This document summarizes fluid and electrolyte physiology. The body contains 40L of total body water, with 60% intracellular fluid and 40% extracellular fluid. Electrolytes such as sodium, potassium, calcium, and chloride are regulated and important for cellular function. Fluid balance is maintained through intake, output, and hormonal control. Abnormalities in fluid volume or electrolyte levels can cause various signs and symptoms.

1. Fluid and electrolytes

2. Body Fluids16%40%4%Body Water (~40L) = 60% of body weight

3. Body fluid compartmentsInterstitialfluidsIntracellular fluidIntravascularfluid

4. Intracellular Fluid (ICF)Fluid within the cellsLocated primarily in skeletal muscle massProvide nutrients for metabolism:High in potassium, phosphate, & proteinModerate levels of Mg, SO4Assists in cellular metabolism

5. Extracellular fluid (ECF)Intravascular- plasma (half of total blood volume)Interstitial- surround all cells (eg. lymph)* Some interstitial fluid is TRANSCELLULARor under the influence of metabolic activity - respiratory fluid - pericardial fluid - GI digestive fluid - peritoneal fluid - CSF - intraocular fluid - pleural fluid - synovial fluid - gland secretions (sweat, enzymes)

6. Extracellular fluid (ECF)Surrounds cells Transport medium for nutrients, gases, waste products and other substances between blood and body cellsBack-up fluid reservoir Nutrients for cell functioningNaCaClGlucoseFatty acidsAmino Acids

7. Fluid MovementFluid movement is constant and is influenced by:1. membrane permeabilityActive : require energy to transport eg. Na/K pumpPassive : osmosis, diffusion, hydrostatic force2. colloid osmotic pressure (plasma proteins)3. hydrostatic pressure (cap. bed pressure)Mechanical force of water pushing against membraneForces H2O, Na, glucose to go across membrane to interstitial fluid

8. Renal RegulationKidneys are the most important regulators of volume and composition of body fluidsHormonal ControlAntidiuretic hormone (ADH)Renin-angiotensin-aldosterone system(RAA)Natriuretic peptides (NUP)

9. ADH regulatory mechanism

10. NUP regulatory mechanism

11. RAA regulatory mechanism

12. Daily Intake & Output Intake 2,500 – 3,000 mlLiquids 1,500 – 2,000 mlWater in food 700 mlWater of oxidation 250 mlOutput 1,400-2,300 mlRespiration & Perspiration (insensible) 600-900 ml Urine 800-1500 mlStool 250 ml

13. Water loss

14. Serum Osmolarity (Concentration)Normal value = 275 -295 >295 = concentrated (dehydrated) <275 = dilute (fluid overloaded)Serum Osmo = 2(Na) + glucose/18 +BUN/2.8Serum Osmo = Sodium x 2 (quick reference)

15. Serum Laboratory Findings (Normal)Serum sodium : 135-145 mEq/L Serum potassium : 3.5 – 5 mEq/LSerum chloride : 95 – 105 mEq/LSerum osmolarity : 275-295 mOsm/L Urea : 15 – 40 mg/dLCreatinine : 0.6 – 1.5 mg/dLBUN: creatinine : 10:1 ratioHematocrit (males 40-52% , females 37-46%)Total protein : 6.5 - 8.0 g/dL

16. Fluid volume deficitOutput > Intake -> Water extracted from ECFECF hypertonic (water moves out of cell -> cell dehydration) + osmotic pressure increased (stimulates thirst receptor in hypothalamus)ICF hypotonic with decreased osmotic pressure -> posterior pituitary secretes more ADHDecreased ECF volume -> adrenal glands secrete AldosteroneLabIncreased HCTIncreased BUN out of proportion to CrHigh serum osmolarityIncreased urine osmolarityIncreased specific gravityDecreased urine volume, dark color

17. Signs and symptomsAcute weight lossDecreased skin turgorOliguriaConcentrated urineWeak, rapid pulseCRT >2sDecreased BPIncreased pulseSensations of thirst, weakness, dizziness, muscle crampsSunken eyeballsDepressed fontanels

