a) List the problems interpreting the following ABG results and explain the reasons why:
i. Sample from a patient with severe hypothermia. (30% marks)
ii. Delayed sample processing by 45 minutes. (20% marks)
i. Outline the causes of pseudohypernatremia or pseudonormonatremia in critically ill patients. (20% marks)
ii. List three causes of factitious hyponatraemia in critically ill patients. Give an example of each. (30% marks)
This question was poorly answered, with many candidates not answering the questions asked. For example, in part a), many candidates listed the clinical effects of hypothermia rather than its effects on the ABG analysis. Knowledge of sodium measurements and hyponatraemia were either at a superficial level, incorrect, or omitted.
Problems with the interpretation of an ABG from a severely hypothermic patient:
Problems with the interpretation of an ABG which suffered a 45 minute delay in processing:
Causes of pseudohypernatremia:
Causes of factitious hyponatremia ("pseudohyponatremia" is also an accepted term)
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Muys, Mariolein, Frank Martens, and Nico Callewaert. "Pseudohypernatremia at the intensive care unit: a cause for concern?." ACTA CLINICA BELGICA. Vol. 69. STE 1C, JOSEPHS WELL, HANOVER WALK, LEEDS LS3 1AB, W YORKS, ENGLAND: MANEY PUBLISHING, 2014.
Hankinson, S. E., et al. "Effect of transport conditions on the stability of biochemical markers in blood." Clinical Chemistry 35.12 (1989): 2313-2316.
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