Evaluation of the addition of cisatracurium in an anesthetic protocol with short-acting drugs in ASA IV and V canine patients

The reduction of drug doses in anesthesia practice results in a valid and safe protocol leading to better management of animal welfare, particularly in patients with high anesthesiological risk (ASA IV and V). Neuromuscular blockers (NMBs) are important adjuncts to general anesthesia (1-3). Cisatracurium besylate is a nondepolarizing muscle relaxant and could be considered an useful adjuvant to analgesic and anesthetic protocols. The purpose was to investigate whether the use of cisatracurium in association with propofol, remifentanyl and sevofluorane allowed to reduce the dose of drugs making the anesthetic protocol suitable in patients with high anesthesia risk. Ten adult female dogs that met the anesthetic criteria (Group 1), undergoing elective unilateral mastectomy surgery, were evaluated. Subjects received propofol and sevoflurane at variable dosage to induce and maintain anesthesia; analgesia was performed using remifentanyl 0.1 µgkg-1min-1. After three months, the same subjects (Group 2) underwent contralateral mastectomy and received the same anesthetic protocol with the addition of cis-atracurium 0,2 mgkg-1. Postoperative analgesia was provided by intravenously buprenorphine 20 µgkg-1 towards the end of surgery, prior to discontinuing the remifentanil infusion. The effects of muscle relaxant on the dose of sevoflurane and propofol were evaluated. During anaesthesia, heart rate (HR), systolic arterial pressure (SAP), end-tidal CO2 (EtCO2), oxygen saturation (SpO2), halogenate concentration in the inspiratory phase (MAC) and rectal temperature were monitored continuously; the measurements were collected before drug administration (basal values, T0), and at induction time (Ti), at 5 (T5), 10 (T10), 15 (T15), 20 (T20), 30 (T30), and 35 (T35) minutes after drugs injection. In Group I, HR values (median and range) showed significant differences, compared with T0 (94; 86/97), at Ti (111; 99/125; p=0.005), T5 (100; 92/108; p=0.012), T15 (74; 65/83; p=0.005), T20 (73; 66/80; p=0.005) and T25 (70; 64/76; p=0.005). In Group 2, the significant differences of HR values compared with T0 (94; 89/99) were: T5 (103; 92/118; p=0.012), T10 (103, 85/121; p=0.032), T15 (84; 70/98; p=0.028), T20 (84; 70/98; p=0.028), T25 (78; 68/88; p=0.005); T30 (86; 74/99; p=0.018) and T35 (84; 69/99; p=0.018). The comparison of HR values between the two groups showed significant differences at T10, T15, T20 and T25 with p<0.05. Regarding SAP values, Group 1 showed significant differences in all time points than T0 (p=0.005). In Group 2, significant differences were found at Ti ((145; 126/164; p=0.008), T5 (149; 136/162; p=0.012), T20 (127; 112/132 p=0.044), T25 (119; 108/126; p=0.012), T30 (121; 114/127; p=0.012), T35 (121; 114/127; p=0.012) in comparison with T0 (135; 110/158). The comparison of SAP values between the two groups showed significant differences at all data points (p<0.05) except at T0. In Group 1, requirement for intraoperative halogenate varied significantly at all time points compared to T0 with p<0.001, while in Group 2 the percentage of halogenate requirement remained constant during the experimental period, showing no significant differences in all data points. In Group 1, the comparison of EtCO2 values showed no significant differences, while in Group 2 a significant difference with p<0.001 was found. The propofol dosage at the induction phase varied significantly between the two groups, with significantly lower dosages in the cisatracurium-treated group (6.9±1.4mgKg-1 Group 1 vs 2.45±0.9mgkg-1 Group 2, respectively). Estubation time and resumption of station were shorter in Group 2. Subjects treated with cisatracurium showed more stable values of investigated parameters. Its addition determined a clinically relevant reduction in the concentration of propofol and sevofluorane used in dogs, with a good anesthetic and analgesic plan. We recommend the addition of cisatracurium in the anesthetic protocols for canine patients with high anesthesiological risk. During Sevoflurane Or Propofol Anaesthesia In Dogs Clinical Trial Vet Anaesth Analg. 2005;32(4):222-7. [2] Nagahama et al. The Effects Of Propofol, Isoflurane And Sevoflurane On Vecuronium Infusion Rates For Surgical Muscle Relaxation In Dogs. Vet Anaesth Analg. 2006:33(3):169