Neonatal cyanosis, methaemoglobinaemia and haemolytic anaemia.

The early and correct diagnosis of t he cause of neonatal cyanosis is a medical emergency, particularly if t he infant develops increasing acidosis and low arterial oxygenation. Rarely acquired methaemoglobinaemia may be the cause which, once diagnosed, may readily b e treated with the infusion of the reducing agent methylene blue (1). Occasionally, however, the treatment itself may have consequences, namely haemolytic aneamia and/or cyanosis ( 2 4 ) . The former, if severe enough, may entail an exchange transfusion for increasing hyperbilirubinaemia. Two infants are described. They developed methhaemoglobinaemia from an inadvertent injection of prilocaine hydrochloride (Citanest). They responded well t o methylene blue, though one developed severe jaundice. Case I . A boy, delivered normally at term, with an Apgar of 8 at 1 min and 10 at 5 min. By 2 hours he had become pale and dusky and by 3 hours he was quite blue with mild tachypnoea. His pulse was normal, there were no murmurs and his chest was clinically clear. Blood gases done with the infant in air and 90% ambient oxygen revealed a normal pH and Paco, levels and a Pao2 of 55 and 236 mmHg, respectively. Chest X-rays and electrocardiograph were normal and the haemoglobin was 143 gll. The infant remained grey-blue despite oxygen, and a blood spot on filter paper took on a brown-chocolate colour. Methaemoglobinaemia was diagnosed clinically and subsequently confirmed by spectral absorption peaks constituting 39% of the haemoglobin. An echocardiogram showed a structurally normal heart. Four mg of diluted methylene blue (approximately 1 mg/kg-birthweight 3650 g) was given intravenously over 5 min with a dramatic resolution of the cyanosis over the next 15-30 min. The infant did well and was discharged with its mother. Careful examination of the infant’s scalp revealed a tiny abrasion which was thought to be due to a needle prick. It was considered that the baby had inadvertently been injected with prilocaine hydrochloride when the mother’s perineum was injected prior to the episiotomy. Case 2. A boy, Baby A was delivered normally at term with an Apgar of 10 at 1 min and at 5 min. Within an hour he was slightly dusky and was quite blue when seen at 2 hours. He was otherwise normal where examined. Blood gases taken with the infant in air and 90% ambient oxygen revealed a normal pH and Paco, levels and a Pao2 of 86 mmHg, and 372 mmHg, respectively. Chest X-ray and electrocardiograph were normal and a filter paper test was again suggestive of methaemoglobinaemia. Four mg of methylene blue was given slowly i.v. (birthweight 3860 g), the colour of the infant returned to normal within half an hour. By the next day, however, the infant had become increasingly jaundiced. His serum bilirubin measured 309 mmol/l on day 3, at which time phototherapy was commenced. No incompatibility was noted on a direct Coombs’ test and a glucose-6-phosphate dehydrogenase screen was negative. By the 4th day the serum bilirubin had reached a level of 452 mmol/l and an exchange transfusion was carried out to a volume of 200 ml/kg. At that stage the infant’s liver and spleen were readily palpable. The blood film revealed an acute haemolytic picture with moderate anisocytosis, microcytosis, macrocytosis and spherocytosis. There was moderate polychromasia, poikilocytosis, fragmented cells, acanthocytosis and burr cells. Staining for Heinz bodies was not done at the time. Blood cultures were taken and the infant was given systemic antibiotics. The cultures proved negative. Phototherapy was continued, but the following day the seum bilirubin rose to 355 and then 362 mmol/l requiring a further exchange transfusion. He subsequently did well, although his haemoglobin progressively fell from 166 g/l on day 1 to 148 g/l on day 3 and to 94 g/I after the exchange transfusions and just prior to discharge. Again a careful examination of the infant’s scalp revealed a small pinprick. It was assumed that the baby had been inadvertently injected with prilocaine hydrochloride at the time of delivery.