Fluids, Electrolytes & Acid-Base Medications

Vocabulary practice flashcards covering fluid compartments, tonicity, ATI laboratory reference ranges, crystalloid solutions, electrolyte replacement drugs, hyperkalemia interventions, and acid-base pharmacotherapy.

Intracellular Fluid (ICF)

The body fluid located inside the cells, which contains approximately $98\%$ of the body's total potassium.

Extracellular Fluid (ECF)

Body fluid situated outside of cells, subdivided into intravascular fluid (within blood vessels) and interstitial fluid (in tissue spaces), where the vast majority of sodium resides.

Osmolality

The concentration of dissolved solutes per kilogram of body fluid, with a standard normal serum range of $275\text{ to }295\,\text{mOsm/kg}$.

Tonicity

The relative concentration of an intravenous solution compared to blood serum, determining the osmotic gradient and direction of fluid movement across cellular membranes.

Crystalloid

An intravenous solution consisting of sterile water and dissolved electrolytes that readily passes through semipermeable membranes, such as 0.9% sodium chloride, Lactated Ringer's, or 5% dextrose in water.

Fluid Volume Deficit (FVD)

A state of hypovolemia resulting from insufficient fluid in the extracellular compartment, commonly triggered by vomiting, diarrhea, NG suction, blood loss, or diuretic overuse.

Fluid Volume Excess (FVE)

A state of hypervolemia characterized by excessive fluid retention in the extracellular compartment, presenting clinically with crackles, jugular venous distention (JVD), peripheral edema, and dyspnea.

Isotonic Crystalloids

Intravenous fluids with an effective osmolality equal to blood that expand extracellular volume without causing a net fluid shift into or out of cells, maintaining baseline cell volume.

0.9% Sodium Chloride (Normal Saline, NS)

An isotonic crystalloid prototype used to restore intravascular volume and treat mild hyponatremia; it is the only intravenous solution compatible for administration with blood products.

Lactated Ringer's (LR)

An isotonic crystalloid containing multiple electrolytes and sodium lactate; contraindicated in renal failure due to potassium content, liver disease due to inability to metabolize lactate, and incompatible with blood transfusions.

Hypotonic Crystalloids

Intravenous fluids with a solute concentration lower than plasma that drive free water from the vascular space into the intracellular space, causing cells to swell.

0.45% Sodium Chloride (1/2 Normal Saline)

A hypotonic crystalloid prototype used to rehydrate cells and correct hypernatremia; contraindicated in patients with increased intracranial pressure, burns, trauma, or hypovolemic hypotension.

5% Dextrose in Water (D5W)

A fluid that is isotonic in the intravenous infusion bag but functions as a hypotonic solution in the body once dextrose is metabolized, delivering free water to intracellular compartments.

Hypertonic Saline (3% Sodium Chloride)

A concentrated crystalloid that draws fluid from the intracellular space into the vascular compartment, reserved for severe symptomatic hyponatremia ($\text{Na} < 130\,\text{mEq/L}$) or cerebral edema and preferentially administered via a central venous catheter.

Cerebral Edema

Intracellular fluid accumulation causing brain tissue swelling, manifesting as altered mentation, headache, and seizures; an adverse consequence of rapid hypotonic fluid administration.

Infiltration

The inadvertent leakage of non-vesicant intravenous fluid or medication out of the vascular channel and into the surrounding subcutaneous tissue spaces.

Phlebitis

Inflammation of the venous wall characterized by local pain, erythema, warmth, or a palpable venous cord along the cannulated vein, often triggered by irritating infusions such as potassium chloride.

Hyponatremia

A serum sodium concentration dropping below the ATI normal reference parameter of $136\,\text{mEq/L}$.

Hypernatremia

A serum sodium concentration exceeding the ATI normal reference limit of $145\,\text{mEq/L}$, typically resulting in cellular dehydration marked by intense thirst and dry, cracked mucous membranes.

