Water, Electrolyteand Acid-BaseBalance · 2018-02-18 · Water, Electrolyteand Acid-BaseBalance You created this PDF from an application that is not licensed to print to novaPDF printer

WaterWater, , ElectrolyteElectrolyte andandAcidAcid--BaseBase BalanceBalance

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WaterWater BalanceBalance1. Water is the main component of blood and

cells. It fills spaces around cells. 2. The body must keep the amount of water

in balance.

3. The water in the body contains dissolvedminerals called electrolytes.

4. The body must also keep levels ofelectrolytes in balance.

5. The balance of electrolytes is closely tiedto the balance of water in the body:



WaterWater BalanceBalanceTotal body water (TBW) content averages50-70% of body weight. This volume depents

on:1. Age2. Sex3. Fatty mass per cent (fat tissue has a lower

water content)

About 2/3 of TBW is intracellular and 1/3 extracellular.





WaterWater BalanceBalance

34 %40 %Intracellular water< 2 - 3 %< 2 - 3 %Transcellular water

15 %15 %Extravascular,exstracellular water

5 %5 %Intravascular water20%20%Extracellular water:54%60%Total Body Water

FemaleMale





Daily water balance



DehydrationDehydration

Dehydration is not having enough water in the body.

The body tries to keep blood pressure from falling by moving water from cell and the spaces around the cellinto blood vassels.

Tissues dry out.

The kidney try to conserve water by concentratingurine



ConditionsConditions thatthat make make dehydrationdehydrationmoremore likelylikely includeinclude thethe followingfollowing::

Hot weather, because sweating is increased. Fever, because sweating is increased and breathing

becomes more rapid Diarrhea, Vomiting,. Diabetes that is poorly controlled, because the body

produces more urine. Kidney disorders, because the kidneys are less able to

concentrate urine as needed. Problem with walking, because getting water is difficult. Dementia, because the sense of thirst is reduced and the

ability to get water when needed is impaired. Use of diuretics, because these drugs increased the amount

of water (and salt) excreted by kidneys.



IsotonicIsotonic dehydrationdehydration Na loss in the isoosmolalic solution form. Body fluid loss by digestive track (vomiting, diarrhea). Loss of sodium and water by kidneys. Blood loss. Intestinal obstruction.MainMain symptom:symptom: hypovolemia, circulatory disturbances,

collapse, pressure fall, kidney function disturbances(prerenal failure) with oliguria and uremia.

Laboratory tests:Hb , Ht , Total protein , RBC Na - 0



HypertonicHypertonic dehydrationdehydration

Free water loss; more water is losed than sodium. High loss of body fluids by: kidney (renal diabetes

insipidus, osmotic diuresis in diabetes), lungs(hiperventilation), skin.

Low water intake: young children, senseless people, oldpeople.

Laboratory tests:Ht (0), Hb , Osm , Na , RBC



HypotonicHypotonic dehydrationdehydration

Sodium loss syndrom Loss of sodium by kidneys: chronic renal

failure, Addison disease, organic lesion ofcentral nervous system.

Laboratory tests:Ht , Hb , Osm , RBC Na ,





OverhydrationOverhydration

Overhydration is having too much water inthe body.

The blood vessels overfill and fluid movesfrom the blood vessels into the spacesaround cells, causing swelling (edema).



OverhydrationOverhydration Blood test may be done to measure levels of

electrolytes or other substances that indicate howwell the kidney are functioning

A chest x-ray can show the back of fluid in thelungs.

Test may be needed to determine whetherheartfailure is present.

For people who are overhydrated, treatmentinvolves helping the body excrete the excesswater. Diuretic are drugs that help the kidneys do just that.



OverhydrationOverhydration

Overhydration has many causes: Heart failure. Kidney disorders. When the body produces too much antidiuretic

hormone (may be coused by pneumonia, strokeand by drugs like carbamazepine and sertraline).

