DA

Shock, Sepsis, SIRS, MODS

Shock is a syndrome marked by decreased tissue perfusion and impaired cellular metabolism, an imbalance between the supply and demand of oxygen and nutrients.

Types of Shock

  • Cardiogenic: Systolic or diastolic dysfunction leading to decreased cardiac output (CO), often due to myocardial infarction (MI). Manifestations include tachsirsycardia, hypotension, crackles, and cool, clammy skin. Treatment focuses on restoring myocardial oxygen supply/demand, cardiac catheterization, and hemodynamic or mechanical support.

  • Hypovolemic: Inadequate intravascular volume, from absolute (hemorrhage, GI losses) or relative (third-spacing) loss. Compensatory mechanisms work up to \sim 15\% of total blood volume (TBV) loss; \ge 30\% (TBV) loss risks autoregulation failure. Manifestations: tachycardia, decreased preload/CO, cool/clammy skin. Treatment is primarily volume expansion.

  • Distributive Shock: Abnormal distribution of blood flow due to widespread vasodilation.

    • Neurogenic: Loss of sympathetic nervous system (SNS) vasoconstrictor tone causes massive vasodilation, pooling of blood, bradycardia, and hypotension. Treatment involves spinal precautions, vasopressors to maintain \text{BP}, and cautious fluid resuscitation.

    • Anaphylactic: Rapid, massive vasodilation and increased capillary permeability mediated by inflammatory substances, posing a high risk of airway compromise. Manifestations: dyspnea, angioedema, hypotension, urticaria. Treatment: IM epinephrine (first-line), antihistamines, and IV fluids.

    • Septic: An infection triggers an exaggerated inflammatory response, leading to endothelial injury, vasodilation, and capillary leak. Clinical signs include fever or hypothermia, tachycardia, and hypotension, with warm flushed skin early on.

  • Obstructive Shock: Physical obstruction to blood flow causing decreased \text{CO}. Causes include tamponade, tension pneumothorax, and pulmonary embolism (PE). Treatment involves relieving the obstruction.

Stages of Shock

  1. Initial: Cellular-level changes, metabolism shifts to anaerobic, lactic acid buildup.

  2. Compensatory: \text{SNS} and hormonal responses attempt to restore perfusion; \text{BP} is maintained.

  3. Progressive: Compensatory mechanisms fail, organ perfusion worsens, requiring intensive monitoring.

  4. Refractory: Severe, pervasive hypoperfusion, multi-organ failure, profound hypotension, with a high likelihood of death.

SIRS and MODS

  • SIRS (Systemic Inflammatory Response Syndrome): A systemic inflammatory response to various insults (infection, ischemia, injury). Diagnostic criteria include abnormal temperature (T), heart rate (HR), respiratory rate (RR), white blood cell count (WBC), or signs of organ dysfunction (e.g., \text{SBP} < 90\,\text{mmHg} or lactate \ge 2\,\text{mmol/L}).

  • MODS (Multiple Organ Dysfunction Syndrome): Failure of two or more organ systems in an acutely ill patient, progressing from SIRS, where homeostasis cannot be maintained without intervention.

Sepsis and Septic Shock

  • Sepsis: Infection with a dysregulated host response leading to new organ dysfunction.

  • Septic shock: Sepsis patients with persistent hypotension despite adequate fluid resuscitation and/or inadequate tissue perfusion.

  • Surviving Sepsis Campaign: Hour-1 Bundle: Key elements include measuring lactate, obtaining blood cultures, administering broad-spectrum antibiotics, rapid 30\,\text{mL/kg} crystalloid for hypotension or lactate \ge 4\,\text{mmol/L}, applying vasopressors to maintain \text{MAP} \ge 65\,\text{mmHg} if hypotensive, and remeasuring lactate.

  • Treatment goals: Restore intravascular volume and organ perfusion, administer vasopressors (norepinephrine first-line), broad-spectrum antibiotics within 1 hour, source control, and vigilant glucose control (< 180\,\text{mg/dL}).

Nursing Management of Shock

  • Assessment: Monitor airway, responsiveness, signs of decreased perfusion, vitals, and urine output.

  • Fluid Resuscitation: Choice based on shock type; crystalloids, colloids, or blood products to achieve adequate circulating volume and \text{MAP} \ge 65\,\text{mmHg}.

  • Drug Therapy: Vasopressors (e.g., norepinephrine) aim to correct decreased tissue perfusion and maintain \text{MAP} \ge 65\,\text{mmHg} after fluid resuscitation.

  • Nutritional Therapy: Initiate enteral feeding within the first 24 hours.

  • Glycemic Control: Target blood glucose \le 180\,\text{mg/dL}.

Quick Reference Summary

  • Key definitions: SIRS (systemic inflammatory response), MODS (failure of \ge 2 organ systems), Sepsis (infection + organ dysfunction), Septic shock (persistent hypotension despite resuscitation).

  • Critical Numbers: \text{MAP} goal: \ge 65\,\text{mmHg}; fluid resuscitation in sepsis: 30\,\text{mL/kg} crystalloid; lactate threshold for concern: \ge 2\,\text{mmol/L}; enteral feeding: within 24 hours.