Changes of cardiovascular regulation during rewarming in newborns undergoing whole-body hypothermia.

OBJECTIVES: The aim of the study was to determine changes of oxygenation and cardiovascular parameters during body temperature recovery in newborns undergoing therapeutic hypothermia.

DESIGN AND SETTINGS: Three full-term newborns treated by whole-body hypothermia according to TOBY trial were included in the study. They were cooled to body temperature of 33.5 °C for 72 hours, thereafter gradual rewarming was initiated. During rewarming period following parameters were measured: heart rate and heart rate variability, blood pressure, core body temperature, blood oxygen saturation, cerebral and splanchnic tissue oxygenation. In one of the infants Doppler sonography examination of truncus coeliacus and arteria mesenterica superior was performed to assess blood flow in these arteries.

RESULTS: During rewarming period the heart rate increased, whereas blood pressure tended to decrease. It was observed ascending trend in parameters of heart rate variability (MSSD and total spectral power) due to increasing spectral activity in LF and also HF bands. Blood oxygen saturation and cerebral tissue oxygenation remained stable, but significant decrease of splanchnic tissue oxygenation was noticed. This finding corresponded to Doppler sonography parameters in arteria mesenterica superior.

THE MAIN FINDING: Therapeutic hypothermia and subsequent rewarming in newborns influenced cardiovascular regulation (blood pressure, heart rate, heart rate variability). Body temperature recovery was accompanied by reduction in splanchnic oxygenation and blood flow in superior mesenteric artery.

CONCLUSIONS: Body temperature recovery in neonates led to changes in autonomic cardiovascular regulation resulting in redistribution of blood flow to vital organs. Reduction of blood flow to splanchnic organs during heating is a finding that has not been described yet. Further studies are needed to confirm these findings.