Invasive arterial blood pressure monitoring via radial artery cannulation is performed. The waveform shows pulsus paradoxus — systolic BP variation of >10 mmHg with respiration. In a ventilated patient, what does this indicate?

• A Aortic regurgitation
• B Hypertensive crisis
• C Aortocaval compression
• D Fluid responsiveness and volume depletion; also seen in cardiac tamponade ✓

Explanation

Systolic pressure variation (SPV) >10 mmHg with positive-pressure ventilation, or PPV (pulse pressure variation) >13%, indicates preload dependence/fluid responsiveness — the ventilated patient would respond to a fluid bolus with an increase in cardiac output. Mechanically, positive-pressure inspiration increases intrathoracic pressure, transiently increasing LV afterload and reducing LV preload, causing the pressure variation. In spontaneous breathing, pulsus paradoxus >10 mmHg indicates cardiac tamponade, severe asthma, or constrictive pericarditis. SPV/PPV monitoring using invasive arterial waveforms is more reliable than CVP for guiding fluid therapy.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.