Potassium and Calcium Management

Potassium

The ratio of potassium(K⁺): Major ICF cation; essential for muscle and nerve function. in the ICF to the ECF is an important regulator of membrane potentials. Potassium is needed to repolarize the cell and to create IPSPs. If we have too much potassium in the IF, depolarizationThe loss of electrical charge across a membrane, triggering an action potential. will happen too often. With too little potassium in the IF, we get hyperpolarizationAn increase in membrane potential, making the inside of the neuron more negative.. Cardiac muscle is particularly sensitive to hyperkalemiaHigh potassium levels in the blood. with the plateau phase of their action potentials.

The other problem is that potassium is also a regulator of pH in both the ICF and in the IF. We expect to have a high amount of potassium cation in the ICF and that’s OK. However, when concentrations are abnormal, either high or low, potassium cations are exchanged for hydrogen cations(H⁺): Protons that influence pH levels in body fluids.. This exchange creates acidosisA condition where blood pH falls below 7.35. in either the ICF or the IF.

Your kidney prefers to secrete potassium and actually has a hard time trying to save it. This is why potassium is important in your diet. Potassium regulation is tied tightly to sodium(Na⁺): Major ECF cation; important for fluid balance, nerve function. regulation via aldosteroneA hormone that increases sodium and water reabsorption in the kidneys, helping regulate blood pressu. Aldosterone causes the kidney to secrete potassium, trading it for sodium via Na/K pumps in the DCT.

Hypokalemia & Hyperkalemia

Hyperkalemia occurs when blood potassium (K⁺) levels are too high, typically above 5.0 mEq/L.

A common cause is kidney failure. The kidneys normally excrete excess potassium. If they’re not working properly, potassium builds up in the blood. Another cause is crushing injuries—when large numbers of cellsThe basic structural and functional units of life. are damaged, potassium leaks out into the extracellular fluid(ECF) Fluid outside cells, including plasma and interstitial fluid..

Opposite from sodium, excess potassium causes muscle weakness. With too much potassium in the IF, potassium can’t flow out of a neuron in repolarizationThe return of membrane potential to a negative value after depolarization.. This is a serious issue for the cardiac muscle fibers of the heart. They aim to create that plateau in their action potentialA rapid, temporary electrical charge that travels along neurons, allowing signal transmission.. Hyperkalemia makes it possible for the heart to go into tetany or sustained contractions.

Some potential solutions to hyperkalemia is calcium gluconate to stabilize the heart. Insulin and glucoseA simple sugar that is the main source of energy for cells. to push potassium into cells.
Hypokalemia is when blood potassium levels are too low, typically below 3.5 mEq/L. One common cause is excessive vomiting or diarrhea, which leads to potassium loss. It can also occur with overuse of diuretics (especially loop diuretics like furosemide). Muscle weakness or cramps. Oral or IV potassium replacement, depending on severity

Hypocalcemia & Hypercalcemia

Calcium is present in your plasmaThe liquid component of blood. as the cation. However, it is mainly stored as calcium phosphate salts in your bones. Recall from the endocrine section A cut or slice of the body or an organ for study. that calcium in the plasma is regulated by PTH. PTH is the parathyroid hormone(PTH): Raises blood calcium by stimulating bone resorption. that increases calcium in the plasma. Calcitonin is the hormone that decreases calcium in the plasma.

Hypocalcemia increases the excitabilityA neuron’s ability to respond to stimuli by generating an electrical signal. of muscle cells while hypercalcemiaExcess calcium in the blood, leading to nervous and muscular dysfunction. does the opposite and inhibits muscle cells and neuronsThe functional cells of the nervous system that transmit signals..

A classic cause is hyperparathyroidism—overactive parathyroid glands release too much parathyroid hormone (PTH), which increases calcium levels. Some cancers can also release PTH-like substances with the same effect. “Bones, stones, groans, and psychiatric overtones”: Bone pain Kidney stones Abdominal discomfort or constipation Confusion or depression. IV fluids and diuretics to flush out calcium
Bisphosphonates to slow bone breakdown

A common cause is hypoparathyroidism, often after thyroid or parathyroid surgery. It can also result from vitamin D deficiency, which is needed for calcium absorption. Positive Chvostek’s sign (facial twitch when cheek is tapped). Positive Trousseau’s sign (carpal spasm when BP cuff inflated). Calcium supplements (oral or IV)
Vitamin D supplementation