Lecture 3: High Anion Gap Metabolic Acidosis

Question 1

How do you calculate anion gap?

What is normal?

Answer 1

• AG = Na⁺ - (Cl^- + HCO₃^-)
• Normal = 10 ± 2

Question 2

Which value indicates metabolic acidosis?

Answer 2

HCO₃^- <20

Question 3

Which value indicates metabolic alkalosis?

Answer 3

HCO₃ > 30

Question 4

Which value indicates respiratory acidosis?

Answer 4

pCO₂ >45

Question 5

Which value indicates respiratory alkalosis?

Answer 5

pCO₂ < 35

Question 6

Elevation in anion gap value suggests what?

Answer 6

Metabolic acidosis w/ circulating anions

Question 7

How do you calculate the appropriate compensation for Metabolic Acidosis?

How do you know if you have appropriate compensation?

Answer 7

• PCO₂ = (1.5 x [HCO₃^-]) + 8 (±2)
• Approrpiate compensation –> calculated PCO₂ = measured PCO₂

Question 8

After applying the compensation equation for metabolic acidosis, if the calculated PCO₂ doesn’t match measured PCO₂, is either higher or lower you have what?

Answer 8

• Serum PCO₂ > expected PCO₂ = additional respiratory acidosis
• Serum PCO₂ < expected PCO₂ = additional respiratory alkalosis

Question 9

Ingestion of which 4 acids are major causes of acidosis?

Answer 9

1. Ethylene glycol
2. Methanol
3. Propylene glycol
4. Salicylates

Question 10

Major signs and symptoms of acidosis?

Answer 10

• Tachypnea
• Tachycardia
• Pulmonary edema
• Increased serum glucose

Question 11

Using MUD PILES what are the most common causes of high anion gap metabolic acidosis?

Answer 11

• Methanol, metformin
• Uremia —> renal failure
• DKA –> generally T1DM
• Paraldehyde, propylene glycol, phenformin
• Isoniazid/iron toxicity
• Lactic acidosis
• Ethanol/ethylene glycol
• Salicylates

Question 12

Lactic acidosis is a cause HAGMA, what 4 underlying factors can cause lactic acidosis?

Answer 12

• Cyanide and carbon monoxide poisoning
• Seizures
• Sepsis
• Ischemia/Hypovolemic shock

Question 13

What does the CAT stand for if using CAT MUDPILES for most common causes of HAGMA?

Answer 13

• C = carbon monoxide and cyanide
• A = alcoholic ketoacidosis (starvation ketoacidosis)
• T - toluene (can cause HAGMA and NAGMA)

Question 14

Major causes of Rhabdomyolysis?

Answer 14

• Muscle fiber exhaustion –> seizure, extreme exercise, heat stroke, malignant hyperthermia
• Physical injury –> trauma, crush injury, immonbilization, compartment syndrome

Question 15

List 6 drugs which may cause rhabdomyolysis?

Answer 15

• Statins
• SSRIs
• Cocaine
• Amphetamines
• Heroin
• Creatine

Question 16

List 6 toxins which may cause rhabdomyolysis?

Answer 16

• Alcohol
• Toluene
• Carbon monoxide
• Hydrocarbons
• Quail poisoning
• Mushroom poisoning

Question 17

Hypokalemia, hypophosphatemia, excessive fluid shifts, vasculitis, influenza, dermatomyositis, and polymyositis may cause what condition that is associated w/ HAGMA?

Answer 17

Rhabdomyolysis

Question 18

What are the typical presenting sx’s of someone with DKA?

Answer 18

• Polyuria and polydipsia
• Abdominal pain, N/V

Question 19

Ethylene glycol will have what finding in the urine and under woods lamp?

Answer 19

• Calcium oxalate crystals in the urine
• Fluoresce under woods lamp

Question 20

Characteristic sx of Methanol ingestion?

Answer 20

Blurry vision

Question 21

How does Salicylate toxicity present?

Answer 21

• Tachypnea as salicylate is direct respiratory stimulant
• Tinnitus is present when levels are high
• CNS manifestations –> agitation, seizures, coma

Question 22

In salicylate toxicity the metabolic acidosis is a result of what accumulation?

Answer 22

Accumulation of both lactic acid and ketoacids

Question 23

Ethylene glycol ingestion will present with intoxication and HAGMA and what lab findings?

Answer 23

• HAGMA without ketones
• Low blood alcohol level

Question 24

Ethylene glycol ingestion causes HAGMA by increasing levels of what?

Answer 24

Increased NADH levels –> encourages lactic acid formation

Question 25

Methanol is metabolized to what, which leads to a HAGMA?

Answer 25

Methanol –> formaldehyde –> formic acid