Dr. Elias Areen El Azhar university Gaza Palestine lama el banna faculty of dentistry surgery

1. Acid base balance
Elias arteen FRCSI
General and colorectal surgeon
El Quds hospital
E-mail: E_Arteen@hotmail.com

2. Acid base balance
Definition of PH 7.36-7.44
 Acidosis Alkalosis
Buffer systems: Is a weak acid or base and salt of that acid or
base.
H2CO3 HCO3
Main extracellular buffer is bicarbonate 65%.
Main intracellular buffer is proteins 30% bone, and phosphate.

3. Acid base balance
• Acids
Are molecules that have the ability to release H+
ions
Fixed acids Volatile acids
Bases
Are molecules that have the ability to accept or bind
with H+
ions.

6. Continue
CO2 (gas) CO2 (water )+H2O H2CO3
H+
+ HCO3
-
Lung control CO2 level
Kidney control HCO3 level through
Reabsorption of HCO3 proximal renal tubules.
Generation of HCO3 distal renal tubules.

7. How does lung control CO2 level?
Shifting the equation to left.
Medullary ,carotid body chemoreceptors stimulate
respiration.
C02 diffuse 20 times more than 02.

8. Acid base regulation
Maintenance of acceptable range of PH in ECF is
accomplished by three mechanisms.
Chemical buffers
React very rapidly less than one second.
Respiratory regulations
Reacts rapidly seconds to minutes .
Renal regulations
Reacts slowly minutes to hours.

9. 9

10. 10

11. Acidosis/alkalosis
PH changes has dramatic effects on cell
functions
Change in excitability of nerve and muscle cell.
Influence enzyme activity.
Influence K+
levels .

12. 12

13. Henderson-Hasselbach equation
 pH=pK + log BHCO3 24mEq/L 20 7.4
H2CO3 1.2mEq/L 1
 The pH is dictated by Ratio of HCO3 to CO2.
 If ratio is 20:1 PH is 7.4.
 Increase HCO3 increase CO2 to keep ratio constant.

15. Respiratory Control Mechanisms:
Works within minutes to control pH; maximal in 12-24
hours.
Only about 50-75% effective in returning pH to normal.
Excess Co2 & H+
in the blood act directly on respiratory
centers in the brain.
CO2 readily crosses blood-brain barrier reacting w/ H2O to
form H2CO3.
H2CO3 splits into H+
& HCO3
-
& the H+
stimulates an
increase or decrease in respirations.

16. Renal control mechanisms
Don’t work as fast as respiratory mechanisms ,
functions for days to restore PH to normal level .
Regulate PH through exerting acidic or alkaline urine ,
excreting excess H+ ,and regeneration and reabsorption
of HCO3.
Excreting acidic urine decrease acidity of EC fluid,
excreting alkaline urine remove base.

18. 18
ACIDOSIS / ALKALOSIS
Acidosis and Alkalosis are categorized as MetabolicMetabolic or
RespiratoryRespiratory depending on their primary cause.
Metabolic AcidosisMetabolic Acidosis andand Metabolic AlkalosisMetabolic Alkalosis
Caused by an imbalance in the production and excretion of
acids or bases by the Kidneys.
Respiratory Acidosis and Respiratory Alkalosis
Caused primarily by Lung or breathing disorders.

19. Metabolic acidosis
Causes
Increase acid production
 Shock (lactic acid).
 Diabetes (keto acids).
 Renal failure (sulfuric, phosphoric acid).
Increase alkali excretion(GIT-Kidney)
 Diarrhea, small bowel, pancreatic fistula.
 Uretro – sigmoidostomy.
 Renal tubular acidosis.

20. What is the most common cause
M A in surgical patients?
 Shock decrease tissue perfusion
lactic acidosis anaerobic metabolism
wide anion gap
 Severe anemia.
 Severe hypoxaemia.

