Objective: To determine the incidence and risk factors of postoperative apnea in premature infants who received general anesthesia for cryotherapy or laser photocoagulation for treatment of retinopathy of prematurity (ROP) at Queen Sirikit National Institute of Child Health.
Material and Method: A retrospective cohort study was performed by reviewing medical records of premature infants with ROP who underwent general anesthesia for cryotherapy or laser photocoagulation during January 2008 and December 2010 at Queen Sirikit National Institute of Child Health. The incidence and risk factors of postoperative apnea were analyzed.
Results: Forty of 167 (24%) premature infants had apnea after general anesthesia for treatment of ROP. The risk factors were post-conceptual age and history of apnea. The risk of apnea in patients with post-conceptual age less than 35 weeks was 5.7 times higher than in patients with post-conceptual age more than 37 weeks (95%CI 1.59-20.45). Patients with a prior history of apnea had a 6.42 times greater risk of postoperative apnea compared to patients without a prior history of apnea (95%CI 2.01-20.50). No other serious complications were reported during the study period.
Conclusion: The incidence of apnea after general anesthesia in infants with ROP treated with cryotherapy or laser photocoagulation was 24%. The risk factors of postoperative apnea were post-conceptual age less than 35 weeks and prior history of apnea. Patients with risk factors should be closely monitored.

Keywords: Anesthesia, Apnea, Cryotherapy, Laser photocoagulation, Premature infants, Retinopathy of prematurity