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Review

Clinical review: A review and analysis of heart rate variability and the diagnosis and prognosis of infection

Saif Ahmad1, Anjali Tejuja1, Kimberley D Newman1, Ryan Zarychanski23 and Andrew JE Seely145*

Author Affiliations

1 Ottawa Hospital Research Institute, Ottawa, Ontario, K1Y 4E9, Canada

2 Section of Critical Care, Department of Internal Medicine, University of Manitoba, Winnipeg, Manitoba, R3A 1R9, Canada

3 Department of Haematology and Medical Oncology, CancerCare Manitoba, Winnipeg, Manitoba, R3E 0V9, Canada

4 Division of Thoracic Surgery, University of Ottawa, Ottawa, Ontario, K1H 8L6, Canada

5 Department of Critical Care Medicine, University of Ottawa, Ottawa, Ontario, K1H 8L6, Canada

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Critical Care 2009, 13:232  doi:10.1186/cc8132

Published: 24 November 2009

Abstract

Bacterial infection leading to organ failure is the most common cause of death in critically ill patients. Early diagnosis and expeditious treatment is a cornerstone of therapy. Evaluating the systemic host response to infection as a complex system provides novel insights: however, bedside application with clinical value remains wanting. Providing an integrative measure of an altered host response, the patterns and character of heart rate fluctuations measured over intervals-in-time may be analysed with a panel of mathematical techniques that quantify overall fluctuation, spectral composition, scale-free variation, and degree of irregularity or complexity. Using these techniques, heart rate variability (HRV) has been documented to be both altered in the presence of systemic infection, and correlated with its severity. In this review and analysis, we evaluate the use of HRV monitoring to provide early diagnosis of infection, document the prognostic implications of altered HRV in infection, identify current limitations, highlight future research challenges, and propose improvement strategies. Given existing evidence and potential for further technological advances, we believe that longitudinal, individualized, and comprehensive HRV monitoring in critically ill patients at risk for or with existing infection offers a means to harness the clinical potential of this bedside application of complex systems science.