1. The document discusses acid-base balance and arterial blood gases (ABGs), including definitions of pH, the Henderson-Hasselbalch equation, and the three main mechanisms of acid-base regulation: chemical buffers, respiration, and renal. 2. It examines the causes, classifications, and compensation mechanisms of metabolic and respiratory acidosis and alkalosis. Mixed acid-base disorders are also addressed. 3. The importance of considering the patient's history and clinical presentation when interpreting ABG results is emphasized to help identify underlying etiologies and guide treatment.

1. ABG FROM THEORY TO
THERAPY

2. WHAT IS PH ?
pH=-log[H+] concentration,
which is read:
the pH is equal to minus the log of the H+
concentration.
For example is the H+ concentration is very low, lets say
about 0.0000001M, then the pH is
pH= -log[.0000001] whis is the same as -log[1 X 10-7]
the term log[1 X 10-7] = -7
- (-7) = 7

3. WHAT IS PSTAND FOR ?
The exact meaning of the "p" in "pH" is
disputed
Power :-
o according to the Carlsberg
Foundation, pH stands for "power of
hydrogen".
o It has also been suggested that the
"p" stands for
the German Potenz (meaning
"power"),
o others refer
to French puissance (also meaning
"power", based on the fact that the
Carlsberg Laboratory was French-
Pondus :-
Another suggestion is that the "p"
stands for the Latin terms pondus
hydrogenii (engl. quantity of
hydrogen)

4. WHAT IS OPTIMUM PH FOR OUR
BODY?

5. WHAT IS HOMEO-STASIS ?
is the property of a system in which a
variable (e.g. the concentration of a
substance in solution, or its
temperature etc.) is actively
regulated to remain very nearly
constant.

7. HOMEO-STASIS ….. DISEASE
imbalanceBalance
hypothermiahyperthermi
a
lossProductionTemperatur
e
cachexiaobesitylossProductionEnergy
alkalosisacidosisLossProductionH ion
HypoHyperLoss (
shift)
Gain (
retention)
Electolytes (
CA ,K , Na
……
Bleedingthrombosisfibrinolysi
s
CoagulationBlood
Hemostasis

8. FROM WHERE WE CAN GET H IONS
?
Most hydrogen ions originate from cellular
metabolism
Breakdown of phosphorus containing proteins
releases phosphoric acid into the ECF
Anaerobic respiration of glucose produces
lactic acid
Fat metabolism yields organic acids and
ketone bodies
Transporting carbon dioxide as bicarbonate
releases hydrogen ions

9. Life is a long
acid trip

10. WHAT IS ACID AND WHAT IS THE
BASE ?
volatileOrganic
Carbonic1- hydrochloric
acid
2- lactic acid
3- DNA RNA
4- amino acids
5- fatty acids

11. WHAT IS DIFFERENCE BETWEEN
ION AND ANION ? Ion :-
Carry charge in its outer
surface

12. WHY FIXED PH IS IMPORTANT ?
Electrical
Neutrality

13. ELECTRICAL NEUTRALITY
Nerve
conduction
Muscle
contraction
Platelets
function
Electrolytes
homeostasis
Dissociation
of oxygen

14. WHAT IS DIFFERENCE BETWEEN
ACIDEMIA AND ACIDOSIS ?
AcidosisAcidemia
Primary physiologic process that may
lead to acidemia
 hypoperfusion  lactic acidosis
 hypoventilation  respiratory
acidosis
Ph may be normal
or
or
Blood PH less than
7.35

15. WHAT IS DIFFERENCE BETWEEN
ALKALEMIA AND ALKALOSIS ?
AlkalosisAlkalemia
Primary physiologic process that may lead
to alkalemia
 diarhia  metabolic alkalosis
 hyperventilation  respiratory
alkalosis
Ph may be normal
or
Blood PH more than
7.45

16. NORMAL PH BUT ABNORMAL ABG ,
WHY ?
Compensation
Concomitant
disorders
1- over or under
compensation (
secondary disorders )
2- tertiary disorders

