Obstructive Shock: Tamponade, Tension PTX, Massive PE

• Obstructive shock arises from tamponade (pericardiocentesis), tension pneumothorax (needle/finger decompression), massive PE (thrombolysis), or air/fat/amniotic embolism.
• For massive PE with hypotension, give systemic thrombolysis (alteplase 100 mg/2 h); catheter-directed/mechanical thrombectomy (Class 2a in the highest-risk category) or surgical embolectomy when lysis is contraindicated; activate the PERT where available.
• Bedside POCUS makes the diagnosis: RV strain, tamponade physiology, absent lung sliding.
• Amniotic fluid embolism gets supportive care (ABC, pressors, correct coagulopathy); mortality is high and management mirrors an anaphylaxis variant.

Mechanisms of Mechanical Shock

• Mechanical obstruction with pulmonary vasoconstriction
• Pulmonary vascular resistance ↑ → RV afterload ↑
• With RV dilatation, RV end-diastolic volume and pressure ↑ → right atrial pressure ↑ while venous return ↓; RV preload ↓, then RV stroke volume ↓, then LV preload ↓
• Interventricular septal flattening → LV compliance ↓ → LV preload ↓ further
• Myocardial O₂ demand ↑ as RV wall stress ↑; myocardial ischemia follows coronary vascular perfusion ↓ → LV + RV contractility ↓
• Cardiac output ↓ → hypotension → end-organ hypoperfusion
• Shock → refractory shock, circulatory collapse, demise
• Pre-existing cardiopulmonary disease worsens the cardiac output fall, and hypotension further lowers venous return — a self-perpetuating cycle

Managing Massive Pulmonary Embolism

• Massive PE suspected → supplemental O₂
• Refractory hypoxemia?
• Intubate and start mechanical ventilatory support
• Vasopressor start/add: norepinephrine (preferred over dopamine — SOAP II), targeting SBP >90 mm Hg and MAP ≥65 mm Hg
• Add dobutamine infusion; titrate to cardiac index >2.2 L/min/m²
• Place a 7-French central venous catheter or two 16-gauge peripheral IVs → 1 L NS or LR bolus
• Monitor: ECG/telemetry · end-tidal CO₂ · pulse oximetry · arterial line · transesophageal Doppler
• 2D echocardiogram: assess LV and RV function
• Hemodynamics improved?
• Additional fluid boluses as needed to hold adequate perfusion pressure; reassess frequently
• Cardiopulmonary arrest → to ACLS protocol
• Exclude alternate diagnoses: cardiac tamponade · aortic dissection · RV infarction · LV dysfunction · valvular dysfunction
• High-dose anticoagulant Rx: heparin bolus 10,000 U (or 80 U/kg) → infusion 15 U/kg/h, target aPTT >80 s; hold infusion before fibrinolytics; check aPTT after fibrinolytics — restart heparin once aPTT <80 s; avoid LMW heparin in impaired renal function
• Fibrinolysis contraindicated? (intracranial neoplasm · prior hemorrhagic CVA · intracranial hemorrhage · active hemorrhage · CVA <2 months · pregnancy)
• Salvage Rx to weigh: surgical or catheter embolectomy · highest-risk (Category E1) patients at experienced centers also have a Class-2a reperfusion option in catheter-directed/mechanical thrombectomy (2026 AHA/ACC guideline)
• Lyse via peripheral IV: reteplase 10 U bolus + 10 U after 30 minutes OR alteplase 100 mg over 2 hours (lower-dose lysis is a Class-2b option)
• Hemodynamics improved?
• After lysis: close observation · confirmatory testing once stable · LE duplex Doppler · IVC filter if DVT is found
• Activate the PE Response Team (PERT) where available · salvage Rx options: surgical or catheter embolectomy · highest-risk (Category E1) patients at experienced centers also have a Class-2a reperfusion option in catheter-directed/mechanical thrombectomy (2026 AHA/ACC guideline)

