One hundred and twenty patients undergoing Pars Plana Vitrectomy (PPV) under regional anesthesia were enrolled in this prospective randomized double-blinded study, after approval of the hospital Research and Human ethics committees, and informed patient written consent, were obtained. Regional block was performed using a disposable insulin needle of 30 G and 12.5
mm needle length (Becton Dickinson, BD Microlance 3, Benelux, Belgium). Anesthesia was performed by either of the anesthesiologists investigators (WR or NH) involved in the study. Exclusion criteria include patients allergic to local anesthetic solutions; with local sepsis, serious impairment of coagulation, and orbital abnormalities; or who were unable to cooperate in maintaining a relatively motionless supine position; or who refused the anesthetic technique.
On the day of surgery, patients were requested to fast 6 hours and premedicated with hydroxyzine 0.5–1.5
, paracetamol with codeine (Revacod) 10–15
one hour before surgery according to the standard practice of the institute. On arrival of the patient in the preoperative holding areas, baseline globe movements in the major directions of gaze (superior, inferior, medial, and lateral) were assessed. Standard monitoring of ECG, pulse oximetry, and noninvasive blood pressure were started and venous access was initiated.
Patients were randomly allocated using a computer generated numbers and sealed envelope to either group. Peribulbar block performed through insertion of the standard 25 gauge, 25
mm needle length (Group 1), or 30 gauge, 12.5
mm needle length (Group 2). The 12.5
mm needle was initially designed for administration of subcutaneous insulin or tuberculin test. In both groups, the needle inserted through the lower eyelid as far lateral as possible in the inferotemporal quadrant, just above the inferior orbital notch. It is inserted perpendicularly to the skin until the hub rested on the inferior orbital bony rim. This typically allows fixation of the needle in position and prevent its migration backward during injection. Digital pressure was applied by the thumb and index fingers around the needle hub during injection. This prevents needle from further displacement and promotes a posterosuperior spread of injectable instead of accumulation into the lower eyelid. After negative aspiration,a volume of 8–10
mL of local anesthetic solution of Bupivacaine 0.5%, Lidocaine 2% in a ratio of 3
2 (Astra, Astra Sodertalje, Sweden) with hyaluronidase 5
(CP Pharmaceutical Ltd, Wrexham, United Kingdom) was injected until total drop and fullness of the upper eyelid. No pressure reducing device (Honan's balloon) was used, however intermittent digital message of the eye was applied. Ocular movements were assessed 10 minutes after the block. A simple akinesia scoring system was used [12
]. Eyes movement in four directions is elicited superiorly, inferiorly, nasally, and temporally. A normal movement score two, partial movement score one, and flicker or no movement score zero. Merging the four directions of ocular movement, a maximum score of eight and a minimum score of zero could be achieved. Using this scale, an ocular mobility was assessed at five and 10
min after block by an observer who was unaware about the needle used for block. A score of one or zero was accepted to allow the surgeon to operate. If after 10
min, the required degree of block was not achieved, a supplementary anesthesia was provided. This means addition of 3–5
mL anesthetic solution either medially if the movement is medial or inferior or superiorly if the movement is lateral or superior using the same needle used for the primary block. Surgeons who were blind to the technique used were asked to rate their satisfaction with the anesthetic technique using a scale from 0 (total dissatisfaction) to 10 (total satisfaction). Similarly at the same time, Visual analogue scale was used to assess the patients' level of pain (0 = no pain to 10 = worst pain ever). Any complication and additional supplementation of local anesthetics were documented.
2.1. Statistical Analysis
The results were analyzed using the Statistical Package for Social Science for Windows version 14 (SPSS Inc., Chicago, IL, USA). Sample size was calculated using N-Query software version 4, it indicated that 60 subjects were required in each arm to detect a difference of 0.5 in the mean of simple akinesia score which is the primary objective when α error equals 0.05 and β error equals 0.20. Numerical data were analyzed using independent sample, two-tailed t-test, and e expressed as a mean and standard deviation (SD). On the other hand, categorical data were analyzed by chi-square test and expressed in number and percentages. P value of 0.05 was used as the level of significance.