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Thu Jun 30 02:56:32 BST 2005

nice review and discussion.

E

Errington C. Thompson, MD, FACS, FCCM
Author - Letter to America
Trauma/Surgical Critical Care
Mission Hospitals
Asheville, NC
ecthompson at msn.com<mailto:ecthompson at msn.com>
www.erringtonthompsonmd.com<http://www.erringtonthompsonmd.com/>

Don't think you are
Know you are
                  - Morpheus (The Matrix)
  ----- Original Message ----- 
  From: Karim Brohi<mailto:karim at trauma.org> 
  To: 'Trauma & Critical Care mailing list'<mailto:trauma-list at trauma.org> 
  Sent: Wednesday, June 29, 2005 2:54 AM
  Subject: Permissive hypotension & traumatic brain injury

  > This is dangerous supposition.  The clinical evidence to date is that
  > hypotension in the resus phase is a strong prognostic indicator of bad
  > outcomes in acute traumatic head injury. 

  > Dr John L Holmes
  > Director Emergency Medicine,  Mater Adult Hospital,  Brisbane,  Australia

  John,

  Of course you are right - hypotension worsens outcome from traumatic brain injury.

  However this is not quite the issue here.  The question must be stated differently:

  "In the shocked patient with a concomitant traumatic brain injury, does setting a 'normal' target blood pressure improve outcome?'

  The answer to this question is in no way clear cut and tends to the answer "no".

  Multiple studies of fluid resuscitation in trauma patients (or animals) with on-going blood loss (blunt or penetrating) show that it
  doesn't matter what target blood pressure you set, you won't be able to achieve it, despite the volume of fluid you administer.  We
  have all seen this in the classic see-saw vitals chart of the transient responder, but I think it is best illustrated in a study by
  Tom Shires which, as I read it, was specifically designed to disprove permissive hypotension and is in fact titled:  "Improved
  Survival with Early Fluid Resuscitation Following Hemorrhagic Shock." (Alberto S. Santibanez-Gallerani[..] G. Tom Shires, World J.
  Surg. 25, 592-597, 2001)

  In it the authors induced haemorrhage in 80 rats and then randomized them to early (15 mins), delayed (60 mins) or no fluid
  resuscitation.  Rats were bled down to a blood pressure of 20mmHg (35% blood volume), and needless to say those rats left
  unresuscitated over the 3 hours of the experiment had a higher mortality - thus proving that prolonged extreme hypotension is bad
  for you.  Note here that no advocate of permissive hypotension suggests that a blood pressure of 20mmHg is acceptable or that 3
  hours is an appropriate time period for any level of hypotension.

  What is really interesting about this study is the data in the figures.  The first is of the blood pressure measured at time points
  across the three groups:

  Regardless of whether animals received early, delayed or no resuscitation, their blood pressure at different time points was exactly
  the same.  The next chart of mortality against volume of resuscitation fluid is equally interesting:

  Mortality in the delayed group was higher - we expected that from the severity & duration of the hypotension.  But look!!  - as the
  volume of crystalloid increases in the early resuscitation group, mortality increases - remember with no improvement in blood
  pressure.

  So here is the father of fluid resuscitation, performing a study essentially to disprove permissive hypotension and has had to
  induce a severe and prolonged hemorrhage to prove it - and yet he is unable to produce a blood pressure difference between the
  groups and moreover, the more fluid administered to the animals, the higher the mortality.

  But that's just rats you say. Well pig studies show the same thing, but you'd probably like to know about humans... Well, even in
  Ken's study of penetrating torso trauma, whether patients were randomized to standard or limited resuscitation, their admission
  blood pressure was the same - 70mmHg - but the standard resuscitation group got 2500mls and the limited resuscitation only 375 mls.
  A study from Shock Trauma (Hypotensive resuscitation during active hemorrhage: Impact on in-hospital mortality,  Dutton RP,
  MacKenzie CF, Scalea TM J Trauma 2002 June;52(6):1141-1146) randomized patients to a target BP of 70mmHg or 100mmHg.  They were
  unable to achieve these target BPs and all patients had a BP of 100-110mmHg (in fact the BP was higher in the target 70mmHg group).
  Several other studies, including the classic canadian prehospital IV vs no-IV study also show the lack of effect of volume loading
  on the blood pressure in the actively hemorrhaging patient.

  So in the patient who is actively bleeding, there is no doubt that the hypotension is bad for the brain.  BUT GIVING FLUIDS WILL NOT
  CORRECT THE HYPOTENSION.  We know that fluid resuscitation of itself is not good for you (activation of inflammation, coagulation,
  endothelial injury, interstitial oedema, hypothermia etc etc etc).  If it's not actually helping the blood pressure - how are you
  helping the brain?

  Karim

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Permissive hypotension & traumatic brain injury