2. ACID BASE DISTURBANCES
DR WAQAR ( MBBS, MRCP)
ASSISTANT PROFESSOR OF MEDICINE
MAAREFA MEDICAL COLLEGE

3. BASIC DEFINITIONS ACID : A compound which releases H+ ( HCL)
BASE ( alkali) : A compound which can accept H+
( Na HCO3)
pH : A measure of H+ activity. This number tells us how “acidic” or “alkaline”( or neutral) is the solution.

4. CO2 ALSO PRODUCES ACID ( CO2 + H2O = H2CO3 ( CARBONIC ACID)
ACIDS ARE PRODUCED DAILY IN THE HUMAN BODY ( LACTIC, ACETOACETIC, HYDROXYBUTYRIC )
CO2 ALSO PRODUCES ACID ( CO2 + H2O = H2CO3 ( CARBONIC ACID)
ALKALI IS ALSO PRESENT IN THE BODY (HCO3)
BUT
BLOOD IS NEITHER ACIDIC NOR ALKALOTIC

5. IN THE BLOOD, ACID & ALKALI ARE BALANCED
NORMAL pH OF BLOOD : TO 7.45
IN THE BLOOD, ACID & ALKALI ARE BALANCED
SO pH IS STABLE
A NORMAL BLOOD pH IS IMPORTANT FOR NORMAL CELL FUNCTIONS

6. Extra acid or alkali in the blood is immediately “bufferred” ( neutralized) by certain substances in the blood and then excreted. These substances are called BUFFERS. ( eg HCO3, organic acids)
eg : H + HCO H2CO H20 + CO2
BUFFERS : Substances which immediately absorb excess acid or alkali , so that the pH does not change

7. IF EXCESS ACID REMAINS IN THE BLOOD ACIDOSIS
IF EXCESS ALKALI REMAINS ALKALOSIS
pH CHANGES
ACIDOSIS CAUSES LOW pH ( lower than 7.35)
ALKALOSIS CAUSES HIGH pH ( higher than 7.45)

8. WHAT IS ACIDOSIS ? ACIDOSIS : * EXCESS ACID or LESS ALKALI
* pH IS LOW ( less than 7.35)
( normal pH is 7.35 to 7.45)
acid alkali acid alkali acid alkali
NORMAL
( A C I D O S I S )

9. WHAT IS ALKALOSIS ? EXCESS ALKALI ( BASE) OR LESS ACID
pH IS HIGH ( MORE THAN 7.45) (normal pH is 7.35 to 7.45)
ACID ALKALI ACID ALKALI ACID ALKALI
NORMAL ( ALKALOSIS )

10. IMPORTANT EQUATION H+ HCO3 H2CO3 CO2 + H2O HCO3 Handled by the kidney
CO Handled by the lungs

11. COMPENSATION
WHENEVER THE pH CHANGES IN A DISEASE, THE BODY TRIES TO BRING IT BACK TOWARDS NORMAL. THIS IS CALLED COMPENSATION.
COMPENSATION IS NOT 100% COMPLETE, SO pH DOES NOT RETURN TO COMPLETE NORMAL, IF THE DISEASE CONTINUES.

12. 3 THINGS WHICH TRY TO COMPENSATE
1) BUFFERS IN THE BLOOD : ACT WITHIN
seconds ( HCO3, Organic acids)
2) LUNGS : WITHIN SECONDS TO MINUTES
( BY KEEPING OR REMOVING CO2)
3) KIDNEYS : WITHIN HRS TO DAYS ( BY
handling HCO3 and H+)

13. SO PH 7.40 ------------------ ( ? ) PH 7.20 ------------------ ( ? )
( NORMAL IS 7.35 TO 7.45 )

14. IN DISEASE STATES, ACID – BASE BALANCE GETS DISTURBED, SO ACIDOSIS OR ALKALOSIS ( OR MIXED DISTURBANCES ) CAN OCCUR.

15. Things we need, to understand acid- base balance
ABG ( arterial blood gases)
SERUM ELECTROLYTES ( NA, K, CL, HCO3)
ABG report is written as follows:
ABG : pH/ pCO2/ pO2/ HCO3
eg / 45 mmHg / 78 mmHg / 25meq
For our discussion, forget about O2

16. SOME NORMAL VALUES Blood pH: * 7.35 to 7.45 Blood pCO2 :
* Also 7.35 mmHg to 7.45mmHg
3) Blood HCO3:
* 22 to 28 meq/L ( slightly different in various
labs)

