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Information

(see also ScVO2 Monitoring; SVO2 Monitoring; Phlebostatic Axis, Stroke Volume Variation)

A Swan-Ganz (SG) pulmonary artery catheter is a diagnostic tool that allows for direct measurement of pressures in the patient's right atrium, right ventricle, and pulmonary artery, as well as determining filling pressures in the left atrium. It is inserted through a central vein (femoral, jugular, subclavian, or less commonly the antecubital or brachial) and connected to a thermodilution sensor that is attached to a pressure transducer outside the body. In recent years, the benefit of pulmonary artery catheters has become controversial, and many clinicians today minimize its use. It is, however, still an effective tool for the assessment of patients with pulmonary hypertension, cardiogenic shock, heart failure, and unexplained dyspnea. It is still commonly used in the cardiac catheterization lab.

Basic Features

There are numerous models of the SG catheter. Some allow for monitoring of continuous cardiac output, some for monitoring SVO2, some with the ability to pace, and others with extra ports for medication administration. However, all catheters share the same four basic features:

  • Proximal (CVP) port. This port is located 30 cm from the tip of the catheter and rests within the right atrium. It is used for infusions and to monitor CVP. It is historically BLUE.
    • As an option, there may be another port that terminates close to the proximal port at approximately 31 cm. This is an additional infusion port and is historically WHITE or CLEAR.
  • PA distal port. It is located at the very distal tip of the catheter and is used to measure the pulmonary artery pressure. It is also used to draw mixed venous sampling. It is historically YELLOW.
  • Thermistor connector plug. This port terminates 4 cm proximal to the tip of the catheter and rests in a main pulmonary artery. It connects to the cardiac output monitor and allows for determination of cardiac output using thermodilution. Historically, the connector is RED/WHITE.
  • Balloon inflation port.While rarely used at the bedside, this port allows the measurement of the pressure in the left ventricle when there is no obstruction. The port has an “open/close” slide valve, which is historically RED, where a syringe is connected to permit injection of air. The air is used to inflate the balloon at the distal tip of the catheter, thus causing the catheter to float (wedge) into a pulmonary artery. This effectively occludes the right side of the heart and yields a left ventricular pressure reading. The wedge pressure, also known as the pulmonary artery occlusive pressure (PAOP), should correlate with the pulmonary artery diastolic pressure in the absence of disease.

Figure 2.72

Specifications

  • Length: 60 cm (pediatric) to 110 cm (adult).
  • Diameter: 4 Fr (pediatric) to 8 Fr (adult).
  • Markings: Thick rings, 50 cm, and thin rings, 10 cm.
  • Insertion: First choice, right IJ or left SC (left turn, left turn); second choice, left IJ or right SC (requires right turn before left turn).
  • Position: Final adult insertion depth is dependent on patient size. Typically, it is 40 to 55 cm using the IJ access and proximal port in the RA at 30 cm.

Right Atrial Pressure (Central Venous Pressure) or “Preload”

Normal 4 to 10 cm H2O or 2 to 6 mm Hg

Increase in CVP (right ventricle can't pump forward) is related to:

  • Circulatory overload; overinfusion of IV fluid
  • Venous congestion (tamponade, PEEP, heart failure)
  • Severe mitral stenosis; left-to-right shunt
  • Poor contractility of the right ventricle (infarct, pericarditis)
  • High pulmonary vascular resistance, pulmonary edema, and COPD

High levels of PEEP (>5cm H2O) can cause a falsely high CVP. While there is no accurate formula to “adjust” the CVP, studies have shown that a 0.38 cm H2O increase in PEEP results in a 1cm increase in CVP. Other sources suggest that using a 1:1 ratio of PEEP to CVP for any PEEP >5 will provide a rough guesstimate of CVP. For example, a PEEP of 8 would raise the CVP 3.

Decrease in CVP (inadequate venous return) is related to:

  • Hemorrhage
  • Third spacing
  • Extreme vasodilation (shock)

Right Ventricular Pressure (RVP)

The normal is 25 to 30 mm Hg systolic/0 to 5 mm Hg diastolic.

On insertion, start recording pressures here. This is the only time the RVP is measured. The provider must keep the catheter moving, as an irritated ventricle will cause PVCs:

  • Systolic pressure may be increased due to pulmonary hypertension or stenosis.
  • Diastolic pressure may be increased due to right ventricular failure, pericarditis, or tamponade.

Pulmonary Artery Pressure (PAP)

The normal is 17 to 32 mm Hg systolic/8 to 10 mm Hg diastolic/<20 mm Hg mean.

Key Point:To remember the PA normal value, think of “quarters over dimes”.

Right ventricular and pulmonary artery pressures should be the same, but the diastolic will be different:

  • Increased due to left ventricular failure or pulmonary vascular disease (hypertension, embolism, edema)
  • Decreased related to volume depletion, drugs, aspiration, and pulmonary stenosis

Cardiac Output (CO)

The normal is 4 to 8 L/min:

This is the amount of blood ejected by the heart into the systemic circulation each minute.

Cardiac output may be increased related to:

  • AV shunt
  • Pulmonary edema
  • Increased metabolic state (fever, tachycardia, burns)
  • Mild hypertension with wide pulse pressure
  • Early sepsis

Cardiac output may be decreased related to:

  • Infarction
  • Decreased stroke volume (dehydration, diuresis, infarction)
  • Increased pulmonary vascular resistance
  • Valve disorders; slow heart rate
  • Poor left ventricular filling
  • Hypovolemia
  • Tamponade

Cardiac Index (CI)

The normal is 2.5 to 4.5 L/min/m2

Cardiac index directly correlates with the patient's body surface area (BSA) and is derived from the cardiac output value:

  • 2.0 to 2.2 indicates onset of forward heart failure.
  • 1.5 to 2.0 is consistent with cardiogenic shock.
  • <1.5 signals a grave prognosis.

Pulmonary Vascular Resistance (PVR)

Normal 37 to 250 dyne/sec/cm5

A measurement of right ventricular afterload. PVR is the force that must be overcome by the right ventricle to produce blood flow through the pulmonary system. Pulmonary vessels constrict with a fall in the alveolar PO2 of a rise in the arterial PaCO2. Thus, an obstruction such as a pulmonary embolus can cause the PVR to rise.

Systemic Vascular Resistance (SVR) or “Afterload”

Normal 800 to 1,300 dyne/sec/cm5

A measurement of resistance that must be overcome by the left ventricle to produce blood flow. It is also known as peripheral vascular resistance, not to be confused with PVR, which is pulmonary vascular resistance and a separate entity. The SVR always moves inversely to cardiac output.

Increase is related to patient being peripherally constricted as a result of:

  • Hypovolemia
  • Hypothermia
  • Catecholamines
  • Hypertension
  • Cardiogenic shock
  • Massive pulmonary embolism
  • Cardiac tamponade

Figure 2.73

Decrease related to patient being peripherally dilated as a result of vasodilatory therapy or early septic shock