Successful Outcome of Cataract Surgery using Topical Anaesthesia in a Patient with Previous Local Anaesthetic Failures due to Scorpion Sting

Vol 10 | Issue 2 | May-August 2024 | Page: 04-06 | Nikunj V. Patel, Shreya B. Shah, Umang Mathur

DOI: https://doi.org/10.13107/jaccr.2024.v10.i02.237

Submitted: 15/07/2024; Reviewed: 11/03/2024; Accepted: 24/06/2024; Published: 10/08/2024


Author: Nikunj V. Patel [1], Shreya B. Shah [2], Umang Mathur [1]

[1] Department of Cornea, Dr. Shroff ’s Charity Eye Hospital, New Delhi-110002
[2] Department of Anaesthesiology, All India Institute of Medical Sciences, New Delhi-110029

Address of Correspondence

Dr. Shreya Shah,
Department of Anaesthesiology, All India Institute of Medical Sciences, Sri Aurobindo Marg, Ansari Nagar, New Delhi-110029
E-mail: shreyabs@hotmail.com


Abstract


Introduction: “Failure” of anaesthesia is a commonly encountered situation and the exact cause may not be known. Previous history of scorpion stings is one of the causes and is often not thought about.
Case Presentation: A 71-year-old gentleman presented with a history of scorpion stings in childhood and two previous instances of “failed” anaesthesia. He felt pain when he was operated on for hydrocoele 30 years back and again when underwent left eye cataract surgery under local anaesthesia 3 years ago. We successfully operated on him for his right eye cataract under topical gel anaesthesia without him feeling significant pain.
Conclusion: Extracting the history of scorpion stings in a patient having failures of anaesthesia in the past can help in planning future surgeries. Cataract surgeries in such patients should be performed under topical gel anaesthesia.
Keywords: Scorpion sting, Anaesthesia failure, Cataract surgery, Topical anaesthesia, Corneal nerves.


Introduction

During ocular surgeries, adequate anaesthesia is essential to comfort both the patient and the operating surgeon. For most surgeries, a combination of lidocaine and bupivacaine is commonly used, as the short-acting lidocaine provides immediate anaesthesia while bupivacaine provides a longer duration of anaesthesia. Poor intraoperative akinesia and insufficient analgesia can increase vitreous pressure, leading to complications. Inadequate anaesthesia is usually attributed to a technical error in performing a regional block. However, in some circumstances, patient factors could be contributory and extracting an “out of the box” history could aid in better patient management. We report a case of a patient post-scorpion sting, where the failure of local anaesthesia was expected. However, general anaesthesia was avoided in this high-risk cardiac patient and he was successfully operated on for cataracts under topical anaesthesia.

Case Report:

A 71-year-old man presented with a diminution of vision in his right eye for the past 1 year. He had a case of dilated cardiomyopathy with poor effort tolerance and a left ventricular ejection fraction of 25%. On examination, visual acuity in the right eye was 20/200. He was advised of cataract surgery for the right eye.
The patient was apprehensive regarding the surgery as he had experienced significant discomfort during the phacoemulsification of the left eye under the peribulbar block. The surgical duration was 30 min. 5 min into the surgery, he started having pain, which lasted for the duration of the surgery. The post-operative period was uneventful. He also recollected a similar experience of inadequate anaesthesia 30 years ago when he was operated on for hydrocoele under spinal anaesthesia. His daughter, an anaesthesiologist, gave us the history that the patient had a scorpion sting in childhood over his thumb producing a localized reaction. Hence, we suspected the sting to be the likely cause of previous “failures” of anaesthesia.
A pre-operative applanation tonometry after the instillation of proparacaine drops caused no pain. We confirmed the absence of corneal sensations after 15 min of instillation. Based on this observation, there was a probability that despite the previous failures of local anaesthetics (LA), topical anaesthesia could still be successful. The patient was counseled for right eye phacoemulsification under topical anaesthesia and written informed consent was obtained. Consent was also obtained from the patient for the publication.
For surgical anaesthesia, lignocaine hydrochloride (2%) jelly (Lox 2% jelly, Neon Laboratories Ltd, India) was instilled twice -10 min before surgery and after applying the drape. Monitored anaesthesia care with intravenous sedation was kept ready. The patient was enquired about pain in touching his cornea and conjunctiva with forceps. After assuring sufficient analgesia, surgery was commenced. The patient did not complain of pain throughout the duration of surgery and the post-operative course was uneventful.

