Epidural anesthesia with lidocaine alone or combinated with clonidine: cardiopulmonary and analgesic effects in dogs/ Anestesia peridural com lidocaina isolada ou associada a clonidina: efeito cardiorrespiratorio e analgesico em caes

Satisfactory analgesia has been related with epidural [[alpha].sub.2] adrenoceptor agonists in combination with local anesthetics. The aim of this study was to compare the analgesic and cardiopulmonary effects of lidocaine or lidocaine-clonidine epidural injections in healthy dogs. Dogs were randomly assigned to two groups of six animals each. The L group received lidocaine (5mg [kg.sup.-1] L) and the C group lidocaine plus clonidine (10 [micro]g [kg.sup.-1] C). Preanaesthetic medication was carried out with acepromazine (0.05mg [kg.sup.-1] IV). Anaesthesia was induced and maintained with isoflurane by facial mask for epidural injection. Heart rate (HH), electrocardiography (ECG), respiratory rate (RR), systolic arterial blood pressure (SAP), rectal temperature (RT), blood gases, duration of anesthesia and sensitive block level were investigated. Statistical analysis was performed with ANOVA, Tukey test and paired t test. There was a decrease of HR at 15, 30 and 45 minutes after epidural injection in C group when compared with L group. Cardiac dysrhythmias did not observe in both treatments. The variables, SAP, RR, RT and blood gases did not differ between treatments. Duration of anesthesia was 71 [+ or -] 13 and 75 [+ or -] 26 minutes to L and C treatment, respectively, without difference between groups. The maximal extension of sensitive block was the fourth lumbar vertebra and the tenth thoracic vertebra in L and C treatment, respectively. In conclusion, the addition of clonidine to lidocaine in epidural anesthesia allowed more cranial sensory block in relation to the isolated use of local anesthetic, however, it produced bradycardia and did not prolong the duration of anesthesia.