Supplementation of retrobulbar block with clonidine in vitreoretinal surgery: effect on postoperative pain

Efficacy of adjuvants in ophthalmic regional anesthesia: A systematic review and network meta-analysis

PURPOSE

This network meta-analysis aims to determine the differences between adjuvants that are used in combination with local anesthetics for ophthalmic regional anesthesia.

DESIGN

Systematic review and network meta-analysis METHODS: A systematic literature search for randomized controlled trials, comparing the impact of adjuvants in ophthalmic regional anesthesia, in Embase, CENTRAL, MEDLINE and Web of Science was performed. Risk of bias was evaluated using the Cochrane risk of bias tool. Frequentist network meta-analysis was performed using a random effects model with saline as the comparator. Primary endpoints were the onset and the duration of sensory block and globe akinesia, as well as the duration of analgesia. Summary measure was the ratio of means (ROM). Secondary endpoints were the rates of side effects and adverse events.

RESULTS

39 trials were identified as eligible for network meta-analysis, including 3046 patients. 17 adjuvants were compared in the most extensive network (onset of globe akinesia). The addition of fentanyl (F), clonidine (C) or dexmedetomidine (D) showed the best overall results. Onset of sensory block: F 0.58 [CI 0.47-0.72], C 0.75 [0.63-0.88], D 0.71 [0.61-0.84], onset of globe akinesia: F 0.71 [0.61-0.82], C 0.70 [0.61-0.82], D 0.81 [0.71-0.92], duration of sensory block: F 1.20 [1.14-1.26], C 1.22 [1.18-1.27], D 1.44 [1.34-1.55], duration of globe akinesia: F 1.38 [1.22-1.57], C 1.45 [1.26-1.67], D 1.41 [1.24-1.59], duration analgesia: F 1.46 [1.33-1.60], C 1.78 [1.63-1.96], D 1.41 [1.28-1.56].

CONCLUSION

The addition of fentanyl, clonidine or dexmedetomidine showed beneficial effects regarding onset and duration of sensory block and globe akinesia.

Effect of adding clonidine to lidocaine on ocular hemodynamics during sub-Tenon's anesthesia: randomized double-blind study

INTRODUCTION AND OBJECTIVES

Different regional anesthesia techniques for ophthalmology can have hemodynamic effects on the eye. We assessed the effects of adding clonidine to lidocaine on Intraocular Pressure (IOP), Ocular Pulse Amplitude (OPA), and Ocular Perfusion Pressure (OPP) after the sub-Tenon's technique for cataract surgery.

METHODS

The study included 40 patients randomly allocated into two groups: sub-Tenon's blockade with Lidocaine plus Saline Solution (LS) or Lidocaine plus Clonidine (LC). IOP, OPA and OPP were measured before anesthesia, and 1, 5 and 10 minutes after the injection of anesthetic solution.

RESULTS

There was no difference between the groups in IOP, OPA, and OPP baseline values. After the injection of the anesthetic solution, the IOP increased in both groups at minute one, with a mean difference of +4.67 mmHg (p = 0.001) and +2.15 mmHg (p = 0.013) at 5 minutes. The increase was lower in the LC group when compared to LS (p = 0.027). OPA decreased in both groups, with a baseline difference, after 1 minute, of -0.85 mmHg (p =  -0.85 mmHg (p = 0.001), and at 5 and 10 minutes with differences of -1.17 (p = 0.001) and -0.89 mmHg (p = 0.001), respectively. The highest decrease was observed in group LC in relation to group LS (p = 0.03). There was no difference in OPP in relation to baseline measurements.

CONCLUSIONS

Adding clonidine to lidocaine for sub-Tenon's anesthesia reduced IOP and OPA without significant changes in OPP.

Efficacy of ropivacaine versus bupivacaine in preventing peribulbar block failure: A meta-analysis

PURPOSE

Peribulbar block is considered a standard of care in ophthalmological practice due to its easy execution and minor complications. There is a paucity of studies confirming efficacy between ropivacaine and bupivacaine for this specific technique. We evaluated the efficacy of ropivacaine or bupivacaine in preventing total or partial peribulbar block failure in ophthalmic surgeries.

