During the catabolic phase of illness (following trauma, surgery or during sepsis/infection) the metabolic rate is increased and energy requirements have been shown to be elevated by between 5% and 60%, depending on the severity of the response (Barak et al., 2002 and Long et al., 1979). While the provision of nutritional support during this time is important, it cannot prevent the metabolic changes seen. The aim should be to provide balanced nutritional support to reduce the losses of lean body mass, while avoiding the negative effects of overfeeding.

Malnourished individuals who continue to have no/inadequate nutritional intakes are at risk of metabolic complications when re-fed (commonly referred to as re-feeding syndrome). Clinical and biochemical abnormalities – acute micronutrient deficiencies (especially B vitamins), fluid and electrolyte imbalance (hypophosphataemia, hypokalaemia, hypomagnesaemia) and disturbances of organ function (cardiac failure) – may occur when excessive, imbalanced nutritional support is given to malnourished patients. It is important to introduce nutritional support slowly (whether it is given via the oral, enteral or parenteral nutrition route) alongside biochemical monitoring (NICE, 2006).

After the catabolic phase of illness, the individual enters the recovery phase, when they are no longer hypermetabolic and can utilize additional nutrients. In this stage it is appropriate to increase intake to restore the body’s stores of lean and fat mass.

Protein is made up of chains of amino acids, and makes up the main structural and functional components of all cells in the body. Proteins within the body are continuously being broken down and resynthesized and this balance is altered by trauma or surgery. During the catabolic phases of illness, although protein loss may be reduced by the provision of nutrition, it cannot be reversed. Attempts to restore lean body (muscle) mass and improve nitrogen balance by giving large amounts of protein and energy may result in complications such as hyperglycaemia, and have been shown to have no additional benefit over giving standard amounts (Ishibashi et al, 1998).

Levels of blood proteins such as albumin/pre-albumin were historically used as a marker of malnutrition. Albumin levels often fall post-surgery (Cuthbertson and Tompsett, 1935) or during trauma or infection when inflammatory markers (such as white cell count and C-reactive protein) are raised (Fleck et al, 1985). Severely malnourished patients such as those with anorexia nervosa often maintain a normal albumin level (McCain et al, 1993). Therefore, in surgical patients a low albumin level is more likely to indicate severity of illness than simply malnutrition. Whereas patients should not be referred for nutritional support solely due to a low albumin level, it should be recognised that severely ill patients are more unlikely to meet their full nutritional needs via the normal oral route.

Nutritional support should provide a balance of macronutrients (fat, carbohydrate and protein). Requirements at different stages of illness are summarized in Table 6.1.

Water is an essential component of body tissues, constituting approximately 50–70% of the total body weight, within cells or as extracellular fluid. Water is ingested as fluid drunk and in food eaten, or provided by intravenous fluids, and is excreted in urine, faeces, sweat from the skin and is exhaled from the lungs.

The electrolytes sodium, potassium and chloride are essential to maintain the correct composition of body fluids. Potassium occurs mainly within the cells, with only 2% of the total body stores existing in the extracellular fluids. Increases in plasma potassium levels may occur when tissues are destroyed and potassium is released from the cells. A fall in plasma potassium usually occurs when losses from the body are increased, e.g. in diarrhoea, increased losses from the kidney or when re-feeding malnourished individuals (as described above).

It is common after surgical intervention for a patient to be given intravenous (IV) fluids. Although large volumes may be required to restore blood volume during surgery, the excessive provision of IV fluids postoperatively (particularly those high in sodium, such as 0.9% saline) has been shown to increase complications (Brandstrup et al, 2003). Postoperative fluid overload can result in oedema and delay in the return of normal gastrointestinal function (gastric emptying and passing of bowel motions) (Lobo et al, 2002).

In other situations, sodium depletion can occur, if losses are not adequately replaced. Sodium (and fluid) requirements are increased during excessive sweating (due to pyrexia for example), or if there are losses from the small bowel (small bowel fistula, ileostomy, or profuse diarrhoea).

