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IM11.1-24 | Diabetes Mellitus — PBL Case

CLINICAL SETTING

It is 11:30 PM at the casualty department of a government teaching hospital in Chennai. Final-year MBBS students Arun and Priya are on their night duty posting. The duty resident, Dr Kavitha, is simultaneously managing three patients. A family rushes in with Rajan, a 52-year-old taxi driver. His wife explains: 'He has been very tired for three months, urinating very frequently at night, and drinking a lot of water. Tonight he started vomiting after dinner, complained of severe stomach pain, and his breathing has become very fast and deep.' She produces no previous medical records. Rajan is drowsy but responds to voice. His wife adds: 'He has never been diagnosed with any disease. He eats a lot of biryani and drinks a small amount of alcohol on weekends. His father died of a heart attack at 57 — we don't know why.' Arun quickly checks the triage vitals: BP 96/64 mmHg, pulse 118/min (thready), RR 28/min (deep and sighing), temperature 37.8°C, SpO2 98% on air. Capillary blood glucose reads 'HI' (above the glucometer's measurable range of 600 mg/dL). Arun looks at Priya and says: 'I think I know what this is. But what exactly is happening, and where do we start?'

Trigger 1: First Encounter: Unravelling the Presentation

Dr Kavitha reviews Rajan rapidly. She notes the deep sighing breaths — 'Kussmaul breathing,' she says — and the smell of acetone on his breath. She orders immediate blood investigations. Results arrive in 20 minutes: Blood glucose: 624 mg/dL. Arterial blood gas: pH 7.14, PaCO2 22 mmHg, HCO3 8 mEq/L, anion gap 28 mEq/L. Serum potassium: 5.8 mEq/L. Serum sodium: 128 mEq/L (corrected Na 138 mEq/L). Urine dipstick: glucose 4+, ketones 3+. Creatinine: 1.8 mg/dL (baseline unknown). Dr Kavitha turns to Arun: 'Tell me the diagnosis, the specific criteria that confirm it, and the five parallel problems we must address simultaneously.' She also asks: 'His potassium is 5.8 on the blood test — does that mean he has too much potassium in his body?'

DISCUSSION POINTS

  • State the three-part diagnostic criteria for diabetic ketoacidosis (DKA) and identify which specific values in Rajan's investigations confirm each criterion.
  • Dr Kavitha asks whether the high serum potassium (5.8 mEq/L) represents true hyperkalaemia or a redistributional change. Explain the mechanism of potassium shift in DKA and the clinical implication for insulin therapy.
  • Name the five parallel derangements in DKA that must be addressed simultaneously and outline the first therapeutic action for each.
Click to reveal Trigger 2: The Management Hour: Decisions Under Pressure (discuss previous trigger first!)

Trigger 2: The Management Hour: Decisions Under Pressure

Dr Kavitha initiates the DKA protocol. IV access is secured and 1 litre of 0.9% normal saline is running rapidly. An insulin infusion is prepared. Arun asks: 'Should we start insulin now?' Dr Kavitha responds: 'Look at the potassium before you answer.' Arun rechecks: K+ is 5.8 mEq/L. As the team manages the resuscitation, Rajan's wife pulls Priya aside: 'Doctor, he was fine — he just had tiredness. Why is he so sick now? He also had a fever and burning while passing urine three days ago.' Priya notes this in the chart. Two hours into treatment, a repeat glucose shows 420 mg/dL. Potassium has fallen to 3.9 mEq/L. The nurse prepares to add potassium to the IV fluid. Dr Kavitha asks: 'At what glucose level do we change the IV fluid, and what do we change it to?'

DISCUSSION POINTS

  • At the time of initiating the DKA protocol, Rajan's K+ is 5.8 mEq/L. State the rule regarding insulin initiation in DKA at different potassium levels (below 3.5, 3.5-5.5, above 5.5 mEq/L) and justify this rule using the pathophysiology of potassium shift.
  • Rajan's wife mentions fever and dysuria 3 days before admission. How do you incorporate this history into the management plan? Name the most common precipitating causes of DKA and explain which investigation is now mandatory.
  • When Rajan's glucose reaches approximately 250-300 mg/dL during treatment, what specific change must be made to the IV fluid and why? What are the criteria for DKA resolution — and is glucose normalisation one of them?
Click to reveal Trigger 3: The Morning After: Making the Diabetes Diagnosis and Starting Long-Term Management (discuss previous trigger first!)

Trigger 3: The Morning After: Making the Diabetes Diagnosis and Starting Long-Term Management

By the next morning, Rajan is fully alert, eating, and his DKA has resolved. ABG: pH 7.38, HCO3 22 mEq/L. Blood glucose: 186 mg/dL. Dr Kavitha explains to the team: 'His DKA has resolved. Now we need to figure out what type of diabetes he has and what long-term treatment he needs.' A C-peptide level taken on admission is low-normal: 0.3 nmol/L (normal 0.37-1.47 nmol/L). GADA (glutamic acid decarboxylase antibodies) result is pending. Fasting lipid profile from the morning: total cholesterol 248 mg/dL, LDL 164 mg/dL, HDL 34 mg/dL, triglycerides 398 mg/dL. Creatinine has returned to 1.1 mg/dL (eGFR estimated at 64 mL/min/1.73 m2). Urine ACR: 42 mg/g. Dr Kavitha asks the students: 'What type of diabetes does he most likely have, what drugs can and cannot be used, and what are his non-glycaemic priorities?'

