ACID BASE

Question 1

DDx AGMA

Answer 1

Methanol
Uremia
Diabetes (ketones)
Paraaldehyde
Isoniazid, Iron
Lactic Acid
Ethylene Glycol
Salicylates

Question 2

MANAGEMENT

Answer 2

STEPWISE APPROACH
1. Assess the pH
pH < 7.35: acidemia
pH > 7.45: alkalemia

2. Assess PC02
   PC02 > 45: hypercarbic acidosis
   PC02 < 35: hypocarbic acidosis
3. Assess Bicarb
4. Calculate SID (Na-Cl)
   SID < 36: hyperchloremic acidosis
   SID > 40: hypochloremic acidosis
5. Calculate Anion Gap
   (Na-[Cl + HC03])
   GAP > 15: Gap Acidosis
6. Calculate Delta Delta
   Delta Anion Gap = Anion Gap - 10 = elevated anion gap

Delta BiCarb = 24 - Bicarb

DELTA RATIOS
Delta HC03 < Delta AG ~ AGMA + NAGMA

Delta HC03 = Delta AG ~ Uncomplicated AGMA

Delta HC03 > Delta AG ~ AGMA + Metabolic Alkalosis

INVESTIGATIONS

Na+, K+, Cl−, blood urea nitrogen (BUN), creatinine, and albumin.
VBG
Serum lactate.
Ketones, either urine or serum.
Salicylate level.
Pregnancy test.
Echo, focused assessment with sonography in trauma, and/or computed tomography if and when clinically indicated to help further elucidate the underlying cause.

Question 3

JOURNALS

Answer 3

Jaber et al.: infusion of 4.2% sodium bicarbonate to ICU patients presenting with metabolic acidosis and a pH <7.20 did not improve mortality.

Fujii T, Udy A, Licari E, Romero L, Bellomo R. Sodium bicarbonate therapy for critically ill patients with metabolic acidosis: A scoping and a systematic review. J Crit Care. 2019;51:184-191. doi:10.1016/j.jcrc.2019.02.027: No trial has been identified that shows mortality benefit when sodium bicarbonate has been used in bolus or infusion to correct a patient’s serum pH