Changes in Vital Signs and Pupil Diameter Related to Pharmacologic Mydriasis in Premature Infants: A Randomized Double Blind Clinical Study

I. Introduction Retinopathy of prematurity (ROP) is one of the common anatomic causes of blindness among Filipinos, accounting for 47.7% of the cases. With this retinopathy being preventable and treatable, ROP screening has been proven to be effective in preventing blindness, which is achieved with the usage of mydriatics. Even if the regimen of multiple alternate instillations of 0.5% tropicamide and 2.5% phenylephrine is the one recommended by international guidelines for ROP screening, the mydriatic regimen usually used by many of the country's institutions is the regimen of 0.5% tropicamide + 0.5% phenylephrine applied via a cotton wick placed in the inferior fornix. There have been no studies yet on the safety and efficacy in premature infants of this mydriatic preparation and method, although it is hypothesized that the usage of a cotton wick promotes the possible systemic effects of the mydriatic combination used.

II. Significance It is the aim of this study to evaluate the safety and efficacy of the mydriatic regimens we use in our institution and compare it to the recommendation by the UK ROP Guidelines. In doing so, this study aims to (1) document vital sign changes in the infant during dilation, (2) identify adverse systemic changes due to the mydriatic regimen and (3) provide appropriate interventions and recommendations to address these adverse effects. These will greatly improve the ROP screening process in our institution.

III. Objectives The general objective is to determine vital sign changes related to Pupil Dilation among preterm infants referred for ROP Screening from Neonatal Intensive Care Unit, Pediatric Wards and Eye Instrumentation Center of the Philippine General Hospital (PGH). Specifically, its objective is to compare the vital sign changes and mydriasis in (1) multiple alternate instillations of 0.5% Cyclopentolate Hydrochloride + 2.5% Phenylephrine (MAI) (2) single instillation of 0.5%/0.5% Phenylephrine + Tropicamide (SI) and (3) single instillation of 0.5%/0.5% Phenylephrine + Tropicamide with a cotton wick placed in the inferior fornix (SIW).

IV. Methodology This study was designed as a randomized, double blind, clinical study which enrolled sixty preterm infants referred for ROP Screening from January to July 2011. Each subject was randomly distributed into the standard, instillation, and packing group. To avoid observer bias, two investigators were involved per monitoring during dilation. The first investigator was assigned only to place the monitoring devices and to administer the mydriatics contained in unmarked 1 mL syringe which content was unknown to him.

The vital signs monitored during dilation were blood pressures (systolic, diastolic and mean arterial pressure (MAP)), heart rates and oxygen saturations using the newly calibrated Phillips Digital IntelliVue MP20 junior Cardiac monitors. A digital camera and a millimeter rule were used to approximate size of pupil dilatation. Measurement of all the vital signs and pupil dilation from a subject was derived from a single dilation session only.