Comparison of orbital muscle akinesia caused by rocuronium versus hyaluronidase mixed to the local anesthetic in single injection peribulbar block for cataract surgery.

BACKGROUND: The aim of this study was to compare orbital muscle akinesia caused by rocuronium versus hyaluronidase when mixed with the local anesthetic in single-injection peribulbar anesthesia (PBA). PATIENTS AND METHODS: Sixty patients were included in the study and subjected to cataract extraction using phacoemulsification technique with intraocular lens implantation. Group I received peribulbar block with 5 ml mixture of 30 IU/ml hyaluronidase and 2% lidocaine. Group II received peribulbar block with 5 ml mixture of rocuronium 5 mg and 2% lidocaine. The onset and duration of akinesia were assessed; the akinesia score at 2, 5, and 10 min was measured after injection. The need for supplementary injection was also recorded. RESULTS AND
CONCLUSION: PBA using a mixture of rocuronium and lidocaine provides optimal globe akinesia and faster establishment of suitable conditions to start eye surgery and shortens the block onset time as compared with the addition of hyaluronidase to lidocaine.

INTRODUCTION

Regional anesthesia, peribulbar block (PBA) for intraocular surgery is relatively safe, easy-to-perform. Many studies have demonstrated that PBA provided optimal conditions for cataract surgery.[1] It was first described as a specific local anesthetic block by Davis in 1986.[2] Little attention has been drawn to the technique of periocular infiltration because of its lower incidence of adverse effects as compared to the retrobulbar blockade, provides a reliable alternative to retrobulbar anesthesia.[3] However, the main disadvantage of peribulbar block is the use of long needles (1-1.25 inches), that may have the potential risk of optic nerve injury, retro-bulbar hemorrhage and globe perforation.[4]

The standard practice for extraconal injections is by using a 25-mm needle.[5] Rizzo et al.[6] described that the single-injection technique for percutaneous PBA with a short needle is a simple and easy technique with less pain, using a decreased volume of local anesthetic. It requires a single puncture with adequate anesthesia and analgesia.[7] PBA is associated with delayed and/or incomplete orbital akinesia[8] and the frequent need for block supplementation.[9] Over the last two decades, various modifications have been devised to reduce this technique complications and to augment its efficacy and hasten its speed of onset. Many adjuvant drugs such as adrenaline,[10] sodium bicarbonate, and hyaluronidase[1112] have been added to the local anesthetic mixture used for peribulbar block. However, their effects have been variable.

Neuromuscular blocking drugs, such as atracurium[13] and vecuronium,[14] have also been added to the local anesthetic mixture and have been shown to improve the quality of PBA. Histamine-releasing property of atracurium could result in undesirable local hyperemia. Rocuronium, on the other hand, is devoid of histamine-release, has a faster onset of action, and its effects in a low dose on the quality of PBA (onset time and need for supplemental injection with lower concentration of local anesthetics) have not been fully explored yet.

Hyaluronidase is an enzyme which catalyses the depolymerisation of hyaluronic acid to a tetra-saccharide and potentially decreases the viscosity of the tissue permitting a wider spread of injected fluids through tissue planes.[15] The use of hyaluronidase in retrobulbar anesthesia has been shown to be of benefit in terms of speed of onset and quality of block,[16] but the results with peribulbar techniques are more conflicting.[17]

The aim of this study was to compare the akinesia with the use of rocuronium versus that of hyaluronidase when mixed to the local anesthetic in single-injection peribulbar for cataract surgery.

PATIENTS AND METHODS

Sixty patients of American Society of Anesthesiologists I and II, aged from 50 to 70 years old, of both sexes were included in the study and subjected to cataract extraction using phacoemulsification technique with intraocular lens implantation by the same surgeon in Mansoura Ophthalmic Center. After written informed consent, approval of our Ethical Committee was achieved. Preoperative screening was done and patients who were having active infection or evidence of infection were not included, other exclusion criteria were sensitivity to local anesthetic drugs, history of convulsion or epilepsy, mental instability, difficulty in communication, orthopnea, severe uncontrolled hypertension, abnormal bleeding tendencies, extra-ocular muscles or eyelid abnormalities, previous intraocular injury or surgery, patients with posterior synechia, and ocular axial length more than 25 mm. Moreover, patients with hepatic, cardiac, chest, renal diseases were excluded from the study.

All patients were sedated with midazolam IV (0.02 mg/kg) 5 minutes before the block in the prepreation room. Then transferred to operating room and attached to the standard monitors (Electrocardiogram, peripheral oxygen saturation and noninvasive blood pressure) and nasal catheter for oxygen at a rate of 2-3 Liter/min. Patients were explained about the procedure involved in the peribulbar block and the use of visual analog scale (VAS) of 10 cm to evaluate the pain perceived by them; zero cm representing no pain and 10 cm representing the most severe pain.

