Advertisement

Association of intensive care unit occupancy during admission and inpatient mortality: a retrospective cohort study

  • Nicholas A. Fergusson
  • Steve Ahkioon
  • Mahesh Nagarajan
  • Eric Park
  • Yichuan Ding
  • Najib Ayas
  • Vinay K. Dhingra
  • Dean R. Chittock
  • Donald E. G. GriesdaleEmail author
Reports of Original Investigations

Abstract

Purpose

There is conflicting evidence regarding the influence of intensive care unit (ICU) occupancy at the time of admission on important patient outcomes such as mortality. The objective of this analysis was to characterize the association between ICU occupancy at the time of ICU admission and subsequent mortality.

Methods

This single-centre, retrospective cohort study included all patients admitted to the ICU at the Vancouver General Hospital between 4 January 2010 and 8 October 2017. Intensive care unit occupancy was defined as the number of ICU bed hours utilized in a day divided by the total amount of ICU bed hours available for that day. We constructed mixed-effects logistic regression models controlling for relevant covariates to assess the impact of admission occupancy quintiles on total inpatient (ICU and ward) and early (72-hr) ICU mortality.

Results

This analysis included 10,365 ICU admissions by 8,562 unique patients. Compared with ICU admissions in the median occupancy quintile, admissions in the highest and second highest occupancy quintile were associated with a significant increase in the odds of inpatient mortality (highest: odds ratio [OR], 1.33; 95% confidence interval [CI], 1.12 to 1.59; P value < 0.001; second highest: OR, 1.21; 95% CI, 1.02 to 1.44; P value < 0.03). No association between admission occupancy and 72-hr ICU mortality was observed.

Conclusions

Admission to the ICU on days of high occupancy was associated with increased inpatient mortality, but not with increased 72-hr ICU mortality. Capacity strain on the ICU may result in significant negative consequences for patients, but further research is needed to fully characterize the complex effects of capacity strain.

Association entre le taux d’occupation à l’unité de soins intensifs pendant l’admission et la mortalité hospitalière: une étude de cohorte rétrospective

Résumé

Objectif

Les données probantes concernant l’influence du taux d’occupation à l’unité de soins intensifs (USI) lors de l’admission sur d’importants pronostics de patients tels que la mortalité sont conflictuelles. L’objectif de cette analyse était de caractériser l’association entre le taux d’occupation de l’USI au moment de l’admission à l’USI et la mortalité subséquente.

Méthode

Cette étude de cohorte rétrospective monocentrique a inclus tous les patients admis à l’USI à l’Hôpital général de Vancouver entre le 4 janvier 2010 et le 8 octobre 2017. Le taux d’occupation de l’unité de soins intensifs était défini comme le nombre d’heures d’occupation de lit à l’USI utilisées en une journée divisé par le nombre total d’heures d’occupation de lit à l’USI disponibles pour ladite journée. Nous avons créé des modèles de régression logistique à effets mixtes contrôlant les covariables pertinentes afin d’évaluer l’impact des quintiles d’occupation à l’admission sur la mortalité hospitalière totale (USI et étages) et précoce (72 h) à l’USI.

Résultats

Cette analyse a inclus 10 365 admissions à l’USI pour 8562 différents patients. Par rapport aux admissions à l’USI dans le quintile d’occupation médian, les admissions ayant eu lieu dans le quintile le plus élevé et le suivant ont été associées à une augmentation significative de la probabilité de mortalité hospitalière (1er quintile : rapport de cotes [RC], 1,33; intervalle de confiance [IC] 95 %, 1,12 à 1,59; valeur P < 0,001; 2e quintile : RC, 1,21; IC 95 %, 1,02 à 1,44; valeur P < 0,03). Aucune association n’a été observée entre le taux d’occupation à l’admission et la mortalité dans les premières 72 h dans l’USI.

Conclusion

L’admission à l’USI lors d’un jour de forte occupation a été associée à une augmentation de la mortalité hospitalière, mais pas à une augmentation de la mortalité à l’USI dans les premières 72 h. Les pressions sur la capacité de l’USI pourraient engendrer d’importantes conséquences négatives pour les patients, mais des recherches supplémentaires sont nécessaires afin de bien cerner les effets complexes de ces pressions.

