BackgroundThe oculocardiac reflex (OCR), bradycardia that occurs during strabismus surgery is a type of trigemino-cardiac reflex (TCR) is blocked by anticholinergics and enhanced by opioids and dexmedetomidine. Two recent studies suggest that deeper inhalational anesthesia monitored by BIS protects against OCR; we wondered if our data correlated similarly.MethodsIn an ongoing, prospective study of OCR/TCR elicited by 10-s, 200 g square-wave traction on extraocular muscles (EOM) from 2009 to 2013, anesthetic depth was estimated in cohorts using either BIS or Narcotrend monitors. The depth of anesthesia was deliberately varied between first and second EOM tested.ResultsFrom 1992 through 2013, 2833 cases of OCR during strabismus surgery were monitored. Excluding re-operations and cases with anticholinergic, OCR from first EOM traction averaged − 20.2 ± 21.8% (S.D.) with a range from − 95 to + 25% in patients aged 0.2 to 90 (median 6.5) years. We did not find correlation between %OCR and brain wave for 97 patients with BIS monitoring and 91 with Narcotrend. With intra-patient controls between first and second muscle, the difference in brain wave did not correlate with difference in %OCR for BIS (r = 0.0002, 95% C. I -0.0002, 0.002, p = 0.30) or for Narcotrend (r = − 0.001, 95% C. I -0.004, 0.001, p = 0.32). Secondary multi-variable analysis demonstrated significant association on %OCR particularly with BIS monitor, opioid, propofol and nitrous oxide concentration in the second EOM tensioned. Sevoflurane concentration correlated better with BIS monitor in second and third EOM tension. %OCR correlated with younger age (p < 0.01). OCR with rapid onset was more profound than those with gradual onset (difference in means 18, 95% C. I 10, 26%).ConclusionsWe were unable to confirm a direct correlation between brain wave monitor and OCR when using multifactorial anesthetic agents. The discrepency with other studies probably reflects direct impact of inhalational agent concentration and less deliberate quantification of EOM tension. We found no level of BIS or Entropy EEG monitoring that uniformly prevents OCR.Trial registryNCT03663413.Data: http://www.abcd-vision.org/OCR/OCR%20Brainwave%20de-identified.pdf.

is an alpha-adrenergic agonist that can serve as an intranasal alternative to oral midazolam for children undergoing strabismus surgery. Helpful for pediatric eye surgery, 1 when combined with fentanyl and ketamine, intravenous dexmedetomidine may decrease oculocardiac reflex. 2 From 2013 to 2015, in our institutional review board-approved study, we sought to determine the influence of these agents on prospectively studied oculocardiac reflex: a widely variable bradycardia elicited by 200 g and 10-second square wave tension on the inferior rectus muscle. Since 1992, our 2,283 primary cases without anticholinergic with a mean age of 15 ± 19 years had an oculocardiac reflex averaging-20.2% ± 0.4% (standard error of the mean) bradycardia. Compared to no preoperative sedation in patients younger than 10 years (n = 102, median:-19.5%), dexmedetomidine (2 mcg/kg nasal) produced more oculocardiac reflex (n = 23, median:-33.6%, mean heart rate from 100 to 63 bpm, Mann-Whitney test, P < .01), whereas midazolam (0.5 mg/kg orally) was not significantly different (n = 11, median:-28.9%, mean heart rate from 122 to 85 bpm, Mann-Whitney test, P = .18; Figure 1). In patients younger than 20 years who did not receive dexmedetomidine, oculocardiac reflex with fentanyl at induction (-26.6% ± 7%) was greater than in those who did not receive fentanyl (-18.6% ± 4%, t test, P = .03). Nasal dexmedetomidine as a sedative before strabsimus surgery in young patients produced more oculocardiac reflex than in patients receiving oral midazolam or those with no preoperative sedative. We also observed more oculocardiac reflex with the other agent known to produce an augmentation of oculocardiac reflex, fentanyl. 3 Surgeons, anesthesiologists, and those examining infants for retinopathy of prematurity should be aware that dexmedetomidine and fast-acting opioids can produce more oculocardiac reflex. Further study is now under way to better delineate the impact of dexmedetomidine on the oculocardiac reflex in children and adults.

BackgroundStrabismus surgery is often performed on children and adults as a quick-turnover, outpatient procedure under general anesthesia. Ideal methods to reduce post-operative pain and nausea are not yet perfected. We postulated that a simple topical anesthetic drop after surgery might help.MethodsIn a prospective study of oculocardiac reflex (OCR) and strabismus surgery, a cohort of ongoing patients either received proparacaine immediately post-op, or none. Co-variables were Intraoperative opioid and OCR, patient age, type of surgery. Several post-operative recovery outcome variables were prospectively monitored.ResultsSixty strabismus surgery patients (age 15±22 years) received proparacaine 1% while another 80 (16.5±22 years) received none; both received topical antibiotic-steroid ointment. Pain and nausea (Likert scale) were not impacted by covariables complexity of case, age less than 3.5, OCR >33% drop, intraoperative opioid or neuro-status. Immediate post-op heart rate was lower if OCR >33% and if opioids used. Time until discharge was shorter in younger patients. Proparacaine did not impact outcome variables, except in patients younger than 3.5 years when post-op pain was worse.ConclusionPost-op topical anesthetic either produced no difference, or worsened post-op pain and recovery. This prospective study does not support the use of topical anesthetic drop to reduce post-strabismus pain and nausea.Clinical trials registrationNCT03672435, Strabismus Recovery With Proparacaine and Oculocardiac Reflex (OCRprop).

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