title: Oxygen transport during hemodilution in normoxic and hypoxic dogs treated with verapamil.
abstract: In order to determine the possible limitations of acute isovolemic hemodilution in patients taking verapamil, the various factors determining oxygen availability were analyzed in an animal experiment. Twenty-four anaesthetized dogs were subjected to a gradual isovolemic hemodilution. Six dogs received a bolus injection of 0.1 mg kg-1 of verapamil followed by 0.01 mg kg-1 min-1. In 12 dogs, mild hypoxic hypoxia was induced by ventilation with 16-17% oxygen; six of them also received verapamil. Six dogs served as a control group. In the latter, due to an increase in heart rate and stroke volume, oxygen availability in the clinically relevant range of hemodilution between HC 25 and 25% was maintained at 81% of its control value. In normoxic animals treated with verapamil, oxygen availability decreased more rapidly and was below the level of the control group once HC reached 25%. Mild hypoxic hypoxia alone did not reduce oxygen availability as much as its combination with verapamil. Even though the verapamil-induced reduction in oxygen availability was similar during normoxia and hypoxia, the sharp rise in serum lactate at HC levels below 35-30% in the hypoxic verapamil group was a sign of impairment of tissue oxygenation. Hematocrit levels below 35-30% and even moderate hypoxemia should be avoided whenever the cardiovascular response to hemodilution is influenced by verapamil.
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D004285:Dogs; D006400:Hematocrit; D006438:Hemodilution; D006439:Hemodynamics / Q000187:drug effects; D000860:Hypoxia / Q000139:chemically induced*; D007773:Lactates / Q000097:blood; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects*; D014700:Verapamil / Q000009:adverse effects*
chemical_list: D007773:Lactates; D014700:Verapamil; D010100:Oxygen