PA Catheter Basics

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Picture of Alyx Presler
Alyx Presler
Emergency department nurse turned to the CVICU dark side. Revels in the airway, FOAMed, hiking, and hanging out with a black lab named Blue Gill.

The Pre-brief

Pulmonary artery catheters (PACs), also known as Swan-Ganz catheters, are intravascular catheters that are inserted through a central vein (femoral, jugular, subclavian) and advanced through the right side of the heart to rest in the pulmonary artery (PA). PACs are utilized for hemodynamic assessment in right ventricular (RV) failure, pulmonary hypertension, cardiogenic shock, and post-cardiac surgery.

PACs have four lumens: blue, white, yellow, red/balloon, and often a fifth thermistor lumen. 

  • Blue – right atrial lumen (CVP)
  • White – right atrial infusion lumen (med port) 
  • Yellow – pulmonary artery lumen (PAP/SvO2) – this is inserted through a sheath that remains in place with the PAC
  • Red – pulmonary artery balloon port (balloon/PAWP)
  • Thermistor – pulmonary artery thermodilution lumen

For additional information visit: The Vitals: Pulmonary Artery Catheter – CriticalCareNow

PACs allow for assessment of Cardiac Output (CO), Pulmonary Artery Pressure (PAP), Mixed venous oxygenation (SvO2), Pulmonary Artery Wedge Pressure (PAWP), and Central Venous Pressure (CVP) through blood draws and waveform analysis. CO is the amount of blood pumped by the heart each minute and is simply heart rate multiplied by stroke volume (the amount of blood ejected with each beat). With a PAC, CO is determined by obtaining an SvO2 level, the patient’s body surface area, a hemoglobin level, and an SpO2 reading. All of these numbers are collected and inserted into a Fick calculator which gives us CO and cardiac index (CI). The only lab values needed to run a Fick is a mixed venous saturation (SvO2) and an arterial saturation. CI is merely CO with consideration of the patient’s body surface area (BSA), and is, therefore, more accurate for clinical decision making. 

PAP is a reflection of cardiac heart pressures and is read as a systolic and diastolic number. Pulmonary artery systolic pressure (PASP) is the pressure exerted by the right ventricle (RV) during systole on the PA. Whereas pulmonary artery diastolic pressure (PADP) is a measurement of the pressure in the PA during RV diastole. This is a continuous waveform measurement.

SvO2 is the percentage of oxygen attached to the hemoglobin in the blood leaving the right ventricle. Therefore, SvO2 can be used to determine if CO and oxygen delivery is sufficient for the patient. A Low SvO2 can indicate that either body tissues are taking more oxygen from the blood as compensation for increased oxygen needs or are not receiving enough oxygen to begin with (CO is not high enough to meet the body’s demand). An SvO2 is obtained through a blood draw from the yellow lumen of the PAC.

PAWP is a measurement of left ventricular end-diastolic pressure. Basically, this is a measurement of preload, or filling volume, to the left ventricle (LV). PAWP is obtained by utilizing the balloon port of the PAC. Between 0.5-1.5mL (a specific syringe exists that only allows 1.5mL, try not to lose it!) is injected into the red lumen, this causes the balloon to occlude antegrade flow from the distal PA to the pulmonary capillaries. Due to the occlusion created by wedging, it is important to have your monitor set up to “freeze” the screen when a wedge waveform is achieved. Since you do not want to be wedged for longer than 15 seconds, preparing to get a still of the wedged waveform, or “freezing” the screen, will allow you time to assess the waveform once the air is removed from the balloon. Only insert air until the waveform is “wedged”, freeze the screen, and deflate the balloon. Allow the balloon to deflate passively and ensure a PAP waveform is present following wedging. Not all PACs will wedge, often due to positioning. Do not wedge a PAC unless there is an order to do so from the clinician. 

Finally, CVP is a representation of RV preload and pressure. Using this measurement has many caveats and will require an entire post in itself! This is a continuous waveform measurement and can also be assessed with a CVC sans PAC.

So, what are the normal values for these measurements?

