This randomized, open clinical trial sought to compare the use of Midazolam and Dexmedetomidine during surgery in patients under regional anesthesia.

The primary objective was to determine the superiority of either drug during the intraoperative period regarding: 1- Depth of sedation and 2- incidence of complications.

Secondary objectives included the determination of superiority regarding the postoperative period.

For that, patients were randomized into two groups and sedated with either Midazolam or Dexmedetomidine.

This study was a randomized, open clinical trial.

Patients undergoing surgery under regional (neuraxial or brachial plexus block) anesthesia were randomly assigned into one of two groups.

Patients in one of the groups (called MDZ) were initially sedated with a 0.05mg/Kg bolus dose of Midazolam.

The ones in the other group (called DEX) were initially sedated with a loading dose of 1 µg/Kg of Dexmedetomidine over 10 minutes, followed by continuous infusion at 0.2 to 0.8 µg/Kg/h.

In order to achieve a Richmond Agitation-Sedation Scale (RASS) score between -3 and -1, the following breakthrough doses were used as necessary:

MDZ: 0.02 mg/Kg bolus dose of Midazolam plus 0.5µg/Kg bolus dose of Fentanyl DEX: 0.5µg/Kg bolus dose of Fentanyl

Depth of sedation and incidence of complications were recorded during surgery, in the Post Anesthesia Care Unit (PACU) and in the Ward for two days following surgery,

Inclusion Criteria:

• Undergoing surgery under regional anesthesia

Exclusion Criteria:

• The presence of any Bradyarrhythmia;
• New York Heart Association (NYHA) Functional Classes III and IV Heart Failure and/or Left Ventricle Ejection Fraction under 30%;
• Respiratory Failure, Glasgow Coma Scale score 8 or under, and Liver Failure - due to the increased risk of sedation in patients with these conditions (d) refusal to participate in the study or withdrawal of consent at any moment.