1. By: Diana Blum MSN MCC NURS 2140
Acid/Base Balances
By: Diana Blum MSN
MCC NURS 2140

2. 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.
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4. Homeostasis 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

6. Life
pH range compatible with life is

7. Acids 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

8. Bases Combine with hydrogen ions Proton acceptors
Ex: NaHCO3- (sodium bicarb) removes hydrogen when added to blood

9. Carbon Dioxide/Respiratory Acid
Potential acid
When dissolved it becomes carbonic acid
Body metabolism will constantly produce
288L/day produced and excreted by ventilation

10. Metabolic Acid Not many produced on daily basis Main acids are:
Lactic
Pyruvic
Ketoacids
Beta hydroxybutyric
Eliminated by kidneys or Metabolized by liver

11. Defense Mechanisms First: Buffering 2nd : Changing CO2 level
3rd : changing the level of HCO3 -

12. Buffers

13. Buffer Systems Helps minimize change in pH
React quickly to prevent excess changes
Primary Buffers: carbonic acid and bicarb
Aerobic metabolism:
Anaerobic metabolism:

14. 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

15. Balance in the body is maintained by three buffer mechanisms
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16. R.O.M.E. Respiratory Opposite Metabolic Equal
Example: pH low PCO2 high HCO3 ok= respiratory acidosis
Metabolic Equal
Example: pH is high HCO3 is high it is metabolic

18. Categories of Interest
Respiratory Acidosis:
Respiratory Alkalosis:
Metabolic Acidosis:
Metabolic Alkalosis:

20. Lungs

21. 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

22. 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)

24. Kidneys Secrete hydrogen ions
Reclaim bicarb during the filtering process in the glomerulas.
Ammonia

25. Norms pH: 7.35-7.45 pCO2: 35-45 HCO3: 22-26 RR=12-20
Carbon dioxide is an end product of metabolism, and when dissolved in blood becomes carbonic acid. Carbonic acid is termed a volatile acid because it dissociates into water and a gas, CO2 which is exhaled by the lungs. The pCO2 or PaCO2 represents the partial pressure of carbon dioxide dissolved in arterial blood, and provides an important measure of the adequacy of a patient’s ventilation. The lungs normally maintain an acceptable balance of CO2 (which is acidotic) in the bloodstream. The normal range for this respiratory component of ABG’s, the pCO2, is 35 – 45 mmHg, and is maintained by ventilation.
When the patient is moving a normal volume of air in and out of the lungs, the pCO2 will stay within the normal range. Hypoventilation will prevent sufficient removal of CO2 from the bloodstream, causing a respiratory acidosis. Some causes of respiratory acidosis include obstructive lung disease, restrictive lung disease and hypoventilation as a result of oversedation, anesthesia or improper ventilator settings (e.g., tidal volume too low.) Respiratory acidosis could also result from a drug overdose and neuromuscular diseases such as Guillain-Barre syndrome or myasthenia gravis.
Hyperventilation, on the other hand, causes CO2 to be “blown off” or removed, causing a respiratory alkalosis. The pCO2 falls below 35, and the acid-load decreases, causing an alkalosis. Some possible causes of respiratory alkalosis include pain, panic attacks, anxiety, pulmonary embolism, pregnancy, and a tidal volume that is too high for a ventilator patient.
The second step in ABG interpretation, is to evaluate the pCO2, to determine if it falls within the acceptable range, falls below the lower limit (respiratory alkalosis) or is above the upper limit (respiratory acidosis.)
Notice that a high value in pCO2 actually represents an acidosis (retention of CO2), whereas a high value in pH represents an alkalosis. Do not try to memorize, but rather to understand the concept of what the components represent. A high level of pCO2 simply means there is retention of CO2 or hypoventilation. CO2 is acidotic in the blood, and too much causes respiratory acidosis.
HCO3 represents the metabolic component of ABG interpretation, with a normal range of mEq/L. Bicarbonate (HCO3) is a weak base that is regulated by the kidneys.
When there is a loss of acid in the body, or an excess of base, the HCO3 will be greater than 26, resulting in metabolic alkalosis. Some causes of metabolic alkalosis include loss of stomach acid and potassium from vomiting or gastric suction, and ingestion of large amounts of bicarbonate. Prolonged therapy with potassium-wasting diuretics, steroid therapy, Cushing's disease, and aldosteronism can also deplete potassium, chloride, and hydrogen levels, resulting in metabolic alkalosis.
When there is an excess of metabolic acid, or not enough base, the HCO3 will be less than 22, causing metabolic acidosis. Conditions that increase acid-load include diabetic ketoacidosis or prolonged fasting, lactic acidosis, and renal failure. Actual loss of bicarbonate ions through severe diarrhea leads to metabolic acidosis. During cardiac arrest, or when low cardiac output states (as in external cardiac compression) are present, anaerobic metabolism occurs and there is an increase in the [production of lactic acid. Metabolism of lactic acid is normally effected through the Krebs cycle, and oxygen is the essential element for this metabolic process. In the absence of adequate tissue oxygenation, lactic acid cannot be metabolized; its quantity increases and the result is metabolic acidosis.
The third step in ABG interpretation is to determine the direction of the metabolic component HCO3, whether it is within normal limits, is high (metabolic alkalosis), or low (metabolic acidosis.) Simply think of HCO3 as a base, and too much causes metabolic alkalosis, whereas too little causes metabolic acidosis.

