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II.  Pericardiocentesis

I.  Introduction and Indications
The pericardial space usually contains 15-50 ml of fluid, which serves as lubricant between the visceral and parietal layers of the pericardium.  Several systemic conditions can cause an increased amount of fluid in this space.  Blood can also collect in this space following trauma.  Clinical manifestations are highly dependent on the amount and rate of accumulation of this fluid or blood.  The worst outcome is ventricular collapse causing a precipitous drop in cardiac output, hypotension and possible cardiac arrest.  Using bedside echocardiography allows the emergency physician to rapidly evaluate the pericardium and identify the presence of a pericardial effusion.  Identification of a pericardial effusion causing collapse of the right ventricle is diagnostic of pericardial tamponade and mandates immediate pericardiocentesis.(1-3)

Indications:
Emergent detection of pericardial effusion and visual guidance during drainage.

II.  Anatomy

See cardiac chapter for anatomy details.

III.  Scanning Technique and Sonographic Findings

Commonly attempted ultrasound views for this procedure are the subxiphoid (SX) and parasternal long axis (PSLA) view. However, the optimal position of the probe depends on multiple factors including patient position and body habitus, and oftentimes good results can be achieved with an apical or apical/PSLA approach.
(See also cardiac chapter for more details.)

Subxiphoid
The probe is placed transversely at the left costal margin at the level of the subxiphoid process with the ultrasound beam aimed at the patient’s left shoulder.

• The structures closest to the probe will appear on top of the screen display with the liver being a landmark.
• The liver borders the right ventricle of the heart.
• A pericardial effusion will appear as an anechoic area surrounding the heart.
  
  

Figure 1:  Subxiphoid view of the heart with pericardial effusion.

Parasternal
The transducer is placed in the left parasternal area between the 2nd and 4th intercostal spaces.

• The indicator should be facing the patient’s right shoulder
• Provides good images of left atrium, mitral valve, left ventricle, proximal ascending aorta.
• Look for anechoic area surrounding the heart.
• An apical four-chamber view can be utilized as well.
  
  
  

  	Figure 2		Video clip 1

  
  Figure 2:  Parasternal long axis view with effusion. Video clip 1:  Parasternal view of pericardial effusion

IV.  Pathology

Procedure Technique
The chest wall is prepped and draped in standard surgical fashion.  The ideal site of skin puncture is where the fluid accumulation is closest to the skin surface (chest wall).  A curvilinear or phased array transducer covered in a sterile sheath with frequency ranging from 2.5 – 3.5 mHz is placed on the left anterior chest wall in the parasternal long axis.  Look for the anechoic area on the top of the screen above the right ventricle.  The distance from the transducer to the center of the effusion can be measured using the measuring tool on the machine (see video 5).  A 16 – 18 gauge needle attached to a syringe is inserted adjacent to the transducer through the chest wall and into the pericardium.  For placement confirmation, it is also recommended to use the ‘activated saline technique’.  Here the position of the needle is confirmed by injecting agitated saline through the needle, creating a ‘bubble appearance’ within the pericardial effusion and confirming placement within the fluid-filled pericardial sac.

Figure 3:  Position of the ultrasound probe for parasternal ultrasound-guided pericardiocentesis.

Illustration 1:  Schematic view of pericardiocentesis.

	Video clip 2		Video clip 3

Video clip 2:  Pericardiocentesis, visualizing the needle entrance through the chest wall (apical view).
(Courtesy of B. Hoffmann, M.D.) Video clip 3:  Agitated saline injected into the pericardial effusion. (Courtesy of B. Hoffmann, M.D.)

There are several advantages to performing this procedure with the transducer on the anterior chest adjacent to the needle as opposed to the transducer positioned in the subxiphoid position distant from the needle entry point.  In the subxiphoid view, the heart and hence the effusion you are trying to drain is located perpendicular to the ultrasound beam making it difficult to visualize the needle.  Placing the transducer on the chest wall in the parasternal long axis aligns the beam in the same plane as the structure of interest with close proximity to the needle giving you excellent visualization. In addition to being closer to the skin surface and hence the effusion, the parasternal approach steers clear of other vital structures such as the liver and lung. (1-3)

VI.  References

1. Tayal VS, Moore CL, Rose GA.
   Cardiac. In: Ma J OJ, Mateer JR, eds. Emergency Ultrasound. 1st edition,89-127. McGraw-Hill, New  York, 2003.
   
   
2. Tibbles CD, Porcaro W.
   Procedural applications of ultrasound. Emerg Med Clin North Am.2004;22(3):797-815.
   
   
3. Tayal VS, Kline JA.
   Emergency echocardiography to detect pericardial effusion in patients in PEA and near-PEA states. Resuscitation.2003;59(3):315-8.