Hemodynamics among neonates with hypoxic-ischemic encephalopathy during whole-body hypothermia and passive rewarming.
OBJECTIVE
To assess changes in cardiac performance, with Doppler echocardiography, among newborns with hypoxic-ischemic encephalopathy during mild therapeutic hypothermia and during rewarming.


METHODS
For 7 asphyxiated neonates (birth weight: 1840-3850 g; umbilical artery pH: 6.70-6.95) who received mild whole-body hypothermia, the following hemodynamic parameters were determined immediately before rewarming (33 degrees C) and during passive rewarming (35 degrees C and 37 degrees C): heart rate, systolic and diastolic blood pressure, core and peripheral temperatures, left ventricular ejection time, mean velocity of aortic flow, stroke volume, and cardiac output.


RESULTS
Heart rate decreased during hypothermia. Bradycardia, with heart rates below 80 beats per minute, did not occur. The median difference between core and peripheral temperatures decreased from 2.0 degrees C (range: 0-6.2 degrees C) during hypothermia to 0.7 degrees C (range: 0.4-1.9 degrees C) at normothermia. Cardiac output was reduced to 67% and stroke volume to 77% of the posthypothermic level. The median heart rate was 129 beats per minute before rewarming and increased to 148 beats per minute during complete rewarming. Before and during passive rewarming, hypotension was not observed. Before, during, and at the end of rewarming, the following parameters increased: mean velocity of aortic flow (median: 44, 55, and 58 cm/second, respectively), stroke volume (median: 1.42, 1.55, and 1.94 mL/kg, respectively), and cardiac output (median: 169, 216, and 254 mL/kg per minute, respectively). Left ventricular ejection time remained unchanged.


CONCLUSIONS
Whole-body hypothermia resulted in reduced cardiac output, which reached normal levels at the end of passive rewarming, at normothermia. Physiologic cardiovascular mechanisms seemed to be intact to provide sufficient tissue perfusion, with normal blood lactate levels.
Gebauer
Corinna Mirjam
CM
Department of Neonatology, Children's Hospital, University of Leipzig, Leipzig, Germany. corinna.gebauer@kksl.uni-leipzig.de
Knuepfer
Matthias
M
Robel-Tillig
Eva
E
Pulzer
Ferdinand
F
Vogtmann
Christoph
C
D001238:Asphyxia Neonatorum / Q000150:complications / Q000503:physiopathology / Q000628:therapy; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002302:Cardiac Output; D015150:Echocardiography, Doppler; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D007036:Hypothermia, Induced; D020925:Hypoxia-Ischemia, Brain / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D007231:Infant, Newborn; D016032:Randomized Controlled Trials as Topic; D017694:Rewarming; D013318:Stroke Volume