Shock

Question 1

shock

Answer 1

• physiologic state characterized by a systemic reduction in tissue perfusion resulting in decreased tissue O2 delivery
• initially reversible
• rapidly irreversible –> cell death, end organ damage, failure of multiple organ systems and death
• pre-shock and overt shock

Question 2

determinants of blood pressure

Answer 2

•CO = HR x SV
SV - preload, myocardial contractility, afterload
•TPR (SVR) - vessel length, viscosity, radius

Question 3

hypovolemic shock

Answer 3

• decreased preload
• CO falls when preload drops
• result of hemorrhage and/or other fluid loss (dehydration, pancreatitis)
• CVP down due to loss of fluid
• CO down due to loss of fluid
• SVR up

Question 4

cardiogenic shock

Answer 4

• pump failure
• decreased CO
• cardiomyopathic causes, arrhythmias, severe valvular disease, massive PE, cardiac tamponade and others
• CVP up due to nothing moving
• CO down due to pump failure
• SVR up

Question 5

distributive shock

Answer 5

• vasodilatoryshock
• severe decrease in SVR
• increased CO
• common cause is septic shock, but also includes anaphylaxis and neurogenic shock following CNS injury or spinal cord injury
• CVP down due to vasodilation, or stays the same due to capillary leak of fluid into tissues (forming edema) and pleral and peritoneal spaces (third spacing of fluids)
• CO up due to vasodilation
• SVR down due to vasodilation

Question 6

common features of shock

Answer 6

1. hypotension
   - systolic <90 mmHg or MAP <65 mmHG
2. cool, clammy skin
   - redistribution by vasoconstriction of blood to vital organs
   - distributive shock - sepsis - flushed warm skin
3. oliguria
   - shunting of renal blood flow to vital organs, objective measure of intravascular volume depletion
   - orthostatic hypotension is a sign of volume loss
4. change in mental status
5. metabolic acidosis
   - accumulation of lactic acid,lactate production increased due to anaerobic metabolism

Question 7

treatment of shock

Answer 7

• IV fluids

* vasopressors for MAP <65 mmHg

Question 8

phenyephrine

Answer 8

• purely alpha adrenergic

* vasoconstriction –> increase in SVR

Question 9

norepinephrine

Answer 9

• alpha 1 and beta 2
• vasoconstriction and an increase in CO
• first line for shock

Question 10

epinephrine

Answer 10

• beta 1 and beta 2 and alpha 1
• low doses increase CO because beta 1 inotropic and chronotropic effects, while alpha 1 vasoconstriction offset by beta 2 vasodilation
• at higher doses alpha 1 predominates over beta 2 –> increase in SVR and CO
• first line for anaphylaxis

Question 11

dopamine

Answer 11

• 1-2 mcg/kg per minute, acts on dopamine 1 receptors in the renal, mesenteric, cerebral and coronary beds –> selective vasodilation
• 2-5 mcg/kg per minute have variable effects on hemodyanmics in individual patients
• 5-10 mcg/kg per minute, also stimulates beta 1 receptors –> increased CO
• > 10mcg/kg per minute, predominant effect is to stimulate alpha adrenergic receptors –> vasoconstriction and increased SVR
• hypotension due to spesis or cardiac failure, but not first line for either

Question 12

dobutamine

Answer 12

• no vasoconstrictor effects on the peripheral vasculature
• bet 1 receptor producing inotropic and chronotropic effects on the heart
• minimal alpha and beta 2 receptor effects may result in overall vasodilation with decreased SVR
• severe, medically refractory heart failure and cardiogenic shock

Question 13

vasopressin

Answer 13

• sometimes added to norepinephrine therapy in severe refractory septic shock
• only in a fixed dose, not titrated
• vasoconstriction and increased SVR