HHS Flashcards
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clinical features of HHS ?
fatigue, lethargy, altered consciousness, hypotension and tachycardia
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diagnostic criteria for HHS
hypovolaemia,
hyperglycaemia (blood sugar > 30mmol/L)
and a serum osmolality > 320mosmol/kg
important to measure lactate levels as they are raised in patients with dehydration, sepsis and ischaemia, with higher levels suggesting more severe illness
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treatment for HSS ?
Intravenous (IV) 0.9% sodium chloride solution is the first line fluid .
Important to remember isotonic 0.9% sodium chloride solution is already relatively hypotonic compared to the serum in someone with HHS.
Therefore in most cases very effective at restoring normal serum osmolarity.
If serum osmolarity is not declining despite positive balance with 0.9% sodium chloride, then fluid should be switched to 0.45% sodium chloride solution which is more hypotonic relative to the HHS patients serum osmolarity.
IV fluid replacement should 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.
Fluid replacement alone (without insulin) will gradually lower blood glucose which will reduce osmolality
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). This is not necessarily an indication to give hypotonic solutions. 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.
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.
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.
Measurement of ketones is essential for determining if insulin is required.
If significant ketonaemia is present (3β-hydroxy butyrate is more than 1 mmol/L) indicates relative hypoinsulinaemia and insulin should be started at time zero (e.g. mixed DKA / HHS picture).
Recommended insulin dose is a fixed rate intravenous insulin infusion given at 0.05 units per kg per hour.
If significant ketonaemia is not present (3β-hydroxy butyrate is less than 1 mmol/L) then do NOT start insulin.
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omplications associated with a raised serum osmolality
g. thrombosis) or from rapid correction of serum osmolality (cerebral oedema).
rapid changes of serum osmolarity are dangerous and can result in cardiovascular collapse and central pontine myelinolysis (CPM).
Therefore, it is vitally important that during a patient’s treatment of HHS, that serum osmolality is monitored.
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