inpatient / nephrology

Metabolic Acidosis

Last Updated: 1/6/2023

# Metabolic Acidoiss

-- ABCs: 
pH <7.2 --> ICU for bicarb, possible intubation if resp distress
-- VBG: confirm pH <7.36 and bicarb <24 (did PCO2 go down by 1 for each decrease in bicarb?)
-- HPI Intake: meds and adherence, alcohol use, other ingestions, immunosuppression, infectious symptoms
-- Can't Miss: sepsis/shock, DKA
-- Admission Orders: lactate, BHB, UA
-- Initial Treatment to Consider: *** bicarb, fluids, antibiotics,

-- History: *** alcohol use, CKD, diabetes, infections, ingestions
-- Clinical: *** confusion, dyspnea, vision changes, localizing infectious symptoms, N/V/D
-- Exam: *** AMS, WOB, overload
-- Data: *** VBG (pH, PCO2), bicarb, potassium,
-- Etiology/DDx: *** Anion Gap: lactic acidosis, uremia, DKA, intoxication; Non-Anion Gap: renal failure, diarrhea, saline infusion, RTA

The patient's HPI is notable for ***. Exam showed ***. Labwork and data were notable for ***. Taken together, the patient's presentation is most concerning for ***, with a differential including ***.

-- f/u CBC, BMP, VBG, UA
-- if anion gap - lactate, BHB

-- IVF: ***
-- Treat underlying cause - DKA, sepsis, renal failure, etc.
-- If c/f intoxication, consult renal for dialysis and fomepizole

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If You Remember Nothing Else

While acid-base distrubances can be confusing to think through, most patients who have metabolic acidosis in the hospital have lactic acidosis, renal failure, or ketoacidodis (DKA, EtOH, starvation). However, you can't miss ingestions or a respiratory acidosis from overdose or central process. Treatment involves addressing the underyling process and intubation or dialysis when appropriate.

Clinical Pearls

  • Severe acidemia (pH <7.2) can lead to vasodilation, decreased inotropy, decreased response to pressors, arrhythmias, hyperkalemia, altered mental status
  • Forget MUDPILES and GOLDMARKS - for common inpatient etiologies of metabolic acidosis, just remember LUDI - lactic acidosis, uremia, DKA, intoxication
  • If you are spilling glucose on UA with no other good reason in metabolic acidosis, may suggest proximal tubules may not be working, bicarb may not be getting absorbed - may suggest RTA
  • The anion gap is calculated by unmeasured anions - unmeasured cations → will be high if lots of unmeasured anions like albumin or other proteins like in MM or IVIG treatment
  • Ona VBG the pH will be ~0.04 lower and CO2 ~8 lower than on ABG

Other Resources

  • Image for Interpreting Acid-Base Disturbace based on PCO2 and pH - link