Hemodilution and blood replacement surgery

Blood dilution (hemodilution) to reduce the concentration of toxic substances in it has long been used in practical medicine. This purpose is served by water loading (drinking copiously) and parenteral administration of water-electrolyte and plasma-substituting solutions. The latter are especially valuable in acute poisoning, since they allow, simultaneously with hemodilution, to restore the BCC and create conditions for effective stimulation of diuresis. Blood replacement surgery (hemapheresis).

General characteristics

The main therapeutic factors of this procedure, which consists of simultaneous and equal volume bloodletting and blood transfusion, include the following: detoxification, depuration, substitution and general biological.

The detoxification factor is based on the possible removal of various toxic substances with the patient's blood. In clinical practice, there is a real possibility of performing only a partial blood replacement operation (PBO) in a volume of 1.5-3 liters, while for a virtually complete (95%) replacement of the patient's blood, it is necessary to transfuse at least 15 liters of donor blood, i.e. in an amount 3 times greater than the average BCC.

This circumstance significantly reduces the effectiveness of OZK as a detoxification method, since it allows removing no more than 15% of the toxicant from the blood.

The depurative effect of the blood replacement operation consists of freeing the body from large-molecular compounds (free plasma hemoglobin, myoglobin, etc.), which fundamentally distinguishes this method of detoxification from dialysis, in which such purification is impossible.

The substituting effect of the blood substitution operation consists of replacing the patient's blood, which has been altered morphologically and functionally (methemoglobinemia, etc.), with full-fledged donor blood, as a result of which the recipient's blood approaches the donor's blood in its composition.

The general biological effect of the blood substitution operation is considered to be the general reaction of the body to bloodletting, compensated by the transfusion of donor blood, i.e., in essence, it is a blood transplant as an individual "tissue" of the body from several donors to the recipient. This immunobiological reaction, when moderate, has a stimulating protective effect on the immune system of the body. It is advisable to distinguish absolute indications for the OZK operation, when it is assessed as a pathogenetic treatment and has some advantages over other methods, and relative indications, which can be dictated only by specific conditions when it is impossible to use other, more effective methods of artificial detoxification (HD, hemosorption, etc.).

Indications for the procedure

An absolute indication for blood substitution surgery is poisoning with substances that have a direct toxic effect on blood, causing severe methemoglobinemia (more than 50-60% of total hemoglobin), increasing massive hemolysis (with a free hemoglobin concentration of more than 10 g / l) and a decrease in cholinesterase activity of the blood to 10%. A significant advantage of blood substitution surgery is the relative simplicity of this method, which does not require special equipment, and the possibility of its use in any hospital. At present, given the difficulty of obtaining donor blood, OZK is practically used only in young children.

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Contraindications to the procedure

Contraindications to the use of blood substitution surgery are severe hemodynamic disorders (collapse, pulmonary embolism), as well as complicated heart defects, thrombophlebitis of the deep veins of the extremities.

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Complications after the procedure

Complications of blood substitution surgery include temporary hypotension, post-transfusion reactions, and moderate anemia in the postoperative period. Complications during blood substitution surgery largely determine the clinical condition of patients at the time of surgery. Most patients who did not have significant hemodynamic disorders before the surgery tolerate it satisfactorily. If the surgery is technically correct, the blood pressure level is stable or changes within insignificant limits. Technical errors in the surgery (imbalances in the volume of injected and removed blood) lead to temporary fluctuations in blood pressure within 15-20 mm Hg and are easily corrected when the disturbed balance is restored.

The most severe complications of blood substitution surgery include homologous blood syndrome, which develops during the transfusion of large volumes of donor blood (over 3 liters) and occurs as an immunological rejection reaction.

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