I go on about how important it is to be able to interpret blood gases, with our junior doctors and Fellowship Candidates. It can really change your diagnostic capabilities in the emergency department. Here is an interesting case, where gases solve the problem.

A 30 yo woman is transferred to your emergency department. She has been in a small centre overnight, where she received 4 litres of Hartmans Solution. Here presentation had been of nausea and occasional vomiting, for nearly a week.

She is a mother of 6 children, currently breastfeeding twins and has no past medical history. She has had no major symptoms apart from th nausea and hasn’t eaten much.

Here initial results are as follows:

pH 7.083
pCO2 23.8
pO2 54
HCO3 7.1
Lact 1.04

Na 131, K 5.2, Cl 108, HCO3 7, Glc 6.6, U 2.6, Creat 7.6

GAS CALCULATIONS

We see that the patient has an anion gap(131-108-7=16) metabolic acidosis, with (pCO2 =1.5×7 + 8 + 2= 20)almost complete respiratory compensation. We can then use all the mnemonics we have i.e.., CATMUDPILES or CUTE DIMPLES, or what, or as I like to do, look at the most common causes.

The most causes of Anion Gap Metabolic Acidosis are:

Ketoacidosis
Lactic Acidosis
Renal Impairment
Intoxication
The patient has a normal glucose, lactate and urea and the calculated osmol is 272.

Here is where the trap can occur, in that we can rule out the most common cause of Ketoacidosis, which is Diabetic Ketoacidosis, however there are the next most common causes which are alcoholic and starvation ketoacidosis.

The patient’s measured ketones were 7+.

DIAGNOSIS

The combination of starvation and lactation(a high energy utilisation process) had led to Lactation Ketoacidosis(1) Starvation Ketosis on its own, is usually a benign condition. Glucose levels are maintained by glyconeogenesis. As liver glycogen stores become depleted, the energy must come from ketone bodies.

TREATMENT

It is a simple matter of stopping breastfeeding for a few hours and getting some glucose. The patient received 25mL of 50% glucose and within 16 hours here acid-base status had almost totally normalised.

Think of this condition in:

  • Lactating mothers who are unwell, or have diabetes(2)
  • Lactating mothers who are fasting for a procedure

References

  1. Gleeson S et al. Lactation Ketoacidosis:An Unusual Entity and a Review of the Literature. Perm J, Spring 2016;20(2):71-73
  2. Hudak S et al. Ketoacidosis ina non-diabetic woman who was fasting during lactation. Nutrition Journal(2015);14:117

Peter Kas