17. ACIDOSIS RESPIRATORY ACIDOSIS METABOLIC ACIDOSIS
(DUE TO HIGH CO2 ) (DUE TO:
a) Excess acid production
b) Decreased acid excre-
- tion from the kidneys
c) Loss of HCO3

18. RESPIRATORY ACIDOSIS * IT IS DUE TO HYPOVENTILATION
* DUE TO HYPOVENT., CO2 CANNOT BE EXCRETED , SO
PCO2 RISES ( think of CO2 as an acid)
ETIOLOGIES :
* RESP. CENTER DEPRESSION ( MORPHINE)
* NEUROMUSCULAR PATHOLOGIES ( KYPHOSIS, RESP
MUSCLE PARALYSIS )
* LUNG DISEASE ( COPD)

19. RESPIRATORY ACIDOSIS PH IS LOW ----- < 7.35
PROBLEM IS IN RESP. SYS. OR LUNGS CO2 RETAINED
HIGH CO ACIDOSIS( CO2 + H2O = H2CO3)
Eg PH / PCO2 / HCO3
7.30/ 50mmHg/ 30 ( Norm pCO2 35 to 45, HCO3 22 to
28)

20. COMPENSATION ( in resp.acidosis)
KIDNEYS RETAIN MORE HCO3
SO, THERE IS COMPENSATORY RISE IN HCO3
END RESULT :
* pH : low
* PCO2 : high
* HCO3 : high ( DUE TO COMPENSATION)

21. S/S OF RESP. ACIDOSIS S/S USUALLY OCCUR IF IT IS ACUTE
HEADACHE, RESSTLESSNESS, DYSPNEA
PROGRESSES TO HYPER-REFLEXIA, COMA
RESP. ACIDOSIS MAY BE SEEN IN LATE STAGES OF ASTHMA EXACERBATION, WHEN THE PATIENT GETS TIRED
IT IS SEEN IN COPD PATIENTS EVEN AT BASELINE STATUS (CHRONIC ACIDOSIS)

22. TREATMENT OF RESP. ACIDOSIS
1) TREAT THE CAUSE
2) DON’T GIVE HCO3.
IT WILL COMBINE WITH H+ IN THE BODY AND PRODUCE MORE CO2 WHICH CAN NOT BE ELIMINATED. SO, CONDITION WILL BE WORSE
HCO3 + H = H2CO H2O + CO2
3) MAY NEED MECHANICAL VENTILATION ( ventilation takes out CO2 from the lungs)

23. RESPIRATORY ALKALOSIS
pH IS HIGH
PROBLEM IS WITH RESPIRATORY RATE
HYPERVENTILATION EXCESS CO2 IS ELIMINATED
LOW CO ALKALOSIS
Eg : PH / PCO2/ HCO3
7.50 / / 18

24. COMPENSATION KIDNEYS LOSE MORE HCO3
SO, THERE IS COMPENSATORY FALL IN SERUM HCO3
END RESULT :
* pH : high
* pCO2 : low
* HCO3 : low ( due to compensation)

25. CAUSES OF RESPIRATORY ALKALOSIS
ANXIETY
RESPIRATORY CENTER STIMULATION all these
HYPOXIA ( LIVING AT HIGH ALTITUDES ) cause
PATIENTS ON VENTILATORS MAY DEVELOP hyper-
ASPIRIN POISONING ventilation
ABHA IS A HIGH ALTITUDE CITY. LIVING THERE CAN CAUSE:
a) Resp. Alkalosis

26. RESP. ALKALOSIS S/S ACUTE RESPIR. ALKALOSIS CAUSES LOW Ca, & K
S/S INCLUDE :
* LIGHTHEADEDNESS
* CONFUSION
* SIEZURES
* HYPERVENTILATION
* TETANY ( DUE TO LOW Ca)

27. TREAT MENT OF RESPIRATORY ALKALOSIS
TREAT THE MAIN CAUSE
CHANGE THE VENTILATOR SETTINGS
CAN TRY “REBREATHING EXHALED” AIR IN A PAPER BAG

29. SO REMEMBER THAT:. IN RESP. ACIDOSIS, CO2 WILL BE HIGH. IN RESP
SO REMEMBER THAT: * IN RESP. ACIDOSIS, CO2 WILL BE HIGH * IN RESP. ALKALOSIS, CO2 WILL BE LOW

