Nursing 280: Pathophysiology Examination

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Nursing 280 PathophysiologyExamination
3Module II Section BAcid/Base Balance

• Presented by
• Ronda M. Overdiek M.S.N., R.N.

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Acid/Base Balance

• Chapter 4

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Objective 1Describe the normal regulations of
acid/base

• pH
• Hydrogen ion concentration in body fluids
• 10-7 or 0.0000001 mg/L
• Expressed as pH of 7.0
• As pH changes one unit, H changes 10X
• H acid
• SO as H INCREASES, pH DECREASES
• The greater the H , more acid LOWER the pH
• The lower the H , less acid HIGHER the pH
• BIOLOGIC FLUIDS (According to Book)
• pH lt 7.4 acidic pH gt 7.4 basic

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Objective 1Describe the normal regulations of
acid/base

• Acids are formed as by-products of cellular
  metabolism
• Two forms of body acids
• Volatile Can be eliminated as CO2 (respiratory)
• Carbonic Acid H2CO3 (weak acid)
• Nonvolatile Can be eliminated by kidney
• Sulfuric, phosphoric, other organic acids
• CO2 H2O H2CO2
  HCO3- H
• (Regulated by lung) (Regulated by
  kidney)

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Objective 1Describe the normal regulations of
acid/base

• Buffers
• Absorb excessive H (acid) or OH- (base) without
  a significant change in pH.
• Buffering occurs in response to acid/base status
• Systems located in both ICF/ECF
• ICF phosphate/protein
• ECF (plasma) carbonic acid-bicarbonate/ Hgb

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Objective 1Describe the normal regulations of
acid/base

• Buffering occurs at different rates
• Cellular (Hb/HHb) Immediate
• Respiratory (Lungs) Minutes/Hours
• Metabolic (Kidneys) Hours/Days

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Objective 1Describe the normal regulations of
acid/base

• Protein Buffering
• Intracellular Buffer
• Hemoglobin (Hb) binds with H to form HHb
• Hb binds w/carbon dioxide to form HHbCO2
• Renal Buffering
• Distal tubule secretes H in the urine and
  reabsorbing HCO3-

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Objective 1Describe the normal regulations of
acid/base

• Carbonic Acid-Bicarbonate Buffering
• Operates in the lung and the kidney
• Major Extracellular Buffer
• Lungs
• Decreases the amount of carbonic acid by blowing
  off carbon dioxide and leaving water
• Kidneys
• Reabsorb bicarbonate or regenerate new
  bicarbonate from carbon dioxide and water

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Objective 1Describe the normal regulations of
acid/base

• Bicarbonate Base HCO3- 24 mEq/L
• Carbonic Acid Acid H2CO3 1.2 mEq/L
• PRODUCES
• 201 Ratio
• Normal pH 7.4
• Acid Adjusted rapidly by lungs
• Bicarbonate Reabsorbed/regenerated by kidneys

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Why Care?From Wise, 1992.
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Laboratory Measurements

• Maintain Homeostasis
• Blood Gas (Arterial, Venous, Capillary)
• Components
• pH
• PaO2
• PaCO2
• HCO3- (Base Excess)
• SaO2

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Laboratory MeasurementsBlood Gas

• Components tell us
• Respiratory (Lungs)
• Oxygenation Ventilation
• PaO2 PaCO2
• SaO2
• Metabolic (Kidneys)
• HCO3-
• BE

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Components of Oxygenation

• Oxygenation
• PaO2
• SaO2

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Blood Gas Components

• PaO2
• Partial pressure of oxygen (O2) dissolved in
  plasma
• 3-5 of total O2 content of arterial blood
• Reflect diffusion of O2 from alveoli into blood
• Normal 90-100 mmHg
• Abnormal lt60 mmHg Hypoxemia

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Blood Gas ComponentsPractice PaO2

• 68
• 58
• 42
• 100
• 70

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Blood Gas ComponentSaO2

• SaO2
• Degree to which hemoglobin molecules are
  saturated with O2
• Normal Greater than or equal to 95
• Abnormal Less than 90 Hypoxemia

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Blood Gas ComponentsPractice SaO2

• 68
  60
• 58
  38
• 42
  50
• 100
  99
• 70
  75

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Blood Gas ComponentsAcid/Base Imbalances