26. Interpretation 1} Assess the pH 2} Is it Respiratory or Metabolic
Look at PaCO2
Look at Bicarb level
3} Compensation
Complete or partial

27. 1}

28. 2}

29. 2}

31. Imbalances
Result from disease, organ dysfunction, pathologic reasons

32. Respiratory Acidosis

33. Referred as primary hypercapnia Excess CO2 decreases pH Management:
Regulated by RR
Management:
Treat underlying cause
Sodium Bicarb not always given
BiPAP
CPAP
Vent

34. Respiratory Alkalosis

35. Other Causes: hypoxemia, neuro issues, pregnancy
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

36. Metabolic Acidosis

37. 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

38. Metabolic Alkalosis

39. 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

40. Compensation
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

41. Compensated ? / Uncompensated?
Uncompensated: Ph and one other value abnormal
Partially Compensated: ( All values are abnormal)
Completely Compensated: (pH is the only normal value)
Maintenance of acid-base balance is normally accomplished by buffer systems which react to changes in the hydrogen ion concentration of body fluids. The primary buffer system is the bicarbonate (kidneys) - carbonic acid (lungs) buffer system. When there is an imbalance in one parameter, the other tries to compensate for it by causing the opposite imbalance. The goal of this compensation process is to restore the 20:1 ratio, and return the pH back to the acceptable range of 7.35 – 7.45.
The regulation of respiration is achieved mainly by chemoreceptors in the medulla, that are stimulated or inhibited by an increase or decrease in the carbonic acid and hydrogen ion levels. Normally an increase in carbonic acid or hydrogen ion concentration in the blood stimulates an increase in the rate and depth of ventilations, cause more carbon dioxide to be removed. A decrease in concentration of carbonic acid results in a decrease in rate and depth of breathing, thus retaining more carbon dioxide. The lungs can begin to compensate for metabolic imbalances immediately, but can only partially correct pH deviations (can return pH to normal range, but never to perfectly normal 7.4).
The kidneys, on the other hand, take much longer to compensate, sometimes as long as 3-5 days to fully compensate. An increase in hydrogen ion concentration is corrected by increasing the amount of bicarbonate that is returned to the blood, and increasing the amount of acid that is excreted. A decrease in hydrogen ion concentration is corrected by increasing the amount of acid that is retuned to the blood, and increasing the amount of bases, particularly, bicarbonate, that are excreted. The kidneys may be slower to compensate, but they are much more powerful, and can return the pH to perfectly normal 7.4.
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42. When compensation is present, we will see two imbalances
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.

43. EXAMPLE
if the pH is normal in the presence of abnormal pO2/pCO2 – compensated
(the body has compensated for 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)
A diabetic patient goes into ketoacidosis and develops Kussmaul breathing, causing him to blow off CO2, creating a respiratory alkalosis to help balance his pH.

44. *Remember that compensation corrects the ph.

45. Examples
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)
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)

46. Metabolic acidosis = low ph and low HC03 ex:diabetic ketoacidosis, 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)

47. Nursing Management Promote healthy behaviors Limit conversations
6 small meals a day
Positioning
Stress reduction techniques

49. Practice

50. pH 7.33
PCO2 50
HCO3 26

51. Answer
Respiratory Acidosis
pH low PCO2 high bicarb ok

52. pH
PCO
HCO

53. Answer
Metabolic alkalosis
pH high Bicarb high

54. 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.
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55. 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
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56. 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.
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