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 three times: before and after a cosyntropin (1.0 microgram/kg) stimulation test (performed prior to 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 x dopamine (μg/kg/min) + 1 x dobutamine) was used to monitor the catecholamine support an infant received. Infants were considered to have catecholamine-resistant hypotension if their highest Inotrope Score was >15. Results Of 95 infants enrolled, 43 (45%) developed hypotension and 14 (15%) developed catecholamine-resistant hypotension. Low post-operative cortisol levels were not associated with the overall incidence of hypotension following ligation. However, low cortisol levels were associated with the refractoriness of the hypotension to catecholamine treatment. In a multivariate analysis: the odds ratio for developing catecholamine-resistant hypotension was OR=36.6, CI=2.8–476, p=0.006. Low cortisol levels (in infants with catecholamine-resistant hypotension) were not due 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 following 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.

Objective We performed a multicenter study of preterm infants, who were about to undergo patent ductus arteriosus ligation, to determine if echocardiographic indices of impaired myocardial performance were associated with subsequent development of catecholamine-resistant hypotension following ligation. Study Design A standardized treatment approach for hypotension was followed at each center. Infants were considered to have catecholamine-resistant hypotension if their dopamine infusion was >15 µg/kg/min. Echocardiograms and cortisol measurements were obtained between 6 and 14 hours after the ligation (prior to the presence of catecholamine-resistant hypotension). Results 45 infants were enrolled: 10 received catecholamines (6 were catecholamine-responsive, 4 developed catecholamine-resistant hypotension). Catecholamine-resistant hypotension was not associated with decreased preload, shortening fraction or ventricular output. Infants with catecholamine-resistant hypotension had significantly lower levels of systemic vascular resistance and postoperative cortisol concentration. Conclusion We speculate that low cortisol levels and impaired vascular tone may play a more important role than impaired cardiac performance in post-ligation catecholamine-resistant hypotension.

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SUMMARYMethaemoglobinaemia is rare but should be considered in cases of cyanosis unresponsive to oxygen therapy. An example of this is given involving the accidental ingestion of Amyl Nitrite. CASE REPORTA 20-year-old girl attended the accident and emergency department following a collapse. She was alert and orientated, but complained of headache. Her blood pressure was 80/40 mmHg. Her most striking feature was a blue-grey discolouration of her skin. Oxygen therapy made no difference to her appearance, although blood gas analysis revealed a Pao2 of 46 kPa.She had been attending a Halloween party, but was not wearing make-up, and admitted taking 'Poppers' (Amyl Nitrite). Instead of inhaling the vapour, she had swallowed the liquid. Amyl Nitrite may produce methaemoglobinaemia, and this was confirmed by analysis of her blood which revealed a value of 30% methaemoglobin. When dropped on to a white sheet, a sample of her blood produced the characteristic chocolate colouration, which is a qualitative test for methaemoglobin. Gastric lavage was performed and she was resuscitated with intravenous colloid and intravenous Methylene Blue. No further complications followed and she was discharged the following day. DISCUSSIONMethaemoglobinaemia is characterized by increased amounts of haemoglobin where

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