Cell Injury

Front 1

Causes of Hypoxemia

Back 1

What is hypoxemia?--> decrease in plasma O2 levels

1. respiratory acidosis
2. ventilation defects
3. perfusion defects
4. diffusion defects

Front 2

Respiratory Acidosis

Back 2

Causes a retention of CO2 in the lungs, which drives down PaO2 causing hypoxemia

examples of this: respiratory depression (from barbiturates), paralysis of the diaphragm, chronic bronchitis

Front 3

Ventilation Defect

Back 3

Impaired O2 delivery to the alveoli
example: RDS

so there is perfusion, but no ventilation.. this means we've got low PaO2

administration of 100% oxygen does NOT increase PaO2

Front 4

Perfusion Defect

Back 4

Absent blood flow to the lungs

example is a pulmonary embolus

produces an increase in dead space, but administration of 100% oxygen will increase the Pa02

Front 5

Diffusion Defect

Back 5

Examples: pulmonary fibrosis, pulmonary edema

Decreases diffusion through the alveolar- capillary interface

Front 6

What type of iron will bind O2?

Back 6

Fe2+ will bind O2 (ferrous)

Fe3+ will NOT bind O2 (ferric)

Front 7

What Oxygen Saturation produces cyanosis?

Back 7

Less than 80%

Front 8

Causes of Anemia

Back 8

1. lack of Hb production (iron deficiency)
2. Increased destruction of RBCs (HS)
3. Decreased production of RBCs (aplastic anemia)
4. Increased sequestration of RBCS (splenomegaly)

you will have decreased O2 content, but NORMAL O2 sat and NORMAL PaO2

Front 9

What is Methemoglobinemia?

Back 9

Iron is Oxidized to Fe3+

causes: oxidizing agents (Nitrite and Sulfur containing drugs)
or a deficiency of metHb reductase (reductase normally converts Fe3+ to ferrous Fe2+)

Front 10

What does Methemoglobinemia look like?

Back 10

Patients have chocolate colored blood and cyanosis; skin color WILL NOT return back to normal after 100% oxygen, because the O2 can't bind to the Hb.

See decreased Oxygen Saturation, and normal Pa02

Treatment for Methemoglobinemia is Methylene Blue to activate metHb reductase and Vitamin C to reduce Fe3+ to Fe2+

Front 11

Carbon Monoxide Poisoning

Back 11

Causes a Left SHIFT

Has much higher affinity for Hb (250X) than Oxygen does. So CO competes with O2 for binding sites on the Hb, so it decreases the Sa02 without affecting the Pa02

CO also inhibits cytochrome oxidase in the electron transport chain, and causes a left shift in the O2 binding curve

Front 12

Tell me more about CO poisoning?

Back 12

Caused by the incomplete combustion of Carbon containing compounds

Clinically there is a cherry red discoloration of the skin and blood, but the cyanosis will often time mask this. Headache is the first symptom, coma and necrosis of the globus pallidus

Treat CO poisoning with 100% Oxygen

Front 13

What factors will cause a left shift in the O2 binding curve?

Back 13

So you are NOT dropping the oxygen off at the tissues

Decreased 2,3 BPG
an intermediate of glycolysis via conversion of 1,3 BPG to 2,3 BPG

CO, Alkalosis, metHb, fetalHb, hypothermia

Front 14

What happens at high altitudes?

Back 14

Same O2 content, but it's lower pressure, therefore we have a decreased Pa02. This hypoxemia stimulates the carotid body peripheral chemoreceptors which causes a respiratory alkalosis (hyperventilation) which causes LEFT shift, but the alkalosis also activation of PFK in glycolysis increases 2,3, BPG causing a RIGHT shift to deliver oxygen to the tissues

Front 15

Cytochrome Oxidase

Back 15

CO and CN inhibit cytochrome oxidase, preventing the synthesis f ATP

CN poisoning may come from house fires (polyurethane products like chairs) or from drugs (nitroprusside)

CN poisoning is treated with amyl nitrites (which produces a metHb which will combine with CN) followed by a thiosulfate (CN converted to thiocyanate)

Front 16

Hyperthermia as a possible complication?

Back 16

Alcohol, Salicylates, and Dinitrophenol (an uncoupling agent)

EtOH and ASA damage the inner mitochondrial membrane, causing protons to move into the mitochondrial matrix