figure). Arterial waveforms were collected over 20 second periods and the true mean arterial pressure (MAP) derived. Data were stored on floppy disk and the 20 second cycles repeated. Ultrasound scans were made at least daily during the first week and then weekly until discharge, with an ATL Mark III sector scanner with multifrequency head (3/5/7.5 MHz).Thirty three infants were entered into the study; 28 were having mechanical ventilation, and five required headbox oxygen for the respiratory distress syndrome. Treatment was independent of the results of the study, the clinicians having no access to the data collected. Pethidine and pancuronium were given when required, and plasma or 5% human albumin was given slowly (10-15 ml/kg) if perfusion was considered inadequate. Seven infants received inotropic support for extreme underperfusion (dopamine or dobutamine, or both, in a dose of 5-10 [igIkg/min) starting on average 101/2 hours after birth.

BACKGROUND The pathogenesis of pulmonary vascular disease in children with congenital heart disease is incompletely understood. Thromboxane (TX) A2 and prostacyclin (PGI2) have opposing effects on platelet aggregation and pulmonary vascular smooth muscle. An imbalance in their biosynthesis could contribute to the progressive increase in pulmonary vascular resistance seen in older untreated patients with pulmonary hypertensive congenital heart disease and the thrombotic complications they may develop. METHODS AND RESULTS We investigated TXA2 and PGI2 biosynthesis in 15 young children (0.2 to 2.25 years old) with congenital heart disease with increased pulmonary blood flow and potentially reversible pulmonary vascular disease by measuring urinary excretion of 2,3-dinor-TXB2 and 2,3-dinor-6-oxoprostaglandin (PG) F1 alpha and compared the findings with those in 16 healthy children (0.5 to 2.8 years old). 2,3-Dinor-TXB2 excretion was greater in the patients than in control subjects (1253 +/- 161 versus 592 +/- 122 ng/g creatinine; P < .001). Excretion of 2,3-dinor-6-oxo-PGF1 alpha was 452 +/- 54 compared with 589 +/- 95 ng/g creatinine in control subjects. In 5 patients who underwent successful cardiac surgery > or = 1 year later excretion of 2,3-dinor-TXB2 decreased from 1100 +/- 298 to 609 +/- 131 ng/g creatinine (P < .05), a value comparable to those in 5 healthy children of similar age (749 +/- 226 ng/g creatinine). We also compared 15 patients (11 to 23 years old) with advanced irreversible pulmonary vascular disease with 19 healthy control subjects (10 to 23 years old). The ratio of TX to PGI2 metabolite excretion was greater in the patients than in control subjects (3.5 +/- 0.6 versus 2.0 +/- 0.3; P < .05). CONCLUSIONS There is increased 2,3-dinor-TXB2 excretion in children with congenital heart disease and a high pulmonary blood flow that may reflect an imbalance in biosynthesis of TXA2 and PGI2 in the pulmonary vascular bed. The imbalance may contribute to the progressive development of increased pulmonary vascular resistance and persists in older patients whose heart defects are uncorrected.

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Objective-To determine the feasibility of studying myocardial and skeletal muscle bioenergetics using 31p magnetic resonance spectroscopy (MRS) in babies and young children with congenital heart disease.Subjects-16 control subjects aged 5 months to 24 years and 18 patients with CHD, aged 7 months to 23 years, of whom 11 had cyanotic CHD, five had cardiac failure, and two had had a Senning procedure. Design-3P MRS was carried out using a 1*9 Tesla horizontal 65 cm bore whole body magnet to study the myocardium in 10 patients and skeletal muscle (gastrocnemius) in 14 patients, eight of whom were exercised, together with appropriate controls. Results-In hypoxaemic patients, in skeletal muscle at rest intracellular pH patients fatigued more quickly but endexercise pHi and phosphocreatine recovery were normal, implying that an equivalent but smaller amount of work had been performed. End-exercise ADP concentration was lower. On recovery, the initial rate of phosphocreatine resynthesis was low. Skeletal muscle bioenergetics were within normal limits in those in heart failure. In the myocardium, the phosphocreatine/ATP ratio was similar in controls and hypoxaemic subjects, but low in those in heart failure. Conclusions-In heart failure, the myocardial phosphocreatine/ATP ratio was reduced, as in adults, while resting skeletal muscle studies were normal. By contrast, hypoxaemic children had normal myocardial bioenergetics, but showed skeletal muscle alkalinity, and energy reserves were more readily depleted on exercise. On recovery, the initially slow phosphocreatine resynthesis rate reflects a low rate of mitochondrial ATP synthesis, probably due to an inadequate oxygen supply. 31P MRS offers a safe, non-invasive method of studying myocardial and skeletal muscle bioenergetics in children as young as 5 months. (Heart 1996;75:614-619)

Opiates are also recommended to facilitate ventilation, and pethidine (a synthetic opiate) is extensively used in our unit. Though it may produce transient orthostatic hypotension, studies have shown no effect on heart rate or blood pressure in supine unanaesthetised adults,4 though a reduction in both was seen in anaesthetised patients.5 We know of no relevant published reports concerning neonates.We have investigated the possible adverse cardiovascular effects of these commonly used drugs and their influence on blood pressure instability using data recorded on a microcomputer. Patients and methodsThirty two infants admitted to the neonatal unit at Royal Postgraduate Medical School, Hammersmith this hospital were enrolled in the study. All were being ventilated for respiratory distress syndrome and had an umbilical artery catheter in the thoracic aorta (Neocath Biomedical Sensors Ltd, High Wycombe, Buckinghamshire). None had received any drug except vitamin K and no colloid had been given in the hour preceding the study; skin perfusion, capillary filling, and urine output indicated normovolaemia. Procedures likely to affect the measurements were not carried out in the 15 minutes before, or during the study time of 20 minutes. The infants were each given a first dose of either pancuronium (0-1 mg/kg) or pethidine (standard analgesic dose 1*0 mg/kg) to assist ventilation after independent assessment by house officers, the study being complete when there were 16 consecutive infants in each group. The mean weight of those receiving pancuronium was 1100 g (range 640-2500) and the mean gestational age was 28 weeks (range 25-33). In the group receiving pethidine the mean weight was 1000 g (range 480-1800) and mean gestational age 28 weeks (range 25-31