Cardiopulmonary Recirculation in Dialysis An Underrecognized Phenomenon

Authors:
  • HPHans D. Polaschegg
    Hans D. Polaschegg
  • NLNathan W. Levin
    Nathan W. Levin
  • GCGIL A. Cu
    GIL A. Cu
  • AMAlice T. Morris
    Alice T. Morris
  • MKMatthias Krämer
    Matthias Krämer
  • JDJohn T. Daugirdas
    John T. Daugirdas
  • AKAllen M. Kaufman
    Allen M. Kaufman
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Abstract
Access recirculation can be determined by measuring blood temperature or blood water concentration in the dialyzer inlet after injecting a bolus of cold saline into the venous line. In patients with access recirculation, some of the cooled venous blood re-enters the blood inlet line soon after injection, resulting in a sharp transient drop in its temperature. There is also a prompt increase in blood water concentration at the dialyzer blood inlet caused by the dilution effect of the recirculated saline. In this study, data are reported on four patients studied under conditions where no access recirculation could occur because blood was returned to a second access or into a central vein. In these patients, transient cooling of the blood in the dialyzer inlet and a transient hemodilution after venous line injection of cold saline was still observed. These observations can be explained by passage of the injected saline through the heart and pulmonary blood vessels and return of a portion of the cooled blood to the vascular access, bypassing the systemic capillary microcirculation. This "cardiopulmonary recirculation" can cause dilution of urea in dialyzer inlet blood, with resulting errors in urea kinetic modeling and in computing access recirculation.