A 40-year-old patient with a background of alcohol abuse presents with a history of 8 days of diarrhoea and vomiting.


The following results are obtained: 

Parameter

Patient Value

Adult Normal Range

Sodium

129 mmol/L*

135 – 145

Potassium

5.1 mmol/L*

3.5 – 5.0

Chloride

105 mmol/L

95 – 105

Bicarbonate

14.0 mmol/L*

22.0 – 26.0

Urea

16.3 mmol/L*

3.0 – 8.0

Creatinine

659 µmol/L*

45 – 90

Glucose

7.0 mmol/L*

3.5 – 6.0

Magnesium

1.49 mmol/L*

0.75 – 0.95

Albumin

27 g/L*

35 – 50

Protein

45 g/L*

60 – 80

Total bilirubin

148 µmol/L*

< 26

Conjugated bilirubin

143 µmol/L

Aspartate transferase

2250 U/L*

< 35

Alanine transferase

1218 U/L*

< 35

Alkaline phosphatase

43 U/L

30 – 110

g-Glutamyl transferase

68 U/L*

< 40

Ionised calcium

0.97 mmol/L*

1.10 – 1.35

Calcium corrected

1.95 mmol/L*

2.12 – 2.62

Phosphate

1.11 mmol/L

0.80 – 1.50

Creatinine Kinase

500 U/L*

55 – 170

Iron Level

34 µmol/L

6 – 35

Ferritin

181,900 µg/L*

30 – 400

Transferrin

0.6 g/L*

2.0 – 3.6

Ammonia

78 µmol/L*

16 – 60

Parameter

Patient Value

Adult Normal Range

Haemoglobin

132 g/L

120 – 160

White Cell Count

5.2 x 109/L

4.0 – 11.0

Platelet count

24 x 109/L*

150 – 350

Parameter

Patient Value

Adult Normal Range

Prothrombin time

20.0 sec*

12.0 – 16.5

International normalised ratio (INR)

1.8*

0.9 – 1.3

Activated    partial    thromboplastin time (APTT)

77.0 sec*

27.0 – 38.5

Fibrinogen

0.7 g/L*

2.0 – 4.0

D-Dimer

66.0 mg/L*

< 0.5

a)    What is the acid-base disturbance in this patient? (20% marks)

b)    What are the likely causes in this context? (30% marks)
 

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College answer

a)
Metabolic acidosis- Anion gap= 116-(67+14) = 35 Delta ratio= 23/10=2.3
HAGMA with metabolic alkalosis OR Increased SID

b)
Metabolic alkalosis – due to vomiting- Acid loss and contraction alkalosis. HAGMA-
Lactic acidosis from hypovolaemia or bowel obstruction/sepsis, Ketoacidosis from starvation/alcohol.
 

Discussion

In some sort of a structured fashion:

  • The bicarbonate is low, suggesting a metabolic acidosis
  • The anion gap is (116-67-15) = 34
  • The delta ratio is therefore (34-12)/(24-15) =  2.44; 
    in other words, this is a mixed HAGMA and metabolic alkalosis.
  • The calculated osmolality is (116 × 2) + 2.9 + 6.8 = 241.7, and so the osmolar gap is minimal (254-241.7 = 12.3)

Causes of HAGMA appropriate to this scenario include:

  • Toxic alcohol ingestion (classically, methanol) - though the low osmolar gap makes this less likely
  • Alcohol-induced or starvation-associated ketoacidosis (more likely)
  • Lactic acidosis due to the hypovolemic state, and the failure of the liver to metabolise it 

The metabolic alkalosis can be attributed to the vomiting and diarrhoea, and more directly to the aldosterone excess which develops in states of volume depletion.

References