The use of a pulmonary artery catheter in critically ill patients  remains controversial.

(a)        What potential  benefits are associated with its use?

(b)        What potential  complications are associated with its use?

(c)        In what groups of patients  do you think that it should be used?

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College Answer

The use of a pulmonary artery catheter in critically ill patients  remains controversial.

(a)        What potential  benefits are associated with its use?
Potential benefits relate to the information that is provided. These include:
•    Estimates of left-heart filling pressures. Clinical assessment is notoriously unreliable.
Allows better assessment of true filling pressures, in particular in the presence of pulmonary or right heart dysfunction.
•    Measurement of pulmonary arterial pressures. Clinical assessment is unreliable. Allow titration of therapies to improve right heart function (nitric oxide, GTN, oxygenation, ventilation etc).
•    Measurement of core temperature. Useful assessment of true core temperature.
•    Measurement of cardiac output. Gold standard for measurement (more accurate than clinical assessment).
•    Measurement of mixed venous oxygen saturation. Allows assessment of global oxygen extraction, and facilitates management directed towards this endpoint (eg. fluids, inotropes, sedation etc.)
•    Measurement of right heart pressures. Allows titration of specific management.
•    Calculation of derived variables (eg. SV, SVR) which may provide further direction for management.
•    Some extra features may be available. Consider ability to calculate right ventricular ejection fraction, and to measure cardiac output and mixed venous oxygen saturation continuously.

(b)        What potential  complications are associated with its use?

Potential complications are multiple, some of which are rare and life threatening, others are more subtle, may affect morbidity, and are far more common. Some reference to magnitude of importance of various potential complications should be made. Consider:
•    Additional cost of catheter and flush lines, exposure to heparinised (usually) catheter, ±
requirement for additional staff and/or monitoring equipment
•    Problems associated with delays in instituting management while awaiting completion of insertion

•    Problems associated with the venepuncture (including damage to surrounding structure at risk [dependent on site] eg. nerves, arteries, veins, lung etc).
•    Problems associated with the passage [insertion or removal] (including malposition, arrhythmias)
•    Problems associated with the catheter in situ (including trauma to valves, infection, air embolus)
•    Problems predominantly associated with balloon inflation (including pulmonary artery rupture, air embolus)
•    Problems associated with the information obtained or its interpretation (including limitations of various assumptions relating pressure [eg. PAOP] and preload [eg. LVEDV], errors in calculating derived indices, treatment based on erroneous information)

(c)        In what groups of patients  do you think that it should be used?

The answer should represent a combination of the candidate’s knowledge of the literature, and their experience/expertise. There is very little data to support the routine use of PA catheters in any particular group of patients. Specific reference to situations where it has not been proven to be of benefit may be of value, but has not been asked for specifically. Some justification (eg. risk benefit analysis) for the groups of patients is required.
Expected groups of patients may include:

•    those with combination organ dysfunction (eg. cardiac and lung), with conflicting priorities
•    those who are not responsive (or respond abnormally) to small amounts of inotropic/vasopressor support
•    those where additional information may not be readily obtainable (eg. no echocardiography service)
•    those undergoing cardiac surgery (often restricted to those with impaired LV function)
•    those requiring cardiovascular optimisation for high risk non-cardiac surgery.

Discussion

With this question, one could become overexcited, and write extensively about the various possible minute details of PA catheter use, its various merits and demerits, recruting massive amounts of literature as references.

However, one only has 10 minutes.

(a) What potential  benefits are associated with its use?

  • Direct measurement of several variables with one device:
    • RA pressure
    • PA pressure
    • PA wedge pressure
    • Core temperature
    • Mixed venous saturation
  • Measurement of cardiac output, and mathematical derivation of other variables from thermodilution
  • Titration of therapies to these measurements

(b)What potential  complications are associated with its use?

  • Same as CVC:
    • Perforation of SVC
    • Hemothorax, pneumothorax
    • Atrial fibrillation
  • Unique to PA catheter
    • Ventricular Arrhythmia
    • Thromboembolic events (the catheter is a nidus for clot formation)
    • Mural thrombi in the right heart (up to 30%)
    • Air embolism from ruptured balloon
    • Pulmonary infarction
    • Endocarditis of the pulmonary valve ( 2%)
  • Right bundle branch block
    • If you already have LBBB, this causes complete heart block
    • If you are lucky, it is a transient phenomenon and you only need to pace them transcutaneously for a brief period. If you are unlucky, you have injured the AV node, and the patient needs prolonged transvenous pacing
  • Knotting on structures or on itself ( ~ 1%)
    • If it has gone into the right ventricle by 25-30cm and its still not in the pulmonary artery, you start to worry
  • Damage to the valves
    •  Never pull the catheter back with the balloon inflated! You could tear the valve leaflets
  • Pulmonary artery rupture: 0.2% risk,  70% mortality (The historical mortality rate from Kearney & Shabot, 1995)
    • Risk factors: pulmonary hypertension, mitral valve disease, anticoagulants and age over 60

(c)In what groups of patients  do you think that it should be used?

  • Patients who require the titration of multiple simultanous resuscitation strategies (inotropes, vasopressors and fluid resuscitation)
  • Situations where non-invasive assessment of hemodynamic parameters and cardiovascular funtion is not available, or impossible (eg. where there is no TTE service, or where TTE or TOE is impossible, for instance in patients with oesophagectomy or an open mediastinum)
  • Situations where therapy is titrated to pulmonary artery pressure (eg. inhaled pulmonary vasodilators), and more generally situations when therapy is titrated to any of the directly measured variables
  • Situations where the risk of PA catheter insertion is outweiged by the benefit, and where less invasive methods of monitoring are considered inferior, or are impossible (eg. when PiCCO pulse contour analysis is invalidated by arrhythmia)

The awesomeness of the PA catheter is discussed in greater detail elsewehere.

References

This a full-text version of the seminal paper from 1970:

Swan HJ, Ganz W, Forrester J, Marcus H, Diamond G, Chonette D (August 1970). "Catheterization of the heart in man with use of a flow-directed balloon-tipped catheter"N. Engl. J. Med. 283 (9): 447–51.

 

A manufacturer (Edwards) offers some free information about the PA catheter on their product page.

 

The PA catheter section from The ICU Book by Paul L Marino (3rd edition, 2007) is a valuable read.

 

Armstrong, Ehrin J., James M. McCabe, and Melvin D. Cheitlin. "Pulmonary artery catheterization in the intensive care unit: just numbers floating by?."Archives of internal medicine 171.12 (2011): 1110-1111.

Kearney, Thomas J., and M. Michael Shabot. "Pulmonary artery rupture associated with the Swan-Ganz catheter." CHEST Journal 108.5 (1995): 1349-1352.

 

Additionally, UpToDate has an article on PA catheter complications