Permissive Hypotension

You are dispatched to a scene where a 21 year old male has been shot in the chest by an unknown caliber handgun. On exam, you note a single GSW to the chest inferior to the left nipple. His VS are: BP 62/48, HR 138/min, RR 36 and labored. He is agitated and diaphoretic, but is AAOx4. You establish peripheral access and begin administering crystalloid fluid as a bolus. Your transport time to the trauma center is 20 minutes, due to road closures.

How much fluid should you administer en route to the trauma center?

            Captain Walter Cannon introduced the world to the concept of permissive hypotension in penetrating trauma back in 1918 during World War I. Cannon was an Army surgeon who witnessed the poor outcomes of patients who were “resuscitated” to “normal” blood pressures and developed the idea of the tenuous clot.  In 1994, Bickel and colleagues compared low volume resuscitation (300-340 ml) with standard ATLS volumes of 2400 ml.  In a randomized prospective trial, Bickel demonstrated a change in mortality of almost 7% in the low volume resuscitation group. This group also had less complications (ICU length of stay, development of acute respiratory distress syndrome, and abdominal compartment syndrome) compared with the standard resuscitation group.

            This practice of permissive hypotension in penetrating chest trauma is now widely accepted and practiced. The idea of the tenuous clot is real. Increased fluid volumes raise the blood pressure to levels higher than required, resulting in dilution of clotting factors and increased bleeding. The majority of these injuries are in non-compressible sites. Hence, patients end up bleeding more than they would have if we had never touched them in the first place.

            Therefore, consider resuscitating penetrating chest trauma patients to normal mental status.  This holds true for other trauma patients where bleeding is felt to be the cause of hypotension. The vast majority of people will retain normal mental status around 90 mmHg SBP. If the SBP is at least 90 mmHg, consider giving no fluids at all.

Boswell, K.  Menaker, J. Assessment and Treatment of the Trauma Patient in Shock, 2014-11-01Z, Volume 32, Issue 4, Pages 777-795,