Therapeutic administration of thoracic epidural anesthesia reduces cardiopulmonary deterioration in ovine pulmonary embolism

Objective: It was hypothesized that sympathetic blockade restricted to the thoracic levels and achieved by,thoracic epidural anesthesia might be capable of reducing hemodynamic deterioration after pulmonary artery embolism and that this might represent a potential method of treatment in patients with pulmonary embolism. Cardiopulmonary function after pulmonary embolism was therefore studied in sheep, either without a sympathetic blockade (the control group) or with sympathetic blockade. Design: Prospective, randomized laboratory investigation. Setting: University research laboratory. Subjects: Twelve adult, chronically instrumented Blackhead ewes. Interventions. Pulmonary embolization was achieved by injecting autologous blood clots (0.75 mL/kg) intravenously into an external jugular vein. The treatment group (n = 6) received 6 mL of 0.175% bupivacaine and the control group (n = 6) received 6 mL of 0.9% NaCl 90 mins after the embolization procedure. The injections were made via an epidural catheter (at the level of T3). Results were considered to be statistically significant (with analysis of variance) at p <.05. Measurements and Main Results. After epidural administration of bupivacaine in the thoracic epidural anesthesia group, the mean pulmonary artery pressure and heart rate were significantly reduced and the stroke volume index was significantly higher in comparison with the control group, in which the animals received epidural injections of saline. Conclusions. Thoracic epidural anesthesia administered after the occurrence of pulmonary artery embolism thus significantly reduces hemodynamic deterioration in awake, spontaneously breathing sheep and may represent an additional option in the treatment of pulmonary embolism.