21. What is anion gap(AG)
Definition
 AG is the difference between
measured cations and measured
anions.
AG=Na-(Cl -
+HCO3) =5-11 mEq/L
 Increase acid production increase AG.
 Increase alkali loss normal AG.
 NB hypoalbuminaemia reduce AG

22. Anion gap metabolic acidosis
 Methanol
 Ureamia
 Diabetic ketoacidosis
 Propylene glycol
 Isoniazid
 Lactic acid
 Ethylene glycol
 Rhabdomyolysis
 Salicylates

23. Non anion gap metabolic acidosis
• Fistula (pancreatic)
• Uretro-enterostomy
• Saline administration
• Endocrine (hyperparathyroidism)
• Diarrhea
• Carbonic anhydrase inhibitors
• Ammonium chloride
• Renal tubular acidosis
• Spironolactone

24. Symptoms
 Lethargy ,headache.
 Deep rapid breathing Kussmaul’s breathing.
 Cardiac arrhythmias, decrease CO.
 Depression of CNS, coma.
Treatment
 Treat the cause .
 In severe cases give NaHCO3.
• PH less than 7.2
• Hco3 less than 12

26. 0.3X wt x base deficit
0.3x70x20 =210mEq/l NaHCO3
Give half over 20 minute, rest over 4 h
8.4% NaHco3 1ml=1mmol
4.2%NaHco3 1ml=1/2 mmol

27. What is compensated MA
• Look for paco2 expected pco2
1.5xHCO3 +8
Yes compensated MA.
No added respiratory acidosis.

28. Metabolic alkalosis
 Loss of acid from GIT, or Kidney
(Vomiting, Overdiuresis , Ascites)
 Diuretic therapy
 Excessive alkali Administration
 Massive blood transfusion
 Severe K depletion
 Mineralocorticoid excess
Chloride
Resistance
Chloride
Sensitive

29. Patient with alkalosis is always K Deficit
K move into cell
K is lost in urine
So always give potassium
Urine should be adequate first.

30. Symptoms
 Increase neuromuscular excitability , parathesia.
 Carpo - pedal spasm.
 Keynes-stokes breathing with period of apnea 5-30 s.
 Arrhythmias.
 Decrease cerebral blood flow confusion.

31. What is paradoxical aciduria ?
 Early in pyloric obstruction patient is loosing acid,
kidney excrete HCO3, so urine is alkaline.
 Later, volume depletion Hypokalemia, lead
to increase K Reabsorption and H secretion
leading to paradoxical aciduria.

32. Treatment of metabolic alkalosis
• Most of alkalosis is volume responsive.
Treatment by volume expansion by NaCL
Add KCL

33. Respiratory acidosis
 Retention of CO2 (alveolar ventilation).
Air way obstruction, pneumonia, pleural effusion, fracture ribs,
asthma .
 Depression of respiratory center (morphine -CNS injury)
 Upper abdominal incisions.
 Tense ascites, distension.
 Large PE ,fever.
 Myopathy.

34. Symptoms of respiratory acidosis?
 CO2 NARCOSIS
• Headache , blurred vision
• Anxiety ,restless , tremors
• Coma

36. 36
RESPIRATORY
ACIDOSIS / ALKALOSIS
COCO22 + H+ H22OO HH22COCO33 HH++
+ HCO+ HCO33
--
Respiratory Acidosis
Respiratory Alkalosis

41. Respiratory alkalosis
Hyperventilation
 Fever,pain,sepsis.
 Assisted ventilation.
 Head injury.
 Respiratory center lesion stroke, tumor
 Hysterical.
 Salicylate poisoning.
 Hypoxia, hypotension high altitude.
 Pulmonary embolism.

42. Symptoms and signs
Diziness,confusion,parathesia
Numbness around mouth
Treatment
Breathing into air bag
Hold your breathing

43. 43

47. 47
ACID – BASE DISORDERS
Clinical State Acid-Base Disorder
Pulmonary Embolus Respiratory Alkalosis
Cirrhosis Respiratory Alkalosis
Pregnancy Respiratory Alkalosis
Diuretic Use Metabolic Alkalosis
Vomiting Metabolic Alkalosis
Chronic Obstructive Pulmonary Disease Respiratory Acidosis
Shock Metabolic Acidosis
Severe Diarrhea Metabolic Acidosis
Renal Failure Metabolic Acidosis
Sepsis (Bloodstream Infection)
Respiratory Alkalosis,
Metabolic Acidosis

51. Respiratory and metabolic
component of acid base balance

52. Review Concepts Related
to Acid-Base Disturbances

53. These ABGs (pH-7.51, pCO2-28,
HCO3-26) show
a) Partially compensated respiratory acidosis
b) Uncompensated respiratory acidosis
c) Partially compensated metabolic acidosis
d) Normal acid-base balance
e) Uncompensated respiratory alkalosis
f) A combined metabolic and respiratory
alkalosis

