Baroreflex sensitivity during intestinal ischemia (1169.6)

Abstract

Autonomic control of heart rate (HR) during prolonged intestinal ischemia was investigated by mathematical analysis of cardiac baroreflex. 24 Wistar rats underwent splanchnic arterial occlusion (SAO) under anesthesia and received different treatments, which included enteral saline or glucose, intramuscular xylazine and i.v. glycopyrrolate. High fidelity continuous arterial blood pressure (ABP) was measured by a catheter placed in the femoral artery. Time series of systolic blood pressure (SBP) and heart period (HP) were derived from the continuous ABP. Baroreflex gain (from SBP to HP) was calculated both in the low frequency (LF, 0.25‐0.75 Hz) and high frequency (HF, 0.75‐2.5 Hz) spectral bands. After a variable delay, ABP began to steadily decrease until either sacrifice at 4 hours after SAO or collapse by a sudden, fast fatal drop (FFD) of ABP. FFD was prevented by treatment with glycopyrrolate. Rats who displayed the FFD had a higher LF gain in the period (~ 5 mins) preceding the FFD with respect to the post‐SAO period (0.22 ± 0.11 ms/mmHg vs. 0.36 ± 0.15 ms/mmHg, p‐value < 0.05). These preliminary results suggest a sympathetic hyperactivation in the FFD rats and hint that the sympathetic system reaches saturation before the FFD, with the possibility of a sudden shift of the sympatho‐vagal balance towards a parasympathetic driven control of HR. Grant Funding Source: Supported by the ShockOmics project of the European Union (Grant#602706)