[Continuous pH registration in the coronary sinus in vivo in ischemic and normoxic lactic acidosis using an ion sensitive field effect transistor catheter].

A new catheter with an Ion Sensitive Field Effect Transistor (ISFET) for continuous measurements of blood pH in vivo was employed. In canine heart preparations (n = 15), two catheters were positioned in the coronary sinus and in the abdominal aorta, respectively. A close agreement between pH-measurements with the pH-ISFET-sensor and the corresponding pH-determinations on blood samples by conventional means (r = 0.97; pH-range 7.15-7.50) was found. The ISFET-sensor revealed a sensitivity of 50-55 mV/pH, a long-term drift rate of 1-2 mV/h, as well as a response time shorter than 100 ms. The ISFET-sensor was sensitive for the detection of respiratory and metabolic acidosis and alkalosis (hypo-, hyperventilation, myocardial ischemia, intracoronary infusion of 0.3-M lactic acid). There was a close correlation between the changes of coronary venous pH and lactate concentrations during myocardial ischemia (r = 0.83; n = 9). During ischemic acidosis there was a drastic reduction of left ventricular dp/dtmax, whereas contractility changes during normoxic lactacidosis were moderate. The pH-decrease (pH = 7.1) was identical in both interventions. The observed data suggest that the newly developed ISFET-pH-catheter is working precisely and enables respiratory and metabolic control of the whole organism as well as of individual organs.