18. ManagementMajor goal : correction and prevention of ARFEncourage oral fluidsIV fluidsIsotonic solutions (0.9% NS or Hartmann) until BP back to normal, then hypotonic (0.45% NS)Monitor I & O, urine specific gravity, daily weightsMonitor skin turgorMonitor VS and mental statusEvaluationNormal skin turgor, increased UOP with normal specific gravity, normal VS, alert and conscious, good oral intake of fluids

19. Fluid volume excessHypervolemiaIsotonic expansion of ECF caused by abnormal retention of water and sodium Fluid moves out of ECF into cells and cells swellCausesCardiovascular – Heart failureUrinary – Renal failureHepatic – Liver failure, cirrhosisOther – Cancer, thrombus, PVD, drug therapy (i.e., corticosteriods), high sodium intake, protein malnutrition

20. Signs and symptomsPhysical assessmentWeight gainDistended neck veinsPeriorbital edema, pitting edemaLungs crepitationDyspneaMental status changesGeneralized or dependent edemaVSHigh CVP/PAWP↑ cardiac outputLab data↓ Hct (dilutional)↓ BUN (dilutional)Low serum osmolalityLow specific gravity

21. Signs and symptomsRadiographyPulmonary vascular congestionPleural effusionPericardial effusionAscites

22. ManagementSodium restriction (foods/water high in sodium)Fluid restriction, if necessaryClosely monitor IVFIf dyspnea or orthopnea > Semi-Fowler’sStrict I & O, lung sounds, daily weight, degree of edema, reposition q 2 hr Promote rest and diuresis

23. IV fluids

24. Crystalloids

25. Content of crystalloids

26. ElectrolytesMajor intracellular electrolytesPotassium (cation)Phosphorus (anion)Major extracellularelectrolytesSodium (cation)Chloride (anion)* Sodium is the determinant of osmolality (tonicity) since it is the major ECF cation

27. SodiumNormal 135-145 mEq/LMajor cation in ECFRegulates voltage of action potential; transmission of impulses in nerve and muscle fibers, one of main factors in determining ECF volumeElderly at riskHelps maintain acid-base balance

28. HypernatremiaCausesSymptoms - extreme thirst - tachycardia - dry mucous membranes - low grade fever - irritability - weakness/lethargy - spasticity - oliguria/polyuriaLabIncreased serum Na Increased serum osmolality Increased urine specific gravity

29. ManagementWater depletionOral hydration if toleratedIV infusion D5% or 0.45% NaClGive maintenance fluid requirement (40ml/kg/day)Salt gainRemove sodium using potent diuretic (eg. IV furosemide) with D5% infusedIn severe cases dialysis may be necessary*Assessment1) Normal level of serum Na2) Resolution of signs and symptoms

30. HyponatremiaDecrease in measured serum Na concentration below 135 mEq/LMild 125-134mEq/LModerate 110-124mEq/LSevere 100-109mEq/LEvaluate serum osmolarityIf osmolarity is hypotonic, evaluate volume status:HypervolemiaEuvolemiaHypovolemia

31. CausesResults from excess Na loss or water gainGI losses, diuretic therapy, severe renal dysfunction, severe diaphoresis, DKA, unregulated production of ADH associated with cerebral trauma, narcotic use, lung cancer, some drugs (eg. Thiazides, carbamazepine, desmopressin, oxytocin)Clinical manifestations↓ BP, confusion, headache, lethargy, seizures, decreased muscle tone, muscle twitching and tremors, vomiting, diarrhea, and cramps

32. Lab & ManagementLab investigationIncreased HCT, KDecreased Na, Cl, Bicarbonate, UOP with low Na and Cl concentrationUrine specific gravity ↓ 1.010ManagementMildWater restriction if water retention problem Increase Na in foods if loss of NaModerateIV 0.9% NS, 0.45% NS, HartmannSevere3% NS – short-term therapy in ICU setting

33. PotassiumNormal 3.5-5.5 mEq/LMajor ICF cationVital in maintaining normal cardiac and neuromuscular function, influences nerve impulse conduction, important in carbohydrate(CHO) metabolism, helps maintain acid-base balance, control fluid movement in and out of cells by osmosis

