Pharmacokinetics of propofol in calves undergoing abdominal surgery

Evaluation of hematological, biochemical and oxidative stress profile in calves under propofol anesthesia

Propofol is a widely used drug in veterinary medicine to induce anesthesia; as well as the chosen compound for protocols of intravenous anesthesia. The present study aimed to describe the hematological, biochemical and oxidative stress alterations in calves kept under anesthesia by propofol in different dosages. In order to achieve this, eight Holstein calves were induced using propofol in a 5 mg/kg dosage and maintained under continuous propofol infusion for 60 min, having being administered 0.6 mg/kg/h or 0.8 mg/kg/h in crossover design with seven days interval. Blood samples were collected immediately before the anesthesia induction (baseline), and 30 min, 1, 2, 3, 4 and 5 h after the procedure started. Statistically relevant propofol influence was observed both in blood and biochemical parameters, with differences between dosages according to the time of infusion. The drug action over oxidative stress was also observed, causing a raise of the total antioxidant capacity (TAC) with an uric acid increase. Additionally, the increase of triglycerides, induced by the anesthesia maintenance with propofol, caused lipemia in the samples, which was capable of interfering directly in the measurements made by refractometry and spectrophotometry. It was concluded that, in spite of propofol induced alterations in blood and biochemical parameters, such alterations are subtle. In addition to that, the drug presented an antioxidative effect, which reinstates the safety of anesthesia maintenance with propofol in calves.

Continuous infusion of propofol in calves: bispectral index and hemodynamic effects

OBJECTIVE

To assess the bispectral index (BIS) and the hemodynamic effects of propofol administered by continuous infusion at different rates in calves.

STUDY DESIGN

Experimental crossover study.

ANIMALS

Eight intact male Dutch calves, aged 6-12 months and weighing 84-124 kg.

METHODS

The calves were anesthetized with propofol (5 mg kg(-1) ) intravenously (IV), and after endotracheal intubation, positioned in right lateral recumbency and allowed to breathe ambient air. Anesthesia was maintained by continuous infusion of propofol, administered IV with an infusion pump at 0.6 mg kg(-1)  minute(-1) (treatment G6) or 0.8 mg kg(-1)  minute(-1) IV (treatment G8), for 60 minutes. The eight animals were anesthetized twice, 1 week apart. The following hemodynamic variables and BIS were assessed before the induction of anesthesia (baseline) and 15, 30, 45, and 60 minutes after beginning the infusion of propofol: heart rate, systolic, diastolic and mean arterial pressures, cardiac output, mean pulmonary artery pressure, cardiac index, stroke index, pulmonary vascular resistance index, and systemic vascular resistance index, BIS, electromyography, and signal quality index.

RESULTS

The continuous infusions of propofol at different rates did not alter BIS variables during the infusion time between dose rates, and no clinically significant hemodynamic changes were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

A continuous infusion of propofol at 0.6 or 0.8 mg kg(-1)  minute(-1) caused minimal hemodynamic changes without clinical relevance in calves. BIS could not be reliably used to discriminate the anesthetic depth during the two propofol infusion rates.