My Canadian Pharmacy: Deliberations about Impact of Palivizumab on Admission to the ICU for Respiratory Syncytial Virus Bronchiolitis

sRSV diseaseIn the present national surveillance survey, we compared PICU admissions and the need for mechanical ventilation for the treatment of RSV bronchiolitis between the following two consecutive seasons: before and after the introduction of palivizumab in Israel. Seventeen percent of the patients admitted to a PICU in both periods were candidates for RSV prophylaxis according to the AAP guidelines. For period 1, 13.3%; and for period 2, 9.7% (p < 0.01) were candidates for RSV prophylaxis according to the IMH recommendations. The difference in the rates associated with the AAP and the IMH guidelines is probably attributable to the broader criteria of the AAP guidelines.

The present study takes an alternative look at the epidemiology of severe RSV disease. It did not ask which patients were at greater risk of severe disease, but rather, among those with severe disease what risk factors were present. We sought to investigate the potential impact of palivizumab therapy on the burden of PICU admissions due to RSV infections. We evaluated the PICU admissions for RSV bronchiolitis with respect to the recognized risk factors associated with an increased severity of RSV disease, namely, prematurity and CLD. The study showed that the majority of children who were admitted to the PICU lacked these risk factors, probably because the majority of infants in the general population are not premature and do not have CLD.

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Outcomes of Impact of Palivizumab on Admission to the ICU for Respiratory Syncytial Virus Bronchiolitis

bronchodilatorsOne hundred twenty-nine children were admitted to the 13 PICUs in Israel because of acute bronchiolitis during period 1 (from 2000 to 2001), and 167 children were admitted during period 2 (from 2001 to 2002). Of these patients, 105 children (81.4%) and 123 children (73.7%), respectively, were RSV-posi-tive. The remainder were RSV-negative, including two patients in period 1 and one patient in period 2 with unknown RSV status. There was no statistically significant difference between the periods for this factor (p = 0.127). An analysis of the seasonal distribution of PICU admissions for RSV bronchiolitis revealed that in both periods 75 to 85% of the RSV-positive patients were admitted to PICUs from December to February, and 100% were admitted from November to April. All of the patients with proven RSV-negative status were admitted to PICUs from November to March (approximately 10 cases per month). The data for period 2 are shown in Figure 1. Because our study focused on palivizumab prophylaxis (a specific monoclonal antibody against RSV), the non-RSV- positive patients (ie, those with RSV-negative and unknown status) were excluded from the analysis.

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Investigation about Impact of Palivizumab on Admission to the ICU for Respiratory Syncytial Virus Bronchiolitis

RSV bronchiolitisThis 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.

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My Canadian Pharmacy: Impact of Palivizumab on Admission to the ICU for Respiratory Syncytial Virus Bronchiolitis

Respiratory syncytial virusAlmost all children become infected with respiratory syncytial virus (RSV) within 2 years after birth. Although the infection usually presents as a mild upper respiratory tract disease, up to 1% of infected children require hospitalization. Overall, RSV accounts for 50 to 90% of all hospitalizations for bronchiolitis in children.2 In patients with a known underlying disease, such as chronic lung disease (CLD) or congenital heart disease, and in premature children, RSV bronchiolitis can quickly become a severe, life-threatening, lower respiratory tract infection.

Since 1996, the following two passive immunization techniques have been available: RSV IV immunoglobulins (Ig) (RSV-IGIV, RespiGam; Massachusetts Public Health Biological Laboratories; Boston, MA; and MedImmune, Inc; Gaithersburg, MD) and a humanized monoclonal antibody preparation against the F glycoprotein of RSV (palivizumab, Synagis; MedImmune, Inc). In controlled clinical trials, monthly prophylaxis during the RSV season reduced the hospitalization rate in the high-risk population. On the basis of these findings, in 1998 the American Academy of Pediatrics (AAP) recommended that RSV prophylaxis should be considered for the following patients:
1. Infants < 2 years old with CLD who warranted medical therapy (ie, supplemental oxygen, bronchodilators, diuretics, or corticosteroids) within 6 months before the anticipated RSV season;
2. Infants born at < 28 weeks of gestation who do not meet the first criterion, up to 12 months of age; and
3. Infants born at 29 to 32 weeks of gestation who do not meet the first criterion, up to 6 months of age.

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