Potassium – ProductiveMedic

Potassium

Potassium abnormality pathways

- Potassium abnormality
  - Hypokalaemia
  - Hyperkalaemia
- Important instructions and notes - please click to read.
  
  Instructions: Click the links (blue text), icons () and drop-downs (▶) for further information. Select the appropriate clinical scenario to adjust the pathway.
  
  This is an adapted version of the source material referenced/linked below. Please see the original source for full details.
  
  Please read our medical disclaimer - this pathway may not be suitable for your particular patient or healthcare setting/system.
  If you would like to commission a more appropriate localised pathway please get in touch.
  
  This pathway is adapted from Hypokalaemia in Adults: Southern Derbyshire Shared Care Pathology Guidelines
  
  [Hypokalaemia Physiology] | [Hypokalaemia Clinical Findings]
  Symptomatic or Severe Hypokalaemia
  The major risk of hypokalaemia is dysrhythmia.
  
  Hypokalaemia ⇛ Severe ≤ 2.5 mmol/L Symptomatic Hypokalaemia <div class="navybox"> <p><b><u>Clinical symptoms of hypokalaemia include:</u></b></p> <ul> <li><b>Arrythmias</b></li> <li><b>ECG changes:</b> ST depression | T wave flattening or inversion | U waves</li> <li>Digoxin sensitivity <a href="" target="_blank">[&nearr;]</a></li> <li>Muscle weakness | <b>Rhabdomyolysis</b></li> <li>Lethargy | Confusion</li> <li>Tetany: extensor muscle spasms of hands and feet</li> <li>Paraesthesia of hands and feet</li> <li>Polyuria, renal tubular dysfunction</li> </ul> </div> ECG abnormalities <div class="navybox"> <p><b><u>Hypokalaemia ECG changes</u></b></p> <ul> <li><strong>ST depression | T wave flattening or inversion | U waves</strong></li> <li><a target="_blank" href="https://litfl.com/hypokalaemia-ecg-library/">Further details and ECG examples</a></li> </ul> </div>
  
  ⇛ CONSIDER URGENT ADMISSION
  
  Have lower threshold for admission in patients on digoxin, patients with heart failure, ischaemia or left ventricular hypertrophy as any low potassium may have serious consequences.
  Clinical symptoms of hypokalaemia include:
  
  Arrythmias
  
  ECG changes: ST depression | T wave flattening or inversion | U waves
  
  Digoxin sensitivity [↗]
  
  Muscle weakness | Rhabdomyolysis
  
  Lethargy | Confusion
  
  Tetany: extensor muscle spasms of hands and feet
  
  Paraesthesia of hands and feet
  
  Polyuria, renal tubular dysfunction
  What are the likely causes in this patient?
  
  Drugs <div class="navybox"> <p><b><u>Drugs and agents that may cause hypokalaemia</u></b></p> <ul> <li>Diuretics: particularly loop and higher dose thiazides, Metolazone and Indapamide</li> <li>Mineralocorticoids</li> <li>Beta-adrenergic mimetics, caffeine, theophylline</li> <li>Insulin</li> <li>Penicillin (high doses) although note that some penicillins are formulated as potassium salts, e.g. potassium benzylpenicillin</li> <li>Drugs primarily causing hypomagnesaemia: Aminoglycosides, Cisplatin, Amphotericin B</li> <li>Verapimil, chloroquine (in overdose)</li> <li>Laxatives (abuse)</li> <li>Liquorice</li> </ul> </div> Nutritional state <div class="navybox"> <p><b><u>Consider nutritional status</u></b></p> <ul> <li>anorexia nervosa</li> <li>prolonged starvation/dysphagia</li> <li>chronic alcoholism</li> <li>vomiting or diarrhoea</li> </ul> </div> Urinary loss <div class="navybox"> <p><b><u>Urinary loss</u></b></p> <ul> <li>Hyperaldosteronism eg Conn’s syndrome (resistant hypertension) and secondary to heart or liver failure</li> <li>Cushing’s syndrome</li> </ul> </div> Ectopic ACTH <div class="navybox"> <p><b><u>Ectopic ACTH production</u></b> typically from small cell lung carcinoma, may cause rapid and profound hypokalaemia</p> </div> Hypomagnesaemia <div class="navybox"> <p><b><u>Hypomagnesaemia</u></b> - patients with moderate-severe hypomagnesaemia typically have hypokalaemia which responds poorly to treatment until magnesium is corrected (see shared care <a href="https://www.uhdb.nhs.uk/download.cfm?doc=docm93jijm4n854.pdf&ver=1195" target="_blank">hypomagnesaemia guideline</a> for information on Mg replacement)</p> </div>
  
  What action should be taken? The clinical urgency should be assessed as indicated by:
  
