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Acid/Base Balances. By: Diana Blum MSN MCC NURS 2140. Acid /Base Balance. Acid base balance is the regulation of free hydrogen ions in extra-cellular fluid. Acids: dissociate in solution to release H+. Bases: combine with free H+ and remove it from solution. Homeostasis.

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acid base balances


By: Diana Blum MSN


acid base balance
Acid /Base Balance

Acid base balance is the regulation of free hydrogen ions in extra-cellular fluid.

Acids: dissociate in solution to release H+.

Bases: combine with free H+ and remove it from solution.

  • Hydrogen ion: smallest ionic particle and very reactive
      • Small changes can alter protein and enzyme functioning
        • Affects organ function: heart, kidneys, lungs
        • Affects clotting cascade
        • Affects drug metabolism
  • Plasma PH: indicator of hydrogen ion concentration
    • Ex: pH of 7.50 is equivalent to 50 nmol/L of hydrogen ion
    • As Hydrogen ion increases pH decreases and vice versa
  • pH range compatible with life is 6.8-7.8
  • Form hydrogen ions and are proton donors
    • Ex: HCL gives up H+ ion when added to blood
  • Strong acids give up hydrogen easily
    • Lower PH
  • Weak acids keep a grip on their hydrogen ions
    • Higher PH
  • Combine with hydrogen ions
  • Proton acceptors
    • Ex: NaHCO3- (sodium bicarb) removes hydrogen when added to blood
carbon dioxide respiratory acid
Carbon Dioxide/Respiratory Acid
  • Potential acid
    • When dissolved it becomes carbonic acid
  • Body metabolism will constantly produce
    • 288L/day produced and excreted by ventilation
metabolic acid
Metabolic Acid
  • Not many produced on daily basis
  • Main acids are:
    • Lactic
    • Pyruvic
    • Ketoacids
    • Beta hydroxybutyric
  • Eliminated by kidneys or Metabolized by liver
defense mechanisms
Defense Mechanisms
  • First: Buffering
  • 2nd : Changing CO2 level
  • 3rd : changing the level of HCO3 -
buffer systems
Buffer Systems
  • Helps minimize change in pH
  • React quickly to prevent excess changes
  • Primary Buffers: carbonic acid and bicarb
  • Aerobic metabolism:
  • Anaerobic metabolism:
buffer continued
Buffer continued
  • Excess CO2 exhaled
  • Bicarb is retained by glomerular filtration and also excreted by renal tubule
  • So what really happens???
  • Intracellular Buffer is phosphate
  • Protein buffers in blood are plasma protein and hemoglobin
  • Bone is a buffer
r o m e
  • Respiratory Opposite
    • Example: pH low PCO2 high HCO3 ok= respiratory acidosis
  • Metabolic Equal
    • Example: pH is high HCO3 is high it is metabolic
categories of interest
Categories of Interest
  • Respiratory Acidosis:
  • Respiratory Alkalosis:
  • Metabolic Acidosis:
  • Metabolic Alkalosis:
the lungs
The Lungs
  • Regulate plasma pH on minute to minute basis by regulating carbon dioxide.
  • CO2 measured as partial pressure in arterial blood=PaCO2
    • Depth and rate of ventilation will alter
  • Minute Ventilation= how much air moved in 1 minute
    • Increase= blowing off CO2 to compensate
  • Dead Space} wasted ventilation/no part in gas exchange
lungs continued
Lungs continued
  • Respiratory center=
  • Hypercarbic Drive= response to acute respiratory acidosis
    • Determinant of ventilation
  • Hypoxic Drive= Drive to breath…responds to low oxygen levels, high CO2, and acidosis
  • Hyperventilation: low PaCO2/hypocapnia
  • Hypoventilation: high PaCO2/ hypercapnia
  • Kussmals respirations: rapid deep breaths and attempt of lungs to correct pH by decreasing respiratory acid (compensation)
  • Secrete hydrogen ions
  • Reclaim bicarb during the filtering process in the glomerulas.
  • Ammonia
  • pH: 7.35-7.45
  • pCO2: 35-45
  • HCO3: 22-26
  • RR=12-20
  • 1} Assess the pH
  • 2} Is it Respiratory or Metabolic
    • Look at PaCO2
    • Look at Bicarb level
  • 3} Compensation
    • Complete or partial
  • Result from disease, organ dysfunction, pathologic reasons
Referred as primary hypercapnia
  • Excess CO2 decreases pH
    • Regulated by RR
  • Management:
    • Treat underlying cause
    • Sodium Bicarb not always given
    • BiPAP
    • CPAP
    • Vent
Lower than normal PaCO2
  • Elevated pH
    • Excessive /deep ventilation causes CO2 to be blown off thereby increasing pH
      • Alveolar over ventilation
  • Other Causes: hypoxemia, neuro issues, pregnancy
  • Changes serum electrolytes
  • Management: treat underlying cause
    • Breath into a paper bag
    • Reassure
    • Be calm
    • Explain procedures
Increase in total acid level thereby decreasing pH
  • Induced in 2 ways:
    • adding H+ ion or excreting H+ from dietary metabolism
    • Decrease in plasma bicarb to <22
  • Other Causes: ETOH, DM, Aspirin OD, Antifreeze ingestion, GI disturbances
  • Management: assess anion gap, monitor electrolytes and ABGs, treat underlying cause, sodium bicarb admin is controversial
Increase Bicarb and pH
  • Other Causes: depletion in K+, Cl-, volume depletion
  • Hypomagnesaemia may also occur
  • Management: correct volume or electrolyte depletion, may get steroids, dialysis,HCL IV in severe cases
  • Body’s normal way to normalize pH by neutralizing the opposite mechanism
  • Important to know cause and effect

If you only treat compensatory response only pH will become more abnormal

compensated uncompensated
Compensated ? / Uncompensated?

