What is the clinical presentation of extracardiac obstructive shock in pulmonary artery catheterization (PAC)?

Updated: Dec 22, 2017
  • Author: Bojan Paunovic, MD; Chief Editor: Karlheinz Peter, MD, PhD  more...
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Pericardial tamponade is an example of this form of shock. Cardiac tamponade results from abnormal rapid fluid accumulation in the pericardial sac. The increased pericardial pressure impairs ventricular diastolic filling, decreasing preload, stroke volume, and CO. This may occur secondary to viral infections, malignancy, trauma, or myocardial rupture. As little as 50 mL of fluid accumulation can begin to impair cardiac filling during systole, leading to a severe reduction in CO. Ventricular filling is impaired throughout all of diastole, thereby causing equalization of all diastolic pressures.

The RAP approximates the RV diastolic pressure, which approximates the PA diastolic pressure, and also approximates PCWP (see image below).

Hemodynamic monitoring can confirm the diagnosis o Hemodynamic monitoring can confirm the diagnosis of pericardial tamponade. Equalization of diastolic pressures on the left and right sides of the heart, elevated right atrial pressure, and Kussmaul sign (ie, increase in right atrial pressure with inspiration) are noted.

The RA waveform shows a minimal X and small and/or absent Y descent, and the mean RAP is elevated. Ppa loses its usual respiratory variation. In pericardial tamponade, the systemic arterial pressure shows evidence of pulsus paradoxus (see image below). Other causes of extracardiac shock include massive PE and tension pneumothorax.

In cardiac tamponade, systemic arterial pressure ( In cardiac tamponade, systemic arterial pressure (Pa) reflects pulsus paradoxus. Right atrial pressure (RAP) is elevated. Pulmonary artery (PA) diastolic pressure equals mean right atrial (RA), right ventricular (RV) diastolic, and wedge pressures.

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