A 34 year old woman is transferred to your hospital with a history of a prolonged generalized tonic-clonic convulsion. She is intubated and ventilated. Blood samples have been collected for a full blood count, biochemistry and a coagulation profile. Her initial non contrast CT brain shows  bilateral intracerebral hemorrhages. Her arterial blood gases and a haematology report are provided below

Parameter

Patient values

Normal range

FiO2

0.5

pH

7.15

7.35-7.45

PaCO2

35 mmHg (4.6 kPa)

35-45 mmHg (4.7-6.0 kPa)

PaO2

105 mmHg (14 kPa)

75-98 mmHg (10-13 kPa)

Bicarbonate

10.3 mmol/l

22-26 mmol/l

Parameter

Patient  values

Normal range

Hb

78 G/L

(130-150)

WCC

14.5 x 106/mm3

(4.0-11.0)

Platelets

43 x 106 /mm3

(150-300)

Blood picture: Thrombocytopaenia, fragmented cells and reticulocytosis

Coagulation profile: Normal

a) List the abnormalities on the blood gases. Give the most likely cause of each abnormality

b) Based on the history, CT scan and the hematology report, provide three possible differential diagnoses and give reasons

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College Answer

a)

Metabolic acidosis: Lactic acidosis induced by status epilepticus

Respiratory acidosis (alternatively inappropriate respiratory compensation) - Central hypoventilation (alternative : inappropriate mechanical ventilation)

Increased A-a gradient : Aspiration pneumonitis (alternative : neurogenic pulmonary oedema)

b)

TTP

Eclampsia

HUS

Vasculitis

? Meningoencephalitis (lower mark)

There is evidence of MAHA with low platelets.

Discussion

This question is identical to Question 15.2 from the second paper of 2011, and Question 22.2 from the second paper of 2008.