PERMISSIVE HYPOTENSION IN HYPOVOLEMIC SHOCK RESUSCITATIONCDR GIRARD POIRIER MC USN

Brief Review

Shock - Inability of the body to adequately perfuse end organs which can lead to irreversible damage and death

Hypovolemic shock from hemorrhage is common with severe injury and must be assumed until ruled out.

The numbers: 10% of all trauma patients present with immediate post traumatic hypotension.

Presence of shock in the pre-hospital setting is a strong predictor of mortality

Prehospital Hypotension Predicts Mortality

0

10

20

30

40

50

60

70

120 + 120-90 90-60 60-0

Blunt

Penetrating

SBP

%Mortality

Classes of Hemorrhagic Shock

Class I 750 mL (15%)

● Slightly anxious● Normal blood pressure● Heart rate < 100 / min● Respirations 14-20 / min● Urinary output 30 mL / hour● Warm skin, Normal Cap Refill

Class II 750-1500 mL (15-30%)

● Anxious● Normal blood pressure● Heart rate > 100 / min● Decreased pulse pressure● Respirations 20-30 / min● Urinary output 20-30 mL / hour● Pale, Cool, Cap Refill Delayed

Class III 1500-2000 mL (30-40%)

● Confused, anxious● Decreased blood pressure● Heart rate > 120 / min● Decreased pulse pressure● Respirations 30-40 / min● Urinary output 5-15 mL / hour● V. Pale, Sweaty, Cap refill V Delayed

Class IV >2000 mL (>40%)

● Confused, lethargic● Hypotension● Heart rate > 140 / min● Decreased pulse pressure● Respirations >35 / min● Urinary output negligible

Not All Trauma Patients are Alike

Division into 3 categoriesBluntPenetratingTBI / Head injury

Not All Trauma Patients are Alike

The very young and very old may present differently. Children have a very large reserve capacity Elderly may be on medications that blunt normal

responses. Also may be unable physically to mount a tachycardic response. Finally, many elderly are hypertensive and may present as “normotensive.”

Resuscitation History

Goal was to normalize HR and BP Animal models of the 1950’s and 60’s showed benefit of

aggressive fluid resuscitation. Subsequent review of methods showed numerous flaws

Testing did not accurately reproduce the pathophysiology of an actual exsanguinating trauma patient

Bleeding was tightly controlled as well as BP Overall paucity of controlled trials during that time.

Resuscitation History

Animal models in the 80’s and 90’s better designed. Improved physiologic modeling of actual trauma patients. Volume and duration of hemorrhage now dependent on animals

physiological responses and not the operator. (thrombus formation as well as vasoconstriction)

Experiments with this design showed harm with aggressive fluid resuscitation.

Thought that aggressive fluid mgmt. led to clot disruption, dilution of clotting factors, and reversal of natural vasoconstriction.

Historical Management

2 large bore IV’s 2 liters or saline or LR wide open Continue replacement / maneuvers until normalization of BP and

HR MAST trousers, legs up in Trendelenburg, vasopressors

Control bleeding

The question of possible harm with aggressive resuscitation was actually broached during WWI by US Army Surgeon Cannon and published in JAMA 1917.

Current ATLS Mgmt

Identify and control source of bleeding (direct pressure, tourniquet, suture ligation, or surgery)

Access (2 large bore periph IV’s, IO, CVL) 2 liters of warmed crystalloid initially if hypotension is present

followed by fluids at a 3:1 ratio to accommodate fluid shifts into the interstitial spaces.

Blood products only if no response to initial fluid bolus Prevent Hypothermia

Choice of Fluid

Crystalliod : LR vs NS. LR may be beneficial due to its buffering ability in acidosis and lessening risk of hyperchloremic acidosis. (studies show this benefit only in massive transfusions. No benefit with minimal replacements). Risk of hyperkalemia with use of LR, especially those with renal disease.

Choice of Fluid

Colloid : Theoretically a good idea. Rapidly expands circulating volume and stays in the circulation longer therefore much less third spacing of fluids. However, multiple studies have shown no benefit

2002 Cochrane Review actually showed increased RR of death in those receiving albumin

Saline vs Albumin Fluid Evaluation (SAFE) showed no benefit using albumin.

