Ch 52 Acids & Bases

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cswett
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112776
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Ch 52 Acids & Bases
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2011-11-12 22:59:49
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52 Acids Bases
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Ch 52 Acids & Bases
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  1. Acids & Bases
    Acidity or alkalinity (base) of a solution is determined by its concentration of hydrogen ions (H+)

    Acids- substances with a high concentration of hydrogen (H+) & can release H+ in a solution

    Bases (alkalis)-substances with a low H+ concentration & can accept H+ in a solution

    • pH- is how acidity & alkalinity are measured
    • Water: pH-7, neutral
    • pH < 7 are acidic (more H+)
    • pH > 7 are alkaline (less H+)
  2. Acid- Base Balance
    Blood pH is slightly alkaline 7.35-7.45

    Acid-Base balance is important for homeostasis. It is the mechanisms by which the acidity & alkalinity of body fluids are kept in a state of equilibrium so that arterial blood is maintained at approximately pH 7.35 to 7.45.
  3. Buffer Regulation of A-B
    • Buffers- prevent excessive changes in pH by removing or releasing H+ as needed
    • Work immediately, action limited

    • Major buffers are:
    • Bicarbonate (HCO3)
    • Carbonic Acid (H2CO3)
  4. Respiratory Regulation of A-B
    • Lungs- regulate carbonic acid by exhaling carbon dioxide (CO2)
    • Works in minutes
    • Carbon dioxide is measured in arterial blood as PaCO2
    • P= partial pressure of a gas
    • a= arterial
  5. Renal Regulation of A-B
    • Kidneys- maintain pH by selectively excreting or conserving bicarbonate (base) & H+ (acid)
    • Slower to respond to changes in pH, takes hours to days
  6. Evaluating Acid-Base Balance
    • Arterial Blood Gases (ABGs) are used to evaluate A-B balance
    • The main ones:
    • pH
    • PaCO2
    • HCO3
  7. pH (7.35 – 7.45)
    Measures H+ concentration in body fluids

    • pH of Less than 7.35 is Acidic
    • pH of More than 7.45 is Alkalotic
  8. PaCO2 (35-45 mm Hg)
    • Is a reflection of depth of pulmonary ventilation
    • < 35 indicates hyperventilation and more CO2 is exhaled & concentration is decreased

    >45 indicates hypoventilation and more CO2 is retained increasing the concentration of CO2
  9. HCO3- (22-26 mEq/L)
    • HCO3 is the major renal component of Acid- Base balance.
    • It is excreted & reproduced by the kidneys
    • <22- HCO3 levels are lower than normal
    • >26- HCO3 levels are higher than normal
  10. Other ABG Results
    • ABGs also give 3 other important results:
    • PaO2
    • O2 Saturation (SaO2)
    • Base excess (BE)- calculated figure that provides indication of amount of bicarb
  11. PaO2 (80-100)
    • Measures partial pressure of Oxygen in arterial blood
    • If PaO2 is normal it plays NO role in Acid Base balance
    • If PaO2 is less than 60 it causes lactic acid
    • production resulting in metabolic Acidosis
    • Hypoxemia may also cause hyperventilation =respiratory Alkalosis
  12. O2 Saturation (98-98%)
    • SaO2-the percentage of Hgb saturated with O2
    • PaO2 & SaO2 are important in assessing respiratory status but do not provide useful info for acid base imbalance
  13. Acid-Base Imbalances
    • Acidosis- pH drops
    • Respiratory
    • Metabolic

    • Alkalosis- pH rises
    • Respiratory
    • Metabolic
  14. Respiratory Acidosis
    pH< 7.35, PaCO2> 45
    • Cause: HYPOVENTILATION (CO2 retention)
    • Diseases of lungs- acute or chronic
    • Airway obstruction
    • Drugs (narcotics) & anesthesia
    • Kidneys will compensate by retaining bicarbonate, takes several days
  15. Assessment of Respiratory Acidosis
    • Increased P & RR- compensation for CO2
    • CO2 causes vasodilatation
    • Headache
    • Confusion & decreased LOC
    • Convulsions
    • Dizziness
    • Warm flushed skin
  16. Nursing Dx
    Respiratory Acidosis
    • Main:
    • Ineffective breathing patterns
    • Impaired gas exchange
    • Risk for Injury
    • Pain (headache)
    • Alterations in Thought Processes
  17. Nursing Interventions: Respiratory Acidosis
    • Frequent lung & mental assessments
    • Encourage deep breathing, coughing, and changes in position at least every 2 hours.
    • Institute Chest Physiotherapy
    • Encourage Fluids 2L per day.
    • Administer low flow O2 as ordered
    • Monitor ABG’s
    • Position in semi-Fowlers position
  18. Metabolic Acidosis
    pH< 7.35, HCO3< 22
    • Cause: an increased accumulation of metabolic acids in proportion to bicarbonate
    • Increased acids
    • Renal failure, diabetes, starvation, cardiac arrest
    • Ingestion of salicylates (aspirin- acidic)
    • Decreased HCO3
    • Prolonged diarrhea
    • Excessive IV NaCl- Na binds with HCO3
  19. Assessment of Metabolic Acidosis
    • Kussmaul’s respirations (deep,rapid)- attempt to blow off CO2
    • Fruity Breath (ketoacidosis is the cause) Diabetic ketoacidosis - breaking down ketones
    • Lethargy & confusion
    • Headache
    • Weakness
    • N & V (Nausea & Vomiting)
  20. Nursing Dx
    Metabolic Acidosis
    • Main:
    • Altered Tissue Perfusion (cardiac arrest with build up of lactic acid)
    • Risk for injury
    • Pain
    • Activity intolerance
  21. Nursing Interventions
    Metabolic Acidosis
    • Monitor VS, ABGs, I & O, LOC, glucose
    • Assess peripheral vascular status (cap. refill, temperature , color)
    • Monitor cardiac status
  22. Metabolic Alkalosis
    PH> 7.45, HCO3> 26
    • Cause: HCO3 exceeds carbonic acid
    • Acid loss
    • Vomiting or gastric suction
    • High HCO3 intake
    • Antacids
    • IV NaHCO3
    • Diseases causing Na retention
    • Meds causing K lose
  23. Assessment of Metabolic Alkalosis
    • Decreased RR & depth (lungs will compensate by conserving CO2)
    • Dizziness
    • Altered Ca+
    • Paresthesia, numbness & tingling, tetany
  24. Step 1
    • Look at each number seperately and label them
    • pH
    • <7.35 = acidosis
    • > 7.45 = alkalotic

