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.

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.