Acute Hemorrhage

Overview of Acute Hemorrhage

Definition: Sudden and significant blood loss occurring over a short period of time
Pathophysiology:
- Rapid loss of blood volume leads to decreased oxygen delivery to tissues
- The body compensates through various mechanisms, including increased heart rate, vasoconstriction, and fluid shifts
- If blood loss is severe and/or compensation is inadequate, hypovolemic shock and organ damage can occur
Key Considerations:
- The initial laboratory findings may not reflect the severity of blood loss due to the proportional loss of all blood components (RBCs, WBCs, platelets, and plasma).
- Changes in laboratory values (e.g., decreased HGB and HCT) become apparent as the body attempts to restore blood volume through fluid shifts
Classification:
- External Hemorrhage: Blood loss visible outside the body (e.g., trauma, surgery)
- Internal Hemorrhage: Blood loss within the body (e.g., gastrointestinal bleeding, ruptured ectopic pregnancy, ruptured aneurysm)

Causes of Acute Hemorrhage

Trauma:
- Accidents
- Surgery
- Gunshot wounds
- Stabbing injuries
Gastrointestinal Bleeding:
- Peptic ulcers
- Esophageal varices
- Diverticulosis
- Colorectal cancer
Obstetrical and Gynecological Causes:
- Ectopic pregnancy rupture
- Postpartum hemorrhage
- Placenta previa or abruption
Vascular Rupture:
- Aortic aneurysm rupture
- Arteriovenous malformation (AVM) rupture
Coagulation Disorders:
- Hemophilia
- Von Willebrand disease
- Disseminated intravascular coagulation (DIC)
- Anticoagulant medication overdose

Clinical Manifestations

Symptoms Depend on the Severity and Rate of Blood Loss:
- Mild Blood Loss (Up to 15% of Blood Volume):
  - May be asymptomatic
  - Mild lightheadedness or dizziness
- Moderate Blood Loss (15-30% of Blood Volume):
  - Tachycardia (increased heart rate)
  - Tachypnea (increased respiratory rate)
  - Pallor (pale skin)
  - Diaphoresis (sweating)
  - Orthostatic hypotension (drop in blood pressure upon standing)
- Severe Blood Loss (30-40% of Blood Volume):
  - Marked tachycardia and tachypnea
  - Hypotension (low blood pressure)
  - Restlessness or anxiety
  - Oliguria (decreased urine output)
  - Cool, clammy skin
- Life-Threatening Blood Loss ( >40% of Blood Volume):
  - Severe hypotension
  - Altered mental status (confusion, lethargy)
  - Anuria (no urine output)
  - Loss of consciousness
  - Shock (hypovolemic shock)
Signs of Internal Hemorrhage:
- Abdominal pain and distension
- Chest pain
- Back pain
- Blood in the stool (melena or hematochezia)
- Vaginal bleeding

Laboratory Findings

Complete Blood Count (CBC):
- Initial CBC may appear normal! This is because all blood components (RBCs, WBCs, platelets, and plasma) are lost proportionally
- Changes become apparent as the body attempts to restore blood volume:
  - Hemoglobin (HGB): Decreases over time (usually within hours) as fluid shifts occur
  - Hematocrit (HCT): Decreases over time (HCT lags behind HGB changes)
  - Red Blood Cell Count (RBC): Decreases over time
  - Mean Corpuscular Volume (MCV): Initially normal (normocytic) but may become microcytic over time if chronic blood loss leads to iron deficiency
  - Platelet Count: May initially increase due to splenic contraction, but can decrease with prolonged bleeding or consumptive coagulopathy (DIC)
  - White Blood Cell Count (WBC): May initially increase due to stress response
Reticulocyte Count:
- Increases within 2-3 days as the bone marrow responds to the anemia
- Peaks at 7-10 days
Coagulation Studies:
- Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT): Usually normal initially unless there is an underlying coagulation disorder or consumptive coagulopathy (DIC)
- Fibrinogen: May be normal or decreased (in DIC)
- D-dimer: May be elevated (especially if there is associated activation of the coagulation system or fibrinolysis)
Iron Studies:
- Initially normal
- With chronic blood loss, iron deficiency can develop, leading to:
  - Low serum iron
  - High Total Iron-Binding Capacity (TIBC)
  - Low Transferrin Saturation
  - Low Ferritin
Other Tests:
- Stool occult blood test: To detect gastrointestinal bleeding
- Blood type and crossmatch: To prepare for potential blood transfusions
- Imaging studies (e.g., CT scan, ultrasound, angiography): To identify the source of bleeding