  • CO 4-8 L/min
  • CI 2.5-4 L/min
  • PAS 15-25 mmHg
  • PAD 2-12 mmHg
  • PAP Mean 10-20 mmHg
  • SvO2 65-70% (typical oxygen extraction is 25-30%)
  • PAWP 8-12 mmHg
  • CVP 2-6 mmHg

In order to get accurate readings, it is important to level and zero the lines prior to waveform analysis. Assess leveling anytime the patient changes position for accurate continuous monitoring.

Level first:

  1. Find and mark the patient’s phlebostatic axis (the level of the right atrium; approximately 4cm posterior to the sternum at the fourth intercostal space), marking it will eliminate some variation between those leveling
  2. Using an actual level, level the stopcocks (there will be one for each measurement: PAP and CVP) to the marked phlebostatic axis

Zero second:

  1. Move the stopcocks off to the patient, open to atmospheric pressure
  2. Select “Zero all” on the monitor, it is also possible to zero each line individually; just learn where the button is on your monitor
  3. Turn the stopcocks back off to the patient

After leveling and zeroing the lines, waveform analysis can be performed. At this stage, it is crucial to measure the waveforms at the end of expiration. This is because pleural pressure is closest to atmospheric pressure at the end of expiration. To achieve this, it is helpful to monitor the respiratory waveform simultaneously. An accurate PAP is the peak and trough measurement of the waveform at end-expiration. CVP measurement is taken at the base of the c wave, this is just after the R wave on an ECG, and represents the final pressure in the RV before systole.

The nurse has the responsibility of monitoring and maintaining the PAC while it is in place. In some facilities the nurses assist with placement of the PAC, this requires helping maintain sterility during the procedure, positioning the patient, and monitoring the cardiac rhythm. The yellow lumen has measurements on it and it is imperative to maintain placement in the PA. Therefore, nurses are responsible for assessing the measurement on the yellow line and notifying the clinician of any changes. The thick black line on the yellow line indicates a measurement of 50cm, and the thinner lines indicate 10cm. So, for example, if there is a thick black line and a thin black line at the insertion site then the line is measured at 60cm. It is possible that the clinician could want to advance/pull back the catheter if the waveform is reading either RA/PAWP, respectively. Facilities may have differing policies on this, but it seems that it is more widespread that the clinician would perform these alterations. 

Waveform analysis and running SvO2 through the Fick calculator is based on clinician preference or facility policy. To prevent inconsistencies in numbers, use the same BSA for every Fick calculation. It may be helpful to write a note in the EMR Kardex so anyone doing a Fick calculation can easily access it.

When removing a PAC, first order from a clinician is needed, then carefully remove the existing dressing. Once this is done, clean the area with a chlorhexidine swab and allow that to dry. Ensure all sutures are removed, have the patient take a breath in and then hum, while humming remove the PAC in one steady movement while assessing for dysrhythmias. Humming is a great way for the nurse to ensure the patient is breathing out, a breath in while removing a PAC can cause an air embolus. If any resistance is met during removal, stop the procedure and contact the clinician. Once out, hold pressure for 5-10 minutes, then create an occlusive dressing with vaseline on gauze and cover it with a transparent dressing. 

The Debrief

  • PACs lie within the pulmonary artery for PAP monitoring but have lumens that lie within the right ventricle for medications and CVP monitoring.
  • Ensure leveling and zeroing prior to waveform analysis. Assess both waveforms at end-expiration.
  • Assess the peak and trough of PAP waveform and the c-wave of CVP waveform.
  • Assess PAC measurement frequently and notify the clinician with waveform changes.

References

  1. Fang JC, Jones TL. Can a Pulmonary Artery Catheter Improve Outcomes in Cardiogenic Shock? JACC Heart Fail. 2020 Nov;8(11):914-916. doi:10.1016/j.jchf.2020.08.013. PMID: 33121703.
  2. Rodriguez Ziccardi M, Khalid N. Pulmonary Artery Catheterization. [Updated 2021 Aug 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482170/
  3. Shah P, Louis MA. Physiology, Central Venous Pressure. [Updated 2020 Sep 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519493/

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