Title: Nutritional support and the surgical patient
Key words: undernutrition, complications, complication rate, nutritional support, malnutrition, surgery, surgical, patients, depletion, wound healing, pneumonia, sepsis, cardiorespiratory failure, bed sores, pressure sores, thrombosis, food intake, BMI, triceps skinfold, sarcopenia, cancer, grip strength, nutritional status, postoperative, aspiration pneumonia, anastamotic dehiscence, paralytic ileus, oral feeding, enteral feeding, enteral nutrition, nasogastric tube, intestinal hypokinesis, jejunostomy, parenteral, perioperative, catabolic state, appetite suppression, hypermetabolic state, immune suppression, glutamine, arginine, RNA, omega-3, fatty acids, atrophy, hyperalimentation, gastrointestinal surgery, supplements, supplementation,
Date: Oct 2006
Author: Morgan, G
Nutritional support and the surgical patient
Surveys have shown that undernutrition is prevalent amongst the surgical population and is linked to higher complication rates and length of hospital stay. This review will look at how nutritional support can help to address these problems and lead to both clinical and cost-saving benefits.
Malnutrition in the surgical population
Amongst the surgical population, malnutrition can be defined as a state of energy and nutritional depletion leading to impaired wound healing, increased morbidity, and prolonged hospital stay. Postoperative complications, such as pneumonia, sepsis, cardio-respiratory failure, bed sores, thrombosis, and impaired mobilisation, are associated features. It has not proved possible to define the condition more precisely. Several biochemical parameters have been suggested but, though supported by much clinical research, they have not proved useful or cost-effective in clinical practice (Baxter 1999).
Assessments of food intake and simple anthropometric measurements of weight, BMI, and triceps skinfold thickness remain the most useful measurements of malnutrition on the ward. Various assessment protocols have been introduced, the MUST protocol (Elia 2003a) now being widely used in the UK as a practical tool for hospital staff to gauge the level of malnutrition amongst surgical patients. In addition, sarcopenia is a common accompaniment of weight loss in such groups, especially in cancer patients. Grip strength closely correlates with the degree of sarcopenia and has proved a useful adjunct in the assessment of nutritional status (Hunt 1985).
The incidence of malnutrition in surgical patients
In an early study, Studley showed postoperative mortality rates rising steeply to around 33% in cases of peptic ulcer surgery when weight loss exceeded 20% (Studley 1936). Improved surgical techniques and more precise definitions of malnutrition have subsequently allowed a more precise assessment of the size of the problem. Estimates from several surveys have put the risk of malnutrition in these patients at between 20-50%, depending on the surgical group concerned (Bistrian 1976, Hill 1977, McWhirter 1994, Stratton 2003). Postoperative complications and length of hospital stay have been related to the degree of malnutrition (Robinson 1987, Dempsey 1988). Surgical patients with a likelihood of malnutrition are three times more likely to have complications and increased mortality (Gallagher-Allred 1996).
The place of nutritional support
The fear of aspiration pneumonia and anastamotic dehiscence, complications ascribed to too early feeding in the presence of paralytic ileus, has, for many years, persuaded many surgeons to refrain from early oral or enteral feeding following abdominal surgery. However, recent reviews have concluded that, in almost all instances of major elective abdominal surgery, enteral nutrition can be instituted within the first 24 hours and is relatively well tolerated (Bengmark 1998). Nasogastric tube intubation is the preferred feeding route but, in more severe cases of intestinal hypokinesis, jejunostomy or parenteral feeding remains an option (Moore 1986, Silk 1998). Clinical considerations, and practical considerations such as cost and staff training, are the major determinants of the route of nutritional support. In clinical terms, the decision to give nutritional support perioperatively is important due to:
Surgery leads to a catabolic state with appetite suppression, reduced oral intake and weight loss. Particularly in cancer cases where weight loss and malnutrition are severe, a hypermetabolic state postoperatively can lead to nutritional compromise with elevated complication and mortality rates that frequently cannot be managed adequately by staged introduction of a hospital diet (Kern 1988, Simons 1999).
