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Randomised trial of safety and efficacy of immediate postoperative enteral feeding in patients undergoing gastrointestinal resection

^a Departments of Cardiothoracic Surgery and Surgery, University College London Medical School, Middlesex Hospital, London W1N 8AA, ^b Department of Medicine, University College London Medical School, Whittington Hospital, London N19 5NF, ^c Bloomsbury Institute of Intensive Care Medicine, Department of Medicine, University College London Medical School, Rayne Institute Building, London WC1E 6JJ

Correspondence to: Dr Singer.

Abstract

Objectives: To assess whether immediate postoperative enteral feeding in patients who have undergone gastrointestinal resection is safe and effective.
Design: Randomised trial of immediate postoperative enteral feeding through a nasojejunal tube v conventional postoperative intravenous fluids until the reintroduction of normal diet.
Setting: Teaching hospitals in London.
Subjects: 30 patients under the care of the participating consultant surgeon who were undergoing elective laparotomies with a view to gastrointestinal resection for quiescent, chronic gastrointestinal disease. Two patients did not proceed to resection.
Main outcome measures: Nutritional state, nutritional intake and nitrogen balance, gut mucosal permeability measured by lactulose-mannitol differential sugar absorption test, complications, and outcome.
Results: Successful immediate enteral feeding was established in all 14 patients, with a mean (SD) daily intake of 6.78 (1.57) MJ (1622 (375) kcal before reintroduction of oral diet compared with 1.58 (0.14) MJ (377 (34) kcal) for those on intravenous fluids (P<0.0001). Urinary nitrogen balance on the first postoperative day was negative in those on intravenous fluids but positive in all 14 enterally fed patients (mean (SD) -13.2 (11.6) g v 5.3 (2.7) g; P<0.005). There was no difference by day 5. There was no change in gut mucosal permeability in the enterally fed group but a significant increase from the test ratios seen before the operation in those on intravenous fluids (0.11 (0.06) v 0.15 (0.12); P<0.005). There were also fewer postoperative complications in the enterally fed group (P<0.005).
Conclusions: Immediate postoperative enteral feeding in patients undergoing intestinal resection seems to be safe, prevents an increase in gut mucosal permeability, and produces a positive nitrogen balance.

Introduction

Malnutrition predisposes to postoperative complications: increased incidence of infection¹ and prolonged hospital stay.² Malnourished patients undergoing major surgery have improved outcome with total parenteral nutrition,³ but this has complications related to site of venous access, metabolic disturbances,⁴ and prolonged postoperative ileus.⁵

Conventional treatment after bowel resection entails starvation with administration of intravenous fluids until passage of flatus. Postoperative gastric stasis causes nausea and vomiting thus inhibiting oral intake, but it has been shown that small bowel function continues.⁶ Early enteral feeding improves the out-come in patients with trauma^{7 8} and burns,^{9 10} though few studies have examined its use after bowel resection. Schroeder et al found improved wound healing in an enterally fed group after bowel resection but calculated that dietary requirements were not fulfilled until the introduction of normal diet.¹¹

We undertook a pilot study in patients undergoing bowel resection by comparing conventional management with immediate enteral feeding in which protein calorie requirements were met within 8 to 12 hours postoperatively. Assessment was made of safety, nutritional state, clinical outcome, and effects on gut mucosal permeability.

Subjects and methods

Patients undergoing intestinal resection were considered. Exclusion criteria were emergencies and allergy or intolerance to the constituents of the feed. Fully informed consent was obtained and approval obtained from the hospital ethics committee.

Record was made of the type of surgery, postoperative drugs (opiates and antiemetics), ventilation or renal replacement, time to flatus and full feeding, daily nutritional intake, complications, sepsis score,¹² and clinical outcome.

Nutritional state was assessed preoperatively, on day 1 postoperatively, and at five day intervals until discharge. Mid-arm muscle circumference, triceps skinfold thickness, handgrip dynamometry,¹³ body weight, serum albumin concentration, and 24 hour urinary nitrogen balance were measured.

A differential sugar absorption test¹⁴ (5 g lactulose, 2 g mannitol, and 22.3 g glucose in 100 ml of water) was given preoperatively and on day 5 postoperatively. A urine sample was taken 12 to 24 hours later and immediately frozen. Analysis was performed by using gas liquid chromatography.

After we had obtained informed consent the patients were randomly allocated (by closed envelope) to receive feeding or to be managed conventionally. Fed patients had a double lumen nasojejunal tube (Medicina, Manchester) passed perioperatively, with the surgeon verifying the position. The conventionally treated patients received intravenous fluids with nil by mouth until passage of flatus.

Feeding was started on returning from the operating theatre by using standard isocaloric feed (Fresubin, Fresenius, Cheshire). Energy and water requirements were calculated from the weight of the patient, and a mixture of Fresubin and water provided the full basic fluid requirements (35 ml/kg body weight/day). Initially feeding was at 25 ml an hour and was increased by 25 ml four hourly until the target volume was reached, at which point intravenous fluids were stopped. Distension or pain would lead to cessation of the feed. Oral fluids started on passage of flatus and increased to normal diet over 48 hours. Intravenous fluids and enteral feeding were stopped with the introduction of diet.

Data are presented as means (SD) and were analysed by Student's two tailed t test. A P value less than 0.05 was considered significant. Where there were significant differences between the two treatment groups the 95% confidence interval for that difference is shown.

