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Mortality and Morbidities Among Very Premature Infants Admitted After Hours in an Australian Neonatal Intensive Care Unit Network

^a Department of Newborn Care, Royal Hospital for Women, New South Wales, Australia
^b School of Women's and Children's Heath, University of New South Wales, New South Wales, Australia
^c Neonatal Intensive Care Units Data Collection, New South Wales Centre for Perinatal Health Services Research, New South Wales, Australia

	ABSTRACT

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OBJECTIVES. To assess risk-adjusted early (within 7 days) mortality and major morbidities of newborn infants at <32 weeks' gestation who are admitted after office hours to a regional Australian network of NICUs where statewide caseload is coordinated and staffed by on-floor registrars working in shift rosters. We hypothesize that adverse sequelae are increased in these infants.

DESIGNS. We conducted a database review of the records of infants (n = 8654) at <32 weeks' gestation admitted to a network of 10 tertiary NICUs in New South Wales and the Australian Capital Territory from 1992 to 2002. Multivariate logistic regression analysis was performed to adjust for case-mix and significant baseline characteristics.

OUTCOMES. Sixty-five percent of infants were admitted to the NICUs after hours. These infants did not have an increase in early neonatal mortality or major neonatal sequelae compared with their office-hours counterparts. Admissions during late night hours after midnight or fatigue risk periods before the end of a medical 12-hour shift were not associated with higher early mortality. Risk factors significantly predictive of early neonatal death were lack of antenatal steroid treatment, Apgar score <7 at 5 minutes, male gender, gestation age, and being small for gestation.

CONCLUSIONS. Current staffing levels, specialization, and networking are associated with lower circadian variation in adverse outcomes and after-hours admission to this NICU network and have no significant impact on early neonatal mortality and morbidity.

Key Words: premature infant • outcome • office hours • mortality • perinatal services • staffing

Abbreviations: NSW—New South Wales • ACT—Australian Capital Territory • CRIB—clinical risk index for infants • OR—odds ratio • CI—confidence interval

Diurnal variations in hospital death rates are well documented in the adult,^1,2 pediatric,³ and neonatal literature. The latter by using birth registration data^4–12 and, more recently, with risk-adjusted admission data.^13,14 Most of these studies only compared mortality between night and day, regardless of public holidays and weekends, which are times presumably similar to night hours in terms of staffing and access to diagnostic and therapeutic services, including obstetrics, anesthesiology, and radiology.

Any circadian variation in mortality or morbidity has important implications for the organization and delivery of care services, because millions of births take place after office hours throughout the world.⁸ Reasons for this variation are widely perceived to be because of lower levels and expertise of staffing,¹⁵ including support personnel,^16,17 and reduced access to diagnostic¹⁸ and therapeutic services after working hours.¹⁹ Other reasons may include errors of judgment related to physical and mental fatigue from night shifts^20,21 and overwork.^22–24

The objective of this study was to compare the risk-adjusted early neonatal mortality rates (death within 7 days of a NICU admission) and major morbidities of infants at <32 weeks' gestation admitted during public holidays, weekends, and after hours with those of infants admitted during weekdays within office hours to 10 NICUs in the state of New South Wales (NSW) and in the Australian Capital Territory (ACT) in Australia from 1992 to 2002. The contribution of fatigue to outcome was assessed by comparing the results of infants admitted during "higher fatigue" (or after regular office hours) periods to those admitted during "lower fatigue" (or normal office hours) periods. The "structural competency" of the roster system was assessed by comparing the outcome of "higher demand" admissions between the 2 time periods. We hypothesized that preterm (and, thus, high risk) infants admitted to NICUs during public holidays, weekends, and after office hours have increased mortality and morbidity compared with those admitted during weekdays and office hours. It is also hypothesized that admissions during the hours after midnight or toward the end of long shifts would be associated with a higher rate of problems.

	METHODS

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This study was a retrospective analysis of prospectively collected data testing an a priori hypothesis. All of the infants who were delivered before 32 weeks' gestational age and consecutively admitted to 1 of the 10 tertiary NICUs in NSW and the ACT (8 perinatal centers and 2 children's hospitals) during 1992 and 2002 were included in the study. Geographically, the ACT lies wholly within the state of NSW, and the NICU forms part of a complete regional network. All of the infants regardless of gestation or born in nontertiary hospital if needing mechanical ventilation were transferred to 1 of the 10 NICUs.

