1. Chp 24 Acid-base balance

2. Acid-Base Balance Acid-Base balance is:
the regulation of HYDROGEN ions.
The more Hydrogen ions, the more acidic the solution and the LOWER the pH
The lower Hydrogen concentration, the more alkaline the solution and the HIGHER the pH

3. pH The acidity or alkalinity of a solution is measured as pH.
The more acidic a solution, the lower the pH.
The more alkaline a solution , the higher the pH.
Water has a pH of 7 and is neutral.
The pH of arterial blood is normally to 7.45

4. Buffer Systems Regulate pH by binding or releasing Hydrogen
Most important buffer system:
Bicarbonate-Carbonic Acid Buffer System
(Blood Buffer systems act instantaneously and thus constitute the body’s first line of defense against acid-base imbalance)

5. Acid-Base Balance Figure 24.12 pH Normal Alkalosis Acidosis 7.35 7.45
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 24.12 pH
Normal
Alkalosis
Acidosis
7.35
7.45
8.0
6.8
Death
Death
H2CO3
HCO3–

6. Respiratory Regulation
Lungs
help regulated acid-base balance by eliminating or retaining carbon dioxide
pH may be regulated by altering the rate and depth of respirations
changes in pH are rapid,
occurring within minutes
normal CO2 level
35 to 45 mm Hg

7. Renal Regulation Kidneys the long-term regulator of acid-base balance
slower to respond
may take hours or days to correct pH
kidneys maintain balance by excreting or conserving bicarbonate and hydrogen ions
normal bicarbonate level
22 to 26 mEq/L.

8. Factors Affecting Balance
Age
especially infants and the elderly
Gender and Body Size
amount of fat
Environmental Temperature
Lifestyle
stress

9. Chart

10. The Basic Relationship between PCO2 and Plasma pH
Figure 27.6

11. Respiratory Acidosis Mechanism Etiology
Hypoventilation or Excess CO2 Production
Etiology
COPD
Neuromuscular Disease
Respiratory Center Depression
Late ARDS
Inadequate mechanical ventilation
Sepsis or Burns
Excess carbohydrate intake

12. Respiratory Acidosis (cont)
Symptoms
Dyspnea, Disorientation or coma
Dysrhythmias
pH < 7.35, PaCO2 > 45mm Hg
Hyperkalemia or Hypoxemia
Treatment
Treat underlying cause
Support ventilation
Correct electrolyte imbalance
IV Sodium Bicarb

13. Metabolic Acidosis Risk Factors/Etiology
Conditions that increase acids in the blood
Renal Failure
DKA
Starvation
Lactic acidosis
Prolonged diarrhea
Toxins (antifreeze or aspirin)
Carbonic anhydrase inhibitors - Diamox

14. Metabolic Acidosis (cont)
Symptoms
Kussmaul’s respiration
Lethargy, confusion, headache, weakness
Nausea and Vomiting
Lab:
pH below 7.35
Bicarb less than 22
Treatment
treat underlying cause
monitor ABG, I&O, VS, LOC Sodium Bicarb?

15. Respiratory Alkalosis
Risk Factors and etiology
Hyperventilation due to
extreme anxiety, stress, or pain
elevated body temperature
overventilation with ventilator
hypoxia
salicylate overdose
hypoxemia (emphysema or pneumonia)
CNS trauma or tumor

16. Respiratory Alkalosis (cont)
Symptoms
Tachypnea or Hyperpnea
Complaints of SOB, chest pain
Light-headedness, syncope, coma, seizures
Numbness and tingling of extremities
Difficult concentrating, tremors, blurred vision
Weakness, paresthesias, tetany
Lab findings
pH above 7.45
CO2 less than 35

17. Respiratory Alkalosis (cont)
Treatment
Monitor VS and ABGs
Treat underlying disease
Assist client to breathe more slowly
Help client breathe in a paper bag
or apply rebreather mask
Sedation

