OBJECTIVEA considerable percentage of preterm infants with posthemorrhagic hydrocephalus initially managed with an Ommaya reservoir require a permanent CSF shunt. The objective of the study was to analyze possible risk factors associated with the need for converting an Ommaya reservoir to a permanent shunt.METHODSThe authors retrospectively reviewed the clinical records of premature infants weighing 1500 g or less with posthemorrhagic hydrocephalus (Papile grades III and IV) managed with an Ommaya reservoir at their institution between 2002 and 2017.RESULTSForty-six patients received an Ommaya reservoir. Five patients (10.9%) were excluded due to intraventricular infection during management with an Ommaya reservoir. Average gestational age and weight for the remaining 41 patients was 27 ± 1.8 weeks and 987 ± 209 grams, respectively. Thirty patients required a permanent shunt and 11 patients did not require a permanent shunt. The conversion rate from an Ommaya reservoir to a permanent shunt was 76.1%. Symptomatic persistent ductus arteriosus (PDA) was more frequent in the nonpermanent shunt group than in the shunt group (88.9% vs 50%, p = 0.04). The need for extraction of more than 10 ml/kg per day of CSF through the Ommaya reservoir was lower in the nonpermanent shunt group than in the shunt group (9.1% vs 51.7%, p = 0.015). CSF lactate was lower in the nonpermanent group than in the shunt group (mean 2.48 mg/dl vs 3.19 mg/dl; p = 0.004). A cutoff value of ≥ 2.8 mg/dl CSF lactate predicted the need for a permanent shunt with sensitivity and specificity of 82.4% and 80%, respectively. There were no significant differences in gestational age, sex, weight, Papile grade, ventricular index, or other biochemical markers. After the multivariate analysis, only CSF lactate ≥ 2.8 mg/dl was associated with a higher conversion rate to a permanent shunt.CONCLUSIONSThis study showed that a high level of CSF lactate, absence of symptomatic PDA, and a higher CSF extraction requirement were associated with a higher likelihood of implanting a permanent CSF shunt. The authors believe these findings should be considered in future studies.