Anesthesiology APPLIED Exam › Cardiovascular and cardiac anesthesia

Pulmonary artery catheter: indications, waveforms, complications

Cardiovascular and cardiac anesthesia·~5 min read· Physician-reviewed✓ Sourced · 4

Stem

A 63-year-old man, 82 kg, with alcohol-related cirrhosis, is scheduled for orthotopic liver transplantation. His echocardiogram estimates a right ventricular systolic pressure of 55 mmHg with mildly reduced right ventricular function and a normal left ventricle. His ECG shows a left bundle branch block. Large blood loss and caval clamping are expected.

Question

Will you place a pulmonary artery catheter, and how will you place it and use it safely?

Ideal answer

HeadlineYes: with pulmonary hypertension and right ventricular dysfunction, continuous right pressures, cardiac output and SvO2 will change what I do through clamping and reperfusion.

Pacing pads on before I float it, or a pacing-capable catheter, because passage can cause right bundle branch block and, with his left bundle branch block, complete heart block.¹
Right internal jugular, balloon inflated, reading the waveforms, right atrium to right ventricle to pulmonary artery to wedge at predictable depths.
Wedge only briefly with the minimum volume, and use it as an estimate of left atrial pressure, knowing where it misleads.
Trend output and SvO2 through clamping and reperfusion, rather than worship single numbers; TEE stays for structural questions.
Watch for arrhythmias during passage, the commonest complication, and for pulmonary artery rupture, which presents as hemoptysis.²

Breaking down the answer

Guides, does not cure — routine use has not reduced morbidity or mortality,² nor did PAC-Man or ESCAPE in unselected patients; so only for a specific continuous question: severe pulmonary hypertension, right ventricular failure, liver transplantation, some cardiac surgery, a poor ventricle facing big shifts.
Why not only TEE — better structural information, but it needs an operator and is not a 48-hour ICU monitor. Justifying an invasive monitor without overselling it is the judgment being scored.
Route and depths — right IJ is straightest; the left subclavian's gentle curve follows the catheter, the usual alternative.²^,3 RA 20–25 cm, RV 30–35 cm, PA 40–45 cm, wedge 45–55 cm; no RV trace by 40 cm means coiling: deflate, withdraw.
Wedge overestimates LVEDP — mitral stenosis, pulmonary venous obstruction, PEEP above about 10 cmH2O and tip position in West zone 1 or 2;² I confirm the tip is below the left atrium and read at end-expiration.
Wedge underestimates LVEDP — a stiff ventricle, or acute aortic regurgitation closing the mitral valve early; a normal wedge does not exclude high left ventricular pressure. Large v-waves: acute mitral regurgitation, ischemic papillary dysfunction or a noncompliant atrium; I treat the lesion, not the number.
Thermodilution limits — tricuspid regurgitation and intracardiac shunts make output values unreliable; I cross-check with echo and SvO2. PA diastolic pressure is a usable surrogate for the wedge unless pulmonary vascular resistance is high,² as in this patient.
SvO2 versus ScvO2 — ScvO2 is superior vena caval blood only, missing IVC and coronary sinus return.⁴ It ran higher than SvO2 under anesthesia and agrees poorly in shock, so a normal ScvO2 does not exclude a low SvO2; I trust its trend.⁴

Follow-up question

After reperfusion of the graft, shortly after you wedge the catheter, blood wells up the endotracheal tube and his saturation falls. What is happening, and what do you do?

Follow-up answer

HeadlinePulmonary artery rupture until proven otherwise; it typically happens at the moment of wedging. I tell the surgeon immediately.

Rare, at about 0.03–0.2% of insertions, but often fatal.² I deflate the balloon, pull the catheter back a few centimeters and increase PEEP. A bronchial blocker or double-lumen tube isolates the lung to protect the other side; the bleeding side goes dependent as far as positioning allows; I correct his coagulopathy, and after bypass would reverse heparin with protamine. Ongoing bleeding needs angiographic embolization or surgical repair. I reassess oxygenation and document. Prevention: wedge only briefly, never over-wedge, and keep the tip proximal in anticoagulated, hypothermic or elderly patients with pulmonary hypertension.

Pitfalls that cost points

Leaving the balloon inflated or wedging repeatedly with full volume.
Reading the wedge without stating the conditions that make it wrong.

Rapid-fire

Q: What does a low SvO2 tell you? A: Normal is 65–75%;² below that, oxygen delivery is not meeting demand: low output, anemia, hypoxemia or high consumption; I work through each rather than assume the heart.

Q: Can a central venous saturation replace SvO2? A: For trend, yes; numerically, no: it misses IVC and coronary sinus blood and diverges from SvO2 in shock and on bypass.⁴

Q: Why does the RV trace have a flat or rising diastolic pressure and the PA trace a falling one with a dicrotic notch? A: The RV fills in diastole, so its pressure rises; the PA is behind a closed pulmonic valve, so its pressure decays and the notch marks valve closure.

Q: Why read at end-expiration? A: Pleural pressure is closest to atmospheric then, so the transmural pressure is most accurate in both spontaneous and controlled ventilation.

Q: What is the pulmonary vascular resistance formula? A: 80 × (mean PA pressure − wedge) / cardiac output; normal is below about 2 Wood units, roughly 160 dyn·s·cm−5.

Numbers to know

Item	Value
RA (CVP)	0–8 mmHg²
RV	15–30 / 0–8 mmHg²
PA	15–30 / 4–14 mmHg, mean 9–16²
Wedge	2–12 mmHg²
SvO2	65–75%²
PA rupture	0.03–0.2% of insertions²
Depth from right IJ	RA 20–25, RV 30–35, PA 40–45, wedge 45–55 cm

Sources

1.How To Do Internal Jugular Vein Cannulation, Ultrasound-Guided · Merck Manual Professional Edition, 2026 · merckmanuals.com
2.Monitoring and Testing the Critical Care Patient (Pulmonary Artery Catheter Monitoring) · Merck Manual Professional Edition, 2026 · merckmanuals.comNormal pressures table (adapted from Fowler), PAOP limitations, complication rates; cites the ASA PAC practice guideline, which was not itself fetched.
3.How To Do Infraclavicular Subclavian Vein Cannulation · Merck Manual Professional Edition, 2026 · merckmanuals.com
4.Mixed venous versus central venous oxygen saturation in patients undergoing on pump beating coronary artery bypass grafting · Saudi J Anaesth, 2010 · europepmc.orgAlshaer et al., Saudi J Anaesth 2010;4:63; full text via Europe PMC (PMC2945516). ScvO2 read higher than SvO2 throughout; strong correlation but not numerically interchangeable; discussion cites poor agreement in septic, cardiogenic and neurogenic shock.

Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.