Propofol causes injection pain is still a common clinical unsolved problem. Mixing a small amount of lidocaine with propofol or injecting lidocaine in advance can reduce the pain caused by propofol injection. Using an air warmer to warm the arm can also reduce the pain caused by propofol injection. Investors suspect that treatment with a warming patch (covering the injection site) can also reduce the pain caused by propofol injection.

This is a single-center randomized controlled clinical study. Purpose of this study is to explore whether the coverage of the warming patch (for 5min before injection) can reduce the pain induced by propofol injection.

The patients included in the study were randomly divided into two groups. The group W used a warming patch to cover the injection site, and the group C used a cotton pad to cover the injection site. After 5 minutes of coverage, the propofol injection was induced, and the patient's complaint of pain (calling or arm withdrawal) during propofol injection was observed, and the patient's recall of the pain score during induction after the patient recovered. After the patients regained consciousness, the data of the two groups were compared to determine whether the use of the warming patch could reduce the pain caused by propofol injection.

Inclusion Criteria:

• No peripheral phlebitis
• No history of Raynaud's syndrome
• No history of smoking or alcoholism
• Body mass index BMI<28 kg/cm2

Exclusion Criteria:

• Refusal of anesthesia
• Previous injection pain caused by propofol
• Difficulty in exposing the veins on the back of the hand or difficulty in venipuncture
• Complained of pain after normal saline infusion.

180 days

The assessor did not know the grouping of the pain scores in memory, nor did he know the purpose of the warming patch.