Preliminary study of the cardiorespiratory effects of fentanyl in halothane anesthetized dogs

Abstract

The purpose of this study was to evaluate selected cardiovascular and respiratory effects of fentanyl administered intravenously to halothane anesthetized dogs. Twelve healthy dogs were anesthetized with halothane, held constant at 1.5 MAC with 2L/min oxygen flow rate up to 40 minutes after treatment was administered. Each dog was given one of 2 treatments: fentanyl (FNT, 25 µg/kg, IV) or isotonic saline (SAL, 0.5 ml/kg). The following values were recorded throughout the study: mean (MAP), systolic (SAP) and diastolic (DAP) arterial blood pressures (mmHg), central venous pressure, (CVP, mmHg), heart rate (HR, beats/minute), oxygen arterial saturation (SaO_2,%), pH, arterial carbon dioxide pressure, (paCO₂, mm Hg), bicarbonate (CO₃H, mmol/l), esophageal temperature (°C), respiratory rate (RR, beats/min). These data were collected at predetermined times before (base line data) and after treatment. Results showed statistically significant differences (P<0.05) for FEN in HR, DAP and MAP when compared with pre-treatment values, and in both groups (FEN and SAL) for temperature. CO₃H and pH decreased significantly and paCO₂ increased when compared with pre-treatment values and with SAL. Apnea was seen in all dogs in FEN. It is concluded that the intravenous administration of FEN did not induce significant alterations in cardiorespiratory parameters in halothane anesthetized dogs, provided mechanical ventilation is instituted and an anticholinergic agent is administered to prevent bradycardia.