using a biased-coin design up-down sequential method, different concentration of lidocaine will be used for popliteal block After 45 successful block (positive response), the data will be used to calculate the minimum lidocaine concentration that can result in successful popliteal block in 90% of patients
The response of a patient determined the lidocaine concentration given to the next patient (a biased-coin design up-down sequential method). If a patient had a negative response, the lidocaine concentration was increased by 0.1% w/v in the next patient. If a patient had a positive response, the next patient was randomized to receive the same lidocaine concentration (with probability of 0.89), or to receive a concentration 0.1% w/v less (with probability of 0.11).
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
TREATMENT
Masking
NONE
Enrollment
50
patients will receive different lidocaine concentrations
successful popliteal block (positive response)
Sensory block will be assessed using pinprick sensation. Complete sensory block = unable to recognize pinprick sensation. Intra-operative pain will be assessed using Visual Analogue Scale (VAS) 0 = No pain, 10 = Worst imaginable pain. Successful block = complete sensory block + pain free surgery (VAS = 0).
Time frame: 30 min to 3 hour after the block
motor block
degree of motor weakness
Time frame: 30 min after the block
motor recovery
complete recover of the motor power
Time frame: 3 hours till full recovery
analgesic duration
requesting painkiller
Time frame: few hours after block
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