54. These ABGs (7.51, pCO2 28, HCO3
26) show
a) Partially compensated respiratory acidosis
b) Uncompensated respiratory acidosis
c) Partially compensated metabolic acidosis
d) Normal acid-base balance
e) UNCOMPENSATED RESPIRATORY
ALKALOSIS ***
f) A combined metabolic and respiratory alkalosis

55. These blood gases (pH-7.25,
pCO2-51, HCO3-30) could be caused by
(select all that apply)
• Diarrhea
• Anxiety
• COPD
• Sepsis
• DKA
• Thoracic Surgery

56. These blood gases (pH-7.25, pCO2-51, HCO3-30)
(Partially compensated respiratory acidosis) could be caused by
• Diarrhea (causes metabolic acidosis)
• Anxiety (causes respiratory alkalosis)
• COPD (CAUSES RESPIRATORY ACIDOSIS)*
• An ASA overdose (causes metabolic acidosis or a respiratory
alkalosis)
• Sepsis (causes respiratory alkalosis)
• Cocaine overdose (causes respiratory alkalosis)
• DKA (causes metabolic acidosis)
• THORACIC SURGERY (CAN CAUSE
HYPOVENTILATION & RESP. ACIDOSIS)**

57. These ABGs (pH 7.29, pCO2-49, HCO3 26)
could be treated with
(select all that apply):
• Breathing into a paper bag
• Incentive spirometry
• Lomotil
• Albuterol
• Recommending the patient quit smoking

58. These ABGs (pH 7.29, pCO2-49, HCO3 26)
(uncompensated respiratory acidosis) could be treated with
• Breathing into a paper bag (used for a low pCO2)
• INCENTIVE SPIROMETRY ***
• Insulin (used in DKA a metabolic acidosis problem)
• TPN (used for starving cells a metabolic acidosis problem)
• Lomotil (used for diarrhea a metabolic acidosis problem)
• ALBUTEROL ***
• QUIT SMOKING REOMMENDATION ***

59. The following problems could lead to these ABGs
(pH-7.19, pCO2-33, HCO3-14):
(Select all that apply)
• Intestinal fistula
• Emphysema
• Anxiety attack
• Diabetic ketoacidosis
• Prolonged vomiting
• Shock
• Pneumonia
• NG suctioning
• Salicylate intoxication

60. The following problems could lead to these ABGs
(pH-7.19, pCO2-33, HCO3-14)
(partially compensated metabolic acidosis):
• INTESTINAL FISTULA ***
• Emphysema (causes respiratory acidosis)
• Anxiety attack (causes respiratory alkalosis)
• DIABETIC KETOACIDOSIS ***
• Prolonged vomiting (causes metabolic alkalosis)
• SHOCK ***
• Pneumonia (causes respiratory acidosis)
• NG suctioning (causes metabolic alkalosis)
• SALICYLATE INTOXICATION ***

61. Which of the following indicates
uncompensated metabolic alkalosis? (select
all that apply)
1. pH 7.32, PCO2 40, HCO3 19
2. pH 7.55, PCO2 20, HCO3 26
3. pH 7.55, PCO2 37, HCO3 30
4. pH 7.49, PCO2 35, HCO3 29
5. pH 7.30, PCO2 50, HCO3 29
6. pH 7.43, PCO2 53, HCO3 30
7. pH 7.44, PCO2 38, HCO3 26
8. pH 7.43, PCO2 32, HCO3 20

62. Which of the following indicates
uncompensated metabolic alkalosis?
1. pH 7.32, PCO2 40, HCO3 19 (uncomp met acid)
2. pH 7.55, PCO2 20, HCO3 26 (uncomp resp alk)
3. pH 7.55, PCO2 37, HCO3 30 ***
4. pH 7.49, PCO2 35, HCO3 29 ***
5. pH 7.30, PCO2 50, HCO3 29 (part comp resp acid)
6. pH 7.43, PCO2 53, HCO3 30 (comp met alk)
7. pH 7.44, PCO2 38, HCO3 26 (normal)
8. pH 7.43, PCO2 32, HCO3 20 (comp resp alk)

