Pulse oxymetry evaluation of oxygen saturation in the upper extremity with an arteriovenous fistula before and during hemodialysis

We noticed that some patients with arteriovenous (AV) fistula on chronic hemodialysis experience pain in the limb with the fistula a short time after being connected to the dialysis machine. We postulated that the pain is caused by relative ischemia and therefore performed this study to determine whether oxygen saturation (SaO 2) of the extremities with AV fistula decreases during hemodialysis. Seventy-two patients with a side-to-side primary AV fistula were evaluated by pulse oxymetry. Sa0 2 was measured before hemodialysis and 20 minutes after initiation of dialysis. The contralateral arm served as a control. In 48 patients, Sa0 2 difference between the arms of each patient before hemodialysis was less than 4%. Sa0 2 values of this group of patients did not change significantly 20 minutes after initiation of dialysis. In 24 patients, SaO 2 differences between the hands of each patient before hemodialysis were 4% or more. In this group of patients, Sa0 2 values of the hands with the AV fistula decreased significantly 20 minutes after hemodialysis from a mean of 90.85 ± 2.84% to 81.60 ± 3.94 ( P < 0.001). SaO 2 remained unchanged in the contralateral arm. Nine patients in this group complained of pain and change in sensation in the arm with the fistula during hemodialysis. One patient complained of severe pain in the arm with the fistula before hemodialysis, and SaO 2 was unmeasurable. We conclude that, in some patients, SaO 2 of the arm with the AV fistula decreases only during hemodialysis. This phenomenon may be symptomatic. A predialysis SaO 2 difference of 4% or more between the arms predicts decreased Sa0 2 of the arm with the AV fistula during hemodialysis.