Clinical Applications:Fluids & ElectrolytesV. Doreen Wagner, PhD, RN, CNORBiology 3317 ~ Pathophysiology

Fluid Balance Review

Primary component of bodyH2O

Functions of water in body

Body composition/distribution

Fluid DistributionIntracellular compartmentExtracellular compartmentInterstitial spacesPlasma (vascular) compartmentTranscellular compartment

Gains & LossesSkin

Lungs

Kidneyshttps://www.youtube.com/watch?v=vB7tSHqR1eY

Intestines

Fluid Balance RegulationThirstEndocrine system (Hormones)Antidiuretic Hormone (ADH) http://www.youtube.com/watch?v=8dQdfbE8kFU (15 mins)Aldosterone http://www.youtube.com/watch?v=Z0XPMFL45oo (10 mins)Renin-angiotensin-aldosterone system http://www.youtube.com/watch?v=BVUeCLt68Ik (14 mins)Cardiac systemAtrial Natriuretic Peptide (ANP)KidneysGI system

Forces - Moving Fluid In and Out of Capillaries

Tonicity of FluidsIsotonicEqual osmolarity to serumAdds to intravascular space without shiftsHypotonicLower osmolarity than serumShifts fluid out of intravascular space to hydrate cells and interstitial spaceHypertonicHigher osmolarity than serumDraws fluid into intravascular space from cells and interstitial space

Controlling Blood OsmolarityHigh osmolarity causes:Thirst increased water intakeADH release water reabsorbed from urineLow osmolarity causes:Lack of thirst decreased water intakeDecreased ADH release water lost in urine

Antidiuretic Hormone (ADH)Regulates H2O reabsorption in bodyPosterior Pituitary GlandADH Released H2O reabsorption in kidneys

ADH ImbalancesDiabetes insipidus (DI)Neurogenic or CentralNephrogenic

Syndrome of inappropriate ADH (SIADH)

Which may cause hyponatremia?

Diabetes Insipidus (DI)Too little ADH secretion from Posterior Pituitary ADH secretion H2O reabsorption Urine Output Blood VolumeHypernatremia

Clinical ManifestationsExtreme Polyuriaup to 30 liters/day!PolydipsiaNocturiaNatriuresis (excretion of Na+ in the urine)

May present with hypernatremia and dehydration - if unable to replace fluids

Syndrome of Inappropriate Antidiuretic Hormone (SIADH)Too much ADH secreted from Posterior Pituitary

Clinical ManifestationsFluid Volume Excess increased body weightHyponatremia (dilutional)ThirstDyspnea on exertionDulled sensoriumMuscle cramps & weaknessLow urine outputWhen serum sodium level falls < 120 mEq/LN&VMuscle cramps abdominal Seizures

~ Summary ~

The Rising TideFluid Volume ExcessEdema capillary pressure colloidal osmotic pressure capillary permeabilityLymphatic flow obstructionIncreased intake of fluidThird-Spacing

What to Look For in HypervolemiaOverloadBounding pulse/bradycardia/HTNRapid wt. gainPulmonary edemaTypical Lab results HCT hemodilutionWNL or HIGH serum sodium serum osmolality oxygen level

Dehydration vs. HypovolemiaDehydration Intracellular loss (increased solutes)Kidneys retain water

Hypovolemia Extracellular loss (isotonic loss)Loss of fluids and solutesLoss of circulating volumeBleeding3rd space fluid shift

DehydrationWhat tests show hematocrit serum osmolality serum sodiumUrine specific gravity above 1.030

How its treatedReplace missing fluidsGive fluids gradually

HypovolemiaWhat to Look for HR & thready, BPRestlessness, anxietyCool, clammy & pale skin (extremities)Delayed capillary refill Acute weight loss (>5-10%)More fluid loss = mental statusExtreme thirst urine output (10 30 mL/hr)> 40% isotonic loss leads to shock

Lab tests showLow to low normal electrolytes HGB & HCT w/hemorrhage urine specific gravity serum osmolality

How its treatedFlood of fluid replacementIsotonic IV fluids to expand circulating volumeBolusPlasma proteinsHypovolemia

Electrolyte Balance ReviewMajor Extracellular ElectrolytesSodiumCalcium

Major Intracellular ElectrolytesPotassiumPhosphorusMagnesium

SodiumMost abundant cation in bodyApprox. 60 mEq/kg of body weight135 145 normal valuesFound in ECF compartmentVery small amount in ICF Regulates ECF volumeIncluding vascular compartment fluidsPart of sodium bicarbonate moleculeImportant in acid-base balanceContributes to nervous system function

Osmolality and SodiumNormal level = 135145 mEq/LRegulates extracellular fluid volume and osmolarity

Question:Why would retaining sodium cause high blood pressure?

Sodium ImbalancesHyponatremia (145 mEq/L)Water deficitNa+ administration

PotassiumNormal level is 3.55.0 mEq/LMaintains intracellular osmolarityControls cell resting potentialNeeded for Na+/K+ pumpExchanged for H+ to buffer changes in blood pH

PotassiumCan be disturbed by diseases, injuries, medications & therapiesMust be ingested daily (40mEq)Body cant conserve K+Maintains balanceSodium-potassium pumprenal regulationpH levelControls cell resting potentialMaintains intracellular osmolarity

What Happens to Blood K+ Levels When:A person hasHyperaldosteronism?Alkalosis?An injection of epinephrine?Convulsions?Loop diuretics?Crush injury?

