Inhibition of platelet and red blood cell accumulation on damaged arterial surfaces with albumin pretreatment

Symptomatic intracranial hemorrhage in the ALIAS Multicenter Trial: relationship to endovascular thrombolytic therapy

BACKGROUND

In the ALIAS (Albumin in Acute Stroke) Part 2 Multicenter Trial, 85% of subjects received standard-of-care intravenous tissue plasminogen activator, and 21% received some form of endovascular thrombolysis. The overall rate of symptomatic intracranial hemorrhage was within the expected range but was higher in albumin-treated subjects than in saline-treated subjects.

AIMS AND METHODS

Using the trial's Public Use Dataset, we analyzed factors contributing to symptomatic and asymptomatic intracranial hemorrhage in the 'safety sample' of 830 subjects.

RESULTS

Four hundred sixteen subjects received albumin therapy, and 414 received saline. Intravenous tissue plasminogen activator was given to 68.2%; intravenous tissue plasminogen activator plus endovascular intervention in 16.4%; and endovascular therapy alone in 43%. Symptomatic intracranial hemorrhage occurred in 41 subjects - within the first 12 h in one-third of cases, and within the first day in ∼60%. Intravenous tissue plasminogen activator had been used in 78% of symptomatic intracranial hemorrhage subjects - no higher than in the overall cohort. In contrast, 48.8% of subjects with symptomatic intracranial hemorrhage had received endovascular therapy - a rate markedly higher than the 20.7% rate for the entire cohort (P = 0.0001). Sixty-eight point three percent of subjects with symptomatic intracranial hemorrhage had received albumin, and 31.7% saline (risk ratio 2.14, P = 0.025). Other factors associated with symptomatic intracranial hemorrhage were baseline NIHSS and ASPECTS scores and the SEDAN score. Forty-one point four percent of subjects with symptomatic intracranial hemorrhage died. The odds ratio for symptomatic intracranial hemorrhage was 3.89 (95% confidence interval 2.04-7.41) with endovascular therapy and 2.15 (confidence interval 1.08-4.25) with albumin.

CONCLUSIONS

Endovascular thrombolysis was the major factor predisposing to symptomatic intracranial hemorrhage, and albumin contributed to this predisposition. The latter may be mediated by albumin's influence on platelet aggregation or collateral perfusion.

Effect of laser welding with human serum albumin on the expression of P-selectin on platelets

BACKGROUND AND OBJECTIVE

Artery repair by means of laser energy induces activation of platelets with a risk of thrombosis and local inflammatory reactions. The aim of this study was to investigate the effect of human serum albumin, the most common solder in laser surgery, on platelet activation.

STUDY DESIGN/MATERIALS AND METHODS

Platelet activation was evaluated in canine blood by using two-color flow cytometry with a phycoerythrin-labeled antibody to a common platelet marker, glycoprotein IIb/IIIa and fluorescein isothiocyanate-labeled antibody to a platelet activation molecule, P-selectin. Human serum albumin was applied in vitro and in vivo, as a solder during laser reconstruction of canine arteries.

RESULTS

In vitro, albumin significantly (P < 0.01) reduces the expression of P-selectin on platelets. This is most likely related to the blockage of P-selectin by albumin, which binds to the platelet surface, as confirmed by flow cytometry with fluorescein isothiocyanate-labeled albumin. In vivo, application of albumin solder tended to result in a lower percentage of P-selectin-expressing platelets in laser-repaired arteries compared to suture-repaired arteries.

CONCLUSION

Albumin decreases the percentage of P-selectin-expressing platelets in vitro. Further research may allow the platelet activation inhibiting properties of albumin to be further optimized in vivo.

Hypoalbuminemia causes high blood viscosity by increasing red cell lysophosphatidylcholine

Albumin deficiency is accompanied by a reduction in red cell deformability and blood hyperviscosity. Albumin deficiency increases plasma fibrinogen and triglyceride levels and may alter red cell membrane lipid composition. These options, which could all contribute to reduced red cell deformability (RCD) and hyperviscosity, were studied in the Nagase analbuminemic rat (NAR), a mutant Sprague Dawley rat (CON), characterized by normal total protein levels, with an absolute deficiency of albumin, but elevated levels of non-albumin proteins and hyperlipidemia. Plasma protein-binding of the polar phopholipid lysophosphatidylcholine (LPC) was markedly decreased. LPC comprised only 26 +/- 1% of total plasma phospholipids as compared to 42 +/- 2% in CON. NAR red cells in CON plasma had a viscosity that was similar to CON red cells in CON plasma. Conversely, CON red cells in NAR plasma show an increased viscosity as compared to CON red cells in CON plasma. The maximum deformation index of both NAR and CON red cells was markedly decreased in NAR plasma as compared to either NAR or CON cells in CON plasma (0.04 +/- 0.03 and 0.02 +/- 0.02 vs. 0.22 +/- 0.06 and 0.15 +/- 0.04, respectively; P < 0.05). Thus, plasma composition causes hyperviscosity and reduced RCD in NAR. Fibrinogen is not responsible since red cells in serum and red cells in plasma had a similar viscosity and differences in viscosity and RCD between NAR and CON were maintained. Plasma triglycerides are also not responsible since the viscosity of red cells in serum with a 50% reduction in triglycerides was not reduced. LPC levels in red cells were increased in NAR (8.7 +/- 0.2 vs. 5.5 +/- 0.3% of total phospholipids; P < 0.01). Adding albumin to NAR blood dose-dependently decreased whole blood viscosity, despite marked increases in plasma viscosity, and increased RCD of NAR cells (from 0.04 +/- 0.03 to 0.21 +/- 0.01; P < 0.05). There was also some effect on CON RCD of similar albumin addition to CON blood (from 0.15 +/- 0.04 to 0.29 +/- 0.03; P < 0.05). Adding albumin to NAR blood reduced red cell LPC content and increased plasma LPC content in a dose-dependent fashion, whereas there were only slight effects of adding albumin to CON blood. There was a reciprocal relation between red cell LPC and the other polar phospholipids in the red cell membrane, probably indicating exchange. The maximum deformability index of either NAR or CON cells was not affected much by adding LPC to CON plasma (NAR, from 0.22 +/- 0.06 to 0.18 +/- 0.10; CON, from 0.15 +/- 0.04 to 0.12 +/- 0.05; NS), whereas adding LPC to NAR plasma caused the red cells to become rigid. Adding LPC to CON red cells in NAR plasma caused a much stronger increase in relative LPC content (from 6.6 +/- 0.7 to 10.9 +/- 0.9%; P < 0.05) than adding LPC to CON red cells in CON plasma (from 5.6 +/- 0.4 to 6.4 +/- 0.8%; NS). Thus, in the absence of albumin, LPC in red blood cells is increased. As a consequence of the latter, RCD is decreased and whole blood viscosity increased. Alterations in red cell phospholipids are far more important than increases in plasma fibrinogen or triglycerides in determining hyperviscosity of blood and reduced RCD in NAR.