Acid BaseBalance

8/11/2019 Acid BaseBalance

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Acid-Base Balance


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Acids & Bases

Normal functioning body requires a balance

between acids and bases

Acid-base balance is a dynamic relationship

which reflects the concentration of

hydrogen ions (H+) in the body.

Chemical reactions occur in the body only

when these substances are in balance


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Free H+ constantly being produced & generated

from carbonic acid (H2CO3)

Free H+ determines pH

Chemical reactions depend on pH

Accelerated

Severly depressed, stopped Chemical reactions depend on enzymes, which are

proteins that act as catalysts, that are easily

destroyed, denatured, in an abnormal pH situation

Deactivated


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Acids

Releases H+

Electrolytes that dissociate into (H+) and an

anion Amount of H+ in a solution determines

acidity

Predominantly carbonic acid (H2CO3)produced from CO2


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Acid Sources

1. Cellular metabolism of glucose,

glycolosis, that produces CO2

2. Diet 50-100 mEq of acid is consumeddaily


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CO2 + H2O = (H2CO3) as an aciddissociates (HCO3-) + free H+

Free H+ must be neutralized to maintainnormal pH

Hgb in RBC + H+ carried to lungs

HCO3- diffuses out of RBC creating acharge and another anion must move intothe cell to maintain a neutral state

Cl- shift


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HCO3-, bicarbonate, + Na+ is transported

by circulation to lungs as NaHCO3 Na+ leaves bicarb combines back with H+


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Bases

Accepts H+

Substances that combine with H+

Usually contain OH- (hydroxyl ion)

Dissociates into:

(element) + (OH-)

Predominantlybicarbonate (HCO3-)

produced from (H2CO3)


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(Na+) + (Cl-) combine to form a salt:

HCL + NaOH > H2O + NaCL

In a neutralization reaction, an acid

combines with a base to form a salt andH2O


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ACID-BASE BALANCE

Definitions

Acid

: a proton, or hydrogen ion donor Base: a proton, or hydrogen ion receiver


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Acid & Base

Weak or strong depending on the ability to

dissociate

Usually occur in pairs

two sides of the same coin

Acid/ base depending on H+


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pH

Unit of measurement that indicates how

many (H+) are in a solution Inversely proportionate, opposite of (H+)

Acid releases H+, > present

Decrease pH or acidosis

Base takes H+, < present

Increase pH or alkalosis


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Scale 0-14

Midpoint- 7.0 # (H+) = # (OH-) in pure H2O

pH < 7 indicates more (H+) acidic

pH > 7 indicates less (H+) alkalotic

Each unit represents a change 10X in (H+)

1 unit = 10x

2 units = 100x


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pH of Body Fluids

Gastric contents

1- 4

Blood

7.35-7.45

A var iation of 0.4 in either directioncan be fatal


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Henderson-Hasselbach Equation

Determines normal pH in the bloodstream

Determined byRATIO of base:acid not

amount

Bicarbonate: carbonic acid

HCO3-:H2CO3

Levels may be abnormal and ratio may benormal

Normal pH ratio 20:1


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Bicarbonate buffer system.


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BODY REGULATION OF ACID-BASE

BALANCE

The body constantly produces acids through

metabolism

These acids must be constantly eliminated fromthe body

Three systems perform this task

Buffer systemRespiratory system

Renal system


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Buffer

Chemical substance that prevents large

changes in pH

A substance capable of accepting anddonating H+ ions

the CARBONIC ACID/BICARBONATE

(H2CO3/HCO3-) system is the principlebuffer system used by the body

Removes excess H+

Antacid combines with hydrochloric acid

Donates H+


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BUFFER SYSTEM

The fastest performer, works in seconds

Temporary solution

Bicarbonate ions combine with excess hydrogenions to form carbonic acid in a dynamic

relationship

HCO3 + H+ H2CO3


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buffering is the first defense against

changes in acid-base balance

bicarbonate buffer system is the most

important because there is a higher

concentration of HCO3- in the extra cellular

fluid than other buffers

ability of the body to regulate HCO3


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BUFFER SYSTEM

For every molecule of carbonic acid, there are 20

molecules of bicarbonate Any change in the this 20:1 ratio is immediately

corrected to maintain pH

An increase H+ causes an increase in H2CO3

A decrease in H+ causes a decrease in H2CO3


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BUFFER SYSTEM

Carbonic acid is a weak, volatile acid which must

be eliminated

The enzyme carbonic anhydrase causes thecarbonic acid to convert to carbon dioxide and

water

The CO2 and the H2O are easily eliminated by the

lungs and kidneys

The system also works in reverse


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Phosphate Buffer Pair

H2PO4- and HPO4

Found in cells concentrated in the tubules of

the kidneys because phosphate is eliminated

in the kidneys

Strong acids buffered in the kidney


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RESPIRATORY SYSTEM

Works in 3-12 minutes

Hyperventilation stimulated by an increase pCO2

The lungs eliminate excess CO2 by increasingrespirations, causing a decrease in H+ and an

increase in pH

The lungs can retain more CO2 by slowingrespirations, causing an increase in H+ and a

decrease in pH


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RENAL SYSTEM

Can take hours to days to work

Eliminates H+ in the urine and conserves HCO3-

Increase CO2 results in increased H+ secretion

Kidneys can retain bicarbonate ion, causing a

decrease in H+ and an increase in pH

Kidneys can excrete bicarbonate ion, causing anincrease in H+ and a decrease in pH

