Effect of adding vasopressin on the distribution of lidocaine in tissues, anesthetic action, and circulatory dynamics.

We examined whether vasopressin affects the distribution, anesthesia duration, and circulatory dynamics of lidocaine. Blood flow was measured after injecting 0.003, 0.03, or 0.3 U/mL vasopressin and 2% lidocaine (L) to the upper lip of rats. Radioactivity and distribution of C-labeled L (CL) in the palate, palatal mucosa, maxilla bone, and blood was measured by autoradiography after injecting CL and CL + 0.03 U/mL vasopressin. To evaluate anesthesia duration, somatosensory-evoked potentials, blood pressure, and pulse rate were measured after L, 0.03 U/mL vasopressin, and L + 0.03 U/mL vasopressin injection to the palatal mucosa. Blood flow from 10 to 60 min was significantly lower with 0.03 U/mL vasopressin and L + 0.03 U/mL vasopressin than with L. Radioactivity in the palatal mucosa and maxilla bone was significantly higher at 5-60 min and 2-60 min with CL + 0.03 U/mL vasopressin than with CL. Blood radioactivity reached the maximum at 0.5 and 50 min with CL and CL + 0.03 U/mL vasopressin, respectively. Autoradiogram showed higher distribution with CL + 0.03 U/mL vasopressin than CL. Peak-to-peak amplitude 30-60 min was significantly lower with L + 0.03 U/mL vasopressin than with L. Lidocaine did not affect blood pressure and pulse rate with 0.03 U/mL vasopressin-only or combined with 2%-lidocaine. Topical 0.03 U/mL vasopressin injection reduced the tissue blood flow, promoted the localization and retention, and extended the anesthesia duration of lidocaine, leaving circulatory dynamics unaffected.