A #FOAMed Roadmap to Permissive Hypotension

Included below is a summary of numerous blog posts and podcasts that discuss the sometimes controversial issue of permissive hypotension or minimum volume resuscitation in the bleeding trauma patient.

The Basics

• Idea of keeping BP low in traumatic hemorrhage to avoid “popping the clot”
• Based mostly on data from animal trials and penetrating trauma in humans
• Common practice in most major trauma centers in USA
• The exact approach still remains controversial around the world

Disclaimer: These are highlights as interpreted by the author of this article and should not replace listening to the original podcast or reviewing the background research.  Posts are in chronological order and many of the below podcasts go beyond the scope of permissive hypotension.

EMCrit Podcast 30 – Resuscitation of the Hemorrhagic Shock Patient in Trauma – Aug 15, 2010

In this episode of EMCrit, Dr. Weingart (@Emcrit) and Dr. Richard Dutton (former Director of Anesthesia at Shock Trauma) discuss Dr. Dutton’s approach to resuscitation:

• Dr. Dutton explicitly states this approach is based on experience – NOT evidence
• Goal is a perfusing low BP while avoiding nonperfusing low BPs
• Alternate anesthetic (Fentanyl) with fluids (blood products) to achieve MAP of 65
  • MAP > 65 – check for perfusion (radial pulse)
    • No pulse – give 25mcg of Fentanyl (decreases sympathetic tone)
    • Good pulse –  DO NOTHING
  • MAP <65 give 100mL of fluids/blood products (increases perfusion)
• Avoid large swings in BP
• Younger healthier patients may tolerate SBP as low as 70

EMCrit – ACEP Preview: Hemostasis: Stopping bleeding in crashing trauma pt – Aug 22, 2010

Dr. Weingart outlines his approach to the bleeding trauma patient in a preview to his 2010 ACEP lecture. Many of the concepts are similar to his discussion with Dr. Dutton:

• Approach based on “minimal evidence and strong opinions”
• Dr. Weingart disagrees with the term “permissive hypotension” and suggest “minimal normotension” is more appropriate
• Hemostatic resuscitation = never give fluids that cannot improve oxygenation or coagulation
• Aim for the minimum BP that will achieve perfusion (radial pulse)
• BP is a “crap” measurement of perfusion
• There is NO good human data for permissive hypotension

(This podcast also includes a detailed approach to massive transfusion protocols and coagulation medications)

EMCrit Conference – Hemostatic Resuscitation – Richard Dutton – Jun 11, 2011

A phenomenal lecture on the EMCrit website given by Dr. Richard Dutton.  His main points include:

• Initial fluids should be blood products (1:1:1)
• Crystalloids do NOTHING for trauma patients
• Fluid resuscitation causes transient responders – swings in BP
• Sheep models (Holmes et al, 2002) – fluid vs no fluids – 2x blood loss in fluids group with delayed hemostasis
• Rapid infuser associated with 5x increased mortality in trauma patients (Hambly,1996)
• Due to autoregulation, keeping BP low may be difficult with fluid only approach (Dutton, 2002)
• Hemostatic resuscitation is bigger than BP, must consider coagulopathy

MSc in Trauma Sciences – Permissive Hypotension – Karim Brohi – August 2012

As part of his online Master’s in Trauma Science Dr. Karim Brohi (@karimbrohi), Professor of Trauma Sciences at Barts & the London School of Medicine, discusses permissive hypotension and the evidence that may or may not exist to support its practice:

• Permissive hypotension is one of the 4 pillars of Damage Control Resuscitation
• Permissive hypotension is a necessary evil and NOT a treatment or resuscitation goal
• Hypoperfusion is a  better indicator of mortality than hypotension
• Fluid resuscitation in actively exsanguinating patient is futile
• A BP goal is unattainable (Dutton, 2002 & Bickle, 1994) – goals result in “cyclic hyper-resuscitation”
• Target BP unknown – give small volumes of fluid to obtain perfusing MAP of 50-65
• Overall target = hemostasis and NOT a goal BP
• Once bleeding is controlled optimize perfusion and abandon permissive hypotension

EMCrit – An Interview on Severe Trauma with Karim Brohi – Sep 2, 2012

Dr. Weingart is joined by Dr. Karim Brohi, a world renowned trauma surgeon and founder of trauma.org.  During the episode Drs. Weingart and Brohi discuss in detail Dr. Brohi’s “Master’s in Trauma Science” lecture series:

• Dr. Brohi does not use MAP or BP to gauge resuscitation success
• SBP lower than 70 necessitates fluid/blood product
• DO NOT aim for NBP until hemorrhage is controlled
• Dr. Brohi does not have different BP target in head injury (controversial)
• Dr. Brohi agrees that Dr. Dutton’s approach (above)  is only theoretical until better evidence exists

Practical Evidence Episode 12 – New Trauma Guidelines: ATLS & C-spine – Apr 13, 2013

New changes in the ATLS guidelines are discussed by Dr. Scott Weingart:

• Balanced resuscitation emphasized – eliminate aggressive fluid resuscitation
• 1L crystalloids now recommended over traditional 2L
• DO not give 2L to any shocked trauma patient
• Most trauma patients will have received fluids via EMS

Overall conclusions

• Permissive hypotension is a small part of the larger Damage Control Resuscitation
• A target MAP is unclear but 55-65 seems to be the general consensus
• BP is a poor measure of perfusion
• Not every MAP of 65 is equal – quality of perfusion is just as important as the MAP
• While human evidence for permissive hypotension is lacking – it is common practice in trauma centers

Questions/Controversies

• Is permissive hypotension applicable to all types of trauma or just penetrating?
• What is the best way to gauge perfusion – can we throw away BP cuffs?
• Should resuscitation strategies differ in patients with head injury?
• Is there any role at all for crystalloids in the trauma resuscitation?

More #FOAMed to Check Out

• Trauma.org – Permissive Hypotension – Dr. Ken Mattox – Oct, 2002
  • Another great review of the literature
• Broome Docs – Managing Traumatic bleeding: how can we apply the evidence in smaller hospitals? – Oct 23, 2011
  • Mixed evidence/opinion approach to the bleeding trauma patient in rural hospitals
• Maryland CC Project – Principles of Resuscitation – Oct 17, 2013
  • Dr. Thomas Scalea gives an in-depth review of trauma resuscitation literature
• PHARM Podcast 39 – Haemorrhagic shock in remote settings with the THREE RESUSCITEERS – Sep 13, 2012
  • Review of the challenges of bleeding trauma patient in retrieval medicine
• PHARM – Permissive Hypotension: A Twitter Story – May 13, 2013
  • An amazing twitter discussion by some of #FOAMed’s most prolific tweeters

References / Further Reading