Pulmonary complications, which are occasionally severe, are common adverse events following the administration of clazosentan. This study aimed to identify factors associated with severe pulmonary adverse events due to clazosentan after aneurysmal subarachnoid hemorrhage (aSAH).

We conducted a retrospective study of 59 patients transported to our hospital and diagnosed with aSAH between April 2022 and May 2023.

The analysis included 33 patients who were treated with clazosentan. Pulmonary complications occurred in 20 patients (61 %) and clazosentan administration was discontinued due to severe pulmonary complications in 7 patients (21 %). The cardiothoracic ratio on admission was significantly higher (57 % vs. 49 %, p = 0.0081) and clazosentan was initiated earlier after aSAH onset (42 vs. 66 h, p = 0.047) in patients who discontinued clazosentan compared with patients who completed administration of clazosentan. The median duration of clazosentan administration was 3.2 days in the discontinuation group. No significant associations were found between the time of clazosentan initiation and the incidence of angiographic vasospasm, delayed cerebral ischemia, or 90-day modified Rankin scale.

The risk of severe pulmonary complications is higher in patients with high cardiothoracic ratios on admission, and delaying clazosentan initiation may prevent pulmonary complications even in high-risk cases.