Standardized mortality rate in groups of patients treated in a pediatric intensive care unit

Abstract

Sastav populacija bolesnika može među jedinicama intenzivnog liječenja djece biti bitno različit. Razlike u sastavu između izvorne populacije na kojoj je sustav izveden i populacija bolesnika na kojima se sustav predviđanja smrtnosti primjenjuje, kao i pojedinih skupina unutar populacije, čine točnost predviđanja smrtnosti nepouzdanom. Prikupili smo pokazatelje za izračun Paediatric Index of Mortality (PIM 2) sustava za 591 uzastopce primljena bolesnika u jedinicu intenzivnog liječenja djece (JILD). Izračunali smo odvojeno zamijećenu smrtnost (ZS), predviđenu smrtnost (PS) i standardizirani omjer smrtnosti (SOS) za različite skupine bolesnika. PS je bila viša od ZS za kirurške bolesnike, kao i za bolesnike primljene u hitnim stanjima. Unutar dijagnostičkih skupina, SOS je bio < 1 za neurološke bolesnike, a u bolesnika s bolestima dišnog sustava bio je > 1. Unutar dobnih skupina, SOS je bio > 1 u predškolske djece, a u adolescenata je SOS bio 1 u bolesnika koji su dugo liječeni. Predikcijska sposobnost sustava PIM2 nije, dakle, jednaka za sve skupine unutar populacije bolesnika. To znači da razlika u sastavima populacija bolesnika može biti uzrokom manje preciznosti izračuna PS u odnosu na ZS. Ova poteškoća može biti izrazita u jedinicama s malim i jednolikim populacijama bolesnika.The composition of patient population in pediatric intensive care units may vary significantly. The differences in composition between original population based on which the system was derived and patient population on whom the mortality rate forecast system is applied, as on certain groups within the population, make the accuracy of mortality predictions unreliable. We collected factors for calculation of Paediatric Index of Mortality (PIM 2) system for 591 patients consecutively admitted to pediatric intensive care unit (PICU). We separately calculated observed mortality (OM), predicted mortality (PM) and standardized mortality rate (SMR) for different groups of patients. PM was higher than OM for surgical patients, as well as for emergency patients. Within diagnostic groups, SMR was 1. Within age groups, SMR was > 1 in preschool children, and 1 in longterm hospitalized patients. Predictive ability of PIM2 system is, therefore not equal for all groups within patient population. Meaning, the difference in patient population composition can be the cause of less precise calculation of PM compared to OM. This problem can be more expressed in units with smaller and uniform patient populations