The study population was composed of 8654 consecutive infants at <32 weeks' gestation who were born between January 1, 1992, and December 31, 2002, and admitted to 1 of the 10 tertiary NICUs in NSW and the ACT. These 2 states have a combined total population of 6984200 and 90683 live births per year.²⁵ Data regarding births, admission, morbidities, and neonatal mortality were extracted from the NICUs' database, a collaborative effort between the 10 units. The details, definitions, and accuracy of this database have been described elsewhere.²⁶

The principal causes of early neonatal death were coded using the International Classification of Diseases 9th Revision Clinical Modification²⁷ for the period 1992–1998 and the International Classification of Diseases and Related Health Problems, 10th Revision, Australian Modification,²⁸ for 1999–2002. The outcome variable of this study was early neonatal mortality (death within 7 days of NICU admission), categorized by time of admission. We ignored deaths after 7 days of NICU admission, because these were less likely to have been related to interventions during admission.¹⁴

We categorized admission time as office hours (8:00 AM to 6:00 PM, Monday to Friday, excluding public holidays) or after hours (6:01 PM to 7:59 AM, Monday to Friday, public holidays [gazetted public holidays in NSW and the ACT], and weekends [Saturdays and Sundays]). We elected to group after office hours, public holidays, and weekends together, because, generally, only essential services are available on site during those times.^1,19

Statewide Neonatal Service Organization and Caseload Coordination
Although the tertiary perinatal hospitals are all clustered within metropolitan areas, a specialized Neonatal and Pediatric Emergency Transport Service has been established, and this team transfers 700 newborn infants each year from nontertiary to tertiary centers.²⁹ All of the infants requiring mechanical ventilation were transferred to 1 of the 10 NICUs (mean time from birth to admission: 6:29 ± 3:16 hours:minutes). Four intermediate NSW nurseries provide continuous positive airway pressure for infants at >32 weeks' gestation under a randomized, control trial protocol. Retrieval teams consist of medical and nursing staff. The retrieval consultant and receiving NICU neonatologist assist the retrieval team via teleconference with stabilization of the infant.

The NSW Pregnancy and Newborn Services Network has a team of on-call obstetric consultant advisors to coordinate and provide advice for the management of high-risk mothers, who may or may not be transferred antenatally to 1 of the 8 perinatal centers (in which the NICUs are located) from nontertiary rural and urban hospitals via road or air ambulance. This has resulted in a high (>90%) inborn rate and antenatal steroid rate (>80% for both inborn and outborn infants) in the NICU population at <32 weeks' gestation.

The 10 tertiary NICUs in this statewide network have a capacity of 61 ventilator beds (median: 6; range: 4–11 per hospital). One unit is a combined pediatric and neonatal unit with 4 neonatal beds. There are a total of 211 neonatal beds in this tertiary system, including nonventilator intensive care and step-down (or intermediate-level) beds. Coordination of in utero or ex utero high-risk referrals is assisted by an intranet bed availability bulletin board, which directs referrals to the unit with the most readily available bed when any particular unit is full or close to full to reduce the risk of overloading. All of the in utero and ex utero referred infants are transferred back to their respective nontertiary or tertiary hospital of origin for continuing care after completion of intensive care.

Perinatal Care Staffing
Infants admitted into the intensive care sections of each NICU are looked after by subspecialty neonatologists (median: 4 per unit; range: 4–5 per unit). General or visiting pediatricians do not share the NICU admissions and after-hours roster. General neonatal surgery is available in 4 hospitals and cardiac surgery in 2 hospitals. Extracorporeal membranous oxygenation has not been available since 1994.

All of the units have 1 nurse educator and 1 neonatal clinical nurse consultant. Five units participate in a neonatal intensive care nursing diploma program. New ventilated admissions and acutely ill infants are cared for by 1 experienced neonatal nurse with the assistance of the nursing team leader or other nursing colleagues. For stable NICU infants receiving more prolonged respiratory support (continuous positive airway pressure or mechanical ventilation), there may be a 1:2 nurse/infant ratio.

All of the perinatal centers have subspecialty fetal-maternal specialists. After-hours on-floor medical staffing is based on the maintenance of a baseline shift roster of obstetric and anesthetic registrars (experienced residents or house officers enrolled in subspecialty training) who have ensured proficiency in procedural skills as part of accreditation for professional college requirements. Obstetric consultants and fellows or senior registrars are on call at home after office hours. The fetal-maternal specialists participate in the statewide perinatal advisory roster.

Fatigue Risk Periods in NICU and the Shift Duties of On-Floor Medical Staff
During the study period, 6 of the 10 units had accredited neonatal fellow positions for advanced subspecialty training. One unit employed 2 neonatal nurse practitioners, and 2 units had 1 career medical officer each. Late night hours (after midnight) and end-of-shift periods were considered as high-fatigue risks. On-floor medical cover was provided by pediatric and specialty neonatal registrars. In NSW and the ACT, the on-floor NICU registrars work in shift rosters and do not extend duty hours from office hour shifts. Thus, the numbers of on-floor core NICU registrars do not substantially change throughout the day. The registrars mostly work in 12-hour shifts, with the exception of 1 unit, where the registrars work in 8-hour shift duties during weekdays and in 12-hour shifts during weekends or holidays. Registrars work 3–4 shifts per week in a pattern that is not dissimilar to nursing shifts in North America.