Most effective


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Acid-Base Derangements

Respiratory acidosis-caused by

retention of CO2

Respiratory alkalosis-caused by

increased respiration and excessive

elimination of CO2


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RESPIRATORY ACIDOSIS

Lower than normal pH caused by retention of CO2

(Alveolar hypoventilation)

Pulmonary system unable to rid the body of enoughCO2

Results in decreased ventilations due to problems

in lungs or respiratory center of the brain

CO2 is increased and the pH is decreased

Treatment is aimed at improving ventilations


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What Happens?

Patient hypoventilates, carbon dioxide

builds up in the bloodstream and the pH

drops below normal.

Compensation

Kidneys retain more bicarbonate which raises

the pH level.


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Respiratory acidosis.

3

H2CO3

16

HCO3


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Causes!

Neuromuscular problems

Depression of respiratory centers in the

brain

Lung disease

Airway obstruction


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Respiratory Acidosis

Caused by retention of carbon

dioxide, leading to an increasein PCO2

Treatment


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Hypoventilating

Decrease ventilations

PaCO2H2CO3


pH


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Respiratory alkalosis.

25HCO3-

1

H2CO3


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Increase

ventilation

H2CO3

PaCO2

Respiratory Alkalosis

pH


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RESPIRATORY ALKALOSIS

Higher than normal pH from increasedrespiration and excessive elimination of

CO2Sudden increase in ventilation (Alveolar

hyperventilation)

Can result from anxiety or following ascentto high altitude

CO2 is decreased and pH is increased

Treatment is aimed at increasing CO2 level

by having patient rebreath CO2

Wh H ?


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What Happens?

When pulmonary ventilation increasesabove the needed amount, excessive

amounts of CO2 are exhaled. PaCO2 fallsbelow normal and a reduction of carbonicacid leads to a rise in the pH

Defense

Hydrogen ions are pulled out of the cells andinto the bloodstream. Hydrogen ions combinewith bicarbonate ions to forms carbonic acidwhich lowers the pH

C !


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Causes!

Hyperventilation with anxiety

Pain

Drugs (nicotine, xanthines)

Hypermetabolic states

Fever, sepsis, and liver failure


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Acid-Base Derangements

Metabolic alkalosis-alkalinityresulting from diuresis, vomiting,or over-consumption of sodium

bicarbonate

Metabolic acidosis-acidityresulting from vomiting, diarrhea,diabetes, or medication


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METABOLIC ACIDOSIS

Lower than normal pH due to increase productionof metabolic acids

Can also result from diarrhea, vomiting, diabetes,medications (aspirin)

pH is decreased and CO2 level is normal

Treatment is aimed at improving ventilations to

eliminate CO2 Sodium bicarbonate may be administered on rare

occasions


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Metabolic Acidosis

Four common forms of metabolic acidosis

Lactic acidosis

Diabetic ketoacidosis (DKA)Acidosis resulting from renal failure

Acidosis from ingestion of toxins

Treatment

b l d


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Metabolic acidosis.

Wh t h ?


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What happens?

There is a loss of bicarbonate from extracellular

fluid, accumulation of metabolic acids, or a

combination of both. Gain acids, lose bases.

C !


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Causes!

Diabetes mellitus

Chronic alcoholism

Severe malnutrition or starvation Poor dietary intake of carbohydrates

Other factors

Lactic acids can make acidosis worse and can occur

secondarily to shock, heart failure, pulmonary disease,hepatic disorders, seizures, or strenuous exercise.


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METABOLIC ALKALOSIS

Higher than normal pH caused by excessive

elimination of H+

pH is increased and CO2 remains normal Treatment is aimed at correcting underlying cause


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Metabolic Alkalosis (rare)

Causes

Loss of hydrogenions (primarily from the

stomach)

Ingestion of large amounts of absorbable base

sodium bicarbonate or calcium carbonate

Excessive IV administration of alkaliDiureticuse

Treatment


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C !


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Causes!

Caused by increased diarrhea, prolonged

vomiting, overdosing on antacids

Also associated with hypokalemiaDepleted potassium stores due to excessive

urination or vomiting


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COMBINATIONS

Usually both metabolic and respiratorycomponents are present

Only arterial blood gasses can accurately diagnosethe problem


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What condition am I?

20:1 ratio

Normal pH

What would the pH be?

