Perioperative Dexmedetomidine for outpatient cataract surgery: a systematic review

Methodological quality of the review: Low confidence

Author: Jones JH, Aldwinckle R.

Region: Not reported

Sector: Service delivery

Subsector: Quality of clinical care

Equity focus: Not stated

Review type: Other review

Quantitative synthesis method: Narrative synthesis, systematic review

Qualitative synthesis method: Not applicable

Background:
Cataract surgery is one of the most common procedures performed worldwide on the elderly. Various medications can provide effective anesthesia and analgesia for cataract surgery, but undesirable side effects limit the utility of each medication or combination of medications. Dexmedetomidine may serve as an anesthesia adjunct for outpatient cataract surgery in the elderly.

Objectives:
Investigate the use of dexmedetomidine for sedation in adult patients undergoing outpatient cataract surgery.

Main findings:
A total of 15 studies were included in this review. Although each study in this review utilised a randomised design, the method of randomisation was frequently inappropriate and led to decreased quality scores.

Authors found that hypotension, with or without bradycardia, was reported following bolus doses of dexmedetomidine ranging from 0.5-1.0 mcg/kg, with or without a continuous dexmedetomidine infusion. Authors reported that cardiovascular depressions were noted with dexmedetomidine, as evidenced by statistically significant decreases in arterial pressure, heart rate, or both. Administration of dexmedetomidine by continuous infusion without initial bolus was not associated with statistically significant decreases in arterial pressure when compared to remifentanil, midazolam and saline. However, when compared to propofol-alfentanil, dexmedetomidine infusion titrated to RSS 3 without initial bolus dose led to statistically significant decreases in systolic blood pressure intraoperatively and postoperatively.

Authors found no statistically significant differences in oxygen saturation (SpO2), end-tidal carbon dioxide (ETCO2) values or respiratory rates reported in studies investigating the respiratory effects of dexmedetomidine compared to saline; no sedation; midazolam and fentanyl; propofol and alfentanil; and ketamine and propofol.

Findings from the review showed inconsistent results among studies that investigated pain perception during regional blocks and postoperative analgesia with dexmedetomidine compared to other study medications.

Authors note that delayed PACU discharge times were associated with the use of dexmedetomidine, but no clear association was identified between delayed recovery and higher levels of intraoperative sedation. Better analgesia and higher patient satisfaction were commonly reported with dexmedetomidine, as well as reductions in IOP.

Overall, authors conclude that this review demonstrates better analgesia, higher patient satisfaction and reduced IOP with dexmedetomidine for outpatient cataract surgery when compared to traditional sedatives, hypnotics, and opioids. These benefits of dexmedetomidine, however, must be weighed against relative cardiovascular depression and delayed PACU discharge or recovery times. Therefore, the utility of dexmedetomidine for outpatient cataract surgery should be considered on a patient-by-patient basis.

Methodology:
Authors performed literature searches in PubMed, Embase, and Cochrane databases for articles published before 1 January, 2019. Additionally, the bibliographies of recovered publications were screened for relevant titles, which were then also reviewed. Eligible studies included randomised clinical trials of adult patients undergoing outpatient, or ambulatory, cataract surgery with sedation supplemented by topical analgesia or peribulbar block.

The quality of each study was assessed with three measures and given a score between 0 and 5. One point was awarded if the study was randomised and another point was awarded if the study utilised a double-blind approach. Additional points were given based on the appropriateness of randomisation and blinding, and if the study included a clear description of withdrawals or dropouts (or specifically stated that there were none). Points were not awarded for inappropriate randomisation or blinding.

Applicability/external validity:
Authors do not discuss the applicability or external validity of findings, but reported several limitations which preclude meta-analysis.

Geographic focus:
Geographic locations of included studies were not reported in the review.

Summary of quality assessment:
There is low confidence in the conclusions about the effects of this study, as important limitations were identified. Thorough searches of the literature were not conducted to ensure that all relevant studies were included in the review. Additionally, authors did not use reliable methods when screening studies for inclusion and extracting data of included studies. Lastly, it is not clear if authors used a validated tool to assess the quality of included studies.