Core Topics in General & Emergency Surgery: Companion to Specialist Surgical Practice (81 page)
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Authors: Simon Paterson-Brown MBBS MPhil MS FRCS
Patients receiving nutritional support should be monitored by accurate recording of fluid balance and daily weighing. Daily intake of calories and nitrogen should be documented. Biochemical assessments include daily measurements of renal and liver function, with twice-weekly checks of phosphate, calcium, magnesium, albumin and protein levels, and haematological indices (haemoglobin, white blood cell count, haematocrit), until the patient is stabilised. Then, weekly or fortnightly measurements are necessary. Patients receiving PN require urinalysis daily initially in case glycosuria occurs, as this induces further fluid and electrolyte losses. If glycosuria occurs, it may be necessary to commence intravenous insulin on a sliding scale with hourly blood glucose monitoring. It is important to note that if the PN fluid is stopped, insulin requirements will reduce immediately; it is safest to discontinue the insulin at the same time as the PN, reviewing the sliding scale with a view to giving intravenous glucose if required.
Routes of access (enteral or parenteral) should be regularly examined to ensure that the catheter is correctly positioned and mechanically satisfactory.
When feeding is prolonged, other assessments, e.g. muscle function, nitrogen balance, measurement of trace elements and vitamins, may be performed regularly to ascertain patient progress (see nutritional assessment section above).
It is clear that for optimal provision of nutritional support, a multidisciplinary nutritional support team is required. This may comprise a clinician with a special interest in nutritional support and understanding of metabolic pathways, a biochemist, a pharmacist, a dietician and a nursing specialist.
The provision of nutritional support by such a team results in the most cost-effective use of nutritional support and the least risk of infective, metabolic and feeding-line complications.
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Nutritional support in the perioperative period
There is debate as to which patients require preoperative and/or postoperative nutritional support. Many studies have evaluated the effects of nutritional support in the perioperative period; clinical benefit with supplemental nutrition has not been a consistent finding. This may be because the studies were small, with many different end-points (e.g. morbidity, mortality), frequently without proper randomisation or allowance for malnutrition prior to the study commencing.
A meta-analysis has examined 27 randomised controlled trials (almost 3000 patients) of nutritional support in the perioperative period.
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The results are important and provide a basis for the rational use of nutritional support in this situation. The key findings are detailed in
Table 17.1
. When PN was given in the preoperative period there was a reduction in complication rates (relative risk 0.52, 95% confidence interval (CI) 0.30–0.91) in malnourished patients but not when nutritional state was adequate. However, there was no difference in mortality. Analysis of patients in the postoperative period indicated no reduction in complications (relative risk 1.08, 95% CI 0.81–1.43) or mortality in patients receiving PN. Subgroup analyses indicated that nutritional support in the preoperative period be considered for:
Table 17.1
Effect of perioperative nutritional support on morbidity and mortality in surgical patients
| Complications (RR and 95% CI) | Mortality (RR and 95% CI) | |
| Malnourished patients | 0.53 (0.30–0.91) | 1.13 (0.75–1.71) |
| Adequate nutrition | 0.95 (0.75–1.21) | 0.90 (0.66–1.2) |
| Preoperative TPN | 0.70 (0.52–0.95) | 0.85 (0.6–1.20) |
| Postoperative TPN | 1.01 (0.70–1.46) | 1.08 (0.73–1.58) |
| Overall effects | 0.81 (0.65–1.01) | 0.97 (0.76–1.24) |
CI, confidence interval; RR, relative risk; TPN, total parenteral nutrition.
those with a serum albumin < 30–32 g/L;
patients with a weight loss of 15% or more, associated with impairment of physiological function;
patients with a nutrition (prognostic) risk index < 83.5.
Nutritional support should be given to malnourished patients for at least 7–10 days preoperatively where possible to reduce postoperative morbidity.
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Nutritional support in the postoperative period should be considered for:
patients in whom it is anticipated that normal oral intake is unlikely for 7 days or more after surgery;
those with severe sepsis or burns;
those with enterocutaneous fistulas (particularly if high output);
patients who have lost 15% or more of their usual weight prior to surgery being undertaken.
As discussed, the enteral route is the preferred route except in specific circumstances where not possible (e.g. intestinal obstruction, ileus, intestinal ischaemia, etc.) or used in combination with PN if the nutritional requirements cannot be provided by the enteral route alone. A recent analysis of
The ESPEN guidance is summarised as follows.
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Patients who should receive perioperative nutritional support:
Those expected not to eat for > 7 days perioperatively.
Those unable to have an oral intake > 60% of their recommended intake for > 10 days.