Too rapid intravenous fluids infusions or bloodtransfusions.



IsotonicIsotonic overhydrationoverhydration

Excessive retention of body water and Na.Occure in hepatic, cardiac and hunger edema.Exciting cause:Chronic circulatory insufficiency,Cirrhosis,Chronic glomerulitis.Laboratory tests:Na – 0/ Ht , Hb , RBC



HypotonicHypotonic overhydrationoverhydration „Water poisoning”Excessive retention of body waterExcessive administration of salt-free solutions, gastric lavage with water, increased ADH activity, liver failure.

Laboratory tests:Na – Ht 0/ , Hb , RBC



HypertonicHypertonic overhydrationoverhydration

Sodium excess Primary hyperaldosteronism (Conn’s syndrom)Excessive supply of hypertonic fluids:Parenteral (ex.patients with renal failure)Oral ( ex. sea water drinking by castaways).Laboratory tests:Na Ht , Hb , RBC , Osm



ComparisonComparison dehydrationdehydration withwithoverhydrationoverhydration

Hypertonic overhydration

0Hypotonic overhydration0Isotinic overhydration

0Hypertonic dehydration

Hypotonic dehydration

0Isotonic dehydration

HbRBCHtNa



OsmolalityOsmolality

Osmolality is a count of the total number of osmotically active particles in a solution and is equal to the sum of the molalities of all the solutes present in that solution.

The osmolality of plasma is closely regulated by anti-diuretic hormone (ADH).

The osmolality of a solution can be measured using an osmometer. The most commonly used instrument in modern laboratories is a freezing point depression osmometer.



OsmolalityOsmolality Plasma osmolality can also be calculated from the measured

components. While there are many equations, a simple one is as follows:

Serum oSerum osmolalitysmolality [[mOsmmOsm/kg H/kg H22O]O] = 2 x Na + Glucose+ urea = 2 x Na + Glucose+ urea (all measurements in (all measurements in mmolmmol/L)/L) OrOr

Serum Serum osmolalityosmolality [[mOsmmOsm/kg H/kg H22O]O] = 2 x = 2 x Na[mmolNa[mmol/L] + /L] + Glucose[mg/dGlucose[mg/dL]/18+ + L]/18+ + urea[mg/durea[mg/dL]/6L]/6

Reference range (plasma,serum): 275 – 300 mOsm/L Reference range (urine): 50 – 1400 mOsm/L The difference between the measured and calculated plasma

osmolality is known as the the osmolarosmolar gapgap and normally is between 0 and 10 0 and 10 mOsmmOsm/kg./kg.



Clinical Uses Clinical Uses Serum Serum osmolalityosmolality is used in two main circumstances:

investigation of hyponatraemia and identification of an osmolar gap.

Urine Urine osmolalityosmolality is an important test:- of renal concentrating ability,- for identifying disorders of the ADH mechanism, - identifying causes of hyper-or hyponatraemia.

Faecal Faecal osmolalityosmolality can be used to assist with diagnosis of the cause of diarrhoea.







BloodBlood gasesgases





Blood GasesBlood Gases

Arterial - peripheral arterial bloodVenous - peripheral venous bloodMixed venous - pulmonary artery blood Capillary - scalp stick, finger stick



Because arterial blood is oxygenated blood flowing directly from the heart, analysis of arterial blood can determine the oxygen content and chemistry of the blood before it is used by the tissues.