Discussion:

Inadequate effect of local anaesthesia can be in terms of extent, quality and/or duration of LA action [1]. Resistance to LA can be found in patients with a history of scorpion stings. We could only find a few case reports and two studies describing the development of local anaesthesia resistance after a scorpion sting [2, 3, 4]. Only one case report described the failure of LA in cataract surgery and one in dental surgery, the rest were with regards to spinal anaesthesia.
It is suggested that in patients with a history of scorpion stings, LA use for any type of block should be avoided, and surgery should preferably be performed under general anaesthesia. However, general anaesthesia would pose a high risk for our patient and there was a possibility that the peribulbar block would not work again.
Scorpions are predominantly seen in the rural areas of India. The clinical effects following the sting vary from species to species. The venom contains several low molecular weight basic proteins, neurotoxins, cardiotoxins, nephrotoxin, hemolytic toxins, phosphodiesterase, phospholipase A, and hyaluronidase. Scorpion neurotoxins act on voltage-gated ion channels of the nervous system. Those acting on voltage-gated sodium channels (Nav) are alpha and beta toxins [5].
The exact mechanism by which the topical lidocaine gel worked in our patient is not clear. However, two mechanisms can be proposed.
1. Antibody-mediated response is one of the proposed mechanisms for resistance to LA following a scorpion sting [6]. The LA attaches to the inner pore of the Na channels, more precisely, the sixth segment of domain four of the alpha subunit (IV-S6). In the peribulbar block, the LA is injected into the peribulbar extraconal space, which eventually spreads into the intraconal space where all the nerves reside. This area is highly vascular leading to an increased antibody response. In the topical drops/gel, the LA is deposited over the corneal surface. Cornea being avascular, may prevent delivery of cross-reacting antibodies at the nerve terminals causing less/no resistance to the action of LA.
2. Corneal sensations are carried by corneal nerve endings to the trigeminal ganglion. LA acts on the Nav which are present along the length of the axon, at a distance from the nerve terminal. Sodium channel subtypes Nav 1.8 and 1.9 subtypes are abundantly present in the corneal axons. The subtype Nav1.8 is found to be more sensitive to lidocaine than other subtypes [7, 8]. However, the nerve endings/receptors are devoid of Nav, and another ancillary mechanism of action of topical anaesthesia must be present (Fig. 1) [9, 10].
These nerve terminals have the cationic channels TRPV1, TRPM8, and Peizo2 [9]. Instillation of topical anaesthetic drops predominantly acts on these cationic channels, allowing the surgeon to make full-thickness corneal incisions near the limbus, transecting the thick limbal nerves without eliciting pain. The deeper stromal nerves are more trophic than sensory while the superficial nerves mainly respond to external stimuli [11].


We decided to use topical lidocaine jelly as the gel formulation provides better analgesia; [12] better wetting properties; [13] deeper anaesthesia, the effect lasting up to 45 min; [14, 15] Intracameral concentration of lidocaine has little influence on pain control in cataract surgery [12, 16]. Thus, a key factor for pain control is corneal bioavailability which is increased using gel formulation.
Although the duration of the present surgery was shorter than previous surgeries, we were prepared to provide analgesia through the surgery, in case of any complication that would have increased the surgical duration. The majority of cataract surgeries are otherwise performed under topical anaesthesia. This report is relevant for planning surgeries that would have been planned under the peribulbar block with anticipated anaesthesia failure.

Conclusion:

Scorpions are rampant in many parts of the world and scorpion stings may not always be reported as it is considered trivial. Eliciting a history of scorpion sting routinely is not necessary but has significance in patients from endemic regions with previous anaesthesia “failures.” It is advisable to schedule such cases for phacoemulsification under topical gel anaesthesia with monitored anesthesia care. It will help avoid general anaesthesia in higher American Society of Anesthesiologists physical status patients. Other ocular surgeries (intra or extra) requiring a longer duration of anesthesia should be performed under general anaesthesia.


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How to Cite this Article: Patel NV, Shah SB, Mathur U Successful Outcome of Cataract | Surgery Using Topical Anaesthesia in a Patient with Previous Local Anaesthetic Failures due to Scorpion Sting | Journal of Anaesthesia and Critical Care Case Reports | May-August 2024; 10(2): 04-06. https://doi.org/10.13107/jaccr.2024.v10.i02.237

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