Key result
Heart rate variability metrics increased early during hemorrhage but failed to discriminate survivors from non-survivors, whereas metabolic and hemodynamic variables more reliably reflected hemorrhagic shock severity.
Why the study?
Does heart rate variability analysis discriminate survivors from non-survivors in an experimental model of hemorrhagic shock and resuscitation in pigs?
Does heart rate variability analysis discriminate survivors from non-survivors in an experimental model of hemorrhagic shock and resuscitation in pigs?
In a porcine model of hemorrhagic shock, traditional hemodynamic and metabolic variables were more reliable than heart rate variability metrics for discriminating survivors from non-survivors.
HRV metrics should not guide resuscitation or outcome prediction in shock; leaves open their added value versus hemodynamics in clinical studies.
BACKGROUND: The analysis of heart rate variability (HRV) has been shown as a promising non-invasive technique for assessing the cardiac autonomic modulation in trauma. The aim of this study was to evaluate HRV during hemorrhagic shock and fluid resuscitation, comparing to traditional hemodynamic and metabolic parameters. METHODS: Twenty anesthetized and mechanically ventilated pigs were submitted to hemorrhagic shock (60% of estimated blood volume) and evaluated for 60 minutes without fluid replacement. Surviving animals were treated with Ringer solution and evaluated for an additional period of 180 minutes. HRV metrics (time and frequency domain) as well as hemodynamic and metabolic parameters were evaluated in survivors and non-survivors animals. RESULTS: Seven of the 20 animals died during hemorrhage and initial fluid resuscitation. All animals presented an increase in time-domain HRV measures during haemorrhage and fluid resuscitation restored baseline values. Although not significantly, normalized low-frequency and LF/HF ratio decreased during early stages of haemorrhage, recovering baseline values later during hemorrhagic shock, and increased after fluid resuscitation. Non-surviving animals presented significantly lower mean arterial pressure (43±7 vs 57±9 mmHg, P<0.05) and cardiac index (1.7±0.2 vs 2.6±0.5 L/min/m2, P<0.05), and higher levels of plasma lactate (7.2±2.4 vs 3.7±1.4 mmol/L, P<0.05), base excess (-6.8±3.3 vs -2.3±2.8 mmol/L, P<0.05) and potassium (5.3±0.6 vs 4.2±0.3 mmol/L, P<0.05) at 30 minutes after hemorrhagic shock compared with surviving animals. CONCLUSIONS: The HRV increased early during hemorrhage but none of the evaluated HRV metrics was able to discriminate survivors from non-survivors during hemorrhagic shock. Moreover, metabolic and hemodynamic variables were more reliable to reflect hemorrhagic shock severity than HRV metrics.
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Salomão et al. (2015) studied Hemorrhagic shock (n=20). Heart rate variability (HRV) monitoring vs. Traditional hemodynamic and metabolic parameters was evaluated on Prediction of mortality (discrimination between survivors and non-survivors). Heart rate variability metrics increased early during hemorrhage but failed to discriminate survivors from non-survivors, whereas metabolic and hemodynamic variables more reliably reflected hemorrhagic shock severity.
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