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 Table of Contents  
Year : 2023  |  Volume : 2  |  Issue : 1  |  Page : 53-55

Anisocoria under anesthesia: Portentous sign or picayune?

Department of Anaesthesiology and Intensive Care, Maulana Azad Medical College and Associated Hospitals, New Delhi, India

Date of Submission26-Apr-2023
Date of Acceptance06-May-2023
Date of Web Publication25-May-2023

Correspondence Address:
Dr. Sukhyanti Kerai
Room No. 413, BL Taneja Block, Maulana Azad Medical College, New Delhi - 110 002
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jica.jica_9_23

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Anisocoria observed under anaesthesia is an alarming sign for anaesthesiologist and is suggestive of possible of neurological involvement due to raised intracranial pressure, intracranial hemorrhage, or space occupying lesions. We report the occurrence of new onset anisocoria in a patient undergoing video assisted thoracoscopic surgery under anaesthesia. The various etiologies of anisocoria under anaesthesia and their implication have been discussed.

Keywords: Anesthesia, anisocoria, lateral decubitus

How to cite this article:
Kerai S, Goswami S, Gaba P, Bhatt G. Anisocoria under anesthesia: Portentous sign or picayune?. J Ind Coll Anesth 2023;2:53-5

How to cite this URL:
Kerai S, Goswami S, Gaba P, Bhatt G. Anisocoria under anesthesia: Portentous sign or picayune?. J Ind Coll Anesth [serial online] 2023 [cited 2023 Oct 1];2:53-5. Available from: https://www.jicajournal.in//text.asp?2023/2/1/53/377605

  Introduction Top

New-onset anisocoria under anesthesia is one of the ominous signs indicating raised intracranial pressure (ICP) and immediate intervention. Knowledge of various etiologies of anisocoria in the perioperative period is crucial for anesthesiologists for identification and timely therapeutic intervention if indicated. We describe here the occurrence of anisocoria in a patient undergoing video-assisted thoracoscopic surgery under anesthesia and present a review of the literature.

  Case Report Top

A 43-year-old female was scheduled for video-assisted thoracoscopic surgical excision of the right middle lobe pulmonary hydatid cyst. She was a known diabetic and was on tablet metformin. The preoperative assessment revealed good exercise tolerance, unremarkable electrocardiogram, normal kidney function tests, and well-controlled blood sugar levels.

On the day of surgery, standard monitoring, including continuous electrocardiogram, pulse oximeter, and noninvasive blood pressure, was instituted. After securing an intravenous cannula of 18G on the dorsum of the nondominant hand, injection fentanyl 120 μg was administered. General anesthesia was induced with injection propofol 130 mg, and injection vecuronium 6 mg was administered to facilitate the placement of a double-lumen tube (DLT). Intermittent positive pressure ventilation for 3 min with a gaseous mixture of 1.2% isoflurane in oxygen nitrous oxide (50:50) was done, and then, a left-sided DLT of size 35 was inserted. The positioning of DLT was confirmed by auscultation and fiberoptic bronchoscopy. DLT was secured in place using a wet cotton bandage tube tie. Anesthesia was maintained with 1.2% isoflurane in oxygen nitrous oxide (50:50). Injection hydrocortisone 100 mg was administered before the start of surgery. The patient was positioned in the left lateral decubitus, and surgery was started after the collapse of the right-side lung. The excision of the cyst was performed uneventfully in approximately 2 h. After the conclusion of surgery, anesthetic gases were switched off, and neuromuscular blockade was reversed. When eye pads were removed, mydriasis in the left eye with slight conjunctival hyperemia was noted [Figure 1]. The pupillary reflex to light was absent in the left eye. The size of the pupil and light reflex was normal on the right eye. During preoperative assessment, there was no apparent abnormality in the size of the pupils The patient was extubated and was maintaining stable vitals. There was no drowsiness, altered mental status, blurring of vision, headache, or vomiting. Urgent noncontrast computed tomography (NCCT) of the head and ophthalmology opinion were sought for newfound anisocoria in the patient. The NCCT head study was found to be unremarkable. Bedside fundus examination revealed normal optic disc, macula, and posterior vascularization. About 3–4 h after extubation, it was observed that the size of the left pupil started to decrease, and the discrepancy between the sizes of both pupils lessened [Figure 2]. The light reflex was sluggish in the left eye. Ophthalmologist suggested monitoring the patient and following up the next day. After 6 h, both pupils were found to be of the same size with normal pupillary light reflex reaction in both eyes.
Figure 1: Anisocoria in patient observed at the completion of the surgery

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Figure 2: Normal size of the pupils at 6 h after extubation

