Fluids, Electrolytes, and pH Management: Glossary

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A

• Acid-base balance: The regulation of hydrogen ion concentration to maintain a stable pH.
• Acidosis: A condition where blood pH falls below 7.35.
• ADH (antidiuretic hormoneADH A hormone that increases water reabsorption in the kidneys to concentrate urine and reduce water): Hormone that promotes waterThe universal solvent essential for life. reabsorptionThe process of fluid moving back into capillaries from surrounding tissues due to colloid osmotic p in the kidneys to reduce water loss.
• Aldosterone: Hormone that increases sodium(Na⁺): Major ECF cation; important for fluid balance, nerve function. reabsorption and potassium(K⁺): Major ICF cation; essential for muscle and nerve function. excretion in the kidneys.
• Alkalosis: A condition where blood pH rises above 7.45.
• Anorexia: Loss of appetite; in clinical terms, it may relate to psychological or physiological causes.

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B

• Bicarbonate buffer system: The main buffer in ECF, involving HCO₃⁻ and H₂CO₃.
• Buffer systems: Groups of chemical or physiological systems that stabilize pH.
• Buffering: The process of stabilizing pH by binding or releasing H⁺ ionsCharged atoms or molecules..
• Buffers: Substances that resist changes in pH.

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C

• Calcium (Ca²⁺): Important for bone health, muscle contraction, and nerve transmission.
• Carbonic acidA substance that releases hydrogen ions (H⁺) in solution. (H₂CO₃): Weak acid in the bicarbonate buffer systemThe main buffer in ECF, involving HCO₃⁻ and H₂CO₃. that forms from CO₂ and water.
• Chemical buffer: A substance that acts quickly to temporarily stabilize pH (e.g., bicarbonate(HCO₃⁻) – A crucial buffer in blood that helps maintain pH balance; formed when carbon dioxide).
• Compensated: When a buffer or system (respiratory or renal) has corrected pH despite ongoing imbalance.
• Cutaneous transpiration: Water that evaporates through the skinThe body’s largest organ, providing protection and regulation., not from sweat glands.

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D

• Dehydration: A condition in which fluid loss exceeds intake, leading to a decrease in total body waterAll the water in the body, about 60% of body weight in adults..

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E

• Edema: Excess fluid in interstitial spaces.
• Electrolyte balance: The maintenance of appropriate levels of ions like sodium, potassium, calcium, and magnesium(Mg²⁺): Cofactor for many enzymes; important in muscle and nerve function. in body fluids.
• Extracellular fluid (ECF): Fluid outside cellsThe basic structural and functional units of life., including plasmaThe liquid component of blood. and interstitial fluidThe fluid surrounding cells within tissues..

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F

• Fluid balance: The maintenance of proper fluid volume and distribution in the body.
• Fluid compartments: Divisions of body water: intracellular, extracellular, and transcellular.
• Fluid deficiency: A state of inadequate fluid in the body, due to either volume depletionA loss of fluid and electrolytes from the ECF, often with proportional loss of sodium and water. or dehydrationA condition in which fluid loss exceeds intake, leading to a decrease in total body water..
• Fluid excess: An abnormal increase in total body fluid.
• Fluid sequestration: Fluid accumulates in areas where it’s not easily exchanged with the rest of the ECF (e.g., edemaExcess fluid in interstitial spaces., pleural effusionFluid accumulation between the layers of the pleura around the lungs.).

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H

• Hydrogen cations (H⁺): Protons that influence pH levels in body fluids.
• Hyper-: Prefix meaning “above normal.”
• Hypercalcemia: High calcium levels in the blood.
• Hyperkalemia: High potassium levels in the blood.
• Hypernatremia: High sodium levels in the blood.
• Hypo-: Prefix meaning “below normal.”
• Hypocalcemia: Low calcium levels in the blood.
• Hypokalemia: Low potassium levels in the blood.
• Hyponatremia: Low sodium levels in the blood.
• Hypotonic hydration: Excess water intake dilutes ECF, causing water to move into cells (ICF), leading to swelling.

