Subdural haemorrhage as a predisposing factor for hyponatraemic convulsions in an infant undergoing test dose DDAVP infusion.

The infusion of desmopressin (DDAVP) is important in the investigation and treatment of selected bleeding diatheses. The potential toxicity of DDAVP is well known. In infants, hyponatraemic convulsions have been reported mostly with repeated infusions of DDAVP and rarely in the context of a single, test dose of DDAVP. We report a case of an infant with a small, resolving spontaneous subdural haematoma in whom a standard test dose infusion of DDAVP resulted in severe hyponatraemia and convulsions. Urinary arginine vasopressin analysis retrospectively identified a subclinical form of the syndrome of inappropriate antidiuretic hormone secretion (SIADH) as a likely predisposing factor. We conclude that even in patients with normal plasma sodium levels, DDAVP testing should be performed with caution and preferably deferred where the possibility of SIADH exists.