# Question 9.3

A 25-year-old patient presents with significant wheeze and shortness of breath after accidental inhalation of vapour whilst cleaning a bathroom. On arrival in the Emergency Department continuous nebulized salbutamol was commenced.

This arterial blood gas was taken 6 hours into the treatment.

 Parameter Patient Value Adult Normal Range FiO2 0.4 pH 7.27 7.35 – 7.45 pO2 70 mmHg (9.2 kPa) pCO2 36.0 mmHg (4.7 kPa) 35.0 – 45.0 (4.7 – 6.0) SpO2 93% Bicarbonate 16.0 mmol/L* 22.0 – 26.0 Lactate 8.8 mmol/L* 0.5 – 1.3 Sodium 145 mmol/L 135 – 145 Potassium 2.9 mmol/L* 3.5 – 5.0 Chloride 111 mmol/L* 95 – 105 Glucose 9.7 mmol/L* 3.5 – 6.0

Explain the results and give reasons for the abnormalities, showing your calculations where appropriate.    (30% marks)

Not available.

## Discussion

The abnormalities are:

• The A-a gradient is raised: (713 × 0.4) - (36  / 0.8) - 70 = 170.
• There is mild acidaemia
• There is a metabolic acidosis; the SBE is not offered, but the bicarbonate is 16.
• The CO2 is slightly more than expected. We cannot apply the SBE equation here, but empirical rules for respiratory compensation in metabolic acidosis suggest the CO2 should be (1.5×16)+8 = 32 58.5 mmHg, i.e. there is also a very mild respiratory acidosis here.
• The anion gap is raised,  (145-(111+16))= 18
• The delta ratio is (18-12)/(24-16) = 0.7, suggestive of a mixed normal anion gap and high anion gap acidosis
• There are also electrolyte abnormalities:
• Hyperlactataemia
• Hypokalemia
• Hyperglycaemia

The possible explanations are:

• Hypoxia is due to some alveolar injury from the cleaning product vapours (clearly this patient mixed a chlorinated bleach with an acid like household ammonia or vinegar, liberating a cloud of chlorine gas)
• The chlorine absorption can also account for the elevated chloride, contributing to the NAGMA component of the metabolic acidosis
• The hyperglycaemia and hyperlactataemia are due to the salbutamol, and the lactate is contributing to the HAGMA component of the metabolic acidosis)

## References

Jones, Frederick L. "Chlorine poisoning from mixing household cleaners." JAMA 222.10 (1972): 1312-1312.