A 70-year-old male presents to the ED with a 2-week history of increasing dyspnoea, cough with altered sputum and fever. Past history includes chronic obstructive airways disease (COPD), lung cancer seven years ago treated with chemotherapy and radiation therapy with no sign of recurrence since.

Examination findings included RR 30 breaths/min, BP 110/70mmHg, HR 145 bpm, Temp 37.4ºC, anxious and distress but tired and peripherally cold and cyanosed.

CXR shows findings consistent with COPD and right lower lobe infiltrate.

The following arterial blood gas is taken one hour after receiving 2 litres of fluid resuscitation, antibiotics and bi-level non-invasive ventilation (NIV), at FiO2 = 1.0.

Parameter

Patient Value

   

Normal Adult Range

FiO2

1.0

       

pH

7.16*

7.35

– 7.45

 

PCO2

33 mmHg* (4.3 kPa)*

35

45 (4.6 – 6.0)

 

PO2

272 mmHg (38.5 kPa)

       

Bicarbonate

11 mmol/L*

22

30

 

Base Excess

-17 mmol/L*

-3 – +3

 

Sodium

138 mmol/L

135 – 145

 

Potassium

4.3 mmol/L

3.5 – 5.0

 

Chloride

121 mmol/L*

95

110

 

Glucose

13.1 mmol/L*

3.5 – 7.8

 

Lactate

6.4 mmol/L*

0.6 – 2.4

 

Haemoglobin

131 g/L*

135 – 175

 

Creatinine

150 micromol/L*

70

120

 

Six hours later the patient remains on NIV, is conscious, reports feeling slightly better, feet remain cyanosed, BP 105/72 mmHg, HR 108 bpm, RR 30 breaths/min, urine output 10 – 20 mL/hr and the following biochemistry profile is obtained:

Parameter

Patient Value

Normal Adult Range

Sodium

139 mmol/L

135 – 145

Potassium

5.5 mmol/L*

3.5 – 5.2

Chloride

110 mmol/L

95

– 110

Bicarbonate

12 mmol/L*

22

– 32

Urea

20.0 mmol/L*

2.7 – 7.8

Creatinine

220 μmol/L*

70

– 120

Estimated glomerular filtration rate (eGFR)

25 mL/min/1.73 m2*

> 90

Anion gap

22 mmol/L*

8 – 18

Total protein

57 g/L*

60

– 80

Albumin

27 g/L*

35

– 50

Total bilirubin

24.9 μmol/L

< 25

Alkaline phosphatase (ALP)

81 IU/L

30

– 110

Alanine transaminase (ALT)

6138 IU/L*

< 65

Aspartate transaminase (AST)

10122 IU/L*

< 50

g-Glutamyl transferase (GGT)

88 IU/L

< 90

C-reactive protein (CRP)

22.5 mg/L*

< 8

The patient’s haematology results are as follows:

Parameter

Patient Value

Normal Adult Range

Haemoglobin

87 g/L*

130 – 180

White cell count

2.1 x 109/L

4 – 11

Platelets

54 x 109/L

140 – 440

International normalised ratio (INR)

2.4

0.8 – 1.2

Activated partial thromboplastin time (APTT)

38 sec*

25 – 35

c)  What is your interpretation of these findings?            (20% marks)

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College Answer

c)

Acute anaemia, acute or chronic leucopaenia, acute or chronic thrombocytopaenia, coagulopathy with raised INR

No unifying diagnosis

Acute drop in haemoglobin over 2 hours is most likely due to haemorrhage or massive fluid infusion. Massive haemolysis is less likely given the bilirubin is not raised

Sepsis most likely cause of leucopaenia, thrombocytopaenia and raised INR

Acute liver failure may explain raised INR

Bone marrow failure would explain leucopaenia and thrombocytopaenia if they are chronic.

Any cause of bone marrow failure also accepted.

Discussion

This is the third part of this SAQ. Question 23.1 is an ABG interpretation question, and Question 23.2 is more about the differential diagnosis of deranged LFTs.

The following list of differentials can be reproduced from the pancytopenia chapter:

Differential Diagnosis of Pancytopenia
  • Infectious causes
    • EBV
    • HIV
    • Hep A, B, C
    • Parvovirus
    • CMV
    • Dengue fever
  • Neoplastic causes
    • Leukaemia
    • Marrow involvement from solid tumours
  • Drugs which cause pancytopenia
    • Methyldopa
    • Carbimazole
    • Acetazolamide
    • Chloramphenicol
    • Trimethoprim/sulfamethoxazole
    • Carbamazepine
    • Cytotoxic agents
  • Idiopathic causes
    • Pregnancy (may be a coincidental association)
    • Splenomegaly (sequestration)
    • Anorexia nervosa
    • Malnutrition
    • Myelofibrosis
    • Paroxysmal nocturnal haemoglobinuria
  • Congenital causes
    • Haemophagocytic lymphohistiocytosis
    • Fanconi anaemia
    • Shwachman-Diamond syndrome
  • Autoimmune causes
    • SLE
  • Traumatic causes
    • Radiation toxicity

These are all forms of a "unifying diagnosis" which is perhaps not appropriate here. The college answer seems to tolerate an individual list of differentials for each individual blood test abnormality, rather than expecting the candidates to connect the dots and make a diagnosis of haemophagocytic lymphohistiocytosis or some such. However, the trainees might not be aware of this. Some readers of Deranged Physiology have been in correspondence regarding this matter, and their profanity-laced comments suggest that to have a unifying diagnosis for these sorts of SAQs is one of their expectations. When asked "what is your interpretation of the findings", the correct answer should not be "these findings defy interpretation" or "just about anything, or several things, could be the cause".