Normal level 8.5 10.5 mg/dLExtracellularBlocks Na+ gates in nerve & muscle cellsClottingLeaks into cardiac muscle Causing it to fireIntracellularNeeded for all muscle contractionActs as 2nd messenger in many hormone & neurotransmitter pathwaysCalcium

Extracellular Calcium Controls Nerve FiringHypercalcemiaBlocks more Na+ gatesNerves are less able to fireHypocalcemiaBlocks fewer Na+ gatesNerves fire more easilyWhich would cause Trousseaus sign?

Hypocalcemia ManifestationsNeural/Muscle EffectsParesthesia (numbness/tingling)Skeletal muscle spasms/crampsAbdominal muscle spasms/crampsHyperactive reflexesCarpopedal spasmLaryngeal spasmCardiovascular EffectsHypotension & cardiac insufficiencyProlonged QT interval arrhythmiasSkeletal Effects (chronic deficiency)Osteomalacia and bone pain

Hypercalcemia Manifestations Renal EffectsPolyuria w/Increased thirstSigns of acute renal insufficiencySigns of kidney stonesNeural and Muscle EffectsMuscle weakness with loss of toneLethargy Personality/behavioral changesStupor to comaCardiovascular EffectsHypertensionShortening of QT interval AV blockGastrointestinal EffectsAnorexiaNausea & vomitingConstipation

https://www.youtube.com/watch?v=SWv-aY4RH3c

MagnesiumNormal level is 1.82.7 mg/dLCofactor in enzymatic reactionsInvolving ATPDNA replicationmRNA productionBinds to Ca2+ receptorsCan block Ca2+ channels

Hypomagnesemia ManifestationsDisordered functions of Cardiovascular systemNeuromuscular systemSkeletal system

Associated with imbalances of other electrolytes - such as potassium and calcium

Hypermagnesemia ManifestationsKidneys have large capacity for Mg excretion so only occurs inRenal insufficiencyExcessive intake/correctionIf untreated, toxicity progresses toFlaccid paralysis & hyporeflexiaBradycardia and arrhythmiasRespiratory depressionComaCardiac arrest

Acid-Base Balance ReviewAcid-Base BasicsUnderstanding pHDeviation from normal pH

Maintaining Acid-Base BalanceChemical Buffer SystemsRespiratory SystemRenal System

Interpreting Acid-Base Imbalances

Acid (H+)Normal value: pH = 7.357.45Blocks Na+ gatesControls respiratory rateIndividual acids have different functions:Byproducts of energy metabolism (carbonic acid, lactic acid)Digestion (hydrochloric acid)Food for brain (ketoacids)

Respiratory or Volatile AcidCO2 + H2O H2CO3 (carbonic acid)H2CO3 H+ + HCO3- (bicarbonate ion)An increase in CO2 will cause Increases in CO2 (increased PCO2)Increases in H+ (lower pH)Increases in bicarbonate ion

Respiration and Buffers Adjust Blood pHScenario:A woman was given an acidic IV. Soon she began to breathe more heavily. Why?When her blood was tested, it had:Slightly lowered pHLow bicarbonateLow PCO2Slightly increased K+ Her urine pH was slightly loweredWhy?

Buffer Systems

Respiratory Acidosis and AlkalosisCO2 + H2O H2CO3 H+ + HCO3- (bicarbonate ion)

Respiratory acidosisRespiratory alkalosis PCO2 carbonic acid H+ = low pH (7.45) bicarbonate

Respiratory ImbalancesRespiratory Acidosis Alveolar hypoventilation ( PaCO2):Acute pulmonary edemaDepressed drive to breathe ( CNS, oversedation)Chronic respiratory diseaseRespiratory AlkalosisHyperventilation excessive breathingMechanical ventilationAnxiety, pain, fever, septic shock

Metabolic ImbalancesMetabolic acidosisIncreased levels of ketoacids, lactic acid, etc.Decreased bicarbonate levels

Metabolic alkalosisDecreased H+ levelsIncreased bicarbonate levels

Metabolic Acidosis and AlkalosisIncreased metabolic acids raise H+ levelsSome H+ combines with bicarbonate, decreasing itBreathing adjusts CO2 to bring pH back to normal

Metabolic acidosisMetabolic alkalosisH+ = low pH (7.45) bicarbonateLighter/shallow breathing causes PCO2

Metabolic Acidosis Acid and HCO3Acid excessRenal failureDiabetic ketoacidosisLactic acidosisStarvationhyperalimentationIngested toxins (ASA, antifreeze)Base deficitDiarrheaHyperkalemiaIntestinal fistulasCertain drugs

Metabolic AlkalosisMetabolic Alkalosis caused by:Acid lossVomiting or NG suctionHypokalemiaHypochloremiaLoop or thiazide diureticsSteroids

Excessive HCO3 Over correction of acidosis with NaHCO3Massive transfusion of whole bloodOveruse of LR solutionExcessive intake of oral bicarbonate

Beyond pH, PaCO2, & HCO3PaO2Measure of partial pressure of arterial O2WNL = 80 100 mm HgVaries with age after age 60 without signs of hypoxiaMay be lower in people who live at higher altitudes

SaO2Oxygen saturation measurement of percentage of hemoglobin actually carrying oxygenWNL = 95 100%

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