acid-base homeostasis rashid

8/9/2019 Acid-base Homeostasis Rashid

1/44

Topic

Acid-Base HomeostasisBY

Rashid Hussain

Post R.N Bsc Nursing

Khyber Medical University

Post Graduate Nursing College Hayatabad

Peshawar. 11


2/44

OBJECTIVESOBJECTIVES

At the end of the session the learner will be ableAt the end of the session the learner will be ableto:to:

Overview the Acid-Base Homeostasis.Overview the Acid-Base Homeostasis.

Describe acids and bases and types acids in theDescribe acids and bases and types acids in the

body.body.

Explain different types of Acid-Base balance systems.Explain different types of Acid-Base balance systems.

Discuss Acidosis and Alkalosis.Discuss Acidosis and Alkalosis.

22


3/44

Acid-Base HomeostasisAcid-Base HomeostasisAcid-base homeostasisAcid-base homeostasis is the part of human homeostasisis the part of human homeostasisconcerning the proper balance between acids and bases, inconcerning the proper balance between acids and bases, in

other words, the pH. The body is very sensitive to its pH level,other words, the pH. The body is very sensitive to its pH level,

so strong mechanisms exist to maintain it. Outside theso strong mechanisms exist to maintain it. Outside the

acceptable range of pH, proteins are denatured and digested,acceptable range of pH, proteins are denatured and digested,enzymes lose their ability to function, and death may occur.enzymes lose their ability to function, and death may occur.

acid-base balanceacid-base balance a normal balance between production anda normal balance between production and

excretion of acid or alkali by the body, resulting in a stableexcretion of acid or alkali by the body, resulting in a stableconcentration of H+ in body fluids.concentration of H+ in body fluids.

33


4/44

ContiConti

When the body is in a state of acid-base balance, it maintains a stableWhen the body is in a state of acid-base balance, it maintains a stable

hydrogen ion concentration in body fluids; specifically, blood pHhydrogen ion concentration in body fluids; specifically, blood pH

remains relatively constant between 7.35 and 7.45remains relatively constant between 7.35 and 7.45

44


5/44

ACIDSACIDS

Molecules that canMolecules that canrelease Hrelease H ++ in solutionin solutioncalled acidscalled acidsHClHCl HH++ + Cl+ Cl --

HH22 CoCo 33 HCOHCO 33 -- + H+ H ++ Acid may be strongAcid may be strongacid which completelyacid which completelydissociatesdissociatesWhile weak acids haveWhile weak acids haveless tendency toless tendency todissociatedissociate

Molecule that accept H+ calledMolecule that accept H+ calledbasebaseHCO3- + H+ ---> H2CO3HCO3- + H+ ---> H2CO3HPO4 - + H+HPO4 - + H+ H2PO4H2PO4Bases may be strong or weakBases may be strong or weak

Strong base reacts rapidly andStrong base reacts rapidly andstrongly with H+ (HCO3-)strongly with H+ (HCO3-)Proteins also function as baseProteins also function as baseHemoglobinHemoglobin Hb + H+Hb + H+ HHbHHb

55

BASESBASES


6/44

There are two types of acidsThere are two types of acidsformed:formed:

Volatile acidsVolatile acids can becan beexcreted from the body asexcreted from the body asgas. Carbonic acid producedgas. Carbonic acid producedby the hydration of carbonby the hydration of carbondioxide is a volatile aciddioxide is a volatile acid

Normally carbon dioxide isNormally carbon dioxide isexcreted by the lungs as fastexcreted by the lungs as fastas metabolism produces it, soas metabolism produces it, socarbonic acid is not allowed tocarbonic acid is not allowed to

accumulate and alter pHaccumulate and alter pH

Non-Volatile acidsNon-Volatile acids Cannot beCannot beeliminated by the lungs andeliminated by the lungs andmust be eliminated by themust be eliminated by thekidneyskidneys

All metabolic acids exceptAll metabolic acids exceptcarbolic are non-volatile acidscarbolic are non-volatile acids

These include sulfuric acid, These include sulfuric acid,phosphoric acid, lactic acid,phosphoric acid, lactic acid,ketoacids like acetoacetic acidketoacids like acetoacetic acidand beta hydroxybutyric acid,and beta hydroxybutyric acid,and small amounts of otherand small amounts of other

inorganic and organic acidsinorganic and organic acids

66


7/44

A Review of Important TermsA Review of Important TermsRelating to Acid-Base BalanceRelating to Acid-Base Balance

pH:pH: The negative exponent (negative log) of the The negative exponent (negative log) of thehydrogen ion concentration.hydrogen ion concentration.

