What are the diagnostic criteria for DKA?

The Joint British Diabetes Societies guideline requires all three of: established or new diabetes mellitus; capillary blood ketones of 3 mmol/L or more on an approved meter, or ketonuria of ++ or more on standard urine sticks; and a venous bicarbonate below 15 mmol/L and/or a venous pH below 7.3. If there is ketonaemia without acidosis, intravenous insulin may not be needed but fluids and a subcutaneous correction may be.

Do you give fluid or insulin first in DKA?

Fluid first. The JBDS guideline commences intravenous 0.9% sodium chloride and starts the fixed rate intravenous insulin infusion only after fluid therapy has been started. Time zero is defined as the moment intravenous fluids are commenced.

What rate of insulin does JBDS use in DKA?

A fixed rate intravenous insulin infusion at 0.1 units per kilogram per hour, calculated on actual or estimated body weight and given by pump as 50 units of human soluble insulin made up to 50 ml with 0.9% sodium chloride. A bolus of intramuscular insulin at 0.1 units/kg is given only if there is a delay in setting up the infusion.

When do you add glucose to the fluids in DKA?

When the blood glucose falls below 14.0 mmol/L, the JBDS guideline commences 10% glucose at 125 ml per hour alongside the 0.9% sodium chloride, and asks you to consider reducing the intravenous insulin infusion rate to 0.05 units/kg/hr. Euglycaemic DKA starts the 10% glucose straight away because the glucose is already below 14.

What is euglycaemic DKA and why does it matter surgically?

Euglycaemic DKA is ketoacidosis in a person with diabetes whose glucose is normal or only mildly raised, and the JBDS guideline treats it in exactly the same way as hyperglycaemic DKA. It matters because it is associated with the SGLT inhibitor class of drugs, which JBDS says should be stopped if DKA occurs, and because a normal glucose can falsely reassure the team.

DKA in the Surgical Patient — CST Interview Clinical Station Answer

Q: How is potassium replaced in DKA?

The JBDS guideline gives no potassium when the serum level is over 5.5 mmol/L, 40 mmol per litre of infusion solution when it is 3.5 to 5.5 mmol/L, and asks for senior review when it is below 3.5 mmol/L because additional potassium is needed. Potassium is not added to the first litre of saline given over the first hour.

Q: When has DKA resolved?

The JBDS guideline continues the fixed rate insulin infusion until the ketone measurement is less than 0.6 mmol/L and the venous pH is over 7.3 and/or the venous bicarbonate is over 18 mmol/L. It expects the ketonaemia and acidosis to have resolved by 24 hours in most people, and says not to rely on urinary ketone clearance.

Q: Should a patient in DKA go to theatre?

The JBDS guideline says it may be necessary to consider a surgical cause for deterioration, and that if surgery is required there must be an urgent senior multidisciplinary discussion on the optimum time to operate. That balances the danger of anaesthetising an uncorrected ketoacidosis against the fact that the acidosis will not correct until the source is controlled.

Diabetic ketoacidosis in the surgical patient is the combination of hyperglycaemia, ketonaemia and acidosis, and on a surgical ward it is nearly always driven by a surgical problem: sepsis, an acute abdomen, or an operation itself. According to the Joint British Diabetes Societies for Inpatient Care guideline, revised in March 2023, the diagnosis needs all three of known or new diabetes, capillary ketones of 3 mmol/L or more or ketonuria of ++ or more, and a venous bicarbonate below 15 mmol/L and/or a venous pH below 7.3. The station tests whether you treat the ketoacidosis and hunt the surgical trigger at the same time.

Key takeaways

The JBDS diagnostic criteria for DKA are all three of: established or new diabetes; capillary ketones 3 mmol/L or more, or ketonuria of ++ or more; and venous bicarbonate below 15 mmol/L and/or venous pH below 7.3
JBDS starts intravenous 0.9% sodium chloride first and commences the fixed rate intravenous insulin infusion only after fluid therapy has been started, at 0.1 units/kg/hr
JBDS replaces potassium at 40 mmol per litre of infusion when serum potassium is 3.5 to 5.5 mmol/L, gives none above 5.5 mmol/L, and asks for senior review below 3.5 mmol/L
The JBDS targets are a ketone fall of at least 0.5 mmol/L per hour, or a bicarbonate rise of at least 3.0 mmol/L per hour, or a glucose fall of at least 3.0 mmol/L per hour
When glucose falls below 14.0 mmol/L, JBDS starts 10% glucose at 125 ml per hour alongside the saline and asks you to consider reducing the insulin infusion to 0.05 units/kg/hr
JBDS states that a surgical cause for deterioration may need to be considered, and that if surgery is required there must be an urgent senior multidisciplinary discussion on the optimum time to operate

How do I recognise DKA in a surgical patient?

