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ELECTROLYTES, WATER ELECTROLYTES, WATER AND ACID-BASEAND ACID-BASE

BALANCE DISORDERSBALANCE DISORDERS

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Course outlineCourse outline

IntroductionIntroduction

Units of solute measurementsUnits of solute measurements

Distribution and composition of Distribution and composition of body fluidsbody fluids

Disturbances of HDisturbances of H22O & O & electrolyte balanceelectrolyte balance

Disturbances in acid-base Disturbances in acid-base balancebalance

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“ “ No metabolic processes that No metabolic processes that are not affected by or are not affected by or

dependent upon electrolytes dependent upon electrolytes and water”and water”

A number of A number of methods and methods and instrumentsinstruments is available for is available for

measuring of electrolytes & blood measuring of electrolytes & blood pHpH

Knowledge of basic mechanisms Knowledge of basic mechanisms involved in electrolyte alterations involved in electrolyte alterations and ability to interpret lab results and ability to interpret lab results

is paramount for is paramount for efficacious efficacious therapytherapy

IntroductionIntroduction

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Units of solute measurementsUnits of solute measurements

1.1. Mass/weight:Mass/weight:- Concentration of a substance in a std Concentration of a substance in a std

vol. of solutionvol. of solution

- Atomic mass (relative: O=16, H=1)Atomic mass (relative: O=16, H=1)

- Molar mass (molal & molar solution)Molar mass (molal & molar solution)

2.2. Combining capacity (equivalency):Combining capacity (equivalency):- Mass (g) of substance which will Mass (g) of substance which will

combine with 1 g of combine with 1 g of Hydrogen ionHydrogen ion

- Equivalent weight = Atomic wt / Equivalent weight = Atomic wt / chargecharge

- Normal solution = Equivalent wt in 1L Normal solution = Equivalent wt in 1L of waterof water

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3.3. Osmotic pressure:Osmotic pressure:

- Not related to mass or charge but Not related to mass or charge but related to the related to the number or particlesnumber or particles in in solutionsolution

- The unit measure is The unit measure is osmole (Osm)osmole (Osm)

- 1 osmole = atomic or molecular mass 1 osmole = atomic or molecular mass ( (un-dissociatedun-dissociated substance) substance)

- 1 osmole = atomic or molecular 1 osmole = atomic or molecular mass /n (mass /n (where where nn is the number of is the number of particles into which each molecule particles into which each molecule dissociatesdissociates))

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Examples:Examples:

• 180 gm Glucose = 1 mole = 1 osmole180 gm Glucose = 1 mole = 1 osmole

• 58.5 gm NaCl = 1 mole = ?? osmoles 58.5 gm NaCl = 1 mole = ?? osmoles

NaCl NaCl Na Na++ + Cl + Cl-- (i.e., n = 2) (i.e., n = 2)

therefore: therefore: 1 osmole NaCl1 osmole NaCl = 58.5/2 = 58.5/2 = 29.25 gm= 29.25 gm

Osmolarity = osmoles / L of Osmolarity = osmoles / L of solutionsolution

Osmolality = osmoles / kg of Osmolality = osmoles / kg of waterwater

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A: Body fluid A: Body fluid compartmentscompartments

Distribution & composition of body Distribution & composition of body fluidsfluids

ICFICF ECFECF

BFCBFC

Intravascular Intravascular fluid fluid - plasma- plasma

Interstitial fluidInterstitial fluid - outside - outside vesselsvessels - between cells- between cells

Trans-cellular fluidTrans-cellular fluid - specialized - specialized fluidsfluids

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Trans-cellular fluids (TCF)Trans-cellular fluids (TCF)

- specialized body fluids formed thru specialized body fluids formed thru active transportactive transport process (cf: interstitial process (cf: interstitial fluid fluid passive transduction) passive transduction)

- include include fluids offluids of glands, skin, gonads, glands, skin, gonads, mucous membranes, GIT, eye, CSFmucous membranes, GIT, eye, CSF

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Determination of fluid volumesDetermination of fluid volumes

- tracer dilution technique (TDT)tracer dilution technique (TDT)- bio-impedance spectroscopy (BIS)bio-impedance spectroscopy (BIS)

Principle: TDTPrinciple: TDT

- several assumptions are madeseveral assumptions are made

- substance (substance (dye [Evans blue], radioactive dye [Evans blue], radioactive material [deuterised Hmaterial [deuterised H22O, Na-sulfate]O, Na-sulfate]) ) is injected into the bodyis injected into the body

