Combined effects of bilateral thoracic sympathectomy and hypercarbia on common carotid blood flow volume in dogs

ABSTRACT

BACKGROUND: The occurrence of acute hypercarbia during endoscopic thoracic sympathectomy is not rare when CO2 gas is used to collapse lung. Upper thoracic sympathectomy can increases cerebral blood flow (CBF) and hypercarbia also increases CBF. The purpose of this study was to analyze the changes in common carotid blood flow volume (CCBFV) before and after T2 thoracic sympathectomy at normocarbia and hypercarbia. METHODS: In nine anesthetized and mechanically ventilated dogs, we checked CCBFV using an ultrasonic flow probe under four experimental conditions 1) before T2 sympathectomy at normocarbia, 2) before T2 sympathectomy at hypercarbia, 3) after T2 sympathectomy at normocarbia, and 4) after T2 sympathectomy at hypercarbia. We also measured heart rate, blood pressure and PaCO2 at each time. RESULTS: Hypercarbia increased CCBFV from 105.2 +/- 47.9 ml/min to 192.3 +/- 85.4 ml/min. In T2 sympathectomy/normocarbia state, CCBFV increased to 152.2 +/- 62.0 ml/min. In T2 sympathectomy/hypercarbia state, CCBFV increased to 230.2 +/- 100.1 ml/min. CCBFV in hypercarbia state, sympathectomy state and sympathectomy/hypercarbia state showed significant increases compared with those in baseline (P < 0.05). CCBFV in hypercarbia state and sympathectomy/hypercarbia state showed significant increases compared with those in sympathectomy state (P < 0.05). But CCBFV in hypercarbia state and sympathectomy/hypercarbia did not showed significant differences. CONCLUSIONS: This result suggests that hypercarbia increases CCBFV more than sympathetic denervation and thoracic sympathectomy under hypercarbia condition increases CCBFV more than sympathectomy only.