17. HYDROGEN ION REGULATION =
COMPENSATION
Concentration of hydrogen ions is regulated
sequentially by:
1. Chemical buffer systems act within seconds
2. The respiratory center in the brain stem acts within
1-3 minutes
3. Renal mechanisms require hours to days to affect pH
changes

18. 1- BUFFERS …SECONDS
1. A buffer is a solution whose
function is to minimize the
change in pH when a base or an
acid is added to the solution
2. Most buffers consist of a weak
acid (which releases H+ ions) and
a weak base (which binds
H+ ions)
3. If an acidic solution is added to a
buffer solution, the buffer will
combine with the extra H+ ions
and help to maintain the pH
4. If a basic solution is added to a
buffer solution, the buffer will
release H+ ions to help maintain
the pH

19. 2- RESPIRATORY …MINUTES
1. physiological buffering system
2. There is a reversible equilibrium
between:
 Dissolved carbon dioxide and water
 Carbonic acid and the hydrogen and
bicarbonate ions
 CO2 + H2O « H2CO3 « H+ + HCO3¯
3. When hypercapnia or rising plasma H+
occurs:
 Deeper and more rapid breathing expels
more carbon dioxide
 Hydrogen ion concentration is reduced
4. Alkalosis causes slower, more shallow
breathing, causing H+ to increase

20. 3- RENAL …DAYS

21. CAN ABG DISORDERS AFFECT
OXYGENATION

22. INDICATIONS OF ABG TEST
Muakkassa and coworkers
studied the relationship between the presence of an arterial line and
ABG sampling . These authors demonstrated that patients’ with an
arterial line had more ABGs drawn than those who did not regardless
of the value of the PaO2, PaCO2, APACHE II score or the use of a
ventilator. In this study, multivariate analysis demonstrated that
presence of an
arterial line was the most powerful predictor of the number of
ABGs
drawn per patient independent of all other measures of the
patient’s clinical status

24. WHAT IS YOUR METHOD ?

25. OUR METHOD WILL BE ……!!!!!!!

26. P & P ……. !!!!!!!!!!!
Patient Paper

27. WHY THE PATIENT IS IMPORTANT ?
History S & S
Diabetic
CKD
Intoxication
Shock
Respiratory
Hyperventilation
Shift of Oxy-Hb curve to
right
Cardiovascular
Myocardial depression
Tissue catecholamine
resistance
Pulmonary
vasoconstriction
Hyperkalaemia
Metabolic acidosis

28. WHY THE PATIENT IS IMPORTANT ?
History S & S
COPD
Opoid
After general anethesia
Vasodilation, sweaty,
tachycardic, mydriasis,
asterixis
Confusion
Drowsy and ALOC
Respiratory
acidosis

29. WHY THE PATIENT IS IMPORTANT ?
History S & S
Vomiting
Diarrhia
Diuretics
Hypovolemic
hypokalemic
Shift O2 dissociation curve to left
(increased affinity for Hb-O2)
 Right shift with increase TEMP,
2-3 DPG, H+
Hypokalemia, hypocalcaemia,
hypochloraemia
Symptoms related to
HYPOcalcaemia and
HYPOkalaemia
 Dizzy, light-headed
 Chest tightness
 Anxiety,
dysphasia…..laryngospasm
Metabolic
alkalosis

30. WHY THE PATIENT IS IMPORTANT ?
History S & S
Pain
Fever
stress
Agitated
Early in athma
PE !!!
Associated changes
 HYPOcalcaemia, HYPOkalaemia,
HYPOphosphatemia
 Decreased Co2 reduces H+
binding, increases negative charge
of proteins and increases binding
of calcium to proteins
 Thus reducing ionised calcium
 Hypocalcaemia with tetany and
carpopedal spasm
Shift 02 dissociation curve to the left
(Alkalosis) (Increased affinity of Hb
for O2)
Respiratory
alkalosis

