Calves were randomly assigned to receive either RSB or a sham injection by means of a random number generator (www.randomizer.org ). Calves in the RSB group received a rectus sheath injection with 0.3 ml/kg 0.25% bupivacaine HCl (Bupivacaina Recordati; Recordati S.p.A., Italy) containing dexmedetomidine HCl (1 μg/ml; Dexdomitor 0.5 mg/ml; Zoetis Inc., United States) as an adjuvant to prolong the effect of the local anesthetic, as previously described (28 (link), 29 (link)). Calves in the control group received a rectus sheath injection with an equivalent volume of sterile saline (0.9% NaCl). All injections were administered by the same operator (FM).
A 14-gauge catheter (Introcan Safety; BBraun Milano S.p.A., Italy) was aseptically placed in one of the jugular veins. Calves were allowed to rest in a quiet room for 120 min prior to induction of anesthesia. All procedures were performed in a dedicated clean area outside the barn. The area was protected from direct sun and well-ventilated. After premedication with an intravenous (IV) injection of 0.02–0.05 mg/kg xylazine (Nerfasin 100 mg/ml; Ati S.r.l., Italy) and 0.02 mg/kg butorphanol (Alvegesic 10 mg/ml; Dechra Veterinary Products S.r.l., Italy), anesthesia was induced with 2.5 mg/kg IV ketamine (Lobotor 100 mg/ml; ACME S.r.l., Italy). All calves were positioned in dorsal recumbency, raised from the ground, and laterally content by straw bales, with legs secured far from the surgical field and with the head elevated and the tip of the nose down to avoid aspiration. Intraoperative monitoring included heart rate (HR) determined by auscultation with a stethoscope, respiratory rate (fR) calculated by direct observation of the thoracic excursions, arterial hemoglobin saturation of oxygen (SpO2) measured with a portable pulse oximeter (CMS-50D1 Fingertip Pulse Oximeter; AccuMed, TX, United States), and rectal temperature. Data were continuously monitored and recorded every 5 min throughout the procedure. At baseline, skin incision, and at the end of surgery, a venous blood sample was collected in a heparinized syringe and analyzed immediately using an automated bench-top blood-gas analyzer (iSTAT 1 Analyser; VetScan, United States) for monitoring ventilation and electrolyte status.
If the calf responded to surgical stimulation with gross movement, spontaneous blinking, nystagmus, or increased jaw tone, additional boluses of IV ketamine (0.5 mg/kg) and/or xylazine (0.01 mg/kg) were administered. At the end of the surgical procedure, 1.1 mg/kg of flunixin meglumine (Alivios; Fatro S.p.A., Italy) was administered IV, and calves were positioned in sternal recumbency, with the neck extended forward for recovery. The time elapsed between the end of the surgery and the animal being able to hold sternal position without support (time-to-sternal) and the time from sternal recumbency to stand (time-to-stand) were recorded.
A 14-gauge catheter (Introcan Safety; BBraun Milano S.p.A., Italy) was aseptically placed in one of the jugular veins. Calves were allowed to rest in a quiet room for 120 min prior to induction of anesthesia. All procedures were performed in a dedicated clean area outside the barn. The area was protected from direct sun and well-ventilated. After premedication with an intravenous (IV) injection of 0.02–0.05 mg/kg xylazine (Nerfasin 100 mg/ml; Ati S.r.l., Italy) and 0.02 mg/kg butorphanol (Alvegesic 10 mg/ml; Dechra Veterinary Products S.r.l., Italy), anesthesia was induced with 2.5 mg/kg IV ketamine (Lobotor 100 mg/ml; ACME S.r.l., Italy). All calves were positioned in dorsal recumbency, raised from the ground, and laterally content by straw bales, with legs secured far from the surgical field and with the head elevated and the tip of the nose down to avoid aspiration. Intraoperative monitoring included heart rate (HR) determined by auscultation with a stethoscope, respiratory rate (fR) calculated by direct observation of the thoracic excursions, arterial hemoglobin saturation of oxygen (SpO2) measured with a portable pulse oximeter (CMS-50D1 Fingertip Pulse Oximeter; AccuMed, TX, United States), and rectal temperature. Data were continuously monitored and recorded every 5 min throughout the procedure. At baseline, skin incision, and at the end of surgery, a venous blood sample was collected in a heparinized syringe and analyzed immediately using an automated bench-top blood-gas analyzer (iSTAT 1 Analyser; VetScan, United States) for monitoring ventilation and electrolyte status.
If the calf responded to surgical stimulation with gross movement, spontaneous blinking, nystagmus, or increased jaw tone, additional boluses of IV ketamine (0.5 mg/kg) and/or xylazine (0.01 mg/kg) were administered. At the end of the surgical procedure, 1.1 mg/kg of flunixin meglumine (Alivios; Fatro S.p.A., Italy) was administered IV, and calves were positioned in sternal recumbency, with the neck extended forward for recovery. The time elapsed between the end of the surgery and the animal being able to hold sternal position without support (time-to-sternal) and the time from sternal recumbency to stand (time-to-stand) were recorded.
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