Effects of extracorporeal hemapheresis therapy on blood rheology.

The blood flow property is one of the factors determining blood perfusion and oxygen supply. The viscosity of the blood is primarily related to the hematocrit, but also to the amount of fibrinogen and other macromolecules present in the blood. Patients with ischemic heart disease have shown a rapid and safe improvement in their hemorheological state when treated with heparin-induced extracorporeal low-density lipoprotein (LDL) precipitation (HELP). In this study we used two extracorporeal hemapheresis methods, plasmapheresis (PP) and immunoadsorption (IA), in 15 patients (eight patients treated with PP and seven patients with IA) with various diseases. Hemorheological variables and plasma fibrinogen were measured before and after the first and before the third treatment performed at 3 consecutive days. The aim of our study was to investigate the immediate effects of these two treatment modalities on the flow properties of blood. Immediately after the first PP and IA session statistically significant declines in plasma fibrinogen concentration, plasma viscosity, whole blood viscosity, and erythrocyte aggregation tendency were found. These changes persisted before the third treatment session. The erythrocyte fluidity and hematocrit remained unchanged. We conclude that extracorporeal hemapheresis therapy, with plasmapheresis or immunoadsorption, affects the blood rheology by decreasing the plasma viscosity and erythrocyte aggregation tendency. The decrease in plasma fibrinogen is probably the main factor underlying that, but other factors such as a decrease in immunoglobulins may also be of importance.

Rheology of paraproteinaemias and the plasma hyperviscosity syndrome.

The proper understanding of the causes, pathophysiology, diagnosis and management of the plasma hyperviscosity syndrome is based on good knowledge of malignant paraproteinaemias, properties of immunoglobulins, rheology of blood in the microcirculation, and modern plasma separation techniques. This multifaceted syndrome complicates less than ten per cent of IgA and IgG myelomas, and up to one-third of Waldenström's macroglobulinaemias. A few cases of HVS have also been reported in association with polyclonal hypergammaglobulinaemias. Excessive paraproteinaemia may cause the plasma HVS, especially when paraproteins are extraordinarily large, asymmetrical or cryosensitive, or if they aggregate into hyperviscous macroaggregates. The resultant severe microcirculatory impairment is mainly due to the combined effects of plasma hyperviscosity, significant plasma volume expansion and intense red cell aggregation. The individually variable general symptoms, bleeding tendency, ocular, neurological, cardiovascular, and renal manifestations and laboratory parameters of the HVS are summarized briefly. The majority of patients present hyperviscosity manifestations when the plasma viscosity exceeds 5-6 mPa.s. Plasmapheresis or plasma exchange have established themselves as efficient and safe modes of therapy of hyperviscosity and hypervolaemia. The therapeutic guidelines for the plasma HVS are briefly discussed with regard to recent experience with developing plasma separation techniques. Diagnostic and therapeutic advances combined with increasing haemorheological knowledge have greatly improved the proper management of this potentially lethal complication of paraproteinaemias.

Blood rheology in the newborn infant.

The blood in neonates shows several peculiar properties which affect its rheological properties. 1. The haematocrit in neonates may be as high as 0.65 l/l without any clinical signs. 2. Both plasma viscosity and red cell aggregation are markedly lower in neonates than in adults because of low protein levels in neonates. This results in decreased blood viscosity at given haematocrit, particularly at low shear forces. 3. Deformability of neonatal red cells is similar to that of adult cells when studied under controlled conditions (e.g. rheoscope, ektacytometer). However, neonatal red cells are less filterable and require higher pressures for entering narrow micropipettes than adult red cells due to the larger size of neonatal red cells. 4. Neonatal leukocytes require higher pressure for the passage of 5 microns filter pores or 5 microns micropipettes than adult cells. The following haemorheological disorders have been observed in neonates: 1. Polycythaemia in infants with late cord-clamping, severe asphyxia, growth retardation and diabetic mothers. 2. Markedly decreased red cell deformability in septicaemia, necrotizing enterocolitis and in vitamin E deficiency (after exposure to oxidizing agents). 3. Moderately decreased red cell deformability in infants with diabetic mothers, growth retardation and severe acidosis. 4. Increased red cell aggregation in septicaemia. 5. Lack of red cell aggregation in immature neonates. 6. Decreased ability of leukocytes from septic neonates to pass filter pores and micropipettes. Treatment may be either haemodilution (in polycythaemia) or exchange transfusion (in septicaemia and necrotizing enterocolitis). Haemorheological drugs have not been used in neonates.

