Hemodynamic Responses to Hypoxia and Hypercapnia during Acute Normovolemic Hemodilution in Anesthetized Cats
The Japanese Journal of Physiology
Systemic changes in arterial blood gas evoke many cardio-respiratory responses mediated by central and or peripheral chemoreceptors  . Hypoxia causes cardiac depression in patients with acute hypoxemic respiratory failure  and depression in myocardial tissue and isolated hearts    . Hypercapnia decreases myocardial contractility. Gudipati et al.  and Planta et al.  have suggested that respiratory acidosis contributes to cardiovascular dysfunction and mortality. Acute
... ality. Acute respiratory acidosis (pH 7.09, PCO 2 92 mmHg) decreases left ventricular contractility, increases end systolic volume in anesthetized dogs  and causes left ventricle (LV) contractile dysfunction accompa-nied by an increased oxygen cost of contractility  . The fall in myocardial contractility during respiratory acidosis is only partially blocked by the adrenergic activation. Stein and Ellsworth  observed that, under the conditions of a severely limited oxygen supply resulting from a combined effect of acute fall in hematocrit and hypoxic ventilation, a diffusion limitation for oxygen resulting from the kinetics of oxygen release from the hemoglobin molecule provides an advantage for oxygen exchange within the capillary network. They suggested that oxygen content rather than PO 2 might be a critical determinant of oxygen supply at low levels of oxygen delivery.