Compensatory Mechanisms in Response to Acute Hemorrhage

Vasoconstriction:
- Activation of the sympathetic nervous system causes constriction of blood vessels, helping to maintain blood pressure
- Shunts blood flow to vital organs (e.g., heart, brain)
Increased Heart Rate (Tachycardia):
- Increases cardiac output to compensate for reduced blood volume
Fluid Shifts:
- Movement of interstitial fluid into the vascular space to increase blood volume
- This hemodilution leads to a decrease in HGB and HCT
Hormonal Responses:
- Release of antidiuretic hormone (ADH) from the pituitary gland, promoting water retention by the kidneys
- Activation of the renin-angiotensin-aldosterone system (RAAS), leading to sodium and water retention and vasoconstriction
Increased Erythropoiesis:
- Kidneys sense decreased oxygen delivery and increase production of erythropoietin (EPO)
- EPO stimulates the bone marrow to increase RBC production, leading to reticulocytosis

Treatment of Acute Hemorrhage

Assess the Severity of Blood Loss:
- Evaluate vital signs (heart rate, blood pressure, respiratory rate)
- Assess mental status and urine output
Stop the Bleeding:
- Apply direct pressure to external wounds
- Surgical intervention may be needed to control internal bleeding
Restore Blood Volume and Oxygen-Carrying Capacity:
- Intravenous Fluids:
  - Crystalloids (e.g., normal saline, lactated Ringer’s solution) to restore blood volume
- Blood Transfusions:
  - Packed red blood cells (PRBCs) to increase hemoglobin and improve oxygen delivery
  - Transfusion triggers depend on the patient’s clinical condition and underlying comorbidities
    - Typically, transfuse when HGB < 7 g/dL or if the patient is symptomatic (e.g., chest pain, shortness of breath)
    - Higher transfusion thresholds may be used in patients with cardiac or pulmonary disease
  - Consider other blood products as needed:
    - Platelets for thrombocytopenia or platelet dysfunction
    - Fresh frozen plasma (FFP) for coagulation factor deficiencies
    - Cryoprecipitate for fibrinogen deficiency
Address Underlying Cause:
- Treat peptic ulcers, esophageal varices, or other sources of bleeding
- Correct coagulation disorders
Monitor for Complications:
- Hypovolemic shock
- Acute respiratory distress syndrome (ARDS)
- Acute kidney injury (AKI)
- Disseminated intravascular coagulation (DIC)

Key Laboratory Findings

Initial CBC may appear normal!
Decreasing HGB and HCT over time
Elevated reticulocyte count (after 2-3 days)
Normal coagulation studies (unless there is an underlying coagulopathy)
Normal iron studies initially, but may show iron deficiency with chronic blood loss

Key Terms

Acute Hemorrhage: Sudden and significant blood loss
Hypovolemic Shock: Shock due to decreased blood volume
Tachycardia: Increased heart rate
Tachypnea: Increased respiratory rate
Orthostatic Hypotension: Drop in blood pressure upon standing
Reticulocyte Count: Measure of new red blood cell production
Blood Transfusion: Infusion of blood products to restore blood volume and oxygen-carrying capacity

Hypoproliferative

Macrocytic