Evidence Report/Technology Assessment

Number 16

Prepared for:
Agency for Healthcare Research and Quality
U.S. Department of Health and Human Services
2101 East Jefferson Street
Rockville, MD 20852

http://www.ahrq.gov/

Contract No. 290-097-0006

Prepared by:
Johns Hopkins University Evidence-based Practice Center
Oliver D. Schein, M.D., M.P.H.
Principal Investigator
David S. Friedman, M.D., M.P.H.
Lee A. Fleisher, M.D.
Co-Principal Investigators

Lisa H. Lubomski, Ph.D.
Jeffrey Magaziner, M.D.
Michael Sprintz, M.D.
John Kempen, M.D., M.P.H.
Sherman W. Reeves
Karen A. Robinson, M.Sc.
Eric B. Bass, M.D., M.P.H.
Investigators

AHRQ Publication No. 01-E017

December 2001

On December 6, 1999, under Public Law 106-129, the Agency for Health Care Policy and Research (AHCPR) was reauthorized and renamed the Agency for Healthcare Research and Quality (AHRQ). The law authorizes AHRQ to continue its research on the cost, quality, and outcomes of health care and expands its role to improve patient safety and address medical errors.

This report may be used, in whole or in part, as the basis for development of clinical practice guidelines and other quality enhancement tools, or a basis for reimbursement and coverage policies. AHRQ or U.S. Department of Health and Human Services endorsement of such derivative products may not be stated or implied.

AHRQ is the lead Federal agency charged with supporting research designed to improve the quality of health care, reduce its cost, address patient safety and medical errors, and broaden access to essential services. AHRQ sponsors and conducts research that provides evidence-based information on health care outcomes; quality; and cost, use, and access. The information helps health care decisionmakers -- patients and clinicians, health system leaders, and policymakers -- make more informed decisions and improve the quality of health care services.

The Agency for Healthcare Research and Quality (AHRQ), formerly the Agency for Health Care Policy and Research, through its Evidence-based Practice Centers (EPCs), sponsors the development of evidence reports and technology assessments to assist public- and private-sector organizations in their efforts to improve the quality of health care in the United States. The reports and assessments provide organizations with comprehensive, science-based information on common, costly medical conditions and new health care technologies. The EPCs systematically review the relevant scientific literature on topics assigned to them by AHRQ and conduct additional analyses when appropriate prior to developing their reports and assessments.

To bring the broadest range of experts into the development of evidence reports and health technology assessments, AHRQ encourages the EPCs to form partnerships and enter into collaborations with other medical and research organizations. The EPCs work with these partner organizations to ensure that the evidence reports and technology assessments they produce will become building blocks for health care quality improvement projects throughout the Nation. The reports undergo peer review prior to their release.

AHRQ expects that the EPC evidence reports and technology assessments will inform individual health plans, providers, and purchasers as well as the health care system as a whole by providing important information to help improve health care quality.

We welcome written comments on this evidence report. They may be sent to: Director, Center for Practice and Technology Assessment, Agency for Healthcare Research and Quality, 6010 Executive Blvd., Suite 300, Rockville, MD 20852.

Surgery for age-related cataract is the highest volume surgical procedure in the Medicare population. In the United States, approximately 1.5 million cataract operations were performed on Medicare beneficiaries in 1996. Cataract surgery is almost exclusively performed as an outpatient procedure and usually involves the administration of a local anesthetic in addition to systemic sedation administered by an anesthesiologist or nurse anesthetist. There is considerable national and international variation in anesthesia management strategies for cataract surgery. The principal objectives of this Evidence Report are to summarize the published literature on (1) the risks and benefits associated with the use of one form of regional anesthesia over another and (2) the risks and benefits associated with different approaches to sedating the patient for cataract surgery.

The primary sources for the literature review were PubMed and the Cochrane Collaboration's database of controlled clinical trials. Medical subject heading (MeSH) terms used in the searches included cataract, anesthesia, and hypnotics or sedatives. All included studies were published between 1968 and 1999.

An article was included in the Evidence Report if it (1) addressed cataract surgery using local anesthesia (with or without sedation) in an adult population, (2) was a controlled trial or a case series with more than 100 cases, and (3) provided outcomes specifically related to the research questions.

After assessment of 739 potentially relevant citations, by abstract or full manuscript review, 141 were identified that met eligibility criteria. Study quality was assessed and data abstracted by pairs of reviewers. Results are presented in evidence tables and the quality of evidence for specific questions graded as strong, moderate, weak, or insufficient. Supplemental analyses include a decision analysis comparing alternative management strategies, an analysis of early postoperative morbidity and mortality based on Medicare claims data, and an analysis of patient perceptions of different anesthesia strategies from the Study of Medical Testing for Cataract Surgery.

