FLUID AND ELECTROLYTE BALANCE - Angelfire fileassessing fluid balance basal fluid requirements estimate the daily fluid requirements for a euvolemic patient with a body weight of 70

FLUID AND ELECTROLYTE BALANCE

John M. Burke, Pharm.D.St. Louis College of Pharmacy

Veterans Administration Medical Center

FLUID BALANCE

I. IntroductionII. Physiology of Body FluidsIII. Assessing Fluid StatusIV. Use of IV fluidsV. Hypernatremia

Body Fluid Distribution

Extracellular fluid Intracellular Fluid

= Sodium

= Potassium

ASSESSING FLUID BALANCEBASAL FLUID REQUIREMENTS

WEIGHT00--10 Kg10 Kg 100100 mLmL/Kg/Kg1010--20 kg20 kg 10001000 mLmL + 50+ 50 mLmL/kg (Wt/kg (Wt--10)10)>20 Kg>20 Kg 15001500 mLmL + 20+ 20 mLmL/kg (Wt/kg (Wt--20)20)

Body Surface Area 1500 ml/m2


ESTIMATE THE DAILY FLUID REQUIREMENTS FOR AEUVOLEMIC PATIENT WITH A BODY WEIGHT OF 70 KG


ESTIMATE THE DAILY FLUID REQUIREMENTS FOR AEUVOLEMIC PATIENT WITH A BODY WEIGHT OF 70 KG

10 kg10 kg 1000 ml/day1000 ml/day20 kg20 kg 1500 ml/day1500 ml/day60 kg60 kg 2300 ml/day2300 ml/day80 kg80 kg 2700 ml/day2700 ml/day

OTHER EXAMPLES

1500 ml + 20 ml/kg (70 kg - 20 kg)1500 ml + 20 (50)2500 ml/day = 104 ml/hr

ASSESSING FLUID BALANCE

SYMPTOMS DRY MOUTHEDEMACHANGES IN URINE OUTPUT

ASSESSING FLUID BALANCE

PHYSICAL FINDINGSWEIGHT CHANGESTEMPERATUREBP, ORTHOSTASIS, HEART RATEMUCOUS MEMBRANESJVD (PRESENCE/ABSENCE)PULM: RALESEDEMA (PRESENCE/ABSENCE)

ASSESSING FLUID BALANCEMONITORING FLUID STATUS

LABORATORYBUN, SERUM CREATININEURINE OSMOLALITYSERUM OSMOLALITYUna, FeNa

ASSESSING FLUID BALANCEMONITORING FLUID STATUS

Sensible losses: intake/output; urine output Insensible losses: 500-1000 ml/dayWeight

Fractional Excretion of Sodium

Calculate the FeNa for a 96 y/o female with CHF, diuretic therapy.Una = 11; Sna = 140; Ucr = 13.6; Scr = 2.1

FeNa = (Urine Na) / (Urine Cr) x 100(Serum Na) / (Serum Cr)

Fractional Excretion of Sodium

Calculate the FeNa for a 96 y/o female with CHF, diuretic therapy.Una = 11; Sna = 140; Ucr = 13.6; Scr = 2.1

FeNa = (11) / (13.6) x 100 = 1.2%(140) / (2.1)

FLUID BALANCE

SERUM OSMOLALITY

SOSM = 2[Na+] + BUN/2.8 + GLUCOSE/18

Normal serum osmolality: 280-300 mOsm/kg

ASSESSING FLUID BALANCEPLASMA OSMOLALITY


Calculate Sosm for a patient with:Sodium 135 mEq/LBUN 12 mg/dlGlucose: 90 mg/dl


SOSM = 2[Na+] + BUN/2.8 + GLUCOSE/18

= 2(135)= 2(135) + 12/2.8+ 12/2.8 + 90/18+ 90/18

= 270= 270 + 4+ 4 + 5+ 5

= 279= 279 mOsmmOsm/kg/kg

IV FLUIDS

ContentDistribution of IV fluidsBasal fluid requirementsCorrecting fluid deficitsReplacing free water deficits

