Background Transurethral resection of the prostate (TUR-P) could incidentally cause hyponatremia, known as TUR syndrome due to intravascular absorption of non-electrolytic irrigation fluid. Recently, normal saline has been used as an irrigation fluid in a new system named TURis (TUR in saline) to prevent TUR syndrome. However, rapid massive absorption of normal saline can also cause other systemic adverse events. Case presentation A 71-year-old man underwent TURis for benign prostatic hyperplasia under spinal anesthesia. The patient lost consciousness which led upper airway obstruction and hypoxia 30 min after the surgery began. Blood gas test indicated hyperchloremic metabolic acidosis. While vasoactive agents were ineffective, the administration of bicarbonate significantly improved the symptoms and restored blood pressure. Conclusion We experienced a case of hyperchloremic metabolic acidosis with decreased level of consciousness and hypotension during TURis. Administration of bicarbonate, but not phenylephrine, was effective for recovering blood pressure.