Blood Gas Analysis

Question 1

When would NaHCO3 improve outcomes?

Answer 1

pH

Question 2

Why is acid-base balance important?

Answer 2

Optimizes enzyme function, myocardial contractility and saturation of hemoglobin with oxygen

Question 3

What causes shift to left of oxygen-hemoglobin dissociation curve?

Answer 3

increased pH, decreased temp and DPG (reduced availability of oxygen to tissues, less dissociation from hemoglobin)

Question 4

Regulation of carbonic acid/HCO3 buffer lungs and kidneys

Answer 4

CO2 + H2O H2CO3 H + HCO3 – more bicarb will go left to breathe out more CO2, more CO2 body increases HCO3 excretion to bring equation right

Question 5

Henderson-Hasselbach equation*

Answer 5

pH = 6.1 + log HCO3/0.0301 x pCO2

Question 6

Normal blood gas values on room air (arterial and venous)

Answer 6

Arterial: pH 7.35-7.45, PCO2 35-45, HCO3 22-28, PO2 80-100. Venous: pH 7.3-7.4, PCO2 42-48, HCO3 24-30, PO2 35-45

Question 7

Acidemia vs acidosis

Answer 7

Acidemia the blood is acidotic, acidosis is the process behind what is making the blood acidotic

Question 8

Acute Respiratory Acidosis causes

Answer 8

Increase in CO2 from hypoventilation, increased CO2 production (temp, MH, sepsis), rebreathing, lap insufflation

Question 9

Chronic respiratory acidosis causes ___ PCO2 with ___ pH

Answer 9

elevated, near normal

Question 10

Respiratory alkalosis causes

Answer 10

Over-ventilation, anxiety, pain, CNS disease, increased ICP, cushings triad

Question 11

Anion gap defined and normal

Answer 11

Difference between major measured cations (Na+) and anions (Cl- + HCO3-), normal 7-14

Question 12

High anion gap causes

Answer 12

metabolic acidosis from decreased bicarb, usually lactic acidosis or ketoacidosis – lactate dissociates - picks up hydrogen ion and becomes lactic acid - gets buffered with bicarb so bicarb

Question 13

Lactic acidosis causes

Answer 13

tissue hypoperfusion, hypoxemia, hepatic failure,

Question 14

Ketoacidosis causes

Answer 14

diabetes, starvation, salicylate poisoning

Question 15

Treatment of lactic acidosis

Answer 15

Increase oxygenation, keep PaCO2 in 30s, fluid resuscitation*, circulatory support (inotropes– epi)

Question 16

Bicarb for lactic acidosis

Answer 16

Only if pH

Question 17

Hyperchloremic (normal anion gap) acidosis

Answer 17

GI loss of bicarb (diarrhea), renal wasting (renal tubular acidosis), dilutional hyperchloremic acidosis (rapid expansion with 0.9% NS)

Question 18

How much does 50 mL HCO3- raise serum pH

Answer 18

0.1

Question 19

Base excess defined and normal

Answer 19

Non respiratory contribution to acid-base balance.. amount of strong acid or base that has to be added to a sample of blood to produce pH of 7.4, -2 to 2

Question 20

Metabolic alkalosis causes

Answer 20

gain of HCO3- or loss of H+ (vomiting, diuretics, alkali administration such as citrate in blood products or TPN, hypovolemia decreasing chloride - increases bicarb with sodium)

Question 21

Respiratory acidosis/alkalsosis compensation

Answer 21

For every 10 change in pCO2, pH decreases/increases by 0.08 in acute, by 0.03 in chronic resp acidosis/alkalosis

Question 22

MUDPILES and increased anion gap acidosis

Answer 22

Methanol, uremia, diabetic ketoacidosis, propylene glycol, iron tablets, lactic acidosis, ethylene glycol, salicylates

Question 23

HARDASS and normal anion gap acidosis

Answer 23

Hyperalimentation, addisons, renal tubular acidosis, diarrhea, acetazolamide, spironolactone, saline infusion

Question 24

Winters formula

Answer 24

PCO2 = 1.5 x (HCO3) + 8 +/- 2, tells us if compensation is adequate