IV Fluids

1 literD5W

Dextrose50 g

1 liter¼ NS

NaCl 38.5 mEq

1 literNS

NaCl154 mEq

1 liter1/2 NS

NaCl77 mEq

1 literRingers

NaCl147 mEqK 4Ca 4

308mOsm/l

154mOsm/l

77mOsm/l

250mOsm/l

310mOsm/l

Distribution of Normal Saline


= Sodium

= Potassium

NaCl

154 mEq

Distribution of D5W


= Sodium

= Potassium

Dextrose

50 g

DISTRIBUTION OF IV FLUIDS


What percentage of the fluid administered would What percentage of the fluid administered would stay in the EXTRAstay in the EXTRA--cellular space?cellular space?

normal saline normal saline = __= __100_100____%___%1/2 NS1/2 NS = ___= ___7373___%___%1/4 NS1/4 NS = ___= ___5555___%___%D5WD5W = ___= ___4040___%___%RingersRingers = ___97___%= ___97___%LRLR = ___= ___8686___%___%



How would you expect the addition of dextrose to an IV fluid to change the distribution?

Example: Normal saline vs Normal saline with D5W

IV Fluids

1 literNS

NaCl154 mEq

1 literD5NS

NaCl154mEq

Dextrose50 g

Providing Basal Fluid Requirements

Choice of IV Fluids½ Normal SalineD5 ½NS¼ Normal SalineD5 ¼NS

Rationale for choice: provides some sodiumsome free water

Providing Basal Fluid Requirements

IV fluid rate

ml/hr = basal fluid requirements/ 24 hours

AdditivesKCl: 20 mEq/l IVF (if serum K is normal)

Example55 y/o male. Ht 6’0”, Wt 78 kgNPO.EuvolemicBasal fluid requirements?

Example55 y/o male. Ht 6’0”, Wt 78 kgNPO.EuvolemicBasal fluid requirements?

Dextrose 5%/0.45% sodium chloride With 20 mEq KCl/L IVFInfused at 110 ml/hr

(see previous basal fluid requirement calculations)

Correction of Hypovolemia

Choice of IV FluidsNormal SalineLactated RingersRingers solution

Rationale for choice:

Correction of HypovolemiaIV Fluid rateSevere hypovolemia:500-1000 ml/hr until hemodynamically stablefollowed by a lower rateModerate hypovolemia2-3 times maintenance fluid requirementsMild hypovolemia1-2 times maintenance fluid requirements

ExampleBasal fluid requirements are 2000 ml/dayIf 20 mEq KCl is added to each liter, how much fluid would the patient receive?

Rate for maintenance fluids?

What if patient is hypovolemic?

What if patient is volume overloaded?

ExampleBasal fluid requirements are 2000 ml/dayIf 20 mEq KCl is added to each liter, how much fluid would the patient receive?

Rate for maintenance fluids?83 ml/hr; 40 mEq KCl per dayWhat if patient is hypovolemic?125-150 ml/hr; 60-72 mEq per dayWhat if patient is volume overloaded?

DISORDERS OF SODIUM BALANCE

VOLUME STATUSHYPOVOLEMIC

SODIUMSODIUMmEqmEq/L/L

< 135< 135

135135--145145

> 145> 145

ISOVOLEMIC HYPERVOLEMIC

NORMAL

FLUID/ELECTROLYTE DISORDERSHYPERNATREMIA

FLUID/ELECTROLYTE DISORDERSHYPERNATREMIA

DEVELOPMENT OF HYPERNATREMIAWater LossSodium Retention

Intact Thirst mechanism provides protection

ASSESSMENT OF THE PATIENT WITH HYPERNATREMIAASSESSMENT OF THE PATIENT WITH HYPERNATREMIA

HYPERVOLEMICHYPERVOLEMICHYPERNATREMIAHYPERNATREMIA

DETERMINE SERUM OSMOLALITYDETERMINE SERUM OSMOLALITY

ASSESS VOLUME STATUSASSESS VOLUME STATUS

HYPOVOLEMICHYPOVOLEMICHYPERNATREMIAHYPERNATREMIA

ISOVOLEMICISOVOLEMICHYPERNATREMIAHYPERNATREMIA

Renal lossesdiureticsglucosuriaARF/CRFpartial post-renal obst

Adrenal insufficiencyGI lossesResp lossesInsensible loss

Diabetes insipidus Renal FailureIatrogenicMineralocorticoid excess

FLUID/ELECTROLYTE DISORDERSASSESSMENT OF HYPERNATREMIA

HYPOHYPO--VOLEMICVOLEMIC EUVOLEMICEUVOLEMIC

H20 LOSS > Na LOSSH20 LOSS > Na LOSSnormal Nanormal NaSlSl H20 DEFICITH20 DEFICIT Na EXCESS >Na EXCESS >

