Investigations

1st investigations to order

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Result
Test

Take a venous (rather than arterial) blood gas in all patients with suspected DKA.[42]

  • Use the pH to determine the severity of DKA.

    • pH ≥7.0 indicates mild or moderate DKA.

    • pH <7.0 indicates severe DKA. Discuss these patients with critical care.

  • Hyperkalaemia is common.[46]

    • Use the potassium level on venous blood gas to replace potassium if ≤5.5 mmol/L. Discuss with critical care if potassium is <3.5 mmol/L.

  • Calculate the plasma osmolality. [ Osmolality Estimator (serum) ]

    • Plasma osmolality is high (>320 mmol/kg) in DKA and is an indication of dehydration.[53][61]

Practical tip

Assessment of electrolytes should be done at or near the bedside.[42] 

Venous blood gas measurements are widely used instead of arterial blood gas measurements and evidence from case studies suggests there is sufficient agreement between them, when combined with other clinical findings, to use a venous blood gas to guide initial treatment.

A clinical review article aimed to answer the question “can venous blood gas analysis replace arterial blood gas analysis in emergency care?”[90]

  • Venous blood gas testing may have a lower risk of serious adverse events (e.g., vascular occlusion or infection), is less painful for the patient, and is technically easier to perform than arterial blood gas testing.

  • There is little difference in pH values between venous and arterial samples (based on 13 studies; 2009 participants, with 3 studies [295 patients] in patients with DKA).[91]

  • Bicarbonate values also show close agreement between venous and arterial samples (8 studies; 1211 patients).[91]

  • Agreement for PCO2 is poor and unpredictable (8 studies; 965 patients), but a venous PCO2 ≤45 mmHg (6 kPa) reliably excludes clinically significant hypercarbia (4 studies; 529 patients; 100% sensitivity).[91]

  • Agreement on lactate is close enough to categorise as high or normal (3 studies; 338 patients).[92] 

  • Evidence regarding arteriovenous agreement for base excess is unclear (2 studies; 429 patients; only 1 study reporting close agreement).[93][94]

  • If data from the venous blood gas does not appear to match the patient’s clinical condition, an arterial blood gas should be performed.[90]

Result

metabolic acidosis with a raised anion gap

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Result
Test

Use urinary ketones if near-patient blood ketone testing is unavailable.[42] [51]

Practical tip

Assessment of ketones should be done at or near the bedside.[42] 

  • Order laboratory measurements in certain circumstances, such as when blood ketone meters are ‘out of range’.

Practical tip

Bear in mind that a patient’s medications can cause errors in detecting ketone bodies.[46]

Some drugs, such as the ACE inhibitor captopril, contain sulfhydryl groups that can react with the reagent in the nitroprusside test (used to test for ketone bodies) to give a false-positive reaction. Therefore, use clinical judgement and other biochemical tests in patients who are taking these medications.

Result

ketonaemia (ketones ≥3.0 mmol/L)[42]

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Hyperglycaemia (blood glucose >11.1 mmol/L) is common.[52] 

  • This blood glucose cut-off is recommended in the 2020 Joint British Diabetes Societies (JBDS) guideline "Diabetes at the front door" and supersedes the 11.0 mmol/L cut-off recommended in the 2013 JBDS guideline "The management of diabetic ketoacidosis in adults".[42][52]

Be aware that some patients can present with euglycaemic DKA (EDKA) and have a normal blood glucose.[65]

Practical tip

Assessment of glucose should be done at or near the bedside.[42] 

  • Order laboratory measurements in certain circumstances, such as when blood glucose meters are ‘out of range’.

Result

hyperglycaemia (blood glucose >11.1 mmol/L)

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Result
Test

Hyponatraemia is common in DKA.[42]

  • Hypernatraemia with hyperglycaemia indicates severe dehydration, however.

