PubMed · 8917153
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J W Richards. 1996. Lidocaine anesthesia.. https://pubmed.ncbi.nlm.nih.gov/8917153/
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OBJECTIVES: To characterize the uptake, washout, and metabolism of lidocaine hydrochloride in the iris/ciliary body and cornea. METHODS: Iris/ciliary body uptake of lidocaine hydrochloride was measured by incubating human and rabbit irides in radiolabeled carbon 14-1% lidocaine hydrochloride for 2 to 60 minutes. Washout was determined by incubating the iris in 14C-1% lidocaine hydrochloride for 5 minutes and transferring the iris to a series of wells. The wells contained a common intraocular irrigating solution of essential ions, glucose, and glutathione buffered with bicarbonate (an enriched balanced salt solution [BSS PLUS]), which is similar to aqueous humor. Corneal uptake was measured by exposing the endothelial surface to 14C-1% lidocaine hydrochloride for 5 or 15 minutes. Corneal washout was performed after 5-minute exposure to 14C-1% lidocaine hydrochloride using a 2-chambered diffusion apparatus. Samples of the iris, cornea, and BSS PLUS washout solution were analyzed by high-performance liquid chromatography and liquid scintillation spectrometry. RESULTS: In vitro iris/ciliary body uptake of 14C-1% lidocaine hydrochloride follows a logarithmic curve, with 50% to 60% of maximum lidocaine hydrochloride uptake present at 5 minutes. There was no difference in uptake between human, albino rabbit, and pigmented rabbit irides. Washout of lidocaine from the iris occurs with a halflife of 8 to 9 minutes. Corneal uptake of lidocaine was greater after incubation for 15 vs. 5 minutes. The washout of lidocaine from the cornea had a half-life of 5 minutes. Results of high-performance liquid chromatography confirmed that there were no metabolites or breakdown products in the iris, cornea, or washout solution. CONCLUSIONS: Lidocaine is taken up quickly by the iris/ ciliary body and cornea and rapidly removed from these tissues after BSS PLUS washout. Irrigation during phacoemulsification seems to limit lidocaine exposure to the ocular tissues, resulting in a short duration of anesthesia. Lidocaine is not metabolized or broken down by the iris or cornea during this short period.
STUDY OBJECTIVE: To assess the efficacy of dermal anesthesia by lidocaine iontophoresis in children undergoing peripheral intravenous (PIV) catheter placement in the emergency department. METHODS: A double-blind, randomized, clinical trial was conducted at a tertiary children's hospital ED. Alert children 7 years or older requiring nonemergency PIV were eligible. Patients in the lidocaine group received 1 mL of 2% lidocaine with 1:100,000 epinephrine over a potential PIV site by iontophoresis. The control group received 1 mL of.9% saline solution with 1:100,000 epinephrine. After PIV placement, patients ranked the procedural pain using a visual analog scale. Complications were noted by visual inspection or telephone follow-up. RESULTS: During a 6-month period, 22 patients were assigned to the lidocaine group and 25 to the control group. There was no significant difference in age, sex, or ethnic background between the 2 study groups, and mean application time was 12.0 minutes. The median pain score was.5 in the lidocaine group compared with 4 in the control group (P =.0002; 95% confidence interval [CI] 1 to 5). No significant immediate or delayed complications were observed. CONCLUSION: Lidocaine iontophoresis provides effective dermal anesthesia for children older than 7 years of undergoing nonemergency PIV placement in the ED.
This technique is a safe simple way to administer sub-Tenon's anesthesia that provides akinesia comparable to that of retrobulbar and peribulbar anesthesia and frequently results in excellent lid block. The potentially serious complications associated with retrobulbar and peribulbar methods appear to be absent.