Topical Anesthesia and Intra-arterial Chemotherapy for Retinoblastoma

Hemodynamic Instability

The objective of this study is to use local topical anesthesia to numb the sensory input, captured by branches of the Trigeminal nerve found on the skin in and around the eye, to decrease a hemodynamic reflex seen during placement of a catheter for intra-arterial chemotherapy (IAC) for eye tumors in children. This Trigeminal-cardiac reflex brings about hemodynamic instability during general anesthesia. Normally, one could block this sensorial input with ophthalmic peribulbar placement of local anesthetics, but these eyes have malignant growth and invasive procedures may cause more harm. The investigators are aiming to numb the sensory branches of the trigeminal nerve non-invasively and observe for any decrease in these events.

Retinoblastoma is a rare tumor of the eye and accounts for 6% of malignancies in children less than 5 years of age. Pediatric anesthesiologists have observed a series of hemodynamic instability following the insertion of a catheter into the cavernous segment of the internal carotid artery or during manipulation of a micro-catheter into the ophthalmic artery for intra-arterial chemotherapy (IAC) of retinoblastoma cases by neuroradiologists. This reaction has been recently published in case reports and observational studies as the treatment of these tumors have moved into the interventional imaging suites. This reaction closely resembles the diving reflex seen when a person is submerged in cold water; known as the trigeminal-cardiac reflex. It manifests as a sudden hemodynamic disturbance in arterial blood pressure, heart rate, arrhythmia and changes in pulmonary compliance.Rescue from a trigeminal-cardiac reflex entails increasing intravascular volume, administrating mild to resuscitative doses of epinephrine and ventilatory support. Catheter manipulation around the ophthalmic artery can stimulate the afferent pathway of the trigeminal nerve, branches V1 and V2, originating around the eye to be treated.The ethmoidal nerve, from the nasal passage on the same side, is also stimulated. This in turn triggers a response by the vagus nerve with hemodynamic instability. Method: Participants are placed under general endotracheal anesthesia for this scheduled procedure. One drop of ocular antiseptic (betadine 5%) will be placed in the eye to be treated followed by a drop of topical FDA approved local anesthetic, Tetracaine 0.5%, to the nasolacrimal duct ( inner corner of the eye) on the eye to be treated. This will numb the ethmoidal nerve in the nasal passage. This is followed by 1 ml of 3.5% Lidocaine gel to the surface of the eye. This gel is placed on the surface of the eye and skin around the eye to numb V1 and V2 fibers of the trigeminal nerve. The study will observe if there is any decrease in the intensity of the reflex or incidence of the reflex during placement of the micro-catheter.

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