199 by guest on 27 September 2021 fasting patients about to undergo elective anaesthesia and surgery, it is important to emphasize that strict preoperative fasting 10,43,44 Based on all the new data available, several editorials is still recommended for all those having emergency 14–16,19,20 and national anaesthesia society guidelines operations. Other situations in which the traditional fasting recommend no more than a 2-h fast for clear fluids rule should still be used include gastrointestinal obstruction (water, tea, coffee, pulp-free fruit juices) in elective patients of any form, or cancer in the upper gastrointestinal (Table 1). Importantly, this does not apply to milk or any tract. Patients with hiatus hernia have a greater risk of other fat-containing fluid. No complications associated regurgitation, but there is no clear evidence to show with new and more liberal fasting guidelines were reported that this group has slower gastric emptying or greater in a follow-up study 3 years after implementation of the residual gastric volume than other patients. Because of 45 national guidelines in Norway . this increased risk of aspiration it may be wise to use a rapid-sequence induction method5 to secure endotracheal New preoperative fasting guidelines and intubation in those with hiatus hernia. Some societies, premedication for example in Sweden, advise that these patients may need modification of the rules, while others make no The use of premedication deserves a special mention special exception. because some of the drugs commonly used may affect gastric emptying. Intake of water together with oral Metabolic aspects of preoperative fasting benzodiazepines as premedication up to 1 h before versus oral nutrition induction of anaesthesia does not increase gastric fluid volume30. Up to 150 ml water to swallow tablets has The metabolic implications have only recently been been recommended in adults15. Larger quantities of water emphasized when discussing preoperative fasting routines.

Table 1 Overview of current recommendations for elective surgery and anaesthesia given in fasting guidelines from different countries where revised recommendations have been made during the past 10 years14 – 16,19,20

Patients for Fasting time before Exclusions whom individual anaesthesia (h) from guidelines modiﬁcations Country Clear ﬂuids Solids (i.e. fast) are needed

UK 3 6 Emergency operation, – gastrointestinal disease or intake of drugs likely to slow gastric emptying Canada 2 6–8 Norway 2 6 Emergency operation Known delay in gastric emptying Sweden 2–3 Fast from midnight for Emergency operation Reﬂux, regurgitation, full stomach, solids, 4 h for yoghurt or slow gastric motility, difﬁcult clear soup airway USA 2 6 (‘light meal’) Women in labour, emergency Conditions affecting gastric operation emptying and patients with airway problems

Clear fluids are often defined as non-particulate fluids without fat. Non-human milk is often defined as a solid.

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The old rule of fasting from midnight means that Intravenous insulin and glucose given a few hours before the patient prepares for surgery – a major stress – with elective arthroplasty had a similar effect47, as did a beverage a substantial omission of food. While this has been containing a large amount of carbohydrate (12·5 per cent) considered the normal way to prepare for operation, a before colorectal surgery48 and elective hip replacement49. 16–18-h fast before any other kind of stress, such as a These data are summarized in Fig. 2. mountain hike or marathon run, would be considered an Why should insulin resistance be considered a factor unnatural way to prepare the body. The fasted state at the of clinical importance in the postoperative patient? This time of operation has recently been shown to represent an deserves some elaboration because not all surgeons are additional stress17. familiar with this particular aspect of metabolism50. Insulin

Several animal models of severe stress have shown resistance is a transient phenomenon that lasts for about Downloaded from https://academic.oup.com/bjs/article/90/4/400/6143199 by guest on 27 September 2021 that the fasted rodent (6–24-h fast) has substantially less 3 weeks after uncomplicated elective open abdominal capacity to cope with haemorrhage or endotoxaemia17.The operations51. The degree of insulin resistance is an fed animal responds to trauma with a less marked endocrine independent factor predicting the length of hospital stay50. stress response, handles glucose metabolism in a more This is probably explained by the fact that postoperative anabolic way, displays better muscle strength for several insulin resistance in many of its central aspects resembles days after the insult and shows less bacterial translocation a state of untreated type II diabetes mellitus50,52. In short, compared with the animal subjected to identical stress in glucose uptake is reduced, in part due to a lesser response by the fasted state. These findings led to studies in adults specific glucose transporters to insulin stimulation. Inside having elective operations. The animal studies indicated the cell it is mainly the pathway to glycogen formation that the availability of carbohydrates and the metabolic that is disturbed. At the same time, endogenous glucose setting of the fed state were the crucial factors for recorded production is enhanced. A recent study of a large number of improvements. Thus, when transferring these findings into patients in intensive care (most after thoracic or abdominal the clinical setting, the first studies hypothesized that surgery) showed that, if their insulin resistance was treated the carbohydrate-fed state might result in an improved using intensive insulin therapy to normalize glucose levels metabolic situation after operation. Following open upper (as opposed to giving intermittent insulin to maintain abdominal surgery, patients treated with a high-dose glucose below 12 mmol/l), both morbidity and mortality glucose infusion (5 mg per kg per min) overnight had rates were reduced, the latter by over 40 per cent53.With a reduction in postoperative insulin resistance of 50 per this in mind, it seems reasonable to suspect that the less cent compared with that in patients fasted overnight46. ‘diabetic’ the patient, the better he or she will fare.

