Topical anesthesia with pH-adjusted versus standard lidocaine 4% for clear corneal cataract surgery

WITHDRAWN: Adjusting the pH of lidocaine for reducing pain on injection

May 2015

This review was originally published in 2010 and at that time complied with Cochrane’s Commercial Sponsorship Policy. The Commercial Sponsorship policy was updated in 2014 (http://community.cochrane.org/organisational‐policy‐manual/appendix‐5‐commercial‐sponsorship‐policy ). This review is no longer compliant with that policy.

The non conflicted members of the original team of authors have decided not to update the review. We have therefore decided to withdraw the review and seek new authors to update it

The editorial group responsible for this previously published document have withdrawn it from publication.

Adjusting the pH of lidocaine for reducing pain on injection

BACKGROUND

Lidocaine administration produces pain due to its acidic pH.

OBJECTIVES

The objective of this review was to determine if adjusting the pH of lidocaine had any effect on pain resulting from non-intravascular injections in adults and children. We tested the hypothesis that adjusting the pH of lidocaine solution to a level closer to the physiologic pH reduces this pain.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, to June 2010); Ovid MEDLINE (1966 to June 2010); EMBASE (1988 to June 2010); LILACS (1982 to June 2010); CINAHL (1982 to June 2010); ISI Web of Science (1999 to June 2010); and abstracts of the meetings of the American Society of Anesthesiologists (ASA). We checked the full articles of selected titles. We did not apply any language restrictions.

SELECTION CRITERIA

We included double-blinded, randomized controlled trials that compared pH-adjusted lidocaine with unadjusted lidocaine. We evaluated pain at the injection site, satisfaction and adverse events. We excluded studies in healthy volunteers.

DATA COLLECTION AND ANALYSIS

We separately analysed parallel-group and crossover trials; trials that evaluated lidocaine with or without epinephrine; and trials with pH-adjusted lidocaine solutions < 7.35 and ≥ 7.35. To explain heterogeneity, we separately analysed studies with a low and higher risk of bias due to the level of allocation concealment; studies that employed a low and a higher volume of injection; and studies that used lidocaine for different types of procedures.

MAIN RESULTS

We included 23 studies of which 10 had a parallel design and 13 were crossover studies. Eight of the 23 studies had moderate to high risk of bias due to the level of allocation concealment.Pain associated with the infiltration of buffered lidocaine was less than the pain associated with infiltration of unbuffered lidocaine in both parallel and crossover trials. In the crossover studies, the difference was -1.98 units (95% confidence interval (CI) -2.62 to -1.34) and in the parallel-group studies it was -0.98 units (95% CI -1.49 to -0.47) on a 0 to 10 scale. The magnitude of the pain decrease associated with buffered lidocaine was larger when the solution contained epinephrine. The risk of bias, volume of injection, and type of procedure failed to explain the heterogeneity of the results.Patients preferred buffered lidocaine (odds ratio 3.01, 95% CI 2.19 to 4.15). No adverse events or toxicity were reported.

AUTHORS' CONCLUSIONS

Increasing the pH of lidocaine decreased pain on injection and augmented patient comfort and satisfaction.

Techniques for reducing anesthetic injection pain

BACKGROUND

The authors conducted a study that considered family physicians' and dentists' knowledge and application of techniques to reduce the pain associated with anesthetic injections. They also assessed practitioners' discomfort with patients' injection pain and needle anxiety/phobia.

METHODS

The authors designed a questionnaire about awareness and use of 10 techniques for reducing pain of anesthetic injection and mailed it to 2,000 randomly selected family physicians and general dentists. They analyzed the data to examine differences between disciplines regarding awareness and use of techniques, reasons for not using techniques, number of injections given per week, and predictive value of certain demographic variables on reported use of individual techniques and on practitioner reactions to patients' pain and anxiety.