Neutral:Neutral: A solution with a pH of 7, whichA solution with a pH of 7, whichcontains equal numbers of hydrogen andcontains equal numbers of hydrogen andhydroxyl ions.hydroxyl ions.

Acidic:Acidic: A solution with a pH below 7, in whichA solution with a pH below 7, in whichhydrogen Hhydrogen H ++ ions predominate.ions predominate.

Basic or Alkaline:Basic or Alkaline: A solution with a pH above 7,A solution with a pH above 7,in which hydroxyl OH- ions predominate.in which hydroxyl OH- ions predominate.

77


8/44

ContiConti

Acids:Acids: A substance that dissociates to release hydrogenA substance that dissociates to release hydrogenions, shifting the pH towards acidity.ions, shifting the pH towards acidity.

Base:Base: A substance that dissociates to release hydroxylA substance that dissociates to release hydroxylions or tie up hydrogen ions and shifting the pH towardsions or tie up hydrogen ions and shifting the pH towards

alkalinityalkalinity

Salt:Salt: An ionic compound consisting of a cation other thanAn ionic compound consisting of a cation other thanhydrogen ions and anion other then a hydroxide ion.hydrogen ions and anion other then a hydroxide ion.

Buffers:Buffers: A substance that tends to oppose changes inA substance that tends to oppose changes inthe pH of solution by removing or replacing H+ ions in thethe pH of solution by removing or replacing H+ ions in thebody fluids, Buffers maintain pH within normal limitsbody fluids, Buffers maintain pH within normal limits(7.35-7.45)(7.35-7.45)

88


9/44

99

Acid Base BalanceAcid Base Balance

Three primary system to maintain H Three primary system to maintain H ++ concentration:concentration:

Chemical Buffers:Chemical Buffers: - chemical system, act- chemical system, act

with in seconds to neutralize Hwith in seconds to neutralize H ++ excessexcess

Respiratory SystemRespiratory System Activate with in Activate with inminutes to remove COminutes to remove CO 22

KidneysKidneys :- response slowly to remove acid or:- response slowly to remove acid oralkali from body, only way to eliminate acidsalkali from body, only way to eliminate acidsother than H2CO3. (minutes to hours)other than H2CO3. (minutes to hours)


10/44

Buffer Systems in Body FluidsBuffer Systems in Body Fluids

1010


11/44

3 Major Chemical Buffer3 Major Chemical BufferSystemsSystems

Protein buffer systems:Protein buffer systems: Help regulate pH in ECF and ICFHelp regulate pH in ECF and ICF Interact extensively with other bufferInteract extensively with other buffer

systemssystems

Carbonic acidbicarbonate bufferCarbonic acidbicarbonate buffersystem:system:

Most important in ECFMost important in ECF

Phosphate buffer system:Phosphate buffer system: Buffers pH of ICF and urineBuffers pH of ICF and urine

1111


12/44

1: Protein Buffer system1: Protein Buffer systemIs the most abundant buffer in intracellular fluid and blood plasma:Is the most abundant buffer in intracellular fluid and blood plasma:

a)a) Albumin in the blood plasma.Albumin in the blood plasma.Protein are composed of amino acids, that contain at leastProtein are composed of amino acids, that contain at leastone carboxyl group (--COOH) an at least one amino groupone carboxyl group (--COOH) an at least one amino group(NH(NH 22 ).).

The free carboxyl group at one end of a protein acts like The free carboxyl group at one end of a protein acts likean acid by releasing H+ ions, when pH rises.an acid by releasing H+ ions, when pH rises.

The free amino group at the other en of a protein can act The free amino group at the other en of a protein can actas a base by combining H+, when pH falls.as a base by combining H+, when pH falls.

So protein can buffer both acids and bases.So protein can buffer both acids and bases.