Patients who should receive preoperative enteral nutritional support:
Preoperative nutritional support should be given for 10–14 days to those with ‘severe’ nutritional risk, which is defined as either a BMI < 18.5 kg/m
2
, recent weight loss of 10–15% in the previous 6 months or serum albumin < 30 g/L (with no evidence of renal or hepatic failure). For such patients it is recommended that surgery should be delayed if possible to allow nutritional support.
Patients who should receive postoperative nutritional support:
Early enteral nutritional feeding (i.e. < 24 hours after surgery) is recommended for patients who have undergone upper gastrointestinal anastomosis with the tip of a feeding tube placed distal to the anastomosis.
studies of enteral nutrition given to patients in the perioperative period has been carried out and published as European Society of Parenteral and Enteral Nutrition (ESPEN) guidelines
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(
www.espen.org/Education/documents/ENSurgery.pdf
).
Chapter 8
)
Severe pancreatitis produces a major catabolic stress with rapid loss of muscle proteins. The daily nitrogen requirements of such patients are high, reaching 1.2–2.0 g protein/kg body weight (0.2–0.3 g of nitrogen/kg). Daily energy requirements also increase with disease severity to be 28–35 kcal/kg. Previously, patients with pancreatitis were fasted in order to avoid pancreatic stimulation. However, views have now changed
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and a recent systematic review
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has shown that patients with acute severe pancreatitis should commence enteral support early (within 5 days). This resulted in better outcomes with reduced infectious complications and hospital stay, but without effect on mortality.
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–
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Patients with severe acute pancreatitis should commence early enteral nutritional support as this is associated with a better outcome.
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A significant number of patients with Crohn's disease and ulcerative colitis become malnourished. The reasons for this include decreased nutrient intake, malabsorption by the small intestine (decreased length, bacterial overgrowth, protein-losing enteropathy) and increased calorie/nitrogen requirements in those with coexistent sepsis. There may be deficiencies of specific vitamins and trace elements.
Nutritional support, therefore, may have different roles: (i) to provide nutritional requirements and correct nutritional deficiencies the patient may have; (ii) the possibility that provision of PN with bowel rest in Crohn's disease may be therapeutically beneficial. The results of studies addressing this latter point are inconclusive,
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suggesting that PN itself does not have a therapeutic effect in inflammatory bowel disease. Furthermore, there is evidence showing that enteral nutrition is as effective as PN in these patients.
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This has the added benefits of maintaining gut mucosa integrity in addition to stimulating production of gut hormones necessary for function.
Nutritional support has an important role to play in management of patients with enterocutaneous fistulas as up to 50% are malnourished. The importance of adequate nutritional support was demonstrated by Chapman et al.,
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who found that if patients with fistulas received nutritional support with PN and enteral feeding (> 3000 kcal (12.6 MJ) daily), spontaneous fistula healing with a reduced mortality occurred compared with patients with fistulas receiving less than 1000 kcal (4.1 MJ) daily. The management of such patients commences with correction of fluid and electrolyte deficits and elimination of septic foci. Nutritional support is required to correct any nutritional deficits and provides maintenance requirements when the patient is stabilised. Whether PN or enteral nutrition is more effective is unknown. Other techniques for providing nutritional support have included collecting the intestinal output from the proximal end of the fistula and re-infusing it into the distal part of the small intestine or by giving enteral nutrition via the fistula. If the fistula output is low, enteral nutritional support should be considered because of the benefits.
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Enteral nutrition has theoretical benefits due to its effects on gut mucosa and case series have suggested that healing rates with enteral nutrition are comparable to those of parenteral nutrition.
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Major burns induce severe hypermetabolic and hypercatabolic states. There is increased skeletal muscle breakdown, nitrogen losses of 15 g daily or more, and up to a doubling of metabolic rate. In patients with burns of greater than 20% of their body surface area, nutritional support is required, orally or by nasoenteric feeding. There may be clinical benefits by introducing feeding early, and with glutamine supplementation.
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This appears to be associated with reduced infectious complications and better wound healing, and is recommended by the ESPEN guidelines.
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Glutamine supplementation should be given to patients with substantial burns to reduce their complications and improve healing. If enteral nutritional support is not possible, e.g. with gastric stasis, ileus or other coexistent injuries, parenteral nutrition is required.
Several formulae exist for calculating the protein and calorie requirements.
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However, up to 20–25 g of nitrogen per day may be required initially, with a non-protein calorie to nitrogen ratio of 100–200. Energy is provided as carbohydrate and lipids, with the calorie requirement being 35–50% as lipid.