INPUT IMPEDANCE OF RADIOCEPHALIC ARTERIOVENOUS-FISTULAS FOR HEMODIALYSIS ACCESS - ITS VALUE IN PREDICTING EARLY FAILURE

This study is concerned with an assessment of the quality of the blood vessels used in the construction of radiocephalic arteriovenous fistu lae for haemodialysis vascular access in 20 patients. Following non-in vasive preoperative assessment of the cephalic vein by means of a colo ur Doppler scanner, input impedance was determined intraoperatively fr om blood flow and blood pressure measured about 2 cm downstream of the anastomosis. The patients were re-assessed 1 day and 2, 4, 6 and 12 w eeks after surgery, and the diameter and the flow through the fistulae , the location of major branches, and the presence and severity of ste noses in the cephalic veins were determined non-invasively. Five fistu lae failed within the 12 weeks period following surgery, mainly due to thrombosis. In a further 3 patients, the fistulae were patent but did not achieve an adequately high blood Row and dilate sufficiently for haemodialysis and were therefore considered to be essentially failed. The impedance moduli from 0 to 10 Hz as well as the average impedance modulus of successful fistulae were significantly lower than those of fistulae that subsequently failed. An attempt was made to locate the p resence of reflection sites (i.e. stenoses and branches) from the mini ma in the impedance modulus spectra. Their locations were compared wit h those of the reflection sites detected by ultrasound 2 weeks after s urgery. However, nor all reflection sites detected 2 weeks after surge ry were located by the impedance method. It is recommended that both p reoperative examination and intraoperative haemodynamic measurements b e made to improve the accuracy of the assessment.