Background Information

Definition

HHS is an acute, life-threatening complication of diabetes mellitus, characterised by:

• Severe hyperglycemia
• Increased plasma osmolality
• Profound dehydration,
• Absent or minimal ketosis or acidosis

See below for its diagnostic criteria.

Pathophysiology

The pathophysiology of HHS is similar to that of DKA, insulin deficiency ^[Ref]

• But the main consequence is extreme dehydration (from osmotic diuresis) and increased plasma osmolality
• This is because insulin deficiency in HHS is NOT absolute, therefore the residual insulin is still able to counteract lipolysis and thus ketogenesis

Aetiology

Primarily affects those with T2DM. ^[Ref]

Precipitators of HHS: ^[Ref]

• Insulin deficiency
  • New-onset T1DM (1/3 of children and adolescents present initially as DKA)
  • Insulin omission / non-adherence

• ↑ Insulin demand (→ relative deficiency)
  • Infection (esp. UTI and pneumonia)
  • Trauma
  • Surgery
  • Systemic steroids

Complications

Complications of HHS are related to the significant dehydration:

• Hypovolaemia and/or shock
• Electrolyte disturbances (hypokalaemia, hypernatraemia)
• AKI
• Altered mental status
• Seizures
• Thromboembolic events (due to hyperviscosity)

Diagnosis

Clinical Features

HHS typically occurs in the context of T2DM. ^[Ref]

HHS typically presents subtly with the following findings: ^[Ref]

• Gradual onset (>24 hours)
• Dehydration ++++ (e.g. dry mucous membrane, reduced skin turgor, tachycardia)
• Polyuria, polydipsia (from hyperglycaemia)
• Nausea and vomiting – tend to be less prominent (+++ in DKA)
• Altered mental status
• Fatigue / generalised weakness

Be aware that the following findings are specific to DKA (not seen in HHS): ^[Ref]

• Rapid onset (<24 hours)
• Abdominal pain (this occurs due to ketoacidosis irritating the peritoneum, thus it is absent in HHS)
• “Pearl-drop” / fruity breath odour (from exhaled ketones)
• Kussmaul respiration (compensatory hyperventilation in response to metabolic acidosis)

Diagnostic Criteria

JBDS states that no precise definition has been agreed upon, but outlined the following characteristic features (ALL must be present):

• Hypovolaemia (marked)
• Osmolality ≥320 mOsm/kg
• Hypergylcaemia (glucose ≥30 mmol/L)
• NO significant ketonaemia (≤3.0 mmol/L) (a mild ketosis is possible due to starvation)
• NO significant acidosis (pH ≥7.3 or serum bicarbonate ≥15 mmol/L) (a mild metabolic acidosis is possible due to dehydration → ↑ lactate, and renal impairment)

Management

Initial Management

Initial fluid regimen: IV 0.9% NaCl, 1L over 1 hour

Other considerations:

• Maintain potassium in normal ranges (depending on serum potassium concentrations)
  • >5.5 mmol/L → no potassium replacement needed
  • 3.5-5.5 mmol/L → give 40 mmol/L potassium in infusion solution
  • <3.5 mmol/L → seek senior review (as additional potassium is required)

• Prevent hypoglycaemia
  • If blood glucose falls <14 mmol/L → add 5% or 10% glucose at 125 mL/hr in addition to the running fluids

Insulin Therapy

Insulin should NOT be started as part of the initial treatment, it should only be started once fluid replacement is adequate and serum glucose has plateaued

• Commence FRIII at 0.05 units/kg/hr
• Only increase to 0.1 units/kg/hr if glucose concentration is not falling

Anticoagulation

All HHS patients should receive prophylactic LMWH for the full duration of admission unless contraindicated.

Monitoring

The main parameter to monitor is serum osmolality [(2 x Na⁺) + glucose + urea]

References