Of the 141 reviewed studies, 122 focused on local anesthesia techniques either alone or in combination with sedation strategies. Of these, 86 were randomized clinical trials and 36 were noncontrolled studies. Nineteen studies, all of which were randomized clinical trials, specifically focused on issues relating to sedation. The mean overall methodology quality score (maximum = 100) was 46 for randomized clinical trials and 33 for noncontrolled studies.

The effectiveness of a regional block for cataract surgery has traditionally been assessed by describing the completeness and adequacy of globe akinesia (i.e., prevention of eye movement) and pain control.

Regarding globe akinesia, there was strong evidence of equivalent effectiveness of peribulbar and retrobulbar anesthesia. There was insufficient evidence to compare subconjunctival/sub-Tenon's anesthetic block with peribulbar and retrobulbar blocks regarding akinesia. However, the rates of adequate akinesia appeared similar across the three techniques. There was weak evidence that adding hyaluronidase or using certain specific anesthetic agents over others produced superior akinesia. There was insufficient evidence to reach any conclusion regarding the relationship between akinesia and the volume of anesthetic used or the speed of injection.

Regarding pain associated with administration of the block, there was weak evidence to suggest that peribulbar injection was slightly less painful than retrobulbar injection, moderate evidence that subconjunctival/sub-Tenon's block was less painful than retrobulbar block, and insufficient evidence that subconjunctival/sub-Tenon's block was less painful than peribulbar block.

Regarding pain control during surgery, all of the major classes of techniques reported yielded good or excellent intraoperative pain control. The evidence was strong that retrobulbar and peribulbar techniques produce equivalent pain control during cataract surgery, and there was moderate evidence indicating superiority of pain control using subconjunctival/sub-Tenon's approaches compared with retrobulbar block. There was insufficient evidence to determine whether peribulbar or subconjunctival/sub-Tenon's anesthesia results in better pain control during surgery. There was strong evidence that retrobulbar block results in less pain during cataract surgery than topical anesthesia, moderate evidence that peribulbar block results in less pain during cataract surgery than topical anesthesia, and weak evidence that subconjunctival/sub-Tenon's block produces better pain control than topical anesthesia during cataract surgery.

Regarding specific agents used for local anesthesia, virtually all agents reported had high rates of excellent pain control, and there was insufficient evidence to determine if some agents produced better pain control during surgery than others.

Complications related to different anesthesia techniques were rarely and not systematically reported in the literature. The most important ocular and systemic complications are sufficiently rare that the reported frequency in the reviewed studies was almost invariably zero. Comparison of complication rates was also limited by wide variation in outcome definitions.

Regarding sedation strategies, weak evidence was found that intravenous or intramuscular sedation or analgesia is associated with improved anxiety control, pain relief, and patient satisfaction. There was insufficient evidence to suggest that one sedative or analgesic regimen was superior to another.

An analysis of a large Medicare claims data set was directed at ascertaining risk factors for readmission within 1 week following cataract surgery. Increasing age, medical comorbidity, and inpatient surgery were found to be predictive of readmission. Risk of readmission was greater for surgery performed in an office-based setting, but the relatively small number of individuals undergoing surgery in this setting limited the significance of this finding.

A decision analysis of alternative anesthesia management strategies indicated that strategies employing retrobulbar or peribulbar block yielded higher respondent preference values from medical experts than strategies employing topical anesthesia. In addition, among strategies employing retrobulbar or peribulbar block, the availability of an anesthesiologist either on call or present to provide intravenous sedation was preferred over having no anesthesiologist present. Having an anesthesiologist present for every case was associated with increased costs, albeit at increased preference values relative to simply having an anesthesiologist on call. Additional input from patients regarding their preferences and further clinical research are needed to validate the findings of the decision analysis.

An analysis of data on patient reports of their cataract surgical experience based on 19,250 surgeries from the Study of Medical Testing for Cataract Surgery indicated a high level of satisfaction with anesthesia management regardless of strategy, greater intraoperative pain with topical than injection anesthesia, and a greater rate of postoperative drowsiness and nausea when intravenous agents were used.

High priorities for additional research are improving the methodological quality of studies in the field, assessing patient (and surgeon) preferences (utilities) for different anesthesia management strategies and outcomes, and assessing the cost-effectiveness of intravenous sedation and monitoring by anesthesia personnel.

A variety of commonly employed anesthesia management strategies for cataract surgery appear to be safe and highly effective. Topical anesthesia does not provide as complete pain control as do the various injection techniques, although this technique is clearly quite effective and avoids rare complications potentially associated with injection techniques. There is only weak evidence that intravenous or intramuscular sedation or analgesia improve anxiety control, pain relief, and patient satisfaction with cataract surgery.

This document is in the public domain and may be used and reprinted without permission, except those copyrighted materials noted, for which further reproduction is prohibited without the specific permission of copyright holders.

