Introduction

The diagnosis of brain death (BD) is based on clinical criteria including deep coma, brain stem areflexia and apnoea. Depending on different local guidelines, confirmatory technical tests are sometimes mandatory.1 Since the 1990s, transcranial Doppler sonography (TCD) has found its place in these circumstances and fulfils most of the criteria of an ‘ideal test’ in confirming BD. To confirm intracranial circulatory arrest (CA) with Doppler sonography, typical flow patterns must be recorded in bilateral intracranial and extracranial brain-supplying arteries.2 A completely absent intracranial flow signal is not a reliable sign to determine CA because this can be due to transmission problems. Inadequate ultrasound penetration of the temporal bone is a major drawback of this technique, making definitive assessment of intracranial flow patterns impossible. Stabilised microbubble ultrasonic contrast agents (UCA) are routinely used in neurological clinical routine when intracranial insonation is difficult. The application of UCAs may also be helpful during BD declaration, but to our knowledge, only one publication evaluated UCAs to detect intracranial CA in BD.3