  Severity of hypokalaemia <div class="navybox"> <p><b><u>The severity of hypokalaemia</u></b></p> <p style="text-align:center;"><span class="yellowbutton"><b>MILD = 3.1 - 3.5 mmol/l</b></span> <span class="orangebutton">MODERATE = 2.6 - 3.0 mmol/l</span> <span class="pinkbutton">SEVERE ≤ 2.5 mmol/l</span></p> <p>These limits are for guidance only; the severity of clinical effects depends not only on the potassium level but also on whether the fall is acute or chronic. It is important to identify patients at particular risk of the effects of hypokalaemia as outlined above. Falls of up to 0.5 mmol/L may reflect normal analytical and biological variation.</p> <p>Note that pseudohypokalaemia is less common and less pronounced than pseudohyperkalaemia. Small falls of up to 0.5 mmol/L can occur during sample transit in hot weather.</p> </div> Rate of potassium change <div class="navybox"> <p><b>Assses the rate of change or extent of change if previous values available. <u>Rapid changes over days are more likely to be significant than slower changes.</u></b></p> </div> Risk factors <div class="navybox"> <p><b><u>Identify patients at particular risk from the effects of hypokalaemia</u> such as the elderly and patients with dysrhythmias or conditions predisposing to them.<br> The classification of hypokalaemia as mild, moderate or severe may not be applicable to these patients and <u>any low potassium may be significant</u></b></p> </div>
- Important instructions and notes - please click to read.
  
  Instructions: Click the links (blue text), icons () and drop-downs (▶) for further information. Select the appropriate clinical scenario to adjust the pathway.
  
  This is an adapted version of the source material referenced/linked below. Please see the original source for full details.
  
  Please read our medical disclaimer - this pathway may not be suitable for your particular patient or healthcare setting/system.
  If you would like to commission a more appropriate localised pathway please get in touch.
  
  This pathway is adapted from Hyperkalaemia in Adults: Southern Derbyshire Shared Care Pathology Guidelines
  
  [Hyperkalaemia Physiology] | [Hyperkalaemia Clinical Findings]
  Symptomatic or Severe Hyperkalaemia
  Severe hyperkalemia should be treated as a medical emergency and carries the risk of a cardiac event.
  
  Hyperkalaemia ⇛ Severe ≥ 7.0 mmol/L Symptomatic Hyperkalaemia <div class="navybox"> <p><b><u>Clinical symptoms of hyperkalaemia include:</u></b></p> <ul> <li><b>Arrythmias</b></li> <li><b>ECG changes:</b> peaked T waves | widening of QRS complex</li> <li><b>Severe: Muscle weakness | Fatigue | Paraesthesia</b></li> </ul> </div> ECG abnormalities <div class="navybox"> <p><b><u>Hyperkalaemia ECG changes</u></b></p> <ul> <li><strong>peaked T waves | widening of QRS complex</strong></li> <li><a target="_blank" href="https://litfl.com/hyperkalaemia-ecg-library/">Further details and ECG examples</a></li> </ul> </div> ⇛ URGENT ADMISSION
  
  Possible emergency: Potassium 6.0 - 6.9 mmol/L <div class="navybox"> <p><b><u>Consider emergency admission to hospital</u> <br>Base your decision on:</b></p> <ul> <li>Clinical state of patient</li> <li>Presence of Arrhythmias</li> <li>Severe muscle weakness, paralysis, fatigue, paraesthesia</li> <li>If available, ECG changes (peaked T waves, widening of QRS complex)</li> <li>Rapid fall in eGFR (> 10% within 1-2 weeks)</li> <li>Rapid increase in potassium (> 0.5 mmol/L within 1-2 weeks)</li> </ul> </div> ⇛ CONSIDER URGENT ADMISSION
  When is hyperkalemia considered a medical emergency?
  
  Potassium = 5.5 - 6.0 mmol/l Not usually an emergency Potassium = 6.1 - 6.9 mmol/l Possible emergency Potassium ≥ 7.0 mmol/l Usually an emergency
  
  These limits are for guidance only; the severity of clinical effects depends not only on the potassium level but also on whether the rise is acute or chronic.
  
  In many patients if the patient has acute kidney injury they will need admission to hospital.
  
  In mild to moderate hyperkalaemia, if previous results have been similar there may be no need for urgent admission.
  Could the result be spuriously high?
  
  Pseudohyperkalaemia (artefactually increased in vitro potassium levels while the in vivo concentration is normal) is the most common reason for an isolated raised potassium result and the following causes should be considered, especially if there is no clinical evidence of hyperkalaemia.
  
