"This used to be merely intuition...even a minute or two at low MAPs may be too much and certainly waiting 20 minutes for pharmacy to send up a drip is probably way too long...and your kidneys may actually be getting damaged in that short period of time." - Scott Weingart, MD
Who is Scott Weingart, MD?
Courtesy of Scott Weingart, MD

Scott D. Weingart, MD FCCM FUCEM DipHTFU

Scott is an ED Intensivist from New York. He did fellowships in Trauma, Surgical Critical Care, and ECMO.

He is currently an attending in and chief of the Division of Emergency Critical Care at Stony Brook Hospital. He is a clinical associate professor of emergency medicine at Stony Brook Medicine and an adjunct associate professor at the Icahn School of Medicine at Mount Sinai.

He is best known for talking to himself about Resuscitation and Critical Care on a podcast called EMCrit, which has been downloaded > 19 million times. EMCrit Twitter Team @emcrit
What is a MAP? (Mean Arterial Pressure)

Average pressure in a patient’s arteries during one cardiac cycle
Really good number to measure organ perfusion
Systolic BP is a useless measurement in super hypotensive patients
Calculations:

MAP = CO x SVR
MAP = SBP + 2(DBP)/3



Low MAPs should be treated as an Emergency = Requires Good Nursing!!
What is a minimal MAP for adequate perfusion?
No one knows!! 
Minimal MAPs (what we think and have made up) to adequately perfuse 3 main organs. Use this as a loose guideline. May have to individualize for each patient.
 

Brain

MAP 60-65
but can go lower for a bit of time before damage
MAP 40 starts to have altered mental status


Heart

MAP 60-65


Kidney

MAP 65
super sensitive to low MAPs
May not be able to measure output in ED if kidneys were hit hard and due to shunting



In the ED, we like MAP 65...

because the organs will have minimal perfusion and we often don't know what the medical history is or have had 24 hours of patient observation.

 Normal MAP + Low SBP + Normal DBP = Okay

Organs are being perfused

Low MAP + Normal SBP + Low DBP (Ex: 100/20) = Badness

Can be in cardiac arrest if you don't pay attention and do something ASAP

Low MAP, How long is too long?

New Anesthesia literature that shows a minute or two may be too much.
Concern for kidney injury
Hearts may dislike low MAP esp. Pts with cardiac history.
React quickly to low MAPs (MAP 40s and 50s)

No barrier to treating low MAPs
No Harm in treating low MAPs
Can start peripheral NE drip and if in 45 minutes, NE drip is titrated off - no harm done to Pt


Wait and See approach with fluids doesn't work

Fluids don't last to maintain MAPs, it will drop 30-60 minutes later
Harm to keep Pt at low MAPs



"Permissive Hypotension" A confusing term

No one is really in a permissive hypotension state lower than the minimal MAP 65

Trauma

A confusing term because the trauma studies still show that a Pt is being perfused and hovering around MAP 60-65

Term came about because fluids were restricted instead of giving bunch of fluids - but BPs were normal
Some say the clot is formed so don't break the clot - still BPs are at MAPs that we talked about
Bickell study on penetrating trauma Scott mentioned
Permissive hypotension/hypotensive resuscitation and restricted/controlled resuscitation in patients with severe trauma by D. Kudo


Rick Dutton Approach for penetrating trauma management as described by Scott

Keep your patient from being vasoconstricted
Organs are not being perfused with higher MAP but in fact exsanguinating due to vasoconstriction
Manage by hovering around a MAP 60-65 and perfuse organs

MAP <65 give product (like 1 unit of PRBC, FFP, etc.)
MAP >80 (or whatever upper limit you decide), give them some anesthetic and dilate them.

Fentanyl is an indirect vasodilator