MONITORING OF AUTOREGULATION USING LASER-DOPPLER FLOWMETRY IN PATIENTS WITH HEAD-INJURY

The authors studied 31 comatose head-injured patients to assess the cl inical usefulness of laser Doppler flowmetry (LDF) in continuous autor egulation monitoring. The LDF probes were placed on the surface of the cerebral cortex. Data on LDF, intracranial pressure (ICP), and arteri al blood pressure (ABP) were recorded and continuously entered into a computer. The data were broken down into multiple segments of 15 minut es' duration (epochs). Epochs showing rapid change in cerebral perfusi on pressure (CPP), change in CPP of less than 10 mm Hg, LDF values of less than five arbitrary units, and loss of ABP/ICP waveform were excl uded from further analysis. A linear relationship between LDF and CPP in individual epochs was used as an indicator of loss of autoregulatio n. The relationship between LDF and CPP changed with time, indicating improvement or deterioration in autoregulation. Longitudinal analysis of all the epochs measured in a patient revealed three patterns of pro gress: 1) intact autoregulation; 2) transient loss; and 3) persistent loss of autoregulation. All five patients with intact autoregulation h ad a good outcome. Ten patients experienced transient loss of autoregu lation; of these four had a good outcome, five were moderately disable d, and one was severely disabled. Transient impairment of autoregulati on did not always indicate poor outcome, provided the impaired autoreg ulation responded to treatment. In 11 patients who had persistent loss of autoregulation, nine died and two were severely disabled. In five cases the LDF probe lost contact with the cerebral cortex and no usefu l information was obtained. Real-time measurement of autoregulation us ing LDF and CPP monitors was achieved and the findings were related to outcome in these patients.