DISCUSSION POINTS

  • Based on the clinical picture (age 52, obesity risk factors implied by the diet history, low-normal C-peptide, DKA presentation, no known autoimmune history), discuss whether this patient is more likely to have ketosis-prone T2DM (KPD) versus early T1DM or LADA. What additional investigations would help classify him?
  • Rajan's eGFR is 64 mL/min/1.73 m2 and uACR is 42 mg/g (microalbuminuria). He has hypertriglyceridaemia (398 mg/dL) and low HDL. Construct a prioritised pharmacological plan covering: (a) glycaemic control — which oral agent is first-line and at what dose threshold must it be stopped; (b) renal protection — which drug class, and why is it more than just an antihypertensive; (c) lipid management — which drug class, and what is the LDL target for a high-risk diabetic patient.
  • Rajan is discharged on metformin and glargine insulin. His wife asks: 'Will he need insulin forever? Can tablets alone control him in the future?' How do you counsel her — and what does the natural history of beta-cell function in T2DM (or KPD) predict about future insulin requirements?
Click to reveal Trigger 4: One Year Later: Complications, Targets, and the Patient's Perspective (discuss previous trigger first!)

Trigger 4: One Year Later: Complications, Targets, and the Patient's Perspective

Rajan returns to the diabetes clinic 12 months later. He has lost 7 kg, stopped alcohol, and is eating a modified diet. He is on metformin 1000 mg twice daily, glargine 18 units at bedtime, enalapril 5 mg, atorvastatin 40 mg, and an SGLT2 inhibitor that was started 6 months ago. His HbA1c is now 7.8% (down from 12.1% at discharge). He brings his SMBG diary — fasting glucoses range 120-160 mg/dL and post-prandial readings are 180-240 mg/dL. He mentions: 'I am doing fine but I noticed some swelling and redness of my right great toe two weeks ago. It was painful for a few days but the pain has now gone away. I did not come earlier because the pain stopped.' On examination: the right great toe shows a small area of skin breakdown over the dorsum. His monofilament is absent at three sites on the right foot. Dorsalis pedis pulse is palpable but weak. Dr Kavitha says to the students: 'The fact that the pain has gone away is not reassuring — explain why, and what we must do now.'

DISCUSSION POINTS

  • Explain why the disappearance of pain from the diabetic foot lesion is a warning sign rather than a reassurance. What does this tell you about the stage of neuropathy and the risk to this foot?
  • Construct a systematic diabetic foot assessment for Rajan at this visit: what findings on examination of the neurovascular status, skin, and deformity would classify this foot according to the Wagner classification or the SINBAD score?
  • Rajan's post-prandial glucoses remain 180-240 mg/dL despite a fasting glucose approaching target. His physician is considering adding a short-acting prandial insulin. The patient says: 'I already inject once — I don't want to inject more times.' How do you balance patient preference (IM11.21) with the clinical need to address post-prandial hyperglycaemia? Name two alternatives to prandial insulin that address post-meal glucose in T2DM.

Group Task Assignments

  • Using Rajan's admission data, construct the complete five-parallel-action DKA management protocol: fluid resuscitation (volumes and rates by hour), insulin infusion (dose, switch point, resolution criteria), potassium replacement (rules by serum K+ level), precipitant identification and treatment, and monitoring schedule (frequency and parameters).
  • Draft a structured discharge education plan for Rajan that covers: SMBG technique and target ranges, recognition of early hypoglycaemia symptoms (autonomic vs neuroglycopenic), when to call a doctor urgently (glucose above 300 mg/dL with vomiting, ketones positive), insulin storage and travel, and foot self-examination daily checklist.
  • Debate: 'In India, SGLT2 inhibitors should be the second-line drug after metformin in all T2DM patients, not just those with established CVD or CKD.' Identify the clinical, economic, and system-level arguments for and against this proposition in a resource-limited Indian context.
  • Rajan asks: 'My father died of a heart attack at 57. Am I at risk?' Calculate his 10-year cardiovascular risk profile using available data and construct a personalised cardiovascular prevention plan — including blood pressure target, LDL target, antiplatelet therapy decision, and lifestyle modification goals.

Learning Issues

Research these questions and bring your findings to the discussion.

  1. [IM11.23] What are the precipitating causes, pathophysiology, three-part diagnostic criteria, and five-parallel management steps of diabetic ketoacidosis, including the rules for insulin initiation based on serum potassium?
  2. [IM11.24] How does hyperosmolar hyperglycaemic state (HHS) differ from DKA in pathophysiology, clinical presentation, typical patient profile, and management approach — specifically regarding fluid replacement rate and insulin timing?
  3. [IM11.17] What is the current stepwise T2DM treatment algorithm incorporating cardiovascular risk, renal risk, weight, and hypoglycaemia risk — and when are SGLT2 inhibitors and GLP-1 receptor agonists preferred over other classes?
  4. [IM11.18] What is the mechanism by which ACE inhibitors and ARBs reduce proteinuria and slow CKD progression in diabetic nephropathy, and what is the evidence basis for statin therapy and blood pressure targets in T2DM with cardiovascular risk?
  5. [IM11.11] What are the four diagnostic criteria for diabetes mellitus (with precise thresholds), when is confirmation on a separate day required, and when is HbA1c unreliable as a diagnostic test?
  6. [IM11.10] How is a differential diagnosis for a patient presenting with DKA constructed — what features differentiate ketosis-prone T2DM (KPD) from T1DM and LADA, and which investigations resolve the classification?