“Non-stressed” NICU neonates have been shown to secrete cortisol (F) in discrete pulses at approx. 80 min intervals (Metzger JCEM 1993). Routine NICU clinical care often involves interventions and procedures. The aim of this study was to assess the effect of clinical state and interventions on plasma cortisol secretion in neonates. Blood samples for plasma F determination were taken via indwelling arterial lines at 15 min. intervals for six hours. Neonates with g.a. 25-40 wk were studied in the first 7 postnatal days. No infant had been exposed to antenatal steroid < 7 days before being studied. Characteristics of F secretion were estimated by deconvolution analysis. Clinical state, at time of study, was assessed by the SNAP score (Score for Neonatal Acute Physiology; Richardson, Pediatrics 1993). Data are presented as median (interquartile range). Infants with a SNAP score> 5 (n = 10) had a greater amplitude of F secretion than those with a SNAP≤ 5 (n=11) [11.8 (5.8 - 22.5) vs 4.7 (3.5 - 10.2) nmol/L.min; P = 0.014] but did not differ with respect to other deconvolution parameters. Compared with extubated neonates (n=11) those who were intubated/ventilated (n = 10) had a greater mass of F secreted per burst and also a greater F production rate [214 (197 - 275) vs 108 (94 - 121) nmol/L; P = 0.003; and 981 (900 - 1100) vs 484 (299 - 756) nmol/L/6h; P = 0.002]. Clinical interventions, as part of necessary care, during the 6 hr study period included endotracheal reintubation, ET suction, intravenous insertion, nasogastric tube insertion and chest physiotherapy. The group with clinical interventions (n = 11) did not differ from those without interventions (n=10) for any deconvolution parameter. These data provide new information about the effect of clinical state and interventions on pulsatile cortisol secretion in neonates. The pulsatile nature of cortisol secretion must be taken into consideration when measuring plasma cortisol as a marker of stress, even in premature neonates.
(Spon. by J C Sinclair).