  K-EDTA contamination of the sample from an FBC tube
  
  When using the Vacutainer system ALWAYS take the U&E (Gold Top) sample first. A small amount of contamination from the FBC Tube (Lavender Top) will lead to an artefactually raised potassium result.
  
  Delayed sample separation
  
  Potassium starts to rise in un-separated samples after 6 hours storage at room temperature (15º C - 25º C), and is usually unsuitable for analysis >12 hours after venepuncture if not separated from the cells. To enable the laboratory to spot this ALWAYS provide the time and date a sample is taken.
  
  Storage at cold temperatures
  
  At low temperatures (< 8º C) the ATPase Na-K pump becomes inactive, and there is a rapid leak of potassium out of the red blood cells. Therefore NEVER refrigerate samples. Depending how samples are transported and stored this same effect can be seen on very cold days.
  
  Thrombocytosis
  
  Leakage of potassium from platelets during clotting and centrifugation can lead to falsely raised potassium results in patients with thrombocytopaenia. Please use a Lithium Heparin sample if known.
  
  Severe leucocytosis / Fragile white cells
  
  This would be a rare cause in GP samples, but when suspected suggest telephone Duty Biochemist.
  
  Haemolysis in vitro
  
  Difficult sample collection and inappropriate sample handling (e.g. shaking tube) can lead to haemolysis in vitro. (e.g. difficult specimen collection).
  What are the likely causes in this patient?
  
  In General Practice hyperkalaemia is most often associated with certain drugs and renal disease
  
  Drugs <div class="navybox"> <p><b><u>What drugs is the patient on?</u></b></p> <p>The following drugs may contribute to hyperkalaemia:</p> <ul> <li>ACE inhibitors</li> <li>Angiotensin-II receptor antagonists (‘sartans’)</li> <li>Potassium supplements</li> <li>NSAIDs</li> <li>Trimethoprim</li> <li>Heparin</li> <li>Beta-Blockers</li> </ul> <p>Where possible when requesting potassium please indicate if the patient is on any of the above medication, as this information is vitally useful for Pathology and the out of hours service when considering if further urgent action is needed for that patient.<p> </div> Decline in Renal function <div class="navybox"> <p><b><u>What is the renal function?</u></b></p> <ul> <li>In chronic kidney disease, high potassium is not usually seen until late stage 4 or 5, but it may be much higher for the same level of creatinine in acute renal failure (Acute Kidney Injury).</li> </ul> </div> Diabetic nephropathy <div class="navybox"> <p><b><u>Does the patient have diabetic nephropathy?</u></b></p> <ul> <li>Potassium is often much higher in longstanding diabetes with apparently moderate renal impairment.</li> </ul> </div>
  
  Excessive dietary intake of potassium is not normally associated with hyperkalaemia if renal function is normal as the kidneys readily excrete any excess.
  
  What action should be taken? The clinical urgency should be assessed as indicated by:
  
  Severity of hyperkalaemia <div class="navybox"> <p><b><u>The severity of hyperkalaemia</u></b></p> <ul> <li>Not usually an emergency 5.5 – 5.9 mmol/L</li> <li>Possible emergency 6.0 - 6.9 mmol/L</li> <li>Severe and usually an emergency ≥ 7.0 mmol/L</li> </ul> </div> Rate of potassium and eGFR change <div class="navybox"> <p>Assess the extent of change in serum potassium and eGFR if previous values available. <b>Significant changes are:</b></p> <ul> <li><b>0.5 mmol/L increase in potassium</b></li> <li><b>Potassium rising by > 0.5 mmol/L over 6-12 hours indicates significant risk at any absolute value</b></li> <li><b>10% decrease in eGFR</b></li> </ul> </div> Potassium > 6.0 mmol/L + typical ECG features <div class="navybox"> <p><b><u>Hyperkalaemia ECG changes</u></b></p> <ul> <li><strong>peaked T waves | widening of QRS complex</strong></li> <li><a target="_blank" href="https://litfl.com/hyperkalaemia-ecg-library/">Further details and ECG examples</a></li> </ul> </div>
- Select clinical scenario ⇒
- Select clinical scenario ⇒
- Hypokalaemia
  MILD = 3.1 - 3.5 mmol/l MODERATE = 2.6 - 3.0 mmol/l SEVERE ≤ 2.5 mmol/l
  These limits are for guidance only; the severity of clinical effects depends not only on the potassium level but also on whether the fall is acute or chronic. It is important to identify patients at particular risk of the effects of hypokalaemia as outlined above. Falls of up to 0.5 mmol/L may reflect normal analytical and biological variation.
  Note that pseudohypokalaemia is less common and less pronounced than pseudohyperkalaemia. Small falls of up to 0.5 mmol/L can occur during sample transit in hot weather.
- Hyperkalaemia
  The following advice makes the presumption that the hyperkalaemia is NOT spurious
  Potassium = 5.5 - 6.0 mmol/l Potassium = 6.1 - 6.9 mmol/l Potassium ≥ 7.0 mmol/l
  - These limits are for guidance only; the severity of clinical effects depends not only on the potassium level but also on whether the rise is acute or chronic.
  - In many patients if the patient has acute kidney injury they will need admission to hospital.
  - In mild to moderate hyperkalaemia, if previous results have been similar there may be no need for urgent admission.
- If the cause is obvious:
  - Treat any underlying cause such as diarrhoea and/or review medication
  - Consider oral potassium replacement treatment:
    
