Diabetic ketoacidosis

Diabetic ketoacidosis (DKA) is defined as the presence of a metabolic acidosis (venous bicarbonate less than 15 mmol/L or pH less than 7.3) and significant ketosis (plasma beta hydroxybutyrate greater than 3 mmol/L or ketonuria greater than 2+ on standard urinalysis sticks) in the presence of a random plasma glucose greater than 11 mmol/L or known diabetes. The latter criterion is important as the entity of normoglycaemic DKA is well recognised and is a diagnostic pitfall for the unwary, especially in pregnancy.

Assessment of ketosis

Traditionally, this is by urinalysis giving a result on a 0-4+ scale.

Urinalysis, however, has technical short comings including the fact that the sodium nitropruside reaction does not pick up the main ketone body in DKA - beta hydroxy-butyrate. It only detects acetone and aceto acetate. Furthermore, urinalysis necessarily provides a somewhat retrospective look at what ketosis was like when the urine in the bladder was made rather than a real-time readout.

For these reasons, there is a move towards blood ketone assessment in many hospitals which may be performed with near-patient testing apparatus not unlike BM machines using a capillary blood sample. Results are given in mmol/L, >3 mmol/L is indicative of significant ketosis, <0.3 mmol/L is indicative of complete resolution of ketosis.

Acid base status

Conventionally arterial blood gasses were used, however, the most recent national guidelines on management of DKA advocate use of venous blood gases.

This is preferable from the patient’s point of view as it is less painful, carries significantly less risk from the procedure itself and unless the patient also has a gas exchange problem as well as DKA (e.g. pneumonia, PE or such like) provides no additional useful information.

Most blood gas analysers will also give a reasonable estimate of serum K+.

FBC

This is part of the 'septic screen' and also an important baseline. However, leukocyte count rises in direct proportion to the degree of ketosis.

Us+Es

This is essential in order to assess the baseline K+ as well as giving a biochemical indication of dehydration and of renal function.

Glucose

Laboratory glucose is an essential baseline investigation. 

HbA1c

Although not directly relevant to the management of DKA, it is useful opportunity to assess the overall level of glycaemic control.

Amylase

Measure this only if you are seriously concerned that the patient may have pancreatitis - it can often be elevated as much as x5 upper limit of normal due to the DKA itself.

LFTs

A useful baseline.

CXR

This is usually performed as part of the 'septic screen'.

Urinary hCG

This should be performed in all female patients between menarche and menopause presenting with DKA.

Urinalysis

The presence of nitrites, leukocytes, protein and blood should prompt a sample being sent for microscopy, culture and sensitivity.

Blood cultures

These should also be sent if there is suspicion that there is a septic precipitant of the episode.

ECG

A baseline ECG is a mandatory investigation in the patient with DKA.

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