Introduction

Epidural anesthesia, when compared to general anesthesia, presents some advantages like reducing costs and minimizing risks for anesthetics due to causing fewer respiratory and cardiovascular disorders. It's been used primarily for surgeries of pelvic limbs and inguinal region, since it is a local anesthetic. When administered in the space between the seventh lumbar vertebra and the first sacral vertebra, it provides maximum lock up the fourth lumbar vertebra. An alternative to more cranial blockages is to use an epidural catheter. This study aimed to evaluate the comparative hemogasometric effects of two doses of lidocaine administered via epidural at the first lumbar vertebra level in bitches laid under ovariohysterectomy. As methodology, we used 16 mongrel dogs weighing between 4 and 20 kg and aged between 1 and 6 years. All received butorphanol and etomidate, both intravenously in doses of 0.4 mg/kg and 2 mg/kg, respectively. Then, at the first lumbar vertebra level and with the aid of an epidural catheter, 4 or 6 mg/kg lidocaine was deposited. Blood was collected for determination of gas parameters (PaCO₂, PvCO₂, pH, SaO₂, SvO₂ HCO₃-, BE) prior to administration of butorphanol, 10 minutes after opioid administration, and every 10 minutes after the deposition of lidocaine in epidural space up to a total of 60 minutes after drug administration. The results showed no statistically significant differences between the two groups in any of the times. However, it's concluded that two doses of lidocaine, deposited at the first lumbar vertebra level, do not interfere with blood gas parameters.