Diabetic ketoacidosis in pregnancy — structured oral station (12 minutes)

Opening prompt — "She has just arrived in birth suite. What do you do?"

Model response — say it as two patients, one team: [1][2]

• "This is diabetic ketoacidosis until proven otherwise. A woman with type 1 diabetes who has stopped insulin because she was not eating, with 36 hours of vomiting, Kussmaul breathing and drowsiness, has ketoacidosis regardless of what the glucose says."
• "I would call for help immediately: obstetric consultant, medical registrar or endocrinologist, anaesthetics, and alert the neonatal team given 27 weeks. I want a high-dependency or birth-suite bed with one-to-one nursing."
• "Simultaneously: airway, breathing, circulation, two large-bore cannulae, bloods, left lateral tilt, oxygen if hypoxaemic, and continuous CTG because she is viable."
• "Bedside tests now: capillary glucose and capillary beta-hydroxybutyrate, and a venous gas. I do not wait for the laboratory."[1]

Examiner is listening for: the diagnosis named in the first sentence, ketones measured at the bedside, help called by name, and simultaneous rather than sequential action. [1]

Probe 1 — "Her beta-hydroxybutyrate is 5.8, venous pH 7.08, bicarbonate 8, potassium 3.1, sodium 131, creatinine 96. Interpret that."

• "This is severe diabetic ketoacidosis. The 2024 consensus grades severity on the acidosis: pH below 7.0 or bicarbonate below 10 is severe, and she is at pH 7.08 with a bicarbonate of 8. Beta-hydroxybutyrate above 6.0 is the severe band and she is close to it."[1]
• "All three diagnostic criteria are met: known diabetes, beta-hydroxybutyrate 3.0 or more, and pH below 7.30."[1]
• "The critical number is the potassium of 3.1. That is below 3.5, so I hold insulin and replace potassium first."[1]
• "Her bicarbonate of 8 is even worse than it looks, because maternal bicarbonate is physiologically low in pregnancy at about 18 to 22 — she has almost no buffering reserve left."[6]
• "This is an intensive care level of illness. I would be speaking to ICU now, not later."[1]

Probe 2 — "Give me your actual orders. Rates, please."

This is where marks are made or lost. Say numbers. [1]

• Fluid: "Isotonic saline or a balanced crystalloid at 500 to 1000 mL/h for the first 2 to 4 hours, then the remaining deficit over 24 to 48 hours. I reassess after each litre, because the consensus specifically flags pregnancy as a state where rapid fluid replacement risks overload."[1]
• Potassium first: "Potassium 3.1, so I withhold insulin and give potassium at 10 mmol/h until it is above 3.5. Once it is between 3.5 and 5.0, I add 20 to 30 mmol per litre of fluid, aiming for 4 to 5 mmol/L. I recheck at 2 hours and then 4-hourly."[1]
• Insulin: "As soon as the potassium is above 3.5, a fixed-rate intravenous infusion of short-acting insulin at 0.1 units/kg/h. No bolus needed if I have access. I also continue her usual long-acting basal insulin subcutaneously — stopping it is why ketones rebound."[1]
• Dextrose: "Once glucose falls below 13.9 mmol/L I add 5 to 10 percent dextrose and reduce the insulin to 0.05 units/kg/h, then keep the glucose around 11 mmol/L until the ketosis clears. Her glucose is already 12.8, so realistically dextrose goes up almost immediately."[1][3]
• No bicarbonate unless the pH is below 7.0 — and at 7.08 she is close, so I would discuss it with intensive care rather than reflexively give it.[1]
• Monitoring: "Glucose hourly, beta-hydroxybutyrate every 1 to 2 hours, potassium at 2 hours then 4-hourly, and a strict fluid balance chart with a scribe."[1]

Probe 3 — "Twenty minutes in, the CTG shows a baseline of 175 with absent variability and late decelerations. Theatre is free."

