Pharmacology of Drugs Acting on the Cardiovascular System

• Understand the Pharmacology of Drugs Acting on the Cardiovascular System to explore anti-hypertensives, diuretics, and cardiac drugs.
• Pharmacology of Drugs Acting on the Cardiovascular System covers agents that influence heart rate, blood pressure, and vascular tone.

Shock

Pathophysiology

1. Initial Stage – Compensatory mechanisms (tachycardia, vasoconstriction) maintain perfusion.
2. Progressive Stage – Oxygen delivery fails → Anaerobic metabolism → Lactic acidosis → Cell dysfunction.
3. Irreversible Stage – Multi-organ failure → Death if untreated.

Types of Shock

1. Hypovolemic Shock (Volume Loss):

   • Cause: Severe blood or fluid loss (e.g., hemorrhage, burns, diarrhea, vomiting).
   • Mechanism: Reduced preload (venous return) → ↓ Stroke volume → ↓ Cardiac output.

2. Cardiogenic Shock (Pump Failure):

   • Cause: Heart dysfunction (e.g., myocardial infarction, arrhythmias, myocarditis).
   • Mechanism: Inability of the heart to pump blood effectively → ↓ Cardiac output.

3. Distributive Shock (Vasodilation):

   • Septic Shock: Caused by severe infection and systemic inflammation.
   • Anaphylactic Shock: Allergic reaction causing massive histamine release and vasodilation.
   • Neurogenic Shock: Spinal cord or brain injury causing loss of vascular tone.
   • Mechanism: Peripheral vasodilation → ↓ Systemic vascular resistance → Inadequate perfusion.

4. Obstructive Shock (Blocked Circulation):

   • Cause: Physical obstruction (e.g., pulmonary embolism, cardiac tamponade, tension pneumothorax).
   • Mechanism: Impaired blood flow → ↓ Cardiac output.

Symptoms

General Symptoms:

• Hypotension, tachycardia, cold/clammy skin (warm in distributive shock), altered mental status, oliguria, weak pulse, rapid breathing.

Specific Symptoms:

• Hypovolemic: Dry mucous membranes, reduced skin turgor, flat neck veins.
• Cardiogenic: Chest pain, lung crackles, distended neck veins.
• Septic: Early fever/flushed skin, later cool/mottled skin.
• Anaphylactic: Hives, angioedema, stridor, wheezing.
• Neurogenic: Bradycardia, warm dry skin, paralysis below injury.

Diagnosis

1. Clinical Assessment: Vital signs, skin color, capillary refill.
2. Laboratory Tests:
   • Elevated lactate, metabolic acidosis (ABG).
   • CBC, electrolytes, renal function.
3. Imaging: Chest X-ray, CT, ultrasound for causes.
4. Hemodynamic Monitoring: CVP, pulmonary artery catheterization.

Treatment

General Management:

• Airway: Secure airway, intubation if needed.
• Breathing: Oxygen or ventilation.
• Circulation: IV fluids, vasopressors.

Specific Treatments:

• Hypovolemic: IV crystalloids, blood transfusion if hemorrhage.
• Cardiogenic: Inotropes, diuretics, revascularization (PCI/CABG).
• Septic: Antibiotics, IV fluids, vasopressors, corticosteroids if refractory.
• Anaphylactic: IM epinephrine, antihistamines, corticosteroids, airway support.
• Neurogenic: IV fluids, vasopressors, spinal stabilization.
• Obstructive: Pericardiocentesis, chest tube, thrombolytics/embolectomy.

Prognosis and Complications

• Prognosis: Depends on type, cause, and timely intervention. Early treatment improves outcomes.
• Complications: Multi-organ dysfunction syndrome (MODS), ARDS, renal failure, death if untreated.

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