Managing Air Embolism Syndrome

• Air embolism syndrome suspected
• Identify and eliminate the portal of gas entry: cover the surgical site with saline-soaked dressings · position the surgical site below right atrial level · stop gas insufflation if applicable · check vascular access devices · check injection or infusion devices
• Left lateral decubitus positioning; consider air aspiration via central venous catheter
• Supplemental O₂, FiO₂ 1.00
• Refractory hypoxemia?
• Intubate and start mechanical ventilatory support
• Raise PEEP to 5–10 cm H₂O to raise intrathoracic pressure; monitor for excessive PEEP effects
• Place a 7-French central venous catheter or two 14–16-gauge peripheral IVs → expand volume using isotonic crystalloids or colloid boluses, targeting CVP 10–12 mm Hg
• Monitors: pulse oximetry · end-tidal CO₂ · ECG/telemetry · arterial line · PA catheter or transesophageal Doppler · mental status and neuro checks (arterial embolus)
• 2D echo: check LV and RV function; rule out mimics — acute PE, hypovolemic shock, septic shock, cardiogenic shock, anaphylaxis, fat embolism
• Hemodynamics improved?
• Additional fluid boluses as needed to hold adequate perfusion; reassess frequently
• Vasopressor start/add: norepinephrine (preferred over dopamine — SOAP II), with epinephrine if needed, targeting SBP >90 mm Hg and MAP ≥65 mm Hg
• Start dobutamine infusion; titrate to cardiac index >2.2 L/min/m²
• Cardiopulmonary arrest → ACLS pathway

Managing Fat Embolism Syndrome

• Fat embolism syndrome suspected
• Supplemental O₂
• Refractory hypoxemia?
• Intubate and start mechanical ventilatory support
• Monitor for ALI/ARDS: use a low tidal volume lung-protective ventilation strategy
• Place a 7-French central venous catheter or two 14–16-gauge peripheral IVs → 1 L NS or LR bolus
• Monitors: pulse oximetry · end-tidal CO₂ · ECG/telemetry · arterial line · CVP monitoring · transesophageal Doppler · PA catheter only in selected cases
• 2D echo: check LV and RV function; rule out mimics — acute PE, hypovolemic shock, septic shock, cardiogenic shock, anaphylaxis, air embolism
• Hemodynamics improved?
• Additional fluid boluses as needed to hold adequate perfusion; reassess frequently
• Vasopressor start/add: norepinephrine (preferred over dopamine — SOAP II), targeting SBP >90 mm Hg and MAP ≥65 mm Hg
• Dobutamine infusion; titrate to cardiac index >2.2 L/min/m²
• Cardiopulmonary arrest → go to ACLS protocol

Managing Amniotic Fluid Embolism Syndrome

• Amniotic fluid embolism syndrome suspected
• Monitors: pulse oximetry · end-tidal CO₂ · ECG/telemetry · arterial line · CVP monitoring · transesophageal Doppler · PA catheter only in selected cases · fetal heart monitor
• Fetal distress?
• Emergent delivery
• Supplemental O₂
• Refractory hypoxemia?
• Intubate and start mechanical ventilatory support
• Adjust PEEP and FiO₂ to hold PaO₂ >65 mm Hg — prevent fetal hypoxia and maternal anoxic brain injury
• Place a 7-French central venous catheter or two 14–16-gauge peripheral IVs → 1 L NS or LR bolus
• 2D echo: check LV and RV function; rule out mimics — acute PE, hypovolemic shock, septic shock, cardiogenic shock, anaphylaxis, fat embolism, air embolism
• Manage neurologic complications: regular neuro checks · seizure precautions · maintain oxygenation · treat seizures aggressively · antiepileptic drugs when necessary · intubate for airway protection when necessary
• Screen for coagulopathy and disseminated intravascular coagulation → transfuse blood products as needed
• Hemodynamics improved?
• Additional fluid boluses as needed to hold adequate perfusion; reassess frequently
• Vasopressor start/add: norepinephrine (preferred over dopamine — SOAP II), targeting SBP >90 mm Hg and MAP ≥65 mm Hg
• Add dobutamine; titrate infusion to cardiac index >2.2 L/min/m²
• Maternal cardiopulmonary arrest: LEFT lateral tilt / manual left uterine displacement to relieve fetal pressure on the maternal IVC · follow ACLS protocol · emergent delivery · continue ACLS during delivery if necessary