Latin American consensus on the use of transcranial Doppler in the diagnosis of brain death

Abstract

Transcranial Doppler evaluates cerebral hemodynamics in patients with brain injury and is a useful technical tool in diagnosing cerebral circulatory arrest, usually present in the brain-dead patient. This Latin American Consensus was formed by a group of 26 physicians experienced in the use of transcranial Doppler in the context of brain death. The purpose of this agreement was to make recommendations regarding the indications, technique, and interpretation of the study of transcranial ultrasonography in patients with a clinical diagnosis of brain death or in the patient whose clinical diagnosis presents difficulties; a working group was formed to enable further knowledge and to strengthen ties between Latin American physicians working on the same topic. A review of the literature, concepts,and experiences were exchanged in two meetings and via the Internet. Questions about pathophysiology, equipment, techniques, findings, common problems, and the interpretation of transcranial Doppler in the context of brain death were answered. The basic consensus statements are the following: cerebral circulatory arrest is the final stage in the evolution of progressive intracranial hypertension, which is visualized with transcranial Doppler as a "pattern of cerebral circulatory arrest". The following are accepted as the standard of cerebral circulatory arrest: reverberant pattern, systolic spikes, and absence of previously demonstrated flow. Ultrasonography should be used - in acceptable hemodynamic conditions - in the anterior circulation bilaterally (middle cerebral artery) and in the posterior (basilar artery) territory. If no ultrasonographic images are found in any or all of these vessels, their proximal arteries are acceptable to be studied to look for a a pattern of cerebral circulatory arrest.

Figure 1

Consensus process.

Figure 2

A 19-year-old patient with asthma who experienced a cardiac arrest during an asthma attack; she was resuscitated via CPR. Admission GCS was 4 with initial brainstem reflexes; over 12 days, the Doppler pattern deteriorated, with all clinical neurological activity disappearing. The initial sonogram revealed normal flow velocity, evolving to slowing velocity, and cerebral circulatory arrest. Tomographic image post-CPR demonstrates diffuse anterior ischemia, as noted by the contrast "white cerebellum".

Figure 3

Two repeated studies over time in a patient with clinical brain death. In the top row, the left central sonogram and the center belong to the first study; the other sonograms belong to the second study. MCA - middle cerebral artery; R - right; L - left. The right middle cerebral artery (left sonogram of the top row) shows normal velocity and pulsatility blood flow, and continuous flow during the arterial pulse. These findings rule out rules out the diagnosis of cerebral circulatory arrest. The left middle cerebral artery (central sonogram of the top row) demonstrates a reverberating flow pattern, but a unilateral finding does not constitute cerebral circulatory arrest of the three sectors needed to support a diagnosis of brain death. After repeating the test (the remaining 4 sonograms), the flow pattern of the right middle cerebral artery has worsened; a unidirectional peak occupies approximately half of the cycle (systolic peak), these sonograms are not systolic spikes, because their duration is longer. The reverberant pattern in the left middle cerebral artery persists, showing lower velocities. The basilar artery has a shimmering pattern. The right vertebral artery exhibits systolic peaks with some ipsilateral flow during diastole. Together, these sonograms do not constitute a pattern of cerebral circulatory arrest of the three territories; thus, the right middle cerebral artery visualization should be repeated. When corroborating reverberating flow in the basilar artery, the vertebral artery should not be included in the assessment because the distal vessel provides sufficient evidence of the hemodynamic status of each sector studied.

Figure 4

A 65-year-old male patient with chronic atrial fibrillation, anticoagulation, cerebellar infarction with hemorrhagic transformation, hydrocephalus, external shunt, fever, venous sinus thrombosis, and multiple bilateral infarcts. GCS 3 without brainstem reflexes and without sedation for 24 hours. Mean arterial pressure 100mmHg. Transcranial Doppler does not demonstrate temporal window sonograms. Reverberating flow and systolic spikes at the right (1) and left (2) carotid syphon and basilar artery (not shown) are consistent with the diagnosis of brain death.

Figure 5

Algorithm demonstrating the different routes to reach the diagnosis of cerebral circulatory arrest in a patient with a clinical diagnosis of brain death or factors that prevent or hinder the clinical diagnosis. SAP - systolic arterial pressure; MAP - mean arterial pressure; TCD - transcranial Doppler; CCA - cerebral circulatory arrest.