Hyperosmolar hyperglycaemic state Flashcards
What proportion of all diabetes-related hospital admissions does HHS account for?
less than 1%
What is the reported mortality rate of HHS?
10-20% (higher than DKA)
What are 4 causes of HHS in type 2 diabetics?
- Infection
- Medications that cause fluid loss or lower glucose tolerance
- Surgery
- Impaired renal function
In what patient group is HHS most common?
elderly with T2DM (can be the initial presentation)
Why is it important to differentiate HHS from DKA?
management is different, and treatment of HHS with insulin e.g. as part of DKA protocol can result in adverse outcomes
Where are patients with HHS best managed and why?
High dependency unit because first 24h of treatment is very labour intensive
What are 4 key examples of complications of HHS?
- Vascular complications: MI, stroke, peripheral arterial thrombosis
- Seizures
- Cerebral oedema
- Central pontine myelinolysis (CPM)
What is central pontine myelinolysis / osmotic demyelination syndrome?
can occur due to over-correction of severe hyponatraemia
symptoms are dysarthria, dysphagia, paraparesis or quadriparesis, seizures, confusion, coma - Locked in syndrome (awake but can’t communicate verbally/move)
Over what time frame does HHS develop and how does this affect the clinical picture?
comes on over many days - causes extreme metabolic disturbances and dehydration
What are the 3 key diagnostic criteria in hyperosmolar hyperglycaemic state (HHS)?
- Severe hyperglycaemia (>30 mmol/L) without significant ketonaemia or acidosis
- Hypotension
- Hyperosmolality (usually >320 mosmol/kg; normal 275-299)
What is the pathophysiology of HHS?
- hyperglycaemia results in osmotic diuresis with associated loss of sodium and potassium
- Severe volume depletion results in a significant raised serum osmolarity (typically > 320 mosm/kg) resulting in hyperviscosity of blood
Why might patients with HHS not looked as dehydrated as they are, despite severe electrolyte losses?
hypertonicity leads to preservation of intravascular volume
What are 9 possible presenting features of HHS?
- Nausea and vomiting
- Lethargy, fatigue
- Weakness
- Confusion
- Headaches
- Dehydration, hypotension, tachycardia
- Coma
- Seizure
- Hyperviscosity of blood may cause MI, stroke, peripheral arterial thrombosis
What are 4 possible signs of HHS on examination?
- Altered level of consciousness
- Papilloedema
- Hypotension
- Tachycardia
Are DKA and HHS always distinct?
no, a mixed picture can occur - more of a spectrum
What is the main difference between DKA and HHS?
in T2DM, patients have sufficient endogenous insulin production to switch off ketone production and prevent ketonaemia
What are the 3 key goals of management of HHS?
- Normalise the osmolality (gradually)
- Replace fluid and electrolyte losses
- Normalise blood glucose (gradually)
In addition to the 3 key goals of HHS what are 3 further considerations for tretament?
- Prevent arterial or venous thrombosis
- Prevent potential complications e.g. cerebral oedema/ central pontine myelinolysis
- Prevent foot ulceration
What are fluid losses estimated to be in HHS?
between 100-220 ml/kg e.g. 10-22L in individual weighing 100kg
What must be taken into accoutn when determining the rate of rehydration in HHS?
determined by assessing combination of initial severity and any pre-existing co-morbidities e.g. heart failure, chronic kidney disease
need to be cautiou in elderly - if too rapid, can precipitate heart failure, but insufficient may fail to reverse AKI
What is the first line fluid for restoring total body fluid?
IV 0.9% sodium chloride solution
1L over 1-2 hours, then add potassium chloride and 1L over next 2-4 hours, 1L over 4-6 hours, 1L over 6-8 hours, 1L over 8-10 hours
What is the formula that can be used to calculate a surrogate for osmolality if the laboratory don’t measure it?
osmolality = 2Na+ + glucose + urea
How frequently should osmolality be calculated during the management of HHS?
hourly
What should determine the rate of NaCl delivery in the management of HHS?
adjust to ensure gradual decline in osmolality
What is the first line choice of fluid replacement in HHS and why?
