BIRTH WEIGHT-SPECIFIC MORTALITY FOR EXTREMELY LOW-BIRTH-WEIGHT INFANTS VANISHES BY 4 DAYS OF LIFE - EPIDEMIOLOGY AND ETHICS IN THE NEONATALINTENSIVE-CARE UNIT

Background. The persistent differences between those who question the appropriateness of aggressive resuscitative measures for many extremel y low birth weight (ELBW) infants (birth weight <1001 g) and those who generally initiate such treatment has been a source of ongoing tensio n for physicians, parents, judges, and policymakers. We believe that m uch of this tension may be a result of the way the issue is framed. We began this study with the intuition that although many ELBW infants d ie, most succumb quickly. Were this true, discussions that considered only survival rates might miss the point. A more relevant statistic mi ght be the degree to which interventions prolong dying, extend sufferi ng, or use resources for infants who will eventually die. Methods. We determined the survival and nonsurvival for 429 ELBW infants admitted to our neonatal intensive care unit (NICU) for 3 years. We noted parti cularly the relationship between birth weight, illness severity (fract ion of inspired oxygen [Fio(2)] requirement for infants requiring mech anical ventilation), and the time course of mortality for nonsurvivors . We next calculated a resource utilization index (NICU bed days occup ied by survivors and nonsurvivors) for each patient and for the popula tion as a whole. Finally, we determined how NICU resources were distri buted among infants who eventually died and those who survived. Result s. Of the 429 ELBW infants alive on day of life (DOL) 1, 202 (47%) sur vived to be discharged. On DOL 1, both birth weight and illness severi ty independently predicted likelihood of survival. Approximately 80% o f ELBW deaths occurred in the first 3 days of life-consequently, once an infant had survived to DOL 4, the likelihood of survival was dramat ically enhanced (81% for the 249 patients alive on DOL 4). In addition , although survival for DOL 4 infants continued to depend on illness s everity, survival no longer depended on birth weight. These observatio ns on DOL 4 were confirmed in the subpopulation of 212 infants whose b irth weight was <750 g. Overall, although 53% of ELBW babies admitted died, only similar to 13% of all NICU bed-days (a proxy for resource a llocation) were devoted to infants who did not survive. This figure di d not vary as a function of birth weight. Conclusions. Generally, when we talk of survival rates to parents, ethics committees, or policy ma kers, we base our predictions largely on birth weight. The data presen ted here suggest that predictions should be corrected by including DOL and that, when this is done, the prognostic value of birth weight rap idly diminishes. In addition, birth weight-specific mortality and day of death for nonsurvivors correlated inversely; that is, more of the s maller infants died, but the doomed ones died more quickly. Consequent ly, medical resources allocated to nonsurvivors remained low, and inde pendent of birth weight. This formulation lends weight both to the rea sonableness of physicians in offering NICU care to ELBW infants with u nlikely prospects for survival, and of parents and surrogate decision- makers in requesting/assenting to it.