Intercrural differences of arterial blood-pressure and blood-flow in new-born infants.

Intercrural systolic blood-pressure differences did not exceed 10 mmHg in 22 healthy infants who were term, pre-term or small for their gestational age (three); as measured simultaneously in both legs with 3-cm wide thigh cuffs and mercury-in-silastic strain gauges around the calves. In 13 infants with indwelling umbilical artery catheter and normal angiographic findings in both legs, blood-pressure differences were similarly low in a majority of the infants, but in three of these intercrural differences of 15-20 mmHg were found. Resting and submaximal arterial leg blood-flow, measured with venous occlusion plethysmography, showed larger intercrural differences than blood-pressure, and did not add further information. The results indicate that simultaneous systolic blood-pressure measurements in the legs, with strain gauge plethysmography, is a simple and risk-free noninvasive method, suitable, for example, for diagnosing thromboembolism in infants. An indwelling umbilical artery catheter seems to interfere very little with the arterial circulation in the catheterized leg.