Microvascular complications of diabetes Flashcards
What are acute complications of T1DM?
> Ketoacidosis
> Hypoglycaemia
What are chronic microvascular complications of T1DM?
Retinopathy
Neuropathy
Nephropathy
What are chronic macrovascular complications of T1DM?
Ischaemic heart disease
Peripheral vascular disease
Cerebrovascular disease
Name the two landmark trials comparing conventional with intensive treatment
> DCCT
> UKPDS
Describe the intensive treatment used in T1DM
Injection of long-acting insulin once a day = basal - prevents ketone formation
Bolus insulin at meal times
What is glycaemic control important for?
Can help to prevent microvascular disease
Isn’t important for macrovascular disease
What factors are important in macrovascular disease?
General cardiovascular risk factors
- cholesterol levels
- HTN
- smoking
What are the causes of microvascular disease?
> Capillary damage
> Metabolic damage
Describe how capillary damage leads to microvascular disease
hyperglycaemia -> structural/functional abnormalities in small blood vessels -> increased blood flow -> increased capillary pressure -> thickened/damaged vessel walls -> endothelial damage = exudate (leakage of albumin and other proteins)
Describe how metabolic damage leads to microvascular damage
Most tissues require insulin to take up glucose except retina/kidneys/nerves
Glucose flows across cell membranes and is metabolised to sorbitol by aldose reductase
What metabolic changes occur as a result of glucose conc. rising?
- Excessive glucose enters polyol pathway (insulin-independent glucose pathway)
- sorbitol accumulates
- Less NADPH is available for cell metabolism
- Build-up of ROS and oxidative stress
- Cell damage ensues
What disease is associated with microvascular complications?
Diabetes-specific
Only occurs with longstanding hyperglycaemia
Which type of diabetes is microvascular complications more of an issue for?
T1DM
T2DM will usually die of CV disease first
What is the common onset of microvascular complications in diabetic patients?
T1DM = takes a few years to develop
T2DM = may be present at diagnosis because they may have had the condition for a long time already
What is the treatment for microvascular complications?
No cure
Early detection is key
What are the common features of early stage (non-proliferative retinopathy?
- Microaneurysms
- Dot haemorrhages
- Hard exudates
- Cotton wool spots
Describe how microaneurisms occur in early stage retinopathy?
Hyperglycaemia causes damage to small vessel wall -> microaneurysms
Describe how dot haemorrhages occur in early stage retinopathy?
Occur when the vessel wall is breached
Describe how hard exudates form in early stage retinopathy?
From the protein and fluid left behind
Describe how cotton wool spots occur in early stage retinopathy?
As a result of micro-infarcts
What are common features of late stage retinopathy?
- Damage to veins
- Ischaemia
- Fluid build up
Describe the results of venous damage in late stage retinopathy
Causes:
- venous budding
- blockage of blood supply
Describe the results of ischaemia in late stage retinopathy
-> VEGF and other growth factors
- neovascularisation occurs but these new blood vessels are very fragile and can easily rupture -> Haemorrhages
- proliferative retinopathy
- vitreous haemorrhage
Describe the results of fluid build up in late stage retinopathy
fluid not cleared from the macular area -> macular oedema
How can retinopathy be prevented?
- Good glycaemic control
- Smoking cessation
- Good BP control
How can retinopathy be treated?
Address risk factors Opthalmic review: - laser - VEGF inhibitors (bevacizumab) - vitectomy
How is retinopathy screened?
- Annual retinal screening from the age of 12 years old
- camera
- refer to opthalmology if sight threatening
What are the stages of diabetic nephropathy?
- Renal enlargement and hyperfiltration
- Microalbuminuria
- Macroalbuminuria
- End stage renal failure
Process occurs over many years
What is microalbuminuria?
Tiny traces of albumin
- too small to be detected on dipstick
defined as 30-300 mg albumin/24 hours (normal <20)
ACR > 3.5mg/mmol
Independent CV disease predictor
What is the pathophysiology of microalbuminuria
> renal hypertrophy
increase in GFR
afferent arteriole vasodilates
- golmerular pressure is increased
- thickened glomerular basement membrane
- capillary damage due to shear stress on endothelial cells
End result = leakage of protein into urine
What is the pathophysiology of the later steps of microalbuminuria?
