thumb|300px|Swan sitting on its packaging
A pulmonary artery catheter (PAC), also known as a Swan-Ganz catheter, thermodilution catheter, or right heart catheter, is a balloon-tipped catheter that is inserted into a pulmonary artery in a procedure known as pulmonary artery catheterization or right heart catheterization. Pulmonary artery catheterization is a useful measure of the overall function of the heart particularly in those with complications from heart failure, heart attack, arrhythmias or pulmonary embolism. It is also a good measure for those needing intravenous fluid therapy, for instance post heart surgery, shock, and severe burns.
Indications
General indications are:
- Management of complicated myocardial infarction
- Hypovolemia vs cardiogenic shock
- Ventricular septal rupture (VSR) vs acute mitral regurgitation
- Severe left ventricular failure
- Right ventricular infarction
- Unstable angina
- Refractory ventricular tachycardia
- Assessment of respiratory distress
- Cardiogenic vs non-cardiogenic pulmonary edema
- Primary vs secondary pulmonary hypertension
- Assessment of types of shock
- Assessment of therapy
- Afterload reduction
- Vasopressors
- Beta blockers
- Intra-aortic balloon counter-pulsation
- Assessment of fluid requirement in critically ill patients
- Hemorrhage
- Sepsis
- Acute kidney injury
- Burns
- Management of postoperative open heart surgical patients
- Assessment of valvular heart disease
- Assessment of cardiac tamponade/constriction
No study has definitively demonstrated improved outcome in critically ill patients managed with PA catheters. Given that the PA catheter is a monitoring tool and not a therapy in and of itself this is not entirely surprising. Justification for its continued use rests on a large body of clinical experience, disadvantages of other cardiac output monitoring systems, its ability to accurately measure pulmonary artery pressure, and the potential to use the catheter as a direct conduit for drug administration into the pulmonary artery.
Procedure
The catheter is introduced through a large vein—often the internal jugular, subclavian, or femoral veins. Ease of placement for a pulmonary artery catheter from easiest to difficult is: right internal jugular > left subclavian > left internal jugular > right subclavian.
Controversy
The benefit of the use of this type of catheter has been controversial. Therefore, many clinicians minimize its use.
Evidence of benefit
Several studies in the 1980s seemed to show a benefit of the increase in physiological information. Many reports showing benefit of the PA catheter are from anaesthetic, and Intensive Care Unit (ICU) settings. In these settings cardiovascular performance was optimized thinking patients would have supra-normal metabolic requirements. In 2005, a multi-center randomized controlled trial found no difference in mortality or length of stay in ICU patients who received pulmonary artery catheters, though it did find a 10% incidence of complications related to the procedure.
Evidence of harm or lack of benefit
Contrary to earlier studies there is growing evidence the use of a PA catheter (PAC) does not necessarily lead to improved outcome. One explanation could be that nurses and physicians are insufficiently knowledgeable to adequately interpret the PA catheter measurements. Also, the benefits might be reduced by the complications from the use of the PAC. Furthermore, using information from the PAC might result in a more aggressive therapy causing the detrimental effect. Or, it could give rise to more harmful therapies (i.e. achieving supra-normal values could be associated with increased mortality).
Utility of pulmonary artery catheterization
This interpretation of Adolph Ficks' formulation for cardiac output by time/temperature curves is an expedient but limited and invasive model of right heart performance. It remains an exceptional method of monitoring volume overload leading to pulmonary edema in an ICU setting.
A feature of the pulmonary artery catheter that has been largely ignored in the clinical setting is its ability to monitor total body oxygen extraction by measuring the mixed venous oxygen saturation. Regardless of the value obtained by measurements of the cardiac output, the mixed venous oxygen saturation is an accurate parameter of total body blood flow and therefore cardiac output. The assumption that a low mixed venous oxygen saturation (normal = 60% except for the coronary sinus where it approximates 40% reflecting the high metabolic rate of the myocardium) represents less than adequate oxygen delivery is consistent with physiological and metabolic observations. High oxygen extraction is associated with low cardiac output and decreased mixed venous oxygen saturation. Except during hypothermia and in severe sepsis, low mixed venous oxygen saturations are indication of inadequate hemodynamics. The ability of the pulmonary artery catheter to sample mixed venous blood is of great utility to manage low cardiac output states.
Non-invasive echocardiography and pulse-wave cardiac output monitoring are concordant with (and much safer) if not better than invasive methods defining right and left heart performance. The emergence of MRSA and similar hospital based catheter infections now clearly limits the utility of this type of invasive cardiac ICU intervention.