Overview/Classification #
Potassium level (mmol/L) | |
Normal Range (1) | 3.5 – 5.0 mmol/L |
Mild hypokalaemia | 3.0 – 3.4 mmol/L |
Moderate hypokalaemia | 2.5 – 2.9 mmol/L |
Severe hypokalaemia | <2.5 mmol/L |
- Key points:
- The management options for treating hypokalaemia depend on the severity of the K+ level (oral vs. IV K+ supplementation)
- The most concerning complication associated with low levels of potassium is cardiac (must get an ECG!)$
Triage #
Triage category depends on the severity of the serum K+ levels
- Mild to moderate – within hours
- Severe – emergency requiring immediate attention
Causes #
- Increased loss (2)
- GIT losses – vomiting, diarrhoea, drain tube output
- Renal losses- diuretics, hypomagnesaemia, renal tubular acidosis, tubulopathies
- Medications (3)
- Diuretics (e.g. frusemide, thiazides)
- Beta-agonists (e.g. salbutamol)
- Corticosteroids
- Theophylline
- Aminoglycosides
- Increased entry of K+ into cells (2)
- Alkalosis
- Increased insulin availability
- Increased beta-adreneregic activity (e.g. stress)
- Hypothermia
- Refeeding syndrome
- Others (2)
- Reduced intake (rare on its own)
- Sweat losses
- Dialysis (esp. Peritoneal)
Clinical features #
Signs and symptoms can often be very vague and non-specific (4)
Signs and symptoms | |
Mild | Usually asymptomatic Arrhythmias Muscle weakness and crampingConstipation Nausea Fatigue |
Moderate | As above but more obvious/severeMuscle necrosisArrhythmias (especially in patients with underlying cardiac problems) |
Severe | Cardiac arrhythmias Paralysis of lower limbs and respiratory muscles Ileus Acute renal failure |
Investigations #
Initial investigations
Investigation | Significance |
VBG | Metabolic alkalosis |
UEC | Serum K+ |
CMP | Hypomagnaesaemia may preclude low levels of K+ (5) |
Further investigations
Investigation | Indication |
ECG | Typically seen with moderate/severe cases of hypokalaemia. For examples of ECG changes refer to; https://litfl.com/hypokalaemia-ecg-library/ {hyperlink to website} (6). ECG changes can be highly variable and may include:Decrease in T wave amplitude (often the earliest sign)Ventricular arrhythmias Prolonged QT ST depression T wave flattening/inversionU-waves |
Urine potassium | If suspecting urinary losses |
Management – Mild hypokalaemia (3.0 – 3.4 mmol/L) #
Consider oral supplementation (7,8):Potassium Chloride Slow Release (Slow K+) (8mmol/L) orPotassium Chloride Effervescent (Chlorvescent) (14 mmol/L) |
- Suggested dose: stat dose of either oral supplementation as listed above
- {{Tip: With a mild hypokalaemia, the exact amount of oral supplementation that you order does not matter so much as ensuring that you have an appropriate follow up plan. This includes: ordering bloods for the next day to check the K+ level and reviewing medications that may cause K+ losses}}
- Chlorvescent is more effective than Slow K+ (but tastes worse!)
- {{Beware oral K+ tablets can cause GI upset}} (9)
- Discuss with senior clinician regarding the need to withhold or reduce the dose of other drugs that may lower K+ levels (as listed above)
- Consider replacing Mg if low
- Recheck UEC in the morning, or sooner if clinically indicated
- Consider causes and work up appropriately as this may impact ongoing potassium prescription
Management – Moderate hypokalaemia (2.5 – 2.9 mmol/L) #
Requires IV replacement (8): 10 mol KCl in 100 mmol NaCl 0.29% (“minibag”) over 1/24or30 mmol KCl in 1L of NaCl 0.9% over 6/24 |
- Suggested dose: 3 sachets Chlorvescent + 3 x KCl “minibag” + consider adding regular
- Maximum rate of IV KCl infusion <10mmol per hour via peripheral line on the ward
- {{Beware that KCl infusions can cause irritation to peripheral veins}}
- {{Tip: can add lignocaine 20mg (ie 2ml of 1% Lignocaine HCl) to KCl minibag for peripheral administration to reduce irritation (10). But check with hospital protocols and consult with senior clinician before commencing}}
- Recheck plasma levels 4 hours post commencing treatment (11)
- Consider replacing Mg if low
Management – Severe hypokalaemia (<2.5 mmol/L) #
- $Potentially life-threatening!$
- Requires immediate potassium replacement (8) (suggested dose see previous section in Management – Moderate Hypokalaemia {hyperlink to other section})
- Get senior clinician help – #may require ICU admission (for faster administration of KCl, continuous ECG monitoring and serial monitoring of K+ levels)
- May need to use a central venous line if available as high concentrations of K+ can be sclerosing to peripheral veins (9)
- If intractable severe hypokalaemia, consider giving #MgSO4 as well as KCl (8)
References #
1. Lederer E. Hypokalaemia: Medscape; 2021 [Available from:
2. Mount DB. Causes of hypokalemia in adults: UpToDate; 2021 [Available from: https://www.uptodate.com/contents/causes-of-hypokalemia-in-adults?topicRef=2297&source=see_link.
3. Veltri KT, Mason C. Medication-induced hypokalemia. Pharmacy and Therapeutics. 2015;40(3):185-90.
4. Management of Hypokalaemia: Clinical Guideline: Royal Cornwall Hospitals; 2019 [Available from: https://doclibrary-rcht.cornwall.nhs.uk/DocumentsLibrary/RoyalCornwallHospitalsTrust/Clinical/Pharmacy/ManagementOfHypokalaemiaClinicalGuideline.pdf.
5. Huang C-L, Kuo E. Mechanism of Hypokalemia in Magnesium Deficiency. Journal of the American Society of Nephrology. 2007;18(10):2649.
6. Buttner R, Burns E. Hypokalaemia: Life in the fast lane; 2021 [Available from: https://litfl.com/hypokalaemia-ecg-library/.
7. Herd S. Potassium Guidelines (Adult) Royal Hobart Hospital 2003 [Available from: https://www.safetyandquality.gov.au/sites/default/files/migrated/tools_royalhobart.pdf.
8. Marshall S, Ruedy J. On Call: Principles and Protocols (3rd Edition). In: Brown AF, Cadogan M, Celenza A, editors. On Call: Principles and Protocols. Pennsylvania W.B. Saunders & Company
9. Potassium chloride: drug information (Lexicomp): UpToDate; 2022 [Available from: https://www.uptodate.com/contents/potassium-chloride-drug-information?search=potassium%20supplementation&source=search_result&selectedTitle=2~150&usage_type=default&display_rank=2.
10. Policy for administration of intravenous potassium chloride (KCL): The Alfred Hospital; 2003 [Available from: https://www.safetyandquality.gov.au/sites/default/files/migrated/tools_alfred.pdf.
11. Queensland Government – Prescribing Guidelines for HYPO-Electrolyte Disturbances in Adults; 2020 [Available from: https://www.health.qld.gov.au/__data/assets/pdf_file/0027/1006587/electrolyte-prescribe-gline-adult.pdf.
Contributors
Reviewing Consultant/Senior Registrar
Dr Michelle Truong
Dr Adam Steinberg