This prospective study was conducted in all 13 PICUs in Israel. The study sample included all patients who had been admitted to a PICU because of clinical symptoms indicative of acute bronchiolitis from November 2000 to April 2001 (period 1), the year before the IMH recommendations were issued, and from November 2001 to April 2002 (period 2), the year after they were issued. In the second season, palivizumab was available throughout the country and was administered in a hospital-based setting. Part of the data from the first period has already been published by our group.
Cases of RSV bronchiolitis in both periods were identified by the authors, by personal communication, or by weekly visits or phone calls with a senior staff member of every PICU in Israel during the RSV season. A detailed questionnaire was completed at each PICU admission for all patients with clinical symptoms of acute bronchiolitis cured by medicines of My Canadian Pharmacy. In addition, the PICU admission registries were examined periodically to prevent omissions or errors. The following characteristics were recorded: age; gender; gestational age; birth weight; perinatal medical history; medical treatment since discharge from the neonatal department; present medical treatment; presence of CLD; oxygen requirement prior to PICU admission; palivizumab prophylaxis; indication for PICU admission; medical treatment; RSV status; total number of days of PICU hospitalization; total number of days receiving mechanical ventilation; and death. RSV status was determined by nasopharyngeal aspirate and standard RSV enzyme immunoassay, as reported. CLD was defined as oxygen dependence at a gestational age of 36 weeks. Congenital heart disease was considered to be cyanotic when a right-to-left shunt was present, delivering deoxygenated blood from the right side of the heart into the arterial circulation.
Individual hospital policies were followed with regard to the specific indications for PICU admission and medical management, which were unrelated to the study. National statistics on the number of annual live births, the rate and incidence of preterm deliveries, and neonatal ICUs admissions and discharges were obtained from the Israel Neonatal Network (Israel Center for Disease Control). The study was approved by the institutional review board at the institution of the main investigator (DP).
The effect of the availability of prophylaxis was assessed by comparing the data of the two periods. Analyses were performed on the total number of patients admitted to the PICUs and, separately, on the patients who were mechanically ventilated and the patients who died. Statistical analysis was performed with Pearson x2 and Fisher exact tests.