Principles of infusion medium selection
Therapy always begins with the administration of blood-substituting fluids, as maintaining vascular volume is a critical survival factor.
For initial therapy, the following are used:
- Colloid solutions. Albumin- and protein-based preparations, as well as medium-molecular-weight dextrans (with a molecular weight of 50,000 to 70,000), are reliably and persistently retained within the vascular lumen.
- Low-molecular-weight dextrans. Agents with a molecular weight of 30,000–40,000 not only effectively restore lost volume but also normalize microcirculation by improving the rheological properties (fluidity) of blood.
- Crystalloid solutions. Their use is justified and necessary, but it should be remembered that they leave the vascular bed rather quickly, redistributing into the tissues.
Blood products, in particular packed red blood cells, are added to the treatment only after a preliminary infusion of blood substitutes. This sequence is necessary to pre-improve capillary blood flow and reduce the risk of pathological cell sequestration.
Administration technique for severe conditions
The rate of fluid administration directly depends on the severity of the patient's condition. If acute blood loss is massive, preparations are administered rapidly as a bolus, engaging one, two, or even three veins simultaneously if necessary.
Reducing the speed and switching to a more gradual, drip administration is permitted only after hemodynamic stabilization—the benchmark is a confident rise in systolic blood pressure (SBP) above the mark of 80 mmHg.
Calculation of therapy volumes and composition
The quantity and qualitative composition of administered solutions depend on the percentage of lost circulating blood volume (CBV). The higher the deficit, the larger the percentage of this deficit that must be transfused to the patient for compensation.
| CBV deficit | Replacement volume | Approximate volume | Composition of media |
|---|---|---|---|
| Up to 15% | 100% of the deficit | 800–1000 mL | Crystalloids (80%) + Colloids (20%) |
| From 15% to 25% | 150% of the deficit | 1500–2300 mL | Crystalloids, colloids, and plasma in a 4:4:2 ratio |
| From 25% to 35% | 180–220% | 2700–4000 mL | Crystalloids (30%), Colloids (20%), Plasma (30%), Red blood cells (20%) |
| More than 35% | 220% | 4000–6000 mL | Crystalloids (20%), Colloids (30%), Plasma (25%), Red blood cells (25%) |
It is important to note that the transfusion of blood products proper becomes absolutely indicated when blood loss exceeds 35–40% of CBV, as targeted correction of developing anemia and hypoproteinemia is required at this stage.
Additional pharmacological correction
In addition to restoring fluid volume, the body needs correction of concomitant metabolic disorders:
- Combating acidosis. Sodium bicarbonate or trometamol is used to balance the acid-base state.
- Vascular tone management. The use of vasoconstrictors (vasopressors) is strictly contraindicated until CBV is fully restored. Their early administration will only increase spasm and critically exacerbate tissue hypoxia. However, the administration of glucocorticoids is indicated: they help relieve peripheral vascular spasm and have a positive effect on myocardial function.
- Improving oxygenation. Oxygen therapy is mandatory for patients. Hyperbaric oxygenation can be used as an additional measure, but strictly after the source of bleeding has been reliably stopped.
Briefly: answers to topical questions
Which specific crystalloid solutions are used to restore CBV?
Various salt solutions allowing rapid administration are used to restore circulating blood volume. Specific crystalloid solutions include:
- Isotonic sodium chloride solution (0.9%) — used for major blood loss.
- Ringer's solution and Ringer-Locke solution.
- Sodium acetate + sodium chloride (Disol).
- Sodium acetate + sodium chloride + potassium chloride.
- Dextrose solution (5%).
The disadvantage of these media is that only about 25% of the administered volume remains in the bloodstream.
Which clinical and laboratory criteria indicate adequate restoration of CBV?
A set of clinical and laboratory parameters is used to monitor therapy and assess the state of circulation. The main criteria include:
- Hemodynamic parameters — measurement of blood pressure (BP), pulse, central venous pressure (CVP), and shock index (Allgöwer index).
- Clinical signs — assessment of general condition, respiratory rate, and skin color.
- Diuresis — hourly monitoring of urine output.
- Laboratory parameters — determination of hemoglobin, hematocrit, and blood electrolyte levels.
Direct determination of circulating blood volume (CBV) is also performed.
What complications are typical for massive blood transfusion in acute blood loss?
Massive blood transfusion leads to a specific syndrome caused by the administration of large volumes of donor blood. Characteristic complications include:
- Citrate intoxication — causes hypocalcemia, tremor, convulsions, arrhythmia, decreased BP, and in severe cases, pulmonary and cerebral edema.
- Cardiovascular overload — occurs due to massive fluid administration.
- DIC (Disseminated Intravascular Coagulation) — leads to the depletion of clotting factors and bleeding.
- Metabolic disorders — accumulation of breakdown products (potassium, ammonia) in the plasma.
- Hypothermia — a consequence of administering refrigerated blood.
The vascular tone rule: «Fill the bed first, then constrict!». Vasopressors administered in the setting of uncompensated circulating blood volume (CBV) is a direct path to fatal hypoxia.
Class and exam questions
Why is it wrong to immediately transfuse packed red blood cells in blood loss?
The body reacts to a drop in plasma volume much more acutely than to the loss of erythrocytes themselves. Administering plasma expanders prior to blood products is necessary to restore capillary blood flow and prevent cell sequestration.
At what blood pressure can rapid bolus infusion be stopped?
The infusion rate can be reduced and switched to a drip only when systolic blood pressure stably exceeds 80 mm Hg.
When is hyperbaric oxygen therapy initiated?
Active oxygenation methods, including hyperbaric oxygenation, are used exclusively after ongoing bleeding has been definitively stopped.
What else to study on this topic
- Mechanisms and stages of hemorrhagic shock development
- Comparative characteristics of colloids and crystalloids
- Pathophysiology of microcirculation in acute hypovolemia
- Criteria for the efficacy of infusion-transfusion therapy
- Methods of surgical and conservative control of bleeding
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