PubMed · 5861316
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M G Chesnut, P B Callaghan, D H Watkins. Assisted circulation controlled by electronic computation.. https://doi.org/10.1109/tbme.1965.4502375
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LDL aggregates when exposed to even moderate fluid mechanical stresses in the laboratory, yet its half-life in the circulation is 2-3 days, implying that little aggregation occurs. LDL may be protected from aggregation in vivo by components of plasma, or by a qualitative difference in flows. Previous studies have shown that HDL and albumin inhibit the aggregation induced by vortexing. Using a more reproducible method of inducing aggregation and assessing aggregation both spectrophotometrically and by sedimentation techniques, we showed that at physiological concentrations, albumin is the more effective inhibitor, and that aggregation is substantially but not completely inhibited in plasma. Heat denatured and fatty-acid-stripped albumin were more effective inhibitors than normal albumin, supporting the idea that hydrophobic interactions are involved. Aggregation of LDL in a model reproducing several aspects of flow in the circulation was 200-fold slower, but was still inhibited by HDL and albumin, suggesting similar mechanisms are involved. Within the sensitivity of our technique, LDL aggregation did not occur in plasma exposed to these flows. Thus, as a result of the characteristics of blood flow and the inhibitory effects of plasma components, particularly albumin, LDL aggregation is unlikely to occur within the circulation.
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The effectiveness of alteplase and urokinase in restoring adequate hemodialysis blood-flow rates was examined. A retrospective review of the medical records of hemodialysis patients with central venous catheters receiving alteplase or urokinase for presumed catheter thrombosis between June 1997 and December 2000 was conducted. Patients received 1 mL of alteplase 1 mg/mL or 1 mL of urokinase 5000 units/mL in each catheter port. The choice of the thrombolytic agent was left to the prescriber. Effectiveness of thrombolysis was defined as achieving a posttreatment hemodialysis blood-flow rate of > 300 mL/min, maintained for at least 30 minutes during the dialysis session. Inclusion criteria included adherence to the thrombolytic protocol and the inability to achieve a hemodialysis blood-flow rate of > 300 mL/min during the first 60 minutes of the hemodialysis session despite at least one attempt to reposition the catheter. Both thrombolytic agents significantly increased the hemodialysis blood-flow rates. Patients with alteplase-treated catheters were twice as likely to achieve hemodialysis blood-flow rates of > 300 mL/min (p = 0.0134) and were more likely to complete hemodialysis during that session (93% versus 70%, p = 0.0234). The percentage of functioning catheters at a subsequent hemodialysis session did not significantly differ between groups (p = 0.0806). The majority of patients in both treatment groups required no further interventions. Hemodialysis blood-flow rates increased after either alteplase 1 mg/mL per port or urokinase 5000 units per port was used to clear presumed catheter thrombosis. Alteplase was more likely than urokinase to result in a hemodialysis blood-flow rate of > 300 mL/min.