assessment of Serum potassium levels. Description of pseudohyperkalemia and reverse pseudohyperkalemia. Causes of hyperkalemia. Clinical manifestation of hypokalemia and hyperkalemia.

1. Serum Potassium
Dr Sana Iqbal Janjua

2. Serum 3.5 - 5.1 mmol/L (Adult) Newborn 3.5 - 5.9 mmol/L
Plasma 3.4 - 4.8 mmol/L
CSF 70% of plasma
Urine 40 - 90 mmol/day
Stool 15.7 - 20.7 (18.2 + 2.5/day)
Diarrhea 60 mmol/day
Total Body Potassium
70 kg →Total Body Potassium
ECF 2%
3.5 - 5.1 mmol/L
ICF 98%
140 - 150 mmol/L

3. Why serum has higher potassium content than plasma?
Best container for serum potassium?
Sample of choice for potassium?
Preservative used for urinary potassium?
Important Facts About Potassium

4. ★ Is little affected by alteration of water balance
★ A poor guide of total body K+ content
★ Doesn’t change unless there is 10% alteration of body K+ content
Role in body
● Maintains Oncotic Pressure & intracellular volume
● Resting Membrane, Acting membrane Potential & neuromuscular function → Tissue
excitability
● Cardiac impulse
● Acid base balance
● Helps in NA/protein synthesis
● Facilitates cell growth
Important Facts About Potassium

5. Clinical Effects
Hypokalemia
Muscle weakness
Paralysis
Irritability
Tachycardia & conduction defects
Hyperkalemia
Muscle weakness
Flaccid paralysis
Mental confusion
Bradycardia & conduction defects

6. Hypokalemia
Rule out Pre analytical error
● Sample dilution (all parameters will be low)
● Electrolytes exclusion effect (electrolytes will be low with indirect ISE)
Causes of Hypokalemia
1. Decrease dietary potassium (chronic starvation)
2. Redistribution of potassium in body compartments
3. True potassium deficit

7. Insulin therapy
Insulin → express GLUT-4 channels on cells (muscles/adipose tissue/RBCs)
→GLUT-4 channel Cotransport Glucose/K+ into the cells →shift of serum
potassium into cells → Hypokalemia
Alkalosis
￬ H+ in plasma → to compensation H+ comes out of cells (mainly RBCs) into
plasma →K+ moves inside cells to keep electrochemical gradient constant →
hypokalemia
￬ H+ in plasma → DCT (kidney) conserve H+ by decreasing its excretion →to
keep electrochemical gradient K+ is secretion into lumen → ￪K+ excretion
→hypokalemia
Redistribution of potassium in body compartments

8. ￪ Catecholamine activity
Beta 2 receptor stimulation → dose dependent activation of Na/K ATPase pump
Hypothermia
Increase activity of Na/K ATPase pump in induction phase
Refeeding syndrome
Hypokalemia (weakness), hypophosphatemia (hypotension, fits) and
hypomagnesemia (hypocalcemia, GI symptoms) after initiation of feeding in
malnourished patients is called refeeding syndrome
Already deficiency of nutrients → Refeeding → ↑glucose in blood → release of
insulin → movement of K+, Mg+2 and PO-3 into cells along with glucose
Redistribution of potassium in body compartments

9. Periodic hypokalemic paralysis
Familial hypokalemic periodic paralysis
Gene mutation →mutated Kir 2.6 potassium channel in skeletal muscles
→increase K+ influx → altered muscle membrane excitability →paralysis
Thyrotoxic hypokalemic periodic paralysis
Kir 2.2 transcription is regulated by thyroid hormone →increase thyroid hormone
→ increase K+ influx → altered muscle membrane excitability →paralysis
Redistribution of potassium in body compartments

10. Loss of potassium from body →￬ Total body Potassium
K+ loss through kidneys
K+ loss through extra renal source
24 Hours Urinary K+ < 25 mmol/day → Extrarenal loss of K+
True Potassium Deficit
Through Gut Through Skin
Diarrhoea Excessive sweating
Fistula (involving gut) Burns
Ileostomy