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I

• Insensible water loss: Water lost through evaporation from skin and respiratory tract.
• Interstitial fluid (IF): The fluid between cells in tissues.
• Intracellular fluid (ICF): Fluid inside cells, making up about two-thirds of total body water.

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L

• Limiting pH: The lowest pH at which the kidneys can still secrete H⁺ effectively (about 4.5).

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M

• Magnesium (Mg²⁺): Cofactor for many enzymesProteins that speed up chemical reactions in the body.; important in muscle and nerve function.
• Malaise: A general feeling of discomfort or uneasiness, often a nonspecific symptom of illness.
• Metabolic acidosisA condition where blood pH falls below 7.35.: Low blood pH due to excess acid or loss of bicarbonate.
• Metabolic alkalosisA condition where blood pH rises above 7.45.: High blood pH due to excess bicarbonate or loss of acid.
• Metabolic water: Water produced from cellular respirationThe process of gas exchange, including ventilation, external and internal respiration..

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N

• Nocturia: Frequent urination at night.
• Normo-: Prefix meaning “normal.”

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O

• Obligatory water loss: Minimum water loss required to eliminate waste, typically in urineThe liquid waste excreted by the kidneys..
• Osmolarity: A measure of solute concentration in fluid; affects fluid movementA fundamental property of life involving motion of the body or its parts. between compartments.
• Osmoreceptors: Hypothalamic cells that detect changes in blood osmolarityA measure of solute concentration in fluid; affects fluid movement between compartments. and help regulate thirst and ADH release.

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P

• Paresthesia: Abnormal sensation like tingling or numbness, often due to electrolyte imbalances.
• pH: A measure of hydrogen ion concentration; lower pH = more acidicA solution with a pH below 7, having a higher concentration of H⁺ ions..
• Phosphate buffer system: A buffer system active in the ICF and renal tubules.
• Physiological buffer: Slower-acting systems (respiratory or renal) that regulate pH over longer timeframes.
• Plasma: The liquid component of blood.
• Pleural effusion: Fluid accumulation between the layers of the pleuraThe double-layered membrane surrounding the lungs and lining the thoracic cavity. around the lungs.
• Polydipsia: Excessive thirst.
• Polyuria: Excessive urine output.
• Potassium (K⁺): Major ICF cation; essential for muscle and nerve function.
• Preformed water: Water from food and drink.
• Protein buffer system: Uses amino acidThe building blocks of proteins, consisting of an amino group, carboxyl group, and side chain. side chains to bind/release H⁺; important in ICF and plasma.

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R

• Renal compensation: Long-term adjustment of pH via kidney function.
• Renal control: The kidneys regulate pH by excreting H⁺ and reabsorbing bicarbonate.
• Respiratory acidosis: Low pH due to CO₂ retention (e.g., hypoventilation).
• Respiratory alkalosis: High pH due to excessive CO₂ loss (e.g., hyperventilation).
• Respiratory compensation: Adjusting breathing to correct pH imbalances caused by metabolic issues.
• Respiratory control: Regulation of pH via control of CO₂ levels by breathing rate.
• Rhabdomyolysis: Breakdown of muscle tissue releasing contents into the blood, can damage kidneys.

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S

• Sensible water loss: Noticeable water loss, such as urine and sweat.
• Signs: Objective clinical findings observable by a provider (e.g., edema, fever).
• Sodium (Na⁺): Major ECF cation; important for fluid balanceThe maintenance of proper fluid volume and distribution in the body., nerve function.
• Symptoms: Subjective experiences reported by the patient (e.g., nausea, fatigue).

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T

• Tetanus: In this context, sustained muscle contractions due to calcium or electrolyte imbalances.
• Total body water: All the water in the body, about 60% of body weight in adults.
• Transcellular fluid: Fluids separated from other ECF by membranes (e.g., cerebrospinal fluid(CSF) – A fluid that cushions and nourishes the brain and spinal cord., synovial fluid).

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U

• Uncompensated: When the body has not yet corrected a pH imbalance.

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V

• Volume depletion: A loss of fluid and electrolytes from the ECF, often with proportional loss of sodium and water.
• Volume excess: Increased fluid volume in the ECF, often with normal osmolarity.