Date Published: August 8, 2012
Publisher: Hindawi Publishing Corporation
Author(s): Waleed Riad, Nauman Ahmed, Emad Abboud, Essam Al-Harthi, Eman Kahtani.
Peribulbar block is commonly used for ocular posterior segment surgery. This work aimed to compare the efficacy of using 12.5 mm to 25 mm standard needle length in performing single injection peribulbar block for retinal surgery. Peribulbar block was performed in 120 patients using either standard 25 mm or 12.5 mm 30 G needle (insulin needle). While applying digital pressure around the needle hub, 8–10 mL of local anesthetic are injected. Ocular movement was assessed at 5 and 10 min using simple akinesia score (0–8). If after 10 min score was >1, supplementary injection was given. Visual analogue scale (0–10) was used at the end of the procedure to assess surgeons’ satisfaction and patients’ intraoperative pain. No differences in akinesia score at 5 & 10 min (P = 0.34 and 0.36, resp.). Initial volume injected was comparable between groups (P = 0.31), however total volume of local anesthesia and supplementary injections were significantly higher in 12.5 mm group (P = 0.03 and 0.01, resp.). No difference as regard surgeons’ satisfaction and patients’ intraoperative pain (P = 1.0 and 0.18, resp.). Peribulbar block with 12.5 mm needle together with digital compression is a suitable alternative to the standard block with 25 mm needle length for retinal surgery.
Regional anesthesia is standard technique for most ophthalmic procedures including ocular posterior segment procedures. In many parts of the world, retrobulbar anesthesia has almost been replaced by peribulbar technique because of higher margin of safety and fewer side effects. The advantages of this approach also include less disruption to the patient’s physiology, rapid return to normal routines, and better utilization of hospital beds and economy . Peribulbar anesthesia that consists of introducing a needle into the extraconal space should theoretically be safer than retrobulbar anesthesia as it is away from the vessels and optic nerve. It is based on the principle of tissue compartments. When a needle is inserted in one compartment and the local anesthetic injected, it will spread under the effect pressure and volume to other compartments. Therefore, the local anesthetic injected into the extraconal space should spread to the intraconal space to provide anesthesia and akinesia of the globe .
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.
One hundred and twenty patients were enrolled in this prospective randomized double-blinded study. Demographic and descriptive data are shown in Table 1. No difference between groups observed as regard age, weight, height, sex, ASA classification and duration of surgery.
The current work showed that posterior segment surgery could be performed with insulin needle. The orbit could be divided into three spaces (anterior, mid, and posterior) for better understanding of the relationship of injection site. The anterior orbit ends 2–5 mm anterior to the equator of the globe and is filled primarily with connective tissue . Insertion of longer needles deep into the orbit increases the potential of injury to important structures and limiting the depth of needle insertion may limit needle injury . In an interesting study, Scott and collaborators clearly reported that a 16 mm needle reaches to the junction between anterior and mid orbit and cannot pass beyond . It is logical the 12.5 mm needle length will rest only in the anterior orbit if it was not pushed posteriorly. If globe perforation happened by the short needle. If inadvertent globe perforation and/or penetration occurred by the short needle the consequences should be less severe than longer needle as it does not involve the optic nerve, fovea, and ophthalmic artery located in the posterior orbit.
Using 12.5 mm needle length (insulin needle) for peribulbar blockade showed agreeable results compared to the standard 25 mm needle length. This technique is a suitable effective alternative for posterior segment surgery.