Classification and Types
Bleeding can be external (into the external environment) or internal (into body cavities or the lumen of hollow organs). When escaped blood accumulates in surrounding tissues, it is termed a hemorrhage. In isolated hemorrhages, systemic hemodynamics typically remain unaffected due to the small volume of lost blood.
Types of tissue hemorrhages:
- Hematoma — accompanied by tissue disruption and the formation of a cavity filled with blood.
- Hemorrhagic imbibition (infiltration) — tissue structure is preserved. On the skin and mucous membranes, it manifests as petechiae (less than 3 mm in diameter) and ecchymoses (greater than 3 mm).
Based on the source, bleeding is classified as arterial, venous, capillary, or mixed. Based on timing, it is divided into primary (immediately after trauma) and secondary (delayed).
The severity of the condition directly correlates with the proportion of lost circulating blood volume (CBV):
- Mild degree: up to 20–25% CBV. Usually not life-threatening and compensated by emergency mechanisms.
- Moderate degree: 25–35% CBV. Causes significant central hemodynamic and microcirculatory disorders.
- Severe degree: greater than 35–40% CBV.
Reactivity Factors
The clinical course of the pathological process depends on individual patient characteristics. Studies show that women and adults tolerate blood loss better than men and children.
Condition of the organism also plays a critical role. Extreme temperature exposures (hypothermia or hyperthermia), as well as deep general anesthesia, depress compensatory mechanisms and exacerbate vital function disorders. Additionally, a decrease in clotting factors or hyperactivation of the fibrinolytic system increases the rate and total volume of blood loss.
Compensatory Mechanisms
To counteract hypovolemia, the body activates four groups of mechanisms. They are triggered at different times but operate concurrently, reinforcing one another.
1. Cardiovascular Stage (First Seconds) Immediate cardiac stimulation occurs: heart rate and stroke volume increase. Centralization of blood flow develops — a selective alteration in vascular tone. Arterioles in peripheral tissues (skin, muscles, kidneys) constrict, while vessels of vital organs (brain, heart) dilate. Arteriolar spasm forces pooled blood into the active circulation, maintaining CBV.
2. Hydremic Stage (First Minutes) Aiming to shift fluid from tissues into blood vessels. The reduction in CBV is detected by baroreceptors, prompting the secretion of ADH (vasopressin).
- ADH stimulates aquaporin-2 water channels in the kidneys, enhancing water reabsorption.
- Simultaneously, ADH constricts the renal afferent arterioles, causing ischemia of the juxtaglomerular apparatus (JGA) and activating the renin-angiotensin-aldosterone system (RAAS).
- Angiotensin II increases vascular tone and stimulates aldosterone release, which promotes sodium retention. Plasma hyperosmolality further drives ADH production.
Fluid shifts down an osmotic gradient from cells into the interstitium, then into lymph and blood. By days 2–3, oligocythemic hypo- or normovolemia develops.
3. Protein Stage (After Several Hours) Protein synthesis is activated in the liver. Plasma protein composition is restored, and procoagulants are produced to thrombose the vascular defect. Signs of elevated synthesis persist for up to 1.5–3 weeks.
4. Bone Marrow Stage Triggered in response to mixed hypoxia: emic (low red blood cell count), circulatory (impaired blood flow), and respiratory (reduced pulmonary perfusion). Activation of hematopoiesis eliminates the deficit of formed elements.
Principles of Therapy
Treatment is based on two main principles:
- Etiotropic: removal of the cause. Includes surgical hemostasis (restoring the integrity of the vessel wall) and pharmacological enhancement of blood coagulation.
- Pathogenetic: blockade of pathogenic links (the cornerstone of management).
- Restoration of CBV to resolve macrocirculatory disorders. Blood transfusions, plasma, and medium-molecular-weight dextrans (Poliglyukin, Hemodez) are utilized.
- Normalization of transcapillary exchange to eliminate microcirculatory disturbances. Low-molecular-weight dextrans (Reopoliglyukin), gelatin, and isotonic saline are applied.
- Correction of homeostasis — elimination of water, electrolyte, and protein imbalances.