Assessment of the Pediatric Index of Mortality 2 with the Pao2/Fio2 ratio derived from the Spo2/Fio2 ratio: a prospective pilot study in a French pediatric intensive care unit.

ABSTRACT

OBJECTIVE: The Pediatric Index of Mortality 2 is a mortality prediction tool used in pediatric intensive care units. Arterial blood gas sampling that is required to calculate the Pao2/Fio2 ratio is often unavailable. Several authors have proposed mathematical relations between the Pao2/Fio2 and Spo2/Fio2 ratios. The main objective of this study was to assess the validity of the Pediatric Index of Mortality 2 score and three modified Pediatric Index of Mortality 2 scores with the Pao2/Fio2 ratio calculated from the Spo2/Fio2 ratio. DESIGN: Prospective observational study of consecutive patients admitted during a 23-month period. SETTING: A multidisciplinary French pediatric intensive care unit. PATIENTS One thousand forty-three patients, 80 of whom died (7.7%). INTERVENTIONS: None. MEASUREMENTS AND MAINS RESULTS: Only 15 of 1043 patients had a Pao2 measurement. Spo2/Fio2 ratio was determined for 338 patients (33%) for whom Fio2 was known and Spo2 was ≤ 97%. However, for mathematical reasons, Pao2/FIo2 ratio could be calculated from the three Spo2/Fio2 equations for 328 (31%), 295 (28%), and 100 (10%) patients, respectively. Discrimination assessed by the area under the receiver operating characteristic curve was 0.86 for Pediatric Index of Mortality 2 and the modified scores. Calibration assessed by the Hosmer-Lemeshow goodness-of-fit test was poor for Pediatric Index of Mortality 2 (p = .04) and one modified score (p = .03) and good for two other modified scores (p = .06, p = .09). CONCLUSION: This study suggests that the Spo2/Fio2 ratio could be used in place of Pao2/Fio2 for calculating Pediatric Index of Mortality 2. This must nonetheless be confirmed by a larger prospective multicenter study.