Hypovolemic💧🩸Shock


Hypovolemic shock is a life-threatening condition that occurs when there is a significant loss of blood or fluids from the body, leading to inadequate circulating volume and insufficient perfusion of tissues and organs. This sudden drop in volume disrupts your body’s ability to deliver oxygen and nutrients to vital organs, potentially leading to organ failure and death.

Hypovolemic shock is circulatory failure due to effective intravascular volume loss (fluids or blood). This effective circulatory volume loss leads to tissue hypoperfusion and tissue hypoxia. If left untreated, hypovolemic shock can lead to ischemic injury of vital organs, leading to multiorgan failure (MOF). (NCBI, 2023)

Types of Hypovolemic shock

The root cause is a rapid loss of fluids, exceeding 15-20% of your total blood volume. Hypovolemic shock can be categorised into two main types based on the cause of fluid loss:

  1. Hemorrhagic Shock:
    • Cause: Significant blood loss due to trauma, surgery, gastrointestinal bleeding, or ruptured aneurysms, (Ectopic pregnancy rupture)
    • Effect: Decreased blood volume leads to reduced oxygen-carrying capacity and inadequate tissue perfusion.
  2. Non-Hemorrhagic Shock:
    • Cause: Loss of fluids due to severe dehydration, burns, vomiting, diarrhoea, high stoma output or third-spacing (fluid shifts into interstitial spaces).
      • Third-Space Loss: Conditions such as burns, pancreatitis, or peritonitis can cause fluids to shift from the vascular compartment to the interstitial spaces.
      • Burns: Severe burns can lead to significant fluid loss through damaged skin. Fluid loss can be substantial enough to cause hypovolemic shock, especially if more than 15% of the total body surface area is affected.
    • Effect: Reduced plasma volume leading to decreased venous return and cardiac output.

Pathophysiology

  1. Volume Status Decrease:
  • The volume status continues to decrease.
  • When it drops to 25-30% of the effective blood volume, the patient enters a shock state. symptoms include:
    • Drop in systolic blood pressure.
    • Tachycardia (rapid heartbeat).
    • Oliguria (reduced urine output).

2. Oxygen Delivery Issue & Metabolic Switch

  • Oxygen delivery to vital organs cannot meet the oxygen demand.
  • Cells switch from aerobic (oxygen-using) to anaerobic (non-oxygen-using) metabolism.
  • This switch leads to the production of lactic acid, causing lactic acidosis.

3. Sympathetic Response:

  • The body’s sympathetic drive increases.
  • Blood flow is diverted from less vital organs to the heart and brain to preserve their function.

4. Tissue Ischemia & Progression to Severe Conditions

  • This diversion of blood flow leads to tissue ischemia (lack of blood supply) in other organs. Tissue ischemia worsens lactic acidosis.
  • If untreated, the condition worsens. This leads to hemodynamic compromise (poor blood circulation)
  • Causes refractory acidosis (persistent acidity). This results in a further reduction in cardiac output (the heart’s ability to pump blood).

5. Outcome:

  • Ultimately leads to multiorgan failure (MOF).
  • If still untreated, it results in death.

Types of Fluid Loss:

  • Intravascular Fluid Loss: This occurs when blood or plasma is lost from the circulatory system, leading to a decrease in blood volume.
  • Extracellular Fluid Loss: This can occur due to severe dehydration or burns where fluid is lost from the interstitial spaces or extracellular compartment.
  • Intracellular Fluid Loss: Generally less relevant in hypovolemic shock, as the immediate concern is usually the loss of extracellular or intravascular fluids

Identification:
Early recognition of hypovolemic shock is essential for effective treatment. Identification involves clinical assessment and diagnostic testing:

  1. Clinical Symptoms:
  • Rapid heart rate (tachycardia)
  • Low blood pressure (hypotension)
  • Rapid, shallow breathing (tachypnoea)
  • Cold, clammy skin,
  • Confusion or altered mental state
  • Reduced urine output (oliguria)

2. Physical Examination:

  • Signs of poor perfusion (e.g., cyanosis, pallor)
  • CRT is usually prolonged
  • Weak peripheral pulses
  • Dry mucous membranes (in dehydration)

3. Diagnostic Tests:

  • Haemoglobin and Haematocrit: To assess the degree of blood loss. Low levels indicate significant blood loss, which can be quantified to determine the severity of hypovolemia.
  • Electrolytes and Renal Function Tests: To evaluate dehydration and renal function. Patients may experience elevated BUN and serum creatinine levels due to prerenal kidney failure. Additionally, they can develop hypernatremia or hyponatremia, as well as hyperkalemia or hypokalemia
    • urine sodium- In patients with hypovolemia and normal kidney function, urine sodium levels are typically less than 20 (mEq/L). This is because sodium reabsorption occurs, which can help differentiate between hypovolemia and other causes of hyponatremia.
  • Arterial Blood Gases: To assess oxygenation, acid-base balance, and lactate levels. Elevated lactate levels indicate anaerobic metabolism due to inadequate perfusion. & VBG from Internal jugular to access Scvo2 status.
  • Imaging (Ultrasound or CT Scans): To identify sources of internal bleeding or fluid loss.
  • Urine Output Monitoring: Reduced output is a key indicator of inadequate renal perfusion and hypovolemia.

Management:
Management of hypovolemic shock focuses on rapid fluid resuscitation, restoring blood volume, and addressing the underlying cause:

  1. Initial Stabilisation:
  • Fluids/Blood Resuscitation:
    • Fluid Resuscitation: Administer isotonic crystalloids (e.g., normal saline or Plasmolyte) rapidly to restore circulating volume. For example, an adult patient might require an initial bolus of 1-2 liters of crystalloids.
      • Lidco monitoring can be used for fluid responsiveness
    • Blood Products: Blood products may be necessary for haemorrhagic shock. (Emergency haemorrhage protocol can be activated after consulting senior staff or a consultant from the blood bank.
      • ROTEM testing to identify the required blood product if the situation allows
  • Vasopressors: Generally avoided initially in favour of fluid resuscitation but may be used if blood pressure remains low despite adequate volume replacement.

2. Addressing Underlying Cause:

  • Control Haemorrhage: Apply direct pressure, surgical intervention, or endoscopic techniques to stop bleeding.
  • Treat Dehydration: Administer oral or intravenous fluids to correct fluid deficits. For example, patients with severe dehydration may need significant volumes of IV fluids.
  • Manage Burns or Third-Space Loss: Provide appropriate fluid resuscitation and address the underlying condition. The Parkland formula is often used to calculate fluid requirements for burn patients: 4 mL/kg/%TBSA burn in the first 24 hours.

3. Ongoing Monitoring and Support:

  • Haemodynamic Monitoring: Continuous monitoring of blood pressure, heart rate, and urine output to assess response to treatment.
  • Laboratory Monitoring: Regular checks of haemoglobin, electrolytes, and lactate levels to guide ongoing management.
  • Monitoring for Complications: Watch for signs of organ dysfunction, such as acute kidney injury or metabolic acidosis, which require immediate attention.

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