Study Notes – Hemodynamic Monitoring (CVP & PAWP)

1. Purpose of Hemodynamic Monitoring

• Assess cardiac output (heart function).

• Determine fluid volume status (euvolemia, overload, or deficit).

• Guide goal-directed therapy: fluid management, vasopressors, vasodilators, inotropes.

• Especially important in heart failure, shock, valve disorders, pulmonary hypertension, post-MI complications, and pre-transplant patients.

2. Central Venous Pressure (CVP)

• Definition: Pressure in the right atrium → reflects right ventricular preload.

• Normal range: 2–6 mmHg.

• Clinical meaning:

  • ↑ CVP → fluid overload (excess volume, heart failure).

  • ↓ CVP → hypovolemia (dehydration, hemorrhage).

• Monitoring devices:

  • Triple lumen central line.

  • Swan–Ganz catheter (can also measure CVP).

3. Pulmonary Artery Wedge Pressure (PAWP / PCWP)

• Definition: Indirect measure of left ventricular end-diastolic pressure (LVEDP).

• Normal range: 6–12 mmHg.

• Clinical meaning:

  • ↑ PAWP → left ventricular failure, pulmonary edema, fluid overload.

  • ↓ PAWP → fluid deficit, hypovolemia.

• Device: Swan–Ganz catheter (aka PA catheter).

  • Inserted via IJ or subclavian vein → RA → RV → pulmonary artery.

  • Balloon at tip inflated → wedges in small PA branch → measures left-sided filling pressure indirectly.

• Note: We cannot place direct catheters into the left ventricle (too dangerous), so PAWP is the surrogate measure.

4. Swan–Ganz Catheter (Pulmonary Artery Catheter)

• Ports / hubs (5 main components):

  1. Proximal infusion port → sits in RA, measures CVP, infusions, blood sampling.

  2. Proximal injectate lumen → sits in RV, used for thermodilution cardiac output measurement.

  3. Distal lumen → sits in PA, measures PA pressures.

  4. Balloon inflation port → inflates balloon at catheter tip (for wedge measurement).

  5. Thermistor → temperature sensor for cardiac output measurement.

• Triple lumen central line (simpler version): only 3 ports, no balloon/thermistor, used mainly for CVP monitoring + medication/fluids.

5. Clinical Use of Hemodynamic Monitoring

• Indications:

  • Severe HF (fluid balance is critical).

  • Shock (cardiogenic, septic, hypovolemic).

  • Valvular heart disease.

  • Pulmonary hypertension.

  • Post-MI complications.

  • Candidates for transplant or those on vasoactive drips.

• Therapies guided:

  • Inotropes → ↑ contractility (e.g., dobutamine).

  • Vasopressors → ↑ vascular tone (e.g., norepinephrine) for low volume/pressure states.

  • Vasodilators → ↓ afterload (e.g., nitroprusside) in volume overload/high pressure states.

6. Key Points to Remember

• CVP = right heart preload / fluid status.

• PAWP = left heart preload / LVEDP.

• High values = fluid overload / heart failure.

• Low values = fluid deficit / dehydration / hemorrhage.

• Swan–Ganz catheter: more advanced; used in ICU/critical care.

• Triple lumen central line: more basic; measures CVP + provides reliable central access for multiple infusions.

• Central line benefit: allows infusion of incompatible medications through separate lumens in one line.

Quick memory hook:

• CVP → Right side → preload (RA/RV).

• PAWP → Left side → preload (LV).

• CVP high = too wet (right side).

• PAWP high = too wet (left side).

• Both low = too dry.