Editing Potassium (section)

== '''Hyperkalaemia''' ==

* Much worse-tolerated than hypokalaemia - can be life-threatening
* '''Aetiology'''
** '''Trans-cellular shift''' - potassium release from cells - high urine K (>30mEq/L)
*** Acidosis - although a causal link has not been firmly established
*** Tumour lysis syndrome - appears within 7 days of cytotoxic chemotherapy - AKI, hyperkalaemia, hyperphosphataemia, hypocalcaemia, hyperuricaemia
*** Drugs - beta blockers, digitalis, succinylcholine
*** Insulin deficiency
** '''Impaired renal excretion''' - urine K < 30mEq/L
*** Drugs that inhibit RAAS - ACE inhibitors, ARBs, K+-sparing diuretics, NSAIDs, heparin, Bactrim
*** Renal failure - usually doesn't occur until eGFR<10, but can appear earlier in interstitial nephritis
*** Adrenal insufficiency - only seen in chronic adrenal insufficiency
** '''Pseudohyperkalaemia''' - present ex vivo but not in vivo. Repeat the venipuncture when suspected.
*** Mostly potassium release from traumatic haemolysis during venipuncture
*** K+ release from fist muscles during clenching
*** K+ release from clot formation in the tube in patients with severe leucocytosis (>50) or thrombocytosis (1,000)
** '''Excessive supplementation'''
*** Blood transfusion - begins to appear after 7 units
* '''Clinical manifestations'''
** Slowed impulse transmission, which can progress to heart block and bradycardic arrest
** ECG changes usually start at K=7
*** Tall, tapering T wave in V2 and V3
*** P wave amplitude decreases and PR interval lengthens
*** P waves disappear and QRS widens
*** VF/asystole
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* '''Severity'''
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* '''Approach'''
** Hyperkalaemia is actually quite tricky to treat in some post-op patients
** Assess and stabilise cardiac membrane
*** Calcium gluconate 10% in 10mL over 3 minutes; repeat after 5 minutes if necessary; effects last 30-60 minutes; opposes the cardiac depolarisation produced by hyperkalaemia
*** Use calcium chloride 10mL of 10% for circulatory shock
** Treat hyperkalaemia - both trans-cellular shift and removal of K from body
*** Reduce intake
**** Stop fluids containing K+
**** Stop supplements
**** Low-potassium diet
*** Shift intracellular
**** Insulin 10 units actrapid in 50mL of 50% dextrose over 5 minutes, with close BSL monitoring, with highest risk after 60 mins. Takes 30-60 minutes. Should decrease K by 0.6mEq/L. 
**** 10mg salbutamol neb over 30 mins, or 5mg if IHD history. Causes tachycardia as high doses are needed to do anything.
*** Increase excretion
**** Resonium 30g in 50mL of 20% sorbitol (oral - preferred) or 50g in 200mL of 20% sorbitol (retention enema). Onset at 2 hours, peak at 6 hours.
***** Don't use resonium in post-op patients or those with ileus - it can cause intestinal necrosis in rare case reports. It also takes 1-2 hours to work, and has minimal effect if just one dose.
**** Frusemide (only if normal renal function, otherwise talk to ICU)
**** Dialysis - very effective
** Identify aetiology
* '''Management'''
** Urgent repeat - do a VBG + UEC + CMP
** ECG
*** If any ECG changes, manage as per severe hyperkalaemia
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