Serum lidocaine concentration after epidural administration in dogs

The pharmacokinetics of lidocaine deals with the measurement of lidocaine concentration in the blood and its changes over time. The toxicity of lidocaine is a function of its peak plasma concentration, which in turn depends on several factors including total dose and rates of systemic absorption and elimination. The aim of the study was to assess serum levels of lidocaine after a single shot epidural injection in dogs seen in daily practice. The study included nine dogs undergoing different types of surgery. The animals were anesthetized with a combination of diazepam and ketamine; then lidocaine was injected epidurally. Blood samples for measurement of serum lidocaine concentration were obtained before and at 10, 30, 60 and 120 min after single injection. Basic vital parameters of heart rate, respiratory rate, mean arterial pressure and hemoglobin saturation were recorded before induction of general anesthesia (T-1), immediately after intubation (T-2), and then at 10, 30, 60 and 120 min of epidural lidocaine administration. Study results indicated that serum lidocaine concentration did not reach the levels of potential toxicity in dogs upon epidural injection of 4 mg/kg lidocaine at a concentration of 2% and there were no significant alterations in basic vital parameters.