31. Prediction – actual
analysis
Mixed
disorder

33. ANATOMY OF ABG PAPER
A ………. Acid
B ………. Base
C ……... Contents of oxygen and Co2
D ……... Delivery of O2 …..
E …….... Electrolytes ( ?)
F ……… Fetal HB and other forms of
abnormal HB
G ……... glucose
H ……... Hemoglobin
I ……… Inhaled CO

34. 5 STEPS
1.Confirm
2.Classify
3.Calculate
4.Causes
5.Correct

35. 1- CONFIRM
Patient Errors
1.Same patient
2.Same date
3.Same time
Lab Errors
1. Calculate the H ion
concentration from the
equation
2. This calculated H ion
should be cross ponded
to H ion in the ABG
report

36. VALIDITY
1-
2- subtract the last two digits
of the pH (e.g., 20 in pH 7.20)
from 80; this value is
approximately equal to the H+
concentration

37. 2- CLASSIFY ….. WHAT IS PRIMARY
? 7.4
alkalosisNorrmalAcidosis
More than 7.457.35 – 7.45LESS than 7.35Ph
Less than 3535 -- 45More than 45PaCO2
(Respiratory)
More than 2622 – 26LESS than 22HCO3
(Metabolic)
ROME

38. 3- CALCULATE …..
1- compensation

39. ANION GAP
Na + ( 1.6 × g –
100/100 )
Na – ( Cl +
Hco3 )
12 ± 4
AG + 2.5 ( 4 –
Albumin )

40. NOT ONLY IN METABOLIC ACIDOSIS
Critical care secret page 311

41. LOW ANION GAP
1- Decrease in unmeasured anions (albumin, dilution)
2- Increase in unmeasured cations (multimyeloma (cationic IgG paraprotein),
hypercalcaemia, hypermagnesaemia, lithium OD, polymixin B)
bromide OD (causes falsely elevated chloride measurements)
Atrovent (Ipratropium) bromide
Avelox (moxifloxacin)
Celebrex (celecoxib)
Cipro (ciprofloxacin)
Crestor (rosuvastatin)
Diflucan (fluconazole)
Lescol (fluvastatin)
Levaquin (levofloxacin)
Lexapro (escitalopram)
Lipitor (atorvastatin)
Pulmicort (budesonide)
Risperdal (risperidone)
Tobra Dex (from dexamethasone)

42. URINE AG
For non-gap metabolic acidosis, calculate the urine
anion gap
UAG = UNA + UK – UCL
If UAG>0: renal problem
If UAG<0: nonrenal problem (most commonly GI)
……. neGUTive !

43. 3- CALCULATE
2- tertiary
disorders

44. 4- CAUSES

45. CAUSES OF METABOLIC ACIDOSIS
Metabolic
acidosis
HAGMA NAGMA

46. HAGMA …… OSMOLAR gap
Measured –
calculated
15

48. isopro
panol
Ethylene
glycol
methan
ol
AcetoneGlycolate (
false ↑
lactate )
Oxylate (
crystals )
Formaldeh
yde
Formic
acid
metabolit
es
ElevatedEarly :- elevated
Late :- normal
OG
NormalEarly :- normal
Late :- elevated
AG
AKIBlindnessClues

50. HAGMA
HOSG
1- methanol
2- ethanol
3- diuritics (mannitol)
4- isopropyl alcohol
5- ethylene glycole
NOSG
1-lactic acidosis
2- renal failure
3- DKA

52. NAGMA
POSITIVE UAG
RENAL
NEGUTIVE UAG
GIT

53. 1- dirrhia
2- colostomy
3- fistula
4- uretric
diversion
5-
hyperalimentaion

54. CAUSES OF METABOLIC ALKALOSIS

56. CAUSES OF RESPIRATORY
ACIDOSIS

57. CAUSES OF HYPERCAPNIA

58. CAUSES OF RESPIRATORY
ALKALOSIS TACHYPNIA

59. 5- CORRECT THE CAUSES
1- sodium bicarb
2- acetazolamide
Please see evidence based book
pp 340

60. HOW TO
DECREASE THE
ABUSE
SEE PAUL MRIK
PP 330

61. Thank you