Effect of thoracotomy upon the carotid sinus control of regional hemodynamics in the dog.

The effects of bilateral thoracotomy upon the operating characteristics of the carotid sinus reflex were examined in 11 vagotomized dogs. Pressure-flow relationships in the aorta, celiac, mesenteric, renal, and femoral arteries were studied as a function of pressure in the isolated carotid sinuses. These relationships were analyzed to give the carotid sinus reflex operating point values and sensitivities of pressure, flow, impedance, and power for each regional vascular bed. Following thoracotomy there was a significant fall in the closed-loop operating point pressure (CLOP) ( p less than 0.005). The operating point values and sensitivities for each regional flow and resistance together with the corresponding mean and oscillatory kinetic and pressure power were not significantly altered by thoracotomy. Renal characteristic impedance at the operating point significantly increased following thoracotomy (p less than 0.05), as did the aortic characteristic impedance for carotid sinus pressures (CSP) above the closed-loop operating point. The operating sensitivity of renal characteristic impedance was decreased (p less than 0.05). Possible mechanisms underlying these changes are discussed.