S ubarachnoid hemorrhage (SAH) from a ruptured aneurysm is accompanied by several complications, including electrolyte abnormalities, vasospasm, hydrocephalus, cardiac dysfunction, and pulmonary edema. 15,16,18 Among these complications, delayed cerebral ischemia (DCI) remains an important cause of morbidity and death. 15 Many studies have investigated the prevention or treatment of DCI after SAH.Triple-H therapy (i.e., hypertension, hypervolemia, and hemodilution) has reportedly been an effective approach abbreviatioNs CI = cardiac index; CRP = C-reactive protein; DCI = delayed cerebral ischemia; ELWI = extravascular lung water index; GEDI = global end-diastolic volume index; PVPI = pulmonary vascular permeability index; SAH = subarachnoid hemorrhage; SVRI = systemic vascular resistance index; WFNS = World Federation of Neurosurgical Societies. obJective Subarachnoid hemorrhage (SAH) is often accompanied by pulmonary complications, which may lead to poor outcomes and death. This study investigated the incidence and cause of pulmonary edema in patients with SAH by using hemodynamic monitoring with PiCCO-plus pulse contour analysis. methods A total of 204 patients with SAH were included in a multicenter prospective cohort study to investigate hemodynamic changes after surgical clipping or coil embolization of ruptured cerebral aneurysms by using a PiCCO-plus device. Changes in various hemodynamic parameters after SAH were analyzed statistically. results Fifty-two patients (25.5%) developed pulmonary edema. Patients with pulmonary edema (PE group) were significantly older than those without pulmonary edema (non-PE group) (p = 0.017). The mean extravascular lung water index was significantly higher in the PE group than in the non-PE group throughout the study period. The pulmonary vascular permeability index (PVPI) was significantly higher in the PE group than in the non-PE group on Day 6 (p = 0.029) and Day 10 (p = 0.011). The cardiac index of the PE group was significantly decreased biphasically on Days 2 and 10 compared with that of the non-PE group. In the early phase (Days 1-5 after SAH), the daily water balance of the PE group was slightly positive. In the delayed phase (Days 6-14 after SAH), the serum C-reactive protein level and the global end-diastolic volume index were significantly higher in the PE group than in the non-PE group, whereas the PVPI tended to be higher in the PE group. coNclusioNs Pulmonary edema that occurs in the early and delayed phases after SAH is caused by cardiac failure and inflammatory (i.e., noncardiogenic) conditions, respectively. Measurement of the extravascular lung water index, cardiac index, and PVPI by PiCCO-plus monitoring is useful for identifying pulmonary edema in patients with SAH.Clinical trial registration no.: UMIN000003794 (clinicaltrials.gov)http://thejns.org/doi/abs/10.3171/2015.6.JNS1519