Cardiopulmonary Effects of Using Carbon Dioxide for Laparoscopic Surgery in Dogs

Cardiopulmonary effects of laparoscopic surgery were investigated in five crossbred dogs (21 ± 1.9 kg). Premedicated dogs were anesthetized with thiopental and maintained with halothane at 1.5 times minimum alveolar concentration in oxygen. Controlled ventilation maintained partial pressure of end-tidal co₂ at 40 ± 2 mm Hg. Vecuronium was used for skeletal muscle relaxation. After instrumentation and stabilization, baseline measurements were made of cardiac output (thermodilution technique), mean systemic, mean pulmonary arterial and pulmonary wedge pressures, heart rate, saphenous vein and central venous pressures, and minute ventilation. Baseline arterial and mixed venous blood samples were drawn for analysis of pH, Pao₂, Paco₂, Pvo₂, Pvco₂, and bicarbonate concentrations. Systemic and pulmonary vascular resistances, oxygen delivery and consumption, shunt fraction, and dead space ventilation were calculated using standard formulas. Abdominal insufflation using co₂ to a pressure of 15 mm Hg for 180 minutes resulted in significant ( P <.05) increases in heart rate (15 to 180 minutes), minute ventilation (75 to 135 minutes), and saphenous vein pressure (15 to 180 minutes), and decreases in pH (60 to 180 minutes) and Pao₂ (60 to 180 minutes). For 30 minutes after desufflation, there was a significant decrease in Pao₂, and increases in cardiac output, o₂ delivery, and heart rate, compared with baseline. There was a significant increase in shunt fraction and decrease in pH at 15 minutes after desufflation only. The changes were within physiologically acceptable limits in these healthy, ventilated dogs.