Dexmedetomidina isolada e associada à morfina como medicação pré-anestésica na anestesia geral em cadelas : efeitos cardiorrespiratórios

Abstract

Ovariohysterectomy is capable of causing moderate pain, requiring adequate transoperative analgesia. Dexmedetomidine is an α 2 -adrenergic receptor agonist capable of providing sedation, muscle relaxation and analgesia. By having action also in the heart can lead to bradycardia. Morphine is an opioid used for mild to severe pain, with analgesia being dose dependent. The objective of this study was to test the analgesic efficiency provided by the use of dexmedetomidine alone and the possibility of analgesic potentialization when it was associated with morphine of patients undergoing general inhalation anesthesia with isoflurane submitted to the elective ovariohysterectomy procedure. Materials, Methods & Results: Twenty female dog between 1 and 6 years of age and weighing between 5 and 15 kg were selected from physical and laboratory tests. Only patients classified as clinically healthy and with hematological values within the normality of the canine species were selected for the elective ovariohysterectomy procedure. These selected patients were randomly divided into two groups, a group with dexmedetomidine application at a dose of 10 μg / kg (GD) intramuscular (IM) and the other with dexmedetomidine also at a dose of 10 μg / kg in combination with morphine in dose of 0.3 mg / kg (GDM) in the same syringe intramuscularly. The physiological parameters: heart rate (HR), respiratory rate (f), body temperature (T), systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) were measured 5 minutes before application of pre-anesthetic medication (MPA), considering the baseline moment and after 30 minutes of MPA application, the same parameters were re-measured. The patient was induced with propofol at the dose effect and intubated with tracheotube adequate for its size, shortly after it was coupled to the inhalation system that provided inhalational anesthetic, with isoflurane, which was diluted in 100% oxygen calculated according to the patient's weight. In the trans anesthesia, the abovementioned parameters plus oxygen saturation of hemoglobin (Sat O2), the value of the carbon dioxide partial pressure at the end of expiration (ETCO2) and isoflurane expired (Iso %) were measured. All these variables were measured 5 minutes and 15 minutes after anesthetic induction, after the beginning the skin incision and the muscle incision, during ligation of the left ovary, ligation of the right ovary, ligation of the uterine body, the celiorraphy and the skin suture. Hemogasometry was used for the analysis of blood pH, bicarbonate (HCO3 - ) and arterial partial pressure of carbon dioxide (PaCO2), was performed prior to the application of MPA, after skin incision and after surgery with blood femoral artery. The surgical procedure lasted a maximum of 45 minutes. The differences were significant between the surgical times of the both groups. There was bradycardia 30 minutes after MPA application, acidemia in the trans anesthetic, without hypotension and hypertension. Discussion: The study demonstrated that both isolated and associated dexmedetomidine conferred good analgesia for the procedure, such as ovariohysterectomy that generates moderate pain, presenting hemodynamic stability, because not cause hipotension or hipertension, despite bradycardia generated by the drug. Acidemia, seen by arterial hemogasometry, occurred during trans anesthesia is indicative of hypoventilation caused by respiratory depression induced by the use of dexmedetomidine.