Physiology and Pathophysiology Flashcards
7 cards from real ECMO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Physiology and Pathophysiology flashcards as text
A patient on VV-ECMO develops worsening hypercapnia despite maximal sweep gas flow. What is the most likely explanation?
Answer: Oxygenator thrombosis reducing effective membrane surface area
Oxygenator thrombosis progressively reduces functional membrane surface area, impairing both oxygen transfer and CO2 elimination despite maximal sweep gas flows.
What is the physiological rationale for maintaining a target ACT of 160-200 seconds during ECMO rather than full anticoagulation (ACT >400)?
Answer: Balancing thrombosis prevention against hemorrhagic complications given the procoagulant surface of the circuit
The ECMO circuit's artificial surfaces activate coagulation, but excessive anticoagulation dramatically increases bleeding risk, so moderate heparin targets balance clot prevention with hemorrhage avoidance.
How does ECMO-induced hemolysis contribute to renal injury?
Answer: Free hemoglobin causes renal tubular toxicity and vasoconstriction of the renal microvasculature
Free plasma hemoglobin released during hemolysis is directly nephrotoxic, causing oxidative tubular injury and scavenging nitric oxide to produce renal vasoconstriction and ischemia.
In ARDS patients on VV-ECMO, why is ultra-protective ventilation (TV 2-4 mL/kg) physiologically preferable?
Answer: It minimizes ventilator-induced lung injury while ECMO maintains gas exchange, allowing lung rest
VV-ECMO assumes the gas exchange burden, permitting extremely low tidal volumes that minimize cyclic alveolar stretch, barotrauma, and biotrauma, facilitating lung recovery.
What hemodynamic consequence occurs when ECMO flow is abruptly reduced in a patient with severe cardiogenic shock on VA-ECMO?
Answer: Precipitous drop in mean arterial pressure and end-organ perfusion
In cardiogenic shock, systemic perfusion depends on ECMO flow; abrupt reduction removes the primary driver of cardiac output and tissue oxygen delivery, causing immediate hemodynamic collapse.
Which metabolic disturbance is most commonly associated with massive blood product transfusion during ECMO circuit prime or resuscitation?
Answer: Hypocalcemia from citrate chelation impairing ionized calcium
Citrate used as anticoagulant in stored blood products chelates ionized calcium, causing hypocalcemia that impairs myocardial contractility and coagulation cascade function.
Why does the right ventricle typically dilate and fail before the left ventricle in massive pulmonary embolism requiring ECMO?
Answer: Acute pulmonary vascular obstruction causes sudden RV pressure overload beyond its adaptive capacity
The RV is a thin-walled, low-pressure chamber not adapted to acute pressure loads; sudden obstruction of the pulmonary vascular bed raises RV afterload acutely, causing dilation, ischemia, and failure.