Editing Pericardiocentesis (section)

== Anatomy and physiology ==

The [[pericardium]] is a fibrous sac surrounding the heart composed of two layers: an inner visceral pericardium and an outer parietal pericardium.<ref name=":m1">{{cite journal |last1=Reyaldeen |first1=Reza |last2=Chan |first2=Nicholas |last3=Lo Presti |first3=Saberio |last4=Fava |first4=Agostina |last5=Anthony |first5=Chris |last6=Rodriguez |first6=E. Rene |last7=Tan |first7=Carmela D. |last8=Saliba |first8=Walid |last9=Cremer |first9=Paul C |last10=Klein |first10=Allan L. |title=Pericardial Anatomy, Interventions and Therapeutics: A Contemporary Review |journal=Structural Heart |date=1 November 2021 |volume=5 |issue=6 |pages=556–569 |doi=10.1080/24748706.2021.1989531 |language=en |issn=2474-8706|doi-access=free }}</ref>  The area between these two layers is known as the pericardial space and normally contains 15 to 50 mL of serous fluid.<ref name=":m2">{{cite book |last1=Roberts |first1=James |title=Roberts and Hedges' clinical procedures in emergency medicine and acute care |date=2019 |publisher=Elsevier |location=Philadelphia |isbn=978-0323547949 |edition=7th}}</ref>  This fluid protects the heart by serving as a shock absorber and provides lubrication to the heart during contraction.<ref name=":m1" /><ref name=":m2" />

The elastic nature of the pericardium allows it to accommodate a small amount of extra fluid, roughly 80 to 120 mL, in the acute setting.<ref name=":m2"/>  However, once a critical volume is reached, even small amounts of extra fluid can rapidly increase pressure within the pericardium.  This pressure can significantly hinder the ability of the heart to contract, leading to [[cardiac tamponade]].  If accumulation of fluid is slow and occurs over weeks to months, the pericardial sac can tolerate several liters of additional fluid without substantially hindering the ability of the heart to pump.<ref name=":m2"/>