Variability of four limb blood pressure in normal neonates

To assess the variation in blood pressure (BP) between limbs in normal neonates. To assess whether comparison of arm and leg BP in neonates is reproducible enough to allow the difference to raise suspicion of coarctation of the aorta.

Infants recruited from the postnatal wards and the postnatal murmur clinic underwent echocardiography and BP measurement in each limb using a Dinamap Compact T 482210. The method of BP measurement was guided by a telephone survey of 40 UK neonatal units.

Forty healthy neonates underwent echocardiography and all had a normal aortic arch. BP was measured in 39. In three, BP in the arms was 20 mm Hg higher than in the legs. This gave a specificity of comparison of the upper and lower limb BPs of 92 (36/39) or a false positive rate of 8% (3/39). The standard deviation in BPs was 15.7 mm Hg between arms, 14.5 mm Hg between legs, and 11 mm Hg when the nearest arm and leg were compared.

With current measurement techniques, normal neonates may have a wide variation in BP between limbs. A difference of 20 mm Hg in isolation is more likely to be due to random variability in measurement than to coarctation of the aorta. If coarctation of the aorta is suspected, it can only be excluded or confirmed by echocardiography.