- allowed to equilibrateallowed to equilibrate

- the amount injected is the amount injected is comparedcompared to to its concentration in the compartment its concentration in the compartment of interestof interest

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Principle: BISPrinciple: BIS

- response of a response of a living organismliving organism to to externally applied externally applied electricelectric current current

- it measures the it measures the opposition to the flowopposition to the flow of of electric current thru tissues (cf: electric current thru tissues (cf: conductivity)conductivity)

- it’s a it’s a non-invasive methodnon-invasive method of studying of studying blood flow, body fluids & body blood flow, body fluids & body compositionscompositions

- more more accurateaccurate than the dilution methods than the dilution methods

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General observations:General observations:

- relative distribution of fluid in relative distribution of fluid in compartments is compartments is similarsimilar for all domestic for all domestic animals & mananimals & man

- body water has body water has higherhigher proportion of proportion of body weight in body weight in youngyoung animals animals

- study variationsstudy variations: tracer types, : tracer types, techniques, etc techniques, etc

- within species variationswithin species variations: body fat: body fat

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B: Body fluid B: Body fluid compositioncompositionPrincipal ions of ECF:Principal ions of ECF:

- Sodium (Na- Sodium (Na++))- Chloride (Cl- Chloride (Cl--))- Bicarbonate - Bicarbonate

(HCO(HCO33--))

Principal ions of ICF:Principal ions of ICF: - Potassium (K- Potassium (K++))- Magnesium - Magnesium

(Mg(Mg2+2+))- Phosphate (PO- Phosphate (PO33

--))- Protein- Protein

Note:Note: Difference are due to Na-K Difference are due to Na-K pumppump

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C: Osmotic C: Osmotic forcesforces- the force that determines - the force that determines volumevolume & & distributiondistribution of fluids in various of fluids in various compartmentscompartments

- [H- [H22O] in these compartments is largely O] in these compartments is largely determined by [determined by [solutesolute]]

- H- H22O O absorptionabsorption from GIT & renal tubules is from GIT & renal tubules is a a passivepassive process due to existence of process due to existence of osmoticosmotic gradientsgradients

- - fluid volume disordersfluid volume disorders may result from may result from abnormalities in [solute] abnormalities in [solute] maldistributionmaldistribution of Hof H22OO

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A: Water A: Water abnormalitiesabnormalitiesDehydration - Dehydration -

• water loss and/or water loss and/or intake intake increased osmolarity increased osmolarity ADH ADH

CausesCauses

• diarrhoea, vomiting, burns, sweating, diarrhoea, vomiting, burns, sweating, etcetc

• lack of water intake: access, inability lack of water intake: access, inability to drink, nervous system disturbances, to drink, nervous system disturbances, etcetc

1. Disturbances of H1. Disturbances of H22O & electrolyte O & electrolyte balancebalance

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Measurement of dehydrationMeasurement of dehydration

• indirectlyindirectly by measuring [Hb], & by measuring [Hb], & RBC counts but interpretation RBC counts but interpretation depends on: depends on:

- what were the baseline values?- what were the baseline values?- hormonal effect- hormonal effect- excitement- excitement

• or or total plasma proteintotal plasma protein preferred preferred as is as is notnot affected by hormones affected by hormones

• physical examination, physical examination, body weightbody weight changeschanges

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B: Electrolyte B: Electrolyte abnormalitiesabnormalities

Hyponatremia – Hyponatremia – (low plasma [Sodium])(low plasma [Sodium])

• dietary deficiencydietary deficiency

• diarrhoea, vomiting, renal disease diarrhoea, vomiting, renal disease e.g. hypoadrenocorticism (Addison’s), e.g. hypoadrenocorticism (Addison’s), excessive sweating, diabetes mellitus, excessive sweating, diabetes mellitus, exudation from burnsexudation from burns

i) Sodium (Nai) Sodium (Na++))

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• usually Nausually Na++ loss is accompanied with loss is accompanied with water losswater loss

• renal compensatoryrenal compensatory mechanism will mechanism will operate to conserve Naoperate to conserve Na++

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Hypernatremia – Hypernatremia – (high plasma [Sodium])(high plasma [Sodium])

• rare, rare, occurs only ifoccurs only if there is: there is:- abnormal thirsty mechanism e.g., abnormal thirsty mechanism e.g., inability to drinkinability to drink- no access to adequate pure waterno access to adequate pure water

• it is always associated with hyper-it is always associated with hyper-osmolalityosmolality

• excessive Naexcessive Na++ intake with limited intake with limited water water salt poisoningsalt poisoning

• advanced chronic renal failure with a advanced chronic renal failure with a low glomerular filtration rate*low glomerular filtration rate*

