Acid-Base Disorders

Question 1

Metabolic acidosis- Laboratory Findings

Answer 1

ctCO2 decreased
pCO2 normal
pH decreased

Question 2

Compensated Metabolic acidosis- Laboratory findings

Answer 2

Primarily respiratory methods (hyperventilation) to lower the pCO2
ctCO2 decreased
pCO2 decreased
pH normal

Question 3

Metabolic alkalosis- laboratory findings

Answer 3

Primary HCO3 excess seen in NaHCO3 infusion, citrate through blood transfusions, antacids, vomiting, K+ depletion, Diuretic therapy, Cushing’s syndrome
ctCO2 increased
pCO2 normal
pH increased

Question 4

Compensated Metabolic alkalosis- laboratory findings

Answer 4

Primarily respiratory (hypoventilation) increasing CO2 retention
ctCO2 increased
pCO2 increased
pH normal

Question 5

Respiratory acidosis- laboratory findings

Answer 5

Primary CO2 acidosis from emphysema, pneumonia, rebreathing air
ctCO2 normal
pCO2 increased
pH decreased

Question 6

Compensated respiratory acidosis- laboratory findings

Answer 6

Mainly renal by increasing H+ excretion and HCO3 reabsorption
ctCO2 increased
pCO2 increased
pH normal

Question 7

Respiratory alkalosis- laboratory findings

Answer 7

Primary CO2 deficit seen in hyperventilation and early salicylate poisoning
ctCO2 normal
pCO2 decreased
pH increased

Question 7

Metabolic acid-base disorders involve ?

Answer 7

Bicarbonate concentration

Question 8

Compensated respiratory alkalosis- laboratory findings

Answer 8

Mainly renal by decreasing H+ excretion
ctCO2 decreased
pCO2 decreased
pH normal

Question 9

Respiratory acid-base disorders involve ?

Answer 9

Carbon Dioxide concentration

Question 10

Increased pCO2 causes what?

Answer 10

And increase in dissolved Carbon Dioxide which forms Carbonic Acid in blood, decreasing pH

Question 11

Henderson-Hasselbalch Equation

Answer 11

Ionization constant of a weak acid
pH = pKa + log [HCO3]/[H2CO3]
Normally should be around 20/1 ratio
pH is proportional to log [HCO3]/[pCO2] ie kidney/lungs or metabolic/respiratory

Question 12

Specimen Collection

Answer 12

Anticoagulant needs to be heparin, using anaerobic collection for blood gas/pH studies
If the blood is exposed to air, CO2 and pCO2 will go down, pH and pO2 will go up
If tested after 15 min, it needs to be iced to prevent glycolysis which will cause CO2 and pCO2 will go up, pH and pO2 will go down

Question 13

Evaluating Acid-Base Disorders

Answer 13

Compare CO2 and HCO3, if pCO2 is going opposite pH think respiratory, if it’s going with pH think metabolic

Question 14

Primary Respiratory Disfunction

Answer 14

Change in pCO2 compensated by metabolic HCO3

Question 15

Primary Metabolic Disfunction

Answer 15

Change in HCO3 compensated by respiratory pCO2

Question 16

Main Buffer Systems

Answer 16

Bicarbonate-Carbonic Acid: minimize pH change in plasma and erythrocytes
Protein Buffer System: plasma proteins minimize pH change in blood
Phosphate Buffer System: minimize pH change in plasma and erythrocytes
Hemoglobin Buffer System: Hgb minimize pH change in blood, most important intracellular buffer

Question 17

Metabolic Acid-Base Disorders involve

Answer 17

Bicarbonate concentration

Question 18

Respiratory Acid-Base Disorders involve

Answer 18

Dissolved Carbon Dioxide concentration

Question 19

Oxygen Metabolism

Answer 19

Transported in dissolved state, controlled by pO2, oxygen diffusion through alveoli, and hemoglobin affinity for oxygen
Release depends on H+ content of tissues and pCO2 concentration
Normal Hgb saturation is around 95%