Method for flushing blood cells using gelatin

An aqueous solution of gelatin used as a flushing liquid for blood cells, in particular erythrocytes, in order to give no changes in the blood cells or at most slight, quality-impairing changes.

BACKGROUND OF THE INVENTION
 The invention concerns the field of flushing liquids for blood cells, in
 particular liquids for washing erythrocytes.
 Flushing and storage liquids for blood cells, in particular for
 erythrocytes, are required in various processes. For example, in machine
 autotransfusion, that is to say obtaining and treating erythrocytes which
 are obtained intraoperatively, they are washed with a flushing liquid for
 subsequent retransfusion. In the machine treatment of blood components
 such as erythrocytes, leucocytes or thrombocytes, the cells are separated
 with a flushing liquid in so-called cell separators, so that they can be
 stored separately for a short period. The blood cells such as erythrocytes
 should be subjected to no changes or the minimum possible changes, by
 virtue of contact with such a liquid.
 Nowadays the operation of flushing erythrocytes is usually implemented with
 physiological common salt solution. It is also known for so-called
 additive solutions such as for example mannitol, in the form of so-called
 SAG-mannitol or PAGGS-mannitol, to be added to erythrocyte concentrates to
 prolong the storage time (see Sibrowski, Anasthesiol. Intensivined.
 Notfallmed. Schmerzther. 1997, 32 (Suppl. 1), page 70). Gelatin-bearing
 infusion solutions are also known, but they have nothing to do with a use
 as flushing liquid for blood cells.
 In regard to the washing of erythrocytes with NaCl-solution for
 autotransfusion it was found that the erythrocyte quality suffered from
 adverse effects due to the contact with the flushing liquid. Those
 erythrocyte quality losses are exhibited in particular due to impairment
 of the O.sub.2 -transport capability of the erythrocytes, which is
 characterised by the form and position of the so-called O.sub.2 -binding
 curve, by spontaneous haemolysis with the consequence of a rising
 haemoglobin and potassium concentration in the ambient liquid, by reduced
 2,3-DPG- and ATP-content of the erythrocytes and disturbance in the
 acid-base housekeeping of the erythrocytes obtained. Quality losses of
 that kind are described in detail in the literature (see R. Karger, V.
 Kretschmer, Anaesthetist 1996, 45, pages 694-707; M. von Finck et al.,
 Anaesthetist 1986, 35, pages 686-692). On the basis of present
 understanding in terms of the quality losses of erythrocytes their
 mechanical properties are in the forefront, with their consequences in
 regard to haemolysis and thus in regard to the loss of transfusable
 erythrocytes and the increase in extra-cellular free haemoglobin and
 potassium. The requirement accordingly is that erythrocyte preparations
 may only be transfused if haemolysis of the preparation is no greater than
 0.8% (Council of Europe, Recommendations 1997).
 It was in consideration of the quality impairments ascertained in respect
 of erythrocytes due to the contact with known flushing liquids that the
 object of the present invention arose, namely obtaining flushing liquids
 for blood cells, in particular erythrocytes, which do not involve any
 changes in the blood cells or at most slight changes such as to impair
 quality.

EXAMPLES AND COMATIVE EXAMPLES
 Aqueous solutions of four different commercially available gelatin types
 according to the invention as well as commercially available additives and
 dextrans and hydroxyethyl starch which are suitable for infusion solutions
 and finally physiological common salt solution were used for determining
 the haemolysis of erythrocytes. The solutions were compared in regard to
 spontaneous haemolysis and mechanical haemolysis, the gelatin solutions,
 hydroxyethyl starch solutions, dextran solutions and additive solutions
 being respectively brought together as their haemolysis values were in
 each case close together irrespective of the origin thereof.
 Spontaneous haemolysis was ascertained as follows: fresh human blood was
 centrifuged three times (10 min at 1600 g), in each case with replacement
 of the plasma by excessive flushing liquid (10 ml of liquid per 2 ml
 erythrocytes). The haematocrit was adjusted to 50.+-.5% by the removal of
 excessive flushing liquid. The concentration of the free haemoglobin in
 the last flushing liquid was then ascertained.
 The mechanical haemolysis rate was ascertained by means of a tonometer IL
 237 (from Instrumentation Laboratory). A thin, respectively fresh film of
 the erythrocytes was produced in that apparatus in a space which was
 temperature- controlled to 37.degree. C. and through which flowed gases
 saturated with water vapour, in a glass vessel (volume a maximum of 8 ml),
 by intermittent rotation, that is to say by accelerating and stopping the
 vessel. Rotation was effected intermittently for one hour under
 physiological conditions (pH-value of 7.40 and CO.sub.2 -partial pressure
 of 40 mm Hg). The haemoglobin concentration in the supernatant matter was
 then determined. The values obtained are set out in the following Table.
 TABLE
 Spontaneous haemolysis (%) after suspension of erythrocytes and
 mechanical haemolysis rate (%/h) of erythrocytes (haematocrit 50 .+-. 5%)
 Mechanical
 haemolysis
 Spontaneous rate
 haemolysis (%) (%/h)
 7 plasma samples not measurable 0.06 .+-. 0.07
 7 samples in 0.9 g/dl NaCl 0.3 .+-. 0.2 2.2 .+-. 0.7
 Infusion solutions
 4 preparations of gelatin 0.04 .+-. 0.04 0.1 .+-. 0.08
 concentration 30-55 g/l
 MW 30,000-35,000
 8 preparations hydroxyethyl 0.3 .+-. 0.2 3.0 .+-. 0.7
 starch
 concentration 30-100 g/l
 MW 70,000-450,000
 7 preparations dextran 0.4 .+-. 0.2 5.7 .+-. 2.7
 concentration 60-100 g/l
 MW 40,000-70,000
 Additive solutions
 2 preparations 0.1 2.8
 PAGGS- or SAG-mannitol
 The values obtained show that both spontaneous haemolysis and also the
 mechanical haemolysis rate of the four gelatin solutions tested are
 comparable to the values of plasma and the gelatin solutions give
 negligible haemolysis. The values are far below the haemolysis value of
 0.8% which is demanded by the Council of Europe. In contrast thereto the
 haemolysis values both for spontaneous haemolysis and also for mechanical
 haemolysis with the physiological common salt solution which is usually
 employed nowadays for the flushing of erythrocytes and the additive
 solutions which are usual nowadays for erythrocyte concentrate storage
 were considerably higher and far above the required value of 0.8%.
 For comparative purposes known infusion solutions with hydroxyethyl starch
 and dextran were also included in the tests. Haemolysis with those
 polymers was even higher than with the investigated additive solutions and
 physiological common salt solution.