K. Oku et al., MILD HYPOTHERMIA AFTER CARDIAC-ARREST IN DOGS DOES NOT AFFECT POSTARREST MULTIFOCAL CEREBRAL HYPOPERFUSION, Stroke, 24(10), 1993, pp. 1590-1597
Background and Purpose: Although mild resuscitative hypothermia (34-de
grees-C) immediately after cardiac arrest improves neurological outcom
e in dogs, its effects on cerebral blood flow and metabolism are unkno
wn. Methods: We used stable xenon-enhanced computed tomography to stud
y local, regional, and global cerebral blood flow patterns up to 4 hou
rs after cardiac arrest in dogs. We compared a normothermic (37.5-degr
ees-C) control group (group I, n=5) with a postarrest mild hypothermic
group (group II, n=5). After ventricular fibrillation of 12.5 minutes
and reperfusion with brief cardiopulmonary bypass, the ventilation, n
ormotension, normoxia, and mild hypocapnia were controlled to 4 hours
after cardiac arrest. Group II received (minimal) head cooling during
cardiac arrest, followed by systemic bypass cooling (to 34-degrees-C)
during the first hour of reperfusion after cardiac arrest. Results: Th
e postarrest homogeneous transient hyperemia was followed by global hy
poperfusion from 1 to 4 hours after arrest, with increased ''no-flow''
and ''trickle-flow'' voxels (compared with baseline), without group d
ifferences. At 1 to 4 hours, mean global cerebral blood flow in comput
ed tomographic slices was 55% of baseline in group I and 64% in group
II (NS). No flow (local cerebral blood flow <5 mL/100 cm3 per minute)
occurred in 5 +/- 2% of the voxels in group I versus 9 +/- 5% in group
II (NS). Trickle flow (5 to 10 mL/100 cm3 per minute) occurred in 10
+/- 3% voxels in group I versus 16 +/- 4% in group II (NS). Cerebral b
lood flow values in eight brain regions followed the same hyperemia-hy
poperfusion sequence as global cerebral blood flow, with no significan
t difference in regional values between groups. The global cerebral me
tabolic rate of oxygen, which ranged between 2.7 and 4.5 mL/100 cm3 pe
r minute before arrest in both groups, was at 1 hour after arrest 1.8
+/- 0.3 mL in normothermic group I (n=3) and 1.9 +/- 0.4 mL in still-h
ypothermic group II (n=5); at 2 and 4 hours after arrest, it ranged be
tween 1.2 and 4.2 mL in group I and between 1.2 and 2.6 mL in group II
. Conclusions: After cardiac arrest, mild resuscitative hypothermia la
sting I hour does not significantly affect patterns of cerebral blood
flow and oxygen uptake. This suggests that different mechanisms may ex
plain its mitigating effect on brain damage.