Table 2 Study objectives and key findings

Annane

1999

Compare HRV between sepsis, septic shock and healthy volunteers

TP, LF, LFnu, LF/HF lower in septic shock vs sepsis

Korach

2001

Effects of sepsis, age, sedation, catecholamines and illness severity on sympathovagal balance (LF/HF)

LF/HF ratio <1.5 was associated with sepsis and mortality

Barnaby

2002

Assess if HRV can predict sepsis severity

Negative correlation between LFnu, LF/HF and SOFA score

Pontet

2003

Assess if HRV can predict MODS in sepsis

Low LF and RMSSD associated with MODS

Shen

2003

Assess changes in cardiac autonomic activity during weaning from mechanical ventilation

HF, LF and TP decreased in unsuccessful group during spontaneous breathing trial

Schmidt

2005

Effects of MODS, age, sedation, catecholamines, mechanical ventilation on HRV

Assess if HRV can predict mortality in MODS

Time and frequency domain reduced in MODS

HRV indices affected by mechanical ventilation but not age, sedation or catecholamines

LnVLF associated with 28-day survival.

Papaioannou

2006

Assess if HRV associated with disease severity and mortality

LF/HF ratio negatively correlated with SOFA score

Bourgault

2006

Effects of endotracheal suction on HRV

No significant differences found in HRV indices between closed or open suctioning

Chen

2007

Assess if HRV can predict sepsis severity

Septic shock associated lower LF, LFnu, LF/HF, and higher RMSSD, HF, HFnu

Passariello

2007

Assess if HRV can predict ischaemic sudden cardiac death

SDNN decreases shortly before ischaemic sudden death

Chen

2008

Assess if HRV can predict 28-day mortality

Low SDNN, TP, VLF, LF and LF/HF associated with increased 28-day mortality

Aboab

2008

Assess effect of steroids on HRV in patients with sepsis

LF, LFnu, LF/HF lower in septic shock. Corticosteroids helped increase LFnu values in adrenal insufficiency group.

Nogueira

2008

Assess relationship between HRV, markers of myocardial damage and free fatty acids in sepsis

Low LF, HF and LF/HF associated with mortality

Papaioannou

2009

Assess relationship between HRV and biomarkers of inflammation (CRP, IL-6, IL-10) in patients with sepsis

There is a negative correlation between LFnu, LF/HF and CRP, IL-6, IL-10, SOFA score

Tiainen

2009

Assess if HRV changes (and has prognostic ability) with therapeutic cooling of resuscitated cardiac arrest patients

Higher SDNN, SDANN, TP, LF, HF in the first 48 h of cooling. SDNN >100 ms predicts better neurological outcome

Schmidt

2010

To assess if ACE-I therapy affects short (28-day) and long (365-day) mortality in patients with MODS

ACE-I associated with preserved VLF, LF, HF, TP and survival (28-day and 365-day)

Kasaoka

2010

To trial a real-time HRV measurement and analysis system

LF, HF and LF/HF higher in patients spontaneously breathing compared to mechanical ventilation

Chen

2012

To compare HRV between post-resuscitation cardiac arrest patients and patients with severe sepsis

No significant differences in HRV indices between OOHCA and Severe Sepsis patients

Low LF, LFnu, LF/HF associated with mortality

Gomez Duque

2012

To investigate the incidence of cardiovascular adverse events in patients with sepsis

Deceased patients demonstrated lower SDNN than survivors

Brown

2013

Assess if HRV can predict vasopressor dependence at 24 h in sepsis

Traditional HRV indices not associated with vasopressor requirement after controlling for HR

Green

2013

Association of HRV and illness severity in MODS

Low LFnu and LF/HF associated with increased MODS

Wieske

2013

Relationship between autonomic dysfunction (HRV) and ICU-acquired weakness

Artefacts, mechanical ventilation, sedation, catecholamines and heart rate all associated with TP

% artefacts were associated with TP and LF/HF

No association between HRV and ICU-acquired weakness

Wieske

2013

Compare different autonomic function tests in critically unwell patients (CFT, SWT and HRV)

Only HRV tests associated with SOFA score

Bradley

2013

Impact of sedation and sedation interruptions on HRV

SDNN, RMSSD and HF all increased during sedation interruption (more pronounced in less unwell patients)

Huang

2014

Assess if HRV associated with weaning success or failure

Reduction in TP during SBT associated with failure

Tang

2014

Assess if HRV predicts outcome in ICU stroke patients

Traditional HRV indices were unable to predict outcome

Zhang

2014

Asses if HRV can predict infected pancreatic necrosis or MODS in patients with severe acute pancreatitis

Low LFnu, LF/HF and high HFnu associated with increased MODS and mortality

Schmidt

2014

Assess relationship between HRV and illness severity in CCF and MODS

MODS patients demonstrated lower HRV indices in all parameters compared to CCF patients.

Zaal

2015

To assess if HRV is abnormal in patients with ICU delirium.

No association between HRV and delirium found

Hammash

2015

Assess relationship between HRV and incidence of dysrhythmias during weaning

LF was higher during spontaneous breathing than during controlled mechanical ventilation.

Nagaraj

2016

Assess if sedation levels can be classified by HRV algorithms

Algorithms using composite measures of HRV may discriminate between levels of sedation in ICU patients