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.

Functional compartmentation of glycolytic versus oxidative metabolism in isolated rabbit heart.

“…A triple barrel K/pH electrode, overall tip diameter 0.5 mlm, was used to measure extracellular K+ and pH. The K+ barrel (tip diameter 0.2 mm) was constructed by the method of Hill et al (16). The solid state pH barrel (0.1 mm diameter) was obtained commercially (Beetrode, WP Instruments, Inc., New Haven, CT).…”

Continuous Coronary Venous K<SUP>+</SUP> Monitoring During Myocardial Ischemia in Swine Hearts

“…29,30) Later, it was shown that acute coronary occlusion leads to a fall in extracellular pH and a rise in extracellular pCO 2 . 31,32) Development of catheter-tip potassium-selective electrodes by Treasure et al 27) and Hill et al 28) led to clinical measurement of coronary sinus potassium levels during coronary angioplasty, which showed a transient increase in coronary sinus potassium after deflation. 33,34) In a clinical study in which serial coronary sinus and arterial blood sampling was performed during pacing to determine the effects of ischemia and alterations in heart rate on myocardial potassium, investigators found a significantly greater loss of myocardial potassium in patients with ischemia than in those without ischemia.…”

“…18) An intravascular K + -selective electrode was fashioned and calibrated by methods described previously. 27,28) In brief, a disk from the valinomycin matrix membrane was placed on the tip of the medical grade polyvinyl chloride tubing which had an outer diameter 1.5 mm and an inner diameter of 1.0 mm, and then fused to it by application of 1 or 2 drops of tetrahydrofuran to the perimeter of the disk. The electrode was dried in air for 10-15 minutes and then filled with 0.5 KCl saturated with silver chloride.…”

Combined Effects of Acidosis and Hyperkalemia on Conduction Slowing and the Effective Refractory Period in an in-situ Canine Heart

“…2) 19,20) . Electrodes were calibrated before each experiment in standard solution (3 or 10 mmol/L KCl).…”

“…Only electrodes with a stable baseline drift (< 1 mV/hour) and 95-105% of the predicted Nernstain slope (56-62 mV shift per decade change in K + activity at room temperature) were used. The in vivo performance of these electrodes was tested by methods described previously 19,20) . At the end of each experiment, the electrodes were removed from the heart and retested in vitro to confirm stable function throughout the experiment.…”