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NEUROSURGICAL ANESTHESIA

Cerebral Hemodynamic Responses to Blood Pressure Manipulation in Severely Head-Injured Patients in the Presence or Absence of Intracranial Hypertension

Olaf L. Cremer, MD MSc^*,, Gert W. van Dijk, MD PhD, Gerrit J. Amelink, MD PhD, Anne Marie G. A. de Smet, MD^*, Karel G. M. Moons, PhD^*,, and Cornelis J. Kalkman, MD PhD^*

*Division of Perioperative Care and Emergency Medicine, Departments of Neurology and Neurosurgery, and the Julius Center for Health Sciences and Primary Care, University Medical Center, Utrecht, The Netherlands

Address correspondence and reprint requests to Olaf L. Cremer, MD, MSc, University Medical Center, Department of Anesthesiology, E03.511, PO Box 85500, 3508 GA Utrecht, The Netherlands. Address e-mail to o.l.cremer{at}anest.azu.nl

The management of cerebral perfusion pressure (CPP) remains a controversial issue in the critical care of severely head-injured patients. Recently, it has been proposed that the state of cerebrovascular autoregulation should determine individual CPP targets. To find optimal perfusion pressure, we pharmacologically manipulated CPP in a range of 51 mm Hg (median; 25th–75th percentile, 48–53 mm Hg) to 108 mm Hg (102–112 mm Hg) on Days 0, 1, and 2 after severe head injury in 13 patients and studied the effects on intracranial pressure (ICP), autoregulation capacity, and brain tissue partial pressure of oxygen. Autoregulation was expressed as a static rate of regulation for 5-mm Hg CPP intervals based on middle cerebral artery flow velocity. When ICP was normal (26 occasions), there were no major changes in the measured variables when CPP was altered from a baseline level of 78 mm Hg (74–83 mm Hg), indicating that the brain was within autoregulation limits. Conversely, when intracranial hypertension was present (11 occasions), CPP reduction to less than 77 mm Hg (73–82 mm Hg) further increased ICP, decreased the static rate of regulation, and decreased brain tissue partial pressure of oxygen, whereas a CPP increase improved these variables, indicating that the brain was operating at the lower limit of autoregulation. We conclude that daily trial manipulation of arterial blood pressure over a wide range can provide information that may be used to optimize CPP management.

IMPLICATIONS: To determine optimal cerebral perfusion pressure (CPP) after severe head injury, we pharmacologically manipulated CPP between 51 and 108 mm Hg. We found that the brain was within autoregulation limits when intracranial pressure was normal, whereas it was operating at the lower threshold of autoregulation when intracranial hypertension was present.

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