7.20: Hyperkalaemia
- Page ID
- 60135
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Hyperkalaemia is a serum potassium (K) greater than 5.5 mmol/l.
Causes
It can occur from increased intake (oral or intravenous), inadequate excretion (including renal failure, adrenal insufficiency, potassium sparing diuretics) or from a shift of potassium from the tissues to the plasma (such as extensive tissue trauma,respiratory and metabolic acidosis or malignant hyperthermia).Acidosis increases K 0.5 mmol/l for every 0.1 increase in pH.
Clinical Signs and Symptoms
Patients may have no symptoms of hyperkalaemia. Clinical effects are seen with a rapid rise or a high level (greater than 6.5 mmol/l). If serum K rises very rapidly the first clinical effect may be ventricular fibrillation or asystole.
ECG changes usually do not occur until serum K is greater than 6.5 mmol/l. There is first, prolongation of the PR interval, followed by peaked T waves, widened QRS,decreased R wave height, loss of ST segment and loss of P wave.Patients can develop bradycardia, complete heart block, ventricular fibrillation or asystole.
Severe hyperkalaemia can cause peripheral weakness.
Management
Mild hyperkalaemia
(serum potassium less than 6.0 mmol/l)The surgery for elective patients should be delayed and the patient should be investigated for a cause of the hyperkalaemia. They should be given cation exchange resins (e.g. resonium) by rectal or oral routes.Emergency patients should be given cation exchange resins. The anesthetist should be careful with giving suxamethonium, which can cause a further rise in serum potassium. Stop any potassium containing fluids. The patient’s potassium should be monitored (blood analysis and ECG).
Moderate to severe hyperkalaemia (serum potassium greater than 6.0 mmol/l)Moderate to severe hyperkalaemia must be corrected before surgery.
Check for ECG changes or signs of peripheral weakness. If present give 5 to 10 ml of 10% Calcium chloride.
Check for acidosis (arterial blood gas). If present give 50 mmol of 8.4% sodium bicarbonate.
Give 50 ml of 50% dextrose (or 25 grams of dextrose) plus 10 units of insulin. Then give an infusion of insulin at 5 units per hour plus 10% dextrose at 100 ml/hour.(Adjust the 10% dextrose rate to maintain a blood glucose of 5 to 8 mmol/l). The serum potassium and blood glucose must be measured frequently. If an infusion pump is not available continue to give 50 ml of 50% dextrose with 10 units of insulin each hour until the serum potassium has returned to normal.
Check for renal failure. If the renal function is normal then increase the urine output by giving 20 mg of frusemide plus intravenous normal saline. If renal failure is present start resonium A 15 mg oral or 30 mg PR.