METHODS

Meta-analysis of randomized clinical trials, comparing patients submitted to ophthalmic surgeries under peribulbar anesthesia with ropivacaine and bupivacaine. We searched in different databases for articles published until March, 2018. Data on patients, anesthesia, procedures and akinesia were tabulated. After calculating the chi-square of heterogeneity, we adopted a random-effects model with DerSimonian-Laird test, as well as an odds ratio and a 95% confidence interval.

RESULTS

From the 310 articles identified, 21 studies were selected. The use of ropivacaine was considered a protective factor for ocular akinesia failure in peribulbar block when compared to bupivacaine (OR = 0.53, 95% CI = 0.35-0.81 and p value = 0.003).

CONCLUSIONS

In ophthalmic surgeries, ropivacaine in peribulbar anesthesia is associated with lower rate of block failure when compared to bupivacaine.

Effect of clonidine added to lidocaine for sub-Tenon's (episcleral) anesthesia in cataract surgery

PURPOSE

We aimed to evaluate the duration of anesthesia, analgesia and ocular akinesia of clonidine added to lidocaine in sub-Tenon's anesthesia in patients undergoing cataract surgery.

METHODS

Forty patients were prospectively enrolled. They were randomized to two sub-Tenon's anesthesia groups: group L (6 ml of lidocaine 2 %, 1 ml of 0.9 % saline and 25 UI/ml of hyaluronidase), and group C (6 ml lidocaine 2 %, clonidine 1 μg/kg, 1 ml of 0.9 % saline and 25 UI/ml of hyaluronidase). Duration of sensory anesthesia, ocular akinesia in all directions, akinesia of the levator palpebrae superioris and orbicularis oculi muscles, the duration of analgesia (time to the first postoperative use of analgesics), the overall use of analgesics and the presence of adverse effects were recorded .

RESULTS

The duration of sensory anesthesia and akinesia of the four rectus, levator palpebrae superioris, and orbicularis oculi muscles was significantly longer in group C (p < 0.05). The number of patients who required analgesics was similar between the groups but the duration of analgesia was longer in group C (p < 0.05). No significant adverse effects were observed.

CONCLUSION

The addition of clonidine 1 μg/kg to 2 % lidocaine in sub-Tenon's anesthesia for cataract surgery increased the duration of sensory anesthesia, ocular akinesia, and the duration of analgesia.

Clonidine as an adjuvant to prolong local analgesia in conventional scleral buckle surgery

PURPOSE

The aim of this study was to determine the effect of a single dose of 150 μg of clonidine as an adjuvant to levobupivacaine (Chirocaine(®)) in retrobulbar block on postoperative safety and analgesia.

METHODS

This was a prospective, randomized, controlled, double-blind trial. One hundred twenty patients with a rhegmatogenous retinal detachment scheduled to undergo external buckling surgery and cryocoagulation were asked to participate. Participants were randomly assigned either to receive 3-5 mL Chirocaine (22.5-37.5 mg) or 3-5 mL Chirocaine and 1 mL clonidine (150 μg) before surgery. Main outcome measures were postoperative pain, use of analgesics, blood pressure, and plasma clonidine concentration. Nine nonrandomized patients consented to give blood samples for pharmacokinetic analysis.

RESULTS

There was no significant difference in pain score between both groups. On average, the use of analgesic medication occurred later in the clonidine group (P=0.0004), but there was no statistical difference in the first time that postoperative medication was taken (P=0.13). Blood pressure was reduced by clonidine (systolic: P=0.02, diastolic: P=0.006). Clonidine levels could be demonstrated during the 24-h postoperative period, with an average half-life of 22 h.

CONCLUSIONS

Administration of clonidine as an adjuvant to conventional retrobulbar block is safe, and delays the postoperative use of analgesics. The reduction of postoperative pain and the time of first use of analgesic medication, however, were not significantly different between groups. Further, pain scores in both study groups remained low. Therefore, the beneficial effect of clonidine in conventional scleral buckle surgery appears to be limited.