Hypokalemia

A serum potassium level falling below $3.5\,\text{mEq/L}$, which enhances myocardial irritability, triggers cardiac arrhythmias, and causes skeletal muscle weakness or cramping.

Hyperkalemia

A serum potassium level rising above $5.0\,\text{mEq/L}$, resulting in myocardial conduction depression, peaked/tented T waves, bradycardia, and risk of ventricular fibrillation or cardiac arrest.

Potassium Chloride (KCl)

The prototype potassium supplement administered orally or diluted in IV solution via an infusion pump to treat hypokalemia; it must NEVER be administered via IV push or intramuscularly.

Calcium Gluconate

A cardioprotective IV agent that antagonizes potassium-induced membrane excitability to prevent lethal dysrhythmias without lowering serum potassium levels, and serves as the primary antidote for magnesium sulfate toxicity.

Regular Insulin with Dextrose

An intravenous treatment regimen for acute hyperkalemia wherein insulin promotes rapid cellular uptake of potassium while co-administered dextrose prevents hypoglycemia.

Sodium Polystyrene Sulfonate (Kayexalate)

A cation-exchange resin administered orally or via retention enema that exchanges sodium ions for potassium ions in the intestine to promote permanent potassium excretion in the stool.

Magnesium Sulfate

The prototype parenteral mineral replacement used to treat hypomagnesemia ($\text{Mg} < 1.3\,\text{mEq/L}$), requiring continuous assessment of respiratory rate ($\ge 12/\text{min}$), urine output, and deep tendon reflexes.

Magnesium Oxide (Mag-Ox)

An oral magnesium supplement prototype utilized to correct mild, non-acute hypomagnesemia.

Deep Tendon Reflexes (DTRs)

Neuromuscular motor reflex evaluations performed during magnesium sulfate infusions; the progressive suppression or absence of DTRs is the primary early warning sign of impending magnesium toxicity.

Sodium Bicarbonate

A systemic alkalinizing agent administered orally or intravenously to buffer hydrogen ions, increase blood pH in metabolic acidosis, and facilitate the intracellular shift of potassium.

Push-Pull Rule (ABG)

The arterial blood gas interpretation model stating that $\text{PaCO}_2$ pushes the pH in the opposite numerical direction (respiratory component), whereas $\text{HCO}_3^-$ pulls the pH in the same numerical direction (metabolic component).

Respiratory Acidosis

An acid-base derangement characterized by a low arterial pH ($< 7.35$) and elevated $\text{PaCO}_2$ ($> 45\,\text{mm}\,\text{Hg}$), commonly caused by hypoventilation from central nervous system depressants like opioids or benzodiazepines.

Metabolic Alkalosis

An acid-base disturbance defined by an elevated arterial pH ($> 7.45$) and elevated $\text{HCO}_3^-$ ($> 28\,\text{mEq/L}$), frequently induced by the overuse of antacids or potassium-wasting loop and thiazide diuretics.

Metabolic Acidosis

An acid-base disturbance presenting with a low arterial pH ($< 7.35$) and low bicarbonate level ($< 21\,\text{mEq/L}$), commonly caused by diabetic ketoacidosis (DKA), kidney failure, or severe diarrhea.

Normal Serum Sodium (ATI Reference)

The standard physiological serum concentration range of $136\text{ to }145\,\text{mEq/L}$.

Normal Serum Potassium (ATI Reference)

The standard physiological serum concentration range of $3.5\text{ to }5.0\,\text{mEq/L}$.

Normal Serum Magnesium (ATI Reference)

The standard physiological serum concentration range of $1.3\text{ to }2.1\,\text{mEq/L}$.

Normal Serum Bicarbonate (ATI Reference)

The standard physiological serum concentration range of $21\text{ to }28\,\text{mEq/L}$.

Hyperkalemia Management Protocol (Four Steps)

The sequential four-step clinical intervention framework: 1. Stop potassium intake; 2. Protect the heart with calcium gluconate; 3. Shift potassium intracellularly with insulin + dextrose; 4. Remove potassium via cation-exchange resins or dialysis.