RESULTS

The response rate was 35 percent. The authors used the chi2 test for differences between disciplines' awareness of and use or nonuse of techniques, Wilcoxon testing to assess differences between disciplines' median values of number of weekly injections and logistic regression to study demographic variables' predictive values (P = .01). General dentists give more injections than do family physicians. Differences existed between disciplines' awareness and use of eight of 10 techniques. Disciplines reported cost and time issues as reasons for not using some techniques. Number of years in practice and age were associated with use of six techniques. Dentists reported feeling greater personal effects of patients' pain and needle anxiety/phobia than did family physicians.

CONCLUSIONS

Those not using pain-lessening techniques inaccurately identified time and cost as problems, suggesting that respondents may be less familiar with these techniques than otherwise reported. Further study is recommended.

CLINICAL IMPLICATIONS

Pain reduction techniques for anesthetic injection cost little to implement, are not time liabilities, and can lessen avoidable pain and reduce the incidence of needle phobia.

Aqueous humor levels of topically applied bupivacaine 0.75% in cataract surgery

PURPOSE

To measure the intraocular levels of bupivacaine 0.75% topically applied before phacoemulsification and to develop standards for topical anesthesia in cataract surgery.

SETTING

Department of Ophthalmology, University Hospitals of Leicester, Leicester, United Kingdom.

METHODS

Forty eyes having phacoemulsification for senile cataract under topical anesthesia without sedation were randomly assigned to 1 of 2 preoperative topical anesthesia regimens. Bupivacaine 0.75% was applied in 0.1 mL drops 3 times in the 30 minutes before surgery in 18 eyes and 6 times in the 60 minutes before surgery in 22 eyes. Aqueous humor and serum samples were taken at the start of surgery and the bupivacaine levels measured. A visual analog pain score scale was used to indicate intraoperative pain.

RESULTS

The mean aqueous humor level of bupivacaine was 5.9 microg/mL +/- 4.3 (SD) after 3 drops and 5.7 +/- 4.0 microg /mL after 6 drops. The blood levels were less than 1.0 microg/mL. There was no statistically significant difference in the intraocular level of bupivacaine between the 2 groups. There was no difference in the age or sex distribution between the 2 groups, although there was an increase in the intraocular level of bupivacaine with age (approximately 1.4 microg/mL per decade; P =.048). There was no clear pattern associating the pain score with age, sex, or intraocular level of bupivacaine.

CONCLUSIONS

A 3-drop regimen of bupivacaine 0.75% in the half hour before cataract surgery penetrated the eye as effectively as 6 drops in the 1 hour before surgery and provided good analgesia for phacoemulsification. Bupivacaine 0.75% penetrated the eye increasingly effectively with increasing age.

A prospective, randomized, double-blind comparison of buffered versus plain tetracaine in reducing the pain of topical ophthalmic anesthesia

STUDY OBJECTIVE

We determine whether buffering ocular tetracaine hydrochloride reduces the pain of instillation.

METHODS

We conducted a prospective, randomized, double-blind, 2-treatment, 2-period crossover, single center study of healthy volunteers 18 years of age or older. Participants were randomized to receive either 2 drops of buffered or plain tetracaine in a randomly assigned eye. After a mean wash out period of 24 days (range 7 to 54 days), participants returned to have 2 drops of the other medication instilled in the same eye. The participants recorded the pain of instillation on a 100-mm visual analog scale (VAS) immediately and 5 minutes after instillation. Adverse events were also recorded at these intervals. The primary outcome measure was the intensity of pain as measured on a VAS immediately after instillation.

RESULTS

Sixty persons were enrolled in the study, with 100% follow up. Immediately after instillation, the adjusted mean VAS score for buffered tetracaine was 29.1 mm, and the adjusted mean VAS score for plain tetracaine was 16.0 mm. The estimated difference was 13.1 mm (95% confidence interval 6.9 to 19.3 mm).

CONCLUSION

Buffering of tetracaine hydrochloride significantly increases the pain of its instillation in healthy volunteers, suggesting that pain with instillation of ocular anesthetics is not dependent on low pH.

