Hypokalemia: Physiology

Hypokalemia: Physiology Abbreviations: Note:
A: Aldosterone
ARR: Aldosterone Renin Ratio
CAH: Congenital Adrenal Hyperplasia CCD: Cortical Collecting Duct
EABV: Effective Arterial Blood Volume H+: Hydrogen ion
K+: Potassium ion
Na+: Sodium ion
NHE1: Na+/H+ antiporter 1
R: Renin
RAAS: Renin Angiotensin System TTKG: Transtubular Potassium Gradient
RMP: Resting membrane potential
• TTKG > 4 with N/↑ EABV in hypokalemia is inappropriate and a principal cell problem.
• ↓ plasma [Mg+] should be corrected for in hypokalemia.
• Hypoaldosteronism from hypovolemia does not usually cause hypokalemia because it is usually counterbalanced by ↓ distal nephron flow.
↑ Loss Renal
GI (vomit, diarrhea)
↓ Intake
↑ Intracellular Shift
Diuretics
↓ EABV
RAAS activation
Renin secreting tumour; renal artery stenosis
↑ A: ↑ R
TTKG > 4
A- secreting adenoma
↑ A: ↓ R
Steroids; CAH; black licorice
↓ A: ↓ R
ARR
TTKG < 4 Primary Polydipsia Polyuria ↑ RBC production Refeeding syndrome β2 stimulation Aldosterone ↑ Na+/K+ ATPase activity ↑ K+ into cell Serum [K+] < 3.5 mmol/L ↑ pH Insulin ↑ NHE1 activity ↑ aldosterone ↑ distal Na+ delivery (-) transepithelial potential difference ↓ K+ availability ↑ CCD K+ secretion Altered RMP ECG: flat T waves, ST depression, U waves, ↓ QT interval ↑ K+ excretion ↑ K+ loss ↑ K+ uptake by new cells Flaccid muscle weakness, fatigue, Authors: Mannat Dhillon Reviewers: Andrea Kuczynski Emily Ryznar Kevin McLaughlin* * MD at time of publication constipation, syncope, palpitations Hypertension, irregular heart rate, ↓ bowel sounds, ↓ deep tendon reflexes Hypokalemia Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published March 6, 2019 on www.thecalgaryguide.com