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

A Case

Objectives

1. Review pathophysiology of metabolic alkalosis

2. Discuss an approach to metabolic alkalosis

3. Outline treatments for metabolic alkalosis

Pathophysiology

Two Necessities for Metabolic Alkalosis

1. Initiation Factor – increase HCO3

2. Maintenance Factor -process suppressing normal renal response

Pathophysiology

What are these processes?

1.Decreased ECV (especially with hypoCl-)

H2O + CO2

BloodTubule

Na+

H+

Na+

Na+

K+

HCO3- + H+

H2CO3

H2CO3

CO2 + H2O

3HCO3-

Proximal Convoluted Tubule

Pathophysiology

2. Hypokalemia

Extracellular

K+

H+

Intracellular

Pathophysiology

3. Aldosterone

BloodTubule

K+

H+

Cl-

HCO3- + H+

H2CO3

H2CO3

CO2 + H2O

HCO3

H2O + CO2

H+

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

Vomit/NGVillous Adenoma

Renal Loss

Remote diuretic use Post hypercapneaNon-reabsorbable anions

Normal K+

Alkali load

Decreased K+

HypertensionPrimary hyperaldoMalignant HTNRenin secreting tumourCushing’s SyndromeLiddle’s Disease CAH

Normo/HypotensionRecent diuretic useHypoK+/Mg2+Bartter’s Syndrome

Treatment

Chloride Sensitive:Volume replacement with NaCl solution(except in those with edema)

Chloride Insensitive:Correct underlying causeBlock aldosterone activity

Severe Metabolic Alkalosis (pH >7.6)IV HClDialysis

QUESTIONS?