A 38-year-old man with pancreatic cancer was scheduled to undergo pancreaticoduodenectomy. He had an unremarkable past medical history. After inducing general anesthesia, a left radial arterial catheter was successfully placed at first attempt. A wrist splint was used to obtain good arterial pulse waveforms. After the operation, he was transferred to the intensive care unit. The radial artery catheter was removed on the fourth postoperative day. He experienced numbness and a tingling sensation in the left thumb, the second and third fingers, and the lateral half of the fourth finger. He was diagnosed with carpal tunnel syndrome. Diagnostic imaging revealed a swollen median nerve, but no hematoma or injury. Some studies have suggested that excessive extension of the wrist may cause neuropathy. We recommend that patients' wrists not be over-extended, even if good arterial waveforms cannot be obtained.