DKA, HHS & hypoglycaemia — MRCP Part 1 flashcards

Question 1

What are the JBDS diagnostic criteria for diabetic ketoacidosis?

Accepted Answer

Ketones ≥3 mmol/L (or urine ≥2+); glucose >11 mmol/L or known diabetes; pH <7.3 and/or bicarbonate <15 mmol/L. — All three parts — ketonaemia, hyperglycaemia/diabetes and acidosis — are needed.

Question 2

What IV fluid is given in the first hour of DKA management in a normotensive adult?

Accepted Answer

0.9% sodium chloride, 1 litre over 1 hour. — Restoring circulating volume is the first priority. Later bags run over 2, 2, 4, 4 and 6 hours.

Question 3

What insulin infusion is used in DKA, and at what rate?

Accepted Answer

Fixed-rate IV infusion of soluble human insulin at 0.1 units/kg/hour. — A fixed rate clears ketones regardless of glucose. Estimate weight if needed.

Question 4

What should happen to a patient's usual long-acting insulin during DKA treatment?

Accepted Answer

Continue it at the usual dose and time. — This prevents rebound ketosis when the IV insulin is stopped.

Question 5

In DKA, how much potassium is added to each litre of fluid if serum K⁺ is 3.5–5.5 mmol/L?

Accepted Answer

40 mmol KCl per litre. — Insulin drives potassium into cells, so levels fall during treatment. Give no KCl if K⁺ >5.5; seek senior advice if <3.5.

Question 6

In DKA, when is 10% glucose added, and at what rate?

Accepted Answer

When blood glucose falls below 14 mmol/L — 10% glucose at 125 mL/hour alongside the saline. — This lets the fixed-rate insulin keep clearing ketones without causing hypoglycaemia. JBDS (2023) also suggests considering reducing the insulin to 0.05 units/kg/hour at this point.

Question 7

What hourly fall in blood ketones is the target in DKA, and what is done if it is not reached?

Accepted Answer

Fall of ≥0.5 mmol/L/hour; if not, increase the insulin infusion by 1 unit/hour. — Alternative targets: bicarbonate rising ≥3 mmol/L/hour or glucose falling ≥3 mmol/L/hour.

Question 8

What criteria define resolution of DKA?

Accepted Answer

Blood ketones <0.6 mmol/L and venous pH >7.3. — Bicarbonate is not used to judge resolution. Switch to subcutaneous insulin once DKA has resolved and the patient is eating and clinically stable.

Question 9

What are the key biochemical features of hyperosmolar hyperglycaemic state (HHS)?

Accepted Answer

Glucose >30 mmol/L, serum osmolality >320 mOsm/kg and no significant ketonaemia or acidosis. — Residual insulin suppresses ketogenesis but cannot control the glucose. It typically affects older people with type 2 diabetes.

Question 10

How is serum osmolality calculated in HHS?

Accepted Answer

2 × Na⁺ + glucose + urea (all in mmol/L). — Serial calculated osmolality guides the rate of correction.

Question 11

What is the first-line treatment of HHS?

Accepted Answer

IV 0.9% sodium chloride alone (even if hypernatraemic). — Fluids alone lower glucose and osmolality. Use 0.45% saline only if osmolality is not falling despite adequate fluid. Give prophylactic LMWH because of high VTE risk.

Question 12

In HHS, when is IV insulin started, and at what rate?

Accepted Answer

Only when glucose stops falling with fluids alone (or if significant ketonaemia), at 0.05 units/kg/hour. — Early insulin drops glucose and osmolality too fast, shifting water into cells and risking cerebral oedema and circulatory collapse.

Question 13

In HHS, what is the target rate of fall of serum osmolality?

Accepted Answer

3–8 mOsm/kg per hour. — Glucose should fall by no more than 5 mmol/L/hour and sodium by no more than 10 mmol/L in 24 hours.

Question 14

How is hypoglycaemia (<4 mmol/L) treated in a conscious adult who can swallow?

Accepted Answer

Fast-acting oral carbohydrate; recheck after about 15 minutes and repeat up to 3 times. — Follow with a longer-acting carbohydrate once glucose recovers. If still not responding, give IM glucagon or IV 10% glucose.

Question 15

For an unconscious hypoglycaemic patient, why should 50% glucose be avoided?

Accepted Answer

Risk of extravasation injury (it is highly irritant). — Use IM glucagon, or IV 10% or 20% glucose instead.

Question 16

In which situations is IM glucagon ineffective for hypoglycaemia?

Accepted Answer

When liver glycogen is depleted — prolonged fasting, chronic hypoglycaemia or alcohol-induced hypoglycaemia. — Glucagon works by releasing glucose from hepatic glycogen; with no glycogen, give IV glucose.

Question 17

What is the FIRST physiological defence against falling blood glucose?

Accepted Answer

Reduced insulin secretion. — Then glucagon rises, then adrenaline; growth hormone and cortisol respond later.

Question 18

How does alcohol cause hypoglycaemia?

Accepted Answer

Alcohol metabolism raises NADH, which inhibits hepatic gluconeogenesis. — Risk is highest after fasting or binge drinking, when glycogen stores are already low.

Question 19

What is Whipple's triad?

Accepted Answer

Symptoms of hypoglycaemia, a documented low plasma glucose, and relief of symptoms when glucose is given. — It must be shown before investigating for an insulinoma, the commonest pancreatic islet-cell tumour (about 90% benign).

Question 20

What is the gold-standard diagnostic test for insulinoma?

Accepted Answer

Supervised 72-hour fast. — It shows hypoglycaemia with inappropriately high insulin, C-peptide and proinsulin.

Question 21

A nurse has hypoglycaemia with high insulin but LOW C-peptide. What is the cause?

Accepted Answer

Exogenous (injected) insulin. — Pharmaceutical insulin contains no C-peptide and suppresses the patient's own. Insulinoma and sulfonylureas both give high insulin AND high C-peptide; a sulfonylurea screen separates them.

Question 22

Which oral drug is used to control hypoglycaemia from an insulinoma that cannot be resected?

Accepted Answer

Diazoxide. — It opens beta-cell K-ATP channels and inhibits insulin release. Somatostatin analogues are an alternative; surgery is definitive.

DKA, HHS & hypoglycaemia flashcards

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