Lignocaine hydrochloride

Unless otherwise stated, all animal surgeries and follow-up evaluations were performed under general anesthesia achieved by intramuscular injections of xylazine hydrochloride (5 mg/kg; Troy Laboratories, Glendenning, NSW, Australia) and ketamine hydrochloride (50 mg/kg; Parnell Laboratories, Alexandria, NSW, Australia), together with a topical application of lignocaine hydrochloride (1%; Pfizer Laboratories, New York City, NY, USA).

New Zealand White rabbits (n = 20) were used for this study and all TE-EK surgeries and CE-CI procedures were performed by JSM. Their use, care and treatment strictly adhered to the regulation of the ARVO statement for the Use of Animals in Ophthalmic and Vision Research, and all experimental procedures were approved by the Institutional Animal Care and Use Committee of SingHealth, Singapore (Ref: 2017/SHS/1292). All surgical procedures and follow-up evaluations were performed under general anesthesia achieved by intramuscular injections of 5 mg/kg xylazine hydrochloride (Troy Laboratories, New South Wales, Australia) and 50 mg/kg ketamine hydrochloride (Parnell Laboratories, New South Wales, Australia), along with topical application of lignocaine hydrochloride 1% (Pfizer Laboratories, New York, USA).

This was studied for eight subjects (mean age 29 ± 12 years, five males and three females), with several participating in other sets of observations (n = 6). The experimental protocol consisted of positive impulses (at two intensities: 0 and +6 dB) and tendon hammer taps applied over C7 while both standing and kneeling. After completion of the baseline observations, local anaesthetic was applied over C7 either topically (n = 5) or via subcutaneous injection (n = 3). Topical anaesthesia was applied over a 6 × 7 cm area using 5 % EMLA cream (AstraZeneca Australia, North Ryde) and secured with Tegaderm transparent film dressing (3 M Health Care, MN). Subcutaneous administration was carried out using 3–4 ml of 2 % lignocaine hydrochloride (Pfizer Australia, West Ryde) injected to 4–6 sites around the usual stimulation site. Skin sensation was assessed approximately 45–60 min postapplication using neurological examination pins (Neurotips, Owen Mumford Inc., GA). Overall, the anesthetised region was approximately 5 cm × 6 cm and included the area of the applied stimuli. The subjects were then retested.