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The impact of pediatric intensive care unit volume on mortality: a hierarchical instrumental variable analysis
James P Marcin1, Jun Song, J Paul Leigh
1UC Davis Children's Hospital, University of California Davis School of Medicine, Sacramento, CA 95817, USA. jpmarcin@ucdavis.edu
Insights
Higher pediatric intensive care unit (PICU) admission volume is linked to lower mortality. However, optimal outcomes occur in mid- to large-sized PICUs, not the very largest.
Area of Science:
- Pediatric Critical Care Medicine
- Healthcare Quality Improvement
- Hospital Operations Research
Background:
- Pediatric intensive care unit (PICU) admission volume is a potential indicator of quality.
- Understanding the relationship between PICU volume and patient outcomes is crucial for optimizing care.
Purpose of the Study:
- To evaluate the association between annual PICU admission volume and patient mortality.
- To identify optimal PICU sizes for improved patient outcomes.
Main Methods:
- Nonconcurrent cohort study of 34,880 pediatric admissions across 15 U.S. PICUs.
- Instrumental variable analysis adjusted for case mix and illness severity using PRISM III.
- Mixed-effects, hierarchical modeling to account for patient similarities across PICUs.
Main Results:
- Higher PICU volume was associated with lower severity-adjusted mortality (OR=0.68 per 100 patient increase).
- Lowest mortality rates were observed in PICUs with 992-1,491 annual admissions.
- Improved outcomes were most notable in patients with lower predicted mortality risk (<10% PRISM III).
Conclusions:
- While higher volume correlates with better outcomes, mid- to large-sized PICUs demonstrate the best results.
- Data support minimum annual admission criteria for PICUs.
- Very high PICU volumes may exceed ideal operational capacity, potentially impacting care quality.
Objective:
To evaluate the relation between annual pediatric intensive care unit (PICU) admission volume and mortality.
Design:
Nonconcurrent cohort design.
Setting:
Pediatric patients included in the most currently available research database from the Pediatric Intensive Care Unit Evaluations (PICUEs).
Patients:
A total of 34,880 consecutive pediatric admissions to a contemporary volunteer sample of 15 U.S. PICUs.
Measurements And Main Results:
We conducted an instrumental variable analysis and adjusted for similarities between patients admitted to different PICUs using mixed-effects, hierarchical techniques. Case mix and severity of illness was adjusted for using patient-level data and the Pediatric Risk of Mortality, version III (PRISM III). On average, admission to higher-volume PICUs was associated with lower severity-adjusted mortality (odds ratio = 0.68 per 100 patient increase in volume; 95% confidence interval: 0.52-0.89) when volume was analyzed as a linear term; however, when PICU volume was analyzed as a quadratic term, we found the lowest severity-adjusted mortality rates among PICUs with annual admission volumes between 992 and 1,491. Furthermore, lower severity-adjusted mortality rates were primarily found among patients with less than a 10% PRISM III predicted risk of mortality.
Conclusions:
Although there is an association between lower severity-adjusted mortality among higher volume PICUs, our data suggest that best outcomes are among mid- to large-sized PICUs. These data support minimum annual admission criteria for PICUs but raise the concern that PICUs with very high annual admission volumes may operate beyond an ideal capacity.