Step baroreflex response in awake patients undergoing carotid surgery: time- and frequency-domain analysis

Author:

Landesberg Giora1,Adam Dan2,Berlatzky Yacov3,Akselrod Solange4

Affiliation:

1. Departments of Anesthesiology and Critical Care Medicine and

2. Department of Biomedical Engineering, The Technion-Institute of Technology, Haifa 32000; and

3. Vascular Surgery and Transplantation, Hebrew University-Hadassah Hospital, Jerusalem 91120;

4. Department of Medical Physics, Tel-Aviv University, Tel-Aviv 69978, Israel

Abstract

Step baroreceptor stimulation can provide an insight into the baroreflex control mechanism, yet this has never been done in humans. During carotid surgery under regional anesthesia, a step increase in baroreceptor stimulation occurs at carotid declamping immediately after removal of the intra-arterial atheromatous plaque. In 10 patients, the R-R interval and systolic and diastolic blood pressures (BP) were continuously recorded, and signals obtained within the time window from 10 min before until 10 min after carotid declamping were analyzed. Mean ± SD time signals, power spectra, and transfer and coherence functions before and after declamping were calculated. Immediately after carotid declamping, both heart rate (HR) and BP declined in an exponential-like manner lasting 10.3 ± 5.9 min, and their power spectra increased in the entire frequency range. Transfer function magnitude and coherence functions between BP and HR increased predominantly in the midfrequency region (∼0.1 Hz), with no change in phase function. Thus, in carotid endarterectomy patients, step increase in baroreceptor gain elicits a prolonged decline in HR and BP. Frequency analyses support the notion that the baroreflex control mechanism generates the midfrequency HR and BP variability, although other frequency regions are also affected.

Publisher

American Physiological Society

Subject

Physiology (medical),Cardiology and Cardiovascular Medicine,Physiology

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