Moderate hypothermia reduces hypotensive, but not hypercapnic vasodilation of pial arterioles in rats.
Two types of acid-base strategies are available for the blood gas management of patients during hypothermia: alpha-stat and pH-stat management. However, the more suitable strategy for therapeutic hypothermia is unclear. We studied the effects of hypothermia (30 degrees C) and acid-base management on reactivity to hypercapnia and hypotension in rat pial arterioles, using a closed cranial window. The baseline diameter during hypothermia decreased in the alpha-stat (PaCO2 was maintained at 35 mm Hg when measured at 37 degrees C, n = 8), but not in the pH-stat (PaCO2 was maintained at 35 mm Hg when corrected to the animal's actual temperature, n = 7). Vasodilation induced by hypotension was significantly reduced in hypothermic groups compared with the normothermic group (n = 7), whereas responses to hypercapnia were preserved. Moreover, hypotensive vasodilation was more attenuated in the pH-stat, than the alpha-stat, management. These findings show that moderate hypothermia and acid-base management alter cerebrovascular autoregulation.
Irikura
K
K
Department of Neurosurgery, Kitasato University School of Medicine, Kanagawa, Japan.
Miyasaka
Y
Y
Nagai
S
S
Yuzawa
I
I
Morii
S
S
Fujii
K
K
D000818:Animals; D001160:Arterioles / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D006863:Hydrogen-Ion Concentration; D006935:Hypercapnia / Q000503:physiopathology*; D007022:Hypotension / Q000503:physiopathology*; D007035:Hypothermia / Q000503:physiopathology*; D008297:Male; D010313:Partial Pressure; D010841:Pia Mater / Q000098:blood supply*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000502:physiology*
D002245:Carbon Dioxide