Article

Of phaco and pain management

Our review and meta-analysis of intravenous sedation in modern cataract surgery.

Cataract surgeons can manage a patient’s pain and anxiety during phacoemulsification through a wide variety of anesthetic techniques. These can be used alone or in combination with a variety of sedation modalities, with the anesthesia delivered through intra- or periocular injections or topically as drops or gels. When surgeons opt for conscious sedation, it is often administered intravenously or sublingually. Sedatives, anxiolytics, hypnotics and opiate analgesics are given via oral, sublingual or intravenous sedation.

In the United States and Canada, conscious sedation is not mandatory, yet the majority of cataract surgeries are performed using neuroleptic anesthesia under the supervision of an anesthesiologist. Internationally, research finds significant variation in anesthesia management strategies.1 These variations should come as no surprise.

While many studies2-4 have shown that local anesthesia alone without conscious sedation is sufficient for adequate pain control during cataract surgery, others conclude that local anesthesia alone is not sufficient in managing patient pain and anxiety and that surgeons were more likely to express dissatisfaction with topical/local anesthesia alone.5-7

Then there’s the cost issue. The findings in this study have implications for cost-containment in modern health-care delivery. Performing the procedure without IV sedation may reduce those associated with personnel, disposables and drugs. A cost analysis study8 published in 2001 found that the most cost-effective anesthesia management strategy in cataract extraction was a combination of oral sedation and an ocular block, without an anesthesiologist present ($16.47). The most expensive method involved intravenous sedation and topical anesthesia, with an anesthesiologist present throughout the operation ($324.72). No standards or clinical practice guidelines for the choice of sedation during phacoemulsification currently exist, and the decision relies entirely on the preference of the patient, ophthalmologist, anesthesiologist or administrators where the surgery is performed.

This is the first systematic review and meta-analysis to synthesize the literature on non-intravenous sedation methods vs. intravenous sedation use when comparing the primary outcomes of patient pain and perioperative complications. Our study has the potential to impact resource allocations in both publicly and privately funded environments.

A WORD ON OUR METHODS

We performed this systematic review in accordance with the recommendations of the Cochrane Collaboration9 and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)10 statement.

We searched the following databases using a comprehensive search strategy: Medline (OVID), Embase (OVID), Cochrane Library (Wiley), BIOSIS Previews (Thomson-Reuters), Web of Science (Thomson-Reuters) and CINAHL (EBSCO). Grey literature was explored by searching dissertations, theses, reports, conference proceedings and clinical trials as well as ophthalmology-specific meetings. The review included randomized control trials with a study population of healthy adults (ages 18+) clinically diagnosed with cataracts and undergoing phacoemulsification. We compared intravenous conscious sedation to local anesthetic techniques and sublingual sedation. The primary outcomes were patient pain perception and perioperative complications. Included studies were in English with no restrictions on the geographic location of the study; articles published prior to 1995 were excluded. We conducted data analysis using STATA 13. All values are in U.S. dollars.

RESULTS

Study selection

A total of 4,541 articles were retrieved and imported into Covidence; duplicate article removal then resulted in 2,920 articles for level one abstract screening. Level two full text screening consisted of 428 articles. A total of 10 randomized control trials11-19 (895 participants) were included in the systematic review and meta-analysis. The PRISMA diagram demonstrating the selection process is displayed in Figure 1 (page 48).

Figure 1: PRISMA flow diagram

Patient pain perception

Figure 2 (page 50) displays the forest plot of a random effects meta-analysis comparing pain perception with intravenous sedation vs. no intravenous sedation. IV sedation was significantly associated with a decrease in pain (SMD = -0.86 with 95% CI of -1.49 to -0.23, p=0.0008, i2=94.8%, p<0.001) when compared to all other methods grouped together (no sedation with topical anesthesia and/or intracameral anesthesia, and oral sedation).

Figure 2: Meta-analysis for pain perception (SMD)

Meta-analysis for pain perception (SMD)

We performed a sub-group analysis, grouping studies by non-intravenous sedation method used (Figure 3, page 50). Eight studies compared intravenous sedation with local anesthesia to local anesthesia only; two studies compared intravenous sedation with local anesthesia to oral sedation with local anesthesia. The analysis revealed that IV sedation with local anesthesia was significantly better than local anesthesia alone at controlling pain perception; however, we found no significant difference in perceived pain between IV or oral sedation methods.

Figure 3: Sub-group analysis by non-intravenous methods

Perioperative complication rate

We extracted quantitative data to analyze complication rates when comparing intravenous sedation to non-intravenous methods. The forest plot for the risk of complications with a correction factor of 0.5 is displayed in Figure 4 (below). Our findings: intravenous sedation was not significantly associated with an increase in ocular or systemic complications (RR= 0.99 with 95% CI 0.97 to 1.02, p=0.704, i2=0%), and there was no difference in risk between the two groups.

Figure 4: Meta-analysis for risk of complications with correction factor

DISCUSSION

Intravenous sedation significantly reduces pain during cataract extraction when compared to no sedation. We conducted a weighted mean difference meta-analysis to highlight the clinical significance of this finding and found that intravenous sedation reduced pain by approximately 10%.

The subgroup analysis suggests that oral sedation and intravenous sedation techniques may be equivalent in terms of pain control. Eighteen patients in the IV sedation group had perioperative complications compared to 14 in the non-intravenous group; the meta-analysis indicated no difference in risk between the two groups. Given equivalent effects on pain control and no difference in risk of complications, it is evident that non-intravenous sedation strategies may be a feasible alternative to the more invasive and resource-intensive intravenous methods.

These results have potential cost implications in both publicly and privately funded environments, as the use of intravenous sedation requires considerable resources: equipment, medication, nurse anesthetists and the presence of anesthesiologist. Further, obtaining intravenous access itself is a source of pain and anxiety for the patient.20,21 But added costs can result from augmented anesthetic techniques that reduce pain at the needle entry site.22 According to a 2001 cost analysis study,8 oral sedation cost $16.47 USD per procedure, while IV sedation was estimated at $324.72 per procedure. These values have likely increased since.

This study has identified crucial gaps in the literature, which will guide future research, allowing researchers and clinicians to generate better conclusions regarding the most effective sedation method for phacoemulsification. OM

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