Microvascular complications Flashcards
what are the sites of microvascular complications of diabetes?
1) retinal arteries
2) glomerular arteries i.e. kidneys
3) vasa nervorum i.e. vessels that supply the nerves
how are microvasc complications exacerbated?
- severity of hyperglycaemia:
the worse the hyperglycaemia, the worse the damage.The higher the HbA1C, the worse the microvascular complications.
-Hypertension.
-Genetic.
-Hyperglycaemic memory
– poor diabetes control, even for a brief period, will give an increased risk of microvascular complications compared to someone that has had good control throughout. - Tissue damage through originally reversible and later irreversible alterations in proteins.
what are involved in the mechanisms of glucose damage?
o Polyol pathway.
o AGEs.
o Protein kinase C.
o Hexosamine.
what is affected in diabetic retinopathy?
retina
can involve the macula (involved in colour vision and acuity)
located centrally
what are the 4 types of retinopathy?
1) background DR
2) Pre-proliferative DR
3) proliferative DR
4) maculopathy
what are the features of Background Diabetic Retinopathy?
o Hard exudates due to protein leakage (looks yellow)
o Microaneurysms – small blood vessels bulge/sprout
o Blot haemorrhages – blots of blood.
pre-proliferative DR (diabetic retinopathy)
o Cotton wool spots (soft exudates)
– indicative of retinal ischaemia
looks faded yellow
proliferative DR (diabetic retinopathy)
o Visible new vessels – on disc or elsewhere in retina (angiogenesis)
not well organised around the area of ischaemia i.e. not straight and grow in multiple direction s
what is the feature of maculopathy?
similar to background retinopathy
o Hard exudates NEAR macula – threatens direct vision.
other:
- microaneurysm
- blot haemorrhages
management of background DR
improve blood glucose control
warn patient of the early signs
how is pre-proliferative DR managed?
suggests general ischaemia therefore stop it progressing to proliferative by pan-retinal photocoagulation (laser to retina)
management of maculopathy
grid-retinal photocoagulation for just the macula
what are the features of diabetic nephropathy?
hypertension
progressive increasing proteinuria
deteriorating kidney function
classic histological features.
what risk is associated with CKD and diabetes?
risk of CV events increases
what are the histological features of DN?
Glomerular:
- Mesangial expansion.
- Basement membrane thickening.
- Glomerulosclerosis – hardening of capillaries.
If there is no retinopathy, any CKD cannot be due to diabetes – these come together.
Vascular.
Tubulointestinal.
how common is CKD in T1DM?
20-40% of T1DM patients have CKD after 30-40 years.
how common is CKD in T2DM?
probably the same as T1DM (20-40%) but difficult to determine due to
– age of development of T2DM, racial factors, age at presentation, loss due to cardiovascular morbidity instead.
what are the clinical features of Diabetic Nephropathy?
what is the hallmark feature?
1) Progressive proteinuria (hallmark for CKD) due to leaky glomerulus
o Normal range = <30mg/24hrs.
o Nephrotic range = >3000mg/24hrs.
2) Increased BP.
3) decreased renal function (GFR decrease)
what are the interventions for DN?
- diabetic control (the lower the HbA1C, the lower the microvascular complications.)
- BP control (control of blood pressure will slow down the deterioration of kidney function.)
- inhibition of RAS (ACE inhibitors reduce rate of decline of creatinine and thus kidney function. AngII is involved in growth and inflammatory pathways, thus inhibiting is good.
- stopping smoking
example of ANGII receptor blocker (antagonist)
irbesartan
what causes the production of renin in the juxta-glomerular cells?
- low perfusion pressure
- ## low tubular sodium
where is ACE found?
in the lungs
what can drugs target in RAS?
o Drugs blocking renin activity.
o ACE inhibitors.
o AT1 antagonists.
what does diabetic neuropathy lead to in the later stages?
lower limb amputations due to blockage of blood supply to nerves
types of DNeuro?
- peripheral neuropathy (affecting peripheral nerves-most common)
- mononeuropathy (affecting one nerve- blocked)
- mononeuritis multiplex (many nerves affected)
- radiculopathy (dermatomes affected, pain over spinal nerves)
- autonomic neuropathy
- diabetic amyotrophy (inflammation and loss of pain)
peripheral neuropathy
- Affects the longest nerves that supply the feet and result in a loss of sensation.
- More common in tall people and people with poor glucose control.
Dangerous: people will not sense damage to the foot–> Charcot’s Foot
- investigated with monofilament examination – tracks loss of sensation.
- Characteristics – loss of ankle jerks, loss of vibration sense, multiple fractures on x-ray (Charcot’s joint).
what is mononeuropathy?
two common signs?
motor loss of single nerve:
Usually sudden motor loss resulting in wrist and foot drop.
1) Cranial nerve palsy – double vision due to 3rd nerve palsy (“down and out”).
what is affected in cranial nerve 3 palsy?
- Lateral rectus – abducent nerve – OUT.
- Superior oblique – trochlear nerve – DOWN.
- Pupil does respond to light.
what 2 ways is the pupil affected in 3rd nerve palsy?
o Pupil-sparing:
PNS fibres on the outside thus they do not easily lose blood supply.
o Fixed dilated pupil:
An aneurysm can also case 3rd nerve palsy BUT the aneurysm will press on PNS fibres and cause a fixed dilated pupil.
what makes up mononeuritis multiplex?
random combination of peripheral nerve lesions
which dermatomes are usually affected in radiculopathy?
Radiculopathy: pain over spinal nerves therefore affects dermatomes
abdomen or chest wall
pain over spinal nerves
what nerves are lost in autonomic neuropathy?
loss of SNS and PNS neves to GI tracts, bladder and CVS
what is the effect of losing the nerves in autonomic neuropathy?
- Gi tract – dysphagia, delayed gastric emptying, constipation/nocturnal diarrhoea, bladder dysfunction (more SNS)
- Postural hypotension (vasodilation)
- Cardiac autonomic supply – can have sudden cardiac death (PNS dominance overcome)
how can autonomic neuropathy be detected?
measure changed in HR in response to Valsalva manoeuvre
there should be a change in HR
look at ECG and compare R-R interval
