This study aim to calculate the minimal effective ropivacaine concentration required achieve successful analgesic interscalene block in 90% of patients (MEAC90)
* Before induction of general anesthesia, all patients will receive interscalene block using 15ml of ropivacaine which concentration will be based on the response of the previous patient. * Based on biased-coin design up-down sequential method: if patient has pain free recovery, a successful block, the next patient will be randomized to receive either the same ropivacaine concentration or a concentration 0.01% w/v less. However, if he has an unsuccessful block, the next patient will receive a concentration 0.01% w/v higher. * Patients with pain free recovery will be considered to have positive response. * Patients' responses will be analyzed to calculate the MEAC90.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
TREATMENT
Masking
NONE
Enrollment
45
all patients will receive interscalene block using same volume of ropivacaine but in different concentrations
Healthpoint Hospital
Abu Dhabi, United Arab Emirates
effective analgesic interscalene block
postoperative pain (will be assessed using numerical rating scale. if ≥ 3, ineffective block will be considered and if \<3, an effective block will be considered
Time frame: in recovery unit (one hour after surgery)
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