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LETTER TO THE EDITOR

Glycine Encephalopathy and Anesthesia

Department of Anaesthesia; Dumfries and Galloway Royal Infirmary; Bankend Road; Dumfries, UK. DG1 4AP; dball{at}nhs.net

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).

Drs. Liu and Fan have elected not to reply to this letter.

REFERENCES

1. Liu C-M, Fan S-Z. Glycine encephalopathy and delayed emergence from anesthesia. Anesth Analg 2006;103:1631[Free Full Text]
2. Chung BHY, Wong KY, Lee JSK, lam BCC. Non-ketotic hyperglycinemia: a case report and review on treatment. Hong Kong J Paediatr 2002;7:152–6
3. Johnson JW, Ascher P. Glycine potentiates the NMDA response in cultured mouse brain nerones. Nature 1987;325:529–31[Medline]
4. Korman SH, Gutman A. Pitfalls in the diagnosis of glycine encephalopathy (non-ketotic hyperglycinemia). Dev Med Child Neurol 2002;44:712–40[Web of Science][Medline]
5. Johnson JW, Ascher P. Voltage-dependent block by intracellular Mg 2 + of N-methyl-D-aspartate-activated channels. Biophys J 1990;57:1085–90[Web of Science][Medline]
6. Allen RJ. Dextromorphan in infantile nonketotic hyperglycinemia. Neurology 1992;43:2422–3
7. Wolff JA, Kulovich S, Yu AL, Qiao CN, Nyhan WL. The effectiveness of benzoate in the management of seizures in nonketotic hyperglycinemia. Am J Dis Child 1986;140:596–602[Abstract/Free Full Text]

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