This study aims to assess the effect of twin subparaneural injection into individual paraneural sheaths of Common Peroneal Nerve (CPN) and Tibial Nerve (TN) below their point of divergence from the sciatic nerve on the sensory motor blockade after Popliteal Sciatic Nerve Block (PSNB) at the popliteal fossa (back of the thigh) for patients requiring lower limb surgeries.
Ultrasound (US) guided Popliteal Sciatic Nerve Block (PSNB) has been routinely used to provide surgical anaesthesia for ankle and foot surgeries, and the introduction of ultrasound (US) guidance has improved the ease and accuracy of performing PSNB. However, the challenge of achieving the optimal 'readiness for surgery' time after the US guided PSNB continues to confront anaesthesiologists. Cumulative evidence indicates that a subparaneural PSNB improves sensory motor block outcome when compared to subepimyseal PSNB where the local anaesthetic is deposited outside the paraneural sheath. While these are encouraging results, producing sensory motor blockade, i.e. surgical anaesthesia in the area innervated by the sciatic nerve within 30 minutes of local anaesthetic (LA) injection, after a subparaneural PSNB, remains a challenge with the success rate varying from 62-92%. Reasons for this shortcoming, despite LA being deposited in subparaneural space, close to the epineurium of the sciatic nerve, is probably multifactorial as the nerve size, surface area exposed to local anaesthetic, and internal architecture (the connective tissue component) of the sciatic nerve and its branches are all seems to influence block onset time and completeness. It was observed from our clinical practice that distal subparaneural injection (twin halo) into individual paraneural sheaths of common peroneal nerve (CPN) and tibial nerve (TN) below the point of divergence at the popliteal fossa demonstrated a faster sensory motor blockade after PSNB. Therefore, this study aims to assess the effect of twin subparaneural injection into individual paraneural sheaths of CPN and TN below their point of divergence from the sciatic nerve on the sensory motor blockade after PSNB at the popliteal fossa.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
TREATMENT
Masking
NONE
Enrollment
20
Patients schedule for lower limb surgery under regional anesthesia will receive ultrasound guided subparaneural popliteal sciatic nerve block. After identification of the common peroneal nerve and tibial nerve, local anesthetic agents will be injected close to each nerve below the point of divergence at the popliteal fossa. The spread of the drug and the sensory and motor function of that limb will be assessed regularly till it is ready for surgery.
Prince of Wales Hospital
Shatin, New Territories, Hong Kong
the percentage of patients with complete sensory and motor block at 30 min
VRS=0 for both sensory and motor score at 30 min. The extent of the sensory blockade will be graded according to VRS (verbal rating scale) for sensory assessment (100 = normal sensation to 0 = no sensation) in the areas innervated by the sciatic nerve. Motor blockade of the deep peroneal nerve (dorsal flexion of the ankle) and tibial nerve (plantar flexion of the ankle) will be graded using a 3-point scale: 2 = normal, 1 = paresis, and 0 = paralysis.
Time frame: within 45 minutes after the block (at 5min, 10min, 15min, 20 min, 25min, 30min, 45 min)
The time taken to complete sensory and motor blockade at 30 min, time to 'readiness for surgery'
The time point where the sensory block was =\< 30 VRS (VRS 0-100, 100=normal sensation and 0= no sensation) and a motor blockade of =\< 1 (2=normal, 1=paresis, 0=paralysis),
Time frame: within 45 minutes after the block (at 5min, 10min, 15min, 20 min, 25min, 30min, 45min)
Success rate of the block
complete abolition of sensation to cold and paralysis of the muscles in the ipsilateral calf and foot
Time frame: within 45 minutes after the block (at 5min, 10min, 15min, 20min, 25min, 30min, 45min)
Complication
any local anesthetic toxicity
Time frame: from immediately after the block till 24 hours afterwards
Paraesthesia and degree of discomfort
Paresthesia (yes or no); degree if discomfort (numeric rating scale 0-100)
Time frame: during the block
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