lecture 34

Question 1

State the three key elements of shock.

Answer 1

Shock is a life-threatening condition of circulatory failure that results in inadequate oxygenation of body tissues.

Question 2

Name and describe the four main types of shock and their most common causes.

Answer 2

1. Distributive shock- vasodilation
   - caused by sepsis, anaphylaxis, neurogenic
   - signs: arterial hypotension and tachycardia, signs of tissue hypoperfusion, circulatory shock, normal or high cardiac output, distributive circulatory shock
   - symptoms: hypovolemia and hypotension, as a result of vasodilation and release of inflammatory mediators
2. Hypovolemic shock- loss of plasma or blood dilation
   - caused by hemorrhage, severe burns, severe vomiting and diarrhea
   - signs: arterial hypotension and tachycardia, signs of tissue hypoperfusion, circulatory shock, low estimated cardiac output, low central venous pressure, hypovolemic circulatory shock
   - symptoms: internal or external fluid loss leading to organ failure.
   - hypothermia, coagulopathy, acidosis
3. Cardiogenic shock- ventricular failure
   - causes: myocardial infarction, ventricular arrhythmia, cardiac myopathy, valvular disease
   signs: arterial hypotension, tachycardia, signs of tissue hypoperfusion, circulatory shock, low estimated cardiac output, high central venous pressure, cardiogenic circulatory shock
   - symptoms: low cardiac output and inadequate oxygen transport
4. Obstructive shock- pericardial tamponade
   - causes: cardiac tamponade, pulmonary embolism, pneumothorax
   - signs: arterial hypotension, tachycardia, circulatory shock, low estimated cardiac output, high central venous pressure, obstructive venous pressure
   - symptoms: blockage in blood flow caused by a massive pericardial effusion, cardiac tamponade, or tension pneomothorax

Question 3

Identify the component of gram negative bacteria that mediated septic shock.

Answer 3

Septic shock is a subcategory of sepsis, where circulatory and organ failure are present.

70% of cases of septic shock are caused by infection by endotoxin-producing gram-negative bacillus.

Endotoxin/outer membrane is made of O-antigen, core oligosaccharide, and lipid-A.

LPS causes the release of TNF, IL-1, IL-6/IL-8, NO, and PAF, which cause either local inflammation (low quantities), systemic effects (moderate quantities), and septic shock (high quantities).

Question 4

Describe the role of adrenomedullin in modulating vascular function.

Answer 4

intravascular compartment:
- ADM enhances endothelial barrier function
- ADM-adrecizumab complexes cannot cross the endothelial barrier, effectively trapping ADM in the circulation
- adrecizumab only partially inhibits ADM function

interstitial compartment:
- ADM freely passes the endothelial barrier
- ADM directly induces vascular smooth muscle cell relaxation
- ADM induces endothelial NO release, thereby indirectly causing vascular smooth muscle cell relaxation

Question 5

Define the term edema.

Answer 5

Edema is an accumulation of fluid in interstitial space of body tissues.
- abnormality in the normal filtration, reabsorption, and lymph flow

Often seen as subcutaneous, pulmonary, or cerebral edema.

If filtration > ability to reabsorb + remove fluid via lymph drainage, fluid accumulates in the interstitial space, resulting in the clinical state of edema.

Question 6

State the primary drivers of the movement of fluid into and out of vascular space.

Answer 6

hydrostatic pressure- fluid is pushed out, pressure decreases as you move along

colloid osmotic pressure- fluid is pushed in, pressure remains the same as you move along

net hydrostatic and colloid osmotic pressure- net flow out and in should be equal
- early on, hydrostatic pressure is greater, so fluid moves out (ultrafiltration)
- later on, osmotic pressure is greater, so fluid comes in (reabsorption)

Question 7

Describe the mechanisms and common clinical causes of edema.

Answer 7

Increased capillary permeability
- local causes: cellulitis
- systemic causes: spesis, hypersensitivity reactions

Increased capillary hydrostatic pressure
- local causes: compartment syndrome, chronic venous insufficiency
- systemic causes: heart failure, renal failure, pregnancy

Decreased capillary oncotic pressure
- systemic causes: protein deficient states (nephrotic syndrome, cirrhosis)

Lymphatic obstruction (lymphedema)
- local causes: tumor, trauma, infection (filariasis)

Diagnosis- is the fluid protein rich (exudate) or protein poor (transudate)?

Unilateral (one side, local) or bilateral (symmetric, systemic)?