H20 EXCESSH20 EXCESS

HYPERVOLEMICHYPERVOLEMIC

Diabetes InsipidusFluid Loss Renal FailureLiver FailureCHF

HypernatremiaClinical Manifestations

CNS dysfunction: restlessness irritabilitytremulousness spasticityhyperreflexia ataxiaseizures coma, death

polyuria if due to diabetes insipiduspolydipsia

Severity based on severity and rate of development

HypernatremiaClinical Manifestations

Urine osmolalityvariablebased on cause of hypernatremia

Volume statusvariablebased on cause

NormalBrainNormalosmolality

Water Loss

Highosmolality

Accumulationof electrolytes

Highosmolality

Accumulationof organicosmoles

CerebralEdema

Immediate effect ofhypertonic state

RapidAdaptation

SlowAdaptationRapid

correction ofhypertonicity

Slow Correctionof hypertonicity

water

Adrogue HJ. N Engl J Med 2000; 342: 1493-9.

HypernatremiaECF Volume

Low Normal/increased

Uvol < 3 l/day Uvol > 3 l/day

Uosm > 450 Uosm

> 300

Postural Hypotension

Na/H20 depletion 1º H20depletion

Uvol > 3 l/day

Uosm < 250 Uosm > 300

Osmotic diuresisDI

Responseto ADH

CentralDI

NephrogenicDI

yes noyes no

Osmoticdiuresis

Hypernatremia

Assessment of Free Water deficit

deficit (liters) = (Wt)(0.6) (Serum Na - 1)140

Correction of Hypernatremia



< 135< 135

135135--145145

> 145> 145


NORMAL

DISORDERS OF SODIUM BALANCE



< 135< 135

135135--145145

> 145> 145


NORMAL

Hypovolemic Hypernatremia

Etiologies:Renal lossesadrenal insufficiencyGI lossesRespiratory lossesInsensible losses

excessive loss of sodium and water [Na+] = Na

H2O



HYPERNATREMIA

Hypovolemic HypernatremiaStep 1: Replace ECVStep 2: Replace free water deficit

Hypovolemia

Hypovolemic HypernatremiaSeverity of Hypovolemia

2 Normal Saline Normal Saline

Persistent Hypernatremia

¼ Normal SalineDextrose 5% in Water

SevereMild/Mod


Desired rate of correction of hypernatremia0.5 mEq/L per hour

Replacement of Free Water

Choice of IV FluidsD5W: 100% free water¼NS: 75% free water½NS: 50% free water

Free Water Deficit

Assessment of Free Water deficit

deficit (liters) = (Wt)(%TBW) (Serum Na - 1)140

%TBW: 0.6 l/kg for children, men < 70 yrs%TBW: 0.5 l/kg for men > 70 yrs, females < 70%TBW: 0.45 l/kg for women > 70 yrs

Calculation of Free Water Deficit

Calculate free water deficit for a 75 y/o male (wt: 60 kg) with serum sodium of 160 mEq/l

Calculation of Free Water Deficit

Calculate free water deficit for a 75 y/o male (wt: 60 kg) with serum sodium of 160 mEq/l

deficit (liters) = (Wt)(%TBW) (Serum Na - 1)140

= (60 kg)(0.5)(160 - 1) = 4.3 L140

Replacement of free water deficit

Replacement of free water deficit is based on calculated deficit and free water contentTo replace 4.3 Liters of free water:

4.3 Liters of D5W5.7 Liters of ¼ NS8.6 Liters of ½ NS

Correction of IV FluidIV rate (ml/hr) = (free water deficit)(1000ml/L)