IV 0.9% NaCl because it is already hypotonic compared to the serum in someone with HHS, so in most cases is effective as restoring normal serum osmolarity
If serum osmolarity is not declining despite positive balance with 0.9% NaCl, what should be the next step?
switch fluid to 0.45% sodium chloride solution - more hypotonic relative to HHS patients’ serum osmolarity
What is the aim in terms of specific parameters when giving IV fluid replacement in HHS?
aim is to achieve a positive balance of 3-6 L by 12 hours and remaining replacement of estimated fluid losses within the next 12 hours
Should insulin treatment be used in the first instances in HHS and why?
no, give initial fluid replacement without insulin as a rapid recline in plasma glucose is potentially harmful, so insulin should not be used in first instance unless significant ketonaemia or acidosis
What is the key parameter to monitor when managing HHS?
omsmolality, to which glucose and sodium are main contributors
Why are rapid changes in serum osmolarity dangerous?
can result in cardiovascular collapse and central pontine myelinolysis (CPM)
How is it recommended that osmolarity is monitored during HHS treatment?
plot osmoalrity, sodium and glucose levels on a graph to permit appreciation of rate of change
initially plot hourly
What will happen to sodium as fluid replacement is given in HHS and how should this be managed?
- inevitable rise in sodium as reduction of serum osmoarity will cause shift of water into the intracellular space
- fall in blood glucose of 5.5 mmol/L will result in 2.4 mmol/L rise in sodium
- not necessarily indication to give hypotonic solutions; if much greater rise than 2.4 mmol/L of sodium for each 5.5 mmol/L fallin blood glucose - suggests insufficient fluid replacement
What change in the level of sodium during HHS treatment would suggest insufficient fluid replacement?
if rise in sodium is much greaer than 2.4 mmol/L for each 5.5 mmol/L fall in blood glucose
What is the only time when a rise in sodium in the treatment of HHS is of concern?
only if osmolality is not declining concurrently
What is recommended as a safe rate of fall of plasma glucose in HHS management?
4-6 mmol/hour
What should a fall in sodium during the management of HHS not exceed?
should not exceed >10 mmol/L in 24 hrs
What is a reasonable target blood glucose in the management of HHS?
between 10-15 mmol/L
How long might it take for complete normalisation of electrolytes and osmolality following treatment of HHS?
may take up to 72h
Why can giving insulin treatment prior to adequate fluid replacement in HHS cause cardiovascular collapse?
as water moves out of the intravascular space, causing a decline in intravascular volume
steep decilne in osmolarity due to big drop in glucose can precipitate CPM
What is the essential measurement to determine if insulin is required in the management of HHS?
measurement of ketones: if significant ketonaemia (3 beta-hydroxybutyrate >1 mmol/L) - indicates relative hypoinsulinaemia, insulin should be started at time zero
What is the recommended way to give insulin in a mixed DKA/HHS picture?
fixed rate intravenous insulin infusion (FRIII) given at 0.05 units per kg per hour (half rate in DKA)
In addition to fluid replacement and insulin what are 5 other important aspects of the management of HHS?
- Anti-infective therapy
- Anticoagulation - all patients should be given LMWH
- Foot protection to prevent pressure ulceration
How do potassium levels determine whether potassium replacement should be given in HHS?
- if >5.5 mmol/L: nil
- 3.5-5.5: 40 mmol/L
- < 3.5 mmol/L: senior review as additional potassium required
What is a suggestion of the rate of fluid resuscitation, depending on individual patient factors, in HHS?
0.9% saline:
- 1L over 1-2 hours
- 1L +/- KCl over 2-4 hours
- 1L +/- KCl over 4-6 hours
- 1L +/- KCl over 6-8 hours
- 1L +/- KCl over 8-10 hours
change to 0.45% saline only if failing to reduce osmolality by approx 5 mOsm/kg/hour
What anti-infective therapy is recommended in HHS?
seek infective source in acutely ill patients even without pyrexia: clinical history + examination and CRP
antibiotics should be given if clinical signs of infection or on imaging and/or laboratory tests
What anticoagulation should be given in HHS?
all patients should receive prophylactic LMWH for full duration of admission unless contraindicated
What complication should you be aware of when a patient starts to eat again after treatment of HHS, particularly in elderly/malnourished patients?
refeeding syndrome (low phosphate, magnesium potassium)
What should be done in terms of foot protection from ulcers in HHS?
initial foot assessment, apply heel protectors if neuropathy/peripheral vascular disease/ lower limb deformity
if too confused/sleepy to cooperate with assessment, assume at high risk
What electrolyte may need to be supplemented to prevent refeeding syndrome?
oral or IV phosphate replacement if hypophosphataemia persists beyond acute phase of treatment of HHS
What anti-diabetic medication are patients likely to be placed on following HHS treatment?
- subcutaneous insulin
- if previously undiagnosed diabetes/ well-contrlled on oral agents, switch from insulin to oral hypoglycaemic agent should be considered after period of stability (weeks/months)
- referral to specialist diabetes team as soon as possible after admission
