Does the Preoperative Midazolam Dose Affect Postoperative Pain?

Does the Preoperative Midazolam Dose Affect Postoperative Pain? - a Multicentric Randomized Controlled Trial in Ambulatory Surgery

To investigate whether midazolam has any effect on postoperative pain in outpatient surgery, the investigators will assess the impact of different midazolam doses on pain scores 24h, 7 days and 3 months after ambulatory surgery. The investigators hypothesize that patients being administered higher midazolam doses will refer more pain.

Systemic midazolam prescribed perioperatively might have impact on pain, with studies suggesting antinociceptive and hyperalgesic effects. Anxiety might be a confounder in this association. In order to investigate the effect of midazolam on postoperative pain, a clinical trial will be conducted in Portuguese ambulatory surgery units. A convenience sample with consecutive design will include patients admitted for open inguinal hernia repair, varicose vein stripping, knee arthroscopy or hallux valgus surgery under spinal anesthesia. Patients will be randomized into 3 premedication groups, and this randomization will be stratified for each centre and each type of surgery. Postoperative pain will be blindly assessed by telephone interviews at 24h, 7 days, and 3 months. The investigators will use multiple regression models to explore the interaction of midazolam dose with preoperative anxiety, gender and chronic benzodiazepine use, as they hypothesize there might be a differential effect of midazolam on postoperative pain amongst these subgroups.

Assessed by the Brief Pain Inventory severity score (24h recall time): mean of 4 items assessing pain at the moment of the interview, on average, at its least and at its worst during the last 24h

Assessed by the Brief Pain Inventory severity score (24h recall time): mean of 4 items assessing pain at the moment of the interview, on average, at its least and at its worst during the last 24h. Features of neuropathic pain as assessed by DN4 patient-reported symptoms

Assessed by the Brief Pain Inventory severity score (24h recall time): mean of 4 items assessing pain at the moment of the interview, on average, at its least and at its worst during the last 24h. Features of neuropathic pain as assessed by DN4 patient-reported symptoms

Assessed by the Brief Pain Inventory interference score (24h recall time): interference of pain in general activity, mood, walking ability, normal work, relations with other people, sleep and enjoyment of life.

Assessed by the Brief Pain Inventory interference score (24h recall time): interference of pain in general activity, mood, walking ability, normal work, relations with other people, sleep and enjoyment of life.

Assessed by the Brief Pain Inventory interference score (24h recall time): interference of pain in general activity, mood, walking ability, normal work, relations with other people, sleep and enjoyment of life.

Inclusion Criteria: adult patients submitted to open inguinal hernia repair, varicose vein stripping, knee arthroscopy or hallux valgus surgery in Portuguese ambulatory surgery units Exclusion Criteria: psychiatric disorders alcoholism illiteracy or poor understanding of Portuguese language history of chronic pain under opioids recurrent surgery contraindication for midazolam or deep sedation contraindication for spinal anesthesia

Individual participant data that underlie the results reported in this article might be shared with other researchers after deidentification.

Proposals should be directed to caroline.dahlem@gmail.com. To gain access, data requestors will need to sign a data access agreement.

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