The effects of thoracotomy on coronary blood flow in the dog.

A velocity-sensitive catheter-tip flowmeter was used to measure left coronary arterial blood flow prior to, during, and following left lateral thoracotomy in the artificially ventilated dog anesthetized with sodium pentobarbital. Thoracotomy was performed with (six dogs) and without (10 dogs) the addition of an increased expiratory airway resistance. Opening the chest without the increased airway resistance had no effect on coronary blood flow, despite a fall in arterial pressure, because coronary vascular resistance decreased. This was associated with a fall in arterial PO2. Thoracotomy with the airway resistance in place caused a transient slight fall in coronary flow owing to decreased arterial pressure and increased coronary resistance. All changes disappeared by the twelfth minute. Arterial PO2 was unaffected. Under the conditions of this experiment, thoracotomy had surprisingly little effect on coronary blood flow.