From the Guidelines
Wedging in a Pulmonary Artery Catheter (PAC) refers to the process of advancing the catheter until its tip becomes lodged in a small pulmonary artery branch, creating an occlusion that allows for measurement of pulmonary capillary wedge pressure (PCWP). This process is crucial for estimating left atrial pressure and guiding therapy in patients with severe diffuse pulmonary pathology or ongoing haemodynamic compromise not resolved by initial therapy, as noted in the guidelines on the diagnosis and treatment of acute heart failure 1. Some key points to consider when wedging a PAC include:
- The catheter is advanced until its tip becomes lodged in a small pulmonary artery branch, at which point the balloon at the catheter tip is inflated with a small amount of air to help carry the catheter forward with blood flow until it lodges in a vessel of similar diameter.
- Proper wedging is confirmed when the pressure waveform changes from a pulmonary artery pattern to a wedge pattern, characterized by lower pressure, loss of dicrotic notch, and a more attenuated waveform.
- It's crucial to deflate the balloon immediately after obtaining measurements (within 10-15 seconds) to prevent pulmonary infarction, and never to forcibly wedge the catheter by advancing it with the balloon inflated, as this can cause vessel rupture. However, it's also important to note that PCWP is not an accurate reflection of left ventricular end–diastolic pressure (LVEDP) in patients with certain conditions, such as mitral stenosis, aortic regurgitation, ventricular interdependence, high airway pressure, or stiff LV, due to factors like left ventricular hypertrophy, diabetes, fibrosis, inotropes, obesity, or ischaemia, as mentioned in the guidelines 1.
From the Research
Definition of Wedging for a Pulmonary Artery Catheter (PAC)
- Wedging for a PAC refers to the process of positioning the catheter in a pulmonary artery branch until it meets resistance, indicating that the catheter tip is wedged in a small artery 2.
- This technique is used to measure pulmonary artery wedge pressure (PAWP), which is an estimate of left atrial pressure 3.
Purpose of Wedging
- The primary purpose of wedging is to obtain an accurate measurement of left atrial pressure, which is essential for assessing cardiac function and guiding fluid management 3.
- Wedging also allows for the measurement of pulmonary artery pressure, which can help diagnose and manage pulmonary hypertension 4.
Complications and Risks Associated with Wedging
- Wedging can cause a decrease in cardiac output and systemic arterial blood pressure, particularly in patients with lung disease 3.
- There is also a risk of pulmonary artery rupture, which is a rare but major complication 2.
- Additionally, wedging can lead to entrapment or knotting of the catheter, which can be life-threatening if not recognized and treated promptly 5.
Factors Influencing Wedging
- Patient factors, such as gender, height, and weight, can influence the distance between the TEE position and the wedge position 2.
- The technique used for wedging, such as balloon inflation, can also affect the measurement of pulmonary artery wedge pressure 6.
- The presence of chronic lung disease can modify pulmonary hemodynamics during wedging, and caution should be exercised when interpreting pressure measurements in these patients 6.