Blood Gas AnalysisBlood Gas Analysis PO2 measured pH measured PCO2 measuredHCO3- CalculatedHb measured indirectly SO2 measured (functional, fractional) Electrolytes Na+, K+, Cl-, Ca++,Mg++Other Lactate, Glucose



Introduction to AcidIntroduction to Acid--Base Base ChemistryChemistry

AcidsAcids BasesBases BuffersBuffers Body fluid chemistryBody fluid chemistry

–– Bicarbonate ionsBicarbonate ions–– Relationship between carbon dioxide and Relationship between carbon dioxide and

hydrogen ionshydrogen ions–– Calculation of free hydrogen ion levelCalculation of free hydrogen ion level





Normal Blood pHNormal Blood pH Changes from normal blood pH (7.35 to Changes from normal blood pH (7.35 to

7.45) interfere with many normal functions 7.45) interfere with many normal functions by:by:–– Changing the shape of hormones and enzymes so Changing the shape of hormones and enzymes so

that they may no longer perform their normal that they may no longer perform their normal functionsfunctions

–– Changing the distribution of other electrolytes, Changing the distribution of other electrolytes, causing fluid and electrolyte imbalancescausing fluid and electrolyte imbalances



AcidAcid--BaseBase BalanceBalance

Both pulmonary and renal function act to compensate for disturbances in acid-base balance to maintain blood pH within normal ranges.





Buffers Buffers

First line of defenseFirst line of defense Two most common chemical buffersTwo most common chemical buffers

–– BicarbonateBicarbonate–– Phosphate Phosphate

Protein buffers Protein buffers



Respiratory AcidRespiratory Acid--Base Control Base Control Mechanisms Mechanisms

When chemical buffers alone cannot When chemical buffers alone cannot prevent changes in blood pH, the prevent changes in blood pH, the respiratory system is the second line of respiratory system is the second line of defense against changes.defense against changes.–– HyperventilationHyperventilation–– HypoventilationHypoventilation



Renal AcidRenal Acid--Base Control Base Control MechanismsMechanisms

The kidneys are the third line of defense The kidneys are the third line of defense against wide changes in body fluid pH.against wide changes in body fluid pH.–– Kidney movement of bicarbonateKidney movement of bicarbonate–– Formation of acidsFormation of acids–– Formation of ammoniumFormation of ammonium



Kidney buffer system



CompensationCompensation

The body attempts to correct changes in The body attempts to correct changes in blood pH.blood pH.

pH < 6.9 or > 7.8 is usually fatal.pH < 6.9 or > 7.8 is usually fatal. Respiratory system is sensitive to acidRespiratory system is sensitive to acid--

base changes; can begin compensation base changes; can begin compensation efforts within seconds.efforts within seconds.

Renal compensatory mechanisms are Renal compensatory mechanisms are much more powerful and result in rapid much more powerful and result in rapid changes in ECF composition.changes in ECF composition.



Respiratory CompensationRespiratory Compensation

Lungs compensate for acidLungs compensate for acid--base base imbalances of a metabolic origin.imbalances of a metabolic origin.

ExampleExample——prolonged running causes prolonged running causes buildup of lactic acid, hydrogen ion levels buildup of lactic acid, hydrogen ion levels in the ECF increase, pH drops; breathing in the ECF increase, pH drops; breathing is triggered in response to the increased is triggered in response to the increased carbon dioxide levels to bring the pH carbon dioxide levels to bring the pH level back to normal. level back to normal.



Renal CompensationRenal Compensation

A healthy kidney can correct or A healthy kidney can correct or compensate for changes in blood pH compensate for changes in blood pH when the respiratory system is either when the respiratory system is either overwhelmed or is not healthy.overwhelmed or is not healthy.



The Henderson-Hasselbalch equation represents a very important relationship.

The HCO3/CO2 buffer system is of physiologic importance because both the pulmonary and renal mechanisms for regulating pH work by adjusting this ratio.

The PCO2 can be modified rapidly by changes in respiratory ventilation, while plasma [HCO3

-] can be altered by regulating its excretion by the kidneys.



OxygenOxygen saturationsaturation –– SOSO22

Oxygen saturation of hemoglobin.

Assess the effectiveness of oxygen therapy.

Oxygen saturation is calculated from themeasured values of pH and pO2 .







