acid-base balance report

7/27/2019 Acid-base Balance Report

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ACIDBASE BALANCE


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Hydrogen Ion and pHImportance:

Membrane integrity Metabolic enzyme reactions

Concentration:

0.0000001 mg/L pH = power of hydrogen

pH = -log [H+] = 10 -7= pH 7.0


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Hydrogen Ion and pH

greater the H

+

= more acidic = lower pH lesser the H+ = more basic = higher pH

body fluid pH = 7.357.45 (narrow range)


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pHH+concentration


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Mechanisms for Regulation


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Regulation of Acid-Base Balance


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A. Buffer SystemsBUFFERS

absorb excessive hydrogen (H+) (acid) or

hydroxyl ion (OH-) (base)

contains salts of either weak acids or weakbases that either:

combine with H+when H+ increase in bodyfluids

release H+ when H+ decrease in body fluids


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3 MAJOR BUFFERS


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1. PO43-buffer system

Reaction:

HPO42- + H+ H2PO4

-

monohydrogen hydrogen dihydrogen

phosphate ion ion phosphate ion


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2. Proteins

amino acid side chains

contains:

Carboxyl group ( -COOH )

Amine group ( -NH2)


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Reaction:

-COO- + H+ -COOH

carboxyl hydrogen carboxyl

group ion group

-NH2 + H+ -NH3

amine group hydrogen ammoniumion group


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3. Bicarbonate (HCO3-)Reaction:

CO2 + H2O H2CO3 H+ + HCO3

-

carbon water carbonic hydrogen bicarbonate

dioxide acid ion ion


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B. Respiratory System

responds rapidly to a change in pHand function to bring the pH back to

its normal range


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C. Kidneys powerful regulatorof pH, but responds

more slowlythan does the respiratory

system

nephrons secretion of H+ into the urine

and reabsorption of bicarbonate directly

regulates pH


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Nephrons are Microscopic Tubules

That Form the UrineInsert fig 23-4


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ACIDOSIS and ALKALOSIS


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ACIDOSIS

pH falls below 7.35 major effect: CNS malfunctions

can become comatose


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ALKALOSIS

pH increases above 7.45 major effect: hyperexcitability of the

nervous system


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Respiratory Acidosis and Alkalosis

Respiratory acidosis Respiratory alkalosis

Increased PCO2Increased carbonic acid

Increased H+= low pH

(7.45)

Decreased bicarbonate


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Respiratory Acidosis

RISK FACTORS

Acute lung condition thatimpair alveolar gas

exchange (pneumonia,edema, aspiration, near-drowning)

Chronic lung disease(asthma, emphysema)

Overdose of narcotics orsedatives

Brain injury that affects therespiratory center

MANIFESTATIONS

Breathlessness, restlessnessand apprehension

Increased PR and RR,gradually becomesdepressed

Headache, dizziness

Confusion, LOC

Convulsions

Warm, flushed skin


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Respiratory Acidosis

Hypoventilation

Hypercapnia (PaCO2 )

pH blood

Hyperventilation Renal buffering

48-72 hours

Blow off CO2

Return the pH

to normal

Hydrogen (H+)

excretion

Bicarbonate

retention

Return pH to

normal

Co

mpensation

When hypoventilation causes hypercapnia, blood pH falls. If this state persists, respiratory acidosis results.Compensatory mechanisms can be initiated to return the pH to normal.


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Respiratory AlkalosisRISK FACTORS

Hyperventilation due to:

Extreme anxiety Elevated body

temperature

Overventilation with a

mechanical ventilator Hypoxia

Salicylate overdose

MANIFESTATIONS

Shortness of breath, chest

tightnessLight-headedness, numbness,

tingling of the extremities

Difficulty concentrating

Tremulousness, blurredvision


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Respiratory Alkalosis

Hyperventilation

Hypercapnia (PaCO2 )

pH blood

Hypoventilation Renal buffering

48-72 hours

Retain CO2

Return the pH

to normal

Hydrogen (H+)

retention

Bicarbonate

excretion

Return pH to

normal

Co

mpensation

When hyperventilation causes hypocapnia, the blood pH elevates. If this state persists, respiratory alkalosis results.

Compensation by the lungs and kidneys will usually be initiated to return the pH to normal.


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Metabolic Acidosis and

Alkalosis

Metabolic acidosis Metabolic alkalosis

Increased H+= low pH

(7.45)

Increased bicarbonate

Lighter breathing causes

increased PCO2


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Metabolic AcidosisRISK FACTORS

Conditions that nonvolatile

acids in the blood ( renalimpairment, DM,

starvation )

Conditions that bicarbonate

( prolonged diarrhea )Excessive infusion of

chloride-containing IV

fluids ( NaCl )

MANIFESTATIONS

Kussmauls respirations

Lethargy, confusionHeadache

Weakness

Anorexia, nausea, vomiting

and diarrhea


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Metabolic Acidosis

Loss of base or

Production of excess acid

serum pH

Hyperventilation Renal buffering

PaCO2

Serum pH

Hydrogen (H+)

excretion

Bicarbonate

retention

Co

mpensation

When base is lost or acid is produced excessively, the serum pH falls. If this state persists, metabolic acidosis results.

