Delay in cooling negates the beneficial effect of mild resuscitative cerebral hypothermia after cardiac arrest in dogs: a prospective, randomized study.
OBJECTIVE
Previously, we documented that mild hypothermia (34 degrees C) induced immediately with reperfusion after ventricular fibrillation cardiac arrest in dogs improves functional and morphologic cerebral outcome. This study was designed to test the hypothesis that a 15-min delay in the initiation of cooling after reperfusion would offset this beneficial effect.


METHODS
Prospective, randomized, controlled study.


METHODS
Animal intensive care unit.


METHODS
A total of 22 custom-bred coonhounds.


METHODS
Eighteen dogs underwent normothermic ventricular fibrillation arrest (no blood flow) of 12.5 mins, reperfusion with brief cardiopulmonary bypass, defibrillation within 5 mins, intermittent positive-pressure ventilation to 20 hrs, and intensive care to 96 hrs. Three groups of six dogs each were studied: group 1, normothermic controls; group 2, core temperature 34 degrees C from reperfusion to 1 hr; and group 3, delayed initiation of cooling until 15 mins after normothermic reperfusion, and 34 degrees C from 15 mins to 1 hr 15 mins after cardiac arrest.


RESULTS
Tympanic membrane temperature (which represented brain temperature) in group 2 reached 34 degrees C at 6 +/- 3 (SD) mins after reperfusion; and in group 3 at 29 +/- 1 mins after reperfusion. Best overall performance categories achieved (1, normal; 5, brain death) compared with group 1, were better in group 2 (p < 0.5) but not in group 3 (NS). Similar results were found with best neurologic deficit scores (0%, normal; 100%, brain death), i.e., 44 +/- 4% in group 1, 19 +/- 15% in group 2 (p < .01), and 38 +/- 9% in group 3 (NS). Total brain histologic damage scores (< 30 minimal damage; > 100 severe damage), however, were 150 +/- 32 in group 1, 81 +/- 13 in group 2 (p < .001 vs. group 1), and 107 +/- 17 in group 3 (p < .05 vs. group 1).


CONCLUSIONS
Mild, resuscitative cerebral hypothermia induced immediately with reperfusion after cardiac arrest improves cerebral functional and morphologic outcome, whereas a delay of 15 mins in initiation of cooling after reperfusion may not improve functional outcome, although it may slightly decrease tissue damage.
Kuboyama
K
K
International Resuscitation Research Center (IRRC), University of Pittsburgh School of Medicine, PA.
Safar
P
P
Radovsky
A
A
Tisherman
S A
SA
Stezoski
S W
SW
Alexander
H
H
D000818:Animals; D001784:Blood Gas Analysis; D001786:Blood Glucose / Q000032:analysis; D001831:Body Temperature; D001925:Brain Damage, Chronic / Q000145:classification / Q000209:etiology* / Q000473:pathology; D002315:Cardiopulmonary Bypass; D003422:Critical Care; D004195:Disease Models, Animal; D004285:Dogs; D004554:Electric Countershock; D006323:Heart Arrest / Q000097:blood / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D006400:Hematocrit; D007036:Hypothermia, Induced / Q000379:methods*; D007385:Intermittent Positive-Pressure Ventilation; D008297:Male; D011379:Prognosis; D011897:Random Allocation; D012151:Resuscitation / Q000379:methods*; D012720:Severity of Illness Index; D013997:Time Factors; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000150:complications* / Q000628:therapy
D001786:Blood Glucose