4.1
The following results are from a 35-year-old female with fever, shortness of breath and known renal calculi.
Parameter |
Patient Value |
Adult Normal Range |
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Fi02 |
0.21 |
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pH |
7.30* |
7.35 - 7.45 |
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pC02 |
25.0 mmHg (3.3 kPa)* |
35.0 - 45.0 (4.6 - 6.0) |
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p02 |
117 mmHg (15.6 kPa) / |
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Sp02 |
98% |
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Bicarbonate |
12.0 mmol/L* / |
22.0 - 26.0 |
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Base Excess |
-15.0 mmol/L* |
-2.0 - +2.0 |
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Lactate |
1.7 mmol/L* ., |
0.5 - 1.6 |
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Sodium |
135 mmol/L |
135 - 145 |
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Potassium |
4.1 mmol |
3.5 - 5.0 |
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Chloride |
105 mmol/L |
95 - 105/ |
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Glucose |
5.8 mmol/L |
3.5 - 6.0 |
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Creatinine |
324 µmol/L* |
45 - 90 |
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Urea |
29.0 mmol/L* ' |
3.0 - 8.0 |
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Albumin |
42 g/L |
35 - 50 |
a) Describe the acid base abnormalities. (30% marks)
b) Suggest one likely aetiology. (20% marks)
a) Describe the acid base abnormalities.
Metabolic acidosis
Anion gap elevated (18)
Delta ratio 0.5 – so coexisting normal AG acidosis
b) Suggest one likely aetiology.
Renal tubular acidosis (type 1) secondary to renal stones for NAGMA and urosepsis for HAGMA
Guidance – any plausible answer that addresses all the acid-base abnormalities
A systematic approach:
The urea and creatinine are significantly raised, suggesting acute kidney injury.
The lactate is minimally raised, suggesting that retained non-volatile acids of renal failure are mainly responsible for the raised anion gap.
Given the history of renal calculi and fever, one might surmise that this lady probably suffers from an untreated renal tubular acidosis (as RTA Type I and Type II are associated with nephrolithiasis) and now has obstructive uropathy because of the stones. The fever may mean the stones are infected, but we got no information about any of that, so it falls in the realm of wild speculation. "Any plausible answer", etc.