Avaliação comparativa da eficácia analgésica transoperatória do bloqueio do plano transverso do abdômen com lidocaína isolada ou associada a dexmedetomidina em cadelas submetidas a ovariohisterectomia

Abstract

Ovariohysterectomy (OH) is a sterilization procedure frequently performed in veterinary medicine that causes moderate to severe pain. The objective was to compare the intraoperative analgesic efficacy of the transverse abdominal plane block (TAP Block) with lidocaine alone or combined with dexmedetomidine in female dogs undergoing elective ovariohysterectomy. Sixteen female dogs were included and randomly assigned in a blinded study to two groups (n=8): the lidocaine group (GL), receiving 1% lidocaine at 0.2 ml/kg, and the lidocaine plus dexmedetomidine group (GDEX), with the addition of 1 µg/ml dexmedetomidine. During the preoperative assessment (Baseline), heart rate (HR) (bpm), respiratory rate (RR) (bpm), temperature (°C), systolic blood pressure (SBP) (mmHg), mucosal coloration, and capillary refill time (CRT) (sec) were evaluated. Dogs were premedicated with 0.03 mg/kg acepromazine and 3 mg/kg meperidine (IM). After 15 minutes, induction was performed with propofol at a dose sufficient for intubation. Subsequently, the animals were intubated and connected to the circular valve circuit with isoflurane in sufficient quantity to maintain them in plane 3 and stage II or III, according to Guedel. TAP Block was performed at two sites (subcostal and umbilical approaches). The variables evaluated were T (°C), f (bpm), HR (bpm), SBP, DBP, and MAP (mmHg), SpO₂ (%), and ETCO₂ (mmHg). Time points were: M1 (immediately after TAP block and 10 minutes after induction), M2 (surgical incision), M3 (ligation of the right pedicle), M4 (ligation of the left pedicle), M5 (ligation of the cervix), and M6 (muscle closure). Rescue analgesia with fentanyl 2 mcg/kg IV was administered when there was a 20% increase in HR, respiratory rate, and BP. Dipyrone 25 mg/kg and meloxicam 0.2 mg/kg (SC) were administered in the immediate postoperative period. Extubation time, sternal decubitus, and standing time were evaluated. Statistical analysis used mixed-effects or generalized linear models for continuous variables, and Pearson’s chi-square (χ²) for categorical variables, with significance at p<0.05. For HR, in the GDEX group, the baseline mean was higher than at other time points (p<0.001). In the same group, for f, the baseline mean was higher than M4 and M5 (p<0.002). For SBP, the baseline mean in GL and GDEX was higher than at the other time points (p<0.001). For DBP in GDEX, M1 was higher than M3 (p=0.028) and M4 (p=0.020). For MAP in GDEX, M1 was higher than M4 (p=0.049). It is concluded that adding dexmedetomidine to lidocaine in the TAP Block for ovariohysterectomy in dogs does not provide better analgesia compared with lidocaine alone.