Glycine Encephalopathy and Anesthesia

Abstract

To the Editor: Liu and Fan report delayed recovery from sevoflurane anesthesia in a child with glycine encephalopathy (1), a metabolic disease of defective glycine cleavage (2), and suggest that increased levels of glycine account for the inhibitory effects of the condition. We write to emphasize that inhibitory and excitatory signs may coexist. The excitatory phenomena result from NMDA receptor activation (3) and using ketamine as an antagonist is reported (4). We suggest that ketamine anesthesia is a reasonable choice for their patient: this agent has additional benefits of cardiorespiratory stimulation. Magnesium is also an NMDA receptor blocker (5). In theory, magnesium may be helpful but we are not aware of magnesium therapy for these patients. Dietary intake in chronically ill patients may be impaired leading to nutrient and electrolyte deficits. Magnesium deficiency may therefore be involved in this condition, but this is speculative. Other therapies may be useful in the perioperative period. Oral dextromorphan, formulated as cough medication has been used, which acts to non-competitively bind to the NMDA receptor (6). Sodium benzoate has also been used because its metabolism depletes available glycine and can decrease CSF glycine levels, improving seizure control and wakefulness (7). C. Barker, FRCA, Specialist Registrar P. Jefferson, FRCA, Consultant David R. Ball, MB, BS, Consultant Department of Anaesthesia Dumfries and Galloway Royal Infirmary Bankend Road Dumfries, UK. DG1 4AP [email protected] Drs. Liu and Fan have elected not to reply to this letter.