Intravenous morphine attenuates pain induced changes in skin blood flow in newborn infants

Abstract

In a previous study we found that pain and discomfort caused a marked increase in skin blood flow in newborn infants, and that skin blood flow decreased after morphine. In this study we tested morphine effect on the skin blood flow response to pain more systematically. Skin blood flow was measured using a laser Doppler technique during 19 percutaneous central venous catheter placements in 18 infants, 10 of whom received intravenous morphine premedication. The mean +/- SD baseline skin blood flow was similar between the two groups: 22.5 +/- 9.5 ml 100 g-1 min-1 in the morphine group, and 23.7 +/- 8.0 ml 100 g-1 min-1 in the no-morphine group, respectively (p = n.s.). During PCVC placement in the morphine treated group, skin blood flow remained low with minimal variability. The mean value was 22.6 +/- 7.7 ml 100 g-1 min-1 (p = n.s. compared to baseline). In 7/9 infants not treated with morphine skin blood flow increased dramatically during PCVC placement, while in two it did not. But the mean skin blood flow in this group of 9 infants during PCVC placement was 45.3 +/- 34 ml 100 g-1 min-1, an overall change of 97% increase from the baseline. This was statistically significant compared with the baseline and the morphine group value during PCVC insertion (p < 0.04). During the 45 min time period after PCVC placement, skin blood flow values between groups again were similar. We conclude that morphine pretreatment for PCVC placement minimizes pain-associated increases in skin blood flow. The issue of whether skin blood flow changes could serve as measures of adequate analgesia needs to be evaluated with further studies.