Temps i espais

Malnutrition is a well recognised comorbid condition in dialysis patients that contributes to the increased mortality seen in these patients.

8.1Causes of protein energy malnutrition

• Increased net protein catabolism

• Anorexia, nausea and vomiting

• Inter-current illness e.g.infection

• Increased circulating levels of catabolic hormones e.g. glucagons, PTH

• Dialytic loss of amino acids and vitamins

• Intradialytic hypercatabolism – dialyser bioincompatability 8.2 Nutritional changes in uraemia

a. Protein metabolism

• Increased degradation of protein and amino acids

• Increase in non-essential amino acids and decrease in essential amino acids

b. Carbohydrate metabolism

Impaired glucose tolerance due to:

• increased peripheral resistance to insulin

• decreased beta cell sensitivity to glucose levels

• increased hepatic gluconeogenesis c. Lipid metabolism

• Moderate increase in triglyceride levels

• Normal or slight increase in cholesterol 8.3 Evaluation of Nutritional status

a. Nutritional status in maintenance dialysis patients should be assessed with a combination of valid, complementary measures rather than any single measure alone

b. Nutritional status should be routinely assessed. This may include predialysis serum albumin, body mass index (BMI), subjective global assessment, dietary interview, diaries and protein nitrogen appearance (PNA)

c. Serum albumin, creatinine and cholesterol are valid and clinically useful markers of protein energy nutritional status. The following levels suggest protein-energy malnutrition:

i. Albumin < 40g/L ii. Creatinine < 880umol/L iii. Cholesterl < 3.8 mmol/L

d. PNA and protein catabolic rate (PCR) are valid and clinically useful measures of net protein degradation and protein intake in maintenance dialysis patients

e. Anthropometric measurements including % usual body weight, % standard body weight, BMI, skinfold thickness, estimated % body fat, mid arm muscle area, circumference or diameter are valid and

clinically useful indicators of protein energy nutrition status 8.4 Nutrition in the haemodialysis patient

8.4.1 Carbohydrate intake

a. Dialysis improves the abnormalities of glucose metabolism. The insulin requirement of diabetic patients may be reduced on dialysis days due to improvement of the tissue sensitivity to insulin. The response of the diabetic patient to hypoglycaemia is blunted during haemodialysis. These patients should reduce their insulin intake on dialysis days and eat before dialysis. One important aim in supplying adequate calories is to reduce protein breakdown for gluconeogenesis.

b. The total daily calorie requirement is about 35 kcal/kg/day.

Carbohydrate should consist of more complex carbohydrates to avoid frequent peaks of glycaemia.

8.4.2 Protein intake

a. An adequate nitrogen balance is important for patients on dialysis. There is significant correlation between serum albumin and mortality. During hemodialysis, patients lose 1.5 to 3 gram of amino acids per hour of dialysis. The losses are increased when glucose-free dialysate is used.

b. It is important that pre-dialysis patients should not be subjected to severe protein restriction that may deplete their protein stores.

c. The amount of protein needed for positive nitrogen balance is 1.0 to 1.2g/kg/day. The protein should be derived from animal source and they should account for at least 50% of the total protein intake.

8.4.3 Fat intake

a. The lipid abnormalities of patients on chronic haemodialysis have been correlated with cardiovascular mortality. The reason for the abnormalities include:

• Impaired catabolism of VLDL - retention of a lipoprotein lipase inhibitor

• dialysate (conversion of acetate to long chain fatty acids and cholesterol)

b. Lipid intake should be 25% of the total energy requirement. It should be in the form of vegetable fats (maize, sunflower oil) which contains polyunsaturated oils. Dietary control of hyperlipidemia includes the reduction of intake of saturated fat and reduction in carbohydrates.

8.4.4 Calcium and phosphorus

a. Uraemia is associated with accumulation of phosphorus and low calcium level. In haemodialysis the removal of phosphate is less efficient than in CAPD.

b. The dietary intake of phosphate should be limited to 800mg to 1200 mg daily

c. The serum phosphate should be kept below 1.6 mmol/l

d. Patients on dialysis require calcium supplements if they are hypocalcaemic. A total of 1200 mg/day may be needed.

Table 8.1 Foods rich in phosphate

Liver Nuts and nut products Evaporated milk Kidney Legumes e.g. peas, beans Condensed milk

Heart Butter/peanut butter Yoghurt

Brain Baked beans Cheese

Canned meat Bean products Cocoa

Sardines Egg yolk Chocolate

Crabs Coconut & all coconut

products Foods with chocolate

Prawns Kaya Instant coffee

Mussels Dried fruit Horlicks

Scallops Keropok Ovaltine

Shellfish Ikan Bilis Cereals e.g. oats

Mushrooms Wholemeal bread

Cauliflower Bovril, Marmite

Cola drinks

Beer

8.4.5 Vitamins

Supplements of water soluble vitamins are recommended as they are lost during dialysis.

• Vitamin B1 4mg/day

• Vitamin B6 10mg/day

• Vitamin C 100 mg/day

• Folic acid 0.5-1mg/day

• Iron supplement 200 mg /day

8.4.6 Sodium and water

a. The amount of water allowed varies with residual urine output b. If the patient has residual urine output sodium intake should be

restricted to 130-170 mmol/day (3-4 g/day)

c. If the patient is anuric sodium intake should be reduced to 40-80 mmol/day (1-2g/day). Interdialytic weight gain should not be >

3% of dry weight.

8.4.6 Potassium

Hyperkalemia may result from excessive intake of fruits and vegetables. If the patient is anuric potassium intake should be restricted to 50 mmol/day. Those with adequate urine output require mild dietary restriction.

Table 8.2 Foods rich in potassium

Pure fruit juices Bran Bovril, Marmite Dried fruit Bran cereal Brown sauce

Ribena Muesli Salt substitutes

Tomato juice Nuts Curry powder

Tomato sauce Peanut butter Beer, lager, wine Vegetables Crisps

8.5 Management of acid base status

Predialysis serum bicarbonate levels should be maintained at or above 22mmol/l and measured regularly

8.6 Nutritional support

Individuals on hemodialysis who are unable to meet their protein and energy requirements with food intake for an extended period of time should receive nutritional support. Complete nutritionl assessment should be done and reversible or treatable conditions should be identified. Oral diet may be started , proceeding to tube feeding if unsuccessful. Intradialytic parenteral nutrition or daily total or partial parenteral nutrition should be considered if the former fails.

8.7 Recommended nutritional intake in patients on haemodialysis The nutritional prescription should be individualised and the motivation of the patient plays a vital role in ensuring compliance:

a. Dietary protein intake 1.2 g/kg/day b. Total energy intake > 35 kcal/kg/day c. Water and salt as allowed by fluid balance

d. Potassium 50 mmol/day + 25 mmol/day for each litre of residual urine

e. Calcium 1.2 g/day f. Phosphate 0.8-1.2g/day

References

1. K/DOQI Clinical Practice Guide for Nutrition in Chronic Renal Failure.

2. Handbook of Dialysis. 3^rd Edition. John B. Daugirdas. Todd S.Ing