Cardiovascular effects following epidural injection of romifidine in isoflurane-anaesthetized dogs

Objective To investigate the cardiovascular effects of epidural romifidine in isoflurane-anaesthetized dogs. Study design Prospective, randomized, blinded experiment. Animals A total of six healthy adult female Beagles aged 1.25 ± 0.08 years and weighing 12.46 ± 1.48 (10.25–14.50) kg. Methods Anaesthesia was induced with propofol (6–9 mg kg−1) and maintained with 1.8–1.9% end-tidal isoflurane in oxygen. End-tidal CO2 was kept between 35 and 45 mmHg (4.7–6.0 kPa) using intermittent positive pressure ventilation. Heart rate (HR), arterial blood pressure and cardiac output (CO) were monitored. Cardiac output was determined using a LiDCO monitor and the derived parameters were calculated. After baseline measurements, either 10 μg kg−1 romifidine or saline (total volume 1 mL 4.5 kg−1) was injected into the lumbosacral epidural space. Data were recorded for 1 hour after epidural injection. A minimum of 1 week elapsed between treatments. Results After epidural injection, the overall means (± standard deviation, SD) of HR (95 ± 20 bpm), mean arterial blood pressure (MAP) (81 ± 19 mmHg), CO (1.63 ± 0.66 L minute−1), cardiac index (CI) (2.97 ± 1.1 L minute−1 m−2) and stroke volume index (SI) (1.38 ± 0.21 mL beat−1 kg−1) were significantly lower in the romifidine treatment compared with the overall means in the saline treatment [HR (129 ± 24 bpm), MAP (89 ± 17 mmHg), CO (3.35 ± 0.86 L minute−1), CI (6.17 ± 1.4 L minute−1 m−2) and SI (2.21 ± 0.21 mL beat−1 kg−1)]. The overall mean of systemic vascular resistance index (SVRI) (7202 ± 2656 dynes seconds cm−5 m−2) after epidural romifidine injection was significantly higher than the overall mean of SVRI (3315 ± 1167 dynes seconds cm−5 m−2) after epidural saline injection. Conclusion Epidural romifidine in isoflurane-anaesthetized dogs caused significant cardiovascular effects similar to those reportedly produced by systemic romifidine administration. Clinical relevance Similar cardiovascular monitoring is required after epidural and systemically administered romifidine. Further studies are required to evaluate the analgesic effects of epidural romifidine.