Recognise DKA in a surgical patient by testing ketones in anyone with diabetes who is unwell, rather than waiting for a classic presentation of vomiting, abdominal pain, Kussmaul breathing and dehydration.

DKA and the acute abdomen imitate each other. Ketoacidosis itself causes abdominal pain, vomiting and a raised white cell count, while an acute abdomen precipitates ketoacidosis, so both have to be assessed together.

The JBDS guideline also warns about euglycaemic DKA, where the glucose is normal or barely raised. It is treated in exactly the same way, and it is the presentation associated with the SGLT inhibitor class of drugs.

How is DKA diagnosed, and what makes it severe?

DKA is diagnosed when all three JBDS entry criteria are met: known or new diabetes, capillary ketones of 3 mmol/L or more or ketonuria of ++ or more, and a venous bicarbonate below 15 mmol/L and/or a venous pH below 7.3.

The JBDS guideline then lists the features that may indicate severe DKA, and any one of them should trigger intensive monitoring and consideration of a level 2 or high dependency environment.

Blood ketones over 6.0 mmol/L, bicarbonate below 5.0 mmol/L, or venous or arterial pH below 7.0
Hypokalaemia on admission, meaning a potassium under 3.5 mmol/L
A Glasgow Coma Scale under 12, or an abnormal AVPU score
Oxygen saturation below 92% on air, assuming normal baseline respiratory function
Systolic blood pressure below 90 mmHg, or a pulse over 100 or below 60 beats per minute
An anion gap above 16

JBDS adds that a drowsy individual in the context of DKA is seriously concerning and requires critical care assessment, with consideration of a nasogastric tube and airway protection to prevent aspiration.

What is the immediate management of DKA in the first hour?

The immediate management of DKA is intravenous 0.9% sodium chloride first, with the fixed rate intravenous insulin infusion commenced only after fluid therapy has been started, which is the order JBDS sets out.

If the systolic blood pressure is below 90 mmHg, JBDS gives 500 ml of 0.9% sodium chloride over 10 to 15 minutes, repeated if the pressure remains below 90 while senior input is sought. Most people need between 500 and 1000 ml given rapidly.

Above a systolic of 90 mmHg, JBDS prints an illustrative regimen for a previously well 70 kg adult: one litre over the first hour, then one litre over each of the next two-hour, two-hour, four-hour, four-hour and six-hour blocks.

The guideline asks for caution in young people aged 18 to 25 years, older people, pregnancy, heart or kidney failure, and other serious comorbidities, where fluids should be replaced more cautiously.

How do I prescribe insulin and potassium in DKA?

In DKA, JBDS prescribes a fixed rate intravenous insulin infusion at 0.1 units per kilogram per hour, made up as 50 units of human soluble insulin in 50 ml of 0.9% sodium chloride and given by pump.

JBDS also asks you to continue the patient's usual long-acting basal insulin at the usual dose and the usual time, which is the point candidates most often miss and panels most often probe.

For potassium, JBDS gives none when the level is over 5.5 mmol/L, 40 mmol per litre of infusion solution when it is 3.5 to 5.5 mmol/L, and asks for senior review when it is below 3.5 mmol/L because more is needed.

Say why. In DKA total body potassium is depleted even when the serum level is high, and insulin drives potassium into cells, so the level falls precipitously once treatment starts.

Which investigations do I order in a surgical patient with DKA?

In a surgical patient with DKA, JBDS asks for blood ketones, capillary and venous glucose, urea and electrolytes, venous blood gases, a full blood count, blood cultures, an electrocardiogram, urinalysis and culture, and a chest radiograph if clinically indicated.