Patients were randomly divided into two equal groups (30 patients each): Group I (n = 30): Hyaluronidase group received peribulbar block with 4.5 ml of a mixture of 30 IU/ml hyaluronidase (Hyalase® 1500 IU, Wockhardt, UK) plus 2% lidocaine (2% lidocaine HCl, Hospira, USA) and 0.5 ml normal saline. Group II (n = 30): Rocuronium group received peribulbar block with 5 ml of a mixture of rocuronium 0.5 ml (5 mg) and 2% lidocaine 4.5 ml.

Complete sterilization of the target eye by betadine, then the peribulbar block was performed, topical anesthesia to the conjunctiva by 0.4% benoxinate hydrochloride (Benox® 0.4%, E.I.P.I.CO., Egypt) drops applied immediately before performing the block. All injections were performed by the same anesthetist using a low volume (5 ml), single transcutaneous infero-lateral injection technique, and a 25-gauge, 25-mm bevel disposable needle.[18] Patients were asked to maintain the eye in the primary position. The injection site was identified at the junction of the lateral one-third and medial two-third of the inferior orbital rim in the infero-temporal quadrant. The needle was advanced in an antero-posterior, slightly medial, and cephalad direction. After aspiration, the anesthetic solution was injected in approximately 30s. Slight external manual pressure with of 4-5 layers of gauze piece was applied over eye immediately after injection for 5 minutes to promote the spread of local anesthetics and softening of the globe.[19]

Patient data were collected: Age, sex, weight, and the duration of operation. Analgesic onset was assessed by holding the bulbar conjunctiva both laterally and medially with toothed forceps. Reduction of ocular motility was considered the only reliably reproducible sign of the successful block.[20] The onset and duration of akinesia (absence of ocular movements in all four directions) (<1 mm) was assessed at 2, 5 and 10 minutes after injection with a 12-point scale. Each of the four rectus muscles and each lid was scored from 0 to 2; 0 = total akinesia, 1 = partial akinesia, 2 = no akinesia). The need for supplementary injection was also recorded.

Globe anaesthesia was assessed on 0-2 scale where 0 = no anaesthesia, 1 = partial but acceptable anaesthesia, 2 = complete anaesthesia. When akinesia and anesthesia were inadequate at 5 min, supplementary injection of 3ml lidocaine 2% was administered, in the same method, with additional assessments performed at 5 min intervals.

Increased intraocular pressure was assessed by palpation only (whether the eye felt tense or not). Patients were encouraged to communicate with the surgeon regarding pain and discomfort during surgery and assessed on VAS scale of 0-10 points. Sub-Tenon's supplementation was given with 2 ml of plain lidocaine by the surgeon if needed. Adverse effects (hemodynamics changes) and immediate complications due to the block were recorded (retrobulbar hemorrhage, hematoma, echymosis,) but Long-term complications were not reported in this study. The presence of pain in the first postoperative 24 h and the first need for any analgesic were also recorded.

Statistical analysis

Data were presented by mean ± standard deviation, and they were analyzed by Student's t-test. Results were considered significant if P < 0.05.

RESULTS

The demographic data showed no statistically significant differences in patient characteristics as regards sex, age, weight and duration of operations [Table 1].

Table 1

Patient characteristics

Globe analgesia, anesthesia and supplemental blocks were comparable in two groups as shown in Table 2. Globe akinesia and akinesia score were achieved significantly rapid in the Group II at 2, 5 and 10 min in comparison to Group I [Figure 1]. Twenty six patients (86.66%) in Group I and, twenty nine patients (96.66%) in Group II had adequate globe akinesia after respective peribulbar injection. Four patients (13.33%) in Group I and one patient (3.33%) in Group II required supplemental injections. Time to adequate condition to begin surgery was significantly shorter in Group II compared with Group I (P < 0.01) [Table 2].

Table 2

Globe analgesia, anesthesia, akinesia, and supplemental blocks

Figure 1

Akinesia score. Data are mean ± standard deviation. *P < 0.05 compared with Group I

The incidence of pain during surgery had similar rating for their intraoperative VAS scores and was statistically insignificant [Table 3]. Postoperative onset of pain (time of first analgesic request) were also statistically insignificant between two groups of study.

Table 3

Peri-operative pain (0-24 h)

Some block related complications were recorded in both groups, one patients of group I developed mild subconjunctival hemorrhage. Mild bruising at the injection site occurred in one patients of Group II. Hard eye with headache was noticed in two patient of Group I and three patients of Group II. They required gentle eye massage before operation. No patient needed general anesthesia or to cancel the operation because of a problem with the regional anesthetic block.

