Additive effects of propofol and midazolam on dopamine vasodilatation in isolated rabbit renal arteries

Aim: The current study was designed to evaluate the effects of propofol and midazolam on the vasodilatation due to dopamine in isolated rabbit renal artery. Although dopamine is often used in combination with either propofol or midazolam in the intensive care unit setting, no studies examined looked at what additive effect midazolam or propofol may have on the vasodilator effect of dopamine. Methods: New Zealand rabbits were used for renal artery preparation. Renal artery strips 2-3 mm in length were mounted in 20 mL organ baths containing Krebs-Henseleit solution. In order to determine the maximal concentration for dilating the artery tissue, dopamine was added in cumulative log concentrations (10(-9)-10(-5) mol/L) to the bath after the tissue had been contracted with 30 mmol/L KCl solution. The dopamine concentration which had the maximal relaxation effect was used in subsequent trials of propofol and midazolam. After contraction with KCl solution and then relaxation with low-dose dopamine, tissue preparations were exposed to either cumulative log concentrations (10(-9)-10(-5) mol/L) of propofol (n=8) or midazolam (n=8). The force oil the transducer was then recorded, and these measurements were translated into percentages of the initial contraction force. Results: Propofol caused a concentration-dependent increase in relaxation which was statistically significant in all propofol concentrations (10(-9)-10(-5) mol/L) (p<0.05). Midazolam concentrations greater than 10(-9) mol/L (10(-8)-10(-5) mol/L) significantly increased relaxation of the artery tissues (p<0.05). The amount of relaxation in propofol and midazolam groups teas not statistically different (p>0.05). Conclusions: There was air additive effect of propofol or midazolam on dopamine-induced vasodilatation in isolated renal artery.