Cardiovascular Effects of Three Distinct Anesthetic Approaches in Rats

Abstract

It is well known that anesthesia affects hemodynamics and leads to marked changes in neurohumoral modulation of the cardiovascular system, affecting results obtained in research protocols conducted during anesthesia. We evaluated the effect of three distinct anesthetic agents on arterial pressure (AP), heart rate (HR), and their variability indexes before and during anesthesia in rats. Conscious freely moving Wistar rats, previously instrumented with catheters in the femoral artery, had their AP recorded during 30 min. Following they were anesthetized with ketamine/xylazine (KX: 50/10 mg/kg, ip, N=7), urethane (URE: 1 g/kg, ip, N=7) or inhalation of isoflurane (ISO: 3–5%, N=10) and the AP recording was maintained for the next 30 min. At the onset of anesthesia with KX, the animals showed a marked rise in AP (D 47±2 mmHg) that slowly returned to normal values within 30 min. URE did not affect AP, while ISO caused a pressure drop of 16±1 mmHg. Overall blood pressure variability, measured by the standard deviation of systolic pressure values, was reduced during anesthesia with KX (D ‐ 1.9±0.5 mmHg) or URE (D −2.3±0.3 mmHg) but was not affected by inhalation of ISO. Likewise, the power of systolic AP spectra, an index of sympathetic vascular modulation, was markedly decreased by anesthesia with KX or URE (D −6.6±1.3 and −4.7±0.6 mmHg2, respectively) but not with ISO. Bradycardia (D −64±10 bpm) and an increase in HR (D 85±12 bpm) were caused by anesthesia with KX and URE, respectively. Inhalation of ISO had no effect on HR. Overall HR variability, measured by the standard deviation of normal cardiac intervals (SDNN), was markedly reduced by all anesthetic agents studied (D −1.1 to −2.0 ms for the three agents used). Spectral analysis showed that low‐frequency power of pulse interval (PI) spectra was decreased during anesthesia with KX (D −10±1 nu) or URE (D −11±3 nu). At the same time, it was not affected by the inhalation of ISO. The high‐frequency power of PI spectra was found reduced during anesthesia with the tree agents used (D −7.7 to −3.1 ms2). Multiscale entropy, an index of complexity of HR variability, showed that anesthesia with KX or URE, but not with ISO, decreased HR complexity at lower scales (1–6). At higher scales (7–20) entropy was markedly decreased by the three anesthetic agents studied. Our results revealed that, despite its hemodynamical effects, anesthesia decreases cardiovascular modulation. However, the inhalation of ISO is the anesthetic approach that preserves the most the characteristics of AP and HR variability, suggesting that this is the anesthesia that has less effect on cardiac and vascular modulation.Support or Funding InformationSupported by FAPESP and CNPq