Assessment of AcidAssessment of Acid--Base Base BalanceBalance

HistoryHistory Physical assessmentPhysical assessment Diagnostic assessmentDiagnostic assessment



BloodBlood gasesgases ––referencereference rangerange

25 – 4080 - 100pO2 (mm Hg)40 - 7096 - 97SO2 (%)

(- 2,5) – (+2,5)(- 2,5) – (+2,5)BE (mmol/L)25 – 2923 - 27T CO2 (mmol/L)41 - 5135 – 45pCO2 (mm Hg)24 – 2822 - 26HCO3 (mmol/L)

7,32 –7,427,35 – 7,45pHVenous bloodArterial blood



Sources of AcidsSources of Acids

Glucose metabolism Glucose metabolism Fat and protein metabolismFat and protein metabolism Incomplete metabolism of glucose and Incomplete metabolism of glucose and

fatsfats Destruction of cellsDestruction of cells



DisturbancesDisturbances ofof AcidAcid--BaseBaseBalanceBalance

Above ?Is the pH above or below 7,35 – 7,45?

Below ?

Alkalosis pH = 7,5

Acidosis pH = 7,2



Respiratory Respiratory effectseffects on pHon pH

Respiratory Alkalosis

CO2 excessive loss

Hyperventilation

CO2 excessiveretained

Hypoventilation

Respiratory Acidosis



MetabolicMetabolic effectseffects on pHon pH

Metabolic Alkalosis

Loss of H+VomitingExcessive AntacidIntake

Metabolic Acidosis

Excess of H+Diabetic

KetoacidosisRenal failure



AcidosisAcidosis Arterial blood pH level < 7.35Arterial blood pH level < 7.35 Causes: metabolic problems, respiratory Causes: metabolic problems, respiratory

problems, or bothproblems, or both Clients with problems that impair breathing Clients with problems that impair breathing

are at greatest riskare at greatest risk Major changes in body function: Major changes in body function:

imbalances of electrolytes, especially imbalances of electrolytes, especially potassiumpotassium



Metabolic AcidosisMetabolic Acidosis

Overproduction of Overproduction of hydrogen ionshydrogen ions

UndereliminationUnderelimination of of hydrogen ionshydrogen ions

Underproduction of Underproduction of bicarbonate ionsbicarbonate ions

OvereliminationOverelimination of of bicarbonate ionsbicarbonate ions



Respiratory AcidosisRespiratory Acidosis

Respiratory acidosis Respiratory acidosis results from:results from:–– Impaired respiratory Impaired respiratory

function that reduces function that reduces the exchange of the exchange of oxygen and carbon oxygen and carbon dioxidedioxide

–– Retention of carbon Retention of carbon dioxide that causes dioxide that causes increased production increased production of free hydrogen ionsof free hydrogen ions



Causes of Respiratory Causes of Respiratory AcidosisAcidosis

Respiratory depressionRespiratory depression–– Chemical depressionChemical depression–– Physical depressionPhysical depression

Inadequate chest expansionInadequate chest expansion–– Skeletal problemsSkeletal problems–– Respiratory muscle weaknessRespiratory muscle weakness–– External conditionsExternal conditions–– Airway obstructionAirway obstruction–– Reduced alveolarReduced alveolar--capillary diffusioncapillary diffusion



Interventions for AcidosisInterventions for Acidosis

Correct the underlying problem.Correct the underlying problem. Increase aerobic metabolism.Increase aerobic metabolism. Monitor for changes.Monitor for changes.



Interventions for Metabolic Interventions for Metabolic AcidosisAcidosis

HydrationHydration Drugs to control or treat the problem Drugs to control or treat the problem

causing the acidosiscausing the acidosis Respiratory acidosisRespiratory acidosis——maintain a patent maintain a patent

airway and enhance gas exchangeairway and enhance gas exchange–– Drug therapy: bronchodilators; Drug therapy: bronchodilators; mucolyticsmucolytics–– Oxygen therapy, pulmonary hygiene, ventilation Oxygen therapy, pulmonary hygiene, ventilation

supportsupport



AlkalosisAlkalosis

Arterial blood pH is > 7.45.Arterial blood pH is > 7.45. AcidAcid--base balance of the blood is base balance of the blood is

disturbed by an excess of bases, especially disturbed by an excess of bases, especially bicarbonate.bicarbonate.

