Elevated levels of hypoxanthine in vitreous humor indicate prolonged cerebral hypoxia in victims of sudden infant death syndrome.

Hypoxanthine levels in vitreous humor from 32 infants who died of sudden infant death syndrome (SIDS) were determined and compared with levels found in eight children who died of trauma, drowning, or hanging and with levels from seven neonates dying suddenly without long-standing antemortem hypoxia. Determination of hypoxanthine level was done with either a PO2 electrode method or high-performance liquid chromatography. The results obtained by both methods were significantly correlated; therefore they were pooled. The median hypoxanthine level in victims of SIDS (380 mumol/L) was significantly higher (P less than .001) than in the children who died violently (118 mumol/L). Moreover, the levels from the SIDS victims were significantly higher (P less than .001) than those from the neonates who died without long-standing hypoxia (53 mumol/L). It is concluded that SIDS is probably not a sudden event but may be preceded by a relatively long period of respiratory failure and hypoxia.