Shock series part 5 of 6- Obstructive Shock

Part 5 of 6 - Obstructive Shock

Recapping: Shock is a syndrome characterised by poor cellular perfusion. It can be preceded by

1. blood volume loss (Hypovolaemia),
2. obstruction of blood flow into the heart (obstructive),
3. failure to pump (cardiogenic), or
4. available blood being maldistributed (distributive).

Over the last week we have covered Distributive shock and hypovolaemia.
Today we will review obstructive shock.
As the name implies, obstructive shock is a poor tissue perfusion because of a blockage (obstruction) to blood returning to the heart. Unlike maldistribution related distributive shock, where poor venous return is caused by vasodilation; the size of the venous space plays no role in obstructive shock.
A physical blockage to blood entering the right heart can manifest in chest trauma patients due to two primary conditions.
Tension pneumothorax and Pericardial Tamponade

In both conditions the heart is compressed or shifted by pressure that inhibits blood return. The mechanical pumping of the heart continues in vane , but with no blood coming into the heart, then cardiac output is all but impossible.
Treatment of obstructive shock is to remove the obstruction. In tension pneumothorax a needle is placed into the chest to release trapped pleural pressure (thoracentesis). In pericardial tamponade, blood collects in the space between the fibrous pericardial membranes, and compresses the Vena Cava and myocardium.

 Doctors trained in the technique can perform pericardiocentesis, which involves the insertion of a needle below the ribs, and into the engorged pericardial sac.  Alternatively, an open thoracotomy is performed to open the pericardial sac .
There, blood (or serous fluid) is aspirated to release pressure.

Obstructive shock occurs quickly, but with rapid assessment, it's cause can be quickly identified and managed. Restoration of cardiac output, and blood pressure is the aim of treatment. Secondary management may include surgery to repair bleeding pericardium, or a formal chest drain to aid in the recovery of pneumothorax.