Lidocaine with vasoconstrictor isolated and its combination with epidural fentanyl anesthesia in dogs

The objective of this blind study was to investigate the cardiopulmonary and analgesic effects of different doses of fentanyl combined with lidocaine by epidural route in dogs. Twenty-eight dogs were distributed in four treatments: 5 mg kg(-1) of lidocaine with vasoconstrictor alone (L) and in combination with 2.5, 5 e 7mg kg(-1) of fentanyl (F2.5, F5 e F7). The preanaesthetic medication was intravenous acepromazine (0.05 mg kg(-1)). An intravenous bolus of fentanyl (2.5 mg kg(-1)) was administered immediately before epidural injection. Heart and respiratory rates, electrocardiography, systolic arterial blood pressure, rectal temperature, arterial blood gases, onset time, duration of anesthesia and sensitive block level were investigated. There was decrease of heart rate after epidural injection when compared with the baseline values in F2.5, F5 and F7 treatments. Heart rate was higher in L when compared with F5 and F7 at 30 and 60 minutes after epidural anesthesia. Onset time was not statically different among the treatments. Duration of anesthesia was longer in F5 when compared with the other treatments. Sensitive block until the sixth lumbar vertebra occurred in four dogs in L. Sensitive block until the first lumbar vertebra occurred in five dogs in F2.5 and F7 and in six dogs in F5. In conclusion, the addition of fentanyl to lidocaine in epidural anesthesia allowed cranial sensory block in relation to the isolated use of lidocaine. The addition of fentanyl (5 mg kg(-1)) to lidocaine prolonged the anesthetic blockade when compared with others treatments.