63. Which of the following problems could cause these
ABGs (pH 7.63, PCO2-24,
HCO3–23)? (Select all that apply)
• Fear
• Emphysema
• Vomiting
• Narcotic overdose
• Anxiety
• Atelectasis
• Renal failure

64. Which of the following problems could cause these
ABGs (pH 7.63, PCO2-24, HCO3–23)
(Uncompensated respiratory alkalosis?
• Fear ***
• Emphysema (causes respiratory acidosis)
• Vomiting (causes metabolic alkalosis)
• Narcotic overdose (causes respiratory acidosis)
• Anxiety ***
• Atelectasis (causes respiratory acidosis)
• Renal failure (causes metabolic acidosis)

65. Treatment for these ABGs (pH-7.55, PCO2 43,
HCO3 29) could include:
(Select all that apply)
• An ampule of NaHCO3 given after careful consideration
• Hyperventilation
• An anti-emetic to control vomiting
• Holding the administration of antacids
• Lomotil to control diarrhea
• Insulin to decrease the breakdown of fats

66. Treatment for these ABGs (pH-7.55, PCO2 43,
HCO3 29) (uncompensated metabolic alkalosis) could include:
• An ampule of NaHCO3 given after careful consideration (may be cautiously used in
acidosis)
• Hyperventilation (used in respiratory acidosis)
• ***An anti-emetic to control vomiting (STOPS
ACID LOSS)
• ***Holding the administration of antacids (STOPS
ADDING BASE)
• IPPB treatments (used in respiratory acidosis)
• Lomotil to control diarrhea (used in metabolic acidosis)
• Insulin to decrease the breakdown of fats (used in metabolic acidosis)

67. These ABGs (pH-7.13, PCO2-36,
HCO3-14) are interpreted as:
a) Partially compensated respiratory acidosis
b) Uncompensated metabolic acidosis
c) Combined respiratory and metabolic acidosis
d) Uncompensated metabolic alkalosis

68. These ABGs (pH-7.13, PCO2-36, HCO3-
14) are interpreted as:
a) Partially compensated respiratory acidosis
b) ***UNCOMPENSATED METABOLIC
ACIDOSIS
c) Combined respiratory and metabolic acidosis (there is no
respiratory acidosis, pCO2 is WNL)
d) Uncompensated metabolic alkalosis

69. The body could compensate for these ABGs
(pH-7.30, pCO2-40, HCO3-17) by: (select all
that apply)
• rBreathing in a shallow manner
• Producing urine with a high pH
• Increasing the respiratory rate
• Retaining more H+ ions
• Increasing respiratory depth
• Excreting more bicab

70. The body could compensate for these ABGs (pH-7.30,
pCO2-40, HCO3-17)
(Uncompensated metabolic acidosis) by:
• Breathing in a shallow manner (this would worsen the acidosis)
• Producing urine with a high pH (to increase the pH of the urine more HCO3 would be
excreted. This would be counter productive as there is not enough base in the system)
• **INCREASING THE RESPIRATORY RATE
ELIMINATES ACID
• Retaining more H+ ions (this would make it worse)
• ***INCREASING RESPIRATORY DEPTH
ELIMINATED ACID
• Excreting more bicarb (this would make it worse)

71. A patient with these ABGs (ph 7.24, pCO2-42,
HCO3-18) would likely have
(select all that apply)
• A feeling of fullness in the head
• Dizziness
• Slow, shallow respirations
• Tingling of the fingers and toes
• Warm, flushed skin
• Carpal-pedal spasm

72. A patient with these ABGs (ph 7.24, pCO2-
42, HCO3-18) Uncompensated metabolic acidosis) would
likely have
• A FEELING OF FULLNESS IN THE HEAD***
• Dizziness (alkalosis)
• Slow, shallow respirations (causes resp acidosis)
• Tingling of the fingers and toes (alkalosis)
• WARM FLUSHED SKIN ***
• Carpal-pedal spasm (alkalosis)

73. True or False
A patient with alkalosis can develop
hypokalemia as a complication.

74. TRUE
• If a person is alkalotic (has a low number of H+
ions in the blood), H+ ions will leave the cells.
To keep the number of positives balanced in the
cell, K+ will move in. This results in
hypokalemia.