To determine the relative roles of cardiac receptors and arterial baroreceptors during blood loss, the effects of acute hemorrhage on measurements of mean arterial pressure, cardiac output, stroke volume, total peripheral resistance, and heart rate were examined in chronically instrumented, conscious dogs with all nerves intact (n = 15) and following either cardiac denervation (CD, n = 14), sinoaortic denervation alone (SAD, n = 11), or combined sinoaortic denervation plus cardiac denervation (SAD+CD, n = 8). Hemorrhage at a constant rate (0.5 ml/kg/min) was continued until mean arterial pressure fell to 40 mm Hg or 30 ml/kg of blood was withdrawn. hemorrhage (20 ml/kg) decreased mean arterial pressure similarly in the intact group (-15 ± 3.3 mm Hg) and CD group (-17 ± 3.2 mm Hg), but to a greater extent in the SAD (-53 ± 3.4 mm Hg) and SAD+CD (-49 ± 2.9 mm Hg) groups. Total peripheral resistance increased similarly in the intact (20.4 ± 3.0 mm Hg/l/min) and CD (22.4 ± 2.4 mm Hg/l/min) groups, but did not increase in SAD and SAD+CD groups. Acute cardiac denervation induced with intrapericardial lidocaine in either the intact or SAD groups resulted in similar responses of mean arterial pressure to hemorrhage as those observed in the chronic CD and chronic SAD+CD groups, respectively. Thus, dogs with cardiac denervation withstand hemorrhage and increase total peripheral resistance to a similar extent as intact dogs. When sinoaortic denervation is added to cardiac denervation or with sinoaortic denervation alone, increases in total peripheral resistance to hemorrhage are abolished and less blood loss is required to produce hypotension. These results suggest taht sinoaortic baroreceptors play a major role, whereas cardiac receptors are not important in regulating mean arterial pressure and total peripheral resistance during hemorrhage in conscious dogs.
All Science Journal Classification (ASJC) codes
- Cardiology and Cardiovascular Medicine
- Arterial baroreceptor reflex
- Arterial pressure
- Cardiac output
- Cardiopulmonary reflexes
- Peripheral resistance