11. 24 Hours Urinary K+ > 25 mmol/day → Renal loss of K+
True Potassium Deficit
Defective renal
tubules
Drugs ￪ Mineralocorticoid effect Compensatory
RTA (Type I/II) Thiazide Primary hyperaldosteronism Metabolic Alkalosis
ATN (Diuretic phase) Loop diuretics Secondary hyperaldosteronism NG suction Vomiting
Amphotericicn B Excess of Glucocorticoids Hypomagnessemia
Penicillin AME

12. 24 hrs urinary K+
Renal >25 mmol/L Extra renal <25 mmol/L
ABGs
Metabolic Alkalosis
Metabolic Acidosis
Normal
RTA Type I/II 24 hrs urinary Cl-
>10 mmol/L < 10 mmol/L
￪Aldosterone
￪Glucocorticoid
Vomiting
NG suction
Diuretics
Penicillin
ATN
Amphoterici
n B

13. Hyperkalemia →5.1 mmol/L
Severe hyperkalemia → > 7.0 mmol/L
Fatal hyperkalemia → > 10 mmol/L
Rule out Pre analytical error
Pseudohyperkalemia
● Traumatic venipuncture
● Prolonged tourniquet
● K+ - EDTA contamination
● Hemolytic sample
● Vigorous shake during transport
● Prolonged handling time
● Improper storage
Hyperkalemia

14. Reverse pseudohyperkalemia Leukemia (>100000/uL)
In vitro phenomenon in which plasma potassium concentration rises higher than
serum potassium concentration, usually due to extreme leukocytosis
Increase iron stores
Leukemic leukocytes are more fragile than normal leukocytes, leading to in vitro
lysis during centrifugation of plasma specimens and elevating potassium
concentrations. In serum specimens, the formation of a fibrin clot is hypothesized
to entrap and stabilize tumor cells during centrifugation. Whole blood can be used
as an alternative specimen in cases of reverse pseudohyperkalemia
Leukocytosis has higher energy consumption leading impaired Na/K ATPase
pump
Increase sensitivity to heparin induced membrane damage in haematological
malignancies
Hyperkalemia

15. Hyperkalemia
Pseudohyperkalemia →False ￪ in serum K+ in comparison to the normal plasma
levels
Pseudohyperkalemia →False ￪ in plasma K+ in comparison to the normal serum
levels
What is the difference between pseudohyperkalemia and reverse
pseudohyperkalemia?
Aldosterone escape phenomenon and lack of edema: Potassium-wasting
effect of excess aldosterone is counterbalanced by the potassium-retaining
effect of hypokalemia itself

16. Causes of Hyperkalemia
1. Redistribution
a. Acidosis (compensatory)
b. Drugs
i. Beta blocker
ii. Digoxin
c. ￬ Insulin (type 1 DM with severe insulin deficiency)
d. Release from ICF
i. Hemolytic anemia
ii. Tissue hypoxia
iii. Rhabdomyolysis
iv. Heavy exercise
v. Status epilepticus
vi. Severe burn

17. Causes of Hyperkalemia
2. True potassium gain
Normal kidneys are able to handle potassium load. When kidneys are able to
excrete out extra K+ look for underlying renal disease
A. Increase potassium intake (supplementation with compromised renal
function)
B. Massive transfusion
C. Hemolytic transfusion reaction

18. Causes of Hyperkalemia
2. True potassium gain
A. Decreased potassium excretion
a. Primary renal defect
b. Mineralocorticoid deficiency
i. Hypoaldosteronism
ii. Hyporeninemic Hypoaldosteronism
iii. Addison's disease
c. Drugs inhibiting Aldosterone
i. ACE inhibitors
ii. ARB II
iii. NSAIDs
B. Potassium sparing diuretics
a. Spironolactone
b. Amiloride