Hypokalemia Flashcards
what is potassium
major intracellular cation
intracellular potassium
140-155 mmol/l
percentage of extracellular potassium
2%
how is cell membrane potential maintained
Na+/K+/ATPase pump
alteration of the K+ ration
has profound effects on
excitable tissue like muscle and nerves
hypokalemia definition
Hypokalemia is a potentially life-threatening decrease in extracellular potassium concentration
hypokalemia range
K+ < 3.5 mmol/l
hypokalemia life threatening range
K+ <2.5 mmol/l
causes of hypokalemia
- excessive losses (non- renal)
- renal potassium losses
- redistribution from extra to intracellular
- pseudohypokalemia
excessive losses (non- renal)
gastroenteritis - acute and chronic
- gastro-intestinal fistula
- excessive sweating in dry environments with prolonged exertion
renal potassium losses
- Drugs: Thiazide diuretics > loop and osmotic diuretics
- distal renal tubular acidosis
- magnesium deficiency
- Rare: Barrter, Gitelman and Liddle syndromes
redistribution from extra to intracellular
- treatment of DKA (acute insulin administration)
- Drugs: β2 agonists,theophylline,caffeine,chloroquine,decongestants
- 1°or 2° hyperaldosteronism (CCF,Hepatic insufficiency,Nephrotic syndrome)
pseudohypokalemia
- abnormal white blood cells - AML
history and symptoms
Take an AMPLE history
Can be asymptomatic or non-specific
May present with fatigue, weakness, muscle cramps, palpitations, paralysis
Can affect intestinal smooth muscle → ILEUS
hypokalemia
‘A SIC WALT’
A- alkalosis
S- shallow respirations
I- irritability
C- confusion and drowsiness
W- weakness and fatigue
A- arrhythmias
L- lethargy
T- thready pulse
examination
Usually unremarkable and will depend on the underlying cause
Look for causes/precipitants
investigations: ECG
arrhythmia, non-specific changes, T waves flattened, U waves, ST changes and T wave inversion. Cardiac arrest: PEA, asystole
hypokalemia ecg
- slightly prolonged PR interval
-slightly peaked P waved - ST depression
- Shallow T wave
- Prominent U wave
other investigations
- Electrolytes,Urea,Creatinine
- Bloodgas
- Urinary K+
- May need CK (hypokalemia can cause rhabdomyolysis)
- Other investigations to be guided by the suspected underlying cause
management
- Stabilise ABCs
- Stop ALL drugs that may cause or worsen hypokalemia
- Look for underlying cause of hypokalemia
- General measures: Correct hypovolemia/volume deficits with isotonic fluids
- Parenteral K+ replacement
- oral K+ replacement
Parenteral K+ replacement:
- safe replacement rate = 10mmol per hour
- 20-40 mmol KCL in 200ml 0.9% normal saline @ 50ml/hr ( over 4 hours)
1 ampoule = 20mmol - High concentrations or more rapid administration should be done very carefully,
through a CENTRAL LINE and with CONTINUOUS CARDIAC MONITORING! - maximum dose 40mmol/hr in arrest situation
- Replace Mg (1-2g MgSO4 in 50-200ml normal saline over 10minutes)
- For suspected/proven hypomagnesaemia and refractory hypokalemia
- 20-40 mmol KCL in 200ml 0.9% normal saline @ 50ml/hr ( over 4 hours)
oral K+ replacement
- Food sources: BANANAS, dried fruit, nuts, avocado, broccoli, spinach, orange juice,
white mushrooms, french fries- Oral preparations: KCL, potassium phosphate, potassium bicarbonate, K-citrate
- Dosage: 40-100mmol/day for treatment and 20mmol/day for prevention of hypokalemia
referral criteria to physician
§persistent hypokalemia despite optimal management
§investigations as part of work-up not offered at your facility
§Conditions causing hypokalemia that can’t be managed at your facility
IF UNSURE WHETHER TO REFER OR NOT, CONTACT THE PHYSICIAN
AT YOUR CLOSEST REFERRING FACILITY
discharge criteria/ checklist
† K+ corrected
† Underlying cause found and treated/corrected
† Drugs causing/aggravating hypokalemia stopped/decreased
† Appropriate outpatient follow-up arranged
† Advised on K+ containing foods
† Consider oral K+ supplement for patients with a very high risk of
cardiac dyfunction/arrhythmia
