Hypotension following patent ductus arteriosus ligation: the role of adrenal hormones.

OBJECTIVE: To test the hypothesis that an impaired adrenal response to stress might play a role in the hypotension that follows patent ductus arteriosus (PDA) ligation. STUDY DESIGN: We performed a multicenter study of infants born at <32 weeks' gestation who were about to undergo PDA ligation. Serum adrenal steroids were measured 3 times: before and after a cosyntropin (1.0 µg/kg) stimulation test (performed before the ligation), and at 10-12 hours after the ligation. A standardized approach for diagnosis and treatment of postoperative hypotension was followed at each site. A modified inotrope score (1 × dopamine [µg/kg/min] + 1 × dobutamine) was used to monitor the catecholamine support an infant received. Infants were considered to have catecholamine-resistant hypotension if their greatest inotrope score was >15. RESULTS: Of 95 infants enrolled, 43 (45%) developed hypotension and 14 (15%) developed catecholamine-resistant hypotension. Low postoperative cortisol levels were not associated with the overall incidence of hypotension after ligation. However, low cortisol levels were associated with the refractoriness of the hypotension to catecholamine treatment. In a multivariate analysis: the OR for developing catecholamine-resistant hypotension was OR 36.6, 95% CI 2.8-476, P = .006. Low cortisol levels (in infants with catecholamine-resistant hypotension) were not attributable to adrenal immaturity or impairment; their cortisol precursor concentrations were either low or unchanged, and their response to cosyntropin was similar to infants without catecholamine-resistant hypotension. CONCLUSION: Infants with low cortisol concentrations after PDA ligation are likely to develop postoperative catecholamine-resistant hypotension. We speculate that decreased adrenal stimulation, rather than an impaired adrenal response to stimulation, may account for the decreased production.

Enteral feeding during indomethacin and ibuprofen treatment of a patent ductus arteriosus.

OBJECTIVE: To test the hypothesis that infants who are just being introduced to enteral feedings will advance to full enteral nutrition at a faster rate if they receive "trophic" (15 mL/kg/d) enteral feedings while receiving indomethacin or ibuprofen treatment for patent ductus arteriosus. STUDY DESIGN: Infants were eligible for the study if they were 23(1/7)-30(6/7) weeks' gestation, weighed 401-1250 g at birth, received maximum enteral volumes ≤60 mL/kg/d, and were about to be treated with indomethacin or ibuprofen. A standardized "feeding advance regimen" and guidelines for managing feeding intolerance were followed at each site (N = 13). RESULTS: Infants (N = 177, 26.3 ± 1.9 weeks' mean ± SD gestation) were randomized at 6.5 ± 3.9 days to receive "trophic" feeds ("feeding" group, n = 81: indomethacin 80%, ibuprofen 20%) or no feeds ("fasting [nil per os]" group, n = 96: indomethacin 75%, ibuprofen 25%) during the drug administration period. Maximum daily enteral volumes before study entry were 14 ± 15 mL/kg/d. After drug treatment, infants randomized to the "feeding" arm required fewer days to reach the study's feeding volume end point (120 mL/kg/d). Although the enteral feeding end point was reached at an earlier postnatal age, the age at which central venous lines were removed did not differ between the 2 groups. There were no differences between the 2 groups in the incidence of infection, necrotizing enterocolitis, spontaneous intestinal perforation, or other neonatal morbidities. CONCLUSION: Infants required less time to reach the feeding volume end point if they were given "trophic" enteral feedings when they received indomethacin or ibuprofen treatments.

Administration of rescue surfactant by laryngeal mask airway: lessons from a pilot trial.

OBJECTIVES: To determine if surfactant can be effectively administered to larger preterm babies by laryngeal mask airway (LMA), reducing the need for supplemental oxygen. STUDY DESIGN: Enrollment criteria: birth weight > 1200 g, < 72 hours old, treated with nasal continuous positive airway pressure (nCPAP) for respiratory distress syndrome, with fraction of inspired oxygen (Fio2) requirement between 0.30 and 0.60. Subjects were randomized either to receive 3 mL/kg calfactant by LMA (experimental) followed by LMA removal back to CPAP, or continued on nCPAP (control). After intervention, both groups remained on nCPAP with Fio2 adjusted to maintain O2 saturations at 88 to 95%. RESULTS: A total of 26 patients (13 per group) were randomized, and 24 completed the study (11 experimental, 13 control). Groups were similar with respect to gender, mode of delivery, estimated gestational age, birth weight, and oxygen and pressure requirements at enrollment. Infants enrolled in the treatment group had an abrupt and sustained decrease in oxygen requirement after LMA surfactant therapy. CONCLUSION: This pilot study demonstrates that surfactant can be delivered by LMA, which leads to a significant decrease in supplemental oxygen requirement. Larger controlled trials in low-resource settings may show this technique to be valuable in clinical situations where direct laryngoscopy and intubation are difficult or where resources for mechanical ventilation are limited.

Understanding clinical literature relevant to spontaneous intestinal perforations.

Spontaneous intestinal perforation (SIP) has emerged as a disease of extremely low-birth-weight (ELBW) infants over the last two decades. Several risk factors have been associated with this disease including early postnatal steroids (EPS; use within the first week of life), early use of indomethacin (EUI; use within the first 3 postnatal days), and the synergistic combination of the two. These two risk factors are thought to play a causal role in the etiology of SIP through their effects on ileal trophism and motility. Two infectious agents ( Candida and Staphylococcus epidermidis) are commonly grown from peritoneal cultures of patients with SIP. It is less clear whether these infections play a causal role or if they represent comorbidities of perforation. Chorioamnionitis is thought to be a risk factor for SIP, as is the stress and elevated cortisol that accompanies it. Recent analyses suggest that antenatal indomethacin may also be a risk factor for SIP, particularly when given close to birth. These latter variables are more challenging to rank in importance compared with EPS and EUI, which have been repeatedly associated with SIP in both retrospective cohorts and randomized controlled trials. Because neonatal care of the ELBW infant is commonly standardized, the habitual combination of any of these risk factors potentially amplifies the risk of SIP. Many of these factors are medicines, thus SIP risk is exacerbated by select forms of polypharmacy. Our challenge lies in understanding how these drug interactions lead to harm.