Problems of alkalosis are serious and Problems of alkalosis are serious and potentially life threatening.potentially life threatening.



Metabolic AlkalosisMetabolic Alkalosis

Base excess results from excessive intake Base excess results from excessive intake of bicarbonates, carbonates, acetates, of bicarbonates, carbonates, acetates, citrates, and lactates.citrates, and lactates.

Acid deficit is caused by disease processes Acid deficit is caused by disease processes or medical treatments, or by prolonged or medical treatments, or by prolonged vomiting, excess vomiting, excess cortisolcortisol, or , or hyperaldosteronismhyperaldosteronism..





Metabolic AlkalosisMetabolic Alkalosis

The hallmark is an increased bicarbonate The hallmark is an increased bicarbonate level with a rising partial pressure of level with a rising partial pressure of arterial carbon dioxide.arterial carbon dioxide.

Serum potassium level decreases. Serum potassium level decreases. Calcium binding increases and Calcium binding increases and

hypocalcemiahypocalcemia results.results. Most of the serious problems are caused Most of the serious problems are caused

by the resulting by the resulting hypocalcemiahypocalcemia..



Respiratory AlkalosisRespiratory Alkalosis

Excessive loss of carbon dioxide through Excessive loss of carbon dioxide through hyperventilationhyperventilation

Anxiety, fear, or improper settings on Anxiety, fear, or improper settings on mechanical ventilators causing mechanical ventilators causing hyperventilationhyperventilation

Direct stimulation of central respiratory Direct stimulation of central respiratory center from fever, metabolic acidosis, center from fever, metabolic acidosis, central nervous system lesions, and central nervous system lesions, and drugs, also causing hyperventilationdrugs, also causing hyperventilation





Respiratory AlkalosisRespiratory Alkalosis

Classic profile:Classic profile:–– Reduced bicarbonate levelReduced bicarbonate level–– Low pressure of arterial carbon dioxide Low pressure of arterial carbon dioxide

Low serum potassium level Low serum potassium level Low serum calcium levelLow serum calcium level



Interpreting an arterial blood gas result:1. Determine whether the sample is arterial or venous

Saturation > 88% = Arterial< 88% = Mixed, Venous, Pulmonary Disease, etc.

2. Determine the acid/base status of the patientDetermine whether the sample is acidotic, alkalotic, or normal (pH)

Determine whether the pCO2 is normal or abnormal Determine whether the HCO3 is normal or abnormal

Determine whether the primary problem is metabolic or respiratory Determine whether compensation is occurring

Assess the ventilatory status (PaCO2) Hyperventilating? (Decreased PaCO2)Hypoventilating? (Increased PaCO2)

Normal ventilation?







ExamplesExamples

95-100% (on air)92%95%95%98%SaO2(air)+/-2 mmol/L-9-14+10+17BE

22-26 mmol/L19123348SB11.3-14 kPa9.014.08.511.6pO2

4.7-6.0 kPa4.95.08.66.0pCO2

7.35-7.457.267.157.297.48pH

Normal ValuesPatient Results



ExamplesExamples

-915.212.17.26.95

+/-2 mmol/L+8-9+10-9BE22-26 mmol/L34.915.23224.1SB11.3-14 kPa8.312.113.513.8pO2

4.7-6.0 kPa9.127.25.82.95pCO2

7.35-7.457.317.157.57.5pH

Normal ValuesPatient Results



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Water, Electrolyteand Acid-BaseBalance · 2018-02-18 · Water, Electrolyteand Acid-BaseBalance You created this PDF from an application that is not licensed to print to novaPDF printer