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Twenty-one patients with prolonged bleeding times secondary to inherited disorders of platelet function and eight patients with prolonged bleeding times secondary to acquired platelet dysfunction were given 0.3 micrograms per kilogram of DDAVP, 1-deamino-8-D-arginine vasopressin, intravenously. Sixteen of twenty-two DDAVP trials in patients with inherited platelet dysfunction (73%) and seven of the nine DDAVP trials in patients with acquired platelet dysfunction (78%) resulted in normalization or shortening of the prolonged bleeding times by at least 4 min. The bleeding time response did not correlate with changes in the levels of von Willebrand factor (vWf) antigen or ristocetin cofactor activity, nor was it associated with changes in vWf multimeric analysis or in vitro platelet aggregations following the administration of DDAVP. Shortening of the bleeding time with DDAVP was seen in patients with a failure to release/storage pool type defect, thromboxane synthesis type defect, Bernard-Soulier syndrome, Glanzmann's thrombasthenia, the May-Hegglin anomaly, liver disease, nonuremic renal disease, myelofibrosis, and Tangier's disease.

Desmopressin (DDAVP), a synthetic vasopressin, temporarily corrects bleeding abnormalities associated with mild hemophilia A, von Willebrand disease, and disorders of platelet function. The side effects of DDAVP are considered benign although most of its use has been in adults and older children. We report four children under the age of 2 years who became hyponatremic after intravenous DDAVP administration (0.3 microgram/kg). Three of them developed grand mal seizures. A review of the literature and these cases indicate that associated risk factors for hyponatremia after DDAVP administration include stress, surgery, anesthesia and narcotics (endogenous release of antidiuretic hormone), vomiting (loss of Na+), liver disease (hindered metabolism of DDAVP), renal tubular acidosis (chronically low serum Na+), multiple doses of DDAVP, and overhydration with hyponatremic fluids. DDAVP is not a benign drug in this age group and shows a serious potential for hyponatremia and seizures. Fluid restriction, avoidance of hyponatremic solutions, and close monitoring of serum electrolytes and urine output for at least 15-20 hr after the administration of DDAVP, when used in children under the age of 2 years, is warranted.

Heparin cofactor II (HC II) was measured by a chromogenic activity assay in normal preterm infants (gestational age, 28-36 weeks; n = 17; 29% +/- 11.5 [mean +/- 1 SD], range 11-51), normal full-term infants (n = 18; 49% +/- 6.6 [mean +/- 1 SD], range 36-58), and normal adults (n = 38; 101% +/- 14 [mean +/- 1 SD], range 73-130). Normal children attained adult levels at approximately 5 to 7 months of age. The lower values in preterm and term infants most likely reflect immature liver function. Neither adults and children with a history of thrombosis with prior negative evaluation (n = 74), patients with documented protein C and protein S deficiency (n = 4), nor sick infants without evidence of consumptive coagulopathy (n = 15) had significantly lower levels of HC II activity. Infants with disseminated intravascular coagulation (n = 2) had strikingly lower levels of HC II activity.