Potassium

1. Clinical Biochemistry
SIMS-305
Dr. Ali Raza
Senior Lecturer
Centre for Human Genetics and Molecular Medicine (CHGMM),
Sindh Institute of Medical Sciences (SIMS), SIUT.
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2. POTASSIUM
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3. • major intracellular cation
• Intracellular [K+] = 150 mEq/L
• Plasma potassium is 3.5-5 mEq/L.
• Na+-K+ ATPase or sodium pump maintains
concentration gradient.
• Filtered by the glomeruli of the kidney and
reabsorbed by proximal tubules
POTASSIUM
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4. POTASSIUM FUNCTIONS
Many functions of potassium and sodium are carried
out in coordination with each other
• Influences the muscular activity
• Involved in acid-base balance
• Involved in neuromuscular irritability and nerve
conduction process.
• It has an important role in cardiac function
• K+ as cofactor: Pyruvate kinase
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5. Potassium -- CLINICAL IMPORTANCE
• High and low values are clinically important.
• Extracellular levels of potassium are
measured on a sample of serum.
• RBCs contain a large amount of potassium,
care must be taken that sample is not hemolysed.
• On standing, potassium value changes,
Plasma potassium must be measured as
soon as possible on fresh sample.
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6. Potassium-- CLINICAL IMPORTANCE
• Hyperkalaemia
• Hypokalaemia
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7. Potassium-- CLINICAL IMPORTANCE
Hyperkalaemia
Excretion of potassium in normal persons are so
effective that it is difficult to produce hyperkalaemia
by simply increasing the oral intake.
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8. Hyperkalaemia are due either to:
1. Anuria
2. Tissue damage
3. Violent muscle contraction
4. Addison’s disease
5. Diabetes mellitus
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9. Hyperkalaemia
1- Kidney failure :
 Anuria (failure of the kidneys to produce urine):
Complete shut-down of kidney function
• Decreased excretion of potassium cause results in
increasing conc. of K+.
• kidney failure is associated with sudden release of
intracellular potassium from any organ.
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10. Hyperkalaemia
2-Tissue damage:
Damage to body cells from any cause in release of
cell contents including K+ into ECF.
 Examples
Crush injuries, with damages to large volumes of
Muscle tissue,
Massive hemolysis
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11. Hyperkalaemia
3-Violent Muscle Contraction:
Vigorous Exercise :
• Produces a release of K+ from muscle cells into the
extracellular space and may increase in plasma K+.
• Same mechanism is responsible for the increase seen
in status epilepticus.
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12. Hyperkalaemia
4-Addison’s Disease:
• In the absence of aldosterone,
the exchange of sodium for potassium in
the kidney is reduced,
• with increased loss of sodium and retention of K+ in
body.
Low serum sodium and high serum K+
are characteristic of this disease.
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13. Hyperkalaemia
5-Diabetes Mellitus:
• In ketoacidosis, substantial loss of intracellular K+ to
the ECF.
• Due to increased activity of Na+-K+ ATPase which
results from impaired glucose metabolism.
• If ketoacidosis presents for a long time, there will
be major depletion of total body K+.
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14. Hyperkalaemia
 Diabetes Mellitus:
• Treatment with insulin allows
a) resumption of Na+ pump activity
b) movement of K+ back into the cells
c) an abrupt fall in plasma K+
• Administration of K+ to restore lost in the urine during
the period of acidosis.
Frequent monitoring of K+ is vital to DM
with ketoacidosis.
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15. Low serum K+ usually results from the
depletion of total body K+.
Potassium level < 3.5 mmol/L.
Hypokalaemia
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16. K+, dietary deficiency is uncommon
• All food contains large quantities of K+.
• Dietary supplements of K+ are required only in patients
a) with some disease
b) Drugs use which causes potassium depletion.
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17.  Common causes of hypokalaemia are:
1. Loss of K+ in GI secretions
2. Loss of K+ in urine
3. Loss of extracellular K+ into the intracellular space
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18. Hypokalaemia
1- Loss of K+ in GI secretions
• Prolonged vomiting
• Severe diarrhoea
• Operation (ileostomy)
• Laxative: Develop chronic mild diarrhoea cause low K+
• Mucous secreting tumour called a Cillous adenoma.
– Secretes large amounts of K+ into lumen of colon.
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19. Hypokalaemia
2-Loss of K+ in urine
• Many medications decrease total body sodium such
as some diuretics also cause loss of K+.
• Thiazides, Acetazolamide for HTN and heart
• Thiazide, diuretics drug causes of low plasma K+.
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20. Hypokalaemia
3-Loss of extracellular K+ into the intracellular space:
• Treatment of diabetes ketoacidosis causes a rapid fall in
plasma K+ from a state of hyperkalaemia to normal and
then to hypokalaemia as the acidosis is brought under
control.
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21. Elements Requirement Group
1
Zn, Fe, and Mn
2
Na, K, Ca,
3
As, CN–, Hg
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Sodium Pump is also called
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Sodium Pump is found in plasma membrane of
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How many sodium and potassium ions are
pump outside and inside the cell membrane
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write functions of Sodium – (3)
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Specific conditions in which hypernatraemia
occurs (3)
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Specific conditions in which Hyponatraemia
occurs (3)
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22. Elements Requirement Group
1 Zn, Fe, and Mn < 100 mg III/ Trace elements, Essential elements
2 Na, K, Ca, >100 mg II/macro elements, Principal elements
3 As, CN–, Hg Group V
4 Sodium Pump is also called Na+-K+ ATPase
5 Sodium Pumps are found in plasma membrane of Intestinal and Renal cells
6 How many sodium and potassium ions are pump
outside and inside the cell membrane
______ Na+ (outside)
______ K+ (Inside)
7 write functions of Sodium – (3) Fluid balance , Blood viscosity
Acid-base balance
Neuromuscular excitability
8 Specific conditions in which hypernatraemia occurs
(3)
Simple Dehydration
Diabetes Insipidus
Osmotic Loading
Excess Sodium
9 Specific conditions in which Hyponatraemia Diuretic medication
Excessive sweating
Kidney diseases
Congestive heart failure
Gastrointestinal loss
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