Circulatory responses to hypocapnia in the anesthetized dog

• Published in: The American journal of physiology Vol. 208; no. 1; pp. 139 - 143
• Main Authors: Kontos, Hermes A, Mauck, H. Page, JR, Richardson, David W, Patterson, John L., JR
• Format: Journal Article
• Language: English
• Published: United States 01-01-1965
• Subjects: Blood Flow Velocity; Blood Gas Analysis; Carbon Dioxide; Dogs; Heart; Hyperventilation; Hypocapnia; Old Medline; Phenoxybenzamine; Physiology; Vascular Resistance; Vasomotor System; HEART; HYPERVENTILATION; PHYSIOLOGY; DOGS; EXPERIMENTAL LAB STUDY; PHENOXYBENZAMINE; BLOOD FLOW VELOCITY; VASCULAR RESISTANCE; CARBON DIOXIDE; BLOOD GAS ANALYSIS; VASOMOTOR SYSTEM
• ISSN: 0002-9513; 2163-5773
• DOI: 10.1152/ajplegacy.1965.208.1.139

1 Department of Medicine, Medical College of Virginia, Richmond, Virginia
The circulatory responses to hypocapnia were studied in 40 anesthetized dogs. Hypocapnia induced without a change in ventilation caused slight increase in limb vascular resistance in six dogs and decrease in one. Hypocapnia induced by hyperventilation caused increase in limb vascular resistance in six dogs and decrease in four. Following administration of phenoxybenzamine into the femoral artery, hypocapnia induced by either method invariably caused increase in limb vascular resistance (8 dogs). These results show that hypocapnia has a direct vasoconstrictor effect on limb blood vessels. In the intact limb this response may be opposed by vasodilator effects mediated through nerves. Hypocapnia induced without change in ventilation had no significant effect on cardiac output, systemic vascular resistance or arterial blood pressure (8 dogs). Hypocapnia induced by increased ventilation was associated with significant decreases in cardiac output and systemic arterial blood pressure and significant increase in systemic vascular resistance (9 dogs). These responses were probably related to the effects of increased intermittent positive pressure used to augment ventilation. Key Words: effect on limb blood flow • effect on limb vascular resistance • effect on cardiac output • effect on systemic vascular resistance • vasoconstriction
Submitted on May 4, 1964