The effects of propofol on heart rate, arterial pressure and A delta and Csomatosympathetic reflexes in anaesthetized dogs

The effects of propofol on mean arterial pressure, heart rate and A delta a nd C somatosympathetic reflexes, recorded in renal nerves, evoked by repeat ed individual supramaximal electrical stimuli applied to radial nerves, wer e observed in anaesthetized, paralysed and artificially ventilated dogs. Pr opofol was infused at rates from 0.4 to 2.0 mg kg(-1) min(-1). Mean C and A delta reflexes were abolished at plasma concentrations (mean, SEM) of 24.3 (3.3) and 29.2 (2.6) mu g mL(-1) (P < 0.05), respectively, when mean arter ial pressure and mean heart rate were reduced by approximately 55% (P < 0.0 1) and 26% (P > 0.05), respectively. Recovery of A delta and C reflexes occ urred at plasma concentrations of 13.1 (2.3) and 9.9 (1.3) mu g mL(-1) (P > 0.05), respectively. There was a log- arithmically linearly related fall i n mean arterial pressure by 70% up to a plasma concentration approximate to 97 mu g mL(-1) (r(2) = 0.7) with a 28% reduction in heart rate which was u ncorrelated with the plasma concentrations (r(2) = 0.12). In conclusion, pr opofol abolished A delta and C responses at comparable plasma concentration s and caused a major reduction in both mean arterial pressure and heart rat e which is consistent with resetting of the baroreflexes. The reduction in mean arterial pressure was logarithmically, linearly correlated with a prog ressive increase in plasma concentrations without evidence of a ceiling eff ect.