Comparative analysis of autonomic effects of ketamine-xylazine in normotensive and hypertensive rats

This study aimed to evaluate the effects of the ketamine-xylazine (KX) anesthetic mixture on autonomic and cardiovascular functions in normotensive rats (Wistar) and spontaneously hypertensive rats (SHR), using both spectral and symbolic analyses. Male Wistar (n=22) and SHR (n=28) rats were intramuscularly anesthetized with KX, and their femoral artery and vein were cannulated for pulsatile arterial pressure recording and drug administration. Autonomic function was assessed 24 and 48 h post-surgery through spectral and symbolic analyses of heart rate (HR) and systolic arterial pressure (SAP) variability. KX anesthesia significantly decreased mean arterial pressure (MAP) 24 h post-surgery in both Wistar and SHR rats. Spectral analysis revealed increased sympathetic modulation in the vascular bed of SHR 48 h post-surgery. In Wistar rats, there was a significant reduction in parasympathetic modulation at 48 h, as indicated by root mean square of successive RR interval differences (RMSSD) and high frequency (HF) (nu) indices. Symbolic analysis, however, detected no significant changes in autonomic modulation. These data are consistent with the notion that KX anesthesia significantly impacts autonomic and cardiovascular functions, with differential effects observed between Wistar and SHR rats. Spectral analysis proved more effective than symbolic analysis in detecting these changes. These findings highlight the need for careful consideration of anesthetic effects in experimental research and suggest that optimizing anesthetic protocols could improve clinical outcomes by minimizing adverse autonomic impact.