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K+ < 3.5 meq/l

R/O pseudo hypo K+

R/O redistribution • Periodic paralysis• Insulin, B2 agonist• refeeding• Rx neutropenia with G-CSF• Rx anemia with B12, folate• Ba poisoning, acute chloroquine toxic

WC > 100,000

• TTKG > 4 or • 24 hour urine K+ > 20 meq

No• diarrhea • sweating• remote diuretic use

= renal loss

• TTKG < 2 or • 24 hour urine K+ < 10 meq

Renal K+ loss

Metabolic acidosis normal Metabolic alkalosis

High gap• DKA

• ketoacidosis• methanal• ethylene glycol

Normal gap• RTA

• CA inhibitor• glue sniff

• Non-oligulic ATN• Diuretic phase ATN• low serum Mg• high dose PGs• TI disease

Urine Cl-

< 10 meq/l(hypo-volumemia)

>20 meq/l(hyper-volumemia

orCl- losing)

• vomiting• NG suction

Normal BP High BP

R/O HT with diuretic use

• resent diuretic use• Barter• Gitelman

High reninHigh aldosterone

low reninHigh aldosterone

low reninlow aldosterone

• RAS• malignant HT• scleroderma• renin producing tumor

• 1o hyperaldosteronism

• Liddle (mutationof Na channelincrease Na reabsorption)

•Increase mineralocorticoid• Very high cortisol• 11 B-OH def• Licorice• fludocortisone• 17 a-OH def

K+ > 5.5 meq/l

R/O pseudo hyper K+ • Hemolysis

• WC > 70,000• Plt > 1,000,000

If > 6.0 EKG should be done

K+ loadExternal source• diet

• IV fluid• old blood > 5 day

Internal source• intravascular hemolysis

• rhabdomyolysis• tumor lysis syndrome• UGIB• absorb hematoma• major trauma or Sx• severe sepsis

• TTKG > 7 or • 24 hour urine K+ > 200 meq

Redistribution• beta-block (esp.

nonselective beta 1)• metabolic acidosis• periodic paralysis• severe exercise • Digitalis toxic• fluoride toxic

yesno

Defect of renal excretion

Na+

K+

3Na+

2K+

ATP

Collecting tubule

Principal cell

Aldosterone

Aldosterone

Aldosterone+

+

+

lumen basolateral

negative

Cl-

Defect of renal excretion

site cause

Low distal Na delivery

low ECV, low GFR(<15), Gordon syndrome(psudohypoaldosterone type II)

Defect of Na channel (ENAC)

triamterene, amiloride

Defect of Cl-channel

heparin, cyclosporine

Defect of K+ channel (ROMK)

cyclosporine

Defect of aldosterone

ACE-I, ARB, spironolactone, NSAIDs, heparin, cyclosporineDM,1o hypoaldosterone,1o adrenal insuff

Intracellular (Hb, protein)

and Bone Buffering (carbonate)

H+ + HCO3- H2CO3 H2O + CO2

RenalNH4

+ excretion(HCO3- regeneration)

Tritratable acid excretionHCO3

-reclamation

Lung

Fixed AcidA- + H+

Volatile acid(from CO metabo)

GluconeogenesisAnionic Amino acid

Anion gapNa

+- ( Cl

-+ HCO3

-)

Unmeasured anionUnmeasured cation

Measured cationNa+

Measured anionCl-, HCO3

-

K+, Ca2+ , Mg2+ alb , phosphate , sulphate, organic cation ( M protein )

Delta gap in met.acidosis ; due to A-

( HA H+ + A- )

Delta HCO3-◦ 60% H+ buffer in intracellular and bone pure

met.acidosis delta gag/delta HCO3- may be 1:1 to 2:1

◦ Resp.acidosis decrease delta HCO3-

◦ Resp.alk increase delta HCO3-

1-2 pure wide gap acidosis

<1 wide gap + normal gap met.acidosis

wide gap met.acidosis + resp.alk.

>2 wide gap met.acidosis + met.alk.

wide gap met.acidosis + resp.acido.

=Measured osmol – calculated osmol

Calculated osmol

= 2(Na+K) + BUN/2.8 + Glu/18

In wide gap met.acidosis if > 25 suggest methanol or ethylene glycol ingestion

Wide P osmolol gap can be found in lactic or ketoacidosis

Rarely elevated in salicylic acidosis

because toxic level is very low.

Anion gap(Na+ + K+) - Cl-

Unmeasured anion

Unmeasured cation

Measured cationNa+ + K+

Measured anionCl-

NH4+

Urine anion gap (urine net charge)

NH4+ is U unmeasured cation

Urine is neutral.

When acidemia high urine NH4+ high

U unmeasured cation neg urine net charge

=Measured osmol – calculated osmol

Calculated osmol

= 2(Na+K) + UUN/2.8 + Glu/18

More than half of urine osmolol gap is ammonium.

Unmeasured anion are already included in 2(Na+K)

Low serum HCO3-

Met acidosis ?R/O resp. alkalosis

OrMixed acid-base

Serum anion gap (collected with alb)

Wide gap Normal gap

Delta gap/Delta HCO3-

Wide gap met. AcidosisLactic acidosisKetoacidosis (dibetes/starvation/alcoholic)

Toxic (methyl or ethyl alcohol/ethylene glycol/salicylate

ABG

Wide gap met.acidosisWith ?

Normal gap hyperchloremic met. acidosis

Fe HCO3->15 Fe HCO3

-<15

CA-I Proximal RTA (type 2)

Isolated type Fanconi synd.

Fe HCO3- <15

Negative urine net chargeOr

Urine osmolar gap > 100 mmol/lOr

Urine ammonium >50 mmol/day

yes no

High ammonium excretion(diarrhea, acid load) Low ammonium excretion

RTA type 1 (low serum K+) orRTA type 4 (high serum K+)

Generation

Correction

• H+ loss (renal, extrarenal)• H+ shift in to cells• Retention of HCO3-• Contraction Alkalosis

• Increase HCO3- filtration• Decrease HCO3- reabsorption• Decrease HCO3- regeneration

(=decrease NH4+ secretion)• Increase HCO3- secretion

◦ H+loss

GI; vomiting, NG tube suction, antacid

Renal; thiazide or loop diuretic, 1o mineralocorticoidexcess, Bartter or Gitelman synd., post hypercapnia

◦ H+shift in to cell

Hypo K+

◦ HCO3- Gain; administration of NaHCO3, organic

anion(citrate, acetate)

◦ Contraction alkalosis; loss CL- > HCO3-

Cl- losing diarrhea

Generation

Maintenance

Correction

• H+ loss (renal, extrarenal)• H+ shift in to cells• Retention of HCO3-• Contraction Alkalosis

• decrease ECF volume• Cl- depletion• K+ depletion• renal failure