Laboratory assessment

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

Investigation

Notes

Venous plasma glucose Sodium, potassium, chloride, phosphate, calcium

Plasma urea (BUN), creatinine

Blood gases, pH, bicarbonate

Urinary ketones

FBC, PCV

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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