Question 12.2 | Deranged Physiology

Question 12.2

You are asked to see a 73-year-old female on the ward. She was admitted to the Emergency Department in a dishevelled state.

She has the following vital signs and investigation results:

Temperature: 34.5°C

Blood pressure: 80/40 mmHg

Glasgow Coma Score: 11

Parameter	Patient Value	Adult Normal Range
Fi02	0.28
pH	7.26*	7.35 - 7.45
P02	62 mmHg (8.3 kPa)
PC02	37.0 mmHg (4.7 kPa)	35.0 -45.0 (4.6 - 6.0)
sp02	92%
Bicarbonate	16.0 mmol/L*	22.0 - 26.0
Base Excess	-10.0 mmol/L*	_2.0 _ +2.0
Lactate	3.1 mmol/L*	0.5 - 1.6
Sodium	128 mmol/L*	135 - 145
Potassium	3.1 mmol/L*	3.5 -5.0
Chloride	90 mmol/L*	95- 105
Glucose	3.2 mmol/L*	3.5 -6.0
Urea	13.0 mmol/L*	3.0 - 8.0
Creatinine	132 umol/L*	45 — 90
Creatinine Kinase	1500 U/L*	55 - 170

Haemoglobin	80 g/L*	120 - 160
White Cell Count	15.0 x 109/L*	4.0 - 1 1.0
Platelet count	250 x 109/1-	150 - 350

a) Comment on the acid base status and ECG abnormalities

(ECG show below)

ECG from LITFL

(30% marks) b) List the two most likely differential diagnosis. (20% marks)

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College answer

a)
Primary metabolic acidosis
Associated respiratory acidosis, or inadequate compensation
Increased anion gap. (22)
Delta ratio 1.2 –pure high anion gap acidosis

ECG: low voltage
Relative bradycardia
Prolonged QT

b)
Myxoedema coma.
Sepsis

Discussion

Acid base status, in detail:

There is acidaemia
The CO₂ is within normal range, which is inappropriate (it should be low)
There is metabolic acidosis, as the SBE is -10
There is also a respiratory acidosis: the expected CO₂ is 30 (or 32 by the Boston rules)
The anion gap is 25.1, or 22 sans potassium. Either way, the lactate of 3.1 does not fully explain it.
The delta ratio is either 1.6 or 1.25, but either way it points to a pure HAGMA.

ECG abnormalities

Bradycardia
Long PR interval
Long QT interval
Borderline widened QRS
Low voltage QRS in the limb leads

Overall, the ECG is consistent with hypothermia. Which the patient has. And with ... one other thing.

So... those two most likely differentials?

Well. One of them HAS to be myxoedema coma.

How can one be so confident? It's easy, when the college lifted their ECG directly from the LITFL page on ECG changes in hypothyroidism. Which is excellent: as that work is covered by the Creative Commons license, this offers the author a rare opportunity to reproduce the original college image without fear of the CICM intellectual property stormtroopers.

The other differential could easily be sepsis, MI, acute kidney injury due to prolonged lie and rhabodomyolysis, and so on.

References

Zhang, Yiyi, et al. "Thyroid hormones and electrocardiographic parameters: findings from the third national health and nutrition examination survey." PloS one 8.4 (2013): e59489.

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