18. Metabolic Alkalosis Risk Factors/Etiology Acid loss due to
vomiting
gastric suction
Loss of potassium due to
steroids
diuresis
Antacids (overuse of)

19. Metabolic Alkalosis (cont)
Symptoms
Hypoventilation (compensatory)
Dysrhythmias, dizziness
Paresthesia, numbness, tingling of extremities
Hypertonic muscles, tetany
Lab: pH above 7.45, Bicarb above 26
CO2 normal or increased w/comp
Hypokalmia, Hypocalcemia
Treatment
I&O, VS, LOC
give potassium
treat underlying cause

20. Mechanisms of pH control
Buffer system consists of a weak acid and its anion
Three major buffering systems:
Protein buffer system
Amino acid
H+ are buffered by hemoglobin buffer system
Carbonic acid-bicarbonate
Buffer changes caused by organic and fixed acids
Phosphate
Buffer pH in the ICF

21. The Carbonic Acid-Bicarbonate Buffer System
Figure 27.9a, b

22. Maintenance of acid-base balance
Lungs help regulate pH through carbonic acid - bicarbonate buffer system
Changing respiratory rates changes PCO2
Respiratory compensation
Kidneys help regulate pH through renal compensation

23. Kidney tubules and pH Regulation
Figure 27.10c

24. Disturbances of Acid-base Balance
Buffer systems
Respiration
Renal function
Maintain tight control within range 7.35 – 7.45

25. The Central Role of the Carbonic Acid-Bicarbonate Buffer System in the Regulation of Plasma pH
Figure 27.11a

26. The Central Role of the Carbonic Acid-Bicarbonate Buffer System in the Regulation of Plasma pH
Figure 27.11b

27. Acid-Base Disorders Respiratory acid-base disorders
Result when abnormal respiratory function causes rise or fall in CO2 in ECF
Metabolic acid-base disorders
Generation of organic or fixed acids
Anything affecting concentration of bicarbonate ions in ECF

28. Respiratory acid-base disorders
Respiratory acidosis
Results from excessive levels of CO2 in body fluids
Respiratory alkalosis
Relatively rare condition
Associated with hyperventilation

29. Respiratory Acid-Base Regulation
Figure 27.12a

30. Respiratory Acid-Base Regulation
Figure 27.12b

31. Metabolic acid-base disorders
Major causes of metabolic acidosis are:
Depletion of bicarbonate reserve
Inability to excrete hydrogen ions at kidneys
Production of large numbers of fixed / organic acids
Bicarbonate loss due to chronic diarrhea
Metabolic alkalosis
Occurs when HCO3- concentrations become elevated
Caused by repeated vomiting

32. The Response to Metabolic Acidosis
Figure 27.13

33. Metabolic Alkalosis
Figure 27.14

34. Detection of acidosis and alkalosis
Diagnostic blood tests
Blood pH
PCO2
Bicarbonate levels
Distinguish between respiratory and metabolic

35. A Diagnostic Chart for Acid-Base Disorders
Figure 27.15

37. Interpreting ABGs 1. Look at the pH
is the primary problem acidosis (low) or alkalosis (high)
2. Check the CO2 (respiratory indicator)
is it less than 35 (alkalosis) or more than 45 (acidosis)
3. Check the HCO3 (metabolic indicator)
is it less than 22 (acidosis) or more than 26 (alkalosis)
4. Which is primary disorder (Resp. or Metabolic)?
If the pH is low (acidosis), then look to see if CO2 or HCO3 is acidosis (which ever is acidosis will be primary).
If the pH is high (alkalosis), then look to see if CO2 or HCO3 is alkalosis (which ever is alkalosis is the primary).
The one that matches the pH (acidosis or alkalosis), is the primary disorder.

38. Compensation
The Respiratory system and Renal systems compensate for each other
attempt to return the pH to normal
ABG’s show that compensation is present when
the pH returns to normal or near normal
If the nonprimary system is in the normal range (CO2 35 to 45) (HCO ), then that system is not compensating for the primary.
For example:
In respiratory acidosis (pH<7.35, CO2>45), if the HCO3 is >26, then the kidneys are compensating by retaining bicarbonate.
If HCO3 is normal, then not compensating.

