In the event of obstructive shock or pulseless electric activity with visualized or suspected tamponade, pericardiocentesis is considered standard of care. There are many approaches to performing a pericardiocentesis, including the classically taught blind subxiphoid approach, which is associated with high rates of morbidity and mortality.5 More recent image-guided approaches employ echocardiography-guided techniques that identify the location and distribution of fluid, and perform pericardiocentesis closest to the area largest fluid accumulation.
Most of these guided techniques involve in-plane visualization of the needle in either a subxiphoid, apical, or parasternal approach. Studies have shown that the subxiphoid approach has a higher risk of injury to the liver, heart, and IVC, with complication rates up to 20% depending on the study.6
The apical approach involves locating the cardiac apex and inserting the needle 1 cm lateral to the apex, with the point directed toward the effusion and in-line with the ultrasound probe, taking care to avoid the lingula. Studies have shown that complication rates with this approach are around 3%.7
Recent studies also suggest that in-line medial-to-lateral parasternal approaches may have minimal complications. However, when employing this approach, care must be taken to avoid the internal mammary artery, which can be identified using color-flow Doppler echocardiology.6
In general, bedside ultrasound is a quick and useful tool to evaluate for pericardial effusion and signs of tamponade physiology. When present, tamponade, a clinical diagnosis, is the likely cause of shock in the hemodynamically unstable patient with circumferential pericardial effusion.
While most cases of pericardial effusion are found incidentally, a stepwise approach to evaluate for tamponade is to quickly look for signs of early right-sided diastolic collapse or ventricular interdependence, as well as a plethoric IVC. For patients who have tamponade requiring pericardiocentesis, the ultrasound-guided apical or parasternal approaches have been shown to have fewer complications compared to the subxiphoid approach.