Use of transcranial Doppler in patients with severe traumatic brain injury
KeywordsMechanical Ventilation Traumatic Brain Injury Emergency Medicine Cerebral Blood Flow Middle Cerebral Artery
Secondary ischemic insult after severe traumatic brain injury (TBI) is correlated with poor outcome. Transcranial Doppler sonography (TCD) permits a non-invasive measurement of cerebral blood flow. The purpose of this study is to determine the usefulness of TCD in patients with severe TBI.
TCD was performed on 73 patients with severe TBI, defined as a Glasgow Coma Scale of 8 or less on admission. All patients were on mechanical ventilation. TCD was performed on hospital days 1, 2, 3 and 7. Hypoperfusion was defined by having two out of three of the following: mean velocity of the middle cerebral artery less than 35 cm/second, diastolic velocity of the middle cerebral artery less than 20 cm/second and a pulsatility index greater than 1.4. Vasospasm was defined by the following: mean velocity of the middle cerebral artery greater than 120 cm/second and/or Landegaard index greater than 3.
Thirty-four patients (64%) had normal measurements. Thirteen were discharged home, 16 were discharged to a long-term care facility and five died. Two of these patients were comatose and their families requested withdrawal of care. The other three died from brain death. Eighteen patients (25%) had hypoperfusion and all 18 progressed to brain death. Twenty-one patients (29%) had vasospasm. Four of these patients were discharged home, 11 to a long-term care facility and six died. The vasospasm was detected on hospital day 1 in three patients, hospital day 2 in seven patients, hospital day 3 in four patients and hospital day 7 in seven patients. Nimodipine was administered in six patients and all six were discharged to a long-term care facility. However, in one patient, nimodipine caused hemodynamic instability and was discontinued. In 15 patients, nimodipine was not given. Six of these patients expired from brain death. Twelve of 21 patients (57%) with subarachnoid hemorrhage on computed tomography had vasospasm.
Most patients with normal measurements can be expected to survive. Patients with hypoperfusion have a poor prognosis. In patients with vasospasm, the use of nimodipine should be considered; however, further studies are needed to determine safety and efficacy. TCD may be useful in determining early prognosis. Further studies are also needed to determine whether TCD can improve outcome in patients with severe TBI.