    Compare with previous result if available
    
    Values of 3.3 – 3.4 mmol/L in low risk patients may be of little clinical significance
    
    Sando K 2 tablets once a day until K > 3.5mmol/L
    
    Repeat potassium within 5 days
  If the cause is unclear:
  - Consider sending a random urine for potassium:creatinine ratio to identify renal loss. A value of > 2.5 mmol/mmol suggests renal loss in the presence of hypokalaemia. Unexplained renal loss, with or without hypertension, should prompt Endocrinology referral to investigate for rarer and complex electrolyte disorders such as Bartter’s and Liddle’s syndromes.
  - Consider referral to either the Endocrinology or Renal departments to exclude Conn’s and Cushing’s Syndrome in hypertensive patients.
- If the cause is obvious:
  - Treat any underlying cause such as diarrhoea and/or review medication
  - Consider oral potassium replacement treatment:
    
    Compare with previous result if available
    
    Repeat measurement on same or next day if inconsistent with previous result
    
    Assess clinical features and risk status, if available perform ECG
    
    Seek urgent specialist advice (eg heart failure nurse) if clinical features of hypokalaemia are present and in high risk patients
    
    Consider referral to A&E if hypokalaemia is rapidly worsening (e.g. change of >0.3 mmol/L in 2-3 days) for consideration of intravenous replacement
    
    Adjust medication to reverse falling potassium
    
    Sando K 2 tablets 2-3 times a day until K > 3.5mmol/L
    
    Regular potassium monitoring (weekly or more often depending on severity of deficiency
  If the cause is unclear:
  - Consider sending a random urine for potassium:creatinine ratio to identify renal loss. A value of > 2.5 mmol/mmol suggests renal loss in the presence of hypokalaemia. Unexplained renal loss, with or without hypertension, should prompt Endocrinology referral to investigate for rarer and complex electrolyte disorders such as Bartter’s and Liddle’s syndromes.
  - Consider referral to either the Endocrinology or Renal departments to exclude Conn’s and Cushing’s Syndrome in hypertensive patients.
- CONSIDER URGENT ADMISSION
- Potassium 5.5 – 5.9 mmol/L
  - If the patient’s eGFR has not decreased by > 10% and the rise in potassium is not recent (within 1 week) and < 0.5 mmol/L, suggest repeat potassium analysis within 1 to 2 weeks.
  - If patient is on any of the drugs <div class="navybox"> <p>The following drugs may contribute to hyperkalaemia:</p> <ul> <li>ACE inhibitors</li> <li>Angiotensin-II receptor antagonists (‘sartans’)</li> <li>Potassium supplements</li> <li>NSAIDs</li> <li>Trimethoprim</li> <li>Heparin</li> <li>Beta-Blockers</li> </ul> </div> that contribute to hyperkalaemia, consider dose and/or changing therapy.
  - In general these patients do not require emergency admission.
- Potassium 6.0 – 7.0 mmol/L
  - Any potassium result ≥ 6.1 mmol/L should be rechecked as soon as possible unless it has been previously similar.
  - Drugs <div class="navybox"> <p>The following drugs may contribute to hyperkalaemia:</p> <ul> <li>ACE inhibitors</li> <li>Angiotensin-II receptor antagonists (‘sartans’)</li> <li>Potassium supplements</li> <li>NSAIDs</li> <li>Trimethoprim</li> <li>Heparin</li> <li>Beta-Blockers</li> </ul> </div> which can raise potassium should be stopped immediately until it has been checked.
  - If available consider performing ECG.
  Consider emergency admission to hospital
  Base your decision on:
  
  Clinical state of patient
  
  Presence of Arrhythmias
  
  Severe muscle weakness, paralysis, fatigue, paraesthesia
  
  If available, ECG changes (peaked T waves, widening of QRS complex)
  
  Rapid fall in eGFR (> 10% within 1-2 weeks)
  
  Rapid increase in potassium (> 0.5 mmol/L within 1-2 weeks)
- URGENT ADMISSION
- Genuine confirmed potassium results from primary care as high as 9.5 mmol/L have been seen, so do not discount very high levels as being clinically implausible.

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