title: Hemodynamics and metabolism during surface-induced hypothermia in the dog: a comparison of pH management strategies.
abstract: The management of blood pH during hypothermia remains controversial. The present study was designed to determine whether hemodynamics and oxygen consumption during hypothermia are different between the alpha-stat and pH-stat strategies. Theoretical considerations of enzyme kinetics suggest that the alpha-stat strategy would result in a higher oxygen consumption during hypothermia. Because hypothermia is used to decrease oxygen consumption for protection during ischemia, a pH scheme that results in a greater oxygen demand for any level of ischemia would be detrimental. The core temperature of 22 dogs was lowered to 26 degrees C by combined surface cooling and gastric irrigation. Either the alpha-stat (N = 9) or the pH-stat (N = 13) pH strategy was used. The arterial pressure was different between the two groups at 26 degrees C (65 +/- 6 vs 85 +/- 6 mm Hg, alpha-stat vs pH-stat, respectively, P less than 0.05). Neither systemic oxygen consumption nor the Q10 was different between groups. There were no differences in any other hemodynamic parameters. In summary, during moderate hypothermia alpha-stat pH management results in an arterial pressure lower than that of pH-stat management, possibly resulting in improved peripheral perfusion. Despite theoretical predictions, the alpha-stat pH scheme does not result in an oxygen consumption higher than that of the pH-stat scheme.
authors.affiliation: Surgery Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: J A
authors.initials: JA
authors.lastname: Swain
authors.forename: T J
authors.initials: TJ
authors.lastname: McDonald
authors.forename: R C
authors.initials: RC
authors.lastname: Robbins
authors.forename: V A
authors.initials: VA
authors.lastname: Hampshire
mesh_terms: D000818:Animals; D004285:Dogs; D006439:Hemodynamics; D006863:Hydrogen-Ion Concentration; D007036:Hypothermia, Induced; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D010101:Oxygen Consumption
chemical_list: D007773:Lactates; D019344:Lactic Acid