Evaluating the Low-Dose ACTH Stimulation Test in Neonates: Ideal Times for Cortisol Measurement.

CONTEXT: Low-dose adrenocorticotropic hormone stimulation testing (LDST) can be used to diagnose central adrenal insufficiency. However, uncertainty remains over optimal times to draw serum cortisol levels. OBJECTIVE: To determine optimal times to draw serum cortisol levels for the LDST in neonates. DESIGN: A retrospective chart review of LDSTs performed on neonates from January 1, 2009 to September 30, 2017. SETTING: Children's Hospital of Eastern Ontario (CHEO), a tertiary-care outborn pediatric center. PATIENTS: Forty-nine patients were included: 23 (46.9%) born at term, 12 (24.5%) born very preterm to late preterm, and 14 (28.6%) born extremely preterm. INTERVENTION: Cortisol levels were drawn at baseline and 15, 30, and 60 minutes following administration of Cortrosyn 1 mcg/kg (maximum dose 1 mcg). MAIN OUTCOME MEASURE: Timing of peak cortisol level and marginal value of drawing a second and third cortisol sample at 15, 30, or 60 minutes was determined. RESULTS: Cortisol peaked at 15-, 30-, and 60-minute sampling times for 4%, 27%, and 69% of patients, respectively. The probability that a failed LDST changes to a pass by adding a 15- or 30-minute sample to the superior 60 minute sample is 5.6% (1% to 25.8%) and 11% (3.1% to 32.6%), respectively, for a cortisol pass threshold of 18.1mcg/dL (500 nmol/L). CONCLUSIONS: In contrast to studies of older children, we found that the majority of neonatal LDST cortisol peaks occurred at the 60-minute sampling time with the addition of a 30-minute sample providing substantial benefit. It is questionable if a 15-minute sample provides any benefit, making a case to revise LDST protocols to sample cortisol later for neonates.

Photoprotection But Not N-acetylcysteine Improves Intestinal Blood Flow and Oxidation Status in Parenterally Fed Piglets.

OBJECTIVES: The purpose of the present study was to determine if protecting parenteral nutrition solutions from ambient light and supplementing with N-acetylcysteine (NAC) improves mesenteric blood flow, gut morphology, and oxidative status of parenterally fed neonates. METHODS: Neonatal Yucatan miniature piglets (n = 23, 7-11 days old) were surgically fitted with central venous catheters and an ultrasonic blood flow probe around the superior mesenteric artery. Piglets were fed continuously for 7 days either light-protected (LP) or light-exposed (LE) complete parenteral nutrition that was enriched with either NAC or alanine (ALA). RESULTS: There were no differences in body weight or overall gut morphology among groups after 7 days. Plasma concentrations of NAC were greater and total homocysteine lower in NAC- versus ALA-supplemented pigs on day 7 (N-acetylcysteine: 94 vs 7 µmol/L; P < 0.001; homocysteine: 14 versus 21 µmol/L; P < 0.005); plasma total glutathione was not affected. Hepatic lipid peroxidation was reduced by 25% in piglets that received LP parenteral nutrition (P < 0.05). The mesenteric artery blood flow decreased in all pigs between days 2 and 6 (P < 0.001) because of parenteral feeding. Photoprotection alone (LP-ALA) attenuated the decrease in mesenteric blood flow to 66% of baseline on day 6 compared with LE-ALA (37%; P < 0.05) and LP-NAC pigs (43%; P = 0.062); LE-NAC piglets had intermediate reductions in blood flow (55%). CONCLUSIONS: Photoprotection of parenteral nutrition solutions is a simple, effective method to attenuate decline in blood flow to the gut and hepatic lipid peroxidation, which are both commonly associated with parenteral feeding.