1212


13/44

Amino Acids inAmino Acids inProtein Buffer SystemsProtein Buffer Systems

1313


14/44

b) Hemoglobin within RBCs.b) Hemoglobin within RBCs.

As blood flow through the systemic capillaries,As blood flow through the systemic capillaries,COCO 22 passes from tissues cells into RBCs, here itpasses from tissues cells into RBCs, here itcombine with Hcombine with H 22 O to form HO to form H 22 COCO 33 ,,

Once formed HOnce formed H 22 COCO 33 dissociate into H+ and HCO3-dissociate into H+ and HCO3-

At the same time CO2 entering the RBCs and O2At the same time CO2 entering the RBCs and O2to the tissue cells.to the tissue cells.

Deoxyhemoglobin picks up most of the H+,Deoxyhemoglobin picks up most of the H+,written as Hb-H.written as Hb-H.

1414


15/44

1515

CARBON DIOXIDE DIFFUSIONCARBON DIOXIDE DIFFUSION

COCO 22

COCO 22

Red Blood CellRed Blood CellSystemic CirculationSystemic Circulation

COCO 22 HH22 OO HH++

HCOHCO 33--

++ ++HCOHCO 33 --

ClCl --

(Chloride Shift)(Chloride Shift)

COCO 22 diffuses into plasma and into RBC Withindiffuses into plasma and into RBC Within

RBC, the hydration of CORBC, the hydration of CO 22 is catalyzed byis catalyzed by

carbonic anhydrasecarbonic anhydraseBicarbonate thus formed diffuses into plasmaBicarbonate thus formed diffuses into plasma

carboniccarbonicanhydraseanhydrase

TissuesTissues

PlasmaPlasma


16/44

1616

CARBON DIOXIDE DIFFUSIONCARBON DIOXIDE DIFFUSION

COCO 22

Red Blood CellRed Blood CellSystemic CirculationSystemic Circulation

HH22 OO

HH++

HCOHCO 33--

carboniccarbonicanhydraseanhydrase

PlasmaPlasma

COCO 22 COCO 22 COCO 22 COCO 22 COCO 22 COCO 22COCO 22

Click for CarbonDioxide diffusion

++ ++

TissuesTissues

HH++

ClCl --

HbHbHH++ is buffered byis buffered by

HemoglobinHemoglobin


17/44


18/44

1818

BICARBONATE DIFFUSIONBICARBONATE DIFFUSION

Red Blood CellRed Blood Cell Pulmonary CirculationPulmonary Circulation

COCO 22 HH22 OO

HH++

++ ++ HCOHCO 33 --

ClCl --

AlveolusAlveolus

PlasmaPlasma

COCO 22

COCO 22 HH22 OO


19/44

2: Bicarbonate-Carbonic Acid2: Bicarbonate-Carbonic Acid

Buffer SystemBuffer SystemBicarbonate buffer system is the mostBicarbonate buffer system is the mostpowerful ECF bufferpowerful ECF buffer

Blood Buffer systems act instantaneouslyBlood Buffer systems act instantaneously

and thus constitute the bodys first line of and thus constitute the bodys first line of

defense against acid-base imbalancedefense against acid-base imbalance

HCOHCO 33-- and COand CO 22 are regulated by kidney andare regulated by kidney and

lunglung

1919

2 Bi b C b i A id2 Bi b C b i A id


20/44

2: Bicarbonate-Carbonic Acid2: Bicarbonate-Carbonic AcidBuffer SystemBuffer System

Is based on the concentration of HCOIs based on the concentration of HCO 33 - ions, which- ions, which

acts as a weak base and Hacts as a weak base and H 22 COCO 3,3, which acts as weakwhich acts as weakacid.acid.

HCOHCO 33 - is a significant anion in both ICFs & ECFs- is a significant anion in both ICFs & ECFs

If there is an excess of If there is an excess of HH++ ions, the HCOions, the HCO 33 - cancanfunction as weak base an remove the excess Hfunction as weak base an remove the excess H +.+.

HH++ + HCO+ HCO 33 -- HH22 COCO 33 COCO 22 ++ HH22 OO

Then H Then H 22 COCO 33 dissociate into water and carbon dioxidedissociate into water and carbon dioxide

and CO2 is exhaled from the lungs.and CO2 is exhaled from the lungs.

