Electrode silver —■ silverchloride

Porphyrinic catheter-protected sensors can be sterilized with ethylene oxide and used for NO measurement in humans. For measurements of NO in veins or arteries, an intervenous catheter is used. TVo cannulae are inserted into a vein. A 24 G catheter is inserted retrogradely and a 23 G butterfly needle is positioned anterogradely with its tip 10—15 nun from the end of the catheter. The catheter is flushed with 0.5 ml heparin (5000 U/ml) and a nitric oxide sensor is mounted on a 24-G needle and is placed so its tip protruded 1-2 mm beyond the end of the catheter. A platinum-wire counter electrode and silver/silverchloride reference electrode can be placed on the skin adjacent to the vein and covered with conductive gel. Heparin solution physiological saline or drugs can be infused continuously throu the butterfly needle. Infusion of acetylcholine causes a dose-dependent NO signal, attenuated by co-infusion of inhibitor of nitric oxide synthase L-NMMA or L-arginine (Figure 19). 

---