30. METABOLIC ACIDOSIS PH IS LOW --------- < 7.35
MAIN PROBLEM NOT IN RESPIRATION
PROBLEM : TOO MUCH METABOLIC ACID IS PRODUCED IN THE BODY, OR IT CANNOT BE EXCRETED OR
TOO MUCH ALKALI ( HCO3) IS LOST FROM THE BODY
LOW HCO3
Eg: PH/ PCO2/HCO / 30 / 18 ( normal is 22 to
26)

31. COMPENSATION LUNGS EXCRETE MORE CO2
SO, THERE IS COMPENSATORY FALL IN PCO2
END RESULT :
* PH : low
* HCO3 : low ( main problem)
* PCO2 : low ( due to compensation)

32. TYPES OF METABOLIC ACIDOSIS
HIGH ANION GAP NORMAL ANION GAP

33. WHAT IS ANION GAP ? CATIONS : Na+, K+ / ANIONS : HCO3-, Cl-
Normally, the sum of cations should be equal to sum of anions.
But Na + K is > HCO3 +Cl
This difference is called Anion Gap.
It is actually the unmeasured anions in the blood ( albumin, phosphates etc)
NORMAL A.G = 8 TO 16 meq ( Na +K) – (Cl + HCO3)
IN SOME CONDITIONS, IT GETS HIGH ( SOME TYPES OF METABOLIC ACIDOSIS) & IN OTHERS, IT IS NORMAL

34. TYPES OF METABOLIC ACIDOSIS
HIGH “ ANION GAP” NORMAL “ ANION GAP”
ETIOLOGIES ETIOLOGIES
M methanol * Diarrhea loss of
U uremia * Ileostomy HCO3
D diab.ketoacidosis
P paraldehyde * Renal tubular acidosis (RTA)
I infection/sepsis ( type 1, 2 &4)
L lactic acidosis
E ethanol * Acetazolamide ( a diuretic)
S salicylate poisoning(aspirin)

35. S/S ( METABOLIC ACIDOSIS)
HEADACHE, MENTAL STATUS CHANGES, RESTLESSNESS
COMA MAY OCCUR

36. TREATMENT OF METABOLIC ACIDOSIS
TREAT THE CAUSE
* Drug toxicity (aspirin, methanol)
* ketoacidosis : treat accordingly
* infection/sepsis
* Diarrhea
* Lactic acidosis : iv fluids, treat the cause
* Uremia : NaHCO3 tab / Dialysis ( remember renal failure ?)
I.V. HCO3 CAN BE GIVEN IN METABOLIC ACIDOSIS
IF NEEDED

37. RENAL TUBULAR ACIDOSIS
A GROUP OF RENAL DISORDERS ( PROBLEM IN TUBULES)
FOUR TYPES.
OVERALL RARE. TYPE 4 IS THE MOST COMMON
METABOLIC ACIDOSIS WITH NORMAL A.G.
TYPE 4 RTA SEEN IN DM

38. METABOLIC ALKALOSIS IT IS ALKALOSIS SO, PH IS HIGH ( > 7.45 )
NO PRIMARY PROBLEM IN RESP.
ACCUMULATION OF EXCESS ALKALI IN THE BODY OR
LOSS OF ACID
Eg : PH / PCO2 /HCO3
7.50 / 48 / 35

39. COMPENSATION LUNGS EXCRETE LESS PCO2 SO, COMPENSATORY RISE IN PC02
END RESULT :
* pH : high
* HCO3 : high ( main problem)
* pCO2 : high ( due to compensation)

40. CAUSES OF METABOLIC ALKALOSIS
VOMITING, N/G TUBE SUCTION ( loss of acid)
EXCESS INTAKE OF NaHCO3
DIURETICS ( thiazides, loop diuretics)
ALL DIURETICS CAUSE METABOLIC ALKALOSIS EXCEPT ACETAZOLAMIDE ( DIAMOX) WHICH CAUSES ACIDOSIS)

41. S/S CEREBRAL DYSFUNCTION * Restlessness * confusion, lethargy
* arrhythmias

42. TREATMENT IF VOMITING OR NG SUCTION GIVE i.v. N/S
If DIURETICS ARE THE CAUSE, GIVE i.v. N/S
IF HIGH INTAKE OF HCO3, Stop IT.
If pH > 7.7, give isotonic HCL thru central vein

43. SO, REMEMBER THAT:
IN METABOLIC ACIDOSIS, HCO3 IS LOW
IN METABOLIC ALKALOSIS, HCO3 IS HIGH

44. THANK YOU
HOPE YOU FOUND IT EASY