Shock 848th Forward Surgical Team

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Shock848th Forward Surgical Team
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Introduction

• Combat-Related trauma may present with classical
  symptoms of hemorrhagic shock following rapid
  exsanguination from major vascular structures
• Hemorrhagic shock is the most common cause of
  death among combat casualties
• Early recognition, control of the hemorrhage
  source by effective first aid, and rapid volume
  resuscitation with IV fluids are the ideal
  preparation for definitive surgical repair
•  

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Physiological Consequences of Hemorrhage

• Adverse effects of hemorrhage on young, healthy
  soldiers are directly related to two primary
  factors
• 1.)     Decreased intravascular volume
• 2.)     Inadequate oxygen-carrying
  capacity

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Cardiovascular Response

• The immediate response to the fall in venous
  return to the heart, and decrease in pressure to
  the aortic arch and carotid baro-receptors is a
  diffuse activation of the sympathetic nervous
  system
• Release of catecholamines from adrenal medulla
• Increase in heart rate and contractility
• Increase in systematic vascular resistance due to
  vasoconstriction of skeletal muscles and viscera
• This response preserves central organs
• Heart brain at the expense of peripheral organs

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Fluid Compartment Shifts

• After a combat casualty sustains a major
  hemorrhage, restoration of the intravascular
  fluid compartment may require many hours as
  interstitial fluid (extra-vascular) is drawn into
  the intravascular compartment

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Extra-vascular Fluid Loss

• Combat casualties presenting for care several
  hours after being injured may suffer from
• Hemorrhage-induced intravascular volume depletion
• Preexisting depletion of the extra-cellular fluid
  compartment that is caused by concomitant
  dehydration, secondary to environmental or
  nutritional factors

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Extra-vascular Fluid Loss Cont.

• Because crystalloids (Normal Saline (NS)
  /Lactated Ringers (LR)) are distributed through
  the body water, a 1950's dog study showed 3-4
  ml/1 ml blood loss is required to replace
  intravascular volume
• Recommendations for replacing the third-space
  fluid sequestration is four, six, and eight
  ml/kg/hr for minimal, moderate, and severe trauma
  (respectively) in addition to estimated hourly
  maintenance fluids

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Oxygen Transport

• Hemorrhage interferes with normal tissue
  oxygenation by two mechanisms
• 1.) The anemic (Inadequate oxygen carrying
  capacity)
• 2.) The hemorrhagic (Inadequate tissue perfusion)
• In the setting of severe hemorrhage, however,
  reduced hemoglobin content is rarely the cause of
  tissue hypoxia
• A 20-year-old healthy soldier can lose 40-50 of
  his blood volume and hemodynamically compensate
  with cardiac output and vasoconstriction to
  maintain adequate tissue perfusion

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Oxygen Transport

• This example demonstrates blood replacement is
  frequently unnecessary and volume restoration is
  the key
• If the circulating plasma volume is maintained
  then the metabolic consequences of severe
  hemorrhage can be minimized

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Hypovolemia

• Bld Loss Blood Vol. Heart
  Blood Pulse Resp Urine Mental
• Hemorrhage (L.) Lost () Rate Pressure Pressu
  re Rate ml./hr. Status
• Class I lt1 lt15 lt100 Normal Normal or
  14-20 gt30 Slight Increased Anxiety
• Class II 0.75-1.5 15-30 gt100 Normal Decreased
  20-30 20-30 Mild
• Anxiety
• Class III 1.5-2.0 30-40 gt120 Decreased Decrease
  d 30-40 lt15 Anxious
  Confused
• Class IV gt2.0 gt40 gt140 Decreased Decreased
  Rapid Neg Confused
• Shallow Lethargic 
• (Committee on Trauma, American College of
  Surgeons. Advanced Trauma Life Support for
  Physicians Chicago, Ill. American College of
  Surgeons 1989 72. ) 

