Technical aspects and complications of plasma-exchange

Hemodynamic Tolerance and Plasma Volume Variations during Plasma Exchange

Little is known about mechanisms of systemic hypotension frequently reported during plasma exchange (PE). Type of substitution fluids may interfere with hemodynamic tolerance. In a prospective study, right heart catheterization was performed during 18 PE by filtration with isovolumic substitution. Blood volume was measured with 51Cr tagged erythrocytes and plasma volume (PV) calculated from hematocrit. Substitution fluids were either albumin (A; n = 9) or A + gelatin (A + G; n = 9). In both groups, PE induces significant (p < 0.01) decreases of mean arterial pressure: group A: - 21 ± 14%; group A + G: - 23 ± 15%; of pulmonary wedge pressure: group A: - 41 ± 33%; group A + G: - 36 ± 22%; of cardiac index: group A: - 38 ± 18%; group A + G: - 25 ± 15%. Plasma volume also decreases after PE: group A: - 13.5 ± 4%; group A + G: - 18.5 + 4%. None of the variations are significantly different between the two groups. So we think that substitution with albumin alone has no advantage for hemodynamic tolerance.

Effects of Membrane Plasma Exchange on the Hemostatic System and on Thyroid Hormones in Critically Ill Patients

The present study examined the effects of repeated plasma exchanges with membrane filtration (Plasmaflux P2 membrane, 4.3 I human albumin solution) on the hemostatic system and on thyroid hormones in critically ill patients.

Clotting factors V, VII, VIII, IX, X, XI, XII, XIII, fibrinogen, antithrombin III (ATIII), prothrombin time (PT), activated partial thromboplastin time (PTT), total (TT3) and free tri-iodothyronine (FT3), total (TT4) and free thyroxine (FT4), and thyroxine binding globulin (TBG) were determined before, immediately after, 1, 3, 6 and 24 h after plasma exchange in 6 patients (3 with glomerulonephritis, 2 with IgG myeloma, 1 with chronic polyneuritis) during 18 plasma exchanges.

After plasma exchange levels of clotting factors and ATIII were markedly lowered but except for fibrinogen and factor XIII, they were not reduced by repeated exchange procedures. Thyroid hormones and TBG were reconstituted after 24 h. Pre-exchange levels, except for TT4 and TBG, were not lowered by repeated exchange procedures.

Risk of bleeding or thrombosis is small and there is no appreciable risk of loss of thyroid hormones during repeated plasma exchanges.

Immunoadsorption therapy for myasthenia gravis

The results of a multicentre trial were analysed to evaluate the efficacy of immunoadsorption therapy for severe generalised myasthenia gravis. Twenty patients with myasthenia gravis who were concurrently receiving high dose prednisolone and azathioprine therapy were treated with an affinity-type adsorbent, using tryptophan-linked polyvinyl alcohol gel (IM-TR), according to a standardised treatment protocol. The 20 patients received five adsorption treatments within a period of 10 days. In 11, pronounced improvement of myasthenic weakness was seen and long-term remission was maintained. The treatment was especially effective in patients with thymic hyperplasia. Circulating acetylcholine receptor (AChR) antibodies were reduced by about 60% by treating one plasma volume. There was no difference in the rate of removal of the AChR antibodies between patients with thymic hyperplasia and patients with thymoma. No serious complications occurred during 100 procedures. It was concluded that the immunoadsorption therapy with IM-TR is useful in controlling symptoms in patients with severe myasthenia gravis who are otherwise unresponsive.