• pH
• Measure of H
• Normal 7.35-7.45
• Abnormal
• Less than 7.35 Acidemia/Acidosis
• Greater than 7.45 Alkalemia/Alkalosis
• DOES NOT TELL THE ORIGIN OF THE IMBALANCE

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Objective 2Identify alterations in acid-base
balance

• Acidosis
• Systemic increase in H
• Alkalosis
• Systemic decrease in H
• Respiratory/Metabolic
• CO2 H2O H2CO2
  HCO3- H
• (Regulated by lung) (Regulated by
  kidney)

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Blood Gas ComponentsPractice pH

• 7.38 68
  60
• 7.50 58
  38
• 7.20 42
  50
• 7.34 100
  99
• 7.60 70
  75

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To Keep pH in Balance

• Homeostasis relies on
• Respiratory Mechanism (Lungs)
• Metabolic Mechanism (Kidneys)
• CO2 H2O H2CO2
  HCO3- H
• (Regulated by lung) (Regulated by
  kidney)

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Respiratory ComponentPaCO2 (Ventilation)

• PaCO2
• Partial pressure of carbon dioxide (CO2)
  dissolved in plasma
• 5 percent of total CO2 content of arterial blood
• Measure of carbonic acid
• Direct reflection of alveolar ventilation
• Normal 35-45 mmHg
• Abnormal
• lt 35 mmHg Hyperventilation (Alkalosis)
• gt 45 mmHg Hypoventilation (Acidosis)

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Objective 3Describe major categories of
acid/base imbalance and their clinical
manifestations

• Respiratory Acidosis
• Decrease in alveolar ventilation
  (hypoventilation) in relation to the metabolic
  production of carbon dioxide and an increase in
  carbonic acid.
• PaCO2 level gt 45 mm Hg
• Causes respiratory depression/muscle paralysis,
  pulmonary edema, pneumonia, asthma, anything
  causing decrease in ability to ventilate.
• Signs/Symptoms
• Breathlessness, restlessness, apprehension
  followed by lethargy disorientation, muscle
  twitching, tremors, convulsions,and coma.
• Treatment Increase alveolar ventilation/correct
  cause

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Objective 3Describe major categories of
acid/base imbalance and their clinical
manifestations

• Respiratory Alkalosis
• Alveolar hyperventilation and excessive reduction
  in plasma carbon dioxide levels.
• PaCO2 levels lt35 mm Hg
• Signs/Symptoms
• Dizziness, confusion, tingling of extremities,
  convulsions, coma, cerebral vasoconstriction.
• Causes
• Hypoxemia, CHF, overdose, hysteria, cirrhosis,
  improper use of mechanical ventilation.
• Treatment Decrease alveolar ventilation/correct
  cause

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Blood Gas ComponentsPractice PaCO2

• 7.38 68 40
  60
• 7.50 58 28
  38
• 7.20 42 80
  50
• 7.34 100 48
  99
• 7.60 70 22
  75

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Metabolic ComponentHCO3-

• Bicarbonate (HCO3-)
• Measure of metabolic base
• Regulated by kidneys
• Normal 22-28 mEq/L
• Abnormal
• Less than 22 mEq/L metabolic acidosis
• Greater than 28 mEq/L metabolic alkalosis

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Metabolic ComponentBase Excess

• Base Excess (BE)
• Measure of base
• Another measure of bicarbonate
• Normal -2, -1, 0, 1, 2
• Abnormal
• gt -2 Base deficit
• gt 2 Base excess

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Objective 3Describe major categories of
acid/base imbalance and their clinical
manifestations

• Metabolic Acidosis
• Noncarbonic acids increase or bicarbonate is lost
  from extracellular fluid
• Signs/Symptoms Changes in function of
  neurologic, respiratory, gastrointestinal, and
  cardiovascular systems. Headache, lethargy, coma,
  Kussmaul respirations, anorexia, nausea,
  vomiting, diarrhea, death.
• Treatment Correct cause if necessary administer
  bicarbonate

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Objective 3Describe major categories of
acid/base imbalance and their clinical
manifestations