34. HypokalemiaSerum potassium level below 3.5 mEq/LCausesLoss of GI secretions (diarrhea, vomiting, villous adenoma, ileostomy or uterosigmoidostomy, fistula)Excessive renal excretion of potassium (diuretics, increased aldosterone secretion, renal tubular damage etc)Movement of K into the cells (insulin therapy)Prolonged fluid administration without K supplementationDiuretics (thiazide, loop, mannitol)

35. Signs and symptomsSkeletal muscle weakness, ↓ smooth muscle function, ↓ DTR’s↓ BP, heart block, AF, VT, VFECG changes (small/inverted T, prominent U, ST depression, prolonged PR intervals)Constipation, ileusMetabolic alkalosisMental depression and confusion

36. ManagementMild – moderate (K > 2.5)Oral KCl 2-4 hourly until return of serum K to at least 3.5Monitor K level to prevent hyperKPotassium-sparing diuretics (amiloride, triamterene, spironolactone) can be given of hypoK is secondary to renal lossesSevere (< 2.5) and/or with ECG changesFast correction 2g KCl in 200ml NS to infuse in 2 hours (<3g KCl/L)With ECG monitoringWhen ECG and cardiac rhythm normalize, IV infusion gradually tapered down and discontinue. Oral KCl is initiated.

37. HyperkalemiaSerum potassium level above 5.3 mEq/LCausesExcessive K intake (IV or PO) especially in renal failureTissue traumaAcidosisCatabolic state Signs and symptomsECG changes – tachycardia to bradycardia to possible cardiac arrestTall, tented T wavesCardiac arrhythmiasMuscle weakness, paralysis, paresthesia of tongue, face, hands, and feet, N/V, cramping, diarrhea, metabolic acidosis

38. ManagementStop K supplements and avoid K in foods, fluids, salt substitutesLytic IV cocktailCalcium gluconate 10% 10ml in 10 minutesInsulin 10U in D50 50ml in 30-60min, then maintain on D5Sodium bicarbonate 100-200mmol/L over 30minKalimate 5-10g tds/Resonium A 15-30 tds/qid PO or PR (cation exchange solution)Beta agonist therapyIV salbutamol 0.5mg in 15min or 10mg nebulization

39. CalciumNormal 4.5-5.5 mEq/L99% of Ca in bones, other 1% in ECF and soft tissuesTotal Calcium – bound to protein – levels influenced by nutritional state Ionized Calcium – used in physiologic activities – crucial for neuromuscular activity

40. Required for blood coagulation, neuromuscular contraction, enzymatic activity, and strength and durability of bones and teethNerve cell membranes less excitable with enough calciumCa absorption and concentration influenced by Vit D, calcitriol (active form of Vitamin D), PTH, calcitonin, serum concentration of Ca and Phos

41. HypocalcemiaMost common – depressed function or surgical removal of the parathyroid glandHypomagnesemiaHyperphosphatemiaAdministration of large quantities of stored blood (preserved with citrate)Renal insufficiency↓ absorption of Vitamin D from intestines

42. Signs and symptomsAbdominal and/or extremity crampingTingling and numbness (circumoral)Positive Chvostek sign (tapping over facial nerve -> twitching) PositiveTrousseau sign (inflate cuff for 5 min over diastolic P -> carpopaedal spasm)Tetany; hyperactive reflexesIrritability, reduced cognitive ability, psychosis, seizuresProlonged QT on ECG, hypotension, decreased myocardial contractilityAbnormal clotting

43. ManagementHigh calcium diet or oral calcium salts (mild) - √ formulas for calcium content IV calcium as 10% calcium chloride or 10% calcium gluconate in D5W– give with cautionClose monitoring of serum Ca and digitalis levels↓ Phosphorus levels with calcium carbonate↑ Magnesium levels Vitamin D therapyD2 (ergocalciferol) 25,000-150,000 IU/dayD3 (cholecalciferol) 50,000-100,000 IU PO daily

44. HypercalcemiaCausesMobilization of Ca from boneMalignancyHyperparathyroidismImmobilization – causes bone lossThiazide diureticsThyrotoxicosisExcessive ingestion of Ca or Vit D (milk alkali syndrome)