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ii) Potassium (Kii) Potassium (K++))

• serum levels serum levels do not reflectdo not reflect true true status of body Kstatus of body K++ level because it is in level because it is in the ICFthe ICF

• serum [Kserum [K++] can ] can increaseincrease in massive in massive cellularcellular necrosisnecrosis

• also during also during acidosisacidosis plasma [K plasma [K++] ] increases about 0.6 mEq/L for each 0.1 increases about 0.6 mEq/L for each 0.1 unit decrease in pHunit decrease in pH

• in all these conditions, changes are in all these conditions, changes are not due tonot due to absolute intracellular K absolute intracellular K++ alterations alterations

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Hyperkalemia (high plasma [KHyperkalemia (high plasma [K++])]) - -

• acute renal failure while the acute renal failure while the intake is intake is highhigh and the animal has and the animal has anuria anuria or or oligouriaoligouria

• Addison’s disease in association with Addison’s disease in association with administration of administration of KK++-sparring diuretics-sparring diuretics

• increased intake when increased intake when KCl KCl is used asis used as salt substitutesalt substitute during salt restriction in during salt restriction in congestive heart failurecongestive heart failure

• death occurs due to cardiac arrest death occurs due to cardiac arrest when [Kwhen [K++] exceeds 10-12mEq/L] exceeds 10-12mEq/L

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iii) Chloride (Cl-)iii) Chloride (Cl-)

Hypo-chloridemiaHypo-chloridemia- losses from the GIT; prolonged losses from the GIT; prolonged vomitingvomiting- advanced renal failureadvanced renal failure- exudation from burnsexudation from burns

Note:Note: alterations generally follow alterations generally follow those of those of NaNa++ as Cl as Cl-- is is passivelypassively absorbed, absorbed, excreted & excreted & distributed with sodiumdistributed with sodium

Hyper-chloridemiaHyper-chloridemia- occurs with dehydrationoccurs with dehydration- reported in congestive heart failurereported in congestive heart failure

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Measurement of electrolyte levelsMeasurement of electrolyte levels

• Sample:Sample: blood is collected and serum is blood is collected and serum is harvested immediately to avoid ion harvested immediately to avoid ion exchangeexchange

• Techniques:Techniques: used for estimating used for estimating electrolyte levels in plasma & serumelectrolyte levels in plasma & serum

- flame photometry with ion-specific - flame photometry with ion-specific electrodeselectrodes- spectrophotometry- spectrophotometry- titration methods- titration methods

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2. Disturbances in acid-base 2. Disturbances in acid-base balancebalance A-BBA-BB

AcidosisAcidosis AlkalosisAlkalosis

RespiratoryRespiratory MetabolicMetabolic RespiratoryRespiratory MetabolicMetabolic

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Deviations in the acid-base balance are Deviations in the acid-base balance are mainly mainly acidosisacidosis and and alkalosisalkalosis ; both are ; both are generally classified as:generally classified as:

• Respiratory – Respiratory – due to abnormalities in due to abnormalities in the pulmonary gaseous exchange the pulmonary gaseous exchange mainly alteration of pCOmainly alteration of pCO22 of the blood of the blood

• Non-respiratory (metabolic) – Non-respiratory (metabolic) – due to due to various causes e.g., renal failure, various causes e.g., renal failure, vomiting, diarrhoea & shock. vomiting, diarrhoea & shock. Characterised by alteration in the Characterised by alteration in the [HCO[HCO33

--] in the blood] in the blood

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1.1. Respiratory acidosis Respiratory acidosis –– (hypoventilation)(hypoventilation)

- when CO- when CO2 2 elimination is decreased elimination is decreased increased blood pCOincreased blood pCO22 & H & H22COCO33

Compensation:Compensation: Kidney Kidney (( excretion of H excretion of H++; ;

reabsorption of HCOreabsorption of HCO33--; Cl; Cl-- excreted in excreted in

exchange with HCOexchange with HCO33--))

Examples:Examples: gaseous anesthetics in gaseous anesthetics in closed-closed- system apparatus; obstruction system apparatus; obstruction of airways; of airways; asthma, bronchitis, etcasthma, bronchitis, etc

Lab findings:Lab findings: H H22COCO33 ; ; pCO pCO22 ; ; pH pH

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2.2. Respiratory alkalosis Respiratory alkalosis –– (hyperventilation)(hyperventilation)

- when there is a deficiency of H- when there is a deficiency of H22COCO3 3 as a as a consequence of pCOconsequence of pCO22 loss loss