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Hypovolemia

• Class I (lt15) Suspected blood loss in absence of
  tachycardia or hypotension
• Resuscitate with clear fluids (crystalloids (NS /
  LR)
•  Class II (15-30) Tachycardia without
  hypotension
• Transfuse with crystalloid or colloid, transfuse
  early with continual bleeding
•  Class III (30-40) or Class lV (gt40)
  Hypotension and tachycardia require immediate
  blood volume replacement with crystalloid,
  colloids, and or packed red blood cells

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Venous Access

• Optimal sited for venous cannulation
• Severe hemorrhagic shock may require surgical
  cut-down
• Central venous access
• Penetrating abdominal injuries may involve the
  inferior venacava

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Intravenous Fluid-Delivery System

• Large-caliber, high-efficiency, blood-warming
  units are essential for large-vol. resuscitation
• Level-I (one) can deliver warm fluids at a rate
  of 500 ml/min with an 18 g IV 1000 ml/min with a
  14 g IV
• There is an in-line air vent to prevent an air
  embolus when fluid bag is pressurized

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Resuscitation Fluid Selection

• Best initial therapy for mild to moderate
  hemorrhage 10-30
• Blood products administered to keep pace with
  blood loss and keep hemoglobin gt 7 gm/dl
• Fresh whole blood or Packed Red Blood Cells
  (PRBC)

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Crystalloid Solutions

• 0.9 Normal Saline (NS) or Lactated Ringers (LR)
• Glucose containing fluids
• Dextrose

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Colloid Solutions (Dextran, Hespan, Albumin)

• Rapidly replenishes intravascular compartment
  with smaller fluid volume than crystalloids
• Gives more prolonged expansion of the plasma
  volume and less peripheral edema
• Has Disadvantages

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Supplemental Therapeutic Measures

• Control of bleeding and rapid infusion of
  crystalloids and blood are essential in combat
  casualty treatment of shock
• Other Treatments

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Patient Position

• Trendelenberg's position
• Raised legs may increase blood return to heart
  without increasing intracranial pressure

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Pneumatic Antishock Garment

• A compression device first known as the Military
  Anti-Shock Trousers (MAST) introduced by the U.S.
  Army during the Vietnam War

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Pneumatic Antishock Garment

• Studies have demonstrated significantly reduced
  survival in patients treaded with MAST garments
  for chest hemorrhage not compressed by the
  trousers
• MAST garments in combat may be useful in
  stabilizing fractures of pelvis and long bones of
  the legs

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Supplemental Oxygen

• Beneficial in multiple or massive injury
• Flail chest, fat embolus and other injuries
  associated with impaired oxygenation
• Expectations of tissue oxygenation in the
  presence of hypovolemic shock is unrealistic
• Hemoglobin oxygenation in young combat casualties
  is already maximally saturated from
  hyperventilation from the injury

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Vasopressors

• Transiently supporting blood pressure with
  vasoconstrictors until volume replacement or
  control of bleeding is possible
• Intense vasoconstriction is typical hemostatic
  response to hemorrhagic shock and may be
  primarily responsible for adverse consequences of
  hypovolemia (acidosis and tissue hypoxia) 

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Hyperthermia and Dehydration

• Physical exertion and inadequate supplies on the
  battlefield combine to develop heat injury and
  dehydration
• Coincidental trauma and hemorrhage
• Rapid replacement of intravascular and
  intracellular fluids

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Hypothermia

• Problem afflicting trauma victims
• Decreases renal blood flow 75
• Temperatures lt30 Degrees C
• Restoration of fluid deficits
• Re-warming the patient frequently develops
  metabolic acidosis
• Fluid resuscitation maintenance will correct
  acidotic state
• Treat acidosis with sodium bicarbonate

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Hemorrhagic Shock and Head Injury

• Hypovolemia and head injury is ominous
• Increased intracranial pressure and hypotension,
  secondary to hypovolemia, further decreases
  cerebral perfusion pressure and potentiates
  cerebral ischemic injury
• When colloid solutions have been advocated, the
  blood-brain barrier may have been damaged
  contributing to worsening edema with fluid
  resuscitation

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Questions
James Malson CPT