Hypokalaemia

Severe <2.5

Low intake
Diet, IVI
GI loss
D+V, fistula, ileus, obstruction
Urine loss
Defective proximal reabsorption
  • recovery ATN
  • post relief obstruction
  • prox RTA
  • drug tubule damage
↑ urine flow rate + distal Na delivery
  • diuretics
  • DM (osmotic diuresis)
↑ aldosterone
  • Conns
  • RAS activation
    • steroids/Cushings
    • cirrhosis
    • liqourice
    • ↑↑ BP
Aminoglycosides and penicillins

K into cells
alkalosis
B agonists
insulin

Effects
ECG
T-wave flattening
Prominent U wave
ST depression
Prolonged PR
Arrhythmias, ↓ contractility
Weakness

Rx
Maximum conc for peripheral is 40mmol/L (venous necrosis)
Maximum rate is 40mmol/h
0.3 mmol ↓ equates to about 100mmol total loss from body store

Anaesthesia
Risk is of arrhythmia
Cancel elective <3 (if chronically low and un-digitalised unlikely to get problems)
Emergency – treat 1st
↑ sensitivity to neuromuscular blockade
If digitalised should be >4

Hyperkalaemia

↑ intake
Cell death
Rhabdomyolysis
Haemolysis
Internal bleeding
Tissue necrosis
Burns
Shift out of cells
Acidosis
B blockers
Dig toxicity
Impaired excretion
Low GFR (ARF/CRF)
↓ aldosterone → ↓ tubular excretion
  • ACEi
  • NSAIDS (block PG mediated renin release)
  • adrenal disease
  • heparin
  • ß blockers (symp stims renin release)
  • k sparing diuretics
  • tubular disorders
Effects
ECG changes progressing through
Peaked T-waves, widened QRS, prolonged PR, loss of P, ST depression, VF, asystole. These potentiated by ↓ Ca, Na and acidosis
N + V + D

Rx
>6.5
If ECG changes Ca to stabilise myocardium - 10ml 10% calcium gluconate or 5 mls 10% calcium chloride
Insulin 10u in 50mls 50% dex
ß2 agonist (salbutamol)
Bicarbonate (50mmol)
Ion exchange resin – calcium resonium 15g PO or 30g PR TDS

Anaesthetic
This is the most dangerous electrolyte abnormality
Cancel elective
Emergency – treat 1st
Avoid sux