Optimal Dose of Dexmedetomidine Retrobulbar Anesthesia during Phacoemulsification Cataract Surgery.

BACKGROUND: The cataract surgery anesthesia should be to make the procedure as safe and as satisfactory as possible for all concerned. The recent progress in anesthesia and surgery now allow cataract extraction to be done with minimal physiological changes to the patient. We aimed in the study to compare between two different doses of dexmedetomidine combined with lidocaine and bupivacaine during retrobulbar anesthesia for cataract extraction by phacoemulsification.
MATERIALS AND METHODS: This study was done on forty patients with cataract. The patients were enrolled in two groups: Group (A):Twenty patients were received 1.5 ml 2% lidocaine + 1.5 ml 0.5% bupivacaine + 0.25 μg/kg of dexmedetomidine and Group (B): Twenty patients were received 1.5 ml 2% lidocaine + 1.5 ml 0.5% bupivacaine + 0.5 μg/kg of dexmedetomidine.
RESULTS: The globe anesthesia duration, globe, and lid akinesia were significantly longer in the Group B than in the Group A (P < 0.05). Intraocular pressure decreased through the first 15 min after anesthesia in the two groups, and the changes were not significant between the two groups but highly significant in every group when compared to its baseline reading. As regards the conscious level in the two groups, there was a significant difference (P < 0.001). Group A is higher regarding score 2 and 3, and Group B higher in score 4.
CONCLUSIONS: We concluded that dexmedetomidine 0.25 μg/kg, when added to retrobulbar block for cataract surgery, will significantly increase the duration of retrobulbar block and improve both the surgeon and the patient satisfaction.

INTRODUCTION

Most of the geriatric patients have a cataract and suffer from various systemic illnesses such as diabetes, hypertension, and cardiac disease.[1] Operation in this group of patients is always related to different risks, whether it is done under general anesthesia or regional anesthesia.[2]

The plan of cataract surgery anesthesia should be to make the procedure as safe and as satisfactory as possible for all concerned.[3] The recent progress in anesthesia and surgery now allow cataract extraction to be done with no harm to the patient. In addition to safety, all factors to be considered such as amnesia, analgesia, anesthesia, akinesia, and amaurosis.[4] We aimed in this study to compare two local doses of dexmedetomidine in their effect on the procedure of cataract extraction by phacoemulsification during retrobulbar anesthesia.

MATERIALS AND METHODS

After approval from the local Clinical Research Ethics Committee of Menoufia and Shebeen El Kom hospitals and written informed consent from the all patients, Forty patients of both sexes with physical status American Society of anesthesiologist (ASA) class I, II, III were undergoing cataract extraction by Phacoemulsification under Retrobulbar Anesthesia. The patients were arranged into two groups: Group (A): Twenty patients were received 1.5 ml 2% lidocaine + 1.5 ml 0.5% bupivacaine + 0.25 μg/kg of dexmedetomidine and Group (B): Twenty patients were received 1.5 ml 2% lidocaine + 1.5 ml 0.5% bupivacaine + 0.5 μg/kg of dexmedetomidine. Exclusion criteria: Patient refusal to local anesthesia even after careful counseling and an explanation of the risks involved, uncontrolled Parkinsonian patient, patient with severe medical condition to limit proper positioning to cataract surgery, the patient with history of severe reaction, allergy, or other complications to bupivacaine or lidocaine or dexmedetomidine, patient on anticoagulants. Patients with myopia (axial length is 26 mm or greater). Once arrived at the operative theater, we attached the patients to pulse oximetry electrocardiogram and noninvasive blood pressure monitoring; a 20-gauge cannula was inserted in the arm opposite to the side of the operation.

Surgical technique

Retrobulbar anesthesia technique

While the patient was in supine position. The eyelids and the surrounding areas were cleaned with povidone 5% solution. A volume of 3 ml of anesthetic solution was taken (1.5cc lignocaine 2%, 1.5cc of bupivacaine 0.5%) with the tested dose dexmedetomidine in a 5 cc syringe with a 23-gauge needle. While the eye in a primary position, the mixture was injected transcutaneously at the inferotemporal quadrant at the junction of the medial 2/3rd and lateral 1/3rd of the lower lid, with the needle direction toward the orbit floor and the bevel facing the globe after aspiration to avoid possible entry into a blood vessel. Compression to the eye was applied for a few minute.

Measurements

Before administration of retrobulbar blocks as a baseline:

Intraocular pressure (IOP) was being measured using a Schiotz tonometer, mean arterial pressure (MAP), SaO2, heart rate (HR).