The discriminating probe. Do not blink. [2]

• "I would not deliver her now. The trace reflects her metabolic state: maternal ketones and hydrogen ions cross the placenta, hypovolaemia and acidosis reduce uteroplacental perfusion, and maternal acidaemia impairs fetal oxygen delivery. Correcting her is the fetal resuscitation."[2][6]
• "She is also, right now, the worst possible anaesthetic candidate: pH 7.08, potassium 3.1, volume-depleted, drowsy. Operating converts one critically ill patient into two."[6]
• "At 27+2 weeks I would give the corticosteroid course if not already given — while planning for the glycaemic consequences — and involve neonatology, but that is preparation, not a decision to deliver."[1]
• "I would deliver if: the trace fails to recover after several hours of adequate maternal correction; there is a separate obstetric indication such as abruption or chorioamnionitis; or she deteriorates despite maximal therapy. I would make that call with my consultant and document the reasoning."[2]
• "And I would say this out loud to the team, because in a real resuscitation the pressure to go to theatre comes from everyone in the room."[2]

Probe 4 — "What caused this?"

• "Insulin omission during illness — she stopped because she was not eating, which is the single commonest avoidable precipitant and the reason sick-day rules exist."[8]
• "Vomiting, which in the UK national cohort accounted for 21 percent of episodes, alongside infection at 21 percent, steroids at 13 percent and medication errors at 10 percent."[4]
• "I would look hard for infection: urine culture, blood cultures, examination for chorioamnionitis, and a lactate. Sepsis is both a differential and a precipitant."[4][6]
• "And I would review whether she is on a pump — a cannula failure gives no basal depot and produces ketosis within hours."[1]

Probe 5 — "How worried should you be about the baby?"

• "Very. In the UK national cohort perinatal mortality was 16 percent — 11 stillbirths and one neonatal death among 73. In a Mayo Clinic cohort fetal demise occurred in 17.2 percent of pregnancies."[4][5]
• "The systematic review of outcomes after ketoacidosis reported stillbirth in 7 to 35 percent across studies, preterm birth in 25 to 83 percent and neonatal intensive care admission in 40 to 65 percent — and it also found only seven usable studies, so the evidence base is thin."[7]
• "That is exactly why the answer is aggressive maternal correction rather than a rushed delivery: the modifiable variable is her biochemistry."[2]

Probe 6 — communication: "Her partner is in the corridor and very frightened. Speak to him."

Rapport, respect and communication are three of the eight scored domains. [2]

• Take him somewhere quiet, sit down, and use plain words: "She is very unwell. Her diabetes has caused acid to build up in her blood because she stopped her insulin while she was vomiting. That is treatable, and we have started treatment."
• Be honest about the baby without foreclosing: "The baby's heart rate pattern is abnormal at the moment, and we expect that to improve as she gets better. We are watching continuously. If it does not improve, we may need to deliver early — and the neonatal team is already aware."
• Say what you need from him: "Has she been unwell in any other way? Has she had any fevers, any pain passing urine?" Family often hold the precipitant.
• Commit to updating him at a stated interval, and name who will do it.[2]

Probe 7 — "She recovers over 18 hours. What happens before she goes home?"

• "Transition off the infusion properly: overlap subcutaneous basal insulin by 1 to 2 hours before stopping the intravenous insulin, and stop it on resolved ketosis — beta-hydroxybutyrate below 0.6 with pH 7.3 or bicarbonate 18 or more — not on a normal glucose."[1]
• "Written sick-day rules: never stop basal insulin, test ketones when unwell, increase insulin rather than reduce it, keep fluids and carbohydrate going, present early. A ketone meter and strips, and a number that reaches a person."[8]
• "Reassess her whole regimen with the diabetes team rather than restarting it unchanged, and document the precipitant."[1]
• "Ongoing fetal surveillance, because a pregnancy that has had ketoacidosis stays high risk."[7]
• "And address the context. Fifteen percent of women in the UK cohort had a second episode in the same pregnancy, and the study linked ketoacidosis to deprivation and mental health difficulty — so social work and psychological support are part of the discharge plan, not an optional extra."[4]