CVP is a poor sole guide to fluid responsiveness. Use dynamic indices, echo, or fluid challenge where appropriate. PA catheter complications include arrhythmia and pulmonary artery rupture.
CVP waveform (RA)
- a wave: atrial contraction
- c wave: ventricular contraction (tricuspid bulge)
- v wave: atrial filling against closed tricuspid
- Elevated: TR, fluid overload, tamponade (with other signs)
PA catheter values
- PAOP approximates left atrial pressure (when wedge correct)
- Cardiac output by thermodilution
- SVR and PVR calculations in ICU
Normal PAOP (6 to 12)
- Adequate LV filling
- Interpret with cardiac output
- Prefer dynamic indices
Low PAOP
- Suggests hypovolaemia (context)
- Consider a fluid challenge
- Beware RV failure and sepsis
High PAOP
- LV failure, mitral disease
- Pulmonary oedema risk
- Treat the cause, senior review
Safe wedge
1
1. Position
Float catheter with pressure waveform guidance to PA (systolic step-up from RV).
Float catheter with pressure waveform guidance to PA (systolic step-up from RV).
↓
2
2. Wedge
Inflate balloon briefly; obtain PAOP. Never leave balloon inflated. Confirm waveform (no ventricular contour).
Inflate balloon briefly; obtain PAOP. Never leave balloon inflated. Confirm waveform (no ventricular contour).
↓
3
3. Interpret
PAOP high: LV failure, mitral disease. Low: hypovolaemia (context needed). Mixed venous saturations for oxygen delivery assessment.
PAOP high: LV failure, mitral disease. Low: hypovolaemia (context needed). Mixed venous saturations for oxygen delivery assessment.
↓
4
4. Complications
Treat arrhythmias during passage. Report haemoptysis (PA rupture) immediately.
Treat arrhythmias during passage. Report haemoptysis (PA rupture) immediately.
Fluid response
- Static pressures alone mislead in sepsis and RV failure
- Passive leg raise or mini-fluid challenge if appropriate
Pitfalls
- Wedge in wrong position (overwedging)
- Using CVP target alone in ITU
MedPrep - www.medprep.uk - Educational revision aid only. Not clinical guidance. Doses are adult examples; check the BNF, current guidelines and local policy, and seek senior advice. Nov 2026