DISCUSSION

In our study, we compared the effect of adding a neuromuscular blocking agent (rocuronium) or hyaluronidase to the local anesthetic (lidocaine 2%) solution for PBA for cataract extraction using phacoemulsification technique with intraocular lens implantation.

Peribulbar anesthesia in eye surgery has been achieved by bulk spread of local anesthesia. The block is usually done using a single or double injection technique.[21] However, the choice between either single or double injection technique is based on the volume of the orbit, degree of required akinesia, ophthalmologist experience and preference of the anesthesiologist.[22] This study we used the single injection peribulbar block technique which is as effective as the standard two injection peribulbar block during eye surgery. The single injection peribulbar block is prefered to avoid possible globe injury that may occur due to second injection.[23]

In the present study, the rocuronium group (Group II) showed a better akinesia score. In contrast, onset akinesia was more rapid, leading to less delay in surgery and more suitable conditions to operate in <10 min versus Group I (hyaluronidase). The supplemental injection was required in 3.33% patients in Group II in comparison to 13.33% patients in Group I which resulted in satisfactory painless operating conditions. Ocular movement scores in patients who received rocuronium (Groups II) decreased by 50% at 2 min after block administration.

Adding neuromuscular blockers to the local anesthetic does not affect analgesia; they induce akinesia in extraocular muscles, so optimizing the setting for ophthalmic surgeries. The dose of rocuronium chosen in this study was less than one-tenth the dose administered intravenously for clinical neuromuscular blockade (standard intubation dose). This dose could be safe because it was used as a priming dose.[24]

The exact mechanism through which the local administration of a nondepolarizing muscle relaxant improves orbital akinesia is not known, but may be due to local direct effects at the muscles motor end-plate. This was planned so that in accidentally intravascular injection during block administration, the most adverse effects would be related to the local anesthetic mixture, not to rocuronium itself. Complications related to systemic absorption of the neuromuscular blocking agent were not observed. There are no data on the potential effects of a small dose of rocuronium if injected intrathecally in case of central spread of peribulbar local anesthetic. In this study, patients were constantly monitored in the operating room by an anesthesiologist who was prepared to intervene in the event of the remote theoretical chance of muscle weakness developing due to the central spread of anesthesia.

Our results are consistent with those reported by Reah et al.[14] who have demonstrated that the addition of vecuronium in a dose of 0.5 mg to a mixture of lidocaine 2%, bupivacaine 0.5%, and hyaluronidase 150 U improve globe and lid akinesia and hasten block onset time without side effects. Küçükyavuz and Arici[13] have also shown similar results when atracurium 5 mg was added to a standard mixture of lidocaine and bupivacaine without hyaluronidase. In addition, Aissaoui et al.[25] have reported that the addition of rocuronium 0.06 mg/kg to a local anesthetic mixture of 2% lidocaine and 0.5% bupivacaine improves the akinesia scores. The current study differed from that of Aissaoui et al. by using a fixed low dose of rocuronium (5 mg) as opposed to a variable dose based on body weight. Rocuronium group needed a lesser dose of the supplemental injection, reducing the rate of complications that may be attributed to repeated injection such as globe perforation and hemorrhage.[8]

The use of hyaluronidase as an adjunct to local anesthesia has been well documented in ophthalmological surgery allowing the local anaesthetic to disperse more extensively around the orbit and smaller volumes is needed as shown in our results. This could lead to a decrease in complications without loss of efficacy.[26] Hyaluronidase causes hydrolysis of hyaluronic acid by splitting the glucosaminidic bond between C1 of the glucosamine moiety and C4 of glucuronic acid. It decreases the viscosity of the intercellular cement, promotes diffusion of injected fluids, and facilitates the absorption of drugs mixed. Hyaluronidase causes more rapid spreading of subcutaneously injected agents and can be used in local anesthesia to increase the area affected, speeding the onset of anesthetic action. The rate of diffusion is proportional to the amount of enzyme.[27] So hyaluronidase could be used in retrobulbar or nerve block anesthesia before ophthalmic surgery to increase the hypotonic effect of local anesthetics.[28] We must mention that the side effects reported in our study were related to the peribulbar block itself, such as mild bruising at the injection site, headache, and mild subconjunctival hemorrhage.

CONCLUSION

PBA using a mixture of rocuronium 5 mg and lidocaine 2% provides optimal globe akinesia and faster establishment of suitable conditions to start eye surgery and shortens the block onset time compared with the addition of hyaluronidase to lidocaine 2% in cataract extraction using phacoemulsification technique with intraocular lens implantation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.