(Serum Na - 140) (% of free water in IVF)(0.5 mEq/l/hr)

Calculate IVF rate for:75 y/o male with weight 70 kg and serum Na of 160 mEq/L

1. Normal saline2. ½ normal saline3. ¼ normal saline4. Dextrose 5% in Water

Correction of IV Fluid

IV rate (ml/hr) = (5.0 L)(1000ml/L) (160 - 140) (% of free water in IVF)(0.5 mEq/l/hr)

Calculate IVF rate for: 75 y/o male with weight 70 kg and serum Na of 160 mEq/L

1. Normal saline (0) rate = XXXXX2. ½ normal saline (0.5) rate = 250 ml/hr3. ¼ normal saline (0.75) rate = 167 ml/hr4. Dextrose 5% in Water (1.0) rate = 125 ml/hr

DISORDERS OF POTASSIUM BALANCEDISORDERS OF POTASSIUM BALANCE

HYPOKALEMIAHYPOKALEMIA

CELLULAR METABOLISM

Em = - 61 log r[K]c + 0.01[Na]cr[K]e + 0.01[Na]e

Distribution of serum potassium

Action Potential

Distribution of potassiumSerum Cell

insulin

insulin

Epi/NE

pH

pH

Sosm

Sosm

Distribution of potassiumSerum Cell

insulin

insulin

Epi/NE

pH

pH

Sosm

Sosm

Etiology of Hypokalemia

Beta agonistIntracellular shift of potassiumTheophyllineIntracellular shift of potassiumInsulinIntracellular shift of potassiumDiuretics (HCTZ, furosemide)enhanced renal excretion


High dose penicillinEnhanced renal excretionMineralocorticoidsEnhanced renal excretionAminoglycosidesEnhanced renal excretionAmphoterecin-BEnhanced renal excretion


Cis-Platinumenhanced renal excretionSodium polystyrene sulfonateEnhanced fecal eliminationSorbitolEnhanced fecal eliminationDiarrheaEnhanced fecal elimination


Vomiting/NG suctionIncreased GI eliminationHypomagnesemiaDecreased intracellular potassiumEnhanced renal eliminationMetabolic alkalosisIntracellular shift of potassium


ETIOLOGYRe-Distribution of potassium

Metabolic AlkalosisInsulin

Decreased intake


ETIOLOGYINCREASED LOSSES

GI lossesSkin lossesRenal Losses

Increased renin activityIncreased mineralocorticoid activity

Transtubular Potassium Gradient

TTKG = [K+] urine / (Uosm/Sosm)[K+] serum

Normal = 6-8

Transtubular potassium Gradient

Sosm

Uosm

KDT

[K+] urine

[K+]

ProminentU Wave

BiphasicT wave

ST depression

Manifestations of Hypokalemia


CLINICAL MANIFESTATIONSCardiovascular

ArrhythmiasOrthostatic hypotension

MuscularWeakness, myalgiasCramps, ParalysisRhabdomyolysis


CLINICAL MANIFESTATIONSMetabolic

Abnormal carbohydrate metabolismHypercalcemiaHypomagnesemiaHyperlipidemiaAchlohydria


CLINICAL MANIFESTATIONSRENAL

Nephrogenic diabetes insipidusNegative nitrogen balancedecreased protein synthesisIncreased ammonia production by kidneys


NON-PHARMACOLOGIC THERAPYHighest content

dried figs, molassesVery High content

dried fruit, nuts, avocados, lima beansHigh Content

vegetables: spinach, tomatoes,carrotsbananas, oranges, mangos, watermelonmeat: beef, pork, lamb, veal

Potassium Supplementation

Why is serum potassium an imprecise measure of total body potassium?

How does this influence your estimate of need for supplementation?


