Management of Hypokalaemia (plasma K⁺ <3.5mmol/L)

Drug therapy / treatment options

General notes

• Oral potassium chloride is the treatment of choice for most patients. Effervescent tablets (Sando-K^®), each contain 12mmol of potassium and 8mmol of chloride.

• The dosage and duration of treatment depends on existing potassium deficit and whether there is continuing potassium loss.

• Larger doses may be required especially in patients with digitoxicity or diabetic ketoacidosis. Advice is available from the Biochemistry Department.

• Caution should be used in patients with eGFR <30ml/min, or when Angiotensin-Converting Enzyme (ACE) inhibitors / potassium-sparing diuretics are being administered concomitantly. The use of IV potassium should be discussed with the Renal Team if eGFR <15ml/min.

Suggested starting doses (but see notes above before prescribing)

Oral potassium supplementation

• For plasma K⁺ 3-3.5mmol/L (approximate potassium deficit 200mmol): Sando-K^® 2 tablets 3 times daily
  • Monitor plasma K⁺ twice weekly until stable.
  • Once plasma K⁺ stable or if plasma K⁺ >4.5mmol/L, reassess requirement for supplementation.
• Plasma K⁺ 2.5-2.9mmol/L (approximate potassium deficit 200-400mmol): Sando-K^® 3 tablets 3 times daily
  • Monitor plasma K⁺ daily until plasma K⁺ >2.9mmol/L and then manage as above.
• Plasma K⁺ <2.5mmol/L or cardiac arrhythmia (approximate deficit >400mmol): Intravenous supplementation is usually required.

Intravenous potassium supplementation

• Intravenous supplements are indicated if patients cannot eat, are unlikely to absorb oral potassium or have profound hypokalaemia.
• Plasma K⁺ 2.5-3.5mmol/L (and IV required). Recommended dose 80-120mmol/24hrs. If patient on IV fluids, subtract amount of potassium prescribed in routine maintenance fluid (24hrs) from 120mmol/L and give remaining as separate infusion(s).
• Plasma K⁺<2.5mmol/L. Recommended dose is 2-3mmol/kg/24hrs up to a maximum of 200mmol/24hrs. If patient on IV fluids, subtract amount of potassium prescribed in routine maintenance fluid (24hrs) from dose required for severe potassium depletion and give remaining amount as separate infusion(s). All patients in this category must have ECG monitoring.
• Where possible use pre-prepared infusion bags. These are available as:
  • KCl 10mmol in 500ml (0.15%w/v) sodium chloride 0.9% or glucose 5%
  • KCl 20mmol in 500ml (0.3%w/v) sodium chloride 0.9% or glucose 5%
  • KCl 20mmol in 1000ml (0.15%w/v) sodium chloride 0.9% or glucose 5%
  • KCl 40mmol in 1000ml (0.3%w/v) sodium chloride 0.18%/glucose 4%
• Recommended rate of infusion: 10mmol/hour.
• Maximum rate of infusion 20mmol/hour. The maximum rate applies to the total amount of potassium administered in both potassium replacement fluids and IV maintenance fluids (where applicable).
• Extravasation may cause tissue damage due to high osmolarity and low pH. If possible, avoid peripheral administration of concentrations >40mmol/L (0.3%w/v). Concentrations >40mmol/L should be administered via a central access device using an infusion pump. If peripheral administration is unavoidable, ensure into large proximal veins only and monitor administration site closely.
• Ready prepared infusion of KCl 40mmol in 500ml (0.6%w/v) sodium chloride 0.9% or glucose 5% (unlicensed) is available in designated critical care areas^# (available for borrowing by other wards only in exceptional circumstances e.g. fluid restriction or clinical risk of arrhythmia).
• Where it is not possible to use a ready prepared infusion fluid e.g. where a different concentration of infusion is required, then designated critical care areas^# may use KCl concentrate injection 20mmols in 10ml (15%) to prepare the infusion. Sodium chloride 0.9% is the preferred diluent for initial potassium replacement as glucose may lower serum potassium levels further. Ensure the infusion is thoroughly mixed before administration.

^# See NHS Ayrshire & Arran's Code of Practice for Medicines Governance Section 1(h) – Policy for the Safe Storage and Supply of Potassium Chloride injection/infusion (link only active if accessing via NHS network) on AthenA for further information regarding these preparations and designated critical care areas.