7.35-7.45


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Mixed Acid-Base Disturbances

Many conditions, including various forms

of shock, may produce mixed abnormalities

of acid-base regulation

Acid Base Balance


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Acid Base Balance

Compensated

HCO3 PCO2 pH

Metabolic Acidosis

RespiratoryAcidosis

Acid Base Balance


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Acid Base Balance

Compensated HCO3 PCO2 pH

MetabolicAlkalosis

RespiratoryAlkalosis


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ABGs

Blood Gases

oxygenation and acid-base status is

determined by measurement of ABGs arterial blood measured as opposed to

venous blood because it represents amixture from all parts of the body

pH and pCO2 are measured directly,HCO3- and O2 saturation are calculated


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Normal Blood Gas Values

pH:

7.40 (7.35-7.45)

pO2: 80-100mmHg

pCO2:

35-45mmHg

SaO2:

>/= 95%

HCO3:

22-26 mmol/L

Acid Base Evaluations : THE 5


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Acid-Base Evaluations : THE 5

STEP APPROACH

1) Look at the pH - identify the type of

emia/ osis

7.45alkalemia, alkalosis

2) Look at the HCO3


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2) Look at the HCO3

- and CO2 values

Determine which process:

either metabolic (HCO3-)

respiratory (pCO2)

is most in keeping with the direction of the

emia


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Metabolic Acidosis

pH

decreased

HCO3-

decreased


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pH

decreased

pCo2

increased


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pH

increased

pCO2

decreased

3) Determine if compensation has


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3) Determine if compensation has

occurred

Kidneys compensate in respiratory

disorders

12-24 hours to exert a noticeable difference

Lungs compensate in metabolic disorders

Within minutes


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Respiratory acidosis- increased HCO3-,

reabsorption by kidneys result in increased

serum HCO3-

Respiratory alkalosis- decreased HCO3-,

reabsorption by kidneys result in decreased

HCO3-


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Metabolic acidosis

HYPERventilation causes decrease pCO2 Metabolic alkalosis

HYPOventilation causes increase pCO2


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4) Calculate the anion gap

Anion gap is useful in determining the cause

of the acid-base disorder

increased AG is usually associated withmetabolic acidosis

AG = Na+ - (Cl- + HCO3-) normally

12 (8-16mmol/L)


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5) Look at the clinical picture!!!


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Decrease pH, increase CO2


Increase pH, decrease CO2

Metabolic Acidosis

Decrease pH, decrease HCO3-

Metabolic Alkalosis

Increase pH, increase HCO3-


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Mixed Acid Base Derangements

Normal pH

Abnormal CO2 / HCO3-


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Acid Base Practice

ABG Values pH =

PaCO2 =

HCO3 =

PaO2 =

Metabolic

Alkalosis

7.47

45

34

90


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Acid Base Practice

ABG Values pH =

PaCO2 =

HCO3 =

PaO2 =

Respiratory

Acidosis

7.24

66

22

75


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Acid Base Practice

Melissa is a 23 y/o female who is brought to

the ED because of a decrease LOC. Her

roommate found her with an empty bottle ofsecobarbital (Seconal) and a half bottle of

wine near her. Her roommate states that

Melissa has been depressed about her busyshifts. Her VS are:

HR-120 RR28 BP70/40 (next slide)


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Acid Base Practice

ABG Values pH =

PaCO2 =

HCO3 =

PaO2 =

Respiratory

Acidosis

7.20

65

26

45


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Acid Base Practice

ABG Values pH =

PaCO2 =

HCO3 =

PaO2 =

Respiratory

Alkalosis

7.56

30

24

104


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Acid Base Practice

ABG Values pH =

PaCO2 =

HCO3 =

PaO2 =

Respiratory

Acidosis

7.14

78

23

74


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Acid Base Practice

In route to the hospital with Rocky, his

respiratory effort showed some

improvement, and now your blood gasesreveal the following. (next slide)


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Acid Base Practice

ABG Values pH =

PaCO2 =

HCO3 =

PaO2 =

Metabolic

(respiratory)

Acidosis

7.25

41

17

79

Acid Base Practice


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Acid Base Practice

Donie is a 39 y/o who had an abdominalhysterectomy 2 days ago. She has had an

uncomplicated postoperative course and has been up

walking in his room twice. She is resting in bed

when she suddenly develops left chest pain that

increases with respirations. She describes of feeling

SOB and appears very anxious. VS: RR32/min

HR124 irregular, BP140/86 Temp 98.6 F


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Acid Base Practice

Robin is a 40 y/o male with a 20 hx ofalcohol abuse. He has been admitted to

hospitals numerous times over the past 4years for TX of jaundice, ascites, and otherproblems associated with hepaticdysfunction. Robin admits he has continued

drink heavily. He his lethargic andconfused. VS HR70, BP112/70, RR24/min, temp 99.9 F. (next slide)


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Acid Base Practice

ABG Values pH =

PaCO2 =

HCO3 =

PaO2 =

Respiratory

Alkalosis

7.46

21

25

82


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Acid Base Practice

Chris is a 28 y/o male who, when found at

home, was arousable but very lethargic with

deep respirations. An empty bottle of ASA

was found in the bathroom. His classmates

state that he has been upset about doing his

paramedic clinicals. They stated they dont

know of prior incidence of drug OD. VS: BP110/60, HR84, RR34/min with deep,

labored (Kussmaul respirations) (next slide)


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Acid Base Practice

ABG Values pH =

PaCO2 =

HCO3 =

PaO2 =

Respiratory

Alkalosis

7.49

14

22

96

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