The continuous measurement of cerebrospinal fluid gas tensions in critically ill neurosurgical patients: a prospective observational study

Objective:To determine the feasibility and usefulness of continuous cerebro spinal fluid pH and gas tension monitoring in critically ill neurosurgical patients. Design: Prospective, observational study. Setting: Neurosurgical intensive care unit in a teaching hospital. Patients: Five critically ill neurosurgical patients (GCS < 8) requiring in tensive care intracranial pressure monitoring and intermittent positive pre ssure ventilation. Interventions: Placement of a Paratrend 7 sensor into the external ventricu lar drain. Measurements and main results: The cerebrospinal fluid (CSF) pH, PCO2 and P O2 were recorded at 1-min intervals. Intracranial pressure (ICP) and cerebr al perfusion pressure (CPP) were recorded at 15-min intervals. The mean bas eline CSF pH O-2 and PO2 values were 7.28 +/- 0.08 pH units, 44 +/- 6 torr and 43 +/- 27 torr, respectively. The ranges of CSF pH, PCO2 and PO2 observ ed during the study were 6.3-7.8 pH units, 37-150 torr and 4-150 torr, resp ectively. A statistically significant correlation between ICP, CPP and CSF gas tensions occurred in patient 3. Significant changes in CSF PO, and pH w ere observed with augmentation of CPP and preceded clinical improvement in patient 4. There were no complications attributable to sensor placement. CS F gas tensions and pH value obtained from patients 3 and 3 suggest that the se measurements may be an indicator of cerebral perfusion. Conclusions: Continuous CSF gas tension measurements in critically ill pati ents are possible and may be an indicator of adequacy of cerebral perfusion . The relative merits and limitations of the technique are discussed.