Hypokalaemia

1. Is the patient unwell?

• ABCDE approach 

2. Is the result a true value?

• Is there a previous level?

3. Does the patient have any symptoms or signs?

• May indicate the significance and rapidity of electrolyte change
• Muscle fatigue, cramps, paralysis
• ECG changes - flattened/inverted T waves, ST depression, QTC prolongation, U waves, arrhythmia (atrial or ventricular)

4. Are there culprit drugs?- consider stopping them

• Diuretics, IV insulin, nebulised salbutamol

5. Causes?- investigate for and treat them

• GI loss, body fluid loss (e.g. from GI fistula), refeeding syndrome
• Alkalosis - check bicarbonate
• Severely Low magnesium (<0.3 mmol/l) - treat this first
• If cause not immediately obvious – take spot urine potassium
• excess steroids (exogenous or in cushings) - RARE, particularly in context of exogenous. Do NOT stop exogenous steroids in context of hypokalaemia without senior discussion.

Severe (K⁺ <2.5 mmol/L OR symptoms OR ECG changes)

• 1 bag of 40 mmol potassium chloride in 1 litre of 0.9% sodium chloride 250 ml/hour
• Additionally prescribe oral potassium replacement (Sando-K 2 tablets three times per day – each tablet contains 12 mmol potassium) if oral route preserved
• Maximum rate of administration is 10 mmol K⁺ per hour- this can be given peripherally but will need central access and HDU if the fluid volume needs to be reduced
• If patient is at extremes of body weight or at risk of fluid overload the infusion rate or volume may need to be adjusted
• Check K⁺ at end of infusion. It is likely that a second bag may be required 
  • If needing >2 bags of IV K replacement please discuss with senior decision maker regarding base IV fluid (0.9% saline vs Dextrose vs 0.18%saline/4%dextrose) and consider alternating to prevent hyperchloraemia (acknowledging limit of administration speed))
• Check K⁺ again after 6-12 hours

Moderate (K⁺ 2.5-3.0 mmol/L AND asymptomatic)

• 40 mmol potassium chloride in 1 litre 0.9% sodium chloride or 5% dextrose at 125 ml/hour
• Alternatively oral potassium replacement (Sando-K 3 tablets three times per day – each tablet contains 12 mmol potassium)
• Monitor K⁺ daily until K⁺ >3.0 mmol/L then manage as per mild
• If at risk of cardiac arrhythmia (for example ischaemic heart disease, heart failure, patient known arrhythmia or taking digoxin)– treat as per severe

Mild (K⁺ >3.0 mmol/L)

• Oral potassium replacement  (Sando-K 3 tablets three times per day – each tablet contains 12 mmol potassium) for 3 days then recheck K+ level

Make sure you investigate cause including checking magnesium and bicarbonate levels

Of note, maintenance potassium requirement is 1mmol/kg/day. Please consider oral intake and ongoing loss when calculating maintenance, and any replacement requirements. 

Seek senior advice if concerns and in particular if:

• Patient fluid restricted or at risk of fluid overload
• Severe hypokalaemia

Cardiac monitoring or HDU review?

• Cardiac monitoring needed in severe hypokalaemia only if patient a candidate for escalation of care
• Consider HDU review if significant ECG changes or risk of arrhythmia