Lab case 84 – Interpretation

33 year old female with vomiting

  1. Severe uncompensated metabolic alkalosis

Severe life threatening hypokalaemia

Moderate hyponatraemia

2. Cardiac monitoring with ivi access

Correct hypokalaemia, will require central venous access

3. HDU/ICU admission for K replacement and full cardiac monitoring

K requirement: likely to be large, serum potassium may be expected to increase by ~0.25 meq/L for each 20 meq IV KCl infused.
750mg/10ml (1mmol/ml) ampoules
Add 10-20mmol KCl to 100ml of compatible IV fluid and infuse over 1 hour via a central line. Rates of up to 40mmol/hr can be used via central line for severe hypokalaemia (<2mmol/L) when cardiac abnormalities are present.

CVC access allows larger doses and reduces phlebitis and patient discomfort

Mg replacement will also be required

Cardiac arrhythmias

A variety of arrhythmias may be associated with hypokalaemia. There is considerable variability in potassium concentrations associated with the progression of ECG changes. Arrhythmias include sinus bradycardia, premature atrial and ventricular beats, paroxysmal atrial or junctional tachycardia, atrioventricular block, and ventricular tachycardia or fibrillation. Typically, there is depression of the ST segment, decrease in the amplitude of the T wave, and an increase in the amplitude of U waves (often seen in the lateral precordial leads V4 to V6).

The presence of concomitant factors, such as coronary ischaemia, digoxin use, increased beta-adrenergic activity, and magnesium depletion, can promote arrhythmias due to hypokalaemia. In addition, diuretic-induced magnesium depletion promotes arrhythmias, particularly in patients also treated with drugs that prolong the QT interval, which can predispose to torsades de pointes.Urgent potassium replacement is required.