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Heart rate variability in neurosurgical patients
Insights
Heart rate variability (HRV) monitoring in neurocritical care patients revealed that long-term variability (LTV) is a valuable clinical parameter. Both short-term (STV) and LTV of heart rate improved serial patient evaluation.
Area of Science:
- Neurology
- Cardiology
- Critical Care Medicine
Background:
- Heart rate is not constant but exhibits beat-by-beat changes, termed instantaneous heart rate.
- Instantaneous heart rate patterns reveal heart rate variability (HRV).
- HRV analysis is a non-invasive method to assess autonomic nervous system function.
Purpose of the Study:
- To prospectively evaluate short-term (STV) and long-term (LTV) heart rate variability in neurocritical care patients.
- To compare the utility of STV and LTV with the Glasgow Coma Scale for patient assessment.
- To investigate correlations between HRV, intracranial pressure, and neurological outcomes.
Main Methods:
- Prospective study of 102 patients in a neurosurgical intensive care unit.
- Calculation of instantaneous heart rate from R-R intervals to determine STV and LTV.
- Comparison of HRV parameters with the Glasgow Coma Scale and clinical evaluations.
Main Results:
- Long-term variability (LTV) emerged as the most clinically useful heart rate parameter.
- Both STV and LTV demonstrated improved performance in serial patient evaluations.
- No strong correlation was found between elevated intracranial pressure and decreased heart rate or HRV.
- Morphological classification of HRV patterns did not hold prognostic value across diverse neurological disorders.
Conclusions:
- Heart rate variability, particularly LTV, is a simple yet valuable parameter for monitoring neurocritical care patients.
- Serial evaluation of HRV can aid in assessing patient progress.
- Previous findings on HRV and intracranial pressure may not generalize to all acute neurological conditions.
Abstract:
Cardiac monitors determine heart rate by counting the number of beats in a given time interval. The normal heart, however, does not beat at a constant rate. Instead, there is a continuous change in heart rate on a beat-by-beat basis. This is termed the instantaneous heart rate and it represents the projected rate per minute that the heart would beat if only one R-R interval (the time between sequential R waves) was repeated throughout a 60-second period. Calculation of the instantaneous heart rate for each heart beat (R-R interval) produces a pattern that demonstrates the variability in heart rate. This instantaneous heart rate pattern was prospectively studied in 102 patients admitted to a neurosurgical intensive care unit. Short-term (STV) and long-term (LTV) heart rate variability were compared to the Glasgow coma scale as a method for patient assessment. LTV seems to be the most useful heart rate parameter in the clinical setting, and both STV and LTV performed better in the serial evaluation of patients. Two postulations found in the heart rate literature were not borne out in this study. First, we did not find a strong correlation between elevated intracranial pressure and decreases in heart rate or variability, as previously reported by Lowensohn et al. Second, the morphological classification of heart rate patterns described by Evans in his study of head-injured patients did not carry the same prognostic value when applied to this broad spectrum of patients with a variety of acute neurological disorders. Heart rate and its variability is a simple parameter to monitor.(ABSTRACT TRUNCATED AT 250 WORDS)