title: Flexible valinomycin electrodes for on-line determination of intravascular and myocardial K+.
abstract: Flexible electrode systems capable of monitoring in vivo changes in venous and myocardial extracellular potassium activity were constructed using valinomycin-polyvinyl chloride matrix membrane and polyvinyl chloride tubing. Electrode impedance was 1--30 Momega, time constant 10--200 ms, drift less than 1 mV/h, and shelf life approximately 3 days (intramyocardial electrode) and approximately 6 wk (venous electrode). In vitro and in vivo accuracy were determined in 5 dogs and 18 pigs, anesthetized with sodium pentobarbital (35 mg/kg iv), with normal and elevated K+ levels. Serum and venous K+ concentration, determined using a K+ electrode with tip diameter of 1.5 mm, correlated well to serum K+ values determined by flame photometry (r = 0.997). Steady-state myocardial extracellular K+ concentration determined using double-barrel electrodes with total tip diameter of 0.6 mm also correlated well to the serum K+ concentration (r = 0.992). These electrode assemblies permit on-line, virtually instantaneous in vivo determination of intravascular and local myocardial extracellular K+ activity, a capability not previously available.
mesh_terms: D000818:Animals; D002138:Calibration; D004285:Dogs; D004566:Electrodes; D005069:Evaluation Studies as Topic; D008567:Membranes, Artificial; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D009206:Myocardium / Q000032:analysis*; D010783:Photometry; D011188:Potassium / Q000032:analysis* / Q000097:blood; D013552:Swine; D014634:Valinomycin
chemical_list: D008567:Membranes, Artificial; D014634:Valinomycin; D011188:Potassium