Pre-hospital transcranial Doppler

The SAMU (Service d’aide médicale urgente) guys have had a run of interesting pre-hospital publications lately. In this study, one of their ultrasound-wielding physicians travelled in a car to meet comatose head injured patients in a large semi-rural territory area with up to a 120–160-min transport time to a hospital with emergency neurosurgical capability. Pre-hospital transcranial Doppler was done, the results of which appear to have influenced treatment decisions, including the pre-hospital administration of noradrenaline (norepinephrine). I think this study has answered the ‘can it be done?’ question, but further work is needed to determine whether it really makes a difference to outcome.

Background: Investigation of the feasibility and usefulness of pre-hospital transcranial Doppler (TCD) to guide early goal-directed therapy following severe traumatic brain injury (TBI).
Methods: Prospective, observational study of 18 severe TBI patients during pre-hospital medical care. TCD was performed to estimate cerebral perfusion in the field and upon arrival at the Level 1 trauma centre. Specific therapy (mannitol, noradrenaline) aimed at improving cerebral perfusion was initiated if the initial TCD was abnormal (defined by a pulsatility index >1.4 and low diastolic velocity).
Results: Nine patients had a normal initial TCD and nine an abnormal one, without a significant difference between groups in terms of the Glasgow Coma Scale or the mean arterial pressure. Among patients with an abnormal TCD, four presented with an initial areactive bilateral mydriasis. Therapy normalized TCD in five patients, with reversal of the initial mydriasis in two cases. Among these five patients for whom TCD was corrected, only two died within the first 48 h. All four patients for whom the TCD could not be corrected during transport died within 48 h. Only patients with an initial abnormal TCD required emergent neurosurgery (3/9). Mortality at 48 h was significantly higher for patients with an initial abnormal TCD.
Conclusions: Our preliminary study suggests that TCD could be used in pre-hospital care to detect patients whose cerebral perfusion may be impaired.

Pre-hospital transcranial Doppler in severe traumatic brain injury: a pilot study
Acta Anaesthesiol Scand. 2011 Apr;55(4):422-8

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