Metabolic acidosis resident survival guide

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ogheneochuko Ajari, MB.BS, MS [2]

Definition

Metabolic acidosis is a state in which the blood pH is low (less than 7.35) due to increased production of H⁺ by the body or the inability of the body to form bicarbonate (HCO₃^-) in the kidney.

Causes

Life Threatening Causes

• Diabetic ketoacidosis
• Ethylene glycol poisoning
• Lactic acidosis
• Methanol

Common Causes

Low Anion Gap Metabolic Acidosis

• Hypoalbuminemia
• Multiple myeloma

Normal Anion Gap Metabolic Acidosis

The mnemonic for the most common causes of a normal-anion gap metabolic acidosis is "DURHAM."

• D- Diarrhea
• U- Ureteral diversion
• R- Renal tubular acidosis
• H- Hyperalimentation
• A- Addison's disease, acetazolamide, ammonium chloride
• M- Miscellaneous: congenital chloride diarrhea, amphotericin B, toluene (toluene causes high anion gap metabolic acidosis followed by normal anion gap metabolic acidosis)

High Anion Gap Metabolic Acidosis

The mnemonic "MUDPILES" is used to remember the common causes of a high anion gap.

• M - Methanol/ Metformin
  
• U - Uremia
  
• D - Diabetic ketoacidosis
  
• P - Paraldehyde/ Propylene glycol
  
• I - Infection/ Ischemia/ Isoniazid
  
• L - Lactic acidosis
  
• E - Ethylene glycol/ Ethanol
  
• S - Salicylates/ Starvation

Management

Shown below is the algorithm summarizing the management of metabolic acidosis

History, symptoms and physical examination Blood pH < 7.35

Physical Examination Eyes, extremities Neurologic (cranial nerves)

Labs/EKG Anion gap, Arterial blood gas analysis Electrolytes (Na, K, Cl, HCO3) CBC Serum lactate, ketone Urinalysis Toxicological screening (salicylate, methanol, ethylene glycol) EKG for arrhythmias

History Arrhythmias Kussmaul breathing Headache, altered mental status

Place patient on EKG monitor for arrhythmias, hyperkalemia

Replace electrolytes if there are losses

If DKA, IV Insulin, normal saline Potassium and Phosphate may be necessary

Send consult to Nephrologist for dialysis for renal failure, poisoning

Toxicological consult

IV Bicarbonate if there is cardiac arrhythmias 50-100mmol while monitoring arterial blood gas readings

Detoxification agents/Toxin antidotes Fomepizole Activated charcoal Emesis Folic acid for methanol overdose Thiamine and pyridoxine for ethylene glycol overdose

Do's

• Treatment of the underlying cause should be the primary therapeutic goal.
• Bicarbonate should be given only when there is a severe case of acidosis with an arterial pH of less than or equal to 7.0
• Patient should be placed on SaO2 and blood pressure/heart rate monitor
• Consider intubation and ventilation for airway if the SaO2 level is deteriorating or there is a loss of consciousness
• Consider doing catherization to monitor the urine output and obtaining urine for urinalysis

Dont's

• Do not give vasoconstrictors in the presence of lactic acidosis