Shock

• Shock


  An abnormality of the circulatory system that results in inadequate organ perfusion and tissue oxygenation
• There is an imbalance between the supply and demand of the body in shock
• The body demands for oxygen to function well but then in cases of shock, there is an inadequate supply of blood to be delivered to the body
• Blood carries hemoglobin which is a carrier of oxygen which is the common metabolite for most mechanisms in the functions of different body system
• The first step in managing shock in trauma is to recognize its presence
• No single vital sign, no laboratory test on its own can definitively diagnose shock
• Cardiac Output (CO)


  Volume of blood that is pumped by the heart per minute

  
• Stroke Volume (SV)


  Amount of blood being pumped out per heartbeat

  
• Determinants of Stroke Volume

  • Preload
  • Myocardial contractility
  • Afterload
• Preload


  Initial amount of blood present in the Right Atrium, Volume of venous blood return to the left and right sides of the heart, Determined by venous capacitance, volume status, venous flow

  
• Myocardial contractility


  The pump that drives the system, if there will be a defective pump → contractility is compromised
• Afterload


  Also known as peripheral vascular resistance, Resistance to the forward flow of the blood, High resistance from the vasculature = stroke volume diminished
• Early circulatory response to blood loss

  Progressive vasoconstriction of cutaneous, muscular, and visceral circulation to preserve blood flow to the kidneys, heart, and brain

  
• Effects of vasoconstriction


  • Cutaneous: patient is pale, limits blood flow to skin
  • Muscular & Visceral: GI tract compromised, blood shunted away from organs
  • Kidneys: ↓ urine output
  • Brain: diminished sensorium
  • Heart: last organ to have diminished blood supply
• Usual response to acute circulating volume depletion is an increase in heart rate in an attempt to preserve cardiac output
• Tachycardia is the earliest measurable circulatory sign of shock
• Don't rely solely on systolic BP
• Poorly oxygenated cells will shift to anaerobic metabolism, hence formation of lactic acid leading to metabolic acidosis
• The most effective method of restoring adequate cardiac output end-organ perfusion, and tissue oxygenation is to restore venous return to normal by locating and stopping the source of bleeding

  
• Vasopressors are contraindicated as a first-line treatment of hemorrhagic shock because they worsen tissue perfusion
• Recognition of shock


  • Look at pulse rate, pulse character, respiratory rate, skin perfusion, and pulse pressure
  • Any injured patient who is cool to the touch and is tachycardic should be considered to be in shock until proven otherwise
• Massive blood loss may produce only a slight decrease in initial hematocrit or hemoglobin concentration
• A normal hematocrit does not exclude significant blood loss
• Most injured patients in shock have hypovolemia, but they may suffer from cardiogenic, obstructive, neurogenic and/or rarely septic shock
• Hemorrhagic shock


  Hemorrhage is the most common cause of shock
• Normal adult blood volume

  7% of body weight
• Estimated Body Weight (EBW)

  • Male: 50 kg + 2.3 kg for every inch over 5 feet
  • Female: 45.5 kg + 2.3 kg for every inch over 5 feet
  • 1-11 months: (0.5 x age in months) + 4
  • 1-5 years: (2 x age in years) + 8
  • 6-12 years: (3 x age in years) + 7
• Classes of hemorrhagic shock

  • Class 1 (<15%)
  • Class 2 (15-30%)
  • Class 3 (31-40%)
  • Class 4 (>40%)
• Class 1 hemorrhage


  • Exemplified by donating 1 unit of blood, Compensatory mechanism will restore blood volume within 24 hours, No changes in vital signs, No intervention needed
• Class 2 hemorrhage


  • Uncomplicated hemorrhage requiring crystalloid fluid resuscitation, Tachycardia, tachypnea, decreased pulse pressure, Subtle CNS changes, Mildly affected urinary output
• Class 3 hemorrhage


  • Complicated hemorrhagic state requiring at least crystalloid infusion and most will need blood products, Marked tachycardia and tachypnea, Significant changes in mental status, Measurable fall in systolic BP

  
• Class 4 hemorrhage


  • Degree of exsanguination is immediately life-threatening, Marked tachycardia, significant decrease in BP and very narrow pulse pressure or unmeasurable diastolic BP, Markedly depressed mental status, Cold and pale skin, Require rapid transfusion and immediate surgical intervention
• The most effective method of restoring CO, end-organ perfusion and tissue oxygenation is restoring venous return to normal by locating and stopping source of bleeding
• Rapidly determine the site of blood loss

  1. On the floor

  2. Chest

  3. Abdomen

  4. Pelvis and retroperitoneum

  5. Extremities
• Diagnostic procedures to determine site of blood loss

  • Chest: whitening of thorax for hemothorax or pleural effusion
  • Abdomen: FAST for fluid in abdominal cavity
  • Pelvis: possibility of pelvic fracture
  • Extremities: displaced fractures can cause significant blood loss
• Cardiogenic shock


  Myocardial dysfunction caused by blunt cardiac injury, cardiac tamponade, air embolus, or myocardial infarction
• All patients with thoracic trauma need continuous ECG monitoring to detect injury patterns and dysrhythmias
• Cardiac enzymes will give basis in diagnosis and treating patients in the ER
• Cardiac tamponade


  Commonly seen in patients with penetrating thoracic injury
• Femoral fracture


  • Can cause a blood loss of 1.5 L