STRESS, SEVERITY OF ILLNESS, AND OUTCOME IN VENTILATED PRETERM INFANTS

Aim-To determine physiological and hormonal stress responses in ventil ated preterm infants. Methods-Physiological and hormonal stress respon ses were studied in 47 ventilated preterm infants who were judged clin ically to require sedation. The correlation between the stress respons e and severity of illness was examined, and responses were compared be tween infants with different clinical outcomes. Results-Stress hormone concentrations were significantly correlated with severity of illness , assessed using the arterial:alveolar oxygen partial pressure ratio. Noradrenaline showed the strongest correlation, with an exponential pa ttern of increased secretion. Catecholamine concentrations before seda tion were significantly higher among infants who subsequently died (n = 15, at a median age of 6 days) than among survivors: median noradren aline 4.31 vs 2.16 nmol/l, median adrenaline 0.69 vs 0.31 nmol/l. The observed fall in noradrenaline with sedation was lower among those who died than survivors (median fall 2% vs 40%). Conclusion-Preterm infan ts are capable of hormonal stress responses appropriate for the severi ty of their illness. Extreme catecholamine responses, in the sickest i nfants, are associated with the worst outcome.