Southern Derbyshire Shared Care Pathology Guidelines. Hyperkalaemia

Transcription

1 Southern Derbyshire Shared Care Pathology Guidelines Hyperkalaemia Purpose of Guideline Dealing with adult patients with Hyperkalaemia in the community Definition Serum potassium normal range is mmol/l Importance of Hyperkalaemia Severe hyperkalemia should be treated as a medical emergency and carries the risk of a cardiac event (see below) When is hyperkalemia considered a medical emergency? Potassium mmol/l Not usually a medical emergency Potassium mmol/l Possible medical emergency Potassium 7.0 mmol/l Usually a medical 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. The laboratory usually telephones all true potassium results >6.1 mmol/l, Monday to Friday when GP practices are open. When the potassium is >6.5 mmol/l the result will usually be telephoned to Derbyshire Health United when the GP practice is closed. In cases of persistent mild hyperkalaemia subsequent raised results may not be telephoned. Dependent upon other results and recent changes, potassium values between mmol/l may also be telephoned out of hours. Authorised by Julia Forsyth Page 1 of 6

2 When is hyperkalaemia suspected? Clinical symptoms of hyperkalaemia include: Arrhythmias Muscle weakness, fatigue, parathesia ECG changes (peaked T waves, widening of QRS complex) Excessive dietary intake of potassium is not normally associated with hyperkalaemia if renal function is normal as the kidneys readily excrete any excess. In General Practice hyperkalaemia is most often associated with certain drugs and renal disease. What happens next? Step 1 Could the result could be spuriously high? Result appears genuinely raised See section 1 (Page 3) for causes of artefactually raised potassium Before reporting a result the lab checks for: EDTA contamination Delayed separation of plasma from cells In vitro haemolysis High platelets or white cell count Step 2 What are the causes of true hyperkalaemia? See section 2 (Page 4) for details Consider the following: Drug Therapy Renal Function Is patient Diabetic? Step 3 Assess the clinical urgency. Suggested action is outlined in section 3 (Page 4-5) depending on: Severity of Hyperkalaemia Clinical condition of patient Authorised by Julia Forsyth Page 2 of 6

3 1. Is it correct? 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. o 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. o 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. o 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 o 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 (Green Top) if known. Severe leucocytosis / Fragile white cells o This would be a rare cause in GP samples, but when suspected suggest telephone Duty Biochemist. Haemolysis in vitro o Difficult sample collection and inappropriate sample handling (e.g. shaking tube) can lead to haemolysis in vitro. (e.g. difficult specimen collection) Before reporting a result the lab will usually check for the possibility of contamination with EDTA, delayed separation of plasma from cells, in vitro haemolysis, high platelets or white cell count and will deal with results and give advice accordingly. Authorised by Julia Forsyth Page 3 of 6

4 2. What are the likely causes in this patient? What drugs is the patient on? The following drugs may contribute to hyperkalaemia: ACE inhibitors Angiotensin-II receptor antagonists ( sartans ) Potassium supplements Potassium sparing diuretics (spironolactone, amiloride) NSAIDs Trimethoprim Heparin Βeta-Blockers 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 Derbyshire Health United when considering if further urgent action is needed for that patient. What is the renal function? 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). Does the patient have diabetic nephropathy? Potassium is often much higher in longstanding diabetes with apparently moderate renal impairment. 3. What action should be taken? The clinical urgency should be assessed as indicated by: The severity of hyperkalaemia o Not usually an emergency mmol/l o Possible emergency mmol/l o Severe and usually an emergency 7.0 mmol/l The extent of change in serum potassium and egfr if previous values available. Significant changes are o 0.5 mmol/l increase in potassium o 10% decrease in egfr Potassium > 6.0 mmol/l and presence of typical ECG features Potassium rising by > 0.5 mmol/l over 6-12 hours indicates significant risk at any absolute value Authorised by Julia Forsyth Page 4 of 6

5 The following advice makes the presumption that the hyperkalaemia is NOT spurious. Potassium 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 listed on page 4, consider dose and/or changing therapy. In general these patients do not require emergency admission. Potassium mmol/l Any potassium result 6.1 mmol/l should be rechecked as soon as possible unless it has been previously similar. Drugs which can raise potassium (Page 4) 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, parathesia 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) Advice can be obtained from Consultant Phone Triage (10:00 to 18:00 Mon-Fri). Refer patients to MAU/ACC in the first instance (NOT to the Emergency Department unless the patient is acutely unwell - see contacts below). Potassium 7.0 mmol/l Patients with potassium 7.0 mmol/l usually require urgent admission to hospital. If available consider performing ECG. Refer patients either to MAU/ACC or the renal team if known renal disease (see contacts below). DO NOT refer to the Emergency Department unless the patient is acutely unwell. We have seen genuine confirmed potassium results from primary care as high as 9.5 mmol/l, so do not discount very high levels as being clinically implausible. Authorised by Julia Forsyth Page 5 of 6

6 Contacts Duty Biochemist (8am to 7pm, Monday-Friday) On Call Consultant Biochemist Via RDH switchboard, (24/7) Renal Registrar 9am to 9pm, via RDH switchboard bleep 8121 Consultant Phone Triage Via RDH switchboard, (10am to 6pm Mon-Fri) MAU and ACC OR MAU Nurse in Charge Authors: Mrs Helen Seddon, Maarten Taal, Dan Becker, Ben Pearson & Nigel Lawson November 2011 Reviewed by: Date: Expiry date: Dr D Becker, Dr P Blackwell, Mrs H Seddon Nov th Nov 2015 Dr D Becker, Dr P Blackwell, Mrs H Seddon Dec st Dec 2017 Dr E Mullaney, Dr P Blackwell, Mrs H Seddon Jan st Jan 2020 Authorised by Julia Forsyth Page 6 of 6