Critical cerebral perfusion pressure during tepid heart operations in dogs.
BACKGROUND
The management of blood pressure during cardiopulmonary bypass varies widely. This may be particularly relevant with the trend to warmer bypass temperatures and an older patient population. Therefore, we examined the minimal perfusion pressure that maintains cerebral oxygen delivery during cardiopulmonary bypass at 33 degrees C.


METHODS
Ten dogs were placed on bypass and body temperature was reduced to 33 degrees C (alpha-stat pH management). At six randomly ordered mean arterial blood pressures (35, 40, 45, 50, 60, and 70 mm Hg), cerebral blood flow, oxygen delivery, and metabolic rate were determined.


RESULTS
Cerebral oxygen delivery was stable if the mean arterial pressure was greater than or equal to 60 mm Hg. If mean arterial pressure was less than or equal to 50 mm Hg, cerebral oxygen delivery decreased, and at less than 45 mm Hg cerebral ischemia was seen.


CONCLUSIONS
In a dog without vascular disease, the brain becomes perfusion pressure-dependent at a mean arterial pressure of approximately 50 mm Hg. There is no leftward shift of the cerebral autoregulatory curve during bypass at 33 degrees C. Greater support of mean arterial pressure during "tepid" cardiopulmonary bypass is indicated in the current adult surgical population that is older and has vascular comorbidity.
Department of Anesthesiology, Mayo Foundation and Mayo Clinic, Rochester, Minnesota 55905, USA.
W
W
Plöchl
D J
DJ
Cook
T A
TA
Orszulak
R C
RC
Daly
D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology; D001921:Brain / Q000378:metabolism / Q000502:physiology; D002545:Brain Ischemia / Q000209:etiology / Q000503:physiopathology; D002245:Carbon Dioxide / Q000097:blood; D002315:Cardiopulmonary Bypass / Q000379:methods; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004285:Dogs; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007036:Hypothermia, Induced / Q000379:methods; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D011897:Random Allocation; D012449:Safety
D006454:Hemoglobins; D002245:Carbon Dioxide; D010100:Oxygen