Arm and leg blood pressures--are they really so different in newborns?

Controversy still exists over differences between upper and lower limb blood pressures (BP) in neonates. We measured upper arm and calf systolic (S) and diastolic (D) BP and heart rate (HR) using 2 Dinamap 847 instruments simultaneously every half minute for several measurement periods of 5-10 min. Nine healthy term newborns were studied in active (AS) and quite (QS) sleep on post-natal days 1 and 5. The results were examined using unbalanced analyses of variance. Arm SBP was 62.3 +/- 1.6 mmHg and DBP 35.5 +/- 1.0 mmHg on day 1 in AS and QS. Calf values were not significantly different but were slightly higher (by 2-3 mmHg) in AS. Arm SBP and DBP rose by 8.5 and 5 mmHg, respectively, between days 1 and 5 but calf pressures rose less. Calf SBP and DBP were significantly lower (by 4.6 and 3.4 mmHg, respectively) than the arm values in QS on day 5. Arm SBP and DBP were dependent on post-natal age but not on sleep state while calf SBP and DBP and HR were dependent on both. Mean HR rose with age from 114 to 117.6 bpm in QS and from 118.6 to 122.4 bpm in AS. Our non-invasive BP measurements were similar to available invasive data. We postulate that differences in arm and calf vasoreactivity account for the different dependence on sleep state and for the unequal changes in arm and calf BE from days 1 to 5.