Lidocaine 2% gel versus lidocaine 4% unpreserved drops for topical anesthesia in cataract surgery: a randomized controlled trial

OBJECTIVE

To compare intracameral levels and clinical efficacy of lidocaine 2% gel with lidocaine 4% unpreserved drops.

DESIGN

Double-blind, randomized, one-surgeon, controlled trial.

PARTICIPANTS

One hundred seven consecutive cataract cases eligible for topical anesthesia.

INTERVENTION

Patients were randomly assigned to receive 20 mg of lidocaine either as lidocaine 2% gel (1 ml) or as lidocaine 4% unpreserved eyedrops (0.5 ml) before clear corneal phacoemulsification.

MAIN OUTCOME MEASURES

Aqueous samples were taken to measure lidocaine intraocular levels. Intraoperative pain was quantified a few minutes after surgery using a 0 to 10 visual analog scale.

SECONDARY OUTCOME MEASURES

Patients were asked to grade the degree to which they were bothered by tissue manipulation. The surgeon graded patients' cooperation. The anesthesiologist recorded any increase in pulse or blood pressure and the need for supplemental topical anesthesia or intravenous sedation. Duration of surgery and intraoperative complications were also recorded.

RESULTS

In the gel group intracameral lidocaine levels were significantly higher (P < 0.001) and patient-reported intraoperative pain scores were significantly lower (P = 0.026). Patients in the gel group were bothered by tissue manipulation to a lesser extent (P = 0.028), and their cooperation was better (P = 0.002). Increases in blood pressure were more frequent in the eyedrops group. Supplemental anesthesia was required in two cases (3.70%) in the gel group versus eight cases in the eyedrops group (15.09%). No correlation between intracameral lidocaine levels and intraoperative pain scores was found (r = -0.026, P = 0.789).

CONCLUSIONS

If administered by means of gel, the same amount of lidocaine gives significantly higher intracameral levels of lidocaine, better analgesia, better patient cooperation, and less need for intraoperative supplemental anesthesia. Lower pain scores do not correlate with intracameral lidocaine levels.

Transcervical intrauterine topical local anesthetic at hysterosalpingography: a prospective, randomized, double-blind, placebo-controlled trial

OBJECTIVE

To assess whether transcervical intrauterine topical instillation of a local anesthetic agent reduces pain at hysterosalpingography.

DESIGN

Prospective, randomized, double-blind, placebo-controlled study.

SETTING

Department of reproductive medicine at a university teaching hospital.

PATIENT(S)

One hundred ten women undergoing hysterosalpingography (HSG).

INTERVENTION(S)

Subjects were randomized to receive either 2 mL of 2% plain lignocaine or 2 mL of 0.9% sodium chloride solution (placebo) topically into the uterine cavity before the HSG was performed.

MAIN OUTCOME MEASURE(S)

The degree of lower abdominal pain experienced both during the injection of contrast media at HSG and 10 minutes after the procedure using a 20-cm visual analogue scale (VAS) and a four-point verbal descriptor scale (VDS).

RESULT(S)

There was no difference in pain scores between lignocaine and placebo during the HSG. However, at 10 minutes after the HSG, subjects receiving lignocaine experienced more pain than those on placebo.

CONCLUSION(S)

Transcervical intrauterine topical instillation of 2 mL of 2% plain lignocaine does not reduce pain during HSG and may lead to increased pain immediately after the procedure.

Alkalinization increases penetration of lidocaine across the human cornea

PURPOSE

To test the hypothesis that corneal permeability of lidocaine complies with the principle of nonionic diffusion.

SETTING

Department of Ophthalmology and Institute of Pharmacology, Vienna, Austria.

METHODS

Human corneas, mounted in an in vitro perfusion system under short-circuit conditions, were exposed on the epithelial (tear) side to lidocaine 4% in a buffered solution of pH 5 or pH 7. The endothelial bathing solutions had a constant pH of 7.4. Both solutions were adjusted to an osmolarity of 290 mOsm/L. The lidocaine permeability of the isolated corneas was assessed from the fluxes of 14C-labeled lidocaine across the tissue, measured at 15-minute intervals for 180 minutes, and corrected for the unidirectional fluxes of 3H-polyethylene glycol, a marker for the extracellular pathway. The corneal tissue content of lidocaine was estimated from the time span until the unidirectional lidocaine fluxes across the cornea reached a steady state.

