Hyperkalaemia

Introduction

Hyperkalaemia is a life threatening emergency and is one of the reversible causes of cardiac arrest.

It is usually secondary to renal failure or drugs (e.g. ACEi, K Sparing diuretics). Other causes include metabolic acidosis, rhabdomyolysis, burns, Addison’s and catabolic states e.g. sepsis, polytrauma. Pseudohyperkalaemia can occur when a blood sample haemolyzes prior to being processed.

It can be graded as mild (5.5 – 6), moderate (6-7) or severe (> 7). Severity and presence of ECG changes determine how it is treated

Clinical Features

Symptoms

Usually asymptomatic
Lethargy, muscle weakness, flacid paralysis, parasthesia

Signs

Arrhythmias causing cardiac arrest suddenly and without warning
Signs of underlying cause
- Renal Failure, Fluid overload, Dehydration, Sepsis

Clinical Investigations

Bedside

VBG
Elevated Potassium level. Concurrent low pH could indicate possible renal failure causing metabolic acidosis, sepsis, hypoperfusion.
Low threshold to repeat VBG if difficult sample to obtain as haemolysis may cause pseudo hyperkalaemia
ECG Changes are characteristic and indicate severity
*6-7 mmol = Tall Peake T waves (>5mm)*
*7-8mmol = Widening QRS, Small P waves*
*8-9mmol = Fusion of QRS with T wave =* *Sine Wave* *(opposite)*
o *> 9 mmol = AV dissociation, VT, V Fib, Asystole*

blood bottles.jpg — Laboratory

U&E
Assess renal function. Confirm Hyper K on VBG
FBC, CRP, LFTs, blood culture if ? Sepsis
MSU

Radiology

CXR
if concerned about fluid overload or chest sepsis
Renal US
if first presentation renal failure to assess for cause

Management & Disposition

Initial Resuscitation

Patients with ECG changes should be placed on cardiac monitor
If concerned for severe hyperkalaemia patient should be managed in resus
Address ABC as clinically indicated
In the event of cardiac arrest follow hyperkalaemia ACLS algorithm

Specific Treatment (in order of priority)

Inhibit cardiac toxicity effects of Potassium if ECG changes
- 10 mg IV Calcium Gluconate 10 % (stabilises the myocardium)
- May be repeated. Works in minutes. Effect is temporary
- Doesn’t lower potassium level
Shift Potassium into Cells
- 10 units IV soluble insulin (Actrapid) in 50ml Glucose 50%
  - Insulin causes potassium translocation. Glucose prevents associated hypoglycaemia
- Nebulized Salbutamol
- IV NaHCO3 infusion if concurrent severe acidosis or cardiac arrest
Enhance Potassium Secretion
- Furosemide diuresis if fluid overloaded
- Dialysis in those patients with ESRF
Seek and treat cause of hyperkalaemia
- E.g. stop offending drugs, treat dehydration, sepsis etc

Disposition

Patients who have missed dialysis should be immediately discussed with the renal team and have dialysis arranged as a matter of urgency
Patient’s with hyperkalaemia requiring treatment i.e. > 6mmol should be admitted to hospital for treatment of hyperkalaemia and subsequent K monitoring and for work up and treatment of underlying cause