Prevention of delayed cerebral infarction (DCI) due to cerebral vasospasm after subarachnoid haemorrhage (SAH) has been done with intravenous Rho kinase inhibitors (ROCKI), ozagrel sodium (TXA2I), selective ROCKI infusion (ROCKI i.a.), and cerebrospinal fluid (CSF) drainage. The endothelin receptor antagonist (ERA, clazosentan) became available in 2022 and is said to be highly recommended for DCI prevention, while fluid retention such as pleural effusion and pulmonary oedema accumulation is often experienced. We investigated the relationship between patient background, fluid retention, and ERA. Ten consecutive SAH patients treated with ERA from July to December 2022 were included. We examined the results of blood sampling on admission, echocardiography, chest computed tomography (CT), with postoperative DCI, and hydrocephalus requiring cerebrospinal fluid shunt (hydro), and symptomatic fluid retention requiring albumin and furosemide (third fluid space). Two males and eight females, mean age 63 years, mean preoperative World Federation Neurosurgical Surgeons (WFNS) grade 3.5, mean creatinine 0.94, mean brain natriuretic peptide (NT-proBNP). In 1883, two patients with Takotsubo cardiomyopathy and four patients with neurogenic pulmonary oedema are present. All patients underwent coil embolisation, and postoperative CSF drainage, ROCKI, TXA2I systemic administration, and ROCKI i.a. There were one DCI, three hydro, and five third fluid cases. Concerning the third fluid, the only significant difference was found in the age. An improvement in fluid retention after ERA discontinuation in old patients was shown. Our experience suggests that age may be the most influential factor. Based on these results, we have also found that by avoiding the use of ERA in patients older than 80 years, strictly limiting the infusion volume when using ERA, and actively using the drugs for heart failure early on, the frequency of suffering from third fluid space is reduced.