Cardiac Arrhythmias Accompanying Experimental Spinal Cord Trauma in Cats

ABSTRACT

This study was undertaken to determine the cardiovascular response to the spinal cord trauma in cats and to determine the autonomic mechnisms involved. The electrocardiogram and arterial blood pressure were recorded in anesthetized cats after the spinal cord trauma of 500 gm-cm at T4-T6 levels. 1. Acute spinal cord trauma caused a wide variety of severe cardiac arrhythmias and acute hypertension. 2. The increase of blood pressure could be prevented by intravenous phenoxybenzamine, and alpha adrenergic blocking agent. The pressor response was mediated by the alpha adrenergic receptor sites of the peripheral nervous system. 3. Tachycardia was occurred by the administration of atropine and bilateral vagotomy before trauma without affecting pressor response. 4. The arrhythmias could be eliminated by the combined administration of propranolol and atropine, but not prevented by the administration of either propranolol or atropine without affecting pressor response. These results suggest that the arrhythmias might be a response of hyperactivity of both sympathetic and parasympathetic divisions of the autonomic nervous system.