Schein OD, Friedman DS Fleisher LA, et al. Anesthesia Management During Cataract Surgery. Evidence Report/Technology Assessment No. 16. (Prepared by the Johns Hopkins University Evidence-based Practice Center under Contract No. 290-097-0006.) AHRQ Publication No. 01-E017. Rockville, MD: Agency for Healthcare Research and Quality. December 2001.

Surgery for age-related cataract is the highest volume surgical procedure performed on Medicare beneficiaries. Approximately 1.5 million surgeries were performed on this population in 1996. Cataract surgery is performed almost exclusively as an outpatient procedure. It usually involves the administration of a local anesthetic in addition to systemic sedation administered by an anesthesiologist or nurse anesthetist.

Previous research has indicated substantial national and international variation in anesthesia management strategies for cataract surgery. The most common forms of local anesthesia include injection techniques (retrobulbar, peribulbar, subconjunctival/sub-Tenon's) and topical anesthesia. Sedating agents given orally or intravenously are commonly used to reduce patient anxiety and discomfort.

Surgeons' and anesthesiologists' preferences, as well as patient characteristics, are believed to influence the choice of anesthesia management for cataract surgery. However, there is uncertainty as to which strategy or strategies provide the best mix of patient comfort, surgical outcomes (e.g., pain control, ease of performing surgery), and freedom from anesthesia-related complications (e.g., brainstem anesthesia, retrobulbar hemorrhage, globe perforation). Therefore, in October 1998, the Agency for Health Care Policy and Research, now renamed the Agency for Healthcare Research and Quality (AHRQ), awarded a contract to the Johns Hopkins University Evidence-based Practice Center to prepare an evidence report on the management of local anesthesia and sedation during surgery for age-related cataract.

The principal objective of this evidence report is to summarize the published literature on the risks and benefits associated with the use of one form of regional anesthesia over another and the risks and benefits associated with different approaches to sedating the patient for cataract surgery. Two key questions were addressed in the literature abstraction process:

• What are the risks and benefits associated with the use of one form of regional anesthesia over another?
• What are the risks and benefits associated with different approaches to sedating the patient for cataract surgery?

For the first question, published studies comparing common forms of local anesthesia, including injection techniques and topical anesthesia, were reviewed. This question included issues related to patient characteristics, complications, choice of agent, training, and evidence for supplemental agents to enhance local anesthesia performance (e.g., heat and pH adjustment). The second question included issues related to complication rates, specific sedation strategies, level and intensity of monitoring, and the presence of evidence supporting the use of sedation.

An article was included in the evidence report if it (1) addressed cataract surgery using local anesthesia (with or without sedation) in an adult population, (2) was a controlled trial or a case series with more than 100 cases, and (3) provided outcomes specifically related to the research questions described above. In addition to data collected on risks and benefits, further information of interest included setting of surgery, intraoperative monitoring, patient comorbidity, choice of agent, the prior training of personnel, and use of supplemental agents.

The specific questions addressed in the evidence report were identified through consultation by the study team with a core panel of clinical experts. Electronic searches were conducted in PubMed and CENTRAL, the Cochrane Collaboration's database of controlled trials. PubMed includes publications from 1966 to the present. CENTRAL includes controlled trials from 1948 to the present. Additionally, principal ophthalmology- and anesthesiology-related journals, as well as reference lists from major reviews, were hand searched. The medical subject heading (MeSH) terms used in the searches included cataract, anesthesia, hypnotics, and sedatives. The literature considered was not limited to randomized trials but also included nonrandomized controlled trials and case series of 100 or more patients.

Of 1,857 potentially relevant citations identified, 739 were unique, appeared to meet the inclusion criteria, and were subsequently included in the abstract review process. All included studies were published between 1968 and 1999. After full review of abstracts and available published studies, 141 articles were identified that met all the eligibility criteria. Pairs of reviewers assessed study quality and abstracted data.

The results are presented in evidence tables, where the quality of evidence for specific questions is graded as strong, moderate, weak, or insufficient. The report also includes supplemental analyses: an analysis of early postoperative morbidity and mortality based on Medicare claims data, a decision analysis comparing alternative management strategies, and an analysis of patient perceptions of different anesthesia strategies from the Study of Medical Testing for Cataract Surgery.

Of the 141 studies reviewed, 122 focused on either local anesthesia techniques or local techniques in combination with sedation strategies. Of these, 86 were randomized clinical trials and 36 were noncontrolled studies including 100 or more patients. Nineteen studies, all of which were randomized clinical trials, specifically focused on issues related to sedation. The mean overall methodology quality score (maximum = 100) was 46 for randomized clinical trials and 33 for noncontrolled studies. There were significant issues in all quality domains examined. However, the lowest scores were in the areas of study representativeness, issues relating to methodologic bias, and adequacy of the description of therapy.

