The Royal Marsden Hospital Manual of Clinical Nursing Procedures - Lisa Dougherty [259]
Haemoglobin. This is often below haematological reference values in malnourished patients (men 13.5–17.5 g/dL, women 11.5–15.5 g/dL). This can be due to a number of reasons, such as loss of blood from circulation, increased destruction of red blood cells or reduced production of erythrocytes and haemoglobin, for example due to dietary deficiency of iron or folate.
Serum vitamin and mineral levels. Clinical examination of the patient may suggest a vitamin or mineral deficiency. For example, gingivitis may be due to a deficiency of vitamin C, vitamin A, niacin or riboflavin. Goitre is associated with iodine deficiency, and tremors, convulsions and behavioural disturbances may be caused by magnesium deficiency (Shenkin 2001). Serum vitamin and mineral levels are rarely measured routinely, as they are expensive and often cannot be performed by hospital laboratories.
Immunological competence. Total lymphocyte count may reflect nutritional status although levels may also be depleted with malignancy, chemotherapy, zinc deficiency, age and non-specific stress (Bodger and Heatley 2001).
If a patient is considered to be malnourished by one or more of the above methods of assessment then referral to a dietitian should be made immediately (Burnham and Barton 2001).
Methods for calculation of nutritional requirements
The body requires protein, energy, fluid and micronutrients such as vitamins, minerals and trace elements to function optimally. Nutritional requirements should be estimated for patients requiring any form of nutritional support to ensure that these needs are met.
Energy requirements may be calculated using equations such as those derived by Schofield (1985), which take into account weight, age, sex, activity level and clinical injury, for example post surgery, sepsis or ventilator dependency. An easier and more appropriate method is to use bodyweight and allowances based on the patient’s clinical condition (Table 8.4). Careful adjustments may be necessary in cases of oedema or obesity, in order to avoid overfeeding (Horgan and Stubbs 2003).
Table 8.4 Guidelines for estimation of patient’s daily energy and protein requirements (per kilogram bodyweight)
Normal Pyrexia or extreme sepsis
Energy (kcal) 25 25–35
(kJ) 105 105–146
Nitrogen (g) 0.17 (0.14–0.2) 0.2–0.3
Protein (g) 1 (0.87–1.25) 1.25–1.87
Fluid (mL) 30–35 30–35 plus 2–2.5 mL per °C in temperature above 37°C
Fluid and nitrogen (or protein) requirements can be calculated in a similar way. If additional nitrogen is being given in situations where losses are increased, for example due to trauma, GI losses or major sepsis, then additional energy intake is required to assist in promoting a nitrogen balance. Improvement in nitrogen balance is the single nutritional parameter most consistently associated with improved outcome, and the primary goal of nutrition support should be the attainment of nitrogen balance (Gidden and Shenkin 2000). Additional fluid of 500–750 mL is necessary for every 1°C rise in temperature in pyrexial patients (Thomas 2007).
Vitamin and mineral requirements calculated as detailed in the Committee on Medical Aspects of Food Policy (COMA) Report 41 on dietary reference values (COMA and DH 1991) apply to groups of healthy people and are not necessarily appropriate for those who are ill. A patient deficient in a vitamin or mineral may benefit from additional supplements to improve a condition. Macronutrient and micronutrient requirements for children are also listed in the COMA Report. Calculations are usually done with the reference nutrient intake (RNI). The child’s actual bodyweight, not the expected bodyweight, is used when calculating requirements. This is to avoid excessive feeding. For a