Thoracotomy is an uncommon procedure in horses but remains essential in a variety of cases of
pleuropneumonia,
pericarditis, thoracic
trauma or diaphragmatic herniation, and for experimental thoracic and cardiac procedures. This study aimed at developing an experimental
surgical procedure allowing access to the entire circumference of the heart and describing the effect of
thoracotomy on pulmonary gas exchange in these horses. The study consisted of two arms, arm one (undergoing
thoracotomy), was a terminal experimental study that included 11 Standardbred horses with experimentally induced (by tachypacing)
atrial fibrillation. Arm two consisted of 6 Standardbred horses undergoing
anesthesia for reasons unrelated to the present study. These horses functioned as controls.
Anesthesia was induced using
zolazepam and
tiletamine.
Anesthesia was maintained with
isoflurane in 100%
oxygen and ventilation with intermittent positive pressure (
IPPV); no
positive end-expiratory pressure (PEEP) was performed. Rib resection and
pericardiotomy were performed for complete exposure of the entire circumference of the heart. Arterial blood samples were collected prior to, 5 and 30 minutes after
puncture of pleura parietalis. In 10 horses, resection of the fifth rib was adequate for exposure of the heart. In one horse, removal of the sixth rib was also necessary. The duration of the
surgical procedure (
thoracotomy,
pericardiotomy) was < 45 minutes. During a
thoracotomy, PaO2 decreased significantly (P < .05) from 291.8 ± 82.8 mmHg to 165.2 ± 73.5 mmHg but was not different from normal anesthetized controls. The PaCO2 remained within normal limits. This surgical approach provided access to the entire circumference of the heart.