SELECT/RECOMMEND THERAPYTOTAL DOSE REQUIREDESTIMATE for ACUTE Replacement:10 mEq per 0.1 mEq/L rise desired

1 mEq/L requires about 100 mEq K


Choice of salt formPotassium bicarbonate 6.5 mEq, 25 mEq

Potassium chloridecapsulesfor solutionsolutiontablet

Management of Hypokalemia[K+]

3.5-4.0mEq/L

Salt subsitutesDietary sources

3-3.5mEq/L

?Cardiacdisease

none 40-100mEq20 mEq/day

For prevention

2.5-3.0mEq/L

?Symptoms

PO IV

no yes

< 2.5mEq/L

IV

intolerant


SELECT/RECOMMEND THERAPYROUTE/RATE OF ADMINISTRATIONORAL


SELECT/RECOMMEND THERAPYROUTE/RATE OF ADMINISTRATIONORALCHOICE AFFECTED BY SEVERITY AND GI TOLERABILITY20-40 mEq doses at 4 hour intervals PRN


SELECT/RECOMMEND THERAPYROUTE/RATE OF ADMINISTRATIONINTRAVENOUSPREFERRED 10 mEq/HRMAXIMUM 20 mEq/HR WITH EKG MONITOR


ADJUNCTIVE THERAPYTRIAMTERENEAMILORIDESPIRONOLACTONEMAGNESIUM SUPPLEMENTATION

HYPERKALEMIAHYPERKALEMIAETIOLOGY

Increased IntakeRedistribution (ICF to ECF)Decreased urinary excretionrenal failure RTAvolume depletion ACE Inhibitorshypoaldosteronism TMP/SMXK-sparing agentsNSAID’s

Hyperkalemia

Muscle weakness

Cardiac Arrhythmias

HYPERKALEMIAHYPERKALEMIA

Assessment of Hyperkalemia

Assess the patient for symptoms, i.e. EKGConfirm true hyperkalemiaEvaluate for possible reversible causesEvaluate renal functionTranstubular potassium gradient (TTKG)Fractional excretion of potassium (FeK)

Transtubular potassium Gradientin Hyperkalemia

Sosm

Uosm

KDT

[K+] urine

[K+]

Low-hypoaldosteronsim

High-renal failure

Hyperkalemia

Hyperkalemia

Mild

Monitor Na PolystyreneSulfonate

Moderate Severe

IV CalciumIV NaHCO3IV insulin/dextrose

Hemodialysis


THERAPY FOR MILD HYPERKALEMIANo therapyIdentify reversible causesDietary potassium restrictionDiuretics

Hyperkalemia

Sodium polystyrene sulfonateA non-absorbable ion-exchange resin which binds potassium in the GI tract to enhance excretion of potassiumOnset: 2-3 hoursDose: 25-50 g PO or PR prn

Management of HyperkalemiaAbnormal EKG? IV Calcium

Continuous EKG monitoring

Hyperglycemia? IV insulin° BS

IV insulin + dextrose

Consider albuterol or NaHCO3

Sodium polystyrene sulfonate or Dialysis

Monitor [K] q 2 hrs until < 5.5 mEq/L

yesno

yesno

HYPERKALEMIAHYPERKALEMIACalciumRaises the threshold potential (less negative) and restores cardiac excitability


CalciumOnset: 1-2 minutesDuration: 10-30 minutesDose: CaGluc 1 gm (4.7 mEq) IV over 5 mins


Insulin/glucoseStimulates cellular uptake of potassium, redistributing total body stores of potassiumOnset: 30 minutesDuration: 2-6 hoursDose: D50W 50 ml (25 g) IV over 5 min with

10 units of regular insulin IV/SQOr D10W with 25-50 units insulin/L at 100-500 ml/hr


Sodium BicarbonateIncreases serum pH and stimulates redistribution of potassium intracellularlyOnset: 30 minutesDuration: 2-6 hoursDose: 50-100 mEq IV over 2-5 minutes

Hyperkalemia

AlbuterolBeta stimulation promotes intracellular distribution of potassiumOnset: 30 minutesDuration: 1-2 hoursDose: 10-20 mg via nebulizer over 10 mins

Hyperkalemia

HemodialysisIncreases potassium eliminationOnset of effect: immediateDuration of dialysis: variable (2-4 hrs)

MAGNESIUM BALANCEMAGNESIUM BALANCE

Jack Burke, Pharm.D.

HYPOMAGNESEMIAHYPOMAGNESEMIA

MAGNESIUM PHYSIOLOGY

MAGNESIUM IS AN Intra-CELLULARCATION AND ONLY 1% IS PRESENT EXTRACELLULARLY.


