Adição de sulfato de magnésio à ropivacaína no bloqueio intraperitoneal para o controle da dor após ovariosalpingohisterectomia em cadelas

Abstract

The aim of this study was to investigate the analgesic efficacy and adverse effects of the intraperitoneal ropivacaine and its combination with magnesium sulfate (MgSO4) in dogs undergoing ovariohysterectomy. Forty-five dogs were sedated with acepromazine (0.05 mg/kg) and pethidine (5 mg/kg). Anesthesia was induced with intravenous (IV) propofol (dose effect) and maintained with isoflurane/O2. In a masked and randomized design, the dogs were randomly distributed into three treatments (n = 15): S = saline solution 0.9% (1.2 mL/kg); R: 0.25% ropivacaine (3 mg/kg); R-Mg: 0.25% ropivacaine (3 mg/kg) combined with MgSO4 (20 mg/kg). The solutions were instilled into the peritoneal space (ovarian pedicles, and uterine cervix). Intraoperatively, fentanyl (2,5 µg/kg, IV) was administered based on cardiovascular parameters. The magnesium plasma concentration was measured before (baseline) and 15, 60, 120 and 240 minutes after IP treatment. Analgesia was assessed for 24 hours post-extubation using an Interactive Visual Analog Scale (IVAS), the short form of the Glasgow Composite Pain Scale (CMPS-SF), and mechanical nociceptive thresholds (MNT). Morphine was administered as rescue analgesia. Data were analyzed using the chi-square test, Tukey test, Kruskal-Wallis test, and Friedman test (P < 0.05). Intraoperatively, the incidence of analgesic supplementation and hypotension were higher in the R-Mg group compared to S group (P = 0.034 e P = 0.018, respectively). The CMPS-SF pain score, MNT and the magnesium plasmatic concentration did not differ between groups. The IVAS pain scores were lower in the R-Mg group at 0.5 (P = 0.004) and 1 (P = 0.003) hour post-extubation when compared with the other groups. The incidence of postoperative analgesic supplementation did not differ between groups (P > 0.05). In conclusion, IP treatment with ropivacaine in combination with MgSO4 decreased intraoperative requirements and the postoperative pain scores (IVAS) in the first hour after ovariohysterectomy in dogs, however was associated with a higher incidence of hypotension.