Overview
This lecture focuses on obstructive shock, especially due to pulmonary embolism (PE), cardiac tamponade, and tension pneumothorax, covering causes, clinical manifestations, diagnostics, and management.
Obstructive Shock: Causes & Manifestations
- Obstructive shock results from physical blockage of blood flow (e.g., PE, cardiac tamponade, tension pneumothorax).
- Common signs: hypotension (low blood pressure), tachycardia (fast heart rate), and symptoms due to decreased cardiac output.
- PE: shortness of breath, chest pain, tachycardia, anxiety.
- Cardiac tamponade: muffled heart sounds, hypotension, tachycardia.
- Tension pneumothorax: absent breath sounds on affected side, deviated trachea, shortness of breath, tachycardia.
Diagnostics & Treatments by Cause
- PE: treat with anticoagulants.
- Cardiac tamponade: pericardiocentesis (fluid removal from heart sac).
- Tension pneumothorax: needle decompression or chest tube.
- All cases: provide oxygen support and continuous cardiac monitoring.
Pulmonary Embolism: Pathophysiology & Diagnosis
- PE is usually caused by a blood clot from a deep vein thrombosis (DVT) traveling to the lungs.
- PE blocks lung blood flow, causing tissue death, decreased gas exchange, and hypoxia.
- Chest X-ray rules out other causes; V/Q scan for those allergic to contrast or with poor kidneys; pulmonary angiogram (CT with contrast) for vessel imaging.
- Monitor for contrast dye allergies (iodine, shellfish) and kidney function before imaging.
PE: Signs, Symptoms & Management
- Symptoms include chest pain, tachycardia, hypoxia, hypotension, dyspnea, petechiae, anxiety, and syncope.
- IVC (inferior vena cava) filter (Greenfield filter) is used for patients with recurrent PE or multiple clots, not first-time PE.
- After IVC filter: bed rest, monitor vital signs, puncture site, and distal pulses; avoid strenuous activity, heavy lifting, sex, tampons, and driving for 48 hours.
PE Prevention & Medical Treatments
- Encourage liberal fluid intake and leg exercises to prevent clots during bed rest.
- SCDs/TED hose unless a clot is already present in the lower limbs.
- Avoid raising knees with pillows or prolonged dangling of feet.
- Thrombolytics used only for unstable, life-threatening PE cases; contraindications same as for ischemic stroke.
- First oral anticoagulant dose given in ER for stable patients; refer for follow-up.
- Common oral agents: warfarin (Coumadin), apixaban (Eliquis).
- Unstable patients receive heparin drip, baseline/coagulation labs, and are bridged to oral anticoagulants before stopping IV therapy; no invasive procedures during heparin drip.
Supportive Care for PE
- Ventilator support for unstable patients only; otherwise, provide supplemental oxygen.
- Incentive spirometry and cough/deep breath to prevent atelectasis.
- Opioids only for severe pleuritic pain; otherwise use non-pharmacologic comfort measures.
- Continuous cardiac monitoring is required.
Key Terms & Definitions
- Obstructive shock — Shock caused by blockage of blood flow outside the heart.
- Pulmonary embolism (PE) — Blood clot blocking lung arteries.
- Cardiac tamponade — Fluid around the heart preventing normal contraction.
- Tension pneumothorax — Air in chest cavity causing lung collapse and shifting structures.
- IVC Filter — Device to catch clots in the inferior vena cava.
- DVT — Deep vein thrombosis; a clot in the deep veins.
- SCD/TED hose — Devices/socks for preventing clot formation in the legs.
- Thrombolytics — Medications to dissolve dangerous clots.
Action Items / Next Steps
- Review anticoagulation protocols, indications, and contraindications.
- Memorize classic signs and urgent treatments for PE, tamponade, and tension pneumothorax.
- Study prevention strategies and post-procedure care for IVC filters.