Hyperglycaemia can be confirmed quickly by a high capillary blood glucose measurement, but it is important to ensure that reagent strips are fresh, that reflectance meters are well maintained and that staff are trained in their use. Ketone measurements are also possible on capillary blood, or urine if available. Treatment can then be started while the results of further tests, such as plasma electrolytes, are awaited. Suggested laboratory investigations are listed in Table 2.3. Arterial or capillary blood should ideally be used for acid-base assessment to confirm the acidosis, but where the facilities are not available venous pH and bicarbonate may be reasonable substitutes. Subsequently, acid-base status can be monitored using venous or non-arterialised capillary blood gases, since, although these will show a slightly higher CO2 and bicarbonate, and slightly lower pH, the differences are not usually clinically significant.
Table 2.3 Suggested laboratory investigations in diabetic ketoacidosis
Venous plasma glucose Sodium, potassium, chloride, phosphate, calcium
Plasma urea (BUN), creatinine
Blood gases, pH, bicarbonate
Urine culture Blood culture, CXR, throat swab Plasma amylase
To confirm capillary result There may be artefactual lowering of sodium due to hyperlipidaemia Chloride will help to define type of acidosis particularly during treatment
Creatinine may be falsely elevated by hyperketonaemia; not usually a problem with modern chemical pathology laboratories
If oxygen saturation is available, a venous or capillary sample is sufficiently accurate, otherwise use arterial sample Bedside blood ketone measurement may be helpful but insufficient evidence yet in children
PCV may support clinical evidence of dehydration
Leucocytosis extremely common in ketoacidosis and does not necessarily imply infection
If clinically indicated
Only if clinically indicated
If abdominal pain severe and continues after adequate initial treatment
FBC = full blood count; PCV = packed cell volume; CXR = chest X-ray; BUN = blood urea nitrogen.
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