Comparison of caudal epidural anesthesia by use of lidocaine versus a lidocaine–magnesium sulfate combination in cattle

OBJECTIVE: To compare time of onset and duration of analgesia obtained by epidural administration of a lidocaine-magnesium sulfate (MgSO4) combination versus a lidocaine-distilled water combination in cattle. ANIMALS: 5 healthy adult (mean +/- SD age, 4.6 +/- 0.5 years) Holstein cows (body weight, 480.0 +/- 71 kg). PROCEDURES: Caudal epidural anesthesia was obtained in all cows with 2% lidocaine (0.22 mg/kg) solution and 1 mL of distilled water, and 2 weeks later, anesthesia was repeated with 2% lidocaine (0.22 mg/kg) solution and 1 mL of 10% MgSO4 solution. Time to onset, duration, and cranial spread of analgesia were recorded. Heart rate, respiratory rate, and body temperature were recorded at minute 0 prior to epidural administrations of each treatment (baseline) and at 5, 10, 15, 30, 60, and 75 minutes after epidural administration of each treatment. RESULTS: Onset of analgesia was significantly different following epidural administration of lidocaine-distilled water (mean +/- SD, 2.82 +/- 0.33 minutes) versus lidocaine-MgSO4 (4.76 +/- 0.59 minutes). Epidural administration of lidocaine-MgSO4 produced analgesia of significantly longer duration (168 +/- 2.6 minutes) than that of lidocaine-distilled water (59.8 +/- 3.4 minutes). No significant differences were observed in heart rate, respiratory rate, and body temperature, compared with baseline values, for lidocaine-distilled water or lidocaine-MgSO4 treatments. CONCLUSIONS AND CLINICAL RELEVANCE: The combination of lidocaine with MgSO4 produced analgesia of longer duration than lidocaine with distilled water. By use of this combination, long-duration obstetric and surgical procedures could commence relatively soon after epidural injection and could be completed without readministration of anesthetic.