Monitoring is then the investigation. JBDS asks for hourly glucose and hourly ketones, with venous blood gas for pH, bicarbonate and potassium at 60 minutes, at 2 hours and 2-hourly thereafter.

On top of that, add the surgical work-up. A patient with DKA and abdominal pain that does not settle as the acidosis corrects needs imaging, because the ketoacidosis is not the whole story.

How do I know DKA is resolving?

DKA is resolving when the ketones are falling by at least 0.5 mmol/L per hour, or the bicarbonate is rising by at least 3.0 mmol/L per hour, or the glucose is falling by at least 3.0 mmol/L per hour.

If those targets are not met, JBDS asks a prescribing clinician to increase the insulin infusion rate in 1.0 unit per hour increments hourly until the ketones are falling at target, and to check that the pump is working and connected.

The fixed rate infusion continues until the ketone measurement is less than 0.6 mmol/L and the venous pH is over 7.3 and/or the venous bicarbonate is over 18 mmol/L. JBDS expects resolution by 24 hours in most people.

When the glucose falls below 14.0 mmol/L, JBDS starts 10% glucose at 125 ml per hour alongside the sodium chloride, and asks you to consider reducing the insulin infusion rate to 0.05 units/kg/hr.

What is different about DKA on a surgical ward?

What is different about DKA on a surgical ward is that the trigger is often surgical, and the JBDS guideline says so directly: it may be necessary to consider a surgical cause for the deterioration.

JBDS then adds the sentence that decides the station. If surgery is required, there will need to be an urgent senior multidisciplinary discussion on the optimum time to operate.

That is the balance to articulate. Operating on an uncorrected ketoacidosis is dangerous, and so is delaying source control in a patient whose ketoacidosis will not correct until the source is controlled.

Practical surgical points follow. Keep the patient nil by mouth only if there is a surgical reason, give prophylactic low molecular weight heparin in line with NICE guidance as JBDS asks, and aim for a urine output no less than 0.5 ml/kg/hr.

Who do I escalate DKA in a surgical patient to, and when?

Escalate DKA in a surgical patient to the diabetes specialist team, which JBDS asks to be involved as soon as possible and ideally within 24 hours, and to critical care if any severity criterion is met.

Escalate to your surgical registrar in parallel, because the decision about whether and when to operate is a consultant-level conversation that JBDS explicitly frames as multidisciplinary.

Escalate immediately for a drowsy patient, a falling Glasgow Coma Scale score, a systolic blood pressure that does not respond to fluid, or a potassium that remains abnormal after a further hour of replacement.

What is the interviewer listening for in a DKA scenario?

The interviewer in a DKA scenario is listening for fluids before insulin, the fixed rate quoted correctly, potassium handled safely, and a candidate who never stops looking for the surgical cause.

The three diagnostic criteria named together, including the ketone and bicarbonate or pH thresholds
0.9% sodium chloride started first, then the fixed rate insulin infusion at 0.1 units/kg/hr
The usual long-acting basal insulin continued at the usual dose and time
Hourly ketones and glucose, with the resolution targets stated as rates rather than end points
An explicit statement that the timing of any operation is a senior multidisciplinary decision

What are the common mistakes in a DKA answer?

The commonest mistake in a DKA answer is giving insulin before fluid, which reverses the JBDS order and risks a sudden fall in potassium in a patient who is already depleted.

The second is stopping the long-acting insulin. JBDS asks for it to continue at the usual dose and time, and stopping it is a common cause of rebound ketosis when the infusion comes off.

The third is relying on urinary ketones. JBDS says not to use urinary ketone clearance to judge resolution of DKA, because urinary ketones are still present after the ketoacidosis has resolved.

How this comes up at the CST interview

DKA in the surgical patient usually arrives as a referral: a young person with type 1 diabetes, abdominal pain and vomiting, with the panel asking whether this is an acute abdomen or ketoacidosis.

The panel then pushes on the timing of surgery, on the potassium, or on what you would do if the abdominal pain persisted after the acidosis corrected.

The coresurgeryinterview question bank carries scored versions of this scenario among its 299 questions, with AI-marked spoken practice so the numbers can be rehearsed out loud: /Question-Bank/Sample-Questions.

DKA in the Surgical Patient