39. Normal range in plasma pH HCO3 PCO2 7.35-7.45 22-26 mEq/L 35-45mm Hg
Respiratory acidosis down up if compensating up
Respiratory alkalosis up down if compensating down
Metabolic acidosis down down down if compensating
Metabolic alkalosis up up up if compensating
Remember: ROME Respiratory opposite Metabolic Equal
if both HCO3 and pH are up = metabolic alkalosis
if both HCO3 and pH are down = metabolic acidosis
CO2 up and pH down = respiratory acidosis
CO2 down and pH up = respiratory alkalosis
Look at the CO2 and HCO3 norms which ever one is closer to normal is the compensating factor

40. Acid-base disturbances, causes, and compensatory mechanisms
Common cause
Mode of compensation
Respiratory acidosis
Respiratory depression (drugs, central nervous system trauma)
Kidneys will retain increased amounts of HCO3– to increase pH
Pulmonary disease (pneumonia, chronic obstructive pulmonary disease, respiratory hypoventilation)
Respiratory alkalosis
Hyperventilation (emotions, pain, respirator overventilation)
Kidneys will excrete increased amounts of HCO3– to lower pH
Metabolic acidosis
Diabetes, shock, renal failure, intestinal fistula,
Lungs "blow off" CO2 to raise pH
Metabolic alkalosis
Sodium bicarbonate overdose, prolonged vomiting, nasogastric drainage
Lungs retain CO2 to lower pH

41. Normal Levels of Substances in the Arterial Blood:pH
pCO2 (partial pressure of carbon dioxide)      
40 mm Hg
pO2 (partial pressure of oxygen)
mm Hg
Hemoglobin - O2 saturation %
[HCO3-]
24 meq / liter

42. of green sputum over the last week.
#1:A 14-year-old girl with cystic fibrosis has complained of an increased cough productive
of green sputum over the last week.
She also complained of being increasingly short of breath, and she is noticeably
wheezing on physical examination.
Arterial blood was drawn and sampled, revealing the following values: pH
7.30
pCO2
50 mm Hg
pO2
55 mm Hg
Hemoglobin - O2 saturation
45 %
[HCO3-]
24 meq / liter

43. 2. An elderly gentleman is in a coma after suffering a severe troke
2. An elderly gentleman is in a coma after suffering a severe troke. He is in the intensive care unit and has been placed on a ventilator. Arterial blood gas measurements from the patient reveal the following: pH
7.50
pCO2
30 mm Hg
pO2
100 mm Hg
Hemoglobin - O2 saturation      
98%
[HCO3-]
24 meq / liter

44. 3. A 28-year-old woman has been sick with the flu for the past week, vomiting several times every day. She is having a difficult time keeping solids and liquids down, and has become severely dehydrated. After fainting at work, she was taken to a walk-in clinic, where an IV was placed to help rehydrate her. Arterial blood was drawn first, revealing the following: pH
7.50
pCO2
40 mm Hg
pO2
95 mm Hg
Hemoglobin - O2 saturation      
97%
[HCO3-]
32 meq / liter :

45. What caused this woman’s problems
4. A young woman cramming for her A&P final exam, suddenly feels dizzy and loses consciousness briefly. Her friends notice that she had been breathing faster than normal prior to her passing out. Her friends took her to the emergency ward and on the way she had an episode of dizziness again. At the hospital, these were the results of her blood tests:
pH 7.5
CO2 was 30mmHg
HCO3 was 20meq / liter
What is your diagnosis
What caused this woman’s problems
A young woman cramming for her A&P final exam, suddenly feels dizzy and loses consciousness briefly. Her friends notice that she had been breathing faster than normal prior to her passing out. Her friends took her to the emergency ward and on the way she had an episode of dizziness again. At the hospital, these were the results of her blood tests: pH 7.5, CO2 was 30mmHg