13 Electrolytes

Overview

• hyperkalemia: wide QRS, peaked T, weakness

• hypokalemia: flat T, U wave, weakness

• hypercalcemia: stones, bones, groans, psychiatric overtones

• hypocalcemia: tetany, seizures

• hypermag: decreased DTR, paralysis, bradycardia, hypotension

• hypomag: tetany, arrhythmia, confusion

Hyperkalemia

_..

_..

• hyperkalemia: Na channels inactivated, slowing depolarization

Reversal potential of K is shifted positive. Driving force for K to leave the cell via Leak K channels is decreased so there is less "leak" K current and the RMP is depolarized compared to normal. The more positive RMP means more Na channels will randomly open and more of them will become inactivated. This means fewer Na channels are available to respond by opening when full depolarization occurs.

_..

• insulin deficient, beta blockers, digoxin: Na/K pump

• insulin and catecholamines stimulates pump (insulin deficient and bb increase K)

• hyperosmolarity: uncontrolled hyperglycemia

• Banana peels: beta-2 activation can cause hypokalemia (due to increased insulin activity)

• rhabdomyolysis: lysis of cells, hyperkalemia

• hyperosmolar state: draw water out of cell, take K with it, create high K gradient in cell that leaves

Hypokalemia

_..

_..

Hypercalcemia

_..

• promotes water loss and nausea: dehydrated

_..

• mets to bones increase turnover

Hypocalcemia

_..

_..

Hyperphosphatemia

_..

• metastatic calcification: end stage renal pts with high phosphate

_..

• phosphate laxatives: bowel prep for GI exam

Hypophosphatemia

_..

_..

• ammonia binds phosphate

• tumor: inhibit transporter in PCT, don't resorb phosphate

Hypermagnesemia

_..

_..

• important cause

Hypomagnesemia

_..

• drags K and Ca with it

_..