Notes

Competing interests

The authors declare that they have no competing interests.

Editorial responsibility

This submission was handled by Dr. Sangeeta Mehta, Associate Editor, Canadian Journal of Anesthesia.

Author contributions

Nicholas A. Fergusson and Donald E. G. Griesdale conceived and designed the overarching framework for the project. Nicholas A. Fergusson performed data retrieval, cleaning, and statistical analyses with the assistance and guidance of Steve Ahkioon and Donald E. G. Griesdale. Mahesh Nagarajan, Vinay K. Dhingra, Yichuan Ding, Eric Park, Najib Ayas, and Dean R. Chittock provided guidance and logistical feedback. All authors contributed to and critically reviewed the final version of this manuscript.

Funding

This project was supported through the University of British Columbia (UBC) Summer Student Research Program (SSRP). DEG is funded through a Health-Professional Investigator Award from the Michael Smith Foundation for Health Research.

Ethics approval and consent to participate

This project was approved by the University of British Columbia Clinical Research Ethics Board (Reference number H17-03588).

Availability of data and materials

The data to support this study were provided by the BC Critical Care Database and Vancouver Coastal Health. Data are available from the authors upon reasonable request and with permission of Vancouver Coastal Health.

Supplementary material

12630_2019_1476_MOESM1_ESM.docx (32 kb)
eTABLE Logistic regression models for total inpatient mortality (intensive care unit and hospital) and early intensive care unit mortality for only completed cases. Supplementary material 1 (DOCX 31 kb)

