Introduction: Although inflating tracheal cuff using lidocaine is effective for cough suppression, it may pressure tracheal cuff too much. Intravenous continuous infusion of lidocaine has emerged recently for most general anesthesia in the context of opioid-sparing anesthesia for cancer, but the 95% effective dose (ED95) for cough suppression during anesthesia emergence is not determined yet. Objective: the objectives of this study are to determine the ED95 of continuous infusion lidocaine for suppressing cough reflex during extubation by sex and age group.

Ideal patient weight in kg will be considered.

Initial dose will be 0.5mg/kg.h and dose-change steps of 0.5mg/kg.h will occur depending on the incidence of emergence cough in the previous patient of the same group:

• It will increase if coughed in a probability of 95%
• It will decrease if not coughed in a probability of 5%.
• It will remain the same otherwise. Maximum dose will be 3mg/kg.h. All patients will receive remifentanil 0.025mcg/kg.min continuous infusion until extubation.

Patients groups will be determined by sex and age group (18-60 or >60 years old), therefore, four independent groups will be studied:

• Female 18 to 60 years old
• Male 18 to 60 years old
• Female > 60 years old
• Male > 60 years old

Inclusion Criteria:

• Understands study risks and benefits, signs informed consent.
• Not pregnant.
• Not an airway surgery
• No acute or chronic respiratory disease.
• Non smoker
• No chronic cough

Exclusion Criteria:

• Any protocol violation.

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In a year following the study

Open

A study participant who will not participate during assessment of the main outcome will prepare the drug solutions to be infused at 10ml/h accordingly to the response of the previous patient and to the dose calculated for the next patient. The participant who will verify the main outcome during anesthesia emergence will not know the dose the patient is receiving. Participants will not be informed of the dose they will receive. The outcomes assessor will not handle individual data and statistical analysis plan was developed in advance.