Lecture Notes: Types of Shock

Introduction to Shock

• Shock is a condition characterized by inadequate tissue perfusion.
• Results in insufficient oxygen delivery to tissues, leading to ischemia and potentially necrosis and organ failure.
• Shock can progress through stages:
  • Compensating stages: Body tries to maintain blood pressure.
  • Progressive stage: Decline in condition.
  • Refractory stage: Critical and potentially irreversible condition.

Causes of Shock

• Low blood pressure due to:
  • Decreased cardiac output.
  • Decreased systemic vascular resistance (SVR).

Hypovolemic Shock

• Caused by low blood volume.
• Blood loss causes:
  • GI bleed (e.g., peptic ulcer).
  • Abdominal aortic aneurysm.
  • Trauma.
  • Postpartum hemorrhage.
  • Ectopic pregnancy.
  • Hemoptysis.
• Non-blood fluid loss causes:
  • Severe burns.
  • Excessive vomiting or diarrhea.
  • Bowel obstructions.
  • Acute pancreatitis.
  • Diabetic ketoacidosis.
• Compensation and Symptoms:
  • Baroreceptors stimulate heart contractility and heart rate.
  • Increased systemic vascular resistance.
  • Tachycardia.
  • High or low hematocrit levels (hemoconcentration vs. blood loss).
  • Cyanosis due to hypoxia.
• Treatment:
  • Fluid resuscitation with crystalloids (e.g., normal saline).
  • Monitor for hypothermia.
  • Control hemorrhage, possibly requiring transfusion.
  • Support renal mechanisms with renin-angiotensin-aldosterone system.

Cardiogenic Shock

• Heart unable to pump sufficient blood.
• Causes:
  • Myocarditis.
  • Severe myocardial infarctions.
  • Valve dysfunctions (e.g., aortic stenosis).
  • Arrhythmias (tachyarrhythmias/bradyarrhythmias).
  • Dilated cardiomyopathy.
  • Congenital heart diseases.
• Symptoms:
  • Low cardiac output, low blood pressure, hypotension.
  • Tachycardia.
  • Increased systemic vascular resistance.
  • Lactic acidosis due to anaerobic metabolism.
• Treatment:
  • Oxygen therapy.
  • Limited isotonic fluids.
  • Vasopressors (e.g., epinephrine, dobutamine).
  • Treat underlying cause (e.g., thrombolytics for MI).

Obstructive Shock

• Caused by barrier to blood flow from or to the heart.
• Types and Causes:
  • Tension Pneumothorax:
    • Air enters pleural cavity, compressing the heart and vessels.
    • Causes mediastinal or tracheal shift.
    • Symptoms include hyper-resonance, decreased breath sounds, jugular venous distention.
  • Pericardial Tamponade:
    • Fluid accumulates in pericardial cavity, compressing the heart.
    • Beck's triad: high jugular venous pressure, hypotension, muffled heart sounds.
  • Massive Pulmonary Embolism:
    • Embolus blocks pulmonary artery, decreasing blood flow.
    • Causes hypotension, hypoxia, respiratory distress.
  • Proximal Aortic Dissection:
    • Affects heart's blood supply and ejection ability.
• Treatment:
  • Dependent on cause: needle decompression, pericardiocentesis, thrombolytics, surgical interventions.
  • General: Oxygen, isotonic fluids, vasopressors.

Conclusion

• Discussed types of shock related to decreased cardiac output and high systemic vascular resistance.
• Next topic: Distributive shock and its impact on systemic vascular resistance.

Note: This lecture focused on understanding the causes, symptoms, and treatments of different types of shock, emphasizing the importance of timely recognition and intervention.