The pain response to mydrin-P eye drops in premature neonates

Background: To evaluate the pain responses of premature neonates after the instillation of mydriatic eye drops (Mydrin-P; 0.5% tropicamide and 0.5% phenylephrine hydrochloride) for retinal examination. Methods: Fifty premature infants (100 eyes) of birth weight (≤ 1501 g) or gestational age (≤ 32 w) who underwent Retinopathy of Prematurity (ROP) examinations between December 2014 and June 2015 in Neonatal Intensive Care Unit (NICU) of Guangdong Women and Children Hospital were randomly selected. All infants received 3 drops of Mydrin-p eye drops for each eye every 5 min. Pain assessments were immediately carried out using the Premature Infant Pain Profile (PIPP): 0-drop; 30 s after 1-, 2- and 3-drop administration. And pupil size was measured by two masked doctors at 0 (baseline), 20, 30 and 40 min after eye drops instillation. Results: 1. The mean PIPP score of the first instillation was (7.41 ± 0.53), significantly higher than (7.41 ± 0.53) of the baseline PIPP (P<0.001). The mean PIPP score of the second instillation was (12.33 ± 0.86), considerably higher than (7.41 ± 0.53) of the first instillation (P<0.001); 2. The pupil size at 30 min was (7.59 ± 0.76 mm), significantly larger compared with (6.02 ± 0.86 mm) at 20 min and (6.25 ± 1.07 mm) at 40 min (both P<0.001). Conclusion: The instillation of Mydrin-P eye drops before ROP screening may cause pain response in premature infants. The use of 0.5% tropicamide and 0.5% phenylephrine eye drops with 3 drops every 5 min can exert the most significant effect upon mydriasis at 30 min after eye drops administration