To evaluate the isoflurane-sparing effect and the intra- and postoperative analgesic efficacy of an ultrasound-guided transversus abdominis plane (TAP) block in pigs undergoing elective laparoscopic ovariectomy. Prospective, randomised, blinded clinical study A total of 35 female pigs. Pigs were randomly allocated to TAP or control groups. Premedication consisted of azaperone 1 mg kg -1 , xylazine 1.5 mg kg -1 , butorphanol 0.2 mg kg -1 and ketamine 5 mg kg -1 intramuscularly. Anaesthesia was induced with ketamine ± thiopental intravenously and maintained with isoflurane. A three-injection-point per hemiabdomen ultrasound-guided TAP block was performed with 1 % lidocaine, 0.1 mL kg -1 per point. No sham injection was performed in controls. Baseline heart rate (HR) and mean arterial pressure (MAP) were recorded before surgery at 1.0% end-tidal isoflurane (FE´Iso). Anaesthetic requirements were adjusted by a blinded investigator if HR and MAP deviated 20% from baseline. Ketamine 1 mg kg -1 was administered for ventilator asynchrony. Postoperative pain was assessed using the UNESP-Botucatu pig composite acute pain scale. Pigs scoring ≥ 6 / 18 were given oral paracetamol 30 mg kg -1 . Statistical significance was set at p < 0.05. After excluding nine pigs,12 were analysed in the TAP group and 14 in the control group. No statistically significant difference was found comparing overall isoflurane requirements (mean ± standard deviation FE´Iso area-under-the-curve: 7.12 ± 0.89 versus 7.19 ± 1.04 in TAP and control groups, respectively p = 0.775). Median postoperative pain scores (interquartile range) were 1 (1–4) in the TAP group and 1 (0–2) in controls. No significant differences were found in rescue analgesia requirements intra- ( p = 0.759) or postoperatively ( p = 0.867). Ultrasound-guided TAP block is a feasible technique in pigs . With the methodology used, no isoflurane-sparing effect of the TAP block was detected.
Cipollini et al. (Sun,) studied this question.