Pleuropulmonary and cardiovascular consequences of thoracoscopy performed in healthy standing horses

Six healthy, awake, and pharmacologically restrained mature horses were stu died in order to define the changes in cardiopulmonary function during and after exploratory thoracoscopy and to determine the presence of postoperati ve complications occurring 48 hours after thoracoscopy. In a randomised 3 x 3 latin square design with 2 replications, 18 procedures were performed: 6 right (RTH) and 6 left thoracoscopies (LTH) and 6 sham procedures (STH), P rior to each procedure a physical examination and bronchoalveolar lavage fl uid analysis were performed, During thoracoscopy and sham protocols, horses were sedated with a continual drip of detomidine HCl and data were collect ed at 6 time intervals: T1 (baseline), T2 (10 min detomidine administration ), T3 (first 15 min pneumothorax), T4 (5 min recovery from pneumothorax), T 5 (second 15 min pneumothorax), and T6 (10 min recovery from the second pne umothorax and detomidine), An endoscopic thoracic examination was conducted during the 2 pneumothorax periods. An identical protocol was followed for sham procedures without surgery or pneumothorax, Data mere analysed by ANOV A,with time and surgical procedure as main factors. Physical examinations, thoracic radiography and ultrasound, CBC and bronchoalveolar lavage fluid a nalysis were performed 48 h after thoracoscopy. Heart rate, respiratory rate, and cardiac output decreased following detomi dine administration. There was a trend for cardiac output to be lower durin g thoracoscopy, Mild systemic hypertension was associated with thoracoscopy although there was no effect on pulmonary arterial pressure. Total and pul monary vascular resistances were increased following detomidine administrat ion. Thoracoscopy caused a further increase in systemic and pulmonary vascu lar resistances especially during the second pneumothorax, Arterial O-2 ten sion decreased following detomidine administration and was further decrease d during the second pneumothorax period. PaO2 values were lower when thorac oscopy was performed on the left rather than the right hemithorax. No signi ficant complications were found during the 48 h follow-up evaluation. A sub clinical postoperative pneumothorax occurred in 2 horses, one of which had sustained a lung laceration by the trocar, Thoracoscopy performed in health y, awake, and pharmacologically restrained horses did not have detrimental cardiopulmonary effects and did not cause postoperative complications withi n the first 48 h period.