Prolonged mild hypothermia after experimental hypothermic circulatory arrest in a chronic porcine model.
OBJECTIVE
We sought to evaluate the potential efficacy of prolonged mild hypothermia after hypothermic circulatory arrest.


METHODS
Twenty pigs, after a 75-minute period of hypothermic circulatory arrest, were randomly assigned to be rewarmed to 37 degrees C (normothermia group) or to 32 degrees C and kept at that temperature for 14 hours from the start of rewarming (hypothermia group).


RESULTS
The 7-day survival was 30% in the hypothermia group and 70% in the normothermia group (P =.08). The hypothermia group had poorer postoperative behavioral scores than the normothermia group. Prolonged hypothermia was associated with lower oxygen extraction and consumption rates and higher mixed venous oxygen saturation levels during the first hours after hypothermic circulatory arrest. Decreased cardiac index, lower pH, and higher partial pressure of carbon dioxide were observed in the hypothermia group. There was a trend for beneficial effect of prolonged hypothermia in terms of lower brain lactate levels until the 4-hour interval and of intracranial pressure until the 10-hour interval. Postoperatively, total leukocyte and neutrophil counts were lower, and creatine kinase BB was significantly increased in the hypothermia group. At extubation, the hypothermia group had higher oxygen extraction rates and lower brain tissue oxygen tension.


CONCLUSIONS
A 14-hour period of mild hypothermia after 75-minute hypothermic circulatory arrest seems to be associated with poor outcome. However, the results of this study suggest that mild hypothermia may preserve its efficacy when it is used for no longer than 4 hours, but the potentials of a shorter period of postoperative mild hypothermia still require further investigation.
Romsi
Pekka
P
Department of Surgery, Oulu University Hospital, University of Oulu, Oulu, Finland.
Heikkinen
Janne
J
Biancari
Fausto
F
Pokela
Matti
M
Rimpiläinen
Jussi
J
Vainionpää
Vilho
V
Hirvonen
Jorma
J
Jäntti
Ville
V
Kiviluoma
Kai
K
Anttila
Vesa
V
Juvonen
Tatu
T
D000818:Animals; D001831:Body Temperature / Q000502:physiology; D001921:Brain / Q000098:blood supply* / Q000378:metabolism; D002245:Carbon Dioxide / Q000097:blood; D002315:Cardiopulmonary Bypass / Q000401:mortality; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003402:Creatine Kinase / Q000097:blood; D004195:Disease Models, Animal; D004569:Electroencephalography; D005260:Female; D006324:Heart Arrest, Induced / Q000401:mortality; D006439:Hemodynamics / Q000502:physiology; D007035:Hypothermia / Q000209:etiology* / Q000378:metabolism / Q000401:mortality; D007036:Hypothermia, Induced / Q000401:mortality; D008955:Models, Cardiovascular; D010100:Oxygen / Q000097:blood; D011183:Postoperative Complications / Q000209:etiology / Q000378:metabolism / Q000401:mortality; D011897:Random Allocation; D012720:Severity of Illness Index; D016019:Survival Analysis; D013552:Swine; D013997:Time Factors; D016896:Treatment Outcome
D002245:Carbon Dioxide; D003402:Creatine Kinase; D010100:Oxygen