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A Case. 25 y.o . male 2 weeks of presyncope and fatigue Supine HR 70bpm, Standing HR 116bpm ABG: pH 7.54, pCO2 47, PO2 92, HCO3 34 . Objectives. Review pathophysiology of metabolic alkalosis Discuss an approach to metabolic alkalosis Outline treatments for metabolic alkalosis.
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A Case 25 y.o. male 2 weeks of presyncope and fatigue Supine HR 70bpm, Standing HR 116bpm ABG: pH 7.54, pCO2 47, PO2 92, HCO3 34
Objectives • Review pathophysiology of metabolic alkalosis • Discuss an approach to metabolic alkalosis • Outline treatments for metabolic alkalosis
Pathophysiology Two Necessities for Metabolic Alkalosis • Initiation Factor – increase HCO3 • Maintenance Factor -process suppressing normal renal response
Tubule Blood Na+ Na+ K+ H+ 3HCO3- HCO3- + H+ H2CO3 Na+ H2CO3 CO2 + H2O Pathophysiology What are these processes? • Decreased ECV (especially with hypoCl-) H2O + CO2 Proximal Convoluted Tubule
Pathophysiology • Hypokalemia Intracellular Extracellular K+ H+
Pathophysiology • Aldosterone Tubule Blood K+ H+ HCO3 HCO3- + H+ H+ H2CO3 Cl- H2CO3 CO2 + H2O H2O + CO2 Intercalated Cell
An Approach History: -vomiting, diarrhea, diuretic use, family hx, alkali load? P/E: -volume status (cap. refill, skin turgor, postural hypotension/tachycardia, BP) -syndromic features (Cushingoid) Note: Don’t forget to do a cardiac exam to exclude arrhythmias caused by electrolyte abnormalities.
Chloride Sensitive Obtain a spot urine chloride If urine Cl- < 20 mEq/L: GI Losses: -Vomiting/NG -Villous adenoma (secretory diarrhea) Renal Losses: -Remote diuretic use -Post hypercapnea (with associated decreased EABV) -Non-reabsorbable anions (eg: penicillin)
Chloride Insensitive If Urine Cl- > 20 mEq/L, obtain serum K+: Normal Serum K+: -Alkali load (citrate, acetate, lactate) -Milk-Alkali Syndrome (CRF from hyperCa with alkali) Decreased Serum K+: Check volume status
Chloride Insensitive: Volume status Hypertension -Primary hyperaldosteronism -Malignant hypertension -Renin secreting tumour -Cushing’s Syndrome -Liddle’s Disease (AD ENaC mutation) -Congenital Adrenal Hyperplasia
Chloride Insensitive: Volume Status Normotension/Hypotension -Current diuretic use -HypoK+/Mg2+ -Bartter’s Syndrome
Come again? Metabolic Alkalosis Urine Cl- <20mEq/L Urine Cl- >20mEq/L GI Loss Renal Loss Normal K+ Decreased K+ Vomit/NG Villous Adenoma Remote diuretic use Post hypercapnea Non-reabsorbable anions Alkali load • Hypertension Primary hyperaldo Malignant HTN Renin secreting tumour Cushing’s Syndrome Liddle’s Disease CAH Normo/Hypotension Recent diuretic use HypoK+/Mg2+ Bartter’s Syndrome
Treatment Chloride Sensitive: Volume replacement with NaCl solution (except in those with edema) Chloride Insensitive: Correct underlying cause Block aldosterone activity Severe Metabolic Alkalosis (pH >7.6) IV HCl Dialysis