EtiologyCommon disordersGastrointestinalRenalInternal redistributionMiscellaneousDrugs


DRUG-INDUCED CAUSESAminoglycosides (gentamicin, etc)Amphoterecin BCyclosporineDiureticsdigoxinCis-Platinumethanol

HypomagnesemiaDescribe the mechanism responsible for hypomagnesemia:Prolonged NG suctionPancreatic insufficiencyRenal tubular acidosisCis-platinHyperaldosteronismNephrotic syndromeDiureticsGlucose, insulin, AA admin

HypomagnesemiaDescribe the mechanism responsible for hypomagnesemia:Prolonged NG suction Increased lossPancreatic insufficiency Dec absorptionRenal tubular acidosis Inc renal lossCis-platin Inc renal lossHyperaldosteronism Inc renal lossNephrotic syndrome Inc renal lossDiuretics Inc renal lossGlucose, insulin, AA Redistribution


CLINICAL MANIFESTATIONSNEUROMUSCULAR

Muscle Twitching TremorHyper-reflexia ParesthesiasTetany SeizuresComa NystagmusAtaxia Vertigo


CLINICAL MANIFESTATIONSPychiatric

ApathyDepressionDeliriumAgitationConfusionHallucinations


CLINICAL MANIFESTATIONSCardiac

PVC’s, V.Fib V.TachTorsade de PointesPredisposition to digoxin toxicityEKG : PR, QT prolongation,

wide QRSCoronary Spasm


CLINICAL MANIFESTATIONSRefractory hypocalcemiaRefractory hypokalemia

Magnesium Supplements

1 mMol = 2 mEq = 24 mg magnesiumMagnesium hydroxide (MOM)390 mg/5 ml; 800 mg/5 ml; 1.2 g/5 ml30 ml = 1.05 g = 87 mEqMagnesium oxide 140 capsules; 400, 420, 800 mg tablets49.6 mEq = 25 mMol = 1000 mg Mag Oxide20 mEq = 10 mMol = 400 mg Mg Ox = 240 mg Mg


SERUM Mg CONCENTRATION

< 1 mEq/L 1-1.5 mEq/L + aSx

Life-threatening Sx?

MgSO4 2 gm1 mEq/kg/day

1 mEq/kg IV0.5 mEq/kg

yes no

MOM 5 ml QIDMOM 5 ml QIDMgOxide MgOxide 400 mg BID400 mg BID--QIDQID

HYPERMAGNESEMIAHYPERMAGNESEMIA

EtiologyDecreased renal excretion

Acute/chronic renal failureExcessive intake

CatharticsTreatment of toxemia of pregnancy

MiscellaneousLithium hypothyroidismMilk-Alkali Syn Addison’s diseaseViral hepatitis Acute DKA


CLINICAL MANIFESTATIONS> 3 mEq/L hypotension, vasodilation> 4 QT prolongation> 4.5 bradycardia, heart blocks> 5 QRS prolongation, sedation> 7 somnolence, decreased reflexes> 10 coma, respiratory depression> 14 complete heart block>15 asystole


Which patients should be treated?Severely elevated concentrations

Significant neuromuscular or cardiovascular symptoms

Hypermagnesemia

Acute treatmentElemental Ca 100-200 mg IV

Calcium Gluconate 90 mg (4.5 mEq) per gCalcium chloride 270 mg (13.5 mEq) per g

Onset: immediateDuration: transient (1-2 hrs)

CALCIUM BALANCECALCIUM BALANCE

Normal calcium: 8.5-10.5 mg/dl

Calcium Balance

Ca++

Ca++- Albumin

MeasuredIn Serum

(active)

Calcium Balance

correction for hypoalbuminemiaFor every 1 g/dl albumin falls below 4 g/dl

add 0.8 g/dl to the measured CalciumExample

Serum Calcium 7.0 mg/dl Serum Albumin 2 g/dl

What is the corrected calcium concentration?

Documents

FLUID AND ELECTROLYTE BALANCE - Angelfire fileassessing fluid balance basal fluid requirements estimate the daily fluid requirements for a euvolemic patient with a body weight of 70