Uncompensated: Ph and one other value abnormal

Partially Compensated: ( All values are abnormal)

Completely Compensated: (pH is the only normal value)

When compensation is present, we will see two imbalances. The question then becomes, which is the primary problem, and which imbalance is due to compensation.
  • The clue is the pH.
    • If the pH is leaning toward acidosis or alkalosis, then the parameter with the matching imbalance is the primary problem, and the other is due to compensation.
  • if the pH is normal in the presence of abnormal pO2/pCO2 – compensated
    • (the body has compensatedfor the abnormality and is able to maintain a normal pH)
  • if the pH is abnormal in the presence of abnormal pO2/pCO2 – uncompensated
    • (the body's defense mechanisms are no longer adequate to compensate, allowing the pH to move to an acidotic or an alkalotic state)

Respiratory acidosis = low ph and high C02 hypoventilation (eg: copd, narcs or sedatives, atelectasis)*Compensated by metabolic alkalosis (increased HC03)examples:ph 7.20 C02 60 HC03 24 (uncompensated respiratory acidosis)ph 7.33 C02 55 HC03 29 (partially compensated respiratory acidosis)ph 7.37 C02 60 HC03 37 (compensated respiratory acidosis)

Respiratory alkalosis = high ph and low C02 hyperventilation (eg: anxiety, PE, pain, sepsis)*Compensated by metabolic acidosis (decreased HC03)examples:ph 7.51 C02 26 HC03 25 (uncompensated respiratory alkalosis)ph 7.47 C02 32 HC03 20 (partially compensated respiratory alkalosis)ph 7.43 C02 30 HC03 19 (compensated respiratory alkalosis)

Metabolic acidosis = low ph and low HC03 ex:diabeticketoacidosis, starvation, severe diarrhea*Compensated by respiratory alkalosis (decreased C02)examples:ph 7.23 C02 36 HC03 14 (uncompensated metabolic acidosis)ph 7.31 C02 30 HC03 17 (partially compensated metabolic acidosis)ph 7.38 C02 26 HC03 20 (compensated metabolic acidosis)

Metabloic alkalosis = high ph and high HC03 ex. severe vomiting, k+ deficit, dieuretics*Compensated by respiratory acidosis (increased C02)example:ph 7.54 C02 44 HC03 29 (uncompensated metabolic alkalosis)ph 7.50 C02 49 HC03 32 (partially compensated metabolic alkalosis)ph 7.44 C02 52 HC02 35 (compensated metabolic alkalosis)

nursing management
Nursing Management
  • Promote healthy behaviors
  • Limit conversations
  • 6 small meals a day
  • Positioning
  • Stress reduction techniques
pH 7.33
  • PCO2 50
  • HCO3 26
  • Respiratory Acidosis
  • pH low PCO2 high bicarb ok
pH 7.52
  • PCO2 40
  • HCO3 30
  • Metabolic alkalosis
  • pH high Bicarb high
acid base problems
Acid base Problems

pH 7.5, PaCO2 = 50 mm Hg, HCO3 =30 mEq/L

Metabolic Alkalosis Partially Compensated.

pH 7.31, Pa CO2 = 50 mm Hg, HCO3 = 22 mEq/L

Respiratory Acidosis Uncompensated.

pH 7.31, PaCO2 = 44 mm Hg , HCO3 = 20 mEq/l

Metabolic Acidosis Uncompensated.

more acid base problems
More, Acid / Base problems.

pH 7.47, PaCO2 = 48 mm Hg , HCO3 = 30 mEq/L

Metabolic Alkalosis Partially Compensated.

pH 7.33, Pa CO2 = 40 mm Hg, HCO3 = 21 mEq/L

Metabolic Acidosis Uncompensated.

pH 7.48, Pa CO2 = 44 mm Hg, HCO3 = 30 mEq/L

Metabolic Alkalosis Uncompensated

even more acid base problems
Even more, Acid /Base Problems

pH 7.33, PaCO2 = 49 mm Hg, HCO3 = 26 mEq/L

Respiratory Acidosis Uncompensated.

pH 7.48, PaCO2 = 33 mm Hg, HCO3 = 24 mEq/L

Respiratory Alkalosis Uncompensated.

pH 7.31, PaCO2 = 33 mm Hg, HCO3 = 20 mEq/L

Metabolic Alkalosis Partially Compensated.

pH 7.45, Pa CO2 = 34 mm Hg, HCO3 = 20 mEq/L

Respiratory Alkalosis Compensated.