Hypokalemia

Question 1

what is potassium

Answer 1

major intracellular cation

Question 2

intracellular potassium

Answer 2

140-155 mmol/l

Question 3

percentage of extracellular potassium

Answer 3

2%

Question 4

how is cell membrane potential maintained

Answer 4

Na+/K+/ATPase pump

Question 5

alteration of the K+ ration

Answer 5

has profound effects on
excitable tissue like muscle and nerves

Question 6

hypokalemia definition

Answer 6

Hypokalemia is a potentially life-threatening decrease in extracellular potassium concentration

Question 7

hypokalemia range

Answer 7

K+ < 3.5 mmol/l

Question 8

hypokalemia life threatening range

Answer 8

K+ <2.5 mmol/l

Question 9

causes of hypokalemia

Answer 9

1. excessive losses (non- renal)
2. renal potassium losses
3. redistribution from extra to intracellular
4. pseudohypokalemia

Question 10

excessive losses (non- renal)

Answer 10

gastroenteritis - acute and chronic
- gastro-intestinal fistula
- excessive sweating in dry environments with prolonged exertion

Question 11

renal potassium losses

Answer 11

• Drugs: Thiazide diuretics > loop and osmotic diuretics
  - distal renal tubular acidosis
  - magnesium deficiency
  - Rare: Barrter, Gitelman and Liddle syndromes

Question 12

redistribution from extra to intracellular

Answer 12

• treatment of DKA (acute insulin administration)
• Drugs: β2 agonists,theophylline,caffeine,chloroquine,decongestants
  - 1°or 2° hyperaldosteronism (CCF,Hepatic insufficiency,Nephrotic syndrome)

Question 13

pseudohypokalemia

Answer 13

• abnormal white blood cells - AML

Question 14

history and symptoms

Answer 14

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

Question 15

hypokalemia
‘A SIC WALT’

Answer 15

A- alkalosis

S- shallow respirations
I- irritability
C- confusion and drowsiness

W- weakness and fatigue
A- arrhythmias
L- lethargy
T- thready pulse

Question 16

examination

Answer 16

Usually unremarkable and will depend on the underlying cause

Look for causes/precipitants

Question 17

investigations: ECG

Answer 17

arrhythmia, non-specific changes, T waves flattened, U waves, ST changes and T wave inversion. Cardiac arrest: PEA, asystole

Question 18

hypokalemia ecg

Answer 18

• slightly prolonged PR interval
  -slightly peaked P waved
• ST depression
• Shallow T wave
• Prominent U wave

Question 19

other investigations

Answer 19

2. Electrolytes,Urea,Creatinine
3. Bloodgas
4. Urinary K+
5. May need CK (hypokalemia can cause rhabdomyolysis)
6. Other investigations to be guided by the suspected underlying cause

Question 20

management

Answer 20

1. Stabilise ABCs
2. Stop ALL drugs that may cause or worsen hypokalemia
3. Look for underlying cause of hypokalemia
4. General measures: Correct hypovolemia/volume deficits with isotonic fluids
5. Parenteral K+ replacement
6. oral K+ replacement

Question 21

Parenteral K+ replacement:

Answer 21

• 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

Question 22

oral K+ replacement

Answer 22

• 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

Question 23

referral criteria to physician

Answer 23

§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

Question 24

discharge criteria/ checklist

Answer 24

† 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