# Can a Sacrococcygeal Epidural of 0.25% Bupivacaine Prevent the Activation of the Sympathetic Nervous System during Feline Ovariectomy?

## TL;DR

This study tested if a low-dose bupivacaine epidural can block the stress response in cats during ovariectomy surgery.

## Contribution

The study introduces a novel approach using sacrococcygeal epidural anesthesia to reduce sympathetic activation in feline ovariectomy.

## Key findings

- Sacrococcygeal epidural reduced hemodynamic variable increases during surgery.
- Sympathetic nervous system activation was not fully prevented by the epidural.
- Heart rate variability monitoring detected sympathetic activation despite epidural use.

## Abstract

This study aimed to assess the efficacy of a sacrococcygeal epidural (ScE) of 0.25% bupivacaine in preventing sympathetic nervous system activation on feline ovariectomy. During the intraoperative period, traditional hemodynamic variables (heart rate, systolic and median blood pressure, and respiratory rate) and Parasympathetic Tone Activity monitoring were used to assess the activation of the sympathetic nervous system after ScE of 0.25% bupivacaine. This study indicates that implementation of ScE reduces the rise of common hemodynamic variables but does not prevent sympathetic nervous system activation during feline ovariectomy.

The ovariectomy (OVE) procedure can trigger somatosensory and visceral peritoneal nociception. Sacrococcygeal epidural (ScE) anesthesia may complement or replace systemic analgesia used for feline OVE, reducing opioid consumption and their related undesirable adverse effects and consequently reducing or completely blocking the sympathetic nervous system activation during this procedure. The present study aimed to evaluate the activation of the sympathetic nervous system resulting from adding an ScE injection of bupivacaine 0.25% (0.3 mL kg−1) in feline OVE and identify whether this translates to hemodynamic variables stability. A Parasympathetic Tone Activity (PTA) monitor was applied given that it performs analysis of heart rate variability (HRV) detecting changes in sympathetic and parasympathetic tone, making it a good tool for detecting activation of the sympathetic nervous system during the study. Two groups of animals were evaluated in five perioperative times, namely, the control group (CG) (n = 18) with systemic analgesia alone and the sacrococcygeal epidural group (ScEG) (n = 20) with 0.25% bupivacaine combined with systemic analgesia. Thirty-eight female cats were selected. All animals assigned to CG and ScEG were premedicated with dexmedetomidine (20 μg kg−1 IM) and methadone (0.2 mg kg−1 IM). General anesthesia was induced with propofol IV ad effectum and maintained with isoflurane in 100% oxygen. Heart rate, non-invasive systolic and median blood pressure, respiratory rate, and instantaneous parasympathetic tone activity were recorded. Compared to systemic analgesia alone (CG), sacrococcygeal epidural (ScEG) reduced the rise of common hemodynamic variables but did not prevent sympathetic nervous system activation.