1. Patients aged 18 years and above, ASA classification I-IV, BMI 18.5-29.9, planning to undergo forearm or hand surgery.
2. Diagnostic criteria: Patients who meet the internationally recognized diagnostic criteria for uremia and require hemodialysis.
3. Informed consent: Patients or their legal representatives must sign an informed consent form, agreeing to participate in this study and undergo related examinations and treatments.

1. According to the Propensity Score Matching (PSM) design for the control group, select patients aged 18 years or older, ASA classification I to IV, matched with patients in the U group in terms of age, gender, and BMI within the corresponding group, who are planned to undergo forearm or hand surgery. In addition to possibly having diabetes, patients should not have any other diseases that could cause peripheral neuropathy.
2. Informed consent: Similar to the uremic patient group, an informed consent form must be signed.

Adjust the neural stimulator, with a stimulation duration of 0.1 ms, a stimulation frequency of 1Hz, and a stimulation current of 1.0mA. Under ultrasound guidance, the needle tip is used to touch the radial nerve, ulnar nerve, median nerve, and musculocutaneous nerve respectively, until a clear motor response is observed in the corresponding muscles. Thereafter, the minimum stimulation threshold current is verified by reducing the current until the distal motor response disappears. If no motor response is elicited, the current intensity is appropriately increased to achieve a motor response of the extensor tendon of the radial nerve, and the flexor tendon motor responses of the ulnar nerve, median nerve, and musculocutaneous nerve.

Under ultrasound guidance, using a high-frequency linear array transducer and a dedicated nerve stimulation needle, the nerves are localized in-plane technique under direct visualization. Adjust the nerve stimulator with a stimulation duration of 0.1 ms, a stimulation frequency of 1Hz, and a stimulation current of 1.0mA. Under ultrasound guidance, the needle tip is used to touch the radial nerve, ulnar nerve, median nerve, and musculocutaneous nerve respectively, until a clear motor response is observed in the corresponding muscles. Thereafter, the minimum stimulation threshold current is verified by reducing the current until the distal motor response disappears. If no motor response is elicited, the current intensity is appropriately increased to achieve motor responses of the extensor tendon of the radial nerve, and the flexor tendons of the ulnar nerve, median nerve, and musculocutaneous nerve.

Testing the time for cold sensation disappearance using alcohol swabs