Brain Death Scintigraphy using Tc-99m DTPA: Does Equivocal Cerebral Flow Matter?

Objective: To eliminate the “equivocal flow” group from brain death scintigraphy with Tc-99m DTPA by demonstrating that patients with equivocal cerebral flow will eventually fall in the brain death groups who have no cerebral flow. Methods: We retrospectively reviewed 100 consecutive cerebral perfusion studies requested for confirmation of brain death (100 patients) performed at the University of Wisconsin from October 2009 to December 2017. Two patients died before they could obtain the cerebral perfusion study and 4 patients had duplicate medical record numbers or perfusion studies, leaving a total of 94 evaluable patients. Patients were categorized into 3 groups: no cerebral flow present, equivocal cerebral flow present and cerebral flow present. Medical records were reviewed to determine if any patients with equivocal flow survived. Results: Of the 94 evaluable patients, 70 had no cerebral flow present, 16 had equivocal cerebral flow present and 8 had cerebral flow present. Ninety-three of 94 patients in all 3 groups were clinically declared brain dead by the neurointensivist team during the same hospital admission. Fifteen of 16 patients in the equivocal flow group were clinically declared brain dead within 48 hours of the brain death scintigraphic study. One patient with equivocal flow present had clinical care withdrawn and died prior to the completion of clinical brain death determination. There was no difference in the final outcome among the no flow and equivocal flow groups. Conclusions: All patients with equivocal flow died shortly after the cerebral perfusion study and thus the equivocal flow category and clinical uncertainty associated with it may be eliminated. Furthermore, given the lack of any false negative studies with Tc-99m DTPA, there may be no significant advantage to using the more expensive and logistically challenging cerebral perfusion agents Tc-99m HMPAO and Tc-99m ECD.