This article reviews the basics of surgical nutrition.
Malnutrition remains a common problem in surgical patients and is associated with significant morbidity and mortality. All surgical patients must undergo nutritional screening on admission to highlight malnourished or at risk patients and implement a nutritional plan. There is a strong association between malnutrition and poor clinical outcome
An interplay exists between nutritional status and illness that makes nutritional assessment and management difficult and interpretation of studies confusing.
Recent guidelines from the National Institute for Clinical Excellence (NICE), the British Association for Enteral and Parenteral Nutrition (BAPEN) and NHS Quality Improvement Scotland (NHS QlS) concerning nutritional support provide an excellent overview of malnutrition, screening tools and monitoring of nutritional support.
Nutritional requirements in health
A healthy adult requires approximately 20-25 kcal per kilogram body weight per day. The principal components of a normal diet are energy (carbohydrate and lipid), nitrogen, trace elements, minerals and vitamins.. Metabolic stress associated with sepsis, trauma or surgery increases energy requirements to 35-40 kcal per kg per day and vitamins, minerals and trace elements are required for metabolic processes and normal cellular function and must be provided for patients requiring artificial nutritional support. Such support is best given by a multidisciplinary approach with a dedicated dietician and nutrition support team.
Nutritional assessment tools
BAPEN has produced a screening tool. Malnutrition Universal Screening Tool (MUST) which is uncomplicated, reliable and reproducible Severe malnutrition can be assessed clinically as marked wasting of proximal limb muscles and pressure sores. Milder degrees of malnutrition may be unrecognised and more detailed assessments of nutritional status are requited
There is currently no single, simple and reliable technique for assessing nutritional status. There are a variety of techniques available which are briefly summarised.
Anthropometnc measurements include Body mass index (BMI), ie as body weight in kilograms divided by height in metres squared. . A BMI of less than 18.5 implies nutritional impairment and a BMI below 15 is associated with significant mortality. Unplanned weight loss of more than 10% body weight over a six month oeriod is a prognostic indicator of poor clinical outcome..
Clinical history, in particular recent weight loss, a change in oral intake, gastrointestinal symptoms and functional capacity, combined with physical signs (muscle wasting, loss of subcutaneous fat and oedema) form the basis of the Subjective Global Assessment tool.
The plasma concentrations of proteins (albumin, pre-albumin.
transferrin and retinol-binding protein) have been used to assess nutritional status but none are particularly sensitive or specific.
The Nutrition Risk Index (NRI) is an equation using weight loss and serum albumin concentration. This equation is expressed as (1.519 x albumin g/L) + 0.417 x [present weight/ usual weight x 100). If the score is > 100 the patient is well nourished, 97.5-100 demonstrated mild malnutrition, 83.5-97 5 moderate malnutrition and
The NICE guidelines recommend that nutritional support should be given to patients who have eaten little or nothing for more than 5 days, have poor absorptive capacity, high nutrient losses or have increased requirements due to catabolic processes After patients are identified as malnourished, the route and type oi nutritional support must be decided. The usual approach to estimating a patient’s nutritional requirement is to estimate the energy requirements using the basal metabolic rate (BMR) Nutrition can be delivered by oral supplements, enteral or parenteral feeding, the route depending on an individual’s requirements and surgical condition Enteral feeding has largely been regarded as superior to parenteral feeding, as it is cheaper, safer and “more physiological” but studies show this is not always the case. Both methods require quality care and positioning of the feeding tube TPN is life saving where there is intestinal failure. TPN requires a skilled support team
There are many unanswered questions about support nutrition. The general belief that this is an important support therapy.
Moyes and McKee 2008 A review of surgical nutrition . Scottish Medical Journal vol 53 pp 38-41
- Martin Eastwood