Synergistic effect of carotid compression and adenosine on cardiac rhythm to prolong flow arrest during intracranial aneurysm surgery.

Adenosine-induced transient cardiac asystole is used in intracranial aneurysm surgery to achieve flow arrest and facilitate clipping, particularly when proximal control is unavailable. Inadequate asystole duration or refractory responses can limit its utility, especially during intra-operative rupture. We describe a 48-year-old man with subarachnoid haemorrhage from a ruptured left supraclinoid internal carotid artery aneurysm and an unruptured right supraclinoid aneurysm. Both were approached via single left craniotomy. After uneventful clipping of the left aneurysm, clipping of the right aneurysm was attempted with 12 mg and 18 mg of adenosine, resulting in brief (8 s and 11 s, respectively) periods of asystole. During the rupture, carotid compression combined with 24 mg adenosine achieved asystole lasting 30 s with return of electrical activity only upon release of carotid compression, enabling safe clipping within 25 s of asystole onset. Hypotension persisted for an additional 60 s, after which the patient fully recovered. Combining mechanical carotid compression with adenosine synergistically prolonged asystole beyond that expected from adenosine alone, likely via enhanced parasympathetic effects on sino-atrial and atrioventricular nodes.