Carbohydrate Control 20 ∗ 10

−10

−20 ∗ −30 ∗ ∗ −40

−50 Change in insulin resistance (%) −60 Cholecystectomy46 Colorectal surgery48 Arthroplasty47 Arthroplasty49

Fig. 2 Relative change in insulin resistance following different elective surgical procedures in control patients (fasted overnight before operation or treated with a placebo beverage) and patients given preoperative carbohydrate to alter metabolism (either as an infusion of 30 per cent glucose with or without insulin, or as a carbohydrate-rich beverage)46 – 49. There were six to eight patients in each group. Measurements were performed before surgery (100 per cent insulin sensitivity) and within 24 h after operation using the hyperinsulinaemic normoglycaemic clamp technique. *P < 0·05 versus control46 – 49

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Clinical effect of preoperative carbohydrate carbohydrate was most beneﬁcial, followed by placebo (water); overnight-fasted patients scored lowest. In an The main objective of preoperative carbohydrate treatment assembly of three small prospective studies containing a is to produce the change in metabolism that normally takes total of 52 patients, length of hospital stay was analysed place when breakfast is eaten. This elicits an endogenous retrospectively using a meta-analytic technique52.Patients release of insulin that turns off the overnight fasting undergoing open cholecystectomy, colorectal surgery or state of the metabolism. The easiest way to accomplish elective hip replacement, who were treated with preoper- this change is to give carbohydrate. In the preoperative ative carbohydrate, were discharged from hospital about situation, this can be effectively achieved either by giving a 20 per cent earlier than those fasted overnight. The value high-dose glucose infusion (5 mg per kg per min or more)

of preoperative carbohydrate is being evaluated further Downloaded from https://academic.oup.com/bjs/article/90/4/400/6143199 by guest on 27 September 2021 or by providing a sufficiently concentrated carbohydrate- in ongoing trials. A preliminary report from a prospec- containing beverage24,54. Thus, a carbohydrate-rich (12·5 tive double-blind placebo-controlled randomized trial of per cent) clear beverage was prepared to suit the 89 patients undergoing major abdominal surgery noted a preoperative situation, in that it contained mainly polymers trend in the same direction58. of carbohydrates to minimize the osmotic load and so reduce gastric emptying time24. Before being used in clinical studies, the gastric emptying Conclusions of the beverage was tested in healthy volunteers and in preoperative patients using isotopic studies of gastric Free intake of clear fluids up to 2 h before anaesthesia emptying. It was shown to pass through the stomach for elective operation is safe and improves subjective well- in doses of 400 ml within 90 min. As the effect remains being, primarily by reducing thirst. More recent research for about 4 h, it has also been tested in patients taking indicates that oral carbohydrate intake on the morning of 400 ml up to 2 h before intake of morphine-containing operation can improve the perioperative metabolic milieu premedication. Follow-up studies in more than 250 and reduce the surgical stress response. Evolution of ideas patients showed that the median residual gastric volume may bring us back to the Holmes’ System of Surgery was about 20 ml, which is almost exactly the same as that recommendation from 188310, in which the wisdom of found after intake of water or after an overnight fast55. keeping the stomach free from solids was pointed out, but The same mixture of carbohydrates has also been the oral intake of carbohydrate, energy-containing fluids preliminarily reported in patients about to undergo before operation was encouraged. gastroscopy56. Again, the mean volume was the same in three groups of patients: overnight fasted, after intake of 400 ml water, and after 400 ml carbohydrate solution 2 h Competing interests statement before the investigation. In this study of some 80 patients Olle Ljungqvist is the owner of a patent for a in each group, there was a total of five patients (all taking carbohydrate-containing beverage from which the pre- a beverage) with a gastric volume of more than 120 ml, the operative beverage mentioned in the article has been highest with 200 ml. In a follow-up study of 60 patients, produced. Part of the research reported in this article 200 ml was given twice, with the later intake 2 h before has been funded by grants from Royal Numico, NL, a gastroscopy. This time, the highest volume found was commercial company that holds the licence for this patent. 120 ml and the mean was about 35 ml, regardless of intake of water or carbohydrate. To date, more than 600 patients have been included in various clinical studies and there References has been no complication reported following intake of the carbohydrate-rich beverage. 1 Mendelson CL. The aspiration of stomach contents into the Further evaluation of this carbohydrate-rich preoper- lungs during obstetric anaesthesia. Am J Obstet Gynecol 1946; ative beverage has revealed that it improves subjective 52: 191–205. 2 Edwards G, Morton HJV, Pask EA, Wylie WD. Deaths well-being compared with placebo (water). While both associated with anaesthesia. A report on 1000 cases. drinks reduce preoperative thirst, the addition of carbohy- Anaesthesia 1956; 11: 194–220. drate also reduces hunger and anxiety, and improves overall 3 Bannister WK, Sattilaro AJ. Vomiting and aspiration during well-being (as measured by 12 variables including pain, anesthesia. Anesthesiology 1962; 23: 251–264. 55 fatigue and fitness) . In addition, postoperative subjective 4 Marshall BM, Gordon RA. Vomiting, regurgitation, and well-being has also been scored in patients undergoing col- aspiration in anaesthesia, II. Can Anaesth Soc J 1958; 5: orectal surgery, and preliminary results presented57.Again, 439–447.

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Copyright  2003 British Journal of Surgery Society Ltd www.bjs.co.uk British Journal of Surgery 2003; 90: 400–406 Published by John Wiley & Sons Ltd