hyper osmolar hypergylcaemic state Flashcards
What is HSS
medical emergency where Hyperglycaemia results in osmotic diuresis, severe dehydration, and electrolyte deficiencies.
Who is at risk
HHS typically presents in the elderly with type 2 diabetes mellitus (T2DM)
What is dangerous to give to HHS patients
It is extremely important to differentiate HHS from diabetic ketoacidosis (DKA) as the management is different, and treatment of HHS with insulin (e.g. as part of a DKA protocol) can result in adverse outcomes.
What are the possible complications of HHS
HHS has a higher mortality than DKA and may be complicated by vascular complications such as myocardial infarction, stroke or peripheral arterial thrombosis. Seizures, cerebral oedema and central pontine myelinolysis (CPM) are uncommon but documented complications of HHS.
What is the onset of HHS
HHS comes on over many days, and consequently the dehydration and metabolic disturbances are more extreme.
What is the pathophysiology §
Hyperglycaemia results in osmotic diuresis with associated loss of sodium and potassium
Severe volume depletion results in a significant raised serum osmolarity (typically > than 320 mosmol/kg), resulting in hyperviscosity of blood.
Despite these severe electrolyte losses and total body volume depletion, the typical patient with HHS, may not look as dehydrated as they are, because hypertonicity leads to preservation of intravascular volume.
What general features may you see
fatigue, lethargy, nausea and vomiting
What neurological features may you see
altered level of consciousness, headaches, papilloedema, weakness
What haematological features may you see
hyperviscosity (may result in myocardial infarctions, stroke and peripheral arterial thrombosis)
What cardiovascular features may you see
dehydration, hypotension, tachycardia
What are the diagnostic features
- Hypovolaemia
- Marked Hyperglycaemia (>30 mmol/L) without significant ketonaemia or acidosis
- Significantly raised serum osmolarity (> 320 mosmol/kg)
Note: A precise definition of HHS does not exist, however the above 3 criteria are helpful in distinguishing between HHS and DKA. It is also important to remember that a mixed HHS / DKA picture can occur.
What are the goals of management
- Normalise the osmolality (gradually)
the serum osmolality is the key parameter to monitor
if not available it can be estimated by 2 * Na+ + glucose + urea - Replace fluid and electrolyte losses
- Normalise blood glucose (gradually)
What are the estimated fluid losses
Fluid losses in HHS are estimated to be between 100 - 220 ml/kg (e.g. 10-22 litres in an individual weighing 100 kg).
How to determine rate of rehydration
assessing the combination of initial severity and any pre-existing co-morbidities (e.g. heart failure and chronic kidney disease). Caution is needed, particularly in the elderly, where too rapid rehydration may precipitate heart failure but insufficient may fail to reverse an acute kidney injury.
What is the first line IV replacement
Intravenous (IV) 0.9% sodium chloride solution is the first line fluid for restoring total body fluid.
What to do next if serum osmolarity is not declining despite positive balance with 0.9% sodium chloride
fluid should be switched to 0.45% sodium chloride solution which is more hypotonic relative to the HHS patients serum osmolarity
What is the aim for iv fluid replacement
aim to achieve a positive balance of 3-6 litres by 12 hours and the remaining replacement of estimated fluid losses within the next 12 hours.
Why is a rapid reduction unfavourable
A steep decline in serum osmolarity may also precipitate CPM. (Central pontine myelinolysis)
What should be plotted on a graph during monitoring
Guidelines suggest that serum osmolarity, sodium and glucose levels should be plotted on a graph to permit appreciation of the rate of change. They should be plotted hourly initially.
How can osmolarity be calculated if lab not available
2Na + glucose + urea
What does a reduction in serum osmolarity lead to
A reduction of serum osmolarity will cause a shift of water into the intracellular space. This inevitably results in a rise in serum sodium (a fall in blood glucose of 5.5 mmol/L will result in a 2.4 mmol/L rise in sodium).
What indicates insufficient fluid replacement
If the inevitable rise in serum Na+ is much greater than 2.4 mmol/L for each 5.5 mmol/L fall in blood glucose this would suggest insufficient fluid replacement. Rising sodium is only a concern if the osmolality is NOT declining concurrently.
What is a safe rate of plasma glucose decline
A safe rate of fall of plasma glucose of between 4 and 6 mmol/hr is recommended. The rate of fall of plasma sodium should not exceed 10 mmol/L in 24 hours.
What is the target blood glucose
A target blood glucose of between 10 and 15 mmol/L is a reasonable goal.
How long does complete normalisation of electrolytes and osmolality take
may take up to 72 hours
Why does insulin cause a dramatic fall in glucose
Because most patients with HHS are insulin sensitive (e.g. it usually occurs in T2DM), administration of insulin can result in a rapid decline of serum glucose and thus osmolarity.
Apart from CPM what else can insulin treatment lead to
Insulin treatment prior to adequate fluid replacement may result in cardiovascular collapse as the water moves out of the intravascular space, with a resulting decline in intravascular volume.
What is measured to determine if insulin is required
Ketones
When is insulin administered
If significant ketonaemia is present (3β-hydroxy butyrate is more than 1 mmol/L) this indicates relative hypoinsulinaemia and insulin should be started at time zero (e.g. mixed DKA / HHS picture).
What is the recommended insulin dose
The recommended insulin dose is a fixed rate intravenous insulin infusion given at 0.05 units per kg per hour.
How pronounced are the potassium changes
Patients with HHS are potassium deplete but less acidotic than those with DKA so potassium shifts are less pronounced