Results

Thirty patients were randomised. Two patients did not proceed to resection, and their data were not included. Fourteen patients were randomised to enteral feeding. Their mean (SD) age was 60.1 (7.5) years; five were women; and the mean body mass index (weight (kg)/(height (m)²)) was 24.14 (4.31). They were all successfully fed with no tube blockages or cessation of feed. The corresponding figures for the 14 patients randomised to conventional feeding were 51.1 (8.2) years; six women; and 22.05 (3.87) for body mass index.

Table 1 summarises all the results. The mean intake of energy (6.78 (1.57) v 1.58 (0.14) MJ/day (1622 (375) v 377 (34) kcal/day); 95% confidence interval for difference -6.11 to -4.30 (-1462 to -1028); P<0.001) and protein (60.6 (3.8) v 0.8 (0.1) g/day; -68.1 to -51.5; P<0.001) was significantly higher in the enterally fed patients. The nitrogen balance was significantly higher in the enterally fed patients on only the first postoperative day (5.3 (0.7) v -13.2 (3.1) g; -25 to -11.6 g; P<0.005). The lactulose:mannitol absorption ratio was numerically higher in the enterally fed patients (0.15 (0.12) v 0.11 (0.06) preoperatively, but this difference did not reach significance. Also the apparently lower preoperative v postoperative lactulose:mannitol in the enterally fed patients was not significantly different. Enteral feeding (0.1 (0.03)), however, resulted in a significant attenuation in gut permeability when compared with conventional feeding (0.5 (0.26); 0.1 to 0.6; P<0.05).

Table 1--Clinical characteristics of patients undergoing
gastrointestinal resection according to method of postoperative
nutrition. Figures are means (SD) unless otherwise
stated
-------------------------------------------------------------------------------------
                                                 Enteral            Conventional
                                                 feeding              feeding
Detail                                           (n=14)               (n=14)
-------------------------------------------------------------------------------------
Investigation data
Energy/day:
  MJ                                            6.8 (1.57)*        1.58 (0.14)
  kcal                                         1622 (375)*          377 (34)
Protein/day (g)                                60.6 (14.4)          0.8 (0.2)
Nitrogen balance:
  Preoperative                                  1.5 (1.9)           1.7 (2.2)
  Postoperative:
    Day 1                                       5.3 (2.7)*        -13.2 (11.6)
    Day 5                                       1.2 (1.2)           1.0 (0.8)
Lactulose:mannitol ratio:
  Preoperative                                 0.15 (0.12)         0.11 (0.06)
  Postoperative                                 0.1 (0.03)          0.5 (0.26)*

Clinical outcome
No of patients with:
  Nausea/vomiting                                  1                    7
  Distension                                       2                    4
  Diarrhoea                                        0                    1
  Bleeding duodenal ulcer                          0                    1
  Infection (wound, urinary)+                      0                    3
Length of stay (days)                           9.8 (6.6)            9.3 (2.8)
Days to oral intake                                6                    6
Days to passage of flatus                          6                    6
Days to defaecation                                4                    5

Nutritional data at day 5 after operation
Loss in mid-arm circumference (cm)              0.3 (0.1)            0.4 (0.1)
Loss in skinfold thickness (cm)                0.07 (0.02)         0.005 (0.01)
Drop in handgrip strength (kg)                  6.7 (3.2)            9.6 (2.1)
Weight loss (kg)                                0.5 (0.2)            1.8 (0.3)
Drop in serum albumin (g/l)                    11.6 (2.5)           11.5 (2.3)
-------------------------------------------------------------------------------------
*P<0.005.
+One patient in conventional treatment group died with sepsis score
>/=20.

There appeared to be fewer complications among the enterally fed group, but overall clinical outcomes did not differ significantly. Also the nutritional data were similar between the two groups.

Discussion

In this study feeding was started two to three hours after surgery and continued until normal diet was possible. Full feeding was achieved quickly and was well tolerated with no excessive distension. No patients progressed to postoperative total parenteral nutrition. The functional integrity of the bowel mucosa was assessed by a differential sugar absorption test. Mannitol is absorbed transcellularly and lactulose paracellularly (40 to 100-fold lower absorption than mannitol). Both sugars are excreted unchanged in the urine. Increased intestinal permeability allows greater amounts of lactulose to be absorbed thus raising the urinary lactulose:mannitol ratio. This occurs in critically ill patients,¹⁴ patients with multiple trauma,¹⁵ and patients undergoing major vascular procedures.¹⁶ Our finding that immediate enteral feeding after bowel resection seems to prevent the rise in intestinal permeability suggests a protective role, whether by providing a physical barrier or via direct metabolic and nutritive effects on the intestinal mucosa remains unknown. The observed higher protein and energy intake in the enterally fed patients may have contributed to the improved gut mucosal integrity.

Total parenteral nutrition costs about £60 a day compared with enteral feeding at £12 a day and intravenous fluids at £3 a day. Postoperative enteral feeding may reduce the need for total parenteral nutrition and reduce expenditure and complications.

We conclude that immediate enteral feeding is safe and well tolerated by patients undergoing bowel resection. In addition to the considerable improvement in total calorie and protein intake there is a significant attenuation in gut mucosal permeability.

Funding: Departments of surgery and intensive care.

Conflict of interest: None.

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