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Anemia Due to Acute Blood Loss

Chapter 106 | Part 4 – Oncology: Hematologic Malignancies · Part 4 – Oncology: Hematologic Malignancies · Chapter 106

Key Clinical Points

  1. Three pathophysiologic stages of APHA: Hypovolemia → Hemodilution → Marrow Response.
  2. Clinical status is driven by hypovolemia initially; hemoglobin concentration remains unchanged until fluids are administered.
  3. Volume loss thresholds: >25% (instability), >30% (compensation failure), >40% (>2 L in adults, shock).
  4. Grey Turner and Cullen signs specifically indicate retroperitoneal bleeding.
  5. Plasma is preferred over saline for volume expansion in trauma to preserve clotting factors.
  6. In acute hemorrhage, transfusion takes priority over identifying the source of bleeding.
  7. Compensatory mechanisms include the Bohr effect (2,3-BPG increase) and blood shunting to vital organs.
  8. Hemoglobin <7 g/dL indicates approximately 50% total blood loss.
  9. Dullness to chest percussion suggests intrapleural or peritoneal bleeding.
  10. Bone marrow response (increased reticulocytes/erythropoietin) occurs only after bleeding stops.

DEFINITION & OVERVIEW

• Definition: Anemia Due to Acute Blood Loss (APHA) refers to posthemorrhagic anemia following acute blood loss. • Mechanisms of Anemia: ◦ Direct loss of red cells ◦ Protracted loss depleting iron stores (see Chap. 102) • Types of Blood Loss: ◦ External: Trauma, obstetric hemorrhage ◦ Internal: Gastrointestinal tract bleeding, splenic rupture, ectopic pregnancy rupture, subarachnoid hemorrhage, leaking aneurysm

ETIOLOGY & PATHOPHYSIOLOGY

• Three Clinical/Pathophysiologic Stages: 1. Stage 1: Hypovolemia 2. Stage 2: Hemodilution 3. Stage 3: Bone Marrow Response

• Stage 1 (Hypovolemia): ◦ Primary threat: Organ perfusion (brain, kidneys) ◦ Clinical impact: Loss of consciousness and acute renal failure ◦ Laboratory note: Hemoglobin concentration not affected initially; falls only after fluid administration ◦ Physiological response: Baroreceptors → vasopressin release → fluid shift from extravascular to intravascular compartments

• Stage 2 (Hemodilution): ◦ Correlation: Severity of anemia correlates with blood loss volume ◦ Example: Hemoglobin <7 g/dL → indicates ≈50% total blood loss

• Stage 3 (Bone Marrow Response): ◦ Trigger: Occurs if bleeding stops ◦ Response: Reticulocyte count and erythropoietin levels elevate (similar to hemolysis response)

• Compensatory Mechanisms: ◦ Moderate anemia symptoms: Fatigue, reduced stamina, dyspnea, tachycardia ◦ Bohr effect: 2,3-BPG increase → shifts O2 dissociation curve rightward ◦ Severe anemia: Blood shunting to vital organs ◦ Clinical Note: Hypovolemia dominates initial presentation; Hb/Hct not reflective of blood loss until fluids are administered.

CLINICAL FEATURES

• General Presentation: Symptoms depend on severity and age. Chronic anemia may be asymptomatic until Hb <7–8 g/dL; acute blood loss presents with hypovolemia signs before hemoglobin changes.

• Volume Loss Thresholds: ◦ Mild loss: Bohr effect enhances O2 delivery ◦ 20% blood loss (~1 unit): Often asymptomatic ◦ >25% loss: Signs of vascular instability appear ◦ >30% loss: Compensation failure (postural hypotension, tachycardia) ◦ >40% loss (>2 L in adults): Hypovolemic shock (confusion, dyspnea, diaphoresis, hypotension)

• Physical Exam Findings: ◦ General: Tachycardia, tachypnea, decreased pulse pressure, cold pale/mottled skin, oliguria ◦ Specific signs: Grey Turner sign (flank ecchymosis) and Cullen sign (umbilical ecchymosis) → retroperitoneal bleeding ◦ Percussion: Dullness to chest percussion → intrapleural/peritoneal bleeding.

INVESTIGATIONS & DIAGNOSIS

  1. Initial Clinical Assessment: Evaluate for tachycardia, tachypnea, decreased pulse pressure, cold skin, and oliguria.
  2. Identification of Localizing Signs: ◦ Grey Turner sign (flank ecchymosis) → retroperitoneal bleeding ◦ Cullen sign (umbilical ecchymosis) → retroperitoneal bleeding ◦ Dullness to chest percussion → intrapleural/peritoneal bleeding
  3. Laboratory Correlation: ◦ Monitor hemoglobin: Note that Hb is not affected in Stage 1; an abrupt drop suggests APHA.
  4. Localization of Internal Bleeding: ◦ Perform sonogram or endoscopy to identify specific internal sources.

MANAGEMENT & TREATMENT

  1. Immediate Stabilization: Airway, breathing, and circulation assessments take priority.
  2. Hemodynamic Support: Vasopressors critical in hypotensive bleeding.
  3. Fluid Resuscitation: ◦ Choice: Plasma preferred over saline in trauma ◦ Rationale: Prevents dilution of clotting factors
  4. Blood Replacement: ◦ Priority: Transfusion takes priority over finding the source of bleeding in acute hemorrhage.
  5. Hemorrhage Control: ◦ Secondary priority following initial stabilization and transfusion.

KEY PEARLS & CLINICAL TRAPS

• Clinical Timing: Hypovolemia dominates initially; hemoglobin concentration is not a reliable indicator of blood loss until fluids are administered. • Volume Thresholds: ◦ >25% → Vascular instability ◦ >30% → Compensation failure (postural hypotension, tachycardia) ◦ >40% → Hypovolemic shock (confusion, dyspnea, diaphoresis, hypotension) • Fluid Choice: Plasma preferred over saline in trauma to preserve clotting factors. • Treatment Priority: Transfusion prioritized over source identification in acute hemorrhage. • Diagnostic Markers: Grey Turner and Cullen signs indicate retroperitoneal bleeding; dullness to chest percussion indicates intrapleural/peritoneal bleeding.