Anabolism: Practical Strategies

Abstract

To maintain anabolism, the body needs sufficient calories, and essential building blocks such as essential amino acids, essential fatty acids, vitamins, and minerals. The source of the calories depends on the availability with during fasting a switch from carbohydrate use to glycogenolysis, protein and fat catabolism with accompanying ketogenesis. Fat breakdown occurs between 15 and 20 hours fasting. Prevention of fat catabolism requires avoidance of fasting for longer than this duration. Practical issues arise around night time fasting. If short term catabolism has to be prevented during illness, then a solution based on alpha-dextrin maltose can be used. Solutions of increasing concentration with age given in frequent small amounts are best tolerated. Alternatives can be simple sugar based or combinations with fat included. If intravenous nutrition is required, glucose 10% solution at 1.5 times maintenance provides part caloric support, but for sufficient caloric intake lipid at 2 g/kg/day or more should be added. Early introduction of protein will result in more rapid protein synthesis, even during episodes of hyperammonemia. To limit protein, an intravenous solution of essential amino acids in combination with a regular protein source is used being careful to avoid amino acid imbalances. Tight glucose control with early use of insulin (glucose < 170 mg/dL) further improves anabolism. Combined use of these anabolic factors together with hemodialysis and intravenous ammonia scavenging medications has allowed control of ammonia in 12 hours without rebound. Brain MRI scan at 3 days later reviewed using a new scoring system then allows for recognition of neurological sequelae to guide further management. Finally, similar principles can be applied for intravenous ketogenic diet, but pancreatitis is a concern. The main factors now include immediate introduction of intravenous lipid, immediate start of essential amino acid supplementation in hyperammonemia, early use of insulin, all aiming at immediately supporting anabolism at optimal levels.