起搏后体位性低血压

观察7条狗起搏前后从卧位变为站位时的血流动力学变化。起搏后起立时平均动脉压平均下降28％,是正常时(13％)的二倍,并且恢复时间明显延长(P<0.01)。实验表明起搏前后狗的体位性低血压代偿机制不同,正常时起立时心输出量增加20％左右,心率平均增加24％,而每搏输出量在开始阶段常减少,有的在整个站立过程中减少。心率在提高心输出量,代偿体位性低血压中起着重要作用。起搏后由于心率固定不变,因而出现明显的体位性低血压。提高起搏频率可改善体位性低血压。

Orthostatic Hypotension in Dogs With ⅤⅥ Pacing

Hemodynamic changes from a prone to a standing position were studied in 7 dogs before and after ⅤⅥ pacing. Mean arterial blood pressure (MAP) decreased nearly two times as much in paced dogs (28％) as it did in normal dogs (13％) and the time during arterial blood pressure returned to prestanding level was longer (P<0.01). Results showed that the paced dogs differed from normal dogs in their compensation for the decreased pressure. The normal exhibited an elevation in heart rate (24％) and in cardiac output (20％) on standing, but there was a reduction in stroke volume (SV) during the initiation of standing and sometimes, a decrease in SV predominated throughout the period of boold pressure change, The heart rate played an important role in compensating for the large decrease in arterial blood pressure. Therefore, orthostatic hypotension was still showed in dogs paced with fixed pacing rate on standing and it could be improved by raising the pacing rate.