Noninvasive Monitoring of Cerebral Blood Flow Autoregulation in Patients With Traumatic Brain Injury (TBI)

BACKGROUND: The brain is very sensitive to both excessive and insufficient flow of blood. Cerebral blood flow (CBF) is normally auto-regulated by the blood vessels in the brain, but this protective mechanism is often disturbed after a traumatic brain injury (TBI). Impairment or loss of the CBF autoregulation makes the brain vulnerable to oscillations of either arterial blood pressure (ABP) or intracranial pressure (ICP). The ideal management of TBI patients, therefore, involves continuous measurement and management of the cerebral perfusion pressure (CPP = ABP - ICP) but the measurement of CPP is currently possible only with specialized equipment and expertise that is not available in all institutions. The investigators have converted a no-longer used system that continuously monitors CBF autoregulation using rheoencephalography (REG) technology into a modern, small, battery-powered, low-cost monitor (aka BM-1) that acquires the REG signals using only noninvasive electrodes placed on the skin/scalp. REG data can then be used to calculate the optimal CPP to maintain in each individual patient. BM-1 is also capable of monitoring electroencephalography (EEG) and impedance plethysmography (IPG), which can, respectively, be used to measure brain electrical activity and changes in peripheral blood flow caused by blood pressure changes.

OBJECTIVES: The primary objectives are to (Obj. 1) demonstrate that REG acquired noninvasively is equal to the well-established but invasive method using intracranial pressure (ICP) monitoring, (Obj. 2) retrospectively test the idea that TBI patients have a less favorable outcome if their CPP were found less optimal using the REG data, and (Obj. 3) determine if noninvasive IPG or the PPG finger sensor monitoring (used to measure heart rate in doctor's offices) can replace the invasive monitoring of arterial blood pressure (ABP).

METHODOLOGY: This is an observational study with retrospective data analysis. 20 adult patients (18-65 yrs) with acute TBI, who meet the inclusion/exclusion criteria, will be enrolled on a first-come-first-enroll basis. The enrolled patients will have the REG, EEG and IPG signals monitored for the duration of ICU stay or 15 days, whichever is shorter. Standard neurological assessment will be made at the patient's discharge from the ICU and at 3 months after injury. The study is expected to end June 2013.


Eligibility Criteria:
Inclusion Criteria:

* Clinical diagnosis of acute moderate or severe TBI
* Hospitalization within 12 hours from the injury
* Intraarterial catheterization and intracranial pressure (ICP) monitoring instantiated within 72 hours from the injury

Exclusion Criteria:

* Earlier head injuries, stroke, space-occupying intracranial lesions, meningitis, or cerebral vasculopathies
* Concomitant severe injuries of the chest, abdomen, pelvis, extremities or spine
* Concurrent terminal illness with a life expectancy of less than 6 months
* Unlikely to survive the next 48 hours after enrollment
* Implanted cardiac pacemaker, cardiac converter/defibrillator, or other electrical stimulator
* Pregnancy
* Patient is a prisoner or on a probation