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  Discussion Top

The appearance of new-onset anisocoria in a patient during the perioperative period is an unusual occurrence and is vexing for anesthesiologists.[1] The differential diagnosis includes preexisting anisocoria, direct trauma to the eyes, accidental exposure of the eyes to alpha-adrenergic or anticholinergic drugs, intracranial space-occupying lesions, intracranial hemorrhage, and impaired venous drainage of the head.[2]

The size of pupils is controlled by the actions of the dilator pupillae muscles innervated by sympathetic nerve fibers and the sphincter pupillae muscles of the iris supplied by parasympathetic fibers. About 20% of healthy individuals have essential anisocoria, which may be noticed suddenly under anesthesia leading to significant concern and unnecessary clinical inputs.[3] Hence, a simple routine pupil examination has been suggested by some of the authors.[4]

Pathological anisocoria results from an imbalance in the activity of the dilator or sphincter pupillae muscles, either due to central or localized events. We found various case reports of new-onset anisocoria during the perioperative period in the literature search. There is a paucity of reports in the literature on portentous anisocoria under anesthesia which required urgent intervention, whereas the majority have reported transient anisocoria. Rapid fluid administration under general anesthesia in a patient with a history of traumatic brain injury has been reported to cause a regional increase in ICP and acute anisocoria.[5] Damodaran et al. described sudden-onset anisocoria and neurological deterioration in a 54-year-old cardiac patient. Computed tomography (CT) angiography in the patient showed type A aortic dissection.[6]

The various causes of transient anisocoria under anesthesia can be broadly divided into four categories: (a) accidental exposure of the eye to pharmacological agents, (b) related to patient positioning, (c) as a complication of certain surgical procedures, (d) accentuation of preexisting anisocoria under anesthesia, and (e) complication of regional anesthesia techniques.

Accidental exposure of the eye to pharmacological agents

The most reported etiology for anisocoria is unintentional exposure of one eye to either sympathomimetic or anticholinergic drugs. The use of topical phenylephrine used for mucosal vasoconstrictor during nasotracheal intubation can reach the conjunctival sacs in retrograde movement through the nasolacrimal ducts causing unilateral mydriasis.[7] In patients receiving nebulized ipratropium bromide, the leakage of the drug from the edge of the face mask to the ipsilateral eye can lead to mydriasis.[8] Contamination of the eye after handling transdermal scopolamine is also reported to cause accidental anisocoria.[9]

Anisocoria as a complication of patient positioning

Xiao et al. reported new-onset anisocoria and mydriasis after the induction of anesthesia and the performance of scalp block in a patient undergoing surgery for a cerebellar tumor. The authors considered that lateral head rotation resulting in impaired venous drainage was a likely reason leading to an increase in ICP and anisocoria.[10] The direct pressure on the globe due to prolonged prone positioning has been reported to cause parasympathetic postganglionic nerve injury leading to segmental pupillary palsy and unilateral mydriasis.[11],[12]

Complications of certain surgical procedures

Postoperative transient unilateral mydriasis is observed after orbital medial wall blowout repair due to direct or indirect parasympathetic nerve injury and excessive retraction of orbital content.[13] It has been reported to occur after functional endoscopic sinus surgery due to the anatomical proximity of the orbit to the paranasal sinus.[14]

Accentuation of preexisting anisocoria under anesthesia

Preexisting Holmes-Adie is another rare but important etiology of anisocoria observed in the perioperative period. It is characterized by a tonic dilated pupil, light-near dissociation, and there may be decreased deep tendon reflexes. There is parasympathetic denervation of the afflicted pupil, which is mostly idiopathic but sometimes associated with viral infections, autoimmune, or cardiovascular diseases.[15]

The presence of anisocoria in patients with preexisting Adie's pupil may be missed during the preoperative assessment as the symptoms are nonspecific and include photophobia and blurry vision. The examination of the affected eye may reveal mydriasis and increased pupillary constriction to accommodation compared to light.[16] The features are exacerbated under anesthesia due to parasympathetic dominance caused by anesthetic agents.[17] The sympathetic block by thoracic epidural has also been speculated to cause parasympathetic dominance leading to the manifestation of Adie's pupil under anesthesia.[18] It has been reported that the incomplete abolition of painful stimulus under anesthesia like tracheal intubation could lead to sympathetic dominance and accentuation of preexisting anisocoria.[19]

Complication of regional anesthesia techniques

Anisocoria during the perioperative period can result from Horner's syndrome. There is an interruption of sympathetic innervation to the eyes, manifesting as miosis on the affected side. It may be noticed as a complication of various regional anesthesia techniques such as epidural, stellate ganglion block, and interscalene block.[20]

In the case described here, there was no evidence of the use of any pharmacological agents which could have led to the unequal size of the pupils. In the preoperative visit, anisocoria was not evident. We believed that mydriasis in the dependent eye in our patient was due to transient parasympathetic postganglionic neuropraxia due to inadvertent ocular pressure during lateral decubitus positioning. The head support used in the case was indigenous one, prepared from cotton and bandages. The use of a silicone gel headrest would have avoided the pressure on the dependent areas during the positioning of the patient.

