The effect of low dose rocuronium bromide on eyeball position, muscle relaxation, and ventilation in dogs |
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| Authors: | U Auer |
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| Institution: | Anesthesia and Intensive Care, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210 Vienna, Austria |
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| Abstract: | A central eyeball position is often required during sedation or anaesthesia to facilitate examination of the eye. However, use of neuromuscular blockade to produce a central eye position may result in depressed ventilation. This study evaluated the eyeball position, muscle relaxation and changes in ventilation during general anaesthesia after the IV administration of 0.1 mg kg?1 rocuronium. With client consent, 12 dogs of different breeds, body mass 27.2 ± 11.8 kg, aged 5.6 ± 2.8 years (mean ± SD) were anaesthetized for ocular examination. Pre‐anaesthetic medication was 0.01 mg kg?1 medetomidine and 0.2 mg kg?1 butorphanol IV. Anaesthesia was induced with propofol to effect and maintained with 10 mg kg?1 hour?1 propofol by infusion. The dogs were placed in left lateral recumbency, their trachea intubated and connected to a circle breathing system (Fi O2 = 1.0). All dogs breathed spontaneously. The superficial peroneal nerve of the right hind leg was stimulated every 15 seconds with a train‐of‐four (TOF) stimulation pattern and neuromuscular function was assessed with an acceleromyograph (TOF‐Guard). Adequacy of ventilation was measured with the Ventrak 1550. After 10 minutes of anaesthesia to allow stabilisation of baseline values, 0.1 mg kg?1 rocuronium was administered IV. Minute volume (Vm ), tidal volume (Vt ), respiratory rate (RR), Pe ′CO2 and maximal depression of T1 and TOF ratio were measured. Data were analysed using a paired t‐test. The changes in the eyeball position were recorded. A total of 100 ± 33 seconds after the injection of rocuronium, T1 was maximally depressed to 62 ± 21% and the TOF ratio to 42 ± 18% of baseline values. Both variables returned to baseline after 366 ± 132 seconds (T1) and 478 ± 111 seconds (TOF). There was no significant reduction in Vm (2.32 ± 1.1 L minute?1), Vt (124.1 ± 69.3 mL) and RR (10 ± 3.8 breaths minute?1) and no increase in Pe ′CO2 (6.5 ± 2.1 kPa (48.8 ± 16.1 mm Hg)) throughout the procedure. The eyeball rotated to a central position 35 ± 7 seconds after rocuronium IV and remained there for a minimum of 20 ± 7 minutes in all dogs. We conclude that rocuronium at a dose of 0.1 mg kg?1 can be administered to dogs IV with minimal changes in ventilatory variables. The eyeball is fixed in a central position for at least 20 minutes, which greatly facilitates clinical examination. |
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