45. Signs and symptomsAnorexia, constipation, nausea, vomitingGeneralized muscle weakness, lethargy, loss of muscle tone, ataxiaDepression, fatigue, confusion, comaSoft tissue and corneal calcification (band keratopathy)Dysrhythmias and heart blockECG : shortened QT intervalsDeep bone pain and demineralizationPolyuria & predisposes to renal calculiPathologic bone fractures Osteitisfibrosa in hyperparathyroidism

47. Hypercalcemic crisisEmergency – level of 8-9 mEq/LIntractable nausea, dehydration, stupor, coma, azotemia, hypokalemia, hypomagnesemia, hypernatremiaHigh mortality rate from cardiac arrest

48. TreatmentNS IV – match infusion rate to amount of UOPI&O hourlyLoop diureticsCorticosteroids and Mithramycin in cancer clients to inhibit osteolytic bone resorptionBiphosphonates and/or calcitonin to inhibit bone resorption and increase renal Ca excretionOral phosphate 1-3g/dayEncourage fluidsDialysis

49. MagnesiumCauses vasodilatation Decreases peripheral vascular resistance Balance - closely related to K and Ca balanceIntracellular compartment electrolyteHypomagnesemia - < 1.5 mEq/LHypermagnesemia - > 2.5 mEq/L

50. HypomagnesemiaCausesDecreased intake or decreased absorption or excessive loss through urinary or bowel eliminationAcute pancreatitis, starvation, malabsorption syndrome, chronic alcoholism, burns, prolonged hyperalimentation without adequate MgHypoparathyroidism with hypocalcemiaDiuretic therapy

51. Signs and symptomsTremors, tetany, ↑ reflexes, paresthesias of feet and legs, convulsionsPositive Babinski, Chvostek and Trousseau signsPersonality changes with agitation, depression or confusion, hallucinationsECG changes (PVC’S, V-tach and V-fib)TreatmentMildDiet – Best sources are unprocessed cereal grains, nuts, legumes, green leafy vegetables, dairy products, dried fruits, meat, fishMagnesium saltsMore severeMgSO4 IM MgSO4 IV slowly Monitor Mg q 12 hrMonitor VS, knee reflexesPrecautions for seizures/confusionCheck swallow reflex

52. HypermagnesemiaMost common cause is renal failure, especially if taking large amounts of Mg-containing antacids or cathartics; DKA with severe water lossSigns and symptomsHypotension, drowsiness, absent deep tendon reflex, respiratory depression, coma, cardiac arrestECG – Bradycardia, complete HB, cardiac arrest, tall T waves TreatmentWithhold Mg-containing productsCalcium chloride or gluconate IV for acute symptomsIV hydration and diureticsMonitor VS, LOCCheck patellar reflexes

53. PhosphorusNormal 2.5-4.5 mg/dLIntracellular mineralEssential to tissue oxygenation, normal CNS function and movement of glucose into cells, assists in regulation of Ca and maintenance of acid-base balanceInfluenced by parathyroid hormone and has inverse relationship to Calcium

54. HypophosphotemiaCauses - Malnutrition - Hyperparathyroidism - Certain renal tubular defects - Metabolic acidosis (esp. DKA) - Disorders causing hypercalcemiaSigns and symptomsImpaired cardiac functionPoor tissue oxygenationMuscle fatigue and weaknessN/V, anorexiaDisorientation, seizures, coma Treatment of moderate to severe deficiency Oral or IV phosphate (do not exceed rate of 10 mEq/h)Identify patients at risk for disorder and monitorPrevent infectionsMonitor levels during treatment

55. HyperphosphotemiaCausesChronic renal failure (most common)Hyperthyroidism, hypoparathyroidismSevere catabolic statesConditions causing hypocalcemiaSigns and symptomsMuscle cramping and weakness↑ HRDiarrhea, abdominal cramping, and nauseaTreatmentPrevention is the goal Restrict phosphate-containing foodsAdminister phosphate-binding agents DiureticsTreat causeTreatment may need to focus on correcting calcium levels

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