RESULTS

The mean transcorneal fluxes of lidocaine in the steady state (90 to 180 minutes) were 72% higher at pH 7 than at pH 5 (101 mmol/min +/- 37 (SD) versus 59 +/- 34 nmol/min.cornea; P <.002). The corneal content of lidocaine in the steady state was 65% higher at pH 7 than at pH 5 (2.8 +/- 0.9 micromol/cornea versus 1.7 +/- 1.2 micromol/cornea; not significant).

CONCLUSIONS

A shift in solution pH from 5 to 7 significantly increased the corneal permeability of topically applied lidocaine. Alkaline pH-adjustment of topical lidocaine solutions is easy to perform by adding sodium bicarbonate. The main clinical advantages of anesthetic solutions buffered at pH 7 are increased penetration rates, effectiveness, prolonged action time, and a reduction in local irritation and lacrimation.

The methodologic quality of clinical trials on regional anesthesia for cataract surgery

OBJECTIVE

To assess the methodologic quality of published randomized trials of regional anesthesia management strategies for cataract surgery.

DESIGN

Literature review and analysis.

METHOD

We performed a systematic search of the literature to identify all articles pertaining to regional anesthesia for cataract surgery on adults. Overall quality scores and scores for individual methodologic domains were based on the evaluations of two investigators experienced in methodologic research who independently reviewed all relevant articles using a quality abstraction form.

MAIN OUTCOME MEASURES

Study quality in each of five domains: representativeness, bias and confounding, intervention description, outcomes and follow-up, and statistical quality and interpretation.

RESULTS

Eighty-two randomized clinical trials were identified with a mean overall quality score of 44%. The mean domain scores ranged from 37% for representativeness to 58% for outcomes and follow-up. Forty percent or fewer studies received the maximum score for reporting the setting, the population, and the start and end dates; describing the inclusion and exclusion criteria; adequately randomizing subjects; and adequately masking individuals participating in the study. Key outcomes were often inadequately reported, including the distribution of patient-reported pain scores and the mean surgical time.

CONCLUSIONS

Greater attention to methodologic quality and detailed reporting of study results will improve the ability of readers to interpret the results of clinical trials assessing regional anesthesia for cataract surgery.

Synthesis of the literature on the effectiveness of regional anesthesia for cataract surgery

OBJECTIVE

To synthesize the findings of the randomized trials of regional anesthesia management strategies for cataract surgery.

DESIGN

Literature review and analysis.

METHOD

The authors performed a systematic search of the literature to identify all articles pertaining to regional anesthesia during cataract surgery on adults. One investigator abstracted the content of each article onto a custom-designed form. A second investigator corroborated the findings. The evidence supporting the anesthesia approaches was graded by consensus as good, fair, poor, or insufficient.

MAIN OUTCOME MEASURES

Evidence supporting the effectiveness of different forms of regional anesthesia.

RESULTS

There was good evidence that retrobulbar and peribulbar blocks provide equivalent akinesia and pain control during cataract surgery. Additionally, sub-Tenon's blocks were at least as effective as retrobulbar and peribulbar blocks. There was good evidence that retrobulbar block provides better pain control during surgery than topical anesthesia, and there was fair evidence that peribulbar block provides better pain control than topical anesthesia.

CONCLUSIONS

This synthesis of the literature demonstrates that currently used approaches to anesthesia management provide adequate pain control for successful cataract surgery, but there is some variation in the effectiveness of the most commonly used techniques. Data are needed on patient preferences to determine the optimal strategies for anesthesia management during cataract surgery.

Corneal endothelial toxicity of different lidocaine concentrations

PURPOSE

To examine the potential damaging effect on the corneal endothelium of unpreserved lidocaine in concentrations of 1%, 5%, and 10%.

