Sciatic Nerve Block for Ankle/Foot Surgeries. A Comparison Between a Premixed Solution of Lidocaine Plus Bupivacaine and Consecutive Infiltration of Lidocaine and Bupivacaine

Sciatic Nerve Block for Ankle/Foot Surgeries. A Comparison Between a Premixed Solution of Lidocaine Plus Bupivacaine and Consecutive Infiltration of Lidocaine and Bupivacaine. A Double Blinded Randomised Controlled Prospective Study

Regional anaesthesia has become the cornerstone of multimodal analgesia. With the advent of ultrasound guided nerve blocks regional anaesthesia has achieved both greater efficacy and a better safety profile as the injection of local anaesthetic is performed under direct vision. This has allowed a reduction of the amount of local anaesthetic injected as compared to peripheral nerve stimulation technique . Blockade of sciatic nerve combined with saphenous nerve provides anaesthesia and analgesia for ankle/foot surgeries. Various combinations of local anaesthetics have been used to provide optimal blockade . A mixture of lidocaine with a long acting local anaesthetic is commonly used. This provides a rapid onset of blockade, but of a consistently shorter duration compared to a long acting local anaesthetic alone. We hypothesize that sequential perineural injection of lidocaine and bupivacaine provides similar onset but a longer duration of sensory block compared to the same dose and volume of local anaesthetic mixed in advance.

Inclusion Criteria:

• Patients with ASA 1 - 3 status
• scheduled to undergo semi-elective ankle/foot surgery under regional anaesthesia +/- sedation/opioid free general anaesthesia will be recruited

Exclusion Criteria:

• Patients having surgery on the medial aspect of the ankle/ foot
• allergy to local anaesthetics
• coagulopathy
• malignancy or infection in the popliteal area
• significant peripheral neuropathy
• neurologic disorder of the lower extremity
• any other contraindication to sciatic nerve block
• pregnancy
• history of alcohol or drug dependency/abuse (defined as >40 IU/week)
• a history of significant cognitive or psychiatric disorder that may affect patient assessment