Compensation:Compensation: KidneyKidney ( ( NH NH33 formation; formation; reabsorption reabsorption of HCOof HCO33

--; ; HCOHCO33- - excreted in exchange excreted in exchange

with Clwith Cl--))

Examples:Examples: pain or psychologic stress, pain or psychologic stress, general anesthesia with excessive general anesthesia with excessive artificial respirationartificial respiration

Lab findings:Lab findings: HH22COCO33 ; ; pCOpCO22 ; ; pHpH

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3.3. Non-respiratory acidosis Non-respiratory acidosis ––

- acid accumulation in the excess of the - acid accumulation in the excess of the rate of elimination; more commonrate of elimination; more common

Compensation:Compensation: Pulmonary Pulmonary hyperventilation & hyperventilation & bicarbonate buffer system bicarbonate buffer system Renal Renal increased acid excretion increased acid excretion

Examples:Examples: lactic acid accumulation with lactic acid accumulation with excessive muscular activity; heat excessive muscular activity; heat

stroke; stroke; cellular hypoxia; diarrhoeacellular hypoxia; diarrhoea

Lab findings:Lab findings: HCOHCO33--; normal pCO; normal pCO22 ; ; pH; a pH; a

degree of hyperkalemiadegree of hyperkalemia

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4.4. Non-respiratory alkalosis Non-respiratory alkalosis ––

- accumulation in the ECF of abnormally - accumulation in the ECF of abnormally large amounts of HCOlarge amounts of HCO33

-- increased pH & increased pH & HCO3

-/H2CO3 ratio

Compensation:Compensation: PulmonaryPulmonary hypoventilation to hypoventilation to pCO pCO22

RenalRenal increased excretion of increased excretion of HCO3- ionion

Examples:Examples: digestive tract disordersdigestive tract disorders

Lab findings:Lab findings: HCOHCO33--; normal pCO; normal pCO22 ; ; pH; pH;

a a degree of hyperkalemiadegree of hyperkalemia

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5.5. Mixed acid-base imbalances Mixed acid-base imbalances ––

- several combinations of the primary - several combinations of the primary acid-base disturbances may developacid-base disturbances may develop

- lab determinations are used in - lab determinations are used in identifying them; otherwise first identifying them; otherwise first inspection may be confusinginspection may be confusing

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Measurement of acid-base balanceMeasurement of acid-base balance

The bicarbonate/carbonic acid buffer The bicarbonate/carbonic acid buffer systemsystem – the most abundant in the body, – the most abundant in the body, easy to measure and controleasy to measure and control

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• Machine:Machine: pH meter with sufficient pH meter with sufficient sensitivity to detect minor deviations. sensitivity to detect minor deviations. Automated systemsAutomated systems are used are used

• Samples:Samples: must be collected and handled must be collected and handled under conditions in which under conditions in which exposure to air is exposure to air is avoidedavoided or kept at minimum or kept at minimum

- venous blood- venous blood- heparinized syringe & vacutainer- heparinized syringe & vacutainer- tubes must be filled completely to - tubes must be filled completely to

avoid airavoid air- analyzed immediately or keep at 4 - analyzed immediately or keep at 4 00CC

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• Clinical evaluation of patients:Clinical evaluation of patients:

- history- history

- physical examination (respiration, - physical examination (respiration, dehydration, body wt, etc)dehydration, body wt, etc)

- ECG (K- ECG (K++ abnormalities especially abnormalities especially [K][K]))

• Laboratory evaluation of patients:Laboratory evaluation of patients:

- routine haematology (Hb, PCV, RBC - routine haematology (Hb, PCV, RBC counts, total plasma solids, etc)counts, total plasma solids, etc)

- routine urinalysis (specific gravity & - routine urinalysis (specific gravity & pH) with pH) with cautious interpretationcautious interpretation of of results depending on animal species & results depending on animal species & ADH functionADH function

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• Serum electrolyte determinations:Serum electrolyte determinations:

- flame spectrophotometry (Na- flame spectrophotometry (Na++ & & KK++) of ) of heparinized serumheparinized serum

- Cl- Cl-- can be determined can be determined electrometrically, electrometrically, spectrophotometrically & by titrationspectrophotometrically & by titration

• Other serum chemistry:Other serum chemistry:

- blood urea nitrogen (BUN) - blood urea nitrogen (BUN) concentrationconcentration

- it draws attention to the - it draws attention to the possibility of possibility of renal disease**renal disease**

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UFISADI

King Jeta, having a snackKing Jeta, having a snack

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END OF LECTURE END OF LECTURE END OF TOPICEND OF TOPIC