Abstract
Since there has been reported a very few studies on the mechanism of the change in cardiac function after head injury, it was thought of interest to investigate this problem using the compression concussion model in adult dogs. After the anesthetization, the planzer system was set on the right temporo-parietal part of the head of the dog and fluid percussion was performed to the head extra-durally. The parameters such as mean blood pressure, aortic flow, left ventricular pressure, max left ventricular dp/dt, total peripheral resistance and electrocardiogram were recorded for 30 minutes after the percussion. The control animals were divided into two groups: one of them consisted of 8 animals and was given the percussion less than 2.5 atmosphere (C1 group), and the other consisted of 10 animals and was given percussion more than 2.6 atmosphere (C2 group) . The medication animals were divided into 3 groups as follows : AS group consisted of 6 dogs and was given 0.2 mg/kg of atropine sulfate, prop group consisted of 9 dogs and was given 0.15 mg/kg of propranolal and PUB group consisted of 6 dogs and was given 2 mg/kg of phenoxybenzamine. The results obtained were as follows : 1) Bradyarrhythmias were observed immediately after the percussion in C2, prop and PUB groups but prevented in AS group. However, the premature ventricular contraction and ventricular tachycardia were not prevented in AS group. 2) Mean blood pressure, left ventricular pressure, max left ventricular dp/dt and total peripheral resistance extremely increased in AS and prop groups, but slightly in PUB group. 3) In most of the cases, ventricular premature contraction and ventricular tachycardia were observed following the elevation of blood pressure, but they were not observed in PUB group in which the elevation of the blood pressure was rather slight. From these results, it is concluded that the excitation of the parasympathetic nervous system was deeply concerned with the change in the cardiac function observed immediately after the injury of the brain stem, and both systems of parasympathetic and sympathetic nerves, particularly the latter, were strongly concerned with the change thereafter.
