Clinical Exercise: Pulmonary Artery Catheter
Scenario:
A 70-yo patient is admitted after an incident where they felt dizziness, shortness of breath, and collapsed in the shopping center. They are conscious but groggy by the time the paramedics arrive, and report that they have had 6 months of worsening shortness of breath on exertion, but have also had fevers/chills during the last three days. The patient had a history of a myocardial infarction 10 years ago as well as HIV, but has not been taking any medications for years. The patient has a blood pressure of 85/60 and has a heart rate of 120 bpm. The patient is breathing at 30 breaths per minute (normal < 20), and body temperature is 39 C (102.2 F)
Diagnosis:
You recognize that the patient is unstable and needs to be admitted immediately to an intensive care unit, but it is unclear why.
On one hand, the patient could have cardiogenic shock, due to severe heart failure. On the other hand, the patient is at high risk for infection, putting them at risk for septic shock.
The treatment options for these two possibilities are very different. In cardiogenic shock, the patient has decreased cardiac output due to preload overload (far right of Starling Curve); you would want to start diuretics. In septic shock, the patient usually has decreased cardiac output due to insufficient preload (far left of Starling curve); you would want to start fluids.
You decide that close monitoring with a pulmonary artery catheterization is needed to ensure the patient receives the right treatment.
Mechanism:
A pulmonary artery catheterization (PAC, also known as a right heart catheterization or a Swan-Ganz catheter) is a procedure where a catheter is advanced into a pulmonary artery. The primary purpose is diagnostic to allow simultaneous monitoring of pressures in the right atrium, right ventricle, pulmonary artery, and indirectly the pulmonary wedge pressure (estimation of left atrial pressure).
A pulmonary artery catheter is introduced through a large vein such as the jugular, brachial, subclavian, or femoral veins (the internal jugular and subclavian veins allow the easiest access). The position of the tip while advancing can be monitored by dynamic pressure readings from the tip and/or with the air of fluoroscopy imaging.
The standard pulmonary artery catheter is equipped with an inflatable balloon at the tip to facilitate its placement into the pulmonary artery by flow of blood and when inflated wedges the catheter into a small pulmonary blood vessel.
Treatment (perform these steps on the donor in a mock-procedure):
To highlight the pathway for a pulmonary artery catheter we will thread a silicon strand through the appropriate cardiac chambers.
PREPARATION: Send a member of your team to the instrument supply tables to fetch some string from one of the supply tables.
1) On your donor, identify the right internal jugular vein and the left subclavian vein (although we will not be threading through those as the heart has been removed from the thorax).
These two veins are the most common entry points for a pulmonary artery catheter, although the left internal jugular and right subclavian as well as the femoral arteries can be used.
2. On the heart, push the silicone cord into the heart through the superior vena cava so that the tip of the simulated 'catheter' enters the right atrium.
3. Grasp the tip of the silicone cord and push the cord inferiorly into the right ventricle through the right atrioventricular (tricuspid) valve.
4. Grasp the tip of the string and push the tip into the pulmonary trunk through the pulmonary semilunar valves.
5. The tip can move into either the left or the right pulmonary artery and continue to a small vessel within the lungs (removed from our donor and those vessels will be examined in the pulmonary section of the course).
Review the course of the pulmonary artery catheter - right internal jugular vein, superior vena cava, right atrium, right atrioventricular (tricuspid) valve, right ventricle, pulmonary semilunar valves, pulmonary trunk, pulmonary artery (left or right).
Outcome:
The pulmonary artery catheter is inserted correctly and you start to receive pressure details from the sensors. The coronary artery occlusions are such that the patient is scheduled for a coronary artery bypass surgery. Post surgery the patient makes a full recovery with restoration of cardiac function sufficient for daily activities.