It is vital that a patient’s fluid and electrolyte needs are assessed on an individual basis, and the nurse has a key role in ensuring that IV fluids are not used indiscriminately. Detailed fluid balance charts should be kept, although these do not take into account insensible losses (such as sweat). Regular (daily) measurements of body weight are the best clinical measure of fluid balance but are often not routinely undertaken on hospital patients.

Adequate quantities of vitamins and minerals are essential for optimal functioning of the body. Daily requirements for healthy individuals are often reported as reference nutrient intake (RNI) (Department of Health, 1991).

In the surgical patient, absorption of vitamins and minerals may be reduced by malabsorption, poor gastrointestinal motility, or loss of intestinal mucosa. Loss of vitamins from the body, particularly water-soluble vitamins, may be increased due to diarrhoea or drainage of gastric contents via a nasogastric tube (Shenkin, 1995). Certain population groups may be at greater risk of deficiency of these nutrients, particularly the elderly (Finch et al, 1998).

Many vitamins and minerals have a role to play in the wound healing process. Vitamin C (ascorbic acid) is essential for the formation of collagen, and wound dehiscence has been reported in individuals depleted in vitamin C. The RNI for vitamin C is 40 mg/day (Department of Health, 1991), although intakes of 60–200 mg have been suggested in wound healing (Todorovic, 2002). Historically, vitamin C has been given to all patients with large wounds; however, there is no evidence to support blanket supplementation (Ter Rite et al, 2001).

Vitamin A (retinol) is necessary for the formation of collagen and enhances granulation and epithelialization of healing wounds. Vitamin A deficiency is rare in western countries, and care must be taken to avoid exceeding reference nutrient intakes, because of the toxicity (Department of Health, 1991).

Vitamin K is necessary for clotting of the blood. Requirements are not known to be increased in the surgical patient but the action of vitamin K may be altered by drugs such as anticoagulants (warfarin), which block the recycling of vitamin K, and broad-spectrum antibiotics, which destroy the bacteria responsible for producing menaquinones, which have vitamin K activity (British Medical Association and Royal Pharmaceutical Society of Great Britain, 2004).

Zinc is necessary for division of cells within the body. Rapid loss of lean body mass – i.e. muscle – encourages loss of zinc from the body (Pichard and Jeejeebhoy, 1994). Zinc deficiency has been associated with delayed wound healing and reduced wound strength (Andrews and Gallagher-Allred, 1999), although a review concluded that zinc supplementation is only of benefit in those with low serum zinc levels (Wilkinson and Hawke, 2003).

Patients should be taking a minimum of 100% of the RNI of micronutrients, and, whenever possible, this should be met by intake of food and fluids. Where dietary intake is inadequate or requirements are raised, a multivitamin and mineral preparation may be necessary to ensure an adequate intake. The use of single nutrient supplements should be avoided where possible, due to potential problems with toxicity, drug nutrient interactions and competing bioavailability, but may be required to correct confirmed deficiencies. Generally there is no benefit to be gained from excess or ‘mega-doses’ of vitamins or minerals. Guidance on safe upper levels for vitamins and minerals is given by the Food Standards Agency (FSA, 2003).

If the shortfall in nutrients cannot be met by food alone, oral nutritional supplements can be used. They have a role in the treatment of surgical patients, but should only be used once food intake has been properly assessed and nutritional goals set. A dietitian’s input will ensure the most appropriate products are used.

The benefits of oral nutritional supplements in both hospital and community settings have been shown, improving energy and protein intakes, body composition, function and clinical outcome (Stratton et al, 2003). There are many steps that can be taken to help with patient concordance, and ensure that the potential benefit from the supplement is realized. Many of the supplement drinks taste much better when chilled, so giving them to patients from the fridge, when they are ready to drink them is best. Patients may need assistance with opening cartons, and they should be given out at an appropriate time – between meals is usually best. It also helps to present the supplement positively, explaining about its contents and how it will help recovery. Many patients find that they prefer to sip these slowly over a period of time (check manufacturer’s guidance on how long they can be left at ward temperature for).