The purpose of this pilot study was to determine the cerebral blood flow velocity and resistance changes and vital signs following a painful stimulus in the premature infant.
A convenience sample of 12 infants was randomly assigned to one of 2 treatment groups. In the final analysis, there were 10 infants younger than 24 hours of age and between 25 and 32 weeks' gestational age.
A randomized 2-period, 2-group, crossover design was used.
Cerebral blood flow velocity and resistance were measured via a Doppler head ultrasound transducer placed over the anterior fontanel. Vital signs were measured with a cardiorespiratory monitor. The infant then received the heel stick procedure or the sham procedure (heel preparation with no heel puncture). Each infant served as his or her own control. After each procedure, there was ultrasound and vital sign measurement at 15, 60, 120, 180, 240, and 300 seconds. Thereafter, the alternate treatment was used and 6 more measurements were taken.
MAIN OUTCOME MEASURES
Cerebral values: peak systolic velocity (PSV) and resistive index (RI); vital signs: heart rate, respiratory rate, oxygen saturation (SpO2), and blood pressure.
Treatment groups were similar at baseline except for gestational age. There were no carryover or period effects in the crossover design for the primary outcomes except for SpO2. There was a significant group effect (heel stick compared with sham) (P = .009) for peak systolic velocity; however, there were no significant differences between groups at each time point. Two subjects had a distinctive pattern based on simultaneous changes in flow and resistance: when flow velocity increased, resistance decreased. This may be reflective of risk for intraventricular hemorrhage (IVH). Mean arterial blood pressure (MAP) was not significant. However, heart rate was significantly different between stick and sham at 15 seconds (P = .022); respiratory rate was significant at 180 seconds (P = .029); and SpO2 was significant at 3 different time points. There were no significant correlations between PSV and mean arterial blood pressure and PSV and SpO2 when comparing stick to sham.
This is a study based on a small sample size. However, the Doppler-measured peak systolic velocity increases significantly after a painful stimulus. The clinical implication of this finding needs to be established.