Metabolic and Respiratory Acidosis and Alkalosis - Diagnostic Algorithm Anion gap

Acid Base and Blood Gas Analysis 1. pH - What’s the primary disturbance? 2. pCO2 - What’s the pCO2? 3. HCO3 - What’s the bicarb? Respiratory Acidosis - Airflow obstruction • COPD, asthma, ↓ Drive, Medications, Central, ↑ CO2 production Respiratory alkalosis drive • Hypoxemia • Pain/anxiety • Hepatic enceph • Pregnancy • Salicylates Metabolic Alkalosis - “BLVD PLACE” B - Bartter's L – Laxative V – Vomiting D - Diarrhea/diuretics P - Post-hypercapnea L - Licorice A - Alkali ingestion C - Contraction alkalosis E - Endocrine (Conn’s or Cushing’s) Metabolic Acidosis - non anion gap metabolic acidosis - anion gap metabolic acidosis Nick Mark MD @nickmmark #acidbase #workup #algorithm #diagnosis #acidosis #alkalosis #metabolic #respiratory #bloodgas #interpretation

Causes of High-anion Gap and Non-anion Gap Metabolic Acidosis Causes of High-anion Gap Acidosis: • Lactic acidosis • Ketoacidosis: Diabetic, Alcoholic, Starvation • Toxins: Ethylene glycol, Methanol, Salicylates, Propylene glycol, Pyroglutamic acid (5-oxoproline) • Renal failure (acute and chronic) Causes of Non-anion Gap Acidosis: I. Gastrointestinal bicarbonate loss A. Diarrhea B. External pancreatic or small-bowel drainage C. Ureterosigmoidostomy, jejunal loop, ileal loop D. Drugs II. Renal acidosis A. Hypokalemia 1. Proximal RTA (type 2) 2. Distal (classic) RTA (type I) B. Hyperkalemia 1. Generalized distal nephron dysfunction (type 4 RTA) C. Normokalemia 1. Chronic progressive kidney disease Ill. Drug-induced hyperkalemia (with renal insufficiency) A. Potassium-sparing diuretics (amiloride, triamterene, spironolactone, eplerenone) B. Trimethoprim C. Pentamidine D. ACE-Is and ARBs E. Nonsteroidal anti-inflammatory drugs F. Calcineurin inhibitors IV. Other A. Acid loads (ammonium chloride, hyperalimentation) B. Loss of potential bicarbonate: ketosis with ketone excretion C. Expansion acidosis (rapid saline administration) D. Hippurate E. Cation exchange resins #aniongap #NonGap #Metabolic #Acidosis #differential #diagnosis #causes #nephrology

Types of Anion Gap Acidosis - AGAPS KIL U - Mnemonic Ketoacidosis: Alcoholic Ketoacidosis, Starvation Ketoacidosis, Starvation Ketoacidosis Ingestions: Alcohols (Ethylene Glycol, Ethanol, Methanol), Salicylates, Acetaminophen, Iron, INH Lactic Acidosis: • L-Lactic Acidosis - From Anaerobic metabolism, Tumors, or Medication induced • D-Lactic Acidosis - From Short Gut or IV Lorazepam Uremia: • Failure to secrete Hydrogen and excrete Ammonia • Accumulation of Phosphate and other organic acids Unremarkable Labs @UnremarkableLab #AnionGap #Acidosis #AGAPSKILU #mnemonic #differential #diagnosis #causes

High Anion Gap Metabolic Acidosis (HAGMA) - Differential Diagnosis - GOLDMARK Glycols - ethylene and propylene glycol Oxoproline - associated with acetaminophen use L-lactate - produced during hypoxic metabolism D-lactate - associated with short bowel syndrome Methanol ingestion - anti-freeze, varnish, etc. Aspirin - salicylate toxicity causes lactic & ketoacidosis Renal failure - underexcretion of acids in advanced renal failure Ketoacidosis - diabetic, alcohol, starvation Paresh Jadav, MD @jadav_md #Anion #Gap #Metabolic #Acidosis #HAGMA #Differential #Diagnosis #GOLDMARK #mnemonic #nephrology

Anion Gap Metabolic Acidosis • Diabetic Ketoacidosis ± Hyperglycemia ± Hyperosmolar • Alcoholic Ketoacidosis ± Hyperglycemia • Shock • Bowel or limb ischemia • Ingestion of Salicylate, Methanol, Ethylene glycol • Type B lactic acidosis - Drugs ( Albuterol, Metformin, Linezolid, HART) - Thiamine Deficiency - Malignancy (lymphoma) • Cirrhosis • Uremic Acidosis Landsberg Manual @LandsbergManual - https://amzn.to/3rEtbK8 #AnionGap #Metabolic #Acidosis #differential #diagnosis

