Acute effects of general anesthesia with propofol, pentobarbital or isoflurane plus propofol on plasma metabolites and hormones in adult pigs.

Experimental setups for physiological research, in which acute operative interventions need to be performed, can require inclusion of general anesthesia (GA), which may interfere or confound with the effects of the experimental factors of interest on measured variables. It was recently shown that the most commonly used sedatives/anesthetics in pigs (e.g., ketamine, xylazine, azaperone) affect physiological responses and thus the primary metabolic readouts have the potential to be confounded. To extend the search for a physiologically-friendly anesthesia regime for such studies, we investigated effects of GA induced by propofol (Prop) or pentobarbital (Pent) or propofol plus isoflurane (Prop + Isof) on plasma concentrations of commonly measured metabolites and hormones. In 2 experimental runs, 6 female pigs fitted with jugular vein catheters were used. Fasted pigs received either no drug (CON) or anesthetized rotationally either with Prop, Pent or Prop + Isof on different days, separated with washout periods of sufficient length (2 to 3 d). Six-h profiles of glucose, lactate, non-esterified fatty acids (NEFA), triglycerides (TG), cholesterol, urea as well as hormones including glucagon, insulin and cortisol were determined. Concentrations of cholesterol, urea and glucagon remained unaffected by any of the treatments ( > 0.05). Pent tended to increase cortisol from 30 to 90 min after drug administration. Glucose and lactate concentrations were increased ( < 0.05) by Prop and Pent within the first hour of GA ( < 0.05). Propofol and Pent reduced NEFA concentrations, which were more pronounced during the last 2 h of the studied period. Triglyceride concentrations were increased by all 3 agents within the first 45 min with Prop containing treatments exerting a stronger effect than Pent. Our data suggest that GA with Prop and particularly with Pent adulterate plasma metabolite and hormone profiles of pigs acutely, and thus has the potential to confound the effects of experimental factors of interest. Although Prop + Isof anesthesia did not differ from the controls, providing a physiologically-friendly GA, both single and the isoflurane-combined treatment of Prop induced hypertriglyceridemia due to the lipid adjuvant of the Prop drugs. It is concluded that readouts obtained under GA may be influenced both by physiological adulterations as response to anesthesia as well as by artifacts due to accompanying ingredients of the drug formulations.