Rationale:
Arginase deficiency(AD) is a rare inherited metabolic disorder characterized by the inability of the body to metabolize arginine adequately resulting in the accumulation of arginine and its metabolites in the blood and risk of hyperammonemia. Without adequate treatment including an arginine-restricted diet, children present with seizure disorders, progressive spasticity and developmental delay. Typical diets for AD are natural protein-restriction with essential amino acid supplements and carbohydrate intake of 45 – 65% total calorie intake. The ketogenic diet(KD) is a high fat, low carbohydrate diet used to treat intractable epilepsy. Carbohydrate intake is less than 19% total calorie intake.
During prolonged fasting periods or intercurrent illness, patients with AD require high dextrose intravenous (IV) fluids to prevent catabolism and metabolic decompensation, while patients treated with KD cannot receive dextrose or they risk losing ketosis and developing seizures. We present a patient treated with a KD and arginine-restricted diet for AD and drug-resistant epilepsy during maintenance care and 3 periods of prolonged fasting.
Method:
A 16-year-old boy with AD and drug-resistant epilepsy treated with a combination of 3.5:1 ratio classic KD and a severe protein-restricted diet. His diet comprised of KetoCal 3:1 powder to provide natural protein and carbohydrate intake and Essential Amino Acid Mix (Nutricia) to provide his metabolic protein. Canola and MCT oil were added for fat. Caloric and protein intake were increased for growth and in response to lab results. His competing metabolic demands were managed during 3 procedures requiring prolonged fasting, including craniotomy with corpus callosotomy, bilateral foot reconstruction and vagal nerve stimulator insertion. A combination of 10% dextrose, SMOF 20% lipids and normal saline IV fluids was used to provide sufficient calories, fluids and 3.5:1 KD ratio during fasting periods.
Results:
The diet provided 0.75–0.85 g protein/kg/d (50% natural protein/50% essential amino acids). Urine ketone levels were 8-16 mmol/L. The diet was adjusted collaboratively with Metabolics and KD teams to raise calories/protein intake and address concerns arising with growth or lab results(Table 1).
During three periods of prolonged fasting, ketosis was maintained while preventing metabolic worsening. Urine ketones ranged from 4-16 mmol/L, except for one temporary drop to 0.5 mmol/L. Blood glucose ranged from 3.9–10.6 mmol/L(Table 2). Higher glucose levels occurred during the immediate post-procedure period. Our patient maintained good metabolic control before, during and after procedures. Seizure activity was unchanged from baseline.
Conclusion:
Patients treated with a combined protein-restriction and KD diet present with competing metabolic needs requiring close surveillance and diet adjustments to prevent complications. During periods of prolonged fasting, using a combination of high dose IV lipids, dextrose and saline fluids may prevent metabolic decompensation while maintaining ketosis.
Funding:
:No funding was received.
FIGURES
Figure 1