Compensatory mechanisms will usually be initiated to attempt to return the serum pH toward normal.

Serum pH


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Metabolic AlkalosisRISK FACTORSExcessive acid losses due to:

Vomiting

Gastric suction

Excessive use of K-losing diuretics

Excessive adrenal corticoidhormones due to:

Cushings syndrome

Hyperaldosteronism

Excessive bicarbonate intake from:

Antacids

Parenteral NaHCO3

MANIFESTATIONSDecreased RR and depth

Dizziness

Numbness and tingling of theextremities

Hypertonic muscles, tetany


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Metabolic Alkalosis

Excess base or loss of

acid

serum pH

Hypoventilation Renal buffering

PaCO2

Serum pH

Hydrogen (H+)

retention

Bicarbonate

excretion

Co

mpensation

When base is accumulated or acid is lost, the serum pH elevates. If this state persists, metabolic alkalosis results. Compensatory mechanisms

will usually be initiated to attempt to return pH toward normal.

Serum pH


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Arterial Blood Gases

performed to evaluatethe clients acid-base

balance and oxygenation

arterial bloodprovides a truer reflection of

gas exchange in the pulmonary system


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Normal Values of ABGs

pH

PaO2

PaCO2

HCO3-

Base excess

O2saturation

7.357.45

80100 mmHg

3545 mmHg

2226 mEq/L

-2 to +2 mEq/L

9598%


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Interpreting ABGs1. Look at the pH:

a.if pH less than 7.35 = acidosis

b.if pH greater than 7.45 = alkalosis

2. Look at the PaCO2:

a.if PaCO2less than 35 = more CO2exhaled

b.if PaCO2greater than 45 = less CO2exhaled


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3. Assess the pH and PaCO2relationship for apossible respiratory problem:

a.if pH less than 7.35 (acidosis) and PaCO2isgreater than 45 mmHg, retained CO2respiratory acidosis

b.if pH greater than 7.45 (alkalosis) and PaCO2is less than 35 mmHg, lack of CO2

respiratory alkalosis


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4. Look at the bicarbonate:

a. if HCO3is less than 22 mEq/L = lowerbicarbonate level

b.if HCO3 is greater than 26 mEq/L =

higher bicarbonate level


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5. Assess pH, HCO3, and base excess (BE) values

for a possible metabolic problem:

a.if pH less than 7.35 (acidosis), HCO3less than22 mEq/L and BE below -2mEq/L = low

bicarbonate levels = metabolic acidosis

b.if pH greater than 7.45 (alkalosis), HCO3

greater than 26 mEq/L and BE above +2mEq/L = high bicarbonate level = metabolicalkalosis


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6. Look for evidence of COMPENSATION:

a.Respiratory acidosis: pH < 7.35

PaCO2> 45 mmHg

If : HCO3is greater than 26 mEq/L= kidneys maintaining

bicarbonate to minimize acidosis = RENAL

COMPENSATION

b.Respiratory alkalosis: pH > 7.45

PaCO2 < 35 mmHgIf : HCO3is less than 22 mEq/L= kidneys excreting

bicarbonate to minimize alkalosis = RENAL

COMPENSATION


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c. Metabolic acidosis: pH < 7.35

HCO3< 22 mEq/L

If : PaCO2 is less than 35 mmHg= CO2being blown off to

minimize acidosis = RESPIRATORY COMPENSATION

d. Metabolic alkalosis: pH > 7.45

HCO3 > 26 mEq/L

If: PaCO2is greater than 45 mmHg = CO2being retained tocompensate for excess base = RESPIRATORY

COMPENSATION


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EXERCISES

1. pH 7.30

pCO2 55 mmHg

HCO3 25 mmHg

2. pH 7.49pCO2 38 mmHg

HCO3 32 mmHg


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3. pH 7.28

pCO2 42 mmHg

HCO3 19 mmHg

4. pH 7.51

pCO2 29 mmHg

HCO3 25 mmHg


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5. pH 7.30

pCO2 38 mmHg

HCO3 19 mmHg


HCO3 19 mmHg

7. pH 7.35

pCO2 29 mmHg

HCO3 19 mmHg


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8. pH 7.28

pCO2 55 mmHg

HCO3 26 mmHg


HCO3 31 mmHg

10.pH 7.35

pCO2 55 mmHg

HCO3 34 mmHg


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Thank you!

acid-base balance report

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