Fluid and Electrolytes BasicsFluid and Electrolytes Basics

Peggy D. JohndrowPeggy D. Johndrow20092009

Fluid CompartmentsFluid Compartments Intracellular fluid (ICF)Intracellular fluid (ICF) Extracellular fluid (ECF)Extracellular fluid (ECF)

– Intravascular (plasma)Intravascular (plasma)– InterstitialInterstitial

TranscellularTranscellular– Cerebrospinal fluidCerebrospinal fluid– Gastrointestinal (GI) tractGastrointestinal (GI) tract– Pleural spacesPleural spaces– Synovial spacesSynovial spaces– Peritoneal fluid spacesPeritoneal fluid spaces

Fluid and Electrolyte MovementFluid and Electrolyte Movement

DiffusionDiffusion Facilitated DiffusionFacilitated Diffusion Active TransportActive Transport OsmosisOsmosis

– Measurement of OsmolalityMeasurement of Osmolality– Osmotic Movement of FluidsOsmotic Movement of Fluids

Hydrostatic PressureHydrostatic Pressure Oncotic PressureOncotic Pressure

FiltrationFiltration

Blood pressure - hydrostatic filtering force Blood pressure - hydrostatic filtering force Difference between hydrostatic pressure of Difference between hydrostatic pressure of

capillary bed and interstitial determines capillary bed and interstitial determines whether fluid leaves the blood vessels and whether fluid leaves the blood vessels and enters the tissue spaces (interstitial fluid) enters the tissue spaces (interstitial fluid)

DiffusionDiffusion

Diffusion - free movement of most Diffusion - free movement of most electrolytes, atoms, and molecules through electrolytes, atoms, and molecules through cell membranes (selective and cell membranes (selective and impermeable)impermeable)

Movement of molecules from an area of Movement of molecules from an area of high concentration to low concentration; high concentration to low concentration; occurs in liquids, solids, and gasesoccurs in liquids, solids, and gases

Membrane separating two areas must be Membrane separating two areas must be permeable to substance for diffusion to permeable to substance for diffusion to occuroccur

DiffusionDiffusion

Facilitated DiffusionFacilitated Diffusion

Very similar to diffusion Specific carrier molecules involved to

accelerate diffusion Glucose cannot cross the cell membrane Glucose cannot cross the cell membrane

without insulinwithout insulin

OsmosisOsmosis

Osmosis and filtration act together in Osmosis and filtration act together in capillary fluid dynamics to control capillary fluid dynamics to control extracellular fluid (ECF) and intracellular extracellular fluid (ECF) and intracellular fluid (ICF) volumesfluid (ICF) volumes

Thirst mechanism - example of how Thirst mechanism - example of how osmosis helps maintain homeostasisosmosis helps maintain homeostasis

Active TransportActive Transport

Cells use active transport to control cell Cells use active transport to control cell volume and intracellular concentrations of volume and intracellular concentrations of many substancesmany substances

Process in which molecules move against Process in which molecules move against concentration gradientconcentration gradient

Example: sodium-potassium pumpExample: sodium-potassium pump ATP is energy sourceATP is energy source

Sodium-Potassium PumpSodium-Potassium Pump

Fluid Movement in CapillariesFluid Movement in Capillaries

Fluid ShiftsFluid Shifts– Shifts of Plasma to Interstitial FluidShifts of Plasma to Interstitial Fluid

Elevation of venous hydrostatic pressureElevation of venous hydrostatic pressure Decrease in plasma oncotic pressureDecrease in plasma oncotic pressure Elevation of interstitial oncotic pressureElevation of interstitial oncotic pressure

– Shifts of Interstitial Fluid to PlasmaShifts of Interstitial Fluid to Plasma

Regulation of Water BalanceRegulation of Water Balance

Hypothalamic RegulationHypothalamic Regulation Pituitary RegulationPituitary Regulation Adrenal Cortical RegulationAdrenal Cortical Regulation Renal RegulationRenal Regulation Cardiac RegulationCardiac Regulation Gastrointestinal RegulationGastrointestinal Regulation Insensible Water LossInsensible Water Loss

Sodium (Na)Sodium (Na)

Normal plasma sodium level 136 - 145 Normal plasma sodium level 136 - 145 mEq/LmEq/L

Sodium - major cation in extracellular fluid; Sodium - major cation in extracellular fluid; responsible for maintaining extracellular fluid responsible for maintaining extracellular fluid (ECF) osmolarity; responsible for skeletal (ECF) osmolarity; responsible for skeletal muscle and cardiac contraction, nerve muscle and cardiac contraction, nerve impulse transmission, normal extracellular impulse transmission, normal extracellular fluid osmolarity and normal extracellular fluid osmolarity and normal extracellular volumevolume

Calcium (Ca++)Calcium (Ca++)

Calcium levels 9.0 - 10.5 mg/dLCalcium levels 9.0 - 10.5 mg/dL Calcium: important in maintenance of bone Calcium: important in maintenance of bone

strength and density, activation of enzymes strength and density, activation of enzymes or reactions, skeletal and cardiac muscle or reactions, skeletal and cardiac muscle contraction, nerve impulse transmission, contraction, nerve impulse transmission, and blood clottingand blood clotting

Phosphorous (P)Phosphorous (P)

Phosphorous plasma levels 3.0 - 4.5 mg/dLPhosphorous plasma levels 3.0 - 4.5 mg/dL Phosphorous function: activating B-complex Phosphorous function: activating B-complex

vitamins, forming and activating ATP, vitamins, forming and activating ATP, assisting in cell division, and cooperating in assisting in cell division, and cooperating in CHO, protein, and lipid metabolismCHO, protein, and lipid metabolism

Phosphorous balance and calcium balance Phosphorous balance and calcium balance inverse proportioninverse proportion

Magnesium (Mg2+)Magnesium (Mg2+) Free magnesium plasma levels 1.3 - 2.1 Free magnesium plasma levels 1.3 - 2.1

mg/dLmg/dL Functions: skeletal muscle contraction. Functions: skeletal muscle contraction.

carbohydrate metabolism, adenosine carbohydrate metabolism, adenosine triphosphate formation (ATP), B-complex triphosphate formation (ATP), B-complex vitamin activation, DNA and protein vitamin activation, DNA and protein synthesissynthesis

Extracellular magnesium regulates blood Extracellular magnesium regulates blood coagulation and skeletal muscle coagulation and skeletal muscle contractilitycontractility

Chloride (Cl)Chloride (Cl)

Chloride normal plasma level 98 -106 mEq/LChloride normal plasma level 98 -106 mEq/L Functions: works with sodium to maintain Functions: works with sodium to maintain

extracellular fluid osmotic pressure, extracellular fluid osmotic pressure, important in the formation of hydrochloric important in the formation of hydrochloric acid in stomach, bicarbonate anion most acid in stomach, bicarbonate anion most commonly exchanged for chloridecommonly exchanged for chloride

Assessment Fluid Electrolyte BalanceAssessment Fluid Electrolyte Balance

HistoryHistory– Medical/surgical historyMedical/surgical history– MedicationMedication– Food/fluidFood/fluid

Physical assessmentPhysical assessment– S/S edema, dehydration, electrolyte imbalanceS/S edema, dehydration, electrolyte imbalance

Psychosocial assessmentPsychosocial assessment Diagnostic assessmentDiagnostic assessment

– Lab studies: blood, urineLab studies: blood, urine