Key result
Depressed heart rate variability and baroreflex sensitivity are linked to mortality in neurosurgical ICU patients.
Why the study?
Patients with brain damage exhibit changes in heart rate and cardiovascular control, and the relationship of these autonomic changes in critically ill neurosurgical patients to subsequent survival and quality of outcome needed to be defined.
Do changes in autonomic cardiovascular control (R-R interval variability and baroreflex sensitivity) predict the quality of subsequent outcome and survival in critically ill neurosurgical patients?
Cohort (n=29)
No
Do changes in autonomic cardiovascular control (R-R interval variability and baroreflex sensitivity) predict the quality of subsequent outcome and survival in critically ill neurosurgical patients?
Reduced R-R interval total power variability, lowered LF/HF ratio, and reduced arterial baroreflex sensitivity are associated with poor recovery or death in critically ill neurosurgical patients.
Answers are grounded in this paper and cite their sources.
Supports autonomic markers for mortality risk in neurosurgical ICU patients; leaves open prospective validation before clinical use.
Objective Patients with brain damage exhibit a number of changes in heart rate and cardiovascular control. The aim of this study was to relate changes in autonomic cardiovascular control seen in critically ill neurosurgical patients to the quality of subsequent outcome and survival. Design Prospective, longitudinal, outcome study. Setting Intensive care department of a university teaching hospital. Patients A total of 29 consecutive neurosurgical patients admitted for > or =2 days to the intensive care department with a Glasgow Coma Scale score < 13 who needed electrocardiographic and invasive arterial monitoring. Interventions Sampling of the electrocardiogram, respiratory rate, and arterial pressure into a personal computer was carried out for > or =60 mins. Power spectral analysis was then applied to the data by using a fast Fourier transformation. Arterial baroreflex sensitivity was determined as the gain of the transfer function between systolic arterial blood pressure and electrocardiograph R-R interval (RRI) variability. All surviving patients were followed up at 3 months postadmission to measure quality of outcome. Measurements and main results There were reductions in the total power (p < .01) of RRI variability in those who subsequently died compared with those who survived. This was significant for very low frequency (p < .001) and low-frequency (LF) (p < .05) but not high-frequency (HF) bands (p = .11). Blood pressure variability, however, did not change between groups. Baroreflex sensitivity was 8.7+/-2.2 msecs/mm Hg for patients with a good later outcome and 4.4+/-1.5 msecs/mm Hg for patients who subsequently died (p = .03). Patients who recovered to a good quality outcome also had a raised LF/HF ratio in RRI (p = .05). Conclusion A reduction in the total power variability of RRI and a lowered LF/HF ratio of the RRI are associated with a poor quality recovery or death after neurosurgical illness. A reduction in the baroreflex was specifically associated with death in this patient group.
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Haji-Michael et al. (2000) conducted a cohort in Critically ill neurosurgical illness with brain damage (n=29). Power spectral analysis of cardiovascular variability (R-R interval variability and arterial baroreflex sensitivity) vs. Survivors / patients with a good later outcome vs non-survivors was evaluated on Quality of subsequent outcome and survival at 3 months postadmission (p=<0.01). Reduced R-R interval total power variability (p<.01) and lower baroreflex sensitivity (4.4 vs 8.7 msecs/mm Hg, p=.03) were associated with death in neurosurgical ICU patients.
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