Anestesia local por tumescência com lidocaína em gatas submetidas a mastectomia

Abstract

The tumescent anesthesia technique has excelled for ensuring effective analgesia. This technique is capable to decrease the volatile anesthetic application. The aim of this study was to evaluate the tumescent technique using lidocaine in cats submitted to mastectomy, by measuring plasma lidocaine concentrations, and evaluation of analgesia postoperatively. Twelve female cats with mammary tumors were selected without predilection for weight or age. All animals received on pre anesthetic medication, intramuscular pethidine 4 mg.kg-1. After 15 minutes, the surgical site, cephalic and jugular veins were clipped. An intravenous (IV) catheter was introduced into cephalic vein for administration of saline solution. Anesthesia was induced with propofol (5 mg.kg-1) followed by endotracheal intubation and, was maintained with isoflurane. The Klein cannula (2,0 mm x 14 cm) was used to provide dispersion of refrigerated tumescent solution. The tumescent solution was prepared with 210 mL of lactate Ringer’s solution, 0,5 mL of adrenaline and 40 mL of 2% lidocaine, without vasoconstrictor, to achieve a lidocaine concentration of 0,32%. The local anesthetic solution (15 mL.kg-1 at 8ºC) was injected under extension of the target mammary glands. The physiological variables [heart rates (FC), respiratory rates (f), systolic arterial blood pressures (PAS), retal temperature, oximetry (SpO2), capnography (EtCO2)] and anesthetic gases expired were measured, throughout the entire procedure. Blood samples were serially collected for measurement of the plasma lidocaine concentration, through High Performance Liquid Chromatography (HPLC). After the surgical procedure the animals had their pain scores assessed at one-hour intervals through a multidimensional scale during six hours. The anesthetic recovery was performed with tramadol, 2 mg.kg-1 (IM) associated to meloxicam 0,15 mg.kg-1 subcutaneously. The plasmatic peak lidocaine was achieved at 90 minutes after infiltration, and it did not produce toxic levels of plasma lidocaine concentrations. Analgesic rescue was performed at median time of 6 hours after infiltration of the tumescent solution. In conclusion, lidocaine tumescent anesthesia is effective to promote satisfactory intraoperative and postoperative analgesia, and is safe for use in cats without interfering on time to stiches removal.