Tx polyagglutination in three members of one family.

A case of acute haemolytic anaemia is described in a child. Tx polyagglutination of his red cells was observed, but no direct association with the anaemia could be proved. Polyagglutination was suspected because of irregularities in the AB0 blood grouping. Confirmation of the cryptantigen Tx was made when the patient's red cells were tested with lectins including Arachis hypogaea, Glycine soja, and Vicia cretica. Examination of family members showed Tx polyagglutination on the red cells of 2 siblings. The Tx polyagglutination was a transient phenomenon lasting 4-5.5 months, and could have been caused as the result of some unidentified bacterial or viral infection. Guidelines for transfusion therapy are suggested in patients in whom polyagglutination is recognised.

Erythrocyte aggregation in clinical medicine.

Red cell aggregation is one of the part of the properties of blood which determine blood flow in the impaired microcirculation. Erythrocyte aggregation does influence not only the viscosity at low rates of shear but leads to a vicious circle which again impairs the blood flow in the microcirculation. In the other hand it seems obvious that red cell aggregation leads to an inhomogenous distribution of microcirculatory blood flow (maldistribution) thereby decreasing the oxygen transport tissue. In a great number of diseases red cell aggregation is increased and in some diseases this fact is responsible for clinical symptoms. This view is supported by the therapeutic benefit seen in patients with paraproteinaemia as well as in patients with vascular diseases treated with plasmapheresis or defibrinogenation, respectively. There is no doubt about, a reduction of red cell aggregation by desaggregating drugs to improve microcirculatory blood flow and do increase the oxygen supply to tissue. It is however hard to differentiate between the influence of red cell aggregation and/or plasma viscosity on the impaired microcirculation since both parameters are closely connected in most of these diseases.

[Disorders of microcirculation in food poisoning]. / Narushenie mikrotsirkuliatsii u bol'nykh s toksikoinfektsiiami.

Thirty-seven patients with alimentary toxicoinfections were examined. The values of central and peripheral circulation and the fluid spaces were determined by one-stage dilution of two indicators, T-1824 and sodium thiosulfate. The capillary blood flow was studied by means of bulbar microscopy in reflected light. A deficit of interstitial fluid prior to treatment and disorder of microhemo- and lymphocirculation were revealed. Infusion of a crystalloid blood substitute with an optimum volume and rate increased capillary filtration and corrected the transinterstitial metabolism.

[Disorders of microcirculation in diffuse toxic goiter and their correction in the early postoperative period]. / Narusheniia mikrotsirkuliatsii i ikh korrektsiia u bol'nykh diffuznym toksicheskim zobom v rannem posleoperatsionnom periode

A study was made of microcirculation in 45 patients suffering from diffuse toxic goiter at the early postoperative period with the aid of microphotography of the bulbar conjunctiva vessels, and investigation of the rate of the isotope elimination from the intradermal depot and the capillary permeability by V. P. Kaznacheev's method. The data obtained permitted to draw a conclusion that on admission to the clinic patients with toxic goiter were suffering from arteriolar spasm, had poor vascular pattern in the bulbar conjunctiva, the sledge phenomenon in small venules, an acceleration of the isotope elimination from the intradermal depot and an increase of the capillary permeability. Preoperative preparation improved the microcirculation indices, without completely normalizing them, however. Microcirculatory disturbances reached their maximum the first two days after the operation and declined by the 3rd-5th day. Recommendations on correction of the microcirculatory disturbances are given.