2. Immune suppression postoperatively with an inflammatory response and activation of an acute phase response.
Much laboratory and clinical research attests to a state of hyperinflammation and immune suppression in the postoperative phase (Bozzetti 1999, Grimble 2001 for review). Many trials have now been conducted looking at the effect of immunomodulating agents, such as glutamine, arginine, RNA and omega-3 fatty acids on modulating the response, particularly following abdominal surgery. A comprehensive meta-analysis of these trials (Marik 2001) has shown significant reductions in sepsis, other complications, hospital stay and mortality. Adequate preoperative and early postoperative enteral nutrition appears to be more beneficial in this group (Senkal 1997, Braga 1999).
3. Disuse atrophy of the intestinal mucosa with associated increased gut permeability and the risk of gut translocation and sepsis (Jolliet 1999 for review)
Although there are associated risks of overfeeding, notably aspiration pneumonia, line infections, and sepsis, when instituted appropriately there are clear benefits to nutritional support. A recent review and meta- analysis of 11 studies of early postoperative enteral nutrition, commencing within 24 hours of elective gastrointestinal surgery, showed the risk of all infections and the length of hospital stay to be reduced (Lewis 2001). Risk reductions in anastamotic dehiscence, wound infection, intra-abdominal abscess, pneumonia and mortality were also noted but failed to reach statistical significance. The data is incomplete and there are methodological problems, such as low powered trials or problems in reaching nutritional targets, that have led to negative results (Heslin 1997, Watters 1997). Improved TPN methodology has meant that line infections, blood sugar, fluid and electrolyte control, and hyperalimentation are no longer restrictive (Woodcock 2001, Elia 2003b).
Although routine parenteral nutrition preoperatively for surgical cases is to be discouraged (The Veteran Affairs TPN Study 1991), its use in the severely ill with prolonged bowel inertia has led to significant reductions in morbidity and mortality. Using all forms of perioperative nutrition, non-infective complications of surgery have been reduced from 40% to 5-20% in the more severely malnourished groups (Elia 2003b).
In summary, in elective gastrointestinal surgery, and particularly when properly implemented in the malnourished and cancer groups, selective nutritional support has been shown to lead to lower rates of postoperative morbidity and mortality.
The efficacy and cost-effectiveness of nutritional support
In spite of the above evidence, concerns are still expressed over the safety of nutritional support. In a review (Silk 1998), it has been stressed that it should be reserved for cases of abdominal and other surgery where studies have shown benefit and should be given according to well-defined protocols. In the least severe case, oral nutritional supplements have produced encouraging results when combined with a food diet. Energy input and weight has increased, grip strength improved, and sepsis and hospital stay reduced (Keele 1997, Delmi 1990, Rana 1992). Early postoperative treatment appears to be most effective. Though improved weight gains are apparent with home nutrition postoperatively, there is no evidence that this improves postoperative complications and morbidity (Jensen 1997, Keele 1997, Walters 1997). For more severe cases enteral nutrition is to be preferred, or parenteral nutrition where there is intestinal failure. The use of percutaneous endoscopic gastrostomies (PEG) is now becoming more routine in the treatment of, for example, upper abdominal obstruction. Trained staff are integral to the provision of a home-based nutritional programme for these patients.
Effective nutritional supplementation has been shown to lead to shorter stays in hospital following surgery (Robinson 1987, Reilly 1998, Stratton 2003). Using the MUST criteria for malnutrition, Stratton (Stratton 2003) computed the mean length of stay to be 2 days longer for malnourished surgical patients. The cost to the NHS at 1992 prices has been computed to be some £266 million per annum (Lennard-Jones 1992). With present financial constraints on the health services, the provision of an efficient and effective nutritional support service with a strong emphasis on care in the community is thus of paramount importance. The founding of nutritional support teams based in hospitals has led to substantial improvements in clinical outcome and cost-savings (Elia 1993).
Improved surgical techniques, combined with better postoperative care, have led to enhanced clinical outcomes for surgical patients. The use of nutritional support for selected gastrointestinal and other surgical groups helps to address the malnutrition-related postoperative complications frequently seen in these groups. The provision of adequately trained and funded teams will help to reduce the high levels of morbidity and mortality traditionally seen in these groups and render both hospital and home-based nutritional support more cost-effective.
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