Diagnostics & Procedures · Topic 4 of 16

Hemodynamic Monitoring & the PA Catheter

Diagnostics · invasive hemodynamics

Hemodynamic Monitoring & the PA Catheter

Know the normals — CVP 2–6, wedge 6–12, CI 2.5–4, SVR 800–1200 — and the shock types sort themselves by output, resistance and filling pressure.

Key numbers

CVP 2–6 and wedge 6–12 mmHgPAOP 6–12 mmHg

Cardiac index 2.5–4 L/min/m²CI 2.5–4 L/min/m²

SVR 800–1200 dyn·s/cm⁵SVR 800–1200

Cardiogenic shock: CI < 2.2, wedge > 15CI < 2.2, PCWP > 15

Mixed venous saturation normally 65–75%SvO₂ 65–75%

01 · The numberCVP 2–6 and wedge 6–12 mmHg

Normal filling pressures: right atrial pressure (CVP) 2–6 mmHg and pulmonary artery occlusion (wedge) pressure 6–12 mmHg; the wedge approximates left atrial pressure and LV end-diastolic pressure.

02 · The numberCardiac index 2.5–4 L/min/m²

Normal cardiac output is 4–8 L/min and cardiac index (output ÷ body surface area) 2.5–4 L/min/m²; output is measured by thermodilution through the PA catheter.

03 · CalculateSVR 800–1200 dyn·s/cm⁵

Systemic vascular resistance = (MAP − CVP) × 80 ÷ cardiac output; normal is 800–1200 dyn·s/cm⁵. It is high in low-output shock and low in vasodilatory shock.

Diagnosis & monitoring

Work-up

Cardiogenic shock: CI < 2.2, wedge > 15 must knowThe cardiogenic-shock hemodynamic profile is a cardiac index below 2.2 L/min/m² with a pulmonary capillary wedge pressure above 15 mmHg — cold and wet.

Mixed venous saturation normally 65–75%SvO₂ sampled from the PA port is normally 65–75%; a low value means oxygen delivery is falling short — low cardiac output, anemia, hypoxemia — or demand is rising.

Low CVP or wedge suggests hypovolemiaA CVP below 5 mmHg or wedge below 8 mmHg suggests hypovolemia; a CVP above 12–15 mmHg makes hypovolemia unlikely as the sole cause of hypoperfusion, and further fluid risks overload.

Management

Orders

Read pressures at end-expiration, leveled mid-chestZero and level the transducer at the atrial (mid-chest) level and read CVP and wedge at end-expiration; readings are unreliable with PEEP above 10 cmH₂O or large swings in pleural pressure from respiratory distress.

Insertion waveforms: RA, RV, PA, wedgeFloat the catheter balloon-up: entering the RV, systolic pressure jumps to about 30 mmHg with unchanged diastolic; entering the PA, diastolic rises; then it wedges. Deflate and confirm position by radiograph.

Red flags & don'ts

Avoid harm

Never leave the balloon wedged complicationInflate the balloon no longer than 30 seconds: overinflation or a permanently wedged catheter causes pulmonary infarction, and pulmonary artery rupture (0.03–0.2% of insertions) occurs on wedging and is often fatal.

Ventricular arrhythmias: commonest PA catheter complication complicationVentricular arrhythmias during passage through the right ventricle are the most common PA catheter complication; others are valve injury, intracardiac perforation, knotting, endocarditis and infection.

The rules

Know these

Wedge misleads in mitral disease and high PEEPThe wedge reflects LV preload poorly with mitral stenosis or regurgitation, PEEP above 10 cmH₂O, changed LV compliance (MI, pericardial effusion, high afterload) or severe pulmonary hypertension.

PA catheter is not routineRoutine PA catheter use does not lower mortality; consider it for shock of uncertain, mixed or severe cause (especially with oliguria or pulmonary edema), complicated MI or heart failure, and cardiogenic shock (Class 2b).

Use dynamic tests to predict fluid responseStatic pressures predict fluid responsiveness poorly; prefer dynamic tests — pulse pressure or stroke volume variation ≥ 12% in a passively ventilated patient in sinus rhythm, or passive leg raising read on real-time cardiac output.

Cardiogenic or distributive shock on the PA catheter?

Commonly confused

Cardiac index	Low (< 2.2 L/min/m²)
SVR	High
Wedge pressure	High (> 15 mmHg)
CVP	High

More detail

Reference

Show 6 reference facts

Fluid responsiveness is usually defined as a rise in stroke volume index or cardiac index of 15% or more after a fluid challenge of about 250 mL (or 3 mL/kg) crystalloid given over 5–10 minutes.

PA diastolic pressure (normally about 8–15 mmHg) tracks the wedge and can stand in for it, avoiding repeated wedging — unless pulmonary vascular resistance is raised (pulmonary fibrosis, pulmonary hypertension).

Other normals: PA pressure 15–25/8–15 mmHg (mean 10–20), RV pressure 15–25/0–8 mmHg, pulmonary vascular resistance 100–250 dyn·s/cm⁵, stroke volume 60–100 mL.

Tricuspid regurgitation produces a prominent v wave on the CVP tracing and can distort thermodilution cardiac output; rapid fluid infusion through the catheter ports also causes artifactual readings.

Cardiac power output = MAP × cardiac output ÷ 451; a value ≤ 0.6 W marks classic cardiogenic shock and predicts mortality (see Cardiogenic Shock sheet).

A right internal jugular or left subclavian approach is typically preferred for placing a PA catheter (or a transvenous pacing wire).

Pearl

Pump, pipes or tank: cardiac index tells the pump, SVR the pipes, and the wedge and CVP the tank.

Sources · Edwards Clinical Education — Normal Haemodynamic Parameters and Laboratory Values (reference card, 2022) · Merck Manual Professional — Monitoring and Testing the Critical Care Patient (pulmonary artery catheter) · Merck Manual Professional — Shock · Merck Manual Professional — Intravenous Fluid Resuscitation · Hemodynamic profiles in circulatory shock (Table 1). Arch Cardiol Mex 2020 — SciELO · Kouz K et al. The contemporary pulmonary artery catheter. Part 2: measurements, limitations, and clinical applications. J Clin Monit Comput 2022 · Monnet X, Teboul JL et al. Using the ventilator to predict fluid responsiveness. Intensive Care Med 2025 · Sinha SS et al. 2025 Concise Clinical Guidance: ACC Expert Consensus Statement on the Evaluation and Management of Cardiogenic Shock. J Am Coll Cardiol 2025;85:1618–1641 · Heidenreich PA et al. 2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure (§9.5 cardiogenic shock). J Am Coll Cardiol 2022;79:e263–e421 · Merck Manual Professional — Pericarditis (pericardial effusion and cardiac tamponade) · Pulse pressure versus continuous flow monitoring for fluid responsiveness during passive leg raising. BMC Anesthesiol 2026 · Merck Manual Professional — How To Do Internal Jugular Vein Cannulation, Ultrasound-Guided · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).