ObjectiveTo investigate the association of clinical workload and the decision to perform procedures on infants in the neonatal intensive care unit (NICU).DesignProspective cohort study over one academic year, observing infants exposed to housestaff working under various levels of clinical workload.SubjectsAll 31 housestaff rotating on the NICU service during the academic year 1993 to 1994 were observed. A total of 785 infants were admitted to these housestaff.SettingOne academic Level III intensive care nursery.Measurements and Main ResultsClinical workload was operationalized as number of NICU infants cared for by the individual houseofficer on-call each night. The procedures of interest were number of umbilical artery catheters (UACs), intubations, lumbar punctures (LPs), and peripheral phlebotomy performed by the houseofficer on-call.Using multiple linear regression approaches, controlling for the average severity-of-illness of each of the NICU infants, the experience and residency program of the houseofficer on-call, and the individual attending, we found that increased clinical workload (number of NICU infants) resulted in a significantly greater probability that an admitted infant received an umbilical artery catheter (p = .02), but resulted in less probability that any NICU infant received a lumbar puncture (p = .0001) or peripheral phlebotomy (p = .0002). The decision to intubate an infant was not affected by the workload in the NICU.ConclusionsThe clinical workload of housestaff in the NICU can affect decisions to perform procedures on infants in the NICU. For equivalently severely ill infants, there is a greater chance of receiving a UAC and less chance of being phlebotomized or receiving an LP when workload is high. Attending neonatologists need to be sensitive to possible effects of workload on patient care in the NICU. (Crit Care Med 1999; 27:815-820)