Background: The stimulation of the trigeminal nerve around the orbit and tension on an extraocular muscle tendon during a strabismus surgery elicits an Oculocardiac Reflex (OCR). This reflex results in severe bradycardia. Profound OCR can lead to hypotension. An evidence-based review to make strabismus surgery was conducted to assess the safety and efficiency that will be beneficial for the surgeons, anesthesiologists and especially for the patients.
Methods: Trigeminovagal and oculocardiac world literature was analysed and reviewed. It covered 15000 patients, including 51 randomised trials. Anaesthetic, patient and surgical influences on routine strabismus were compared at an ongoing observational trial in Alaska. The Institutional Review Board of Providence Hospital approved an observational protocol under which prospective documentation of strabismus cases was done from 1992 to 2020. The use of opioids, the amount and type of EOM, age and anticholinergics were defined as the critical variables. Moderate hypotension that accompanied prolonged bradycardia in orbital fracture patients was resolved after fracture repair.
Results: Rapid-acting opioids and dexmedetomidine increased OCR. OCR was observed to reduce in the right eye, older patients, hypocarbia, less EOM tension, anticholinergics, orbital block and deeper inhaled anaesthetics. For subsequent OCR in re-operations rapid-acting opioids and dexmedetomidine were noted to be poor predictors.
Conclusion: In the absence of anticholinergic preventive measures, profound bradycardia can occur in about 10% of strabismus surgery cases, the authors observed. Reliable prediction of PCR cannot be yet done and remains elusive. Careful anaesthetic monitoring before EOM manipulation makes OCR rare. However, the exact explanation for the occasional occurrence of a dramatic cardiac response is still not known.