INTRACRANIAL-PRESSURE WAVE-FORM INDEXES IN TRANSIENT AND REFRACTORY INTRACRANIAL HYPERTENSION

Analysis of data obtained by continuous computerized monitoring of int racranial pressure (ICP) in 109 adult patients with severe head trauma was performed to examine the patterns of change in indices of the ICP waveform. Indices derived from direct measurement of the ICP wave and obtained from a Fast Fourier Transform (FFT) were examined. Concurren t physiologic measurements were made. Two types of intracranial hypert ension (ICH) were defined for comparison. 'Transient intracranial hype rtension' occurred when an abrupt rise in ICP was followed by a return to below 25 mm Hg (n = 63). Increases in ICP that were progressive an d led to neurologic deterioration and death were termed 'refractory in tracranial hypertension' (n = 18). During transient ICH heart rate, ar terial pressure, end-tidal carbon dioxide and jugular venous oxygen sa turation all increased, while these measures either were unchanged or decreased during refractory ICH. The pulse amplitude of the ICP wave i ncreased in both types of ICHtn. Other changes in the waveform indices were consistent with this change in pulse amplitude. HFC responded di fferently to the two types of changes, with an increase during the tra nsient changes and a decrease during the refractory changes. The diffe rences in changes in physiologic measurements as ICH occurred in the 2 groups suggest that in refractory ICH cerebral blood flow is maintain ed against the mounting ICP, while in transient ICH the hypertension i s caused by an increase in cerebral blood flow. The waveform indices d o not discriminate between the two types of changes.