Ringer laktat l sung

Throughout the surgical study, normotension (MAP 61–119 mmHg) was achieved by infusion of Lactated Ringer’s solution (5–10 mL/kg/h; Ringer-Laktat-Lösung, B. Braun Melsungen, Germany) and dobutamine (0.3–1.2 µg/kg/min; Dobutamine-ratiopharm, Ratiopharm, Ulm, Germany). The duration of the surgical study was approximately 210 min. After the termination of the surgical trial, the manipulation of blood pressure was initiated, allowing a short stabilisation period of 5 min at each range. To achieve hypotension (MAP ≤ 60 mmHg), inspiratory isoflurane concentration was increased, while infusions (crystalloids and dobutamine) were discontinued. Hypertension (MAP ≥ 120 mmHg) was induced by decreasing inspiratory isoflurane concentration and resuming blood pressure support by crystalloid infusions and dobutamine (2.7–3.0 µg/kg/min). To further increase blood pressure, additional norepinephrine (0.15–0.9 µg/kg/min; Arterenol, Sanofi Aventis, Frankfurt, Germany) was administered.

After premedication with either 0.5 mg/kg xylazine (Xylavet®, CP-Pharma, Burgdorf, Germany, IV) or 3.5 μg/kg dexmedetomidine (Dexdomitor®, Zoetis, Berlin, Germany) all horses were anaesthetized with 0.05 mg/kg midazolam (Midazolam-ratiopharm® 15 mg/3 ml, ratiopharm GmbH, Ulm, Germany) and 2.2 mg/kg ketamine (Narketan®, CP-Pharma, Burgdorf, Germany, IV). Anaesthesia was maintained with isoflurane (Isofluran® CP, CP-Pharma, Burgdorf, Germany) in 100% oxygen in combination with a constant rate infusion of 1 mg/kg/h xylazine or 7 μg/kg/h dexmedetomidine. intravenous fluids (lactated Ringer’s solution, Ringer-Laktat-Lösung®, B. Braun Melsungen AG, Germany) were administered at a rate of 10 ml/kg/h. Following induction of anaesthesia and tracheal intubation, the horses were positioned in dorsal recumbency and ventilated immediately. For ventilation a pressure limited and pressure cycled large animal ventilator (Vet.-Tec. Model LAVC 2000 J.D. Medical Distributing Company Phoenix, Phoenix, AZ, USA) was used. Horses were ventilated using intermittent positive pressure ventilation (IPPV) with peak inspiratory pressure of 25 cm H₂O. Respiratory rate (f_R) was adjusted to maintain PaCO₂ between 40 and 45 mmHg.