Purpose: Decisions regarding the need for volume replacement in neonates often are made in the immediate newborn period. Capillary refill time (CRT) is used as an indicator of circulatory status; however, recent data show that CRT varies considerably with age, ambient and skin temperature, anatomical site of measurement, and duration of pressure. The purpose of this study was to (1) examine the relationship between CRT and heart rate (HR) and blood pressure (BP) in term neonates, and (2) evaluate the differences among CRT values measured at 3 body sites and with varying duration of cutaneous pressure.
Design: This was a prospective, cross-sectional, correlational study. Subjects Forty-two appropriate-weight-for-gestational-age (AGA) neonates with birthweights, (M = 3407; SD = +/- 540 g), gestational ages (M = 39 weeks; SD = +/- 1 week), and sex (21 males, 21 females). Infants had no history of perinatal distress or maternal chorioamnionitis.
Methods: Each neonate was studied prospectively 1 to 4 hours after birth. The infants were clothed with only a diaper and evaluated on a radiant warmer bed set to achieve an axillary temperature of 36.5 degrees to 37.0 degrees C. Capillary refill time was measured with a digital stopwatch at 3 sites: volar surface of finger (F), plantar surface of heel (H), and lower sternum (St), using brief (1- to 2-second) and extended (3- to 4-second) pressure. Heart rate was auscultated and counted for 60 seconds, and BP was measured by oscillometry. Relationships among variables were assessed by Pearson correlation coefficient, analysis of variance, and multiple regression analysis. The Bonferroni correction for multiple comparisons was applied.
Main outcome measures: Capillary refill time, blood pressure, and heart rate.
Principal results: There was no significant site variation for CRT for either brief (2.4 +/- 0.6 to 2.9 +/- 1.0 seconds) or extended (3.8 +/- 0.8 to 4.3 +/- 0.8 seconds) pressure. However, regardless of site, CRT was greater when extended versus brief pressure was used (P < 0.001). There were no significant correlations between HR and CRT. There was a moderate, direct relationship between BP and CRT observed in the following anatomic sites: (1) sternum/extended pressure and systolic BP (SBP), diastolic BP, and mean BP (r = 0.35, P = 0.02; r = 0.49, P = 0.001; and r = 0.43, P = 0.005, respectively); (2) sternum/brief pressure and SBP (r = 0.31, P = 0.05); and (3) finger/extended pressure and SBP (r = 0.30, P = 0.05).
Conclusions: An unanticipated moderate, direct correlation between BP and CRT was observed; prolongation of CRT occurred with elevated blood pressure. This finding may have been secondary to increased circulating vasoactive substances in the newborn period; measurement of these substances was beyond the scope of this study. In addition, CRT was highly dependent on the duration of cutaneous pressure, regardless of the site. These 2 findings indicate that CRT may be an unreliable indicator of cardiovascular status in the term neonate during the first 4 hours after birth.