The Impact of Re-Operation, Relatives and Race on the Oculocardiac Reflex During Strabismus Surgery

Abstract

Purpose: The oculocardiac reflex (OCR) is a trigeminovagal bradycardia elicited by tension on an extraocular muscle (EOM). Using three decades of observational data, we investigated whether or not individual strabismus patients are prone to oculocardiac reflex.

Patients and methods: All patients undergoing strabismus surgery from 1992 to 2019 had deliberate 10-second, 200-gram square-wave tension on extraocular rectus muscles with anesthetic variables recorded. OCR was defined as the maximally tension-altered heart rate as a percent of stable baseline heart rate.

Results: OCR was compared in 2532 original cases with 323 re-operations. The 169 cases that used anticholinergics (99% OCR) were excluded from the analysis. The median OCR, a 15% drop, was found to be 85% (95% CI 39%, 102%,; range 5-151%). Factors that showed a significant effect on the OCR were the type of EOM with lateral rectus least (Kruskal-Wallis X2(3)=8, p<0.05), and adults had less OCR compared to the children (X2(2)=105, p<0.01). Factors that showed an augmenting effect on the OCR were peri-operative opioids (X2(6)=62, p<0.01) and Caucasian race (X2(4)=12, p<0.02). Gender and iris color were not found to have an impact on OCR. Re-operations and first-degree relatives did not differ from age-matched controls, but EOM- and opioid-adjusted re-operations correlated with their initial cases (r=0.37).

Conclusion: We confirmed the previously published blocking effect of atropine, augmenting impact of opioids, and an inverse relationship of age on OCR. There was a weak proclivity for individuals to be prone to OCR. We found an impact of race with Caucasians having more OCR.

Keywords: bradycardia; opioid; race; re-operation; strabismus surgery; trigemino-vagal reflex.

Conflict of interest statement

Financial Disclosure: Robert W Arnold is the president of Glacier Medical Software that developed ROP-Check cloud-based software and also PDI Check that makes a vision screening game for the Nintendo 3DS. He coordinates the Alaska Blind Child Discovery which has received discounted vision screening technology from several vendors. He is an investigator and protocol developer for the NIH-funded Pediatric Eye Disease Investigator Group. No other co-author has financial conflicts. The authors report no other conflicts of interest for this work.

© 2020 Arnold et al.

Figures

Figure 1

Frequency distribution of oculocardiac reflex, in 2532 original cases without anticholinergic. OCR was elicited by 10-second, 200-gram square-wave tension on extraocular rectus muscle.

Figure 2

Box and whisker plots of oculocardiac reflex medians as a percent of baseline heart rate. The box surrounds the middle quartiles with whiskers extending to the minimum and maximum. To the left represents all initial cases without anticholinergic medication while the remaining are groupings associated with age groupings, re-operations, race and ethnicity, iris color and which extraocular muscle was involved.

Figure 3

The impact of age on the oculocardiac reflex (OCR). OCR is defined as the percent of baseline heart rate with each of these 2532 cases an original case without anticholinergic medication.

Figure 4

Correlation between 323 initial and re-operation for oculocardiac reflex adjusted for opioids and type of rectus muscle.

Figure 5

Profound OCR and re-operation. Cases at given ages with an OCR less than 50% of baseline heart rate who also had profound OCR on re-operation. Five of these nine cases had neurologic impairment.