Acid-Base

Question 1

Resp Acidosis

Acute & Chronic compensation

Answer 1

Acute: PCO2 +10 = HCO3 +1

Chronic: PCO2 +10 = HCO3 +3

Question 2

Resp Alkalosis

Acute & Chronic Compensation

Answer 2

Acute: PCO2 -10 = HCO3 -2

Chronic: PCO2 -10 = HCO3 -5

Question 3

Metabolic Acidosis

Compensation

Answer 3

HCO3 -1 = PCO2 -1

Question 4

Metabolic Alkalosis

Compensation

Answer 4

HCO3 +1 = PCO2 +0.5-0.7

Question 5

Anion Gap

Answer 5

[Na] - [Cl] - [HCO₃]

Normal: 4-12

Decrease normal limit for AG by 3 for every 10 point drop in Albumin

Question 6

Delta delta

Answer 6

Is the fall in HCO₃ equivalent to the rise in the AG? If HCO₃ has dropped more, then superimposed NAG acidosis. If dropped less, then superimposed metabolic alkalosis.

Question 7

Osmolar Gap

Answer 7

OG = Measured Osm - (2X[Na] + [BUN] + [Glu])

Normal is <10

Question 8

Causes of AG acidosis

Answer 8

• *M**ethanol
• *U**remia
• *D**KA, AKA, starvation ketoacidosis
• *P**araldehyde
• *I**NH
• *L**actic Acidosis
• *E**thylene glycol
• *S**alicylates

Question 9

Causes of Osmolar Gap

Answer 9

• *D**-lactic acidosis
• *M**ethanol
• *E**thylene Glycol
• *A**lcohol
• *T**oluene

Question 10

Urine anion gap

Answer 10

If non-anion gap acidosis, check urine anion gap (Na+K)-Cl

Should be normal (negative value). If normal/negative then GI losses. If positive then renal tubular acidosis.

Question 11

Causes of low AG

Answer 11

• increase in unmeasured cations
  
  • lithium
  • myeloma, gammopathy
  • hypertriglyceridemia
  • decrease in albumin

Question 12

Alveolar-arterial Gradient

Answer 12

• P(A-a)O2 = 147 - (PaCO2 x 1.25) - PaCO2
• Normal in young adults is < 15 mmHg; older, estimate Age/4 + 4

Question 13

PaO2/FiO2 ratio

Answer 13

• PaO2 (mm Hg)/ FiO2 (as a decimal)
• 600 normal
• 300 minimal impairment
• 250 mild
• 200 moderate
• 150 severe
• 100 very severe

Question 14

Differences between ABG & VBG

Answer 14

• pH +- 0.05
• PCO2 +- 20 but if normal, should be normal
• HCO3 best from lytes as blood gas is calculated
• PaO2 does not correlate
• lytes and CBC on ABG not accurate if abnormal
• lactate probably better on ABG but commonly used in peripheral venous