Several reports have compared the duration of action of levobupivacaine and ropivacaine as local anesthetic. The most widely used method for sensory function evaluation is though means of a pinprick test. The investigators want to use the novel method of Quantitative Sensory Testing to better evaluate the anesthetic activity. This method used hot and cold sensation to assess small nerve fiber function. The investigators will assess the duration of action of different drugs when used in an inter scalene nerve block in patients scheduled for shoulder surgery.
This study aims to compare the length of the analgesic effect of different local anesthesic solutions, used in an interscalene nerve block. This will be objectified by measuring the changes in small nerve functioning, using quantative sensory testing. Based on the results of a previous study, the investigators reduce the dose of the administered local anesthetic, expecting a similar length of action using these smaller doses.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
QUADRUPLE
Enrollment
30
The investigators adminster 5ml of Ropivacaine 0.75% in an ultrasound-guided inter scalene nerve block
The investigators adminster 5ml of Levobupivacaine 0.5% in an ultrasound-guided inter scalene nerve block
The investigators adminster 5ml of Levobupivacaine 0.5% + epinephrin 1/200000 in an ultrasound-guided inter scalene nerve block
Length of nerve block measured in longitudinally recorded significant changes in sensory thresholds using quantitative sensory testing
Length of difference in cold and heat pain and sensation measured with quantitative sensory testing
Time frame: 24 hours after intervention
Need for rescue drugs, as requested by the patient after surgery
Time frame: 24 hours after intervention
Motor activity block, longitudinally recorded inability to move the blocked limb
Time frame: 24 hours after intervention
Intensity of nerve block, recorded as maximal changes in sensory thresholds using quantitative sensory testing
The difference in threshold of cold and heat pain and sensation measured with quantitative sensory testing
Time frame: 24 hours after intervention
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