References

  1. 1.
    Rewa OG, Stelfox HT, Ingolfsson A, et al. Indicators of intensive care unit capacity strain: a systematic review. Crit Care 2018. DOI:  https://doi.org/10.1186/s13054-018-1975-3.CrossRefPubMedPubMedCentralGoogle Scholar
  2. 2.
    Bagshaw SM, Wang X, Zygun DA, et al. Association between strained capacity and mortality among patients admitted to intensive care: a path-analysis modeling strategy. J Crit Care 2018; 43: 81-7.CrossRefGoogle Scholar
  3. 3.
    Tierney LT, Conroy KM. Optimal occupancy in the ICU: a literature review. Aust Crit Care 2014; 27: 77-84.CrossRefGoogle Scholar
  4. 4.
    Iwashyna TJ, Kramer AA, Kahn JM. Intensive care unit occupancy and patient outcomes. Crit Care Med 2009; 37: 1545-57.CrossRefGoogle Scholar
  5. 5.
    Gabler NB, Ratcliffe SJ, Wagner J, et al. Mortality among patients admitted to strained intensive care units. Am J Respir Crit Care Med 2013; 188: 800-6.CrossRefGoogle Scholar
  6. 6.
    Iapichino G, Gattinoni L, Radrizzani D, et al. Volume of activity and occupancy rate in intensive care units. Association with mortality. Intensive Care Med 2004; 30: 290-7.CrossRefGoogle Scholar
  7. 7.
    Chrusch C, Olafson K, McMillan PM, Roberts DE, Gray PR. High occupancy increases the risk of early death or readmission after transfer from intensive care. Crit Care Med 2009; 37: 2753-8.PubMedGoogle Scholar
  8. 8.
    von Elm E, Altman D, Egger M, et al. Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. BMJ 2007; 335: 806-8.CrossRefGoogle Scholar
  9. 9.
    Wenner JB, Norena M, Khan N, et al. Reliability of intensive care unit admitting and comorbid diagnoses, race, elements of Acute Physiology and Chronic Health Evaluation II score, and predicted probability of mortality in an electronic intensive care unit database. J Crit Care 2009; 24: 401-7.CrossRefGoogle Scholar
  10. 10.
    Knaus WA, Draper EA, Wagner DP, Zimmerman JE. APACHE II: a severity of disease classification system. Crit Care Med 1985; 13: 818-29.CrossRefGoogle Scholar
  11. 11.
    Kane RL, Shamliyan TA, Mueller C, Duval S, Wilt TJ. The association of registered nurse staffing levels and patient outcomes: systematic review and meta-analysis. Med Care 2007; 45: 1195-204.CrossRefGoogle Scholar
  12. 12.
    Tarnow-Mordi WO, Hau C, Warden A, Shearer AJ. Hospital mortality in relation to staff workload: a 4-year study in an adult intensive-care unit. Lancet 2000; 356: 185-9.CrossRefGoogle Scholar
  13. 13.
    Dodek PM, Wong H, Norena M, et al. Moral distress in intensive care unit professionals is associated with profession, age, and years of experience. J Crit Care 2016; 31: 178-82.CrossRefGoogle Scholar
  14. 14.
    Johnson-Coyle L, Opgenorth D, Bellows M, Dhaliwal J, Richardson-Carr S, Bagshaw SM. Moral distress and burnout among cardiovascular surgery intensive care unit healthcare professionals: a prospective cross-sectional survey. Can J Crit Care Nurs 2016; 27: 27-36.PubMedGoogle Scholar
  15. 15.
    Halpern SD. ICU capacity strain and the quality and allocation of critical care. Curr Opin Crit Care 2011; 17: 648-57.CrossRefGoogle Scholar
  16. 16.
    Yergens DW, Ghali WA, Faris PD, Quan H, Jolley RJ, Doig CJ. Assessing the association between occupancy and outcome in critically ill hospitalized patients with sepsis. BMC Emerg Med 2015. DOI:  https://doi.org/10.1186/s12873-015-0049-y.CrossRefPubMedPubMedCentralGoogle Scholar
  17. 17.
    Hall AM, Stelfox HT, Wang X, et al. Association between afterhours admission to the intensive care unit, strained capacity, and mortality: a retrospective cohort study. Crit Care 2018. DOI:  https://doi.org/10.1186/s13054-018-2027-8.CrossRefPubMedPubMedCentralGoogle Scholar
  18. 18.
    Terwiesch C, Diwas KC, Kahn JM. Working with capacity limitations: operations management in critical care. Crit Care 2011. DOI:  https://doi.org/10.1186/cc10217.CrossRefPubMedPubMedCentralGoogle Scholar
  19. 19.
    Stelfox HT, Hemmelgarn BR, Bagshaw SM, et al. Intensive care unit bed availability and outcomes for hospitalized patients with sudden clinical deterioration. Arch Intern Med 2012; 172: 467-74.CrossRefGoogle Scholar
  20. 20.
    Anesi GL, Gabler NB, Allorto NL, et al. Intensive care unit capacity strain and outcomes of critical illness in a resource-limited setting: a 2-hospital study in South Africa. J Intensive Care Med 2018. DOI:  https://doi.org/10.1177/0885066618815804.CrossRefPubMedGoogle Scholar

Copyright information

© Canadian Anesthesiologists' Society 2019

Authors and Affiliations

  • Nicholas A. Fergusson
    • 1
  • Steve Ahkioon
    • 2
  • Mahesh Nagarajan
    • 3
  • Eric Park
    • 4
  • Yichuan Ding
    • 3
  • Najib Ayas
    • 5
  • Vinay K. Dhingra
    • 5
  • Dean R. Chittock
    • 5
  • Donald E. G. Griesdale
    • 6
    • 7
    • 8
    Email author
  1. 1.University of British ColumbiaVancouverCanada
  2. 2.Vancouver Coastal HealthVancouverCanada
  3. 3.Sauder School of BusinessUniversity of British ColumbiaVancouverCanada
  4. 4.Faculty of Business and EconomicsUniversity of Hong KongPokfulamHong Kong
  5. 5.Division of Critical Care Medicine, Department of MedicineUniversity of British ColumbiaVancouverCanada
  6. 6.Department of Anesthesiology, Pharmacology, TherapeuticsUniversity of British ColumbiaVancouverCanada
  7. 7.Department of Medicine, Divisions of Critical Care Medicine and NeurologyUniversity of British ColumbiaVancouverCanada
  8. 8.Center for Clinical Epidemiology and EvaluationVancouver Coastal Health Research InstituteVancouverCanada

Personalised recommendations