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Heart rate variability after acute traumatic brain injury in children
A K Biswas1, W A Scott, J F Sommerauer
1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, USA.
Insights
Heart rate variability (HRV) power spectral analysis revealed autonomic dysfunction in children with severe traumatic brain injury. Lower HRV ratios correlated with increased intracranial pressure, decreased cerebral perfusion pressure, and poorer outcomes, suggesting prognostic value.
Area of Science:
- Pediatric critical care medicine
- Neuroscience
- Autonomic nervous system research
Background:
- Acute traumatic head injury in children can lead to severe neurological complications.
- Monitoring intracranial pressure (ICP) and cerebral perfusion pressure (CPP) is crucial for managing these patients.
- Autonomic dysfunction may play a role in the severity and prognosis of pediatric traumatic brain injury.
Purpose of the Study:
- To evaluate heart rate variability (HRV) using power spectral analysis in children with acute traumatic head injury.
- To determine the relationship between HRV parameters (specifically the LF/HF ratio) and ICP, CPP, and patient outcomes.
- To explore the potential of HRV analysis as an adjunct tool for assessing neurologic insult severity and prognosis.
Main Methods:
- A prospective case series study was conducted in a pediatric intensive care unit.
- Fifteen critically ill children with traumatic brain injury and four control subjects were enrolled.
- Heart rate variability was assessed using power spectral analysis, calculating the low-frequency to high-frequency (LF/HF) power ratio over hourly and daily intervals.
Main Results:
- No linear correlation was found between the LF/HF ratio and ICP or CPP.
- A significant decrease in the LF/HF ratio was observed when ICP exceeded 30 mm Hg or CPP fell below 40 mm Hg.
- Lower LF/HF ratios were associated with lower Glasgow Coma Scale scores, progression to brain death, and less favorable outcomes.
Conclusions:
- Elevated ICP (>30 mm Hg) or low CPP (<40 mm Hg) in pediatric traumatic brain injury may indicate significant autonomic dysfunction.
- HRV power spectral analysis, particularly the LF/HF ratio, shows promise as a tool for assessing neurologic injury severity and predicting patient outcomes.
- The LF/HF ratio may help identify children at risk for brain death and those likely to have favorable recovery.
Objective:
To evaluate heart rate variability (HRV) by power spectral analysis of heart rate and its relationship to intracranial pressure (ICP), cerebral perfusion pressure (CPP), and outcomes in children with acute traumatic head injury.
Design:
Prospective, case series.
Setting:
Pediatric intensive care unit in a level II trauma center/children's hospital.
Subjects:
Fifteen critically ill children with documented acute traumatic brain injury and four control subjects.
Interventions:
None.
Measurements And Main Results:
The normalized total power from 0.04 to 0.15 Hz was used to quantify low-frequency HRV and from 0.15 to 0.40 Hz to quantify high-frequency HRV. The ratio of low- to high-frequency (LF/HF) power was used as a measure of sympathetic modulation of heart rate. The power spectral data from the 5-min samples were averaged over each hour of data collection, and an hourly LF/HF ratio was obtained based on a 60-min electrocardiogram collection (twelve 5-min segments). The daily mean LF/HF ratio was calculated from the hourly LF/HF measurements. We found no linear correlation between the LF/HF ratio and either ICP or CPP (p = NS). There was a significant decrease in the LF/HF ratio when the intracranial pressure was >30 mm Hg (p < .001) or the cerebral perfusion pressure was <40 mm Hg (p < .001). Children with a Glasgow Coma Scale score of 3-4 had a lower LF/HF ratio compared with those who had a Glasgow Coma Scale score of 5-8 (p < .005). Patients who progressed to brain death had a markedly lower LF/HF ratio (p < .001), with a significant decrease after the first 4 hrs of hospitalization. Patients with more favorable outcomes had significantly higher LF/HF ratios.
Conclusions:
Our findings suggest that an ICP of >30 mm Hg or a CPP of <40 mm Hg may be associated with marked autonomic dysfunction and poor outcome. We speculate that HRV power spectral analysis may be a useful adjunct in determining the severity of neurologic insult and the prognosis for recovery in children. The LF/HF ratio may be helpful not only in identifying those patients who will progress to brain death but also in predicting which patients will have favorable outcomes.