5

1. Acid base disorders
Final year
Dr. Shahid Anwar
Associate Professor Of Nephrology

2. SEQ. 1
• A 65 year old male, known case of chronic kidney
disease presented in the emergency department with
shortness of breath for the last 3 days. Pulse 100 bpm.
B.P 140/80 mmhg, Respiratory rate 32/min, Temp 98.8 F.
Systemic examination is unremarkable. His lab reports
showed BUN 100 mg/dl, Serum creatinine 3.5 mg/dl, pH-
7.1, HCO3- 10, Na-140 mmol/l, Potassium- 4.5 mmol/l
1. What is the most likely acid base abnormality (2)
2. What are the causes of normal anion gap metabolic
acidosis(4)
3. What are the complications of IV sodium bicarbonate
(4)

3. SEQ. 1
• A 65 year old male, known case of chronic kidney disease
presented in the emergency department with shortness of
breath for the last 3 days. Pulse 100 bpm. B.P 140/80
mmhg, Respiratory rate 32/min, Temp 98.8 F. Systemic
examination is unremarkable. His lab reports showed BUN
100 mg/dl, Serum creatinine 3.5 mg/dl, pH- 7.1, HCO3- 10,
Na-140 mmol/l, Potassium- 4.5 mmol/l
1. What is the most likely acid base abnormality (2)
2. What are the causes of normal anion gap metabolic
acidosis(4)
3. What are the complications of IV sodium bicarbonate (4)

4. Normal Values
Average
• pH 7.4
• PaCO2 40
• HCO3 24
• PaO2 100
• SaO2 97%
• Chloride 104
• AG 12
Range
• 7.35 – 7.45
• 35 – 45
• 21 – 28
• 93 – 108
• 95 – 99
• 98 – 106
• 8 - 16

5. Interpretation Of Arterial Blood Gases
ABGs

6. 1. Define individual components
• pH Normal Euphaemia
high (> 7.44) Alkalaemia
low (< 7.35) Acidaemia
• HCO3 high (>24) Metabolic Alkalosis
low (<24) Metabolic Acidosis
• PCO2 high (>40) Respiratory Acidosis
low (<40) Respiratory Alkalosis

7. 2. Decide primary component
• The acid base disorder that is pointing
towards pH is primary component.
• Primary components can be one or more

8. 3: check compensation
Disorder pH Primary Compensation
Metabolic
Acidosis ↓ ↓ HCO3 ↓PCO2
Alkalosis ↑ ↑ HCO3 ↑PCO2
Respiratory
Acidosis ↓ ↑PCO2 ↑ HCO3
Alkalosis ↑ ↓PCO2 ↓ HCO3

9. 4. Check anion Gap
AG = Na – (Cl + HCO3)
Normal value= 6-12

10. HCO3 HCO
HCO3
High AG metabolic
acidosis
Hyperchloremic
metabolic acidosis
Normal
AG = Na – (Cl + HCO3)
NV (6-12)
AG
CL CL
CL
AG
AG

11. Causes of metabolic acidosis
High AG
MUD PILES
• M- Methanol
• U- Uraemia
• D- DKA
• P- Paraldehyde
• I- INH
• L- Lactic acidosis
• E- Ethanol
• S- Salicylates
Normal AG or Hyperchloremic
HARD UP
• H- Hyperalimentation
• A- Acetazolamide
• R- RTA
• D- Diarrhoea
• U- Ureterosigmoidostomy
• P- Pancreaticoduodenal
fistula

12. Case -2
• A middle aged man was found unconscious on
road. He was taken to emergency. Pulse
110/min, B.P: 100/60, afebrile, R.R: 22/min.
systemic examination unremarkable.
• Labs:
– Na: 130, K: 5.5, Cl: 100,
– pH: 7.2, HCO3: 10, PCO2: 19
– BSR: 100 mg/dl, BUN: 20 mg/dl,
– serum osmolality: 300 mosm/l
– Urine C/E: normal
• What is the diagnosis?

13. 1. Check acid base disorder (metabolic acidosis)
2. Calculate anion gap (high AG)
3. Look for cause
– Calculate serum osmolality
– 2×Na + BSR/18 + BUN/2.8 (NV 280 – 295)
– 2×130 + 100/18 + 20/2.8 = 280 mosm/l
– Compare with measured serum osmolality
– Calculated: 280
– Measured: 300
– If gap is more than 10 - yes
• Unmeasured osmoles: methanol, ethanol, ethylene glycol,
mannitol, glycine
• High AG metabolic Acidosis secondary to alcohol
intoxication

14. Case- 3
• A middle aged man was found unconscious on
road. He was taken to emergency. Pulse 110/min,
B.P: 100/60, afebrile, R.R: 22/min. systemic
examination unremarkable.
• Labs:
• Na: 130, K: 5.5, Cl: 100,
• pH: 7.2, HCO3: 10, PCO2: 19
• BSR: 300, BUN: 20
• serum osmolality: 290 mosm/l
• Urine C/E:
– proteinuria ++, glucose+++, ketones ++
• What is the diagnosis?

15. • Check acid base disorder (metabolic acidosis)
• Calculate anion gap (high AG)
• Look for cause
– Calculate serum osmolality
– 2×Na + BSR/18 + BUN/2.8 (NV 280 – 295)
– 2×130 + 300/18 + 20/2.8 = 293 mosm/l
– Compare calculated with measured serum osmolality
– Calculated: 293
– Measured: 290
– If gap is more than 10 - no
• Urine ketones + with high BSR
• High AG metabolic Acidosis secondary to Diabetic
ketoacidosis

16. High AG
MUD PILES
• M- Methanol
• U- Uraemia
• D- DKA
• P- Paraldehyde
• I- INH
• L- Lactic acidosis
• E- Ethanol
• S- Salicylates
Measured & calculated
serum osmolality
BUN, S. Creatinine raised
Urine ketones, BSR
History
History of TB/Drugs
Clinical history, S. Lactate