Nutrition in head injury

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1. Patients with isolated head injuries have 140% of normal caloric demand or about 3500 kcal/day in a 70 kg man
   1. calorie requirements for normal individuals can be estimated by multiplying the weight in kg x 25
   2. those with GCS 4-5 need 50-60 kcal/kg/day (more in the second week after injury), GCS 6-7 need 40-50 kcal/kg/day and those with GCS 8-12 need 30-35 kcal/kg/day
   3. older patiens may require more calories than younger patients
2. After a major injury nitrogen excretion greatly increases and a loss of lean body mass to fat may go as high as 4:1 (NOTE: for every 1 g of nitrogen excreted, 6.25 g of protein has been catabolized) with the most beakdown occurring in the second week following injury
   1. protein requirements of 1.2-1.6 g/kg are needed in head injury patients
   2. alanine is the primary amino acid used for gluconeogenesis
   3. normal individuals excrete about 30g of protein per day
3. Overfeeding is not desirable since in causes hyperglycemia, uremia and increased CO2 production
4. NOTE: respiratory quotient for carbohydrdates is 1.0 while for fat it is 0.7 and protein is 0.8 so high carbohydrate enteral feeds produce more CO2
   1. fat provides 9 kcal/g while carbohydrate and protein provide 4 kcal/g
   2. the average person has about 150,000 kcal in fat stores, 24,000 kcal in protein and 900 kcal in glycogen
      1. patients with McArdle’s disease have a defect in muscle phosphorylase and are unable to fully utilize glycogen in the glycolytic pathway; autosomal recessive
      2. acid maltase deficiency is a type of glycogen storage disease with three clinical forms (Pompe’s disease, childhood, and adult) where large amounts of glycogen deposited in various organs; autosomal recessive
   3. anaerobic metabolism creates lactate which can be converted to glucose in the Cori cycle
5. Linoleic and linolinic acid are the only essential fatty acids; without it cardiac dysfunction and an increased susceptibility to infection may occur
6. Thiamine (vitamin B1) is an essential cofactor in carbohydrate metabolism; the body has only a 10 day store of thiamine so replacement is necessary
   1. lack of thiamine may cause cardiac dysfunction, Wernicke’s encephalopathy and lactic acidosis
   2. vitamin requirements: vitamin A,B12,C,D,E,K, B1 (thiamine), B2 (riboflavin), B6 (pyridoxine), pantothenic acid, biotin, folate
7. essential trace elements: chromium, copper, iodine, iron, manganese, selenium, zinc
   1. toxicity of manganese can cause parkinsonian symptoms with neuronal loss and gliosis in the pallidum and striatum; symptoms improve with L-DOPA