Potassium - Hypokalaemia
Hypokalaemia is defined as a serum potassium of
Hypokalaemia generally means hypomagnesaemia, measure and replace Mg2+ as required.
Causes
Symptoms
Usually asymptomatic, but…
Weakness, lethargy, paralysis, tetany
Cardiac dysrhythmias if severe:
VT, VF, heart block, asystole
Investigations
Bloods EUC ideally via Venous Blood Gas.
ECG done early on suspicion of electrolyte abnormalities:
Normal, flattened T waves, peaked P waves
U wave.
Management
Cardiac monitoring and treatment of cause are the underlying principles. The rate of replacement and methods are highly dependent on the symptoms and signs and degree of deficit.
If mild
Oral K replacement - 40mmol in 4-6 hours with K+ tablets, SlowK and SpanK ( swallowede whole and 8mmol per tablet) Chlorvescent (dissolved, 14 mmol/L)
Slow K not as effective as effervescent immediate release and less K+
Oral is usually best but can lead to GI upset
Replacement of magnesium - 10mmols over 20 minutes which is invariably low in hypokalaemia.
If moderate to severe K 2.5- 3.0mmol/L and asymptomatic
Replace as per mild if can take oral
Consider IV replacement as for severe
If moderate to severe K
IVI Potassium Chloride ideally use preloaded infusions e.g. 30mmol/L in 1000 mLs, or 10mmol/100 mLs, usually at rates of 10-20mmols per hour
Via central or large peripheral IV line, greater than 10 mmol/hr can cause discomfort and vein damage in peripheral lines
Maximum 40mmol per hour
Cardiac monitoring whilst infusing
Concurrent oral can be used if conscious
Note: 20mmol K will raise serum K by 0.5-0.75mmol l-1, this can vary and is only a guide depending on the cause ongoing losses and state of hydration.
If severe K
10mmol as a push dose
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