hyperosmolar hyperglycaemic state

Question 1

HHS occurs in those

Answer 1

with type 2 diabetes mellitus

Question 2

HHS is much

Answer 2

less common than DKA but has a much higher mortality

Question 3

when does it most commonly occur

Answer 3

in those with type 2 diabetes mellitus who have a concomitant illness which leads to reduced fluid intake causing significant dehydration

Question 4

pathophysiology 1

Answer 4

relative insulin deficiency with a concomitant rise in the counter-regulatory hormones causes hyperglycaemia, the relative insulin deficiency is not great enough to cause significant lipolysis or ketogenesis but there is not enough insulin to combat the hyperglycaemia

Question 5

pathophysiology 2

Answer 5

normally all of the glucose filtered by then kidneys is reabsorbed but when blood glucose levels reach 10mmol/l the proximal tubualr transport of glucose from the tubular lumen into the renal interstitial becomes saturated and further glucose resorption is impossible, the excess glucose is then excreted in the urine and causes an osmotic diuresis and pulls water with it causing severe dehydration, the loss of water causes an increased serum osmolality as it increases the amount of sodium and potassium in the blood

Question 6

presentation

Answer 6

xerostomia, polydipsia and polyuria, fever, focal or global neurological deficits, hallucinations

Question 7

management

Answer 7

1. 0.9% sodium chloride over first 12 hours REPLACE 50% of estimated fluid lost and by 24 hours aim to replace 100% of estimated fluid losses
2. start low dose insulin of 0.05 units per kg per hour only if there is significant ketonaemia on admission of if the blood glucose levels are falling at a rate of less than 5mmol/hour
3. commence prophylactic anti-coagulation with low molecular weight heparin

Question 8

HHS is characterised by

Answer 8

hypovolaemia
hyperglycaemia (without significant acidosis or ketonaemia)
hyperosmolality (greater than 320 mosmol/kg)

Question 9

typical biochemistry

Answer 9

• hyperglycaemia which is usually much higher than in DKA (median is around 60)
• significant renal impairment
• significant elevation of osmolality
• ketones may be slightly elevated but nothing of that in DKA

Question 10

how do you calculate osmolality

Answer 10

2x (Na+K) + urea + glucose

Question 11

normal serum osmolality values

Answer 11

between 285 and 295

Question 12

what should you look out for throughout the treatment of HHS

Answer 12

complications of fluid overload

Question 13

why is hyperglycaemia greater in HHS than in DKA

Answer 13

because in DKA the acidosis symptoms cause the patient to present much earlier and because it mostly occurs in younger patients they usually have a higher glomerular filtration rate so have a greater ability to pee out the excess glucose

Question 14

why does HHS have a higher mortality than DKA

Answer 14

not actually because of the mechanism of HHS but because HHS occurs in older people usually from a concomitant illness which is usually the reason for death