Lab case 178 – Interpretation

A 46 year old lady presents following collapse. She has compensated shock and blood tests which show:

Severe compensated metabolic alkalosis with severe hypokalaemia/ hypochloraemia, moderate hyponatraemia and elevated lactate.

All suggest chronic diuretic abuse (Frusemide/Thiazide).

ECG findings of hypokalaemia include ST segment sagging, T wave depression, and U wave – changes which get more pronounced as the K falls. Starts at K<3

  • Increased amplitude and width of the P wave
  • Prolongation of the PR interval
  • T wave flattening and inversion
  • ST depression
  • Prominent U waves (best seen in the precordial leads)
  • Apparent long QT interval due to fusion of the T and U waves (= long QU interval)

With worsening hypokalaemia…

  • Frequent supraventricular and ventricular ectopics
  • Supraventricular tachyarrhythmias: AF, atrial flutter, atrial tachycardia
  • Potential to develop life-threatening ventricular arrhythmias, e.g. VT, VF and Torsades de Pointes

Treatment priorities:

manage in resusc

Full cardiac monitoring

Prepare for unstable arrhytyhmia

Fluid and K replacement – req central access and arterial BP monitoring

ICU admission

Treat cause


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