There was strong evidence that indicated no difference between peribulbar and retrobulbar anesthesia in achieving globe akinesia for cataract surgery. There was insufficient evidence to compare subconjunctival/sub-Tenon's anesthetic block with peribulbar and retrobulbar blocks. However, the rates of adequate akinesia appeared to be similar across the three techniques. There was weak evidence that adding hyaluronidase or using specific anesthetic agents instead of others produced superior akinesia. There was insufficient evidence to reach any conclusion regarding the relationship of block effectiveness to volume of anesthetic used or speed of injection.

There was weak evidence to suggest that peribulbar injection was slightly less painful than retrobulbar injection, moderate evidence that subconjunctival/sub-Tenon's block was less painful than retrobulbar block, and insufficient evidence that subconjunctival/sub-Tenon's block was slightly less painful than peribulbar block.

All of the major classes of techniques reported yielded good or excellent intraoperative pain control. The evidence was strong that retrobulbar and peribulbar techniques produce equivalent pain control during cataract surgery, and there was moderate evidence indicating superior pain control with the use of subconjunctival/sub-Tenon's approaches compared with retrobulbar block. There was insufficient evidence to determine whether peribulbar or subconjunctival/sub-Tenon's anesthesia results in better pain control during surgery. There was strong evidence that retrobulbar block results in less pain during cataract surgery than topical anesthesia, moderate evidence that peribulbar block results in less pain during cataract surgery than topical anesthesia, and weak evidence that subconjunctival/sub-Tenon's block results in less pain during cataract surgery than topical anesthesia.

Virtually all agents reported had high rates of excellent pain control. There was insufficient evidence to determine whether some agents produced better pain control during surgery than others.

Complications related to different anesthesia techniques were rarely and not systematically reported in the literature. The most important ocular and systemic complications (e.g., globe perforation, myocardial infarction) are sufficiently rare that the reported frequency was almost invariably zero. Comparison of complication rates was also limited by wide variation in outcome definitions.

Weak evidence was found that intravenous or intramuscular sedation or analgesia is associated with better anxiety control, pain relief, and patient satisfaction than the lack of such sedation or analgesia. There was insufficient evidence to suggest that one analgesic regimen was superior to another.

Three supplemental analyses were performed:

• Analysis of a large Medicare claims data set -- This analysis was directed toward ascertaining risk factors for readmission within 1 week of cataract surgery. Increasing age, medical comorbidity, and inpatient surgery were predictive of readmission. Risk of admission was greater for surgery performed in an office-based setting, but the relatively small number of individuals undergoing surgery in this setting limited the significance of this finding.
• Decision analysis of alternative anesthesia management strategies -- This decision analysis indicated that respondents, who were medical experts, had higher preference values for strategies employing retrobulbar or peribulbar block than for strategies employing topical anesthesia. In addition, among strategies employing retrobulbar or peribulbar block, they preferred having an anesthesiologist either present or on call to provide intravenous sedation over having no anesthesiologist present. However, having an anesthesiologist present for every case was associated with increased costs, albeit at increased preference values, relative to simply having an anesthesiologist on call. Additional input from patients regarding their preferences and further clinical research are needed to validate the findings of the decision analysis.
• Analysis of data on patient reports of their cataract surgical experience -- Based on 19,250 surgeries from the Study of Medical Testing for Cataract Surgery, this study indicated a high level of satisfaction with anesthesia management regardless of strategy, greater intraoperative pain with topical than with injection anesthesia, and a greater rate of postoperative drowsiness and nausea when intravenous agents were used.

The published evidence and supplemental analyses indicate that a variety of strategies for anesthesia management of cataract surgery are safe and effective. Our findings do not indicate that a particular strategy is sufficiently superior to others to warrant a change in current practice or a rigid guideline for anesthesia care during cataract surgery. However, several high priorities for future research were identified. First, the methodologic quality of clinical trials in the field should be improved. Specifically, far greater attention should be paid to issues relating to representativeness, description of the intervention, patient comorbidities, length of the surgery, and the standardization of outcomes to allow comparison across studies. Second, there is a clear need for information on patient preferences (utilities) for different anesthesia management strategies and outcomes. For example, important tradeoffs are made between the advantages of pain control and depth of sedation on the one hand and the disadvantages of postoperative drowsiness and medication-related complications on the other. Bringing the patient perspective into our understanding of optimal anesthesia management strategies would be very helpful. A better understanding of surgeon preferences for alternative practices would also be important. Finally, the cost effectiveness of intravenous sedation and of monitoring by anesthesia personnel should be assessed. Our preliminary decision analysis suggests that the combination of oral sedation with a local block and an anesthesiologist on call may be the most cost-effective approach. However, further research in this area, which would include preference values collected from patients and additional clinical evaluation, is warranted before any final conclusion can be reached.