CASE DESCRIPTION 4 dogs were examined because of pleural effusion and ventricular tachycardia, coughing and supraventricular tachycardia, appendicular osteosarcoma, and syncopal episodes.
CLINICAL FINDINGS In all 4 dogs, a heart base tumor was identified by means of thoracic CT.
TREATMENT AND OUTCOME In all 4 dogs, the heart base tumors were treated by means of stereotactic body radiation therapy. Dogs were anesthetized, and neuromuscular blockade was achieved with atracurium or vecuronium. A circle rebreathing system with 15 m (50 feet) of anesthetic tubing coursing through the vault wall was used to connect the patient to the anesthesia machine, which was located in the control room. After a brief period of hyperventilation, an inspiratory breath was held at 20 cm H2O for the duration of beam delivery. Each beam delivery lasted between 30 and 100 seconds. Immediately following the breath hold, assisted ventilation was resumed. Mean treatment delivery time for each patient was 26 minutes; mean total anesthesia time was 89 minutes. All patients recovered without complications. There was no evidence of hemoglobin desaturation or hypercapnia during the anesthetic procedure.
CLINICAL RELEVANCE The technique allowed for control of the respiration cycle from outside the radiation vault and a short overall treatment time. No adverse effects were encountered. This procedure should be considered when delivering radiation to structures within the thoracic cavity.