Hyperosmolar hyperglycaemic state

Question 1

What is hyperosmolar hyperglycaemic state (HHS)?

Answer 1

A life-threatening diabetic emergency characterised by severe hyperglycaemia, hyperosmolality, and profound dehydration without significant ketosis or acidosis

Question 2

Which type of diabetes is HHS most commonly associated with?

Answer 2

Type 2 diabetes mellitus

Question 3

In which patient group does HHS most commonly occur?

Answer 3

Elderly patients with type 2 diabetes

Question 4

What is the approximate mortality rate of HHS?

Answer 4

Up to 20%

Question 5

What is the core pathophysiological sequence in HHS?

Answer 5

Hyperglycaemia → increased serum osmolality → osmotic diuresis → severe volume depletion

Question 6

Why does severe dehydration occur in HHS?

Answer 6

Osmotic diuresis caused by extreme hyperglycaemia

Question 7

What factors commonly precipitate HHS?

Answer 7

Intercurrent illness, dementia, and sedative drugs

Question 8

How does the onset of HHS compare to DKA?

Answer 8

HHS develops over days, whereas DKA develops over hours

Question 9

Why is dehydration often more severe in HHS than DKA?

Answer 9

The slower onset allows prolonged fluid loss before presentation

Question 10

What are the key clinical signs of dehydration in HHS?

Answer 10

Dry mucous membranes, hypotension, tachycardia, reduced skin turgor

Question 11

What classic symptoms of osmotic diuresis are seen in HHS?

Answer 11

Polyuria and polydipsia

Question 12

What systemic symptoms are common in HHS?

Answer 12

Lethargy, nausea, and vomiting

Question 13

What neurological features may be seen in HHS?

Answer 13

Altered level of consciousness and focal neurological deficits

Question 14

Why are focal neurological signs seen in HHS?

Answer 14

Marked hyperosmolality affecting cerebral function

Question 15

What haematological consequence can occur due to hyperviscosity in HHS?

Answer 15

Myocardial infarction, stroke, or peripheral arterial thrombosis

Question 16

Is there a single strict diagnostic criterion for HHS?

Answer 16

No, diagnosis is based on a constellation of findings

Question 17

What level of blood glucose is typically seen in HHS?

Answer 17

Marked hyperglycaemia, usually >30 mmol/L

Question 18

What serum osmolality is typical of HHS?

Answer 18

Significantly raised, usually >320 mOsm/kg

Question 19

How is serum osmolality calculated?

Answer 19

2 × sodium + glucose + urea

Question 20

What ketone level is expected in HHS?

Answer 20

No significant hyperketonaemia, typically <3 mmol/L

Question 21

What acid–base status is typical in HHS?

Answer 21

No significant acidosis (pH >7.3, bicarbonate >15 mmol/L)

Question 22

Why might mild acidosis still occur in HHS?

Answer 22

Lactic acidosis or renal impairment

Question 23

What is the primary initial treatment in HHS?

Answer 23

Aggressive fluid replacement

Question 24

How large are estimated fluid losses in HHS?

Answer 24

Approximately 100–220 ml/kg

Question 25

Which intravenous fluid is first-line in HHS?

Answer 25

0.9% sodium chloride

Question 26

What is the typical initial rate of fluid replacement in HHS?

Answer 26

Approximately 0.5–1 litre per hour depending on clinical status

Question 27

Why must sodium levels be monitored closely during treatment?

Answer 27

Rapid correction increases the risk of cerebral oedema

Question 28

How should potassium be managed in HHS?

Answer 28

Monitored closely and added to fluids as required

Question 29

When should insulin be started in HHS?

Answer 29

Only if blood glucose stops falling with fluid replacement alone

Question 30

Why is insulin delayed initially in HHS?

Answer 30

Fluids alone often significantly reduce glucose and insulin can worsen electrolyte shifts

Question 31

Why is venous thromboembolism prophylaxis essential in HHS?

Answer 31

Patients are at high risk of thrombosis due to hyperviscosity

Question 32

What major complications can arise from hyperviscosity in HHS?

Answer 32

Myocardial infarction and stroke