Glyxambi
Home About us Editorial board Ahead of print Current issue Search Archives Submit article Instructions Subscribe Contacts Login 
  • Users Online: 3745
  • Home
  • Print this page
  • Email this page


 
   Table of Contents      
LETTER TO THE EDITOR
Year : 2019  |  Volume : 67  |  Issue : 7  |  Page : 1247-1248

Commentary: Role of alpha-2 agonists in regional ophthalmic anesthesia


1 Advanced Eye Centre, Postgraduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Anaesthesiology and Intensive Care, Postgraduate Institute of Medical Education and Research, Chandigarh, India

Date of Web Publication25-Jun-2019

Correspondence Address:
Dr. Mohit Dogra
Postgraduate Institute of Medical Education and Research, Chandigarh - 160 012
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijo.IJO_170_19

Rights and Permissions

How to cite this article:
Singh SR, Saini V, Singh A, Dogra M. Commentary: Role of alpha-2 agonists in regional ophthalmic anesthesia. Indian J Ophthalmol 2019;67:1247-8

How to cite this URL:
Singh SR, Saini V, Singh A, Dogra M. Commentary: Role of alpha-2 agonists in regional ophthalmic anesthesia. Indian J Ophthalmol [serial online] 2019 [cited 2019 Oct 16];67:1247-8. Available from: http://www.ijo.in/text.asp?2019/67/7/1247/261008



Regional anesthesia is the most common mode of anesthesia used in ophthalmic surgical procedures. Among regional blocks, peribulbar anesthesia is the safest and most commonly used. However, in procedures with prolonged operating time such as vitreoretinal surgeries, repeated need for block supplementation and patient anxiety are a challenge. Adjuvants to peribulbar anesthetics such as hyaluronidase and adrenaline along with preoperative anxiolytics/sedatives have been tried to overcome these challenges.[1] Alpha2 agonists are drugs that bind selectively to alpha2 adrenergic receptors in the central, peripheral, and autonomic nervous system as well as in vital organs and blood vessels. They produce dose-dependent analgesia, anxiolysis, and sedation without causing respiratory depression by acting on the G-protein-coupled alpha2 receptors.[2]

Two main alpha2 agonists that are commercially available include clonidine and dexmedetomidine. Although neither of them is completely selective for alpha2 receptors, dexmedetomidine is 8–10 times more selective toward these receptors compared with clonidine. Dexmedetomidine has a higher avidity and affinity for alpha2 receptors, shorter elimination half-life, and higher clinical efficacy with a lesser side effect profile compared with clonidine.[3] The study by Gujral et al. adds credence to the anxiolytic effect of dexmedetomidine which is coupled with hemodynamic safety in patients receiving peribulbar block for vitreoretinal surgery.[4]

Clonidine was the first alpha2 agonist to be used as an adjuvant by Mjahed et al., who found that its addition to peribulbar block decreased intraocular pressure, enhanced anesthesia, akinesia, and intraoperative sedation.[5] However, use of clonidine was associated with hemodynamic side effects such as bradycardia, arterial and orthostatic hypotension, rebound hypertension, and syncope. The long half-life of clonidine meant that the hemodynamic instability was not only seen intraoperatively but also for upto 8 h in the postoperative period.[6] Dexmedetomidine, a newer alpha2 agonist, has shown potential with a better safety profile due to its higher selectivity and shorter half-life. Two recent studies have evaluated its efficacy and side effect profile when used as an adjunct to peribulbar block during vitreoretinal surgery.[7],[8] Ahmed et al.[7] used 20 μg of dexmedetomidine along with lidocaine, bupivacaine, and hyaluronidase. They found faster onset of anesthesia, akinesia, increased duration of anesthesia, and increased patient sedation in comparison to a control group using normal saline. EL-Shmaa et al.[8] compared two doses of dexmedetomidine – 15 and 30 μg – as adjuvants to routine peribulbar anesthetic agents. They also found similar results in terms of onset and duration of anesthesia in the dexmedetomidine groups compared with the control group. The two doses did not differ significantly in terms of their efficacy or side effect profile. This study in contrast did not find any difference in the time of onset of anesthesia between the study and the control group; however, the patient and surgeon comfort was significantly better with dexmedetomidine. This study is also unique in keeping the systemic stability as its primary outcome measure.[4] No significant systemic side effects have been reported with either of the studies while using this drug in vitreoretinal surgeries.

There is increasing evidence that supports the use of dexmedetomidine as an adjunct to regional blocks for ophthalmic anesthesia. This drug seems to be especially useful in cases with prolonged operating times such as complex vitreoretinal surgeries and for apprehensive patients. However, use of dexmedetomidine in patients with heart block, heart failure, renal/hepatic insufficency, uncontrolled diabetes, obesity, and/or chronic obstructive pulmonary disease is contraindicated. Meticulous preoperative evaluation by the anesthesia team is thus essential before subjecting a patient to peribulbar block with dexmedetimidine as an additive. Establishment of standard preanesthetic evaluation and intraoperative monitoring protocols are needed before this drug gains popularity as an adjunct for regional anesthesia in ophthalmic surgery. Hence, further studies on the requirement of systemic monitoring during surgery and long-term safety profile of these agents are warranted.



 
  References Top

1.
Loots JH, Koorts AS, Venter JA. Peribulbar anesthesia. A prospective statistical analysis of the efficacy and predictability of bupivacaine and a lidocaine/bupivacaine mixture. J Cataract Refract Surg 1993;19:72-6.  Back to cited text no. 1
    
2.
Khan ZP, Ferguson CN, Jones RM. Alpha2 and imidazoline receptor agonists: Their pharmacology and therapeutic role. Anaesthesia 1999;54:146-65.  Back to cited text no. 2
    
3.
Wagner DS, Brummett CM. Dexmedetomidine: As safe as safe can be. Semin Anesth Perioper Med Pain 2006;25:77-83.  Back to cited text no. 3
    
4.
Gujral GS, Agarwal M, Gautam P, Shrivastav A, Singh S. Evaluation of the effect and safety of dexmedetomidine as an additive to local anesthesia in peribulbar block for vitreoretinal surgery. Indian JOphthalmol 2019;67:67:641-2.  Back to cited text no. 4
    
5.
Mjahed K, El-Harrar N, Hamdani M, Amraoui M, Benaguida M. Lidocaine-Clonidine retrobulbar block for cataract surgery in the elderly. Reg Anesth 1996;21:569-75.  Back to cited text no. 5
    
6.
Pöpping DM, Elia N, Marret E, Wenk M, Tramèr MR. Clonidine as an adjuvant to local anesthetics for peripheral nerve and plexus blocks: A meta-analysis of randomized trials. Anesthesiology 2009;111:406-15.  Back to cited text no. 6
    
7.
Ahmed SA, Elmawy MG, Magdy AA. Effect of the use of dexmedetomidine as an adjuvant in peribulbar anesthesia in patients presented for vitreoretinal surgeries. Egypt J Anaesth 2018;34:27-32.  Back to cited text no. 7
    
8.
EL-Shmaa NS, El-Kashlan M, Salama ER. The impact of two different doses of dexmedetomidine to local anaesthetic mixture on the quality of single injection peribulbar block in vitreoretinal operations. Int J Clin Anesth Res 2018;2:1-8.  Back to cited text no. 8
    




 

Top
 
 
  Search
 
    Similar in PUBMED
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

 
  In this article
References

 Article Access Statistics
    Viewed265    
    Printed0    
    Emailed0    
    PDF Downloaded49    
    Comments [Add]    

Recommend this journal