After doing retrobulbar block assessment of the patient for the next

The start of globe anesthesia (seconds) (the ocular sensations)

The start of lid akinesia (seconds) (the movements of eyelid)

The start of globe akinesia (seconds) (ocular muscles movement)

IOP was being measured using a Schiotz tonometer before local anesthesia injection and every 5 min after injection for three times before starting the operation

HR (beat/min) was be measured every 5 min till the end of the operation

MAP (mmHg) was be measured every 5 min till the end of the operation

Oxygen saturation (percent %) was be measured every 5 min till the end of the operation

Sedation levels were assessed by Ramsay Sedation Score.[5]

Patient is anxious and agitated or restless

Patient is cooperative, leaning, and calm

Patient obeys orders only

Patient shows a fast reaction to a light glabellar tap or noisy stimulus

Patient shows a slow response to a light glabellar tap or noisy stimulus

Patient with no response.

Postoperatively, the patients were being kept in a recovery unit and be observed for the return of ocular movements.

The patients were asked to express their feeling toward the sedation/analgesia that was given during the operation (the patient satisfaction using a 7-point Likert-like verbal rating scale)

The surgeon was asked to rate his/her pleasure with the patient sedation using the same method and scale[6]

Globe anesthesia duration

Lid akinesia duration

Globe akinesia duration

Duration of surgery.

We discharged all the patients on the next morning of surgery.

Statistical analysis

After collecting the results, we tabulated it and statistically analyzed by an IBM compatible personal computer with SPSS statistical package version 20 (SPSS Inc. Released 2011. IBM SPSS Statistics for Windows, version 20.0, (IBM Corp., Armnok, NY, USA).

Statistical analysis was done

Descriptive statistics, for example, was expressed in number (no), percentage (%) mean (X̄) and standard deviation. ANOVA test used with P is significant if P < 0.05

Analytic statistics

Student's t-test is a test of significance used for comparison of quantitative variables between two groups of normally distributed data, while Mann–Whitney's test was used for comparison of quantitative variables between two groups of not normally distributed data

Chi-square test (χ2) was used for categorical values as data expressed in the number of patients or ratio (ASA classification, number of patients required analgesia and adverse effects). Whenever any of the expected cells were <5, Fischer's exact test with Yates correction was used.

P < 0.05 was considered statistically significant.

RESULTS

All the demographic data such as age, sex, weight, side of the eye operated, axial length, ASA status, and surgery duration were compared in the two groups, and they were statistically nonsignificant (P > 0.05) as in Table 1.

Table 1

Demographic data

As regards the surgery duration in both groups, there was no significant discrepancy. There were no significant changes between the study groups (P > 0.05) as regarding the onset times of lid akinesia, globe anesthesia, and globe akinesia. The globe anesthesia duration, globe akinesia and lid akinesia in the Group B were significantly longer than in Group A (P < 0.001) [Figure 1].

Figure 1

Onset and duration of block

In both groups, IOP decreased throughout the first 15 min after the administration of the local anesthesia with insignificant changes between both groups [Table 2].

Table 2

Comparative evaluation of intraocular pressure in the Groups A and B at different time intervals

In every group, there was a significant difference between the measurements and the baseline reading [Table 3].

Table 3

Comparative evaluation of intraocular pressure at different time intervals to the baseline inside the same group

As regards the HR, it was significantly lesser in Group B than Group A at 20, 25, 30, 40, and 50 min after injection of local anesthesia (P = 0.02) [Figure 2]. MAP was significantly lesser in Group B than Group A after 20, 25, 30, and 40 min (P < 0.05) [Figure 3].

Figure 2

Heart rate (beat/min) in the Groups A and B at different time intervals

Figure 3

Mean arterial pressure (mmHg) in the Groups A and B at different time intervals

As regards the oxygen saturation percent (%), there was insignificant variation between both groups (P > 0.05). Regarding the conscious level, there was a highly significant variation between the two groups (P < 0.001). Group A is higher regarding 2 and 3, and Group B higher in 4 [Table 4].

Table 4

Comparative evaluation of conscious level by Ramsay sedation score in the Groups A and B

Regarding the patient's satisfaction for anesthesia in the two groups, there was insignificant difference between them (P > 0.05) [Table 5].

Table 5

Patients satisfaction for anesthesia (7-point Likert-like verbal rating scale)

Surgeon satisfaction was statistically considerable higher in the Group A than in the Group B (P < 0.001) [Table 6].

