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Article Excerpt
The expression "you can't rush mother nature" is certainly true when considering the discharge of infants from the neonatal intensive care unit (NICU). An infant born 2 or 3 months premature may often spend an equivalent time or more in the NICU maturing until additional physiologic functioning makes discharge feasible. The costs associated with prematurity are staggering. The Institute of Medicine (IOM) estimates that annual medical costs associated with preterm birth in the United States was $16.9 billion or $33,200 per infant born premature (IOM 2007). The average inpatient costs in the first year of life for premature infants <28 weeks gestation is approximately $181,000, and even infants with gestational age (GA) between 28 and 31 weeks have inpatient costs of $85,000 (IOM 2007).
Defining exactly when a baby may finally be discharged entails a complicated algorithm at most hospitals, but certain requirements must be met before most neonatologists would be comfortable sending the premature baby home (American Academy of Pediatrics 1998). Despite a general consensus, there is considerable variation in the decision as to when to discharge infants, and consequently, there may be considerable variation in the costs experienced by the health care system caring for these patients (Brooten et al. 1986; Casiro et al. 1993).
After the child is free of obvious physical supports such as the need for mechanical ventilation or intravenous fluids and medications, physiologic competencies usually recognized as necessary before discharge include the following (Schmidt and Levine 1990; Medoff-Cooper 1994; American Academy of Pediatrics 1998; Raddish and Merritt 1998): (1) Maintenance of body temperature fully clothed in an open crib at room temperature. (2) Coordinated sucking, swallowing, and breathing while taking an adequate volume of feeding. (3) Sustained pattern of weight gain. (4) Demonstration of maturity and stability in cardiorespiratory function through avoiding apnea and bradycardia episodes for a specified period of time (say, at a minimum, 2-5 days). Often, stimulants such as caffeine are necessary to prevent these episodes. (5) Another dimension, not absolutely required but highly desired, is to be free of the need for supplemental oxygen before discharge, although some patients with chronic lung conditions may require oxygen at home. Finally, aside from the child's physiologic status, the family's ability to care for the fragile premature infant must be evaluated and demonstrated.
In this study we ask a simple question. When a premature baby stays a few days longer in the hospital, does the accompanying increased physiologic maturity reduce expenditures after discharge? Do a few days matter? This question is by no means trivial. As NICUs have rules and styles of practice that govern discharge, thousands of dollars per admission depend on whether these infants go home a few days earlier or later (Rogowski et al. 2001).
To answer this question, we collected daily physiologic data for 1,402 premature babies near discharge, and matched half the 1,402 babies (701 "Early" babies), to the other half of the babies, 701 "Late" babies, who looked very similar on the day each Early baby went home, but who actually were discharged between 2 and 7 days later (in terms of postmenstrual age [PMA]). We chose 2-7 days because this represents a period of discretion on the part of neonatologists that has economic significance. This is a form of "risk set matching," which means that when a baby is discharged from the hospital, the baby is paired with another baby who might have been discharged (who was "at risk of discharge") but who was not discharged (Li, Propert, and Rosenbaum 2001; Lu 2005). The matching was optimal in the sense that it minimized the total covariate distance between babies in the same pair among all possible pairings of the 1,402 babies ("optimal nonbipartite matching" [Derigs 1988]).
The matching controlled numerous maturity and risk factors relevant to discharge, including a daily time-dependent propensity score for discharge (Li, Propert, and Rosenbaum 2001; Lu 2005). So, in the end, we have 701 pairs of two babies who looked similar on the day (the PMA) that the earlier baby was discharged, although one baby stayed in the hospital a few more days. Were the extra days of benefit to the baby who received them? Or did they add to costs without benefit to the baby? We will ask, in various ways: (1) Are 6-month total costs comparable between the Early and Late babies? and (2) Are 6-month clinical outcomes similar or not?
METHODS
Study Population
The Infant Functional Status (IFS) Study examined premature births at the Northern California Kaiser Permanente Medical Care Program (KPMCP), which is a managed care organization with integrated information services whose perinatal outcomes have been described in a number of previous reports (Escobar et al. 1995, 2005; Escobar 1999; Joffe et al. 1999; Newman et al. 1999; Smith et al. 2004; Escobar, Clark, and Greene 2006). Eligible infants for the IFS study were born at one of five KPMCP hospitals between 1998 and 2002. To create our cohort, all infants surviving to discharge who were born at a GA of 32 weeks or less were included in the cohort, plus a random sample of infants with a GA of 33 or 34 weeks. Infants were excluded for major congenital anomalies; mechanical ventilation at home after discharge; placement of a ventriculo-peritoneal shunt or other major surgery that necessitated transfer of the infant to a hospital outside KPMCP (e.g., for cardiac surgery); or loss to follow-up within 1 year of discharge from the NICU. Overall, 2,144 infants were initially screened for the study; 670 infants met one of the exclusion criteria, and an additional 42 infants had incomplete medical records from their NICU admission. Thus, the final IFS cohort included 1,402 infants with 246 having a GA of 28 weeks or below.
This project was approved by the Institutional Review Board of The Children's Hospital of Philadelphia, The University of Pennsylvania, and the Northern California KPMCP.
Data Collection
Electronic Data. We estimated inpatient and outpatient costs based on daily resource consumption from the health system perspective. For inpatients, we had access to all coded diagnoses, as well as resource information on a daily basis. This included physician and nurse staffing, pharmacy, radiology, laboratory medicine, and level of care information. For outpatients, we obtained information on all office visits, pharmacy costs, outpatient home care expenditures, emergency department encounters, and subsequent hospital admissions.
We utilized resource estimates from KPMCP. We estimated a base cost for hospital procedures, radiologic tests, and outpatient visits using 2001 Medicare data (Centers for Medicare and Medicaid Services 2002b); pharmacy resources using the 2001 Red Book of wholesale drug prices for pharmacy resources (2001); personnel costs using the Bureau of Labor Statistics (2002b); laboratory costs using 2001 Medicare data (Centers for Medicare and Medicaid Services 2002a); and room costs from prior literature (Kotagal et al. 1997; Chalom, Raphaely, and Costarino 1999; Rogowski 1999). All base costs were adjusted to 2001 dollars using inflation data from the Bureau of Labor Statistics (2002a).
In-Patient Chart Abstraction. Starting from age 31...
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