  Conclusion Top

The new-onset anisocoria under anesthesia is not always ominous, and in the majority of cases, benign etiology has been described. However, as the neurological assessment in a patient under anesthesia is limited and the neurological causes of anisocoria necessitate urgent intervention, anesthesiologists should remain vigilant while encountering such an event.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published, and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Inchingolo F, Tatullo M, Abenavoli FM, Marrelli M, Inchingolo AD, Villabruna B, et al. Severe anisocoria after oral surgery under general anesthesia. Int J Med Sci 2010;7:314-8.  Back to cited text no. 1
Heath Jeffery RC, Young B, Swann PG, Lueck CJ. Unequal pupils: Understanding the eye's aperture. Aust J Gen Pract 2019;48:39-42.  Back to cited text no. 2
George AS, Abraham AP, Nair S, Joseph M. The prevalence of physiological anisocoria and its clinical significance – A neurosurgical perspective. Neurol India 2019;67:1500-3.  Back to cited text no. 3
[PUBMED]  [Full text]  
Turnbull A, Marsh C. Peri-operative anisocoria – The importance of pupil assessment before general anaesthesia. Anaesthesia 2012;67:1053-4.  Back to cited text no. 4
Ghatak T, Singh RK, Baronia AK, Sahu S. Postoperative acute anisocoria and old traumatic brain injury. Indian J Anaesth 2011;55:611-3.  Back to cited text no. 5
[PUBMED]  [Full text]  
Damodaran S, Gourav KP, Kajal S, Kajal K. Sudden onset of coma with anisocoria in a patient with type A aortic dissection: Dilemma in management? Egypt J Cardiothorac Anaesth 2019;13:19-22.  Back to cited text no. 6
Stirt JA, Shuptrine JR, Sternick CS, Korbon GA. Anisocoria after anaesthesia. Can Anaesth Soc J 1985;32:422-4.  Back to cited text no. 7
Das Adhikari S, Chakraborty R, Kerai SI, Shoaib Budoo M. An elementary cause of anisocoria in intensive care unit. Indian J Crit Care Med 2019;23:346.  Back to cited text no. 8
Joo JH. Anisocoria after scopolamine transdermal patch contamination: A case report. Medicine (Baltimore) 2021;100:e27887.  Back to cited text no. 9
Xiao C, Chen F, Tan Y, Bao X, Jing S. Anisocoria and mydriasis after scalp nerve block: A case report. J Int Med Res 2022;50:3000605221099262.  Back to cited text no. 10
Gupta P, Adabala VB, Barik AK. Unilateral mydriasis: A complication of spine surgery in prone position. Braz J Anesthesiol 2019;69:319-21.  Back to cited text no. 11
Papaioannou I, Xristopoulos K, Baikousis A, Korovessis P, Kokkinis K. Anisocoria after posterior spine surgery: A rare but disastrous complication – A case report and literature review. J Orthop Case Rep 2019;9:92-5.  Back to cited text no. 12
Kang MS, Ahn JH. Characteristics of postoperative anisocoria after medial orbital wall fracture repair. J Craniofac Surg 2022;33:e21-3.  Back to cited text no. 13
Stewart D, Simpson GT, Nader ND. Postoperative anisocoria in a patient undergoing endoscopic sinus surgery. Reg Anesth Pain Med 1999;24:467-9.  Back to cited text no. 14
Xu SY, Song MM, Li L, Li CX. Adie's pupil: A diagnostic challenge for the physician. Med Sci Monit 2022;28:e934657.  Back to cited text no. 15
Hope-Ross M, Buchanan TA, Archer DB, Allen JA. Autonomic function in Holmes Adie syndrome. Eye (Lond) 1990;4 (Pt 4):607-12.  Back to cited text no. 16
Ishihara M, Aoi R, Takahashi K. Anisocoria after anesthesia induction caused by Adie syndrome. J Anesth 2015;29:315.  Back to cited text no. 17
Kobayashi M, Takenami T, Kimotsuki H, Mukuno K, Hoka S. Adie syndrome associated with general anesthesia. Can J Anaesth 2008;55:130-1.  Back to cited text no. 18
Aceto P, Perilli V, Vitale E, Sollazzi L. Effect of anesthesia in a patient with pre-existing anisocoria. Eur Rev Med Pharmacol Sci 2011;15:211-3.  Back to cited text no. 19
Atkinson D, McCluskey A, Richardson AM. Horner's syndrome after general anaesthesia. Anaesthesia 2005;60:99-100.  Back to cited text no. 20


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