SETTINGS

Department of Ophthalmology, Charité Medical Faculty, Humboldt University, Berlin, Germany.

METHODS

Experimental porcine corneas (n = 18) were exposed to 100 microL of unpreserved lidocaine hydrochloride at concentrations of 1%, 5%, and 10% for 60 minutes. Additional corneas (n = 6) were treated with lidocaine hydrochloride 1% for 30 minutes to simulate clinical conditions. Balanced salt solution (BSS((R))) served as a control to evaluate corneal endothelial cell damage using Janus Green photometry. Morphology, damage pattern, and changes in the ultrastructural appearance of corneal endothelial cells were examined by light and scanning electron microscopy.

RESULTS

Lidocaine 1% used for 30 or 60 minutes did not cause significantly more corneal endothelial damage (mean 3.00% +/- 0.76% [SD] and 3.26% +/- 1.00%, respectively) than in the control group (mean 3.32% +/- 0. 86%) (P >.01). Significant corneal endothelial cell loss was observed with lidocaine 5% (mean 10.7% +/- 6.4%) (P <.001) and lidocaine 10% (42.3% +/- 17.0%) (P <.001).

CONCLUSION

Experimental exposure of corneal endothelial cells to higher concentrations of lidocaine resulted in significant cell loss, indicating that the 1% concentration only should be used clinically.

Combined sedation and topical anesthesia for cataract surgery

PURPOSE

To determine whether lidocaine jelly is as efficacious as tetracaine drops for obtaining ocular anesthesia and to evaluate sublingual lorazepam as premedication for sedation in cataract surgery.

SETTING

An ambulatory surgical center dedicated to ophthalmic surgery.

METHODS

The study was divided into 2 phases. In the first, 100 patients were divided into 2 groups of 50 each. The first group received tetracaine 0.5% drops for anesthesia. The second group received lidocaine 2% jelly for topical anesthesia. In the second stage, 100 patients were divided into 2 groups of 50 each. The first 50 patients were given 1 mg of sublingual lorazepam before surgery. The second group had cataract surgery without sublingual lorazepam. All patients were operated on by the same surgeon in an ambulatory surgical center. The technique was temporal clear corneal cataract surgery with foldable intraocular lens implantation. Exclusions from the study were the need to convert to peribulbar or retrobulbar anesthesia, intraocular complications, and altered mental status.

RESULTS

In the first phase of the study, lidocaine 2% jelly was as efficacious as tetracaine 0.5% drops for topical anesthesia in cataract surgery. In the second phase of the study, overall, patients in the lorazepam group had less anxiety, greater amnesia, and lower blood pressure than those not receiving lorazepam as sedation for topical anesthesia.

CONCLUSIONS

Lidocaine 2% jelly combined with sublingual lorazepam provided excellent cost-effective anesthesia and sedation for topical anesthesia in cataract surgery and enhanced patient satisfaction with the procedure.

Systemic levels of lidocaine after intracameral injection during cataract surgery

PURPOSE

To evaluate the systemic concentrations of lidocaine after intracameral injection of a 1% solution during cataract surgery and the safety of this application mode.

SETTING

Department of Ophthalmology, Medical University of Lübeck, Lübeck, Germany.

METHODS

This prospective study included 10 patients who had phacoemulsification and posterior chamber lens implantation with a self-sealing scleral tunnel incision. Topical anesthesia was achieved using cocaine 10% eyedrops combined with 0.5mL of unpreserved lidocaine 1% injected into the anterior chamber. Blood samples were taken from all patients at predetermined intervals before and during the procedure. Consecutive analysis for lidocaine was performed with gas chromatography.

RESULTS

In all samples, serum lidocaine concentrations were below a minimum detectable level of 100 ng/mL. No local or systemic intraoperative or postoperative complications were noted.

CONCLUSIONS

Intracameral injection of 0.5 mL lidocaine 1% revealed no systemic therapeutic concentrations. In patients in whom other forms of needle-delivered local anesthesia are contraindicated, intracameral injection of lidocaine should be considered to enhance topical anesthesia.