Comparison of the Effects of Maropitant, Lidocaine, and Dextroketamine Administered by the Intratesticular Route in Dogs Undergoing Elective Orchiectomy

Abstract

Background: Balanced anesthesia achieved with combinations of inhaled and injectable drugs administered systemically or in loco-regional anesthetic blocks, is widely used in veterinary medicine. The use of anesthesia and/or local analgesia has already demonstrated benefits in the performance of elective orchiectomy in different species, there is no literature that evaluates the use of the maropitant intratesticular route. The present study evaluated the cardiorespiratory variables and analgesia produced by intratesticular blockade with maropitant, lidocaine, or dextroketamine during the trans-operative period along with the discharge and anesthetic recovery of dogs that underwent elective orchiectomy. Materials, Methods & Results: Used twenty-four dogs from routine elective orchiectomy, considered healthy based on the results of clinical and hematological tests. The animals were randomly divided into three groups and was applied intratesticularly 2% lidocaine at a dose of 1 mg/kg (GL), 5% dextrocetamina at a dose of 2.5 mg/kg (GC), or 1% maropitant  at a dose of 1 mg/kg (GM). Anesthesia induction was performed with propofol (to effect), and stabilization of inhalational anesthesia was achieved with 1.7 V% of sevoflurane diluted in 100% oxygen administered through a calibrated vaporizer and appropriate anesthetic system based on the animal's weight, being kept under spontaneous ventilation, After induction, we waited 10 min for stabilization of exhaled anesthetic concentration and then administered one of the treatments intratesticularly. After five min from the local block the surgical procedure was started during up to 15 min. Heart rate (HR), respiratory rate (RR), systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP), oxygen saturation of hemoglobin (SatO2), end-tidal carbon dioxide partial pressure (EtCO2), end-tidal sevoflurane concentration (EtSevo) in exhaled air, and body temperature (T°C) were measured before intratesticular administration of the agent and at specific time points during surgery, in addition to assessments of analgesia and evaluation of discharge and anesthetic recovery. Statistical analysis was performed using the Kolmogorov-Smirnov test (P > 0.10). The parameters HR, RR, SAP, DAP, MAP, T, EtCO2, and SatO2 were evaluated by analysis of variance (ANOVA), followed by the Scott-Knott test (Software R® 3.2.0 - 2013), considering a significance level of P < 0.05. The results did not show inter-drug differences for the evaluated variables.Discussion: It was decided not to use premedication (MPA), so that we could accurately assess the analgesic effect of drugs, lidocaine, dextroketamine and maropitant, on intratesticular block during elective orchiectomy. In this study we demonstrated that these drugs promoted analgesia, because the trans-surgical values were relatively lower compared to baseline and within physiological limits for the species. In addition, it was noted that local analgesia used was efficient since even at the time of ligature and the incision spermatic cord which is described in the literature as the most painful part of the surgical procedure. The post-anesthetic recovery and discharge were quick in the absence of MPA, local analgesia without residual effects and the use of sevoflurane. The sevoflurane has a very low blood gas coefficient solubility, resulting in a recovery fast. Therefore, we can conclude that all of the drugs promoted analgesia and cardiorespiratory stability as well as rapid anesthetic recovery for elective orchiectomy in this species.