Shock, Hypoxia

Question 1

What are the steps involved in hypoxic cell death?

Answer 1

1) Critical loss of ATP
2) Failure of ion gradients to maintain cell polarity
3) Depolarization of cell
4) Calcium influx
5) Calcium dependent phospholipases and proteases activated
6) swelling, hydrolysis, necrosis

Question 2

How is oxygen delivery calculated?

Answer 2

cardiac output x arterial oxygen content (CaO2)

Question 3

What is the normal resting oxygen uptake rate?

Answer 3

3.5 mL/kg/min

Question 4

In what cases might oxygen uptake be dependent upon delivery?

Answer 4

When the delivery has dropped to less than twice the value of VO2

Question 5

What are the four causes of tissue hypoxia?

Answer 5

1) Anemic hypoxia (reduction in hemoglobin)
2) hypoxic hypoxia (reduction in available O2 to blood–extreme altitude, pneumonia)
3) histotoxic hypoxia (chemical disruption of electron transport chain)
4) Stagnant hypoxia (inadequate or maldistributed blood flow)

Question 6

What is the extracted oxygen ratio and how is it calculated?

Answer 6

The percentage of delivered arterial oxygen used for consumption in the tissues. Calcuated by (SaO2-SvO2)/SaO2

Question 7

What is a normal venous oxygen saturation?

Answer 7

75%

Question 8

What are the effects on SvO2 and ERO2 as oxygen delivery decreases?

Answer 8

oxygen extraction will increase; mixed venous saturation will decrease

Question 9

How is shock defined?

Answer 9

systemic derangement in blood flow such that oxygen delivery to tissues is inadequate to meet their needs

Question 10

What are common symptoms of shock?

Answer 10

altered mental status, low urine output, tachypnea, respiratory failure, tachycardia, hypotension, hepatic failure

Question 11

Why might blood pressure be a poor diagnostic criterion?

Answer 11

Young and healthy people will have strong baroreceptor responses to shock and increase sympathetic activity until cardiovascular failure

Question 12

How would work of breathing change in a shock environment?

Answer 12

Since blood is not being delivered appropriately, the work of breathing begins to increase and can rise to up to 50% of oxygen demand.

Question 13

What are the types and causes of shock?

Answer 13

1) Hypovolemic–loss of blood volume due to hemorrhage or dehydration
2) Cardiogenic–problem in heart due to loss of contractility, tamponade, pulmonary artery obstruction, or valvular disease
3) Distributive–bad distribution of blood flow
sepsis, anaphylaxis, hepatic failure

Question 14

What questions guide a clinical diagnosis of shock?

Answer 14

1) Is cardiac output decreased?
2) is the heart full?
3) Do other clinical indicators fit the diagnosis?