Complications of Blood Loss

Acute blood loss and hemorrhagic shock

Massive bleeding from large vessels or cardiac chambers causes acute post-hemorrhagic anemia (usually normochromic) and a critical decrease in circulating blood volume (CBV).

The decrease in CBV triggers a cascade of reactions leading to hemorrhagic shock:

• Compensated stage: reduced venous return and cardiac output stimulate catecholamine release. Peripheral vasoconstriction occurs (centralization of blood circulation), which temporarily maintains hemodynamics.
• Decompensated stage: compensatory mechanisms become depleted, tissue hypoxia and metabolic acidosis progress.
• Irreversible stage: disseminated intravascular coagulation (DIC) and multiple organ dysfunction syndrome (MODS) develop.

Clinically, severe shock manifests as absent peripheral pulses, a drop in blood pressure to unmeasurable levels, and suppressed diuresis (oliguria or anuria). Without emergency blood volume restoration, circulatory collapse and cardiac arrest ensue. An important tactical point: in ongoing internal bleeding, surgery is performed immediately, without waiting for the patient to be resuscitated from shock.

Complications from blood accumulation

Extravasated blood can mechanically compress organs or serve as a medium for microorganism proliferation:

1. Tamponade of cavities. Blood in a confined space impairs organ function. Hemoperricardium causes cardiac tamponade — diastolic myocardial filling is blocked, cardiac output drops sharply, requiring emergency pericardiocentesis. Massive hemothorax leads to lung compression and respiratory failure.
2. Secondary infection. Hematomas and cavity blood accumulations are easily infected. For instance, hemothorax can transform into purulent pleural empyema if infection penetrates through damaged tissues.
3. Compression of structures. A hematoma in a restricted space (e.g., in the brain) destroys and shifts surrounding tissues, leading to severe neurological deficit or death.
4. Two-stage rupture. Typical for aortic aneurysms. The primary wall tear is temporarily sealed by a thrombus (first stage), but with a rise in blood pressure, the thrombus dislodges, resulting in fatal profuse bleeding (second stage).

Chronic blood loss

Unlike acute blood loss, chronic blood loss is characterized by prolonged loss of small blood volumes (in peptic ulcer disease, hemorrhoids, heavy menstruation).

It leads to the development of chronic post-hemorrhagic anemia. Since iron stores are depleted, the anemia is hypochromic. Clinically, this is accompanied by trophic disorders of the skin and mucous membranes, but without pronounced hypovolemia and the risk of shock characteristic of acute situations.

Outcomes of hemorrhage

The consequences of hemorrhage are divided into favorable and unfavorable.

Favorable outcomes:

• Cessation of bleeding (thrombosis, vascular spasm, medical intervention) and resorption of blood.
• Organization of the hematoma — replacement with scar tissue or formation of a connective tissue capsule.
• Formation of a pseudocyst at the site of the hematoma (frequently found in the brain).

Unfavorable outcomes:

• Fatal outcome due to hemorrhagic shock or acute massive blood loss.
• Death from acute heart failure in cardiac tamponade.
• Suppuration of accumulated blood (formation of abscesses, empyema).
• Destruction of vital organs due to compression by an enlarging hematoma.
• Terminal multiple organ failure due to progressive hypoxia.

Class and exam questions

What else to study on this topic

• Pathogenesis of multiple organ failure in shock
• Morphological changes in target organs ("shock kidney", "shock lung")
• DIC syndrome: stages and mechanisms of consumption coagulopathy
• Differences in the pathogenesis of hemorrhagic, cardiogenic, and septic shock
• Compensation mechanisms in acute blood loss

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.