Authors: P M Lewis J V Rosenfeld R R Diehl H M Mehdorn E W Lang
Publish Date: 2008/01/23
Volume: 150, Issue: 2, Pages: 139-147
Abstract
Background Impairment of cerebral autoregulation is known to adversely affect outcome following traumatic brain injury TBI The phase shift PS method of cerebral autoregulation CA assessment describes the time lag between fluctuations in arterial blood pressure ABP and cerebral blood flow velocity CBFV in the middle cerebral artery An alternative method MxABP is based on the statistical correlation between ABP and CBFV waveforms over time We compared these two indices in a cohort of severely head injured patients undergoing controlled 6breathsperminute ventilationMethods PS and MxABP were calculated from 33 recordings of CBFV and MAP in 22 patients with TBI Spearman’s correlation coefficient was used to assess the agreement between PS and MxABP The relationship between ICP slow wave amplitude MAP slow wave amplitude and mean ICP was also examinedFindings Mean values for MxABP and PS were 044 ± 027 and 49 ± 26 degrees respectively PS correlated significantly with MxABP r = −0648 p 0001 A BlandAltman plot of normalised MxABP and Phase Shift values showed no significant bias or relationship mean difference = 00004 r = −0037 p = 0852 During the test procedure ICP fluctuated in an approximately sinusoidal fashion with a mean amplitude of 496 ± 272 mmHg peak to peak The magnitude of ICP fluctuation during deep breathing correlated weakly but significantly with mean ICP r = 0391 p 005 and with the amplitude of ABP fluctuations r = 0625 p 00005
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