Potassium Flashcards
What is a normal intracellular potassium cc?
140 mEq/L
What are the body’s protective mechanisms to prevent hyperkalemia?
increased ECF K+ –> aldosterone secretion –> increased basolateral collecting duct principal cell NaKATPase acitvitiy –> more K excretion
kaliuretic feeforward control
* K-sensing cells in stomach and hepatic portal circulation
* high K intake –> signals to kidneys to increase K secretion independent of aldosterone
List differentials for disorders of internal balance leading to hypokalemia
- alkalosis
- insulin administration
- increased catecholamine levels
- beta-adrenergic agonist therapy or intoxication
- refeeding syndrome
List differentials for external balance disorders leading to hypokalemia
- pyloric outflow obstruction
- severe diarrhea
- prolonged inadequate intake
- Renal tubular acidosis
- renal loss (e.g., CKD)
- hyperaldosteronism
- glucocorticoid administration
- diuretic therapy
- osmotic or postobstructive diuresis
- inadequate fluid supplementation in hospital
- DKA
What are the consequences of hypokalemia?
- decreased glucose tolerance - hypokalemia causes decrease pancreatic beta-cell insulin release
- hyperpolarization of myocytes from lowered resting membrane potential
- rhabdomyolysis -> pigmenturia can damage kidneys
- hyperpolarization of cardiac myocytes -> arrhythmias
What are expected ECG changes from hypokalemia?
- ventricular tachycardias, Vtach or Vfib
- atrioventricular dissociation
- ST segment depression
- QT and PR prolongation
- Increased P wave
- widened QRS
Why can hypokalemia-induced ventricular tachycardias be more difficult to treat?
hypokalemia causes myocardium to become refractory to effects of class I antiarrhythmics
What is the recommended treatment for the apneic hypokalemic patient?
rapid infusion of 0.01 mL/kg KCl (2 mEq/mL)
What is a “safe” potassium serum cc to reach before starting Nabicarbonate or insulin administration?
3.5 mEq/L
What coexisitng conditions may worsen hypokalemic neuromuscular dysfunction and make patients more refractory to supplementation?
- hypomagnesemia
- hypocalcemia
- alkalosis
List differentials for hyperkalemia
- oliguric/anuric AKI
- Urinary obstruction
- uroabdomen
- reperfusion injuries (PCA, extremity reperfusion after ATE
- tumor lysis syndrome
- insulin deficiency (DKA, DM)
- mineral acidosis
- hypoadrenocorticism
- GI disease
- Chylothorax, pleural or peritoneal effusion managed with intermittent or continual drainage
- expired RBC transfusion
- oversupplementation
Why does only mineral acidosis but not organic acidosis lead to hyperkalemia?
organic acids (e.g., lactate, ketoacids) can maintain electroneutrality
What are causes for pseudohyperkalemia?
- high WBC (>100k) or PLT (>1million) counts
- Akitas - increased RBC IC K+ cc
