Lecture 4 - Trauma, Systemic Implications

Question 1

Circulatory shock

Answer 1

• generalised inequacy of blood flow throughout the body: tissue are damaged
• usually due to an inadequate cardiac output, but sometimes also due to abnormal perfusion pattern

Question 2

4 causes of circulatory shock

Answer 2

• Hypovolemic shock: severe hemorrage, vomiting or diarrhea
• Cardiogenic shock: decreased pumping capacity
• Vasogenic shock: septic shock, anaphylactic shock
• neurogenic shock: decreased sympathetic vasomotor activity
• all ultimately lead to decreased arterial pressure. And thus decrease perfusion of tissues and organs

Question 3

Response to shock

Answer 3

• decrease atrial receptor activity and decrease blood pressure (via arterial baroreceptor activity) lead to increase sympathetic nerve activity which causes vasoconstriction and increased cardiac rate and contractitility -> increase CO and bloood volume

Question 4

Hormonal mechanisms in shock response

Answer 4

• vasopressin released
• renin-angiotensin-aldosterone system activated
• ACE in lungs

Question 5

Coronary and cerebral blood flow

Answer 5

• very sparse sympathetic innervation -> very little affected by changes in symapthetic activity
• blood flow to coronary and cerebral beds are controlled largely by local metabolic factors

Question 6

Autoregulation of blood flow to heart or brain

Answer 6

• decrease in MAP -> decrease in coronary blood flow -> imbalance between metabolic demand and supply of nutrients -> decrease in local O2 concentration and increase in Co2 concentration in extracellular fluid -> vasodilation of coronary arterioles -> coronary blood flow back to normal

Question 7

Longer term responses to hemorrhage

Answer 7

• loss of plasma proteins compensated for by increased hepatic synthesis by the liver
• also increased production of RBC, initiated by erythropoietin
• increased level of 2,3-DPG -> causes hemoglobin to release more oxygen and partially compensate for reduced hematocrit

Question 8

Other consequences of severe blood loss

Answer 8

• acidosis
• increased likelihood of blood clots
• increase blood viscosity
• structureal damage to endothelial cells: exacerbates the shock
• Hypoxia leads to a breakdown in barrier and entry of bacteria
• generalised cell damage
• vasomotor and respiratory centres in the brain are depressed

Question 9

Treatment of hemorraghic shock

Answer 9

• blood transfusion
• plasma as an alternative
• colloid (dextran) -> but associated with renal dysfunction
• saline or crystalloid solution
• dont inject vasoconstriction druc