Hyperkalemia - Hypokalemia

Hyperkalemia

Almost always due to impaired renal excretion

• Reduced aldosterone or aldosterone responsiveness

• Renal failure

• Reduced distal delivery of sodium

3 major mechanism of diminished renal potassiun excretion

• Decreases the resting membrane of the cell (8mmol/L)

• Lack muscle excitability (6-7mmol/L)

• Fatal and can cause cardiac arrest (10mmol/L)

Effects of hyperkalemia to cardiac muscle

hyperosmolality

_ depletes potassium

Exercise

_ increases plasma potassium

Potassium

Increase _ directly stimulate aldosterone release form the adrenal gland

• Reduced aldosterone

• Renal failure

• Ph imbalance (acidosis) and deugs

• Pseudohyperkalemia

Causes of hyperkalemia

Reduced aldosterone

_

• Hyporeninemic hypoaldosteronism: most common cause of chronic hyperkalemia

• Hyporeninemic hypoaldosteronisn:

Most common cause of chronic hyperkalemia

Renal failure

Due to decrease tubular secretion

PH imbalance ( acidosis ) and drugs

_

• In acidosis, plasma potassium increases in each unit reduction of hudrogen that enters the RBC in exchange to potassium moving out the cell ( reduction H+ per unit = 0.2 - 1.7 increase K+ ) low insulin causes high potassiun in serum

Acidosis

• In _, plasma potassium increases in each unit reduction of hudrogen that enters the RBC in exchange to potassium moving out the cell ( reduction H+ per unit = 0.2 - 1.7 increase K+ ) low insulin causes high potassiun in serum

0.2 - 1.7

• In acidosis, plasma potassium increases in each unit reduction of hydrogen that enters the RBC in exchange to potassium moving out the cell ( reduction H+ per unit = _increase K+ ) low insulin causes high potassiun in serum

Insulin

Low _ causes high potassium in serum

Therapeutic potassium

Most common cause of hyperkalemia among hospitalized patients

HyperK+

Causes increase in H+ ions: metabolic acidoses

• captopril

• Spironolactone

• Digoxin

• Cyclosporine

• Heparin therapy

Hyperkalemic drugs

Digitalis

_ inhibits the Na, K, ATPase pump

• Na

• K

• Atpase pump

Digitalis inhibits _

• Thrombocytosis and leukocytosis

• Recentrifugation of SST

• Prolonged tourniquet application

• Excessive fist clenching

• IV fluid contamination ( possible hemolysis)

• High blast counts in acute and accelerated phase leukemia

Pseudohyperkalemia

chronicr hyperkalemia

If suspected _of renal cause - the first step is to measure plasma renin activity, plasma aldosterone and urinary excretion of Na+ and K+

• plasma renin activity,

• plasma aldosterone and

• urinary excretion of Na+ and K+

If suspected chronic hyperkalemia of renal cause - the first step is to measure _

• Hemoconcentraion

• In vitro hemolysis

• Systematic error

• Muscle activity

First step: rule out pseudohyperkalemia:

• Increase intake

• Shift of potassium fron cell

• Impired renal excretion

Next step is to ruke out the following:

3-0 - 3.4 mmol/L

Mild hypokalemia = plasma levels of _

• Decreases cell excitability resulting to cardiac arrhytmia and paralysis

• Cessation of contraction

Effect to cardiac muscle of hypokalemia

Cardiac arrhytmia

Common to dehydrated baby px

• Hypomagnesemia

• Impaired renal function/renal loss

• Extra renal loss

• Ph imbalance ( alkalosis and hormone)

• Psedohypokalemia

Causes of hypokalemia

Impaired renal function/renal loss

Most common cause of hypokalemia

Impaired renal function/renal loss

Attributed to increase activity of aldosterone and other mineralocorticoids

Diarrhea

Extra renal loss

• _ most common

Vomiting

Extra renal loss

_ : causes metabilolic alkalosis

Hypokalemia

_ is mainly the result of K loss in urine

Alkalosis

_ potassium decreases by 0.4mmol/L per 0.1 ph unit rise

0.4mmol/L per 0.1 ph unit rise

In akalosis potassium decreases by _

Alkalemia

_ promotes intracellular loss of H+ to neutralize the rise of pH so K+ ( and even sodium ) move into cells to maintain electroneutrality

electroneutrality

Alkalemia promotes intracellular loss of H+ to neutralize the rise of pH so K+ ( and even sodium ) move into cells to maintain _

Increase HCO3 and pCO2

_ leads to movement of potassium inside the cell ( low K in blood - alkalosis )

Aldosterone

_ secretiin contributes to hypokalemia

Insulin and catecholamines

Promotes the entry of K into the cell as glucose is transported inside the cells

Leukocytosis

_ potassium taken up by WBC when left at room temperature like active leukemic cells

• extra renal loss

• low intake

• intracellular shift

low urine potassium :

< 20mmol/L (low)/day

low urine potassium _mmol/L

renal loss

high urine potassium:

>30mmol/L (high)/day

high urine potassium: _ mmol/L

low urine K

not in kidneys

• dehydration

• diarrhea

• sweating

high urine K

due to kidneys

• aldosterone

• diuretics

• dehydration

• diarrhea

• sweating

low urine k, not in kidneys:

Aldosterone

diuretics

high urine K : due to kidneys :

heparinized plasma

_ preffered over serum

platelets

_ contain potassium that is released into serum on clot formation

• emission flame photometry

• ion selective electrode ( valinomycin gel )

• atomic absorption spectrophotometry

• colorimetry ( lockhead and purcell)

methods of potassium determination