الفهرس 
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Abstract
Patient comfort, safety and low complication rates are the essentials of local anesthesia. The anesthetic requirements for ophthalmic surgery are dictated by the nature of the proposed surgery, the surgeon’s preference and the patient’s wishes.
The reduced toxic profile of levobupivacaine is beneficial for achieving higher plasma concentrations and dose without signs of cardiovascular or systemic toxicity. Furthermore, the success rate of cardiopulmonary resuscitation after toxic doses of levobupivacaine is higher compared to bupivacaine intoxication. There is a relative paucity of studies describing the use of levobupivacaine 0.5% for the standard peribulbar block (PB) or for superficial extraconal anesthesia.
The safety margin of ropivacaine is quite high, a higher volume is used in achieving the desired anesthetic effect due to a lower potency than bupivacaine while performing different surgeries thus raising the concerns of systemic toxicity.
Neuromuscular blocking drugs, such as vecuronium, and atracurium have also been added to the local anesthetic mixture and have been shown to improve the quality of peribulbar anesthesia. Atracurium, however, has histamine-releasing property and could result in undesirable local hyperemia. Rocuronium, on the other hand, is devoid of this adverse effect, has a faster onset of action, and its effects in a low dose on the quality of peribulbar anesthesia.
Aim of this study:
Was to compare efficacy and safety of sub-tenon’s and peribulbar block using different local anesthetic drugs for patients scheduled for phacoemulsification.
Patients and methods:
This prospective, randomized, double blind and clinical study was conducted on 400 patients underwent Phacoemulsification cataract surgery. These patients were randomly allocated into two equal groups: Group A received a Peribulbar block (PB) which equally divided into two subgroups, A1 patients underwent PB using levobupivacaine 0.5%, and A2 patients underwent PB using ropivacaine 0.75% plus rocuronium 0.06mg/kg. and Group B received sub-tenon block which divided into two subgroups B1 patients underwent Sub-tenon block using levobupivacaine 0.5%, and B2 patients underwent Sub-tenon block using Ropivacaine 0.75% with rocuronium 0.06mg/kg.
Patients on anti-glaucoma drugs, patients refusing LA, patients with a single eye, allergy to LA solutions, clotting abnormalities, history of sleep apnea, impaired mental status, and drug abuse. Were excluded from the study.
Pre-admission anesthetic assessment is highly desirable. Patients are often elderly and have co-morbidities requiring optimization prior to surgery. One day before surgery all patients were interviewed as the patients usually old with comorbidities detailed history, examination and routine investigations. V.N.P.R.S (0 = no pain to 10 = most severe pain) at 1njection, 1and 2h postoperatively Also explained.
Patient preparation:
All Patients were admitted to the operating room fasted for 6-8 hrs. And unpremedicated. A peripheral i.v. catheter 22G was inserted and standard monitoring Was conducted and recorded, including heart rate (HR), noninvasive arterial blood pressure, electrocardiogram (5 leads), and peripheral oxygen saturation (SpaO2).A nasal cannula was applied and supplemental oxygen was given throughout the procedure at 3 L/min.
Regional block techniques:
Technique in both groups was performed with the patient supine, head relaxed and eyes in primary gaze position during peribulbar while in sub tenon looks upwards and laterally.
1-Technique of peribulbar block:
The lower lid is retracted manually and the needle of a 25 gauge 16 mm with 10 ml plastic syringe is placed through the lower lid at the junction between the lateral and the middle third of the orbital rim. The needle passes close to the bone of the orbital floor backwards in a sagittal plane and parallel to the bone. When the needle tip is judged to be past the equator of the globe the direction is changed to point slightly medial (20o) and cephalic (10o upwards) to avoid the bony orbital margin. Following negative aspiration (to exclude intravascular puncture) up to 5-7 ml of the solution is slowly injected.
Technique of Sub-tenon’s (Episcleral) block
The injection is made while the patient in supine position. The conjunctiva is anaesthetized with topical 1-2 drops of benoxinate hydrochloride 0.4% given at intervals of 5 minutes, eye lid speculum is inserted at this point to improve access, 5% povidone iodine eye drops instilled before starting the block. Throughout the procedure, the patient is asked to look up and outwards to expose the inferonasal quadrant. A small tent of conjunctiva is raised with a pair of fine non toothed forceps approximately 5-10 mm away from the limbus small incision is made in the tented conjunctiva with a pair of ophthalmic scissors. The closed scissors are introduced through the aperture created and a tunnel is fashioned to the bare sclera by blunt dissection through tenon’s capsule. Sub-tenon’s metal cannula, 19-G, 25mm long and curved with a blunt end with the syringe of the anesthetic solution attached is then inserted through the incision. 3 to 6 ml of the local anesthetic is injected after aspiration to avoid intravascular injection occasionally.
Main outcome measures: The primary target of this current study was to compare efficacy as regard ocular akinesia score at 5, 10 and 15 min. after block, onset of sensory and motor block and verbal numerical pain rating scale at injection, 1 and 2hrs.postoperative. And safety as regard rate and incidence of complication of sub-Tenon’s and peribulbar block using different local anaesthetic drugs for patients scheduled for phacoemulsification cataract surgery.
The secondary measurements include: age, sex, weight, height and A.S.A. status, total volume of local anaesthetic used, intraocular pressure, eye lid score, and patient and surgeon satisfaction.
RESULTS:
Current study showed that as regards ocular akinesia The percentage of patients who developed successful akinesia (10 min after block)in peribulbar were significantly higher in the group A2 (78%) compared with the patients in the group A1 (65%) and in sub tenon there was no significant difference between B1 and B2.Also patients who developed successful akinesia in group B1 were significantly higher than A1.Also patients who developed successful akinesia in group B2 were significantly higher than A2. As regard V.N.P.R.S. the patients in the group A1 and B1 achieved lower values of verbal numeric rating scale of pain compared with the patients in the group A2 and B2, respectively, when comparing patients of group A1 with B1 and patients of group A2 with B2 they did not show any significant difference among the period from injection to 2 h postoperatively. As regard onset of sensory and motor block the onset of motor block (min) was significantly earlier in the A2 group compared with the patients in the A1 group. The onset of sensory block (min) was not significant between A1 group compared with the patients in the A2 group .in group B the onset of sensory and motor block did not show any significant difference between B1 and B2.
Conclusion
Peribulbar anesthesia using a mixture of rocuronium 0.06mg/kg and ropivacaine0.75% provides optimal orbital and eyelid akinesia for cataract surgery and shortens the block onset time. However, this does not significantly decrease the need for block supplementation with local anesthesia and that effects was not so obvious in sub-tenon group which may be attributed to sub-tenon technique which draw the local anesthetic directly to optic nerve and ciliary ganglia in contrast to peribulbar technique which depend mainly on diffusion.