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Acid Base Disorders Algorithm

Acid and Base Disorders Algorithm Step-by-Step Instruction Guide

Clinton Pong

on 3 February 2013

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Transcript of Acid Base Disorders Algorithm

Acid Base Disorders Evaluate Patient &
Generate Hypotheses Acidemia <7.4 >7.4 Alkalemia Check pH Henderson-Hasselbach Eq: pH = pK + log([HCO3]/[0.03 x pCO2])
Modified H-H eq: [H+] = 24 x (pCO2/[HCO3]) --> 40nEq/L Check PaCO2
and HCO3 High PaCO2 Low HCO3 Respiratory
Acidosis Metabolic
Acidosis Step 1: Evaluate the Patient and Generate Hypotheses

Step 2: Check pH and determine if Primary Process is Acidemia/Alkalemia

Step 3: Check PaCO2 and HCO3 to determine if Respiratory or Metabolic

Step 4: Check for Compensation

Step 5: Check Anion Gap

Step 6: Reach final diagnosis Low PaCO2 High HCO3 Respiratory alkalosis Metabolic
Alkalosis Respiratory Acidosis Any process that participates in normal ventilation
(brain - brainstem - spinal cord - nerve - NMJ - muscle - chest wall - lung Metabolic Acidosis
Anion gap or Non-Anion Gap? Respiratory Alkalosis Hyperventilation, blowing off the CO2 Metabolic Alkalosis Increased mineralocorticoid activity
Primary hyperaldosteronism
Renal Artery Stenosis
JGA Tumor
Cushing's Hypercortisolism
Excessive licorice ingestion
Recent Diuretic use Mnemonics GOLDMARK
Glycols (Ethylene & Propylene)
L-lactic acid
D-lactic acid
Renal Failure
Ketoacidosis (DM, EtOH) KILU
Lactic acid
Propylene glycol
Lactic acid
Ethylene glycol
Salicylates The metabolic acidoses are generally separated into two categories on the basis of an anion gap calculation (Na+[Cl−HCO3−]): the high-anion-gap metabolic acidoses, and the normal-anion-gap, or hyperchloraemic, metabolic acidoses. Two popular mnemonics are often used to remember the major causes of the high-gap metabolic acidoses.
The first is KUSMALE (a useful misspelling of Adolph Kussmaul's name), which represents Ketoacidosis, Uraemia, Salicylate poisoning, Methanol, Aldehyde (paraldehyde), Lactate, and Ethylene glycol.
The second is MUD PILES, representing Methanol, Uraemia, Diabetes, Paraldehyde, Iron (and Isoniazid), Lactate, Ethylene glycol, and Salicylate.
Metabolic acidosis due to excessive paraldehyde use has become exceedingly rare. Iron and isoniazid are just two of many drugs and toxins that cause hypotension and lactic acidosis (isoniazid can also generate a component of ketoacidosis). Three “new” organic anion-gap-generating acids and acid precursors have been recognised in recent years. They are D-lactic acid, which can occur in some patients with short bowel syndromes; 5-oxoproline (or pyroglutamic acid) associated with chronic paracetamol use, often by malnourished women; and the anion-gap acidosis generated by high-dose propylene glycol infusions. Propylene glycol, the solvent used for several parenteral medications including lorazepam, phenobarbital, and others is metabolised to D-lactate and L-lactate.

Therefore we propose a new anion gap mnemonic for the 21st century: GOLD MARK. This acronym represents Glycols (ethylene and propylene), Oxoproline, L-lactate, D-lactate, Methanol, Aspirin, Renal failure, and Ketoacidosis. Mnemonic aids are only helpful if they are easily remembered and we believe GOLD MARK fits that requirement.