Hyperkalaemia is common but hypokalaemia is an indicator of severe DKA.[46]

  • Hypokalaemia on arrival indicates severe total-body potassium deficit and is an indicator of severe DKA. This is because the total body potassium concentration is low due to increased diuresis.

  • Hyperkalaemia is due to an extracellular shift of potassium caused by insulin insufficiency, hypertonicity, and acidosis.

Hypomagnesaemia and hypophosphataemia may also be present.[42][66]

Practical tip

Assessment of glucose should be done at or near the bedside.[42] 

Result

  • hyponatraemia and hyperkalaemia are common but hypokalaemia is an indicator of severe DKA[42][46]

  • may show hypomagnesaemia and hypophosphataemia[42][66]

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Result
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Leukocytosis is common in DKA and correlates with blood ketone levels.[46]

However, leukocytosis more than 25 × 10⁹/L (25,000/microlitre) may indicate infection and requires further investigation.[46]

Result

leukocytosis

Investigations to consider

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Order if near-patient testing for ketones is unavailable or you suspect a urinary tract infection.[42][51]

Result

ketonuria (more than 2+ on standard urine sticks); may be positive for glucose[95]

  • other findings include leukocytes and nitrites in the presence of infection, and myoglobinuria and/or haemoglobinuria in rhabdomyolysis[95][96][97]

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Result
Test

Use to look for cardiac precipitants of DKA such as myocardial infarction and cardiac effects of electrolyte abnormalities.[98]

Ensure continuous cardiac monitoring and involve senior or critical care support if:[42][17]

  • There is persistent hypotension (systolic blood pressure <90 mmHg) or oliguria (urine output <0.5 ml/kg/hour) despite intravenous fluids

  • Glasgow Coma Scale <12 [ Glasgow Coma Scale ] 

  • Blood ketones >6 mmol/L

  • Venous bicarbonate <5 mmol/L

  • Venous pH <7.0

  • Potassium <3.5 mmol/L on admission

  • Oxygen saturations <92% on air

  • Pulse >100 bpm or <60 bpm

  • Anion gap >16 [ Anion Gap ]

  • The patient is pregnant or has heart or kidney failure or other serious comorbidities.

    • DKA in pregnancy can result in significant morbidity and mortality for both the mother and the fetus.[69]

Result

  • abnormal T or Q waves or ST segment changes in myocardial infarction[98]

  • evidence of hypokalaemia (U waves) or hyperkalaemia (tall ‘peaked’ T waves) may be present[99][100]

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Result
Test

Order in all women of childbearing age.

Result

positive in pregnancy

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Result
Test

Amylase is elevated in most patients with DKA.[46]

Serum lipase is usually normal in DKA.[46]

  • This may differentiate DKA from pancreatitis (lipase level will be elevated in patients with pancreatitis). However, mildly elevated serum lipase level in the absence of pancreatitis has also been reported in patients with DKA.

Result

amylase may be elevated; serum lipase is usually normal[46]

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Result
Test

Order troponin T or I if you suspect myocardial infarction as a precipitant.[101]

Result

elevated with myocardial infarction

Test
Result
Test

Elevated if rhabdomyolysis is present. This is common in DKA and present in around 10% of patients.[96]

Result

elevated with rhabdomyolysis

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Order if there are reduced oxygen saturations.[42]

Result

  • signs of pulmonary oedema are pleural effusions, interstitial and alveolar oedema, prominent superior vena cava, Kerley B lines, and dilated upper lobe blood vessels[102]

  • consolidation occurs in pneumonia

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Result
Test

Use to screen for an underlying hepatic precipitant of DKA. Abnormal LFTs indicate underlying liver disease (e.g., non-alcoholic fatty liver disease or congestive heart failure).[103][104]

Result

elevated with liver disease

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Result
Test

Order these if there are signs of infection. The most common are pneumonia and urinary tract infections.[56]

Patients with DKA who have an infection are usually normothermic or hypothermic due to peripheral vasoconstriction so fever may not be seen.[53]

Result

positive if infection present

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