• Metabolic Alkalosis
• Loss of metabolic acids occurs, bicarbonate
  increases
• Causes loss of chloride (vomiting, GI suction)
  hyperaldosteronism, diuretics
• Signs/Symptoms
• Weakness, muscle cramps, hyperactive reflexes,
  tetany, depressed respirations, confusion,
  convulsions.
• Treatment
• Administer chloride/correct cause

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Blood Gas ComponentsPractice HCO3-

• 7.38 68 24 0
  60
• 7.50 58 35 5
  38
• 7.20 42 18 -4
  50
• 7.34 100 21 -3
  99
• 7.60 70 32 4
  75

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Objective 2Identify alterations in acid-base
balance

• Compensation
• Respiratory System
• Acts in minutes to hours
• Increases or decreases carbon dioxide by changing
  rate/depth of respirations (ventilation)
• Renal System
• Acts in hours to days
• Producing more acidic or more alkaline urine

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Objective 2Identify alterations in acid-base
balance

• Compensation occurs in levels
• Absent or Uncompensated
• Only primary problem exists
• pH abnormal
• Partial Compensation
• Primary and Secondary problem exists
• pH abnormal
• Complete Compensation
• Primary and secondary problems exist
• pH normal
• Correction
• Occurs when primary and secondary problems
  return to normal and pH is normal.

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Complete Compensation

• Two factors
• 1. pH is normal
• 2. Primary and secondary problems exist
• (Metabolic/Respiratory abnormal)
• Compensated Respiratory Acidosis
• Compensated Metabolic Alkalosis
• Normal pH
• pCO2 ( ) Acidotic HCO3- ( ) Alkalotic

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Complete Compensation

• Compensated Metabolic Acidosis
• Compensated Respiratory Alkalosis
• Normal pH
• PaCO2 ( ) Alkalosis
• HCO3- ( ) Acidosis
• Remember To determine which one came first, you
  need to know the patients history.

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Blood Gas ComponentsComplete Compensation
Practice

• 7.40 68 52 30
  60
• 7.45 58 30 19
  38
• 7.37 42 80 34
  50
• 7.43 100 18 12
  99
• 7.35 70 40 24
  75

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Partial CompensationAlkalosis

• Respiratory and Metabolic Alkalosis
• pH Alkalotic (not compensated fully)
• Respiratory
• PaCO2 ( ) Alkalosis
• HCO3- ( ) Acidosis
• Metabolic
• PaCO2 ( ) Acidosis
• HCO3- ( ) Alkalosis

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Partial CompensationAcidosis

• Respiratory and Metabolic Acidosis
• pH is Acidotic (not fully compensated)
• Respiratory
• PaCO2 ( ) Acidosis
• HCO3- ( ) Alkalosis
• Metabolic
• PaCO2 ( ) Alkalosis
• HCO3- ( ) Acidosis

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Blood Gas ComponentsPartial Compensation
Practice

• 7.30 68 30 20
  60
• 7.50 58 28 18
  38
• 7.20 42 80 31
  50
• 6.80 35 108 35
  30
• 7.60 70 70 32
  75

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SummaryBlood Gas Interpretation

• 1. Oxygenation
• Look at PaO2 lt60 mmHg Hypoxemia
• Look at SaO2 lt90 Hypoxemia
• 2. pH (1) normal pt is normal or
• completely compensated (primary
  and secondary problems exist)
• (2) gt7.45 alkalosis
• (3) lt7.35 acidosis

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SummaryBlood Gas Interpretation

• 3. Ventilation (Respiratory Component)
• PaCO2 lt 35 mmHgrespiratory alkalosis
• If pH is alkalotic, respiratory alkalosis is
  primary problem
• PaCO2 gt 45 mmHgrespiratory acidosis
• If pH is acidotic, respiratory acidosis is
  primary problem

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SummaryBlood Gas Interpretation

• 4. Metabolic (kidneys)
• HCO3- lt 22 mEq/L metabolic acidosis
• If pH is acidotic, metabolic acidosis is primary
  problem
• HCO3- gt 28 mEq/L metabolic alkalosis
• If pH is alkalotic, metabolic alkalosis is
  primary problem

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SummaryBlood Gas Interpretation

• 5. Look for compensation
• 1. No compensation pH abnormal, only primary
  problem exists
• 2. Partial compensation pH is abnormal and
  primary and secondary problems exist
• 3. Complete compensation pH is normal and both
  primary and secondary problems exist