Sciatic nerve block at the popliteal fossa is indicated for foot or ankle surgery, and the introduction of ultrasound guidance (USG) has improved the ease and accuracy of the performance of this block. Recent studies proved that subparaneural injection is associated with faster block onset, higher block success rate, and prolonged block duration suggesting subparaneural compartment of the sciatic nerve is a desirable site for local anaesthetic injection. Data from an ongoing trial in the investigator's institution comparing the block dynamics of subparaneural injection of 30ml 0.5% levobupivacaine (Chirocaine) above and below the bifurcation of the sciatic nerve at popliteal fossa has also shown that the time to 'readiness for surgery' was faster when the injection was performed below the bifurcation of the sciatic nerve. Lidocaine (Xylocaine) has a better pharmacokinetic and pharmacodynamics profile than levobupivacaine and is also widely used as local anaesthetic agent in clinical practice. Since there is no data comparing the block dynamics of lidocaine and levobupivacaine, this study aims to study and compare the block dynamics of lidocaine and levobupivacaine when given as a subparaneural injection below the bifurcation of the sciatic nerve at the popliteal fossa. In this study, the investigator hypothesizes that the use of lidocaine as the sole agent for this block will fasten the time to 'readiness for surgery' as compared to levobupivacaine when given as a subparaneural injection below the bifurcation of the sciatic nerve at the popliteal fossa.
This study will involve performing ultrasound guided subparaneural popliteal sciatic nerve block for 40 patients by using either Lidocaine or Levobupivacaine. Both are commonly used local anaesthetics for regional anaesthesia in daily clinical practice. Patients will be enrolled from the elective orthopaedic surgical list at Prince of Wales Hospital after informed consent.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
QUADRUPLE
Enrollment
40
The plane where the sciatic nerve bifurcates will at first be identified by utlrasound. 22-gauge insulated nerve block needle will be inserted in the short axis (out-of-plane) of the ultrasound transducer, and advanced toward the cleavage between the common peroneal nerve and the tibial nerve, which is the easiest location for needle access into subparaneural compartment.Once the needle tip enters the subparaneural compartment 2-3 ml of normal saline will be injected (hydro-distension) to create a halo around both the common peroneal nerve and tibial nerve distally and the sciatic nerve proximally. The needle is then redirected to place its tip into the paraneural sheath of the common peroneal and tibial nerve through the same skin puncture and 15ml of study drug will be injected at each site (total 30ml).
The plane where the sciatic nerve bifurcates will at first be identified by utlrasound. 22-gauge insulated nerve block needle will be inserted in the short axis (out-of-plane) of the ultrasound transducer, and advanced toward the cleavage between the common peroneal nerve and the tibial nerve, which is the easiest location for needle access into subparaneural compartment.Once the needle tip enters the subparaneural compartment 2-3 ml of normal saline will be injected (hydro-distension) to create a halo around both the common peroneal nerve and tibial nerve distally and the sciatic nerve proximally. The needle is then redirected to place its tip into the paraneural sheath of the common peroneal and tibial nerve through the same skin puncture and 15ml of study drug will be injected at each site (total 30ml).
Prince of Wales Hospital
Shatin, New Territories, Hong Kong
RECRUITINGComplete sensory blockade
Proportion of patients achieving complete sensory blockade (sensory score=0) at 30 minutes; Sensory score: VRS 0-100; 0=no sensation, 100=normal sensation
Time frame: assessed within the first 30 minutes
Complete motor blockade
Proportion of patients achieving complete motor blockade (motor score=0); Motor score: VRS 0-2; 2=normal, 1=paresis, 0=paralysis
Time frame: assessed within the first 50 minutes after nerve block at regular intervals (5min, 10min, 15min, 20min, 25min, 30min, 40min, 50min)
Time to readiness for surgery
Sensory score =\<30 and motor score=\<1
Time frame: assessed within the first 50 minutes after nerve block at regular intervals (5min, 10min, 15min, 20min, 25min, 30min, 40min, 50min)
Time to complete sensory and motor block
Sensory score =0 and motor score=0
Time frame: assessed within the first 50 minutes after nerve block at regular intervals (5min, 10min, 15min, 20min, 25min, 30min, 40min, 50min)
Paresthesia
Any incidence of paresthesia during the nerve block
Time frame: Intraoperative (during the period of undergoing the nerve block)
complications
Any complications during and right after the nerve block directly related to local anaesthetic toxicity
Time frame: after the nerve block till the end of surgery
Discomfort score
the degree of discomfort during the nerve block (NRS : 0-100; 0=no discomfort, 100 very uncomfortable)
Time frame: assess once 1 day before surgery
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