Table 6

Percentage of surgeons satisfaction for anesthesia (7-point Likert-like verbal rating scale

DISCUSSION

The ophthalmic surgical procedures under regional anesthesia provide clear and immobile operative field, cardiovascular stability, low-normal IOP, and excellent communication between the patient and the surgeon. Although regional block provides akinesia and analgesia, appropriate sedation has the advantage that it lower the IOP and pain during the operation, prevent anxiety with its hypertensive response, and make the patient calm.[7] Dexmedetomidine is a selective and specific α2-adrenoceptor agonist, with sedative effects for patients in intensive care or also has an advantageous roles during the eye surgery on the ocular pressure. As regards the globe anesthesia duration, lid akinesia and globe akinesia, there was insignificant changes between both groups (P > 0.05) in agreement with our result. Madan R et al. found the same result during their study on the effect of three different concentration of clonidine in the peribulbar block in cataract surgery.[8] Furthermore, Rajendra et al. in their study comparing the clonidine 0.5 μg/kg with dexmedetomidine 0.5 μg/kg showed that no considerable variation in the onset of anesthesia, lid akinesia as our result.[9] The globe anesthesia duration, globe akinesia, and lid akinesia in the Group B were significantly longer than in Group A (P < 0.001). In agreement with this result, Channabasappa et al. on their study on the outcome of dexmedetomidine in two different doses 50 μg (D50) and 25 μg (D25) in peribulbar block, they found that D50 increase the global anesthesia duration, lid akinesia, and globe akinesia.[10] Furthermore, Reem and Mohamed, in their study, they concluded that addition of 1 μg/kg dexmedetomidine to the lidocaine–bupivacaine mixture in a peribulbar block improves the lid akinesia duration and duration of globe akinesia.[11] The akinesia duration in our study was comparable to Mohamed et al., who evaluated the outcome of adding two different doses dexmedetomidine to bupivacaine and lidocaine in peribulbar anesthesia and concluded that this prolongs the akinesia duration.[12] As regards the IOP, a significant decrease from the baseline was found in both groups with no considerable variation between both groups at the measured times during the 15 min next to dexmedetomidine injection and this is in agreement with the study of Abdelhamid et al. who showed reduction in the IOP after both local and IV dexmedetomidine during their study on cataract surgery by peribulbar block.[13] The dexmedetomidine effect on the IOP may be due to decrease production of aqueous humor secondary to its direct vasoconstrictive effect on the afferent blood vessels of the ciliary body Furthermore, because of its reducing sympathetic output with of vasomotor tone reduction of ocular muscle, it could also facilitate the drainage of aqueous humor.[14] Furthermore, Virkkilä et al. found that intramuscular 1 μg/kg dexmedetomidine produced a significant reduction in the IOP before, during, and after the cataract operation.[15] Furthermore, Lee et al. on their study using infusion of dexmedetomidine in vitreoretinal surgery during isoflurane anesthesia, found that there were significant variation between the both groups regarding the baseline while no significant changes between the both groups at the times of measurements.[16]

There was a significant variation as regards the HR and mean blood pressure between both groups which were lesser in Group B after 20, 25, 30, 40, and 50 min than Group A. In agreement with our result, Naik et al. showed during their study on the outcome of dexmedetomidine (1 μg/kg) added to local anesthesia in retrobulbar block that there were reduction in the HR and mean blood pressure after injection and this can be explained by the absorption of the drug take this time to produce the systemic hemodynamic effect.[17] As regards the conscious level, the mean sedation scores were significantly different between both groups (P < 0.001). Group A is higher regarding sedation score 2 (11 patients [55%]) and score 3 (9 patients 45%), and Group B is higher in score 4 (15 patients 75%) in agreement with our result. Gelil showed the improved in sedation state after adding dexmedetomidine to local anesthesia in retrobulbar block;[18] this difference was favorable for dexmedetomidine as it efficiently suppress nociceptive signals transmission in the spinal cord when it joins to pre- and post-synaptic receptors causing sedation, analgesia, and adequate quality anesthesia also, in agreement with our result. Ye et al. found increased sedation level in patients receiving dexmedetomidine 0.1ug with local anesthesia in their study on the use of dexmedetomidine locally in retrobulbar block for implant of orbital ball.[19] This result is similar to the results obtained by Oriol et al. who added dexmedetomidine to the local anesthetics in the epidural block to decrease worry and helps the patient to be in a state of active sedation.[20]

There was no considerable difference between both groups (P > 0.05) as regards the patient's satisfaction for anesthesia; surgeon satisfaction was significantly evident in Group A than in Group B (P < 0.001). Moreover, this can be explained by increase sedation level in group dexmedetomidine 0.5 μg which interfered with appropriate communication between the surgeon and the patient during the operation.

Memis et al. who mentioned that the quality of anesthesia and perioperative analgesia improved by adding 0.5 μg/kg dexmedetomidine to lidocaine 1% with no side effects.[21]

CONCLUSIONS

The retrobulbar block for phacoemulsification cataract surgery, 0.5 μg/kg of dexmedetomidine as an adjuvant to 2% lidocaine and 0.5% bupivacaine significantly increases the retrobulbar block duration in comparing to 0.25 μg/kg while the surgeon satisfaction is significantly better with 0.25 μg/kg dexmedetomidine.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.