TBI patients at much higher risk of harm using albumin.

Finfer S, Bellomo R, Boyce N, et al. A comparison of albumin and saline for fluid resuscitation in the intensive care unit. N Engl J Med 2004;350(22):2247–56

Choice of Fluid

Hypertonic Saline. Osmotic agent that can reduce cerebral edema in TBI Stays intravascular for longer period therefore decrease risk of lung

injury and abdominal compartment syndrome (ACS) Human trials to date are inconclusive in showing benefit in the pre-

hospital and initial treatment phases. Subgroup analysis: Blunt trauma receiving massive transfusion did

show decreases risk of ARDS. TBI patients showed no changes in outcomes. Signif increase in mortality in trauma patients who did not receive blood transfusion in the first 24hrs.

Kobayashi L. Hypovolemic Shock Resuscitation. Surg Clin N Am 92 (2012) 1403–1423

Choice of Fluid

LR and transfusions: Currently not advised by the American Board of Blood Banks due to possibility of clot formation in lines. (calcium in LR may bind with Citrate preservative therefore increasing risk of clotting.)

However, recent studies have shown this not to be the case especially in those receiving massive / rapid transfusions. Risk is greater with slower transfusion rates.

New preservatives also in PRBC’s (AS-3)

Michael Vlessides. Study: Ringer’s Lactate Does Not Trigger Clotting Cascade. Clinical Anesthesiology. OCTOBER 2008 | VOLUME: 34:10

Problems with Traditional Mgmt.

Immediate and aggressive fluids to normalize BP with increase blood flow and perfusion pressures to injured areas.

This may disrupt clot formation Will lead to significant third spacing of fluids leading to

pulmonary as well as intestinal edema. Also, increased risk of abdominal compartment syndrome and ARDS

Dilutional coagulopathy: starts at about 750ml of cystalloid admin.

Uncontrolled Hemorrhage :Is Normal Blood Pressure the Target ?

Roberts et al Lancet 2001

Normal blood pressure is not the target !

Bleeding or

Re-bleeding

Hemodilution

Coagulation disorders

Agressive Volume Loading

AnemiaHypothermia Hypoxemia

SAPIncrease Mechanic effect

on vascular clot

Normotensive or hypotensiveresuscitation ?A meta analysis

Permissive hypotension improve survival !

Mapstone J, Roberts I, Evans PH , J TRAUMA 2003, 55 , 571

Favour hypotensive Favour normotensive

What About Human Studies

Landmark Study by Bickel and colleagues most cited. Compared immediate with delayed fluid resuscitation in

penetrating trauma to the abdomen One group received standard fluid mgmt. while the other was

delayed until reaching the OR. Std group received on avg about 2L of saline. Delayed group received 100-200cc)

Overall survival of the Delayed group 70% vs 62% for Standard grp. Also noted was an increase in ARDS, pneumonia, sepsis, and

coagulopathy in the standard group.

Bickell WH, Wall MJ Jr, Pepe PE, et al. Immediate versus delayed fluid resuscitation for hypotensive patients with penetrating torso injuries. N Engl J Med 1994;331(17):1105–9

What About Human Studies Study By Owens and Colleagues

Restrictive fluid resuscitation model following traumatic amputation significantly increased survival.

Owens TM, Watson WC, Prough DS, et al. Limiting initial resuscitation of uncontrolled hemorrhage reduces internal bleeding and subsequent volume requirements. J Trauma 1995;39(2):200–7 [discussion: 208–9]

Study By Morrison and Colleagues Evaluated differences between intra-operative MAP of 50 vs the

standard of 65 in guiding resuscitation. Lower group exhibited less blood loss, less transfusion, improved

early survival as well as improved mortality rates at 30 days Benefits most beneficial in penetrating traumaMorrison CA, Carrick MM, Norman MA, et al. Hypotensive resuscitation strategy reduces transfusion requirements and severe postoperative coagulopathy in trauma patients with hemorrhagic shock: preliminary results of a randomized controlled trial. J Trauma 2011;70(3):652–63

What About Human Studies Restrictive Fluids in Blunt Trauma Paucity of studies Turner and Colleagues compared fluid restriction in the

field vs standard paramedic protocols. Significantly more blood was transfused in the

standard group vs the restrictive group Flawed compliance by paramedics was significant.