Conversely, if there is a shortage of Conversely, if there is a shortage of HH+,+, the Hthe H 22 COCO 33 cancanfunction as a weak acid and providefunction as a weak acid and provide HH++ ..

HH

22COCO

33 HCOHCO

33

-- + H+ H ++ 2020


21/44

2121

3: Phosphate buffer system3: Phosphate buffer system

Main elements are HMain elements are H 22 POPO 44 -- and HPOand HPO 44 ==

Buffer in renal tubular fluid and ICF.Buffer in renal tubular fluid and ICF.

When HCl is added to bufferWhen HCl is added to bufferHClHCl +Na+Na 22 HPOHPO 44 NaHNaH 22 POPO 44 + NaCl+ NaCl

Strong acid HCl is replaced by weak acidStrong acid HCl is replaced by weak acidNaHNaH 22 POPO 44 and change in pH minimizedand change in pH minimized


22/44

2222

Phosphate BufferPhosphate Buffer

Concentration of Phosphate is less in ECFConcentration of Phosphate is less in ECF

So Phosphate buffer system act much less inSo Phosphate buffer system act much less in

ECF.ECF.

Main site of action are ICF and renal tubularMain site of action are ICF and renal tubular

fluids, where Phosphate is in abundant andfluids, where Phosphate is in abundant and

pH is less as compared to ECFpH is less as compared to ECF


23/44

2323

Respiratory regulation of AcidRespiratory regulation of Acidbase balancebase balance

Lungs 2Lungs 2ndnd

line of defense in maintaining acid base balanceline of defense in maintaining acid base balanceCOCO 22 continuously forming in cellular metabolismcontinuously forming in cellular metabolism

It than diffuses into interstitial fluid and blood, transported toIt than diffuses into interstitial fluid and blood, transported to

lungs and out of bodylungs and out of bodyIncreased ventilation decreases COIncreased ventilation decreases CO 22 and reduces Hand reduces H ++ ,,

decreased ventilation increases COdecreased ventilation increases CO 22 and Hand H ++


24/44

2424

Respiratory BufferRespiratory Buffer

Normal CONormal CO 22 in ECF is 1-2 ml/L equals to PCOin ECF is 1-2 ml/L equals to PCO 22 of 40of 40mmHgmmHg

Change in pulmonary ventilation or rate of COChange in pulmonary ventilation or rate of CO 22

formation can change ECF PCOformation can change ECF PCO 22

So rate of metabolic formation of COSo rate of metabolic formation of CO 22 decreases,decreases,

Rate of ventilation decreasesRate of ventilation decreases

Rate of metabolic formation of CORate of metabolic formation of CO 22 increases, rate of increases, rate of

ventilation increasesventilation increases


25/44

2525

Effect of HEffect of H ++ Concentration onConcentration onAlveolar VentilationAlveolar Ventilation

Respiratory compensation in not as effective inRespiratory compensation in not as effective in

case of increase in pH, as it is effective in reductioncase of increase in pH, as it is effective in reduction

in pH.in pH.

If pH decreases from 7.4 to 7.0, alveolar ventilationIf pH decreases from 7.4 to 7.0, alveolar ventilation

rate will increase 04-05 times.rate will increase 04-05 times.

Change in alveolar ventilation rate will be more inChange in alveolar ventilation rate will be more incase of increase in Hcase of increase in H ++ as compared to decrease inas compared to decrease in

HH++


26/44

2626


Over all buffering power of respiratory system isOver all buffering power of respiratory system is

one to two times as great as the buffering power of one to two times as great as the buffering power of

all other chemical buffers in ECFall other chemical buffers in ECF

HH++ concentration is regulated by negative feed backconcentration is regulated by negative feed back

with alveolar ventilationwith alveolar ventilation


27/44

2727


Respiratory control of pH is only effectiveRespiratory control of pH is only effectiveup to 50% -70%up to 50% -70%

If pH is suddenly falls from 7.4 to 7.0If pH is suddenly falls from 7.4 to 7.0respiratory system will bring it up to 7.2 torespiratory system will bring it up to 7.2 to7.37.3

