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Obstructive Shock

Seth Alexander

Background

  • Obstructive shock occurs when there is increased resistance to forward blood flow which can occur due to:
    • Resistance in the cardiovascular circuit (i.e., pulmonary embolism, HOCM, critical aortic stenosis)
    • Extrinsic compression on the heart (i.e., pericardial tamponade, tension pneumothorax, dynamic hyperinflation (auto-PEEP), restrictive cardiomyopathy)
  • Risk factors vary based on the underlying pathology but include:
    • PE: Known DVT, prothrombotic conditions, malignancy, recent orthopedic surgery
    • Pneumothorax: Recent chest trauma/thoracic procedures, mechanical ventilation, COPD/emphysema, endobronchial valve placement
    • Tamponade: Recent cardiac procedure, ESRD, cancer, trauma

Clinical Signs/Symptoms

  • General: Hypotension, tachycardia, hypoxemia, elevated JVP
  • Tension pneumothorax: Unilateral breath sounds, tracheal deviation away from the pneumothorax, CXR with one lung collapsed, and mediastinal shift away from the PTX
  • Pulmonary embolism: Right heart strain on EKG (right axis deviation, S1Q3T3, ST depressions in inferior leads/precordial leads, new RBBB), chest pain, hypoxia, sense of impending doom
  • Cardiac tamponade: distant heart sounds (Beck’s Triad with JVD and hypotension), electrical alternans, and/or low amplitude on EKG
  • POCUS findings:
    • PE/causes of increased heart pressures: distended IVC, RV dilation, McConnell’s sign, Septal D sign
    • Pneumothorax: Lack of lung sliding
    • Cardiac tamponade: Diastolic collapse of the RV, large pericardial effusion

Approach in the Hemodynamically Unstable Patient

  • Initial workup: order: STAT CBC, EKG, troponin, VBG, CXR. Evaluate the patient at bedside and bring an ultrasound if available to perform POCUS.
  • Pulmonary Embolism – STAT CTA chest, supportive measures (pressors, supplemental O2), and activate PERC team for discussion regarding mechanical thrombectomy or chemical thrombolysis. Start high-dose therapeutic heparin gtt once clot has been identified – bolus unless contraindicated (i.e., recent GI bleed).
  • NOTE: First line is LMWH due to faster onset of action and longer time in therapeutic range. At VUMC, we often start heparin gtt first because if pt is going for EKOS, they need to be able to turn off AC quickly. We recommend starting heparin gtt until decision for EKOS has been made. If no EKOS, switch to LMWH.
  • Cardiac tamponade – emergency procedural management with cardiothoracic surgery (pericardiocentesis vs drain). 500cc-1L IVF bolus can improve preload and temporarily improve cardiac output.
  • Tension pneumothorax – if there is no lung sliding on POCUS or the STAT CXR shows evidence of tension PTX, emergent needle decompression (14-gauge needle in either the 2nd intercostal space mid-clavicular line or the 4th/5th intercostal space anterior axillary line) vs urgent chest tube placement with pulmonology (if at the VA overnight, ED attending can place one).

Further Evaluation and Management

  • Pulmonary Embolism
    • Evaluate the source for the embolism (four extremity dopplers)
    • If no risk factors for VTE are identified, you could consider a benign hematology outpatient referral for a hypercoagulable work-up.
    • See “Pulmonary Embolism” in cardiology for more information
  • Cardiac Tamponade, HOCM, and Critical Aortic Stenosis
    • Formal echo should be obtained at some point during the admission.
    • These are all worsened by a drop in the patient’s preload; AVOID diuretics or other medications which may worsen obstructive pathophysiology if possible.
    • Preload support (IVF, dobutamine in AS) can help temporize patients pending medical or procedural interventions.
    • Consultation to cardiology and/or cardiothoracic surgery is warrant to discuss management.
    • For more on management of aortic stenosis, see “Valvular Heart Disease” in Cardiology”
  • Tension Pneumothorax
    • Once hemodynamically stabilized, consult to pulmonology for chest tube placement is indicated in large, hemodynamically significant pneumothoraces to ensure resolaution.
    • For more on chest tubes, see “Chest Tubes” in Pulmonary.