Acid Base Disorders - Blood Gas Interpretation Steps for Blood Gas Interpretation: 1. Acidemia or Alkalemia? 2. Respiratory or Metabolic? 3. Compensated? Acute or chronic? 4. Anion gap? Delta-delta? 5. Differentials? ABG And BMP Normal Values • pH: 7.35-7.45 • PaCO2: 35-45 mmHg • PaO2: 80-100 mmHg • HCO3 (on BMP): 22-26 mmol/L Step 1 - Acidemia or Alkalemia: • pH <7.35 = Acidemia • pH >7.45 = Alkalemia Step 2 - Respiratory or Metabolic: pH pCO2 ↓ ↓ Metabolic Acidosis ↑ ↑ Metabolic alkalosis ↓ ↑ Resp Acidosis ↑ ↓ Resp Alkalosis Step 3 - Compensation, Acute vs Chronic: • Metabolic compensation • Respiratory compensation Step 4 - Anion gap, Delta-delta: Anion Gap (AG) = {Na - (Cl + HCO3)} Normal = 12 +/- 2 Corrected Anion Gap = AG + 2.5(4-albumin) Delta: Delta = (AG-12) / (24-HCO3) Delta: Delta Interpretation For Metabolic Acidosis <0.4 Pure Normal AG metabolic acidosis 0.4-0.8 Normal + High AG metabolic acidosis 0.8-2.0 Pure High AG metabolic acidosis >2.0 Metabolic acidosis with superimposed Metabolic alkalosis/Resp acidosis Step 5 - Differential Diagnosis: Causes of High Anion Gap Metabolic acidosis: G Glycols - ethylene glycol “antifreeze” and propylene glycol (present in IV benzodiazepines) O Oxoprolin (associated with acetaminophen dosing) L L-lactate (common form of lactate) D D-lactate (short bowel syndrome, intestinal bacterial overgrowth, propylene glycol) M Methanol A Aspirin (salicylates) R Renal failure (uremia) K Ketoacidosis (starvation, diabetic) Causes of Normal Anion Gap Metabolic acidosis: - Diarrhea - Renal tubular acidosis/Chronic renal failure - Adrenal insufficiency - Rapid saline infusion - Acetazolamide Causes of Metabolic Alkalosis: - Vomiting, NG suction - Volume depletion (diuresis) - Mineralocorticoid excess Causes of Respiratory alkalosis: - Hyperventilation (Anxiety, pain, fever, hypoxia) - “Classically” noted with pulmonary embolism (with associated hypoxia) - Salicylates Causes of Respiratory acidosis: - CNS depression (sedation, narcotics, CVA) - Neuromuscular weakness (GBS, Myasthenia gravis) - Obstructive or restrictive lung disease (COPD, OSA, Asthma, Obesity hypoventilation) - Airway obstruction (foreign body, aspiration) M. Daniyal Hashmi, MD @MDaniyalHashmi1 #AcidBase #disorders #Interpretation #Diagnosis #Summary #Nephrology #ABG #bloodgas #Acid #Base #Gas #VBG #differential

Acid-Base (Made Easy) - Algorithm for determining the primary acid / base disorder #Diagnosis #Metabolic #Respiratory #Acidosis #Alkalosis #Algorithm

Metabolic Acidosis with Anion Gap - KILU Mnemonic K - Ketoacidosis • DKA - With normal glucose, ask if on SGLT2 inhibitor. - Eugylcyemic ketoacidosis in SGLT2 inhibitors and SGLT2 deficiency mutation • Alcohol ketoacidosis - 10% have -ve urine ketones (their ketone is B-hydroxy butyrate) • Starvation I - Ingestions • ethylene glycol, methanol (for those, check osm gap, & alcohol level) • salicylates (+ resp alkalosis}, APAP (rare in lit), iron (pediatric), paraldehyde L - Lactate • Type A = tissue hypoxia (e.g. shock, dying gut/limb). • Type B = lymphoma or leukemia or drug that results in lactate build-up, Beri-Beri, NRTl's, linezolid U - Uremia • The anion is phosphate typically. #KILU #Mnemonic #AnionGap #Metabolic #Acidosis #diagnosis #differential

Causes of Metabolic Acidosis with Elevated Anion Gap - Differential Diagnosis Algorithm Elevated Anion Gap > 12 (Gain of H+) - Need to correct anion gap for albumin: For every drop of 10 for albumin (from 40) add 2.5 to the anion gap Decreased NH4 production and anion secretion • AKI/CKD Salicylate poisoning Lactic acidosis • Shock • Drugs • Inborn errors Ketosis • Diabetic ketoacidosis • Starvation/alcoholic Ketosis Toxic alcohol ingestion • Ethylene/Propylene glycol • Methanol Other ingestion • Paraldehyde, Iron, Isoniazid, Toluene, Cyanide #MetabolicAcidosis #AnionGap #Nephrology #Differential #Diagnosis #Algorithm #Causes

Toxic Alcohol Ingestions Metabolic Acidosis - Osmolar Gap - Anion Gap - Ketones - Ca Oxalate Stones - Reduced Vision • Alcohol (Ethanol) • Methanol • Ethylene Glycol • Isopropyl Alcohol • Propylene Glycol - Dr. Kenar Jhaveri @kdjhaveri #Toxicology #Alcohol #Ingestions #comparison #table #osmolargap #diagnosis