Avaliação da técnica de anestesia local por tumescência comparada com infusão contínua de fentanil em gatas submetidas à mastectomia

Abstract

The present study aimed to evaluate the tumescence technique with lidocaine for mastectomy in cats and to compare it with continuous infusion of intravenous fentanyl. Twenty cats with breast tumors were selected for the radical unilateral mastectomy procedure. All animals were acclimated for 30 minutes, and then subjected to a physical examination to record baseline values (HR, f and rectal temperature). After trichotomy of the left thoracic limb, venoclysis was performed for fluid therapy with lactated ringer's solution at the rate of 3 mL.kg-1.h-1, the animal was sent to the operating room, where anesthetic induction with propofol (5 mg.kg-1) was performed intravenously (IV) and then orotracheal intubation and anesthetic maintenance with isoflurane. The animals were randomly assigned to two groups of 10 animals. The study was random and covered, composed of three anesthetists, and only the first anesthetist had knowledge of the instituted analgesic technique. The tumescence group (GT) received 15 mL.kg-1 of 0.32% lidocaine tumescent solution infiltrated in the subcutaneous tissue. The fentanyl group (GF) received an initial bolus of 2.5 μg.kg-1 by slow intravenous fentanyl citrate and immediately afterwards, they were kept in continuous infusion at the rate of 10 μg.kg-1.h-1. The physiological variables [heart rate (HR), respiratory rate (f), systolic blood pressure (SBP), rectal temperature, pulse oximetry (SpO2), capnography (EtCO2)] and expired anesthetic gases were assessed throughout the procedure. After the end of the surgical procedure, the animals' pain scores were evaluated at hourly intervals using the multidimensional pain scale proposed by UNESP-Botucatu until the time of analgesic rescue. The analgesic rescue was performed with 0.3 mg.kg-1 of methadone hydrochloride (IM) associated with meloxican at a dose of 0.15 mg.kg-1 by the subcutaneous route (SC). The mean time for analgesic rescue was 4 hours in the GT and 1.5 hours in the FG. We conclude that when compared, the two analgesic techniques were equally effective in decreasing the requirement for inhalation anesthetic and promoting analgesia at the trans-operative moment, however, the tumescence technique with 0.32% lidocaine showed more prolonged postoperative analgesia. The residual analgesia produced by the infusion of fentanyl was not sufficient for the postoperative period in cats submitted to unilateral mastectomy. Additionally, tumescence for promoting the hydrodivulsion effect facilitated the excision of the mammary chain and decreased the trans-operative bleeding, without interfering in the surgical healing.