Step 3 CCS: Diabetic Ketoacidosis
DKA is a CCS classic that tests meticulous fluid and electrolyte management over simulated hours. You must run simultaneous insulin and potassium protocols, track the anion gap, and identify the precipitating cause. The most common CCS errors are starting insulin with potassium <3.5, stopping insulin before the anion gap closes, and neglecting to search for infection as the trigger.
Clinical Approach — What Attendings Do First
The First Minute
- Normal saline 1 L/hr IV bolus (15-20 mL/kg in first hour)
- BMP (potassium is critical), CBC, serum ketones (beta-hydroxybutyrate), VBG or ABG
- Fingerstick glucose q1h, BMP q2h to track potassium and anion gap
- Continuous telemetry (hypo/hyperkalemia causes arrhythmias)
- Urinalysis + urine culture, blood cultures x2, chest X-ray (find the precipitant)
Key Orders
- Regular insulin 0.1 units/kg IV bolus → 0.1 units/kg/hr continuous infusion (AFTER confirming K+ ≥3.5)
- KCl 20-40 mEq in each liter of IV fluids (adjust per K+ level q2h)
- Switch to D5 0.45% NaCl when glucose <250 mg/dL — do NOT stop insulin
- Phosphate replacement if <1.0 mg/dL (potassium phosphate, replacing some KCl)
- Serum beta-hydroxybutyrate (more reliable than urine ketones)
- HbA1c (distinguishes new-onset diabetes vs non-compliance)
- Lipase if abdominal pain (DKA can cause pseudopancreatitis or mask true pancreatitis)
Time-Sensitive Actions
- Do NOT start insulin if K+ <3.5 — replace potassium first (insulin will drive K+ lower → cardiac arrest)
- Check BMP every 2 hours to track anion gap closure — this determines when to stop the drip
- When glucose drops to 250: add dextrose to fluids and reduce insulin rate, but keep drip running
- Advance clock in 2-hour increments, re-ordering BMP each time to show active management
Common CCS Pitfalls
- Starting insulin with K+ <3.5 — this is the #1 DKA CCS error and can cause fatal arrhythmia
- Stopping insulin drip when glucose normalizes but anion gap is still open
- Forgetting to search for precipitant (infection causes 40% of DKA episodes)
- Not adding dextrose to fluids when glucose <250 — causes hypoglycemia
- Stopping the case too early — CCS expects you to transition to subcutaneous insulin and address underlying cause
Frequently Asked Questions
What is the correct order of interventions for DKA on CCS?
Step 1: Aggressive IV fluids — normal saline 1-1.5 L/hr for the first 1-2 hours. Step 2: Check potassium — if K+ <3.5, replace potassium FIRST before starting insulin. Step 3: Regular insulin 0.1 units/kg IV bolus, then 0.1 units/kg/hr drip. Step 4: When glucose <250, switch fluids to D5 half-normal saline and reduce insulin to 0.02-0.05 units/kg/hr. Step 5: Continue insulin drip until anion gap closes, NOT until glucose normalizes.
How do I manage potassium during a CCS DKA case?
Check BMP immediately. If K+ <3.3: hold insulin, give 20-40 mEq/hr KCl IV until K+ >3.5. If K+ 3.3-5.3: add 20-40 mEq KCl to each liter of IV fluids. If K+ >5.3: do not supplement, but recheck in 2 hours. As insulin drives K+ intracellularly, levels will drop — recheck BMP every 2 hours until stable. This is the #1 DKA CCS scoring point.
When can I transition from insulin drip to subcutaneous insulin on CCS?
Transition when ALL criteria met: anion gap closed (<12), serum bicarbonate ≥15, venous pH >7.30, patient tolerating oral intake. Give subcutaneous insulin (long-acting + rapid-acting) at least 2 hours before stopping the drip to prevent rebound hyperglycemia and ketosis. Calculate the SC dose based on total daily insulin drip requirement.
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