BASICS OF ACID BASE DISORDERS
INCLUDING FORMULAS AND RANGES
AND APPROACH TO DIAGNOSIS
formular for ph
pH = negative Log ( H + )
Classification
¨Metabolic Acidosis
¨Metabolic Alkalosis
¨
¨Respiratory Acidosis
¡Acute
¡Chronic
¨Respiratory Alkalosis
¡Acute
¡ChronicSTEP 1
Determine if
¨ Acidaemia or
¨Alkalaemia
pH Normal 7.35 to 7.45
< than 7.35 acidaemia
> than 7.45 alkalaemia
Step 2Identify primary disorder
Metabolic or respiratory
BUT CAN USE THE EQUATIONS AND SEE WHICH HAS CHANGED TO CAUSE THE PH ABNORMALITY AND THATS THE PRIMARY DISORDERStep 3
Compensation
¨Appropriate
¨If not appropriate think of a mixed disorder
Practice examples to get used to it
CAUSES OF ALL SIX ACID BASE DISORDERS
CHECK IMAGE
METABOLIC ACIDOSIS
METABOLIC ALKALOSIS
ACUTE RESPIRATORY ACIDOSIS
CHRONIC RESPIRATORY ACIDOSIS
RESPIRATORY ALKALOSIS (ACUTE AND CHRONIC)
ANION GAP
- Refers to the difference between the anions and Cations
- Na – ( Cl + HCO3 )
- Why is it important
Helps to identify the types of Metabolic Acidosis
ONLY USEFUL IN METABOLIC ACIDOSES
Correction for hypoalbuminaemia
¨AG adjusted = AG measured + + 2.5 (4 - Albumin g/l )
(vs that in calcium?)INTEPRETATION
>Metabolic Acidosis
>Elevated anion gap acidosis
1Diabetic ketoacidosis
2Lactic acidosis
3Acidosis of advanced renal failure
ú
> Normal Anion gap Acidosis ( Hyperchloraemic acidosis )
1Severe diarrhoea
2renal tubular acidosis
BUT THERE ARE MORE CAUSES (SEE MNEMONIC)
Renal tubular acidosis
- Type I ( Distal renal tubular acidosis )
- Type II ( proximal renal tubular acidosis )
- Type IV ( Hypoaldosreronism )
RANGE IS 12 =/- 4 IF K NOT INLCUDED
BUT 16 +/- 4 IF K IS INCLUDED
Tutorial in Endocrinology 7 - Acid Base Disorders
Intake 34
Tutorials in endocrinology 7
Acid Base disorders
Using the given data give a complete analysis of the following ABG reports.
1. 1. pH - 7.28
PaCO2 - 34
HCO3 - 18
2. 2. pH - 7.15
PaCO2 - 36
HCO3 - 14
3 . 3 pH - 7.52
PaCO2 - 50
HCO3 - 30
4. 4. pH - 7.30
PaCO2 - 35
HCO3 - 18
Na - 132 mEq/ l
Cl - 94 mEq/l
5 . A 55 year old patient with who is being managed for decompensated cirrhosis has the following ABG
pH - 7.51
PaCO2 - 43
HCO3 - 28
What abnormality is seen in the ABG?
What is the cause for the abnormal ABG in this patient?
6. A 13 year old boy is a diagnosed patient with epilepsy but is otherwise normal. He is brought to the ER unconscious following a epileptic seizure. O/e he has a GCS of 4 and there are bilateral coarse crepitations over both lungs.
His ABG is given below
pH - 7.28
PaCO2 - 55
PaO2 - 70
HCO3 - 26
Explain the reason for the above ABG
7. A 62 year old lady C/o pain in the small joints for 5 years and dry mouth of 6 months duration. Her ABG is given below
pH - 7.30
PaCO2 - 34
PaO2 - 98
HCO3 - 18
Na - 134
Cl – 106
Analyse the ABG
What is the primary and secondary cause for this ABG
8. A 55 year old heavy alcoholic who is also a diabetic is brought to the OPD with H/o fever and cough. O/e he has a BP of 100/70, and shallow respiration with rate of 10 / min at rest and the chest X ray revels bilateral bronchopneumonia. His ABG and some other investigations are given below.
pH - 7.18
PaCO2 - 34
PaO2 - 85
HCO3 - 12
Na - 125
Cl – 95
Blood sugar 560 mg /dl
Serum Albumin 2 g/dl
Give a complete analysis of the above ABG
9. A 65 year old lady gives a H/o chronic persistent backache
An X ray of the spine shows a lytic lesion in L2 vertebra.
An ABG gives the following results.
pH - 7.23
PaCO2 - 33
PaO2 - 98
HCO3 - 16
Na - 125
Cl – 98
Analyse the ABG and give a possible reason for the abnormal ABG
What is the primary and secondary cause for this ABG
10. A 22 year old female is brought to the OPD after ingestion of 30 tabs of Aspirin.
Serial ABGs are performed.
Arrange these ABG reports in the likely order they were performed