Response occur in 3-12 minutesResponse occur in 3-12 minutes


28/44

2828

ACIDOSISACIDOSIS

Acidosis is aAcidosis is a decreasedecrease in pH below 7.35in pH below 7.35

Which means a relative increase of Which means a relative increase of HH ++ ionsions

pH may fall as low as 7.0 without irreversible damagepH may fall as low as 7.0 without irreversible damage

but any fall less than 7.0 is usually fatalbut any fall less than 7.0 is usually fatal

H+ pH


29/44

2929

ACIDOSISACIDOSIS May be caused by:May be caused by:

An increase inAn increase in HH 22 COCO 33

A decrease inA decrease in HCOHCO 33 --

Both lead to a decrease in the ratio of 20:1Both lead to a decrease in the ratio of 20:1

H2CO 3 HCO 3 -


30/44

3030

ALKALOSISALKALOSIS

Alkalosis is aAlkalosis is a increaseincrease in pH above 7.45in pH above 7.45

Which means a relative decrease of Which means a relative decrease of HH ++ ionsions

pH may rise as high as 8.0 without irreversiblepH may rise as high as 8.0 without irreversible

damage but any rise more than 8.0 is usually fataldamage but any rise more than 8.0 is usually fatal

H+ pH


31/44

3131

ALKALOSISALKALOSIS May be caused by:May be caused by:

An increase inAn increase in HCOHCO 33 --

A decrease inA decrease in HH 22 COCO 33

Both lead to a increase in the ratio of 20:1Both lead to a increase in the ratio of 20:1

H2CO 3 HCO 3 -


32/44

3232


33/44

Acid-Base Imbalances

pH < 7.35 acidosispH > 7.45 alkalosis

3333


34/44

3434

ACIDOSISACIDOSISdecreasedremoval of CO 2 from

lungs

failure of kidneys to

excrete

acids

metabolicacid

productionof keto acids

absorption of metabolic acids

from GI tract

prolongeddiarrhea

accumulationof CO 2 in blood

accumulationof acid in blood

excessive lossof NaHCO 3

from blood

metabolicacidosis

deepvomiting

from

GI tract

kidneydisease

(uremia)

increase inplasma H +

concentration

depression of

nervous system

accumulationof CO 2 in blood

accumulationof acid in blood

excessive lossof NaHCO 3

from blood

respiratoryacidosis

ALKALOSISALKALOSIS


35/44

3535

ALKALOSISALKALOSIS

respiratoryalkalosis

anxiety overdoseof certain

drugs

highaltitudes

prolongedvomiting

ingestion of excessive

alkaline drugs

excessaldosterone

hyperventilation

loss CO 2 andH

2CO

2from

loss of acid accumulationof base

metabolicalkalosis

decreasein plasma H +concentration

overexcitabilityof nervous

system

hyperventilationloss of CO 2 and

H2CO 3 from

blood

loss of acid accumulationof base


36/44

Normal Blood Gas ValuesNormal Blood Gas Values

pH 7.35 - 7.45pH 7.35 - 7.45

PCO2 - 35 45 mmHgPCO2 - 35 45 mmHg

HCO3 22 26 meq/literHCO3 22 26 meq/liter

PO2 90-100 mmHgPO2 90-100 mmHg

O2 Saturation 94-97%O2 Saturation 94-97%

BE base excess =BE base excess = ++ 2 meq/liter2 meq/liter3636


37/44

3737


38/44

3838

ACIDOSIS AND ALKALOSISACIDOSIS AND ALKALOSIS

Metabolic Acidosis:-Metabolic Acidosis:- Primary decrease in HCOPrimary decrease in HCO 33 --

Metabolic alkalosis:-Metabolic alkalosis:- Primary increase in HCOPrimary increase in HCO 33 --

Respiratory acidosis:-Respiratory acidosis:- Increase in PCOIncrease in PCO 22

RRespiratory Alkalosis:-espiratory Alkalosis:- Decrease in PCODecrease in PCO 22


39/44

3939


40/44


41/44


42/44

Dont see others doingbetter than you

Beat your own recordseveryday!!

Because success is afight between YOU and

YOURSELF


43/44

Victory is not the property of the brilliants

It is the crown for those whobelieve in hard work.

Winners never quitand quitters never wins


44/44

4444

acid-base homeostasis rashid

Documents