hypokalemia

1. HYPOKALEMIA
• Diagnosis
• Potassium homeostasis
• Causes
• investigations
• Treatment
• Approach

2. HYPOKALEMIA
• Normal range - 3.5 to 5 mEq/L
• Hypokalemia defined as plasma concentration of K+ < 3.5 mEq/L
Mild Hypokalemia 3.0 – 3.5 mEq/L : asymptomatic
Moderate Hypokalemia < 3.0 mEq/L : symptomatic
Severe Hypokalemia <2.5 mEq/L

3. Potassium homeostasis
• Daily requirement : 3-4
g/day
• Intracellular : 98%
• Extracellular : 2%
(<2% of total body K+)
• Excretion :
-90% - kidney
-10% - git
-1% - skin

4. Renal excretion
• PCT – Max
absorption
• Regulated by
aldosterone and
corticosteriods

5. Biochemical functions
• maintains intracellular osmotic pressure
• Regulates acid-base & water balance in the cells
• Required for transmission of nerve impulse
• For biosynthesis of proteins by ribosomes
• extracellular k+ influences cardiac muscle activity

6. HYPOKALEMIA – CLINICAL MANIFESTATIONS
• CVS :
ECG changes, atrial/ventricular
arrhythmias, digitoxicity
• SKELETAL MUSCLE :
Weakness, cramps, tetany ,
paralysis, rhabdomyolysis
• SMOOTH MUSCLE :
Constipation, Ileus, urinary
retention
• ENDOCRINE : Carbohydrate
intolerance

7. Hypokalemia
“ Causes ”
Decreased intake Redistribution into cells
Increased losses
Renal extra-renal
Loss loss

8. Decreased Intake
• Starvation (anorexia nervosa, geophagia)
• alcoholism

9. Redistribution into cells
K+ uptake by cells
(hypokalemkia)
activates Na-K ATPase channel
Insulin
B2 agonist
Thyroid hormone
alkalosis
K+ uptake by cells
(hypokalemkia)
Increased activity of
sympathetic nervous system
Acute head injury /MI
Overdose of theophylline
/propranalol
Hyperthyroidism
B2 agoinst

10. Redistribution into cells
TPP (Thyrotoxic Periodic
Paralysis)
• Mutation of thyroid
hormone sensitive K+
channel.
• Mutation of Na-K ATPase
channel
FHPP(Familial Hypokalemic
Periodic Paralysis)
• Mutation of L Type Ca+
channel / skeletal Na +
channel.

11. Acid Base balance
Alkalosis
Hypokalemia
Promotes K+ uptake by
cells
Acidosis
hyperkalemia
Diminishes K+ uptake by
cells

12. Increased lossses
Renal loss
• Distal flow & distal Na
delivery (diuretics,salt
wasting neuropathies)
• secretion of K+
- MC excess (10/20
hyperaldosteronism ,bartter ,
gitelman, liddle syndrome)
-apparent MC excess
• Magnesium def
Extra renal loss
• GI Loss
Vomiting , malabsorption,
diarrhoea , enteric fistulas
• Sweat Loss
Heat stroke ,heavy excersise,
fever

13. Ecg changes
• T wave inversion or flattening
• Prominent U wave
• ST depression
• Narrow QRS complex
• QTc prolongation
• Peaked p wave

14. “ Pull & Push Effect ”

15. INVESTIGATIONS
• History, physical Examination ,dietry Habbits
• Serum K+
• Urine K+ /CL-
• Urine K+ /creatinine ratio
• TTKG (Transtubular K Gradient)
• Aldosterone level
• PRA (plasma renin activity)
• Thyroid hormone levels

16. HYPOKALEMIA-TREATMENT
(1) decreasing potassium losses
(2) replenishing potassium stores
(3) evaluating for potential toxicities
(4) determining the cause in order to prevent future episodes.