Since its introduction in 1973, etomidate has been widely used in clinical anaesthesia, especially in haemodynamically unstable patients, as a new anaesthetic induction drug with the advantage of low circulatory and respiratory depression. When administered via intravenous injection, etomidate can cause adverse effects such as injection pain and myoclonus. The incidence of myoclonus is still reported to be as high as 50-80%. Myoclonus caused by etomidate may cause discomfort during induction of anaesthesia and reduce perioperative satisfaction, and may lead to syringe dislodgement, extravasation of the injected drug, swelling at the injection site, delayed induction of anaesthesia and, in severe cases, cardiovascular adverse events. Therefore, the myoclonus and limb retraction reactions caused by etomidate are a key concern for clinical anaesthesiologists and need to be addressed at a time when comfort anaesthesia is being promoted. The aim of this study was to reduce myoclonus produced by etomidate injection during induction of general anaesthesia in surgical patients and to investigate the half effective dose of remifentanil to reduce etomidate myoclonus.

Inclusion Criteria:

1. Ages ranged from 18 to 80.
2. ASA # or # level.

Exclusion Criteria:

• Allergy or contraindication to remifentanil or rocuronium; required for Central venipuncture catheterization;
• Abnormal liver or kidney function;
• Heavy drinking and long-term use of sedatives, analgesics or anti-anxiety drugs;
• Hearing and language impairment;
• Peripheral vascular disease;
• Severe cardiovascular disease or neurological disorders;
• Failure of one-time peripheral venipuncture;
• Infection of hand or wrist skin.