A 68-year-old Type 2 diabetic with a history of alcohol abuse is admitted with abdominal pain and the following results:

Parameter

Patient Value

Normal Adult Range

pH

6.87*

7.35 - 7.45

PaCO2

8 mmHg (1.1 kPa)*

35 - 45 (4.7-6.0 kPa)

PaO2

149 mmHg (20 kPa)

Bicarbonate

1.4 mmol/L*

22 – 26

Lactate

16 mmol/L*

< 2

Sodium

142 mmol/L

134 – 145

Potassium

4.7 mmol/L

3.5 – 5.1

Chloride

107 mmol/L*

95 – 105

Urea

14 mmol/L*

3.4 – 8.9

Creatinine

170 μmol/L*

60 – 110

Aspartate Aminotransferase

60 U/L*

< 40

Alanine Aminotransferase

70 U/L*

< 40

Lactate Dehydrogenase

1400 U/L*

50 - 150

Total bilirubin

20 μmol/L

< 20

Glucose

6.5 mmol/L*

3.0 – 5.4

Serum osmolality

314 mOsm/kg*

275 – 295

a) Give three likely diagnoses.

b) List two additional investigations that you would perform based on the above information.

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College Answer

a)

  • Ischaemic bowel
  • Metformin induced lactic acidosis
  • Cardiogenic shock 
  • Thiamine deficiency
  • Pancreatitis
  • OR Any reasonable diagnosis

b)

  • Two of the following investigations:
    • Diagnostic laparoscopy or laparotomy
    • CT abdomen
    • Troponin
    • Red cell transketolase,
    • Lipase

Discussion

Let us dissect these results systematically.

  1. The A-a gradient cannot be calculated, as no FiO2 is supplied to us
  2. There is acidaemia
  3. The PaCO2 is compensatory
  4. The SBE is not supplied, but the bicarbonate is 1.4, suggesting a severe metabolic acidosis
  5. The respiratory compensation is adequate and lurks around the natural limits of human respiratory compensation for metabolic acidosis- the expected PaCO2(1.4 × 1.5) + 8 = 10.1mmHg
  6. The anion gap is raised:
    (142) - (107 + 1.) = 34, or 38.7 when calculated with potassium
    The delta ratio, assuming a normal anion gap is 12 and a normal bicarbonate is 24, would therefore be (34 - 12) / (24 - 1.) = 0.95 (.e. mainly a high anion gap acidosis)
  7. Urinary pH and electrolytes are not supplied, and are irrelevant.

So, what is making this diabetic drunk so acidotic?

Well, the lactate of 16 is probably contributing. But it does not account for the whole of the anion gap.

The college kindly gives us a measured osmolality, so we can calculate the osmolar gap:

314 - (142 × 2 + 14 + 6.5) = 9.5

Thus, toxic alcohol ingestion (eg. ethylene glycol or methanol) is less likely.

Three likely culprits of any of the below causes is all the college wanted, or any reasonable diagnosis.

  • Alcoholic ketoacidosis
  • Lactic acidosis due to gut ischaemia
  • Lactic acidosis due to biguanide use
  • Lactic acidosis due to thiamine deficiency
  • Lactic acidosis due to maligancy
  • Pancreatitis
  • Cardiogenic shock
  • Sepsis

Thus, investigations could include any two of the following:

References

References

Smeets, E. H. J., H. Muller, and J. De Wael. "A NADH-dependent transketolase assay in erythrocyte hemolysates." Clinica chimica acta 33.2 (1971): 379-386.

Lonsdale, Derrick, and Raymond J. Shamberger. "Red cell transketolase as an indicator of nutritional deficiency." The American journal of clinical nutrition 33.2 (1980): 205-211.

FENNELLY, JAMES, et al. "Red blood cell-transketolase activity in malnourished alcoholics with cirrhosis." The American journal of clinical nutrition 20.9 (1967): 946-949.

Talwar, Dinesh, et al. "Vitamin B1 status assessed by direct measurement of thiamin pyrophosphate in erythrocytes or whole blood by HPLC: comparison with erythrocyte transketolase activation assay." Clinical chemistry 46.5 (2000): 704-710.

Rossouw, J. E., et al. "Red blood cell transketolase activity and the effect of thiamine supplementation in patients with chronic liver disease." Scandinavian journal of gastroenterology 13.2 (1978): 133-138.