Hence, in general, there are 4 types of shifts: (1) weekday daytime, (2) weeknights, (3) weekends/holidays days, and (4) weekends/holidays night. Consultant neonatologists and subspecialty fellows are usually on call after hours from home but would readily be available to stay in-house for anticipated emergencies or high-risk deliveries.

Other than the late night hours between midnight and 8 AM office hours, we defined a "high-fatigue" period for on-floor NICU registrars as the last 4 hours of the shift before a handover to the next registrar. We grouped these 2 periods together as "higher fatigue risk" periods and compared them to other segments of each day, considered as "low-fatigue risk" periods. We defined "higher demand" admissions as those that required personnel with experience in addressing the acute physiologic needs of premature infants,³⁰ for example, emergency intubations.

Statistical Analysis
Statistical analyses were performed using SPSS version 11.5.0.³¹ The ² test and t test were used where appropriate. Multivariate analysis was performed by means of multiple logistic regression.^32,33 Confounding factors entered into the model included pertinent clinical factors associated with neonatal mortality and significant factors identified in the univariate comparisons. The level of statistical significance for all of the analyses was set at P < .05 using 2-tailed comparisons. The significance level was not changed when multiple comparisons were performed.³⁴

	RESULTS

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Among the 8654 infants admitted over the 10-year period, 3020 (34.9%) were during office hours, 3177 (36.7%) were after-hours admissions during weekdays, and 2457 (28.4%) were during weekends and public holidays. The later 2 groups were grouped together as after-hours admissions (n = 5634 [65.1%]).

Table 1 shows the perinatal characteristics of the study population. Infants admitted after hours were significantly less likely to be treated with antenatal steroids (83.3% vs 85.2%, respectively) and more likely to be delivered by emergency (in labor) cesarean section (22.4% vs 17.9%, respectively). After-hours infants were significantly more premature but also had a higher birth weight than office-hours infants. The clinical risk index for infants (CRIB) score, a measure of initial disease severity, was available for all of the admissions from 1994 (69.7% of the study population). The CRIB score was similar between the 2 groups (after hours: 3.8 ± 4.1; office hours: 3.7 ± 3.8; P = .226).

View larger version (18K): [in this window] [in a new window]   FIGURE 1 Early neonatal mortality for infants <32 weeks by time of admission: the crude mortality rates for admission for each of the 24 clock hours. The admissions born by cesarean section or after spontaneous onset of labor are also shown. Late night hours are defined as from midnight to 8 AM.

View larger version (24K): [in this window] [in a new window]   FIGURE 2 Comparison of early neonatal mortality for NICU admissions: crude mortality rate of admissions during or after office hours by day of the week or during the 12-hour day and night registrar shifts. WE indicates weekends; PH, public holidays. aP > .05.

View larger version (17K): [in this window] [in a new window]   FIGURE 3 Comparison of early neonatal mortality among selected high demand groups: crude mortality of high-demand infants admitted during and after office hours. aP > .05.

	DISCUSSION

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Our study has demonstrated that admission time has little impact on outcome for high-risk infants admitted to NICUs in this regional network in Australia. We did not analyze time of death as part of this study, because we felt that a significant proportion of deaths, especially in this high-risk environment, may be planned as elective office-hours events. Admission is the most vulnerable period for seriously ill infants, because stabilization requires considerable expertise. Infants born within office hours were more likely to have had an interventional delivery for an antenatal diagnosis of growth restriction and, thus, a lower birth weight, whereas infants born after office hours were more likely to have had a less planned birth, as indicated by the lower rates of antenatal steroids and the higher rates of emergency cesarean sections and lower Apgar scores. Nevertheless, these adverse factors had minimal impact on early neonatal mortality and major neonatal sequelae, and the results were consistent regardless of whether the infants were born in tertiary or nontertiary centers.

These results are contradictory to those of some international studies. Lee et al¹⁴ found a 60% higher mortality among night admissions in the <32 weeks' gestation inborn infants in the Canadian network. This was equivalent to 29 excess deaths per 1000 infants. In this study, night admissions were defined as admission from 6 PM to 8 AM, irrespective of weekends or holidays. No difference in the outborn population was found. Luo and Karlberge⁸ reported that infants born at night (from 6 PM to 8 AM) had twice the risk of death. Studies from the United Kingdom and Germany^9–11 had similar findings. Gould et al¹³ evaluated the neonatal mortality among infants >500 g in California and observed a significant increase in mortality (2.80 per 1000 births during weekdays compared with 3.12 per 1000 weekend births) but did not account for weeknight data, which is a period that could also have critically low resource levels.

