Presenting Complaint:

• Confusion

Symptoms:

• Onset: Gradual over 3 days, worsening – “I’ve been feeling more confused over the last few days”
• Character: Persistent confusion with headache and marked thirst – “My head feels heavy, and I can’t think straight”
• Associated symptoms: Polyuria, polydipsia, dry mouth, lethargy, reduced oral intake – “I’ve been drinking a lot but still feel dry and tired”
• Exacerbating/alleviating factors: Worsening with no clear relieving factors – “Nothing is helping, and it keeps getting worse”
• Severity: Severe – “It’s affecting my ability to function”

Systemic Symptoms (answer only if specifically asked for):

• Urinary: Increased volume and frequency, no obvious blood
• Bowels: Bowel movements today, no constipation or diarrhoea, normal coloured stools noted previously, no PR bleeding noticed
• Respiratory: No cough, sputum production, shortness of breath, or pleuritic chest pain
• Cardiovascular:  No chest pain, palpitations, dizziness, or syncope 
• Head: Headache, confusion, no seizures or focal neurology changes noted
• Eyes: Intermittent blurred vision, no scleral icterus
• Weight: No recent weight loss, reduced appetite
• Fatigue: Fatigued, worsening mood
• Fever: No fever
• Vomiting and nausea: No vomiting episodes or nausea
• Hydration: Reports dry mouth

Past Medical History:

• Type 2 diabetes mellitus
• Hyperlipidaemia

Past Surgical History:

• None

Drug History:

• Metformin
• Statin

Allergies:

• NKDA

Family History:

• Father had type 2 diabetes

Social History:

• BMI: 27
• Smoker: None
• Alcohol: drinks on average 5-6 pints of beer daily
• Occupation: office worker
• Diet: poor dietary control
• Lives with wife and three children

Ideas, Concerns, and Expectations:

• Concerned something is wrong with his brain
• Worried his diabetes is “out of control”
• Wants to know why he feels confused and dehydrated

A-E Examination

Airway:

• Airway patent
• No signs of airway obstruction 

Breathing:

• Respiratory rate: 18 breaths/min
• Oxygen saturations: 98% on room air
• Speaking full sentences, no increased work of breathing
• Chest expansion equal bilaterally
• Clear breath sounds on auscultation
• No Kussmaul breathing 

Circulation:

• Pulse: 104 bpm (tachycardic), regular
• Blood pressure: 96/60 mmHg (hypotensive)
• Capillary refill time > 3 seconds
• Peripheries cool
• Dry mucous membranes
• Reduced skin turgor (dehydration)
• JVP not raised
• Heart sounds normal, no murmurs
• No peripheral oedema

Disability:

• GCS: 14/15 (E4 V4 M6 – confused)
• AVPU: Alert but confused
• Pupils equal and reactive to light
• Blood glucose: 38 mmol/L
• Orientation: Not fully oriented to time or place, oriented to person only
• No focal neurological deficits 

Exposure:

• Temperature: 36.7°C
• No rash, cellulitis, or obvious source of infection
• Abdomen soft, non-tender
• No signs of trauma
• Overall: markedly dehydrated 

Observations:

• Respiratory rate: 18
• Oxygen sats: 98% RA
• Pulse: 104
• Blood pressure: 96/60
• Temperature: 36.7

NEWS: 3

Laboratory tests:

• Blood glucose 38 mmol/L (Normal fasting blood glucose range: 3.9-5.5 mmol/L)
• VBG/ABG pH 7.38 (Normal pH range: 7.35-7.45)
• Lactate 1.5 mmol/L (Normal lactate range: 0.5-2.2 mmol/L)
• Bicarbonate 23 mmol/L (Normal bicarbonate range: 22-26 mmol/L)
• Serum ketones 0.8 mmol/L (Normal serum ketones range: <0.6 mmol/L)
• Na 152 mmol/L (Normal Na range: 135-145 mmol/L)
• K 4.8 mmol/L (Normal K range: 3.5-5.0 mmol/L)
• Urea 12.4 mmol/L (Normal urea range: 2.5-7.8 mmol/L)
• Creatinine 145 µmol/L (Normal creatinine range: 64-104 µmol/L)
• Serum osmolality 354 mOsm/kg (Normal serum osmolality: 275-295 mOsm/kg)
• WCC 14.5 ×10⁹/L (Normal WCC range: 4.0–11.0 ×10⁹/L)
• CRP (C-reactive protein): 12 mg/L (Normal CRP range: <5 mg/L)

Examiner questions

1. What is your main differential diagnosis and why is this more likely than other differentials?

Answer: Hyperosmolar Hyperglycaemic State (HHS) 

• Marked hyperglycaemia with significantly raised serum osmolality, normal pH, normal bicarbonate, and only mildly elevated ketones is suggestive of HHS. The presence of severe dehydration, confusion, and a background of poorly controlled type 2 diabetes further supports this diagnosis. In HHS, relative insulin deficiency prevents ketosis but is insufficient to control blood glucose, leading to profound hyperosmolar dehydration without significant acidosis.
• Diabetic ketoacidosis (DKA) is a key differential to consider; however, DKA would typically present with metabolic acidosis, low bicarbonate, and markedly elevated ketones.
• While hypoglycaemia is a key differential for confusion in diabetics, the blood glucose level here is markedly elevated.
• Stroke or intracranial pathology is a key differential for confusion in the elderly, but the profound hyperglycaemia, hyperosmolar state and normal neurological exam provide a likely metabolic cause for the altered mental status. Stroke is also a recognised complication of HHS, thus would need to be ruled out as a concurrent pathology.

2. Describe the management of this condition

Possible answer:

• Initial A-E assessment, full set of bloods and VBG/ABG including glucose, ketones, U&Es, osmolality, FBC, CRP.
• IV fluid resuscitation with 0.9% sodium chloride according to local protocols, and correct any electrolyte abnormalities. Use caution in the correction of chronic hypernatraemia due to the risk of cerebral oedema. Carefully monitor serum osmolality, sodium and potassium.
• After initiating fluid resuscitation, commence insulin infusion in accordance with local protocol, typically when there is ketonaemia (ketones > 1). The fall in osmolality should not exceed 3.0-8.0 mOsm/kg/hr to minimise the risk of neurological complications. The fall in glucose should not be more than 5.0 mmol/L/hr.
• Identify and treat precipitating causes (e.g. infection, non-compliance with medication).
• Suspend metformin + statin in acutely unwell state.
• Strict fluid balance monitoring, catheterise.
• Thromboprophylaxis due to high thrombotic risk.
• Close monitoring in HDU/ICU if severe.
• Consider specialist input from diabetes team, critical care outreach team.
• Consider CT head to rule out cerebrovascular causes of acute confusion.

3. How would you distinguish HHS from diabetic ketoacidosis (DKA)?

Possible answer:

• HHS develops more insidiously and is dominated by hyperosmolar dehydration rather than ketoacidosis.

4. Name complications of untreated HHS 

Possible answer:

• Acute kidney injury
• Thromboembolism
• Seizures
• Coma
• Death
• MI/stroke
• Cerebral oedema
• Central pontine myelinolysis
• Iatrogenic complications from high-dose insulin e.g. hypoglycaemia, hypokalaemia