Transcranial Doppler during suspected brain death in children: Potential limitation in patients with cardiac "shunt".

OBJECTIVES: We report a potential limitation of transcranial Doppler for assessing cerebral circulation during suspected brain death in children. DESIGN: Review of two case series identified during our clinical practice. PATIENTS: Eight children with suspected brain death and seven with intact-brain and cardiovascular anomalies. MEASUREMENTS AND MAIN RESULTS: Brain-death criteria included lack of cerebral-brainstem reactivity, electrocortical silence and absent blood flow by brain scintigraphy ((99m)Tc-hexamethylpropylenamine oxime). Five intracranial Doppler patterns were found in eight cases of suspected brain death: A) orthograde continuous flow; B) reduced systolic flow velocity with absence of diastolic flow; C) reduced systolic flow velocity with retrograde diastolic flow, sometimes with antegrade late diastolic flow; D) systolic spikes of very low flow velocity; and E) absence of Doppler signals. Only patterns "C," "D," and "E" were associated with the absence of supra- and infratentorial brain perfusion. The most common Doppler alterations in patients with intact-brain and cardiovascular anomalies were the absence of diastolic flow (pattern "B") or the presence of retrograde flow during diastole (pattern "C"). CONCLUSION: Transcranial Doppler monitoring of pediatric patients may have value in identifying patients who have severe cerebral compromise, who may progress to brain death. However, key Doppler alterations, such as absent or retrograde flow during diastole, are not uniquely associated with the diagnosis of brain death, particularly in the setting of congential heart disease. The use of conventional methodology for the diagnosis of brain death in infants and children remains the "gold standard."