The differences suggested by our study of NICU admissions may be related to the even distribution of on-floor NICU resident medical staff working around a structured shift roster, which may decrease fatigue, a condition consistently highlighted in the literature as a significant contribution to adverse outcome.^30,35 We, however, found that there was a nonsignificant trend toward slightly increased mortality among 3 of the 5 "high-demand" infant subgroups: those who required emergency intubation and ventilation or who were born outside of a perinatal referral center. This finding, however, was not consistent, because it was not evident in those infants born by emergency section or those who had a low Apgar score.

Lee et al¹⁴ found that early mortality of after-hours inborn admissions from 6 PM to 8 AM was 60% higher even after adjustment for the presence of experienced medical staff, such as fellows or consultants. Unfortunately, our database did not include information regarding the level of expertise, and, therefore, the impact of medical attendance on outcome could not be assessed in this study. Nonetheless, the results demonstrate that the current practice of the 10 participating units seems to be adequate in limiting morbidity and mortality. The statistically insignificant trend of higher after-hours mortality in the 30–31 weeks' gestation subgroup (2.0% vs 1.4%) should be interpreted with caution, because elective deliveries during office hours may be overrepresented with infants of higher gestation in the absence of fetal distress.

Australian NICUs have often been compared in a more favorable light to other developed countries. For example, adjusted mortalities are lower than the United Kingdom in both neonatal³⁶ and pediatric³⁷ intensive care populations, a fact attributed by the authors^36–38 to be because of size (Australian units are larger), a higher degree of specialization of both medical and nursing staff, and a greater degree of centralization, thereby preventing dilution of resources and clinical commitment.^39–41

However, individual NICU size in the NSW/ACT network is much smaller than most units in North America. In contrast to the Canadian Network, the NSW/ACT system acts regionally to direct perinatal traffic to buffer excessive workloads for any individual unit so that in many ways the system functions as 1 large amalgamated service network. Associations between differences in comparative international outcomes and particular organizational characteristics of health services must, therefore, be inferred only with caution.⁴² Although we found no indication of compromised after-hours care in this network, deficiencies may very well exist at the institutional level, and it will be important to assess whether each specific NICU is equally safe with regard to the fluctuation of admissions, patient volume, staff workload and work shifts, level of hospital care, and the socioeconomic profile of the women giving birth.

	CONCLUSIONS

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
We found no evidence that quality of perinatal care in NSW and the ACT was compromised by after-hours resources. The implications of this report for staffing policy, shift work, and ethical practice remain to be tested, but it provides strong evidence that current models of staffing, specialization of care provision, and sharing of workload within a network is associated with a lower circadian variation in deaths among high-risk infants. Further research is needed to identify the differences in the crucial processes of clinical care that account for differences in mortality.

	ACKNOWLEDGMENTS

 
We thank the directors, the NICU members, and the audit officers of all tertiary units in supporting this collaborative study: New South Wales Pregnancy and Newborn Services Network: Professor David Henderson-Smart; NICU: Barbara Bajuk (Coordinator) and Trina Vincent (Research Officer); The Canberra Hospital: Assistant Professor Graham Reynolds (Director), Dr Alison Kent, John Edwards, John Hunter Hospital, Dr Chris Wake (Director), and Lynne Cruden; Royal Prince Alfred Hospital: Assistant Professor Nick Evans (Director), Dr Phil Beeby, and Shelley Reid; Liverpool Hospital: Dr Robert Guaran (Director), Dr Ian Callender, Dr Jacqueline Stack, Kathryn Medlin, and Sara Wilson; Nepean Hospital: Dr Lyn Downe (Director) and Mee Fong Chin; The Children's Hospital at Westmead: Dr Robert Halliday (Director), Dr Nadia Badawi, and Karen Walker; Royal North Shore Hospital: Dr Tushar Bhuta (Director), Dr Jennifer Bowen, Dr Martin Kluckow, and Vicki Gallimore; Sydney Children's Hospital: Dr Barry Duffy (Director), Dr Gary Williams, Janelle Young, and Denise Georgakopoulos; Westmead Hospital: Dr Marilyn Rochefort (Director) and Jane Baird; and Royal Hospital for Women: Dr Kei Lui (Director), Dr Paul Garvey, and Dianne Cameron. We also thank the infants and their families and the nursery, obstetric, and medical records staff of the obstetric and children's hospitals in New South Wales and the Australian Capital Territory.

	FOOTNOTES

 
Accepted Oct 18, 2005.

Address correspondence to Kei Lui, MBBS, FRACP, MD, Department of Newborn Care, Royal Hospital for Women, Barker St, Locked Bag 2000, Randwick, 2031 New South Wales, Australia. Email: E-mail: luik{at}sesahs.nsw.gov.au

The authors have indicated they have no financial relationships relevant to this article to disclose.

	REFERENCES

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