Solutions, Body Fluids, and Electrolytes

Flashcards covering the definitions of solutions, types of pressure, tonicity, homeostatic fluid transport, and major serum electrolytes including sodium, chloride, bicarbonate, and potassium.

Solution

A stable mixture of two or more substances in a single phase that cannot be separated using a centrifuge.

Solute

A substance dissolved in a solution, such as sugar in coffee.

Solvent

Any liquid in which another substance can be dissolved.

Semipermeable membrane

A barrier that allows solvent molecules to pass, such as a capillary wall.

Oncotic pressure

The osmotic pressure of solutions responsible for sucking fluid into capillaries.

Hydrostatic pressure

The pressure responsible for pushing fluid out of capillaries.

Osmosis

The process by which water is distributed in the body to redistribute solvent molecules for the same concentration on both sides of a membrane.

Tonicity

A term used to describe the osmotic force exerted by a solution.

Isotonic

Solutions with tonicity similar to body solutions, such as a $0.9\%$ solution of $NaCl$ (normal saline).

Hypertonic

Solutions with a greater tonicity than $0.9\%$ $NaCl$ that draw fluids out of the cells.

Hypotonic

Solutions with less tonicity than $0.9\%$ $NaCl$ that cause water to be drawn into the cell.

Equivalent weights

Amounts of substances having equal chemical combining forces, generally stated in gram equivalent weight ($gEq$) or milliequivalent ($mEq$).

pH scale

A scale used to describe the concentration of $H^+$ in a solution.

Alkaline

A solution with a $pH > 7$, meaning it has less acid or more base than water.

Acidic

A solution with a $pH < 7$, meaning it has more acid or less base than water.

Homeostasis

A state of balance that depends on body fluids and their transport, including passive diffusion and osmotic pressure exerted by proteins like albumin ($~25\,mm\,Hg$).

Pulmonary fluid exchange

A process where alveoli must remain dry for efficient gas exchange; in pathology, hydrostatic pressures may exceed osmotic, leading to interstitial or alveolar edema often caused by left ventricular failure (CHF).

Sodium ($Na^+$)

The major extracellular electrolyte with a normal range of $135-145\,mEq/L$.

Hyponatremia

An electrolyte imbalance where serum $Na^+$ levels are $< 135\,mEq/L$, impacting cognitive function and gait stability, and potentially leading to cerebral edema.

Hypernatremia

A condition defined by high levels of sodium, most commonly associated with dehydration.

Skin Turgor

A clinical sign of hydration; decreased turgor causes skin to remain elevated after being pulled up and released.

Chloride ($Cl^-$)

The most common anion in the extracellular space with a normal range of $80-100\,mEq/L$; its serum levels typically follow changes in sodium.

Hypochloremia

A condition of low serum chloride that is associated with metabolic alkalosis.

Hyperchloremia

A condition of high serum chloride that is associated with metabolic acidosis.

Bicarbonate ($HCO_3^-$)

An anion with a normal range of $22-26\,mEq/L$ that acts as a primary method of $CO_2$ transport and is reabsorbed or eliminated by the kidneys to maintain acid-base balance.

Potassium ($K^+$)

An electrolyte where about $90\%$ of total body content is intracellular; its normal range is $3.5-4.5\,mEq/L$.

Hypokalemia

Decreased serum potassium that can result from metabolic alkalosis, renal loss, or vomiting, and may present as flattened T waves on an EKG.

Hyperkalemia

Increased serum potassium caused by kidney failure, potentially resulting in spiked T waves on double an EKG or paralysis.

Total Serum Carbon Dioxide

A major buffering system in the body representing dissolved carbon dioxide ($CO_2$) with a normal range of $23-30$; it is distinct from $PaCO_2$ found in an ABG.