Mehta A.N., Emmett J.B., Emmett M. (2008). "GOLD MARK: an anion gap mnemonic for the 21st century." The Lancet, Volume 372, Issue 9642, Page 892, 13 September 2008 NAG AG Occurs when an acid is produced and the unmeasured negatively charged Anion accumulates (ketones, lactate, sulfate, phosphate, organic anions) Metabolic acidosis
HCO3 drop 1 = PaCO2 drop 1.2
[Winter's Formula]
[1.5(HCO3)+8 +/-2 = PaCO2] Metabolic alkalosis
HCO3 up 1 = PaCO2 up 0.7
pCO2 ~ HCO3 +15
0.9(HCO3)+16 or ΔpCO2 = 0.75(ΔHCO3) Respiratory Acidosis
PaCO2 up by 10 per Acute Chronic HCO3 up by 1 HCO3 up by 3.5 Respiratory Alkalosis
PaCO2 down by 10 per Acute Chronic HCO3 down by 2 HCO3 down by 4 Na - Cl - HCO3 = AG. Normal AG = 12 +/- 4
Expected drop in Anion gap is 2.5 mEq/L for every 1 g/dL drop in the serum albumin (below 4.4 g/dL)
Occurs when HCO3 is lost in the urine or stool Anion gap is due to the presence of normal negatively charged proteins (albumin), phosphates, and sulfates
Normal is typically 12 +/- 4 Ketoacidosis
Diabetic ketoacidosis
Starvation ketoacidosis
Alcoholic ketoacidosis
Ethylene glycol
D-lactic acidosis
Lactic acidosis
Shock, hypoxia, hypotension
Uremia (assoc w/ more phosphate & sulfate) Diarrhea
Renal Tubular Acidosis
Type IV (most common)
Type I
Type II
Carbonic anhydrase inhibitor
Dilutional (large NS volume (hyperchloremia)
Early renal failure Check PaCO2
and HCO3 Brain
Drugs and intoxicants
Sleep apnea Brainstem
Herniation Spinal cord
Polio Nerve
Guillain-Barre NMJ
Myasthenia gravis CW/muscle
Flail chest
Muscular dystrophy Pleural disease
PTX Most commonly:
Pulmonary edema
PNA Hypoxemia
Pulmonary disorders
Pulmonary edema
Interstitial lung disease
Mechanical ventilation via both hypoxic and vagal mechanisms Extra Pulmonary Disorders
CNS insult
Cirrhosis Check for
combined disorders Check for a combined disorder with "Delta-Delta" or "Delta Gap"

1. Δ/Δ: ΔAG/ΔHCO3 = (AG-10)/(24-HCO3)
<1 : AG-met-acid + non-AG-met-acid; or AG-metacid + chronic resp alk
1-2: Pure AG-met-acid
>2: AG-met-acid + metalk; or AG-met-acid + chronic resp acid
2. Δgap: (AG-10)+HCO3+6
normal (24-30): no add'l underlying d/o
<24: concomitant non-AG-met-acid
>30: concomitant-metalk Are there any hidden organic anions? Check the OSMOLE GAP
Sosm - Calc osm
[calc osm = 2Na+BUN/2.8+Glu/18] elevated OsmGap >10
EtOH, MeOH, Glycols OsmGap <10
Normal Check urine AG: Na+K-Cl I: hypercalciruria, stone, hyperglobulin, AI, nephrocalcinosis

II: fanconi, dysproteinemia, heavy metal Positive:
HCO3 loss by urine
Renal Tubular Acidosis Negative:
(HCO3 loss via GI)
GI losses IV: DM, obstructive, tubulointerstitial dz, SCD, Transplant rejection, cyclosporine I: Uk dec, UpH>5.5
II: Uk dec, UpH<5.5
IV: Uk inc, UpH<5.5 Check urine Cl UCl<20
(Cl responsive) UCl >20 Vomiting
NGT use
Remote diuretic use
tx w/ NS (saline responsive) ABG: pH / pCO2 / pO2 / HCO3 / BE / O2sat (on vent settings or FiO2 "X") Na Cl BUN
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