[Transcranial Doppler ultrasound use in post-cardiac arrest coma]

Brain damage is the most common cause of morbidity and mortality after initial recovery of a cardiac arrest.

To review the usefulness of transcranial Doppler ultrasonography (TCD) in monitoring and prognosis of comatose patients after initial recovery from cardiac arrest.

The TCD records the velocity and pulsatility of cerebral blood flow, allowing 'beat to beat' hemodynamic analysis, with the added value of not being interfered by the use of sedatives or therapeutic treatments such as moderate hypothermia. In patients who remain comatose two hours after being recovered from cardiac arrest, persistence in the cerebral arteries of a diffuse hypodynamic TCD pattern (low medium velocity and high pulsatility) also predicts poor neurologic recovery. Early or late presence of a diffuse hyperdynamic TCD pattern (high medium velocity and low pulsatility) is also associated with poor prognosis because progression to intracranial hypertension and brain death. Coincidence of hypodynamic arteries and other with normal or hyperdynamic TCD patterns, suggests foci of hypoperfusion that may be predictors of stroke.

Using serial TCD examinations in comatose patients after initial recovery from cardiac arrest, to detect and treat early changes in cerebral hemodynamics, will decrease the likelihood of secondary neurological damage. In the first 24 hours, TCD could identify patients who have progressed to irreversible neurological damage, thus avoiding therapeutic futility.