Shock (Corbett) - 11/11/16

Question 1

What is shock?

Answer 1

Inadequate O2 organ perfusion and delivery of nutrients to the tissues

(low BP doesn’t necessarily mean shock)

Initially may be reversible, but life-threatening if not treated promptly

Question 2

Shock is often accompanied by ______________.

Answer 2

Hypotension

MAP < 60 mm Hg (normal 70-110) in previously normotensive patient

Patients can maintain their BP in normal range despite profound tissue hypoperfusion through compensatory mechanisms.

Question 3

Two compensatory responses to hypotension

Answer 3

1. Baroreceptor Response
   
   1. Decreased baroreceptor firing in carotid sinus and aortic arch
   2. Decreased firing in inhibitory neurons
   3. Increased sympathetic tone
   4. Increased HR, contractility, vasoconstriction
2. Renin-angiotension system
   
   1. Vasoconstriction
   2. Sodium reabsorption

When compensatory response fails: irreversible shock state = imminent

Question 4

What is the benefit of the compensatory response?

Answer 4

• Metabolic rates of heart and brain are high with low nutrient stores, therefore they are critically dependent on blood flow for O2 delivery
• Fall in CO –> diversion of blood from non-essential vascular beds (skin, muscle, GI tract)

Question 5

Features of low CO shock (3)

Answer 5

• Cool, clammy skin, pale or gray color
  
  • Vasoconstriction shunts blood from periphery to vital organ
  • Capillary refill time > 3 sec
  • Nail beds: clubbing
• Mental status changes
  
  • Agitation/anxiety; “sense of impending doom”; confusion; obtundation
• Metabolic Acidosis (low ATP levels)
  
  • Induces tachypnea
    
    • Inc. in respiratory rate (compensatory respiratory alkalosis)
  • Lactic acid production exceeds ability of liver to clear lactate
  • Anaerobic metabolism rapidly worsens acidemia

Question 6

Pericardial Tamponade

Answer 6

Question 7

Clinical Features of Pericardial Tamponade

Answer 7

Beck’s Triad:

• Muffled HS - b/c sound cannot travel fluid barrier
• JV Distention - pressure around heart is impeding venous return, raising venous pressure
• Hypotension

• Pulsus paradoxus (82% - sensitivity of physical exam)

Question 8

Mechanism of pulsus paradoxus

Answer 8

Pressure from fluid will decrease compliance of heart wall …

IV septum only place that doesn’t feel the pressure so gets shifted as right side fills

Left side of heart can’t fill as much now –> lower vol –> lower pressure

Question 9

Tension Pneumothorax

Answer 9

Air is between parietal and visceral wall… lung is pushed away and separated from chest wall

Clinical Features

• Absent breath sounds
• JVD
• Tracheal deviation

Question 10

Distributive Shock (3)

Answer 10

• Septic Shock
  
  • Decrease in peripheral vascular resistance despite increased vasopressors
• Neurogenic Shock
  
  • Loss of sympathetic tone secondary to spinal cord injury
• Anaphylactic Shock
  
  • Histamine, leukotriene C4, prostaglandin D2 release –> profound vasodilatation

Question 11

Cardiogenic, Hypovolemic, Obstructive, Septic Shock

BP (low/high?)

HR (low/high?)

Skin (cool, clammy, warm, dry?)

Lungs (congested vs clear?)

Heart Sound?

JVD (Yes/No?)

Answer 11