    • PaCO2
    • <35 = alkalosis
    • >45 = acidosis

    • HCO3
    • <22 = acidosis
    • >26 = alkalosis
  25. Step 2 & 3
    • Step 2:
    • Look at pH- is it acidotic or alkalotic?

    • Step 3:
    • Check PaCO2 & HCO3
    • Which one matches the pH?
    • The one that matched the pH (acidosis or alkalosis) tell what system
    • PaCO2 = acidosis
    • HCO3- = alkalosis
  26. Example: PaCO2 matching pH
    • pH is < 7.35 (acidosis)
    • PaCO2 > 45 (acidosis)
    • RESPIRATORY ACIDOSIS

    • pH > 7.45 (alkalosis)
    • PaCO2 < 35 (alkalosis)
    • RESPIRATORY ALKALOSIS
  27. Example: HCO3 matching pH
    • pH <7.35 (acidosis)
    • HCO3 <22 (acidosis)
    • METABOLIC ACIDOSIS

    • pH is > 7.45 (alkalosis)
    • HCO3 > 26 (alkalosis)
    • METABOLIC ALKALOSIS
  28. Step 4
    • Look for compensation
    • Look at the value that does not match-
    • If it is normal- no compensation
    • If it is above or below normal = compensation
  29. Nursing Dx : Metabolic Alkalosis
    • Main:
    • Ineffective breathing patterns
    • High Risk for Injury
    • Altered Thought Processes
  30. Nursing Interventions: Metabolic Alkalosis
    • Monitor VS, ABGs, electrolytes
    • Provide emotional support & reassurance to reduce anxiety.
    • Encourage slow, deep breathing (paper bag)
    • Rebreather mask (to inhale CO2)
    • If sedation is used to slow respiratory rate, assess for resp. depression.
  31. Respiratory Alkalosis
    pH> 7.45, PaCO2 <35
    • Cause: HYPERVENTILATION (CO2 exhaled)
    • Anxiety
    • Increased metabolic rate & fever
    • Hypoxia
    • Aspirin overdose
    • Brain stem injury

    Kidneys will compensate by excreting HCO3
  32. Assessment of Respiratory Alkalosis
    • Shortness of breath
    • Decrease blood flow to brain
    • Light-headedness
    • Difficulty concentrating
    • Blurred vision

    • Altered Ca+
    • Paresthesia, numbness & tingling, tremors
  33. Nursing Dx: Respiratory Alkalosis
    • Main:
    • Ineffective breathing patterns
    • High Risk for Injury
    • Altered Thought Processes
  34. Nursing Interventions: Respiratory Alkalosis
    • Monitor VS, ABGs, electrolytes
    • Provide emotional support & reassurance to reduce anxiety.
    • Encourage slow, deep breathing (paper bag)
    • Rebreather mask (to inhale CO2)
    • If sedation is used to slow respiratory rate, assess for resp. depression.
  35. Facilitating Fluid Intake
    • Explain the reason for the required intake
    • Establish a 24 hr ingestion plan
    • Set-short term outcomes for client to meet
    • Identify fluids cilient likes & make available
    • Help client select food that are liquid at room temp
    • Supply cups straws & put within reach
    • Serve fluids at appropriate temp
    • Encourage client to record I & O
    • consider cultural implications of food and fluid
  36. Helping clients restrict fluid intake
    • Expain reason for restriction
    • Help client schedule allowed fluids
    • Make available fluids client likes (unless contraindicated)
    • Set short term goals
    • Place in small containers so they look full
    • Offer ice chips insead of water - 1/2 volume
    • mouth care
    • client should avaid salty or sweet foods
    • Encourage client to record I & O
  37. Tonicity of IV solutions
    • Isotonic Solutions - same concentration of solutes as plasma
    • NS - 0.9% NaCl
    • Lactated Ringers - Na, Cl, K, Ca, Lactate (which metabolizes in the liver to form HCO3-
    • D5W - 5% dextrose in water

    • Hypotonic Solutions - less solute than plasma
    • 1/2 NS - 0.45% NaCl
    • 1/3 NS - 0.33% NaCl

    • Hypertonic Solutions - more solute than plasma
    • D5NS - 5% dextrose in NS
    • D5 1/2 NS - 5% dextrose in 0.45% NaCl
    • D5LR - 5% dextrose in lactated ringers

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