Evaluation for hemodialysis access. The creation of optimal vascular access requires an integrated approach among patient, nephrologist, and surgeon. The preoperative evaluation includes a thorough history and physical examination. A history of arterial and venous line placements should be sought. The upper extremities are examined for edema and asymmetry of pulse and blood pressure. Access should be placed at the wrist only after it is verified that the radial artery is not the dominant arterial conduit to the hand. The classic study is the Allen test, in which an observer compresses both the radial and ulnar arteries, has the patient exercise the hand by opening and closing to cause blanching, then releases one vessel to be certain that the fingers become perfused. An alternative, and perhaps more precise, test is to verify by Doppler imaging that flow to all digits is maintained despite occlusion of the radial artery. If indicated, vascular imaging studies should be used to delineate the vascular anatomy and rule out arterial or venous disease. Clinically silent stenosis involving the central veins is becoming increasingly common with the improved survival of critically ill patients for whom central vein catheters are commonplace.
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