Turner J, Nicholl J, Webber L et al. A randomized controlled trial of prehospital intravenous fluid replacement therapy in serious trauma. Health Technol Assess 2000;4:1-57.

What About Human Studies

Head InjuryThere are no human studies that have

evaluated hypotensive resuscitation in the trauma patient with concurrent head injury.

What About Human Studies

Subsequent studies have failed to reproduce consistently these results.

Active debate continues on the uses of permissive hypotension Fluids should never be restricted to patients with a MAP of <40

who are pulseless. These patients have little chance of survival and any fluid admin to maintain some tissue perfusion outweighs any risk of increased hemorrhage risk.

Mortality with Blood Transfusion Data shows a stepwise increase in mortality

2Table

in mortality transfusionwithincreaseStepwise

PRBCs ( )Units

Mortality

al,Como et 15 et al,Huber-Wagner2004 17 2007

Inaba al,et 142 2008

* Uncross-Matched

<710– 22 % 14.81 % 5 30 %

>7 5 %54

11 – 20 30 % 35.1 % <15 5 78 %

>15 5 95 %

–21 40 %50 20 – 29 5 53.7 %

  30 5 %60.4

>40 59 %

* This study includes patients given uncross-matched blood.

What is the Target MAP / SBP

Coronary Autoregulation

50 160

Cerebral Blood Flow Autoreg.

CPP = MAP - ICP

Current RecommendationsOn Target MAP

Most recent guidelines are based on expert opinion and results of animal and human trials.

Goal is to limit the volume of infused fluids and maintain SBP at a minimum safe level.

Target SBP of 80-90mmHg If concurrent brain injury is suspected then a goal of 100mmHg is

recommended to ensure adequate perfusion in the face of possible increased ICP.

Current RecommendationsOn Target MAP

Morrison and Colleagues: Compared MAP of 50 vs 65mmHg (intra-operative) Showed significant reduction in fluid and transfusion requirements in

the lower MAP group. Reduced post operative coagulopathy Statistically lower mortality in the immediate post op phase and

trend toward lower mortality at 30 days

Morrison CA. Hypotensive resuscitation strategy reduces transfusion requirements and severe postoperative coagulopathy in trauma patients with hemorrhagic shock: preliminary results of a randomized controlled trial. The Journal of Trauma. 2011 Mar;70(3):652-63

Current RecommendationsOn Target MAP

Israeli Methods: Commence hypotensive resuscitation when one of the following is met: Altered mental status Loss of radial pulse SBP < 80

Up to 250ml of fluid are given at a time in order to return mental state, regain radial pulse, or SBP to 80mmHg

Review

The Bickel paper is the only randomly controlled trial which enables some conclusions to be drawn on the topic of hypotensive resuscitation. Some harm has been shown with aggressive fluid resuscitation in the field. Hypotensive resuscitation reduces blood loss and transfusion requirements.

Animal studies consistently show that increased SBP in resuscitation increases or restarts bleeding.

Evidence for hypotensive resuscitation in blunt trauma or TBI is sparse and needs further investigation.

Permissive Hypotension in Other Areas of Medicine

Leaking AAA : normal physiologic response to maint SBP 70-80. Treatment is to maint hypotension until proximal control achieved.

Dissecting aneurysm : afterload reducing agents to induce hypotension

Pulmonary contusions treated with fluid restriction Bleeding Duodenal ulcers treated by lowering BP and holding off

on transfusion if possible until definitive treatment.

Final Thought

"There is nothing more difficult to take in hand, more perilous to conduct, nor uncertain in its success, than to take the lead in the introduction of a new order of things, for the innovator has for enemies all of those who have done well under the old, and lukewarm defenders in all of those who may do well under the new.“

- Machiavelli

Questions ?

Anecdotes From Your Practice ?