Abstract
Epidural pressure (EDP) pulse waves in acute intracranial hypertension was clinically and experimentally analyzed in order to clarify the origin of the EDP pulse wave and its clinical significance.
The cases in this study included eight males and one female, ranging in age between 17 and 76 years, who were admitted with a diagnosis of hypertensive intracerebral hemorrhage, severe head injuries, or intracerebral hematoma caused by a ruptured cerebral aneurysm or a arteriovenous malformation. They were all operated on within 17 hours after the onset and manifested marked intracranial hypertension within several days after surgery. EDP was measured with an intracranial pressure (ICP) monitor system from the parietal extradural space on the operated side. Systemic blood pressure (BP) was simultaneously recorded from the radial artery with a pressure transducer in all instances. The fidelity of these pressure measuring systems was determined as acceptable. Both EDP and BP pulse waves were analyzed by measuring upstroke (U) time determined by the time from the rising point (S') in the ascending slope and the peak of a pulse wave, S'-C time determined as the time from S' to incisura (C) or dicrotic notch expressed as C in the descending slope of a pulse wave, and the pulse amplitude.
Recording of the pressure pulse waves of the internal carotid artery and the femoral artery as well as EDP pulse wave were carried out in five Japanese monkeys with acute intracranial hypertension produced by the epidural balloon method. Each component of the EDP pulse wave corresponded well with that of the BP pulse wave, when ICP was below 15 mmHg. But an increase in the amplitude of the EDP pulse wave was recorded with an elevation of ICP, and prolongation of U time in the EDP pulse wave was observed at EDP of 20 to 30 mmHg. The increase in the amplitude was most significant at EDP as high as 40 to 50 mmHg. In the experimental study, changes in EDP pulse wave-form observed in intracranial hypertension was in accord with that of the internal carotid artery showing an increase of the tidal wave.
These results indicated that the changes in the EDP pulse wave were induced mainly by changes in the intracranial hemodynamics and pressure transmission, secondary to intracranial hypertension. Thus, analysis of the EDP pulse wave can promote early detection of intracranial dynamic changes in intracranial hypertension.