- Progressive glomerulosclerosis
- Glomeruli destroyed
- Progressive proteinuria - nephrotic range
- Renal failure
How is nephropathy screened?
Microalbuminuria is screened every year from diagnosis
How is microalbuminuria treated?
If present, start with ACEi/angiotensin receptor blocker
(helps to prevent progression to macroalbuminuria)
Aggressive CV risk reduction
- BP <125/75
- Statin
- Smokin cessation
Improve glycaemic control
Refer to renal clinic once patients develop CKD (eGFR <30)
What are the different types of neuropathy?
Peripheral (sensory) neuropathy -> most common )glove and stoking distribution)
Autonomic neuropathy
Mononeuritis multiplex = peripheral neuropathy with damage to 2+ areas
Diabetic amyotrophy = proximal diabetic neuropathy
What tissue changes are noted in diabetic neuropathy?
capillary damage, including occlusion in the vasa nervorum
reduced blood supply to the neural tissue results in impairments in nerve signalling that affect both sensory and motor function
How does diabetic neuropathy occur?
Glucose leads to inability to transmit signals through nerves
Diabetic neuropathy:
- metabolic changes = sorbitol accumulation
- vascular changes = capillary damage
- structural changes
What are the signs of diabetic neuropathy?
- Numbness or loss of feeling (asleep or ‘bunched up sock under toes’ sensation)
- Prickling/tingling
- Aching pain
- Burning pain
- Lancinating pain (sudden, sharp, severe burst of pain)
- Unusual sensitivity or tenderness when feet are touched (allodynia)
What are the symptoms of diabetic neuropathy?
- Diminished vibratory perception
- Decreased knee and ankle reflexes
- Reduced protective sensation such as pressure, hot and cold, pain
- Diminished ability to sense position of toes and feet
What are the treatment options for diabetic neuropathy?
Duloxetine (or amitriptyline) - SSRI
Amitriptyline (or pregabalin) - TCA
Refer to pain clinic:
- Try tramadol (opiod)
- Try topical lidocaine (anaesthetic)
What is diabetic foot?
Combination of neuropathy (damaged nerve supply) and peripheral vascular disease
- infection
- ulcers
- ischaemia -> reduced blood flow impairs healing
What does NICE classify as low risk features for diabetic foot and what recommendations are given?
Normal sensation and pulses
Annual review
What does NICE classify as medium risk features for diabetic foot and what recommendations are given?
Neuropathy OR absent pulses
Review by podiatrist ever 3-6/12
What does NICE classify as high risk features for diabetic foot and what recommendations are given?
Deformities OR ulceration
Review by podiatrist every 1-3/12
What is Charcot foot?
Progressive degeneration of weight-bearing joint
How does Charcot foot occur?
Numb foot - no sensations
- repetitive microtrauma results and goes unnoticed
- stress fractures
Increase in dysregulated blood flow to the foot due to vascular disease
- increased bone turnover
- fragile bone
How does Charcot foot present?
With a hot, red, flat foot
How is Charcot foot treated?
Needs to be completely immobilised in a plaster cast
What are the effects of autonomic neuropathy on different systems?
CV = postural hypotension GU = erectile dysfunction GI = gustatory sweating (sweating after ingesting food), gastroparesis (delayed gastric emptying
What are the different autonomic neuropathies?
Diabetic amyotrophy
- painful proximal neuropathy
- usually affects thigh/buttock
- msucle wasting or weakness, pain, or changes in sensation/numbness of the leg
Mononeuritis multiplex
- painful, asymmetrical motor and sensory neuropathy
- 2 or more nerves
What does the annual review of a diabetic patient comprise of?
HbA1c Cholesterol, HDL, TG Creatinine Microalbuminuria Lifestyle (exercise, diet, smoking) Drug therapy Mental well-being Visual acuity Retinal screening Pedal pulses Foot sensation BMI BP Erectile dysfunction Contraception
What needs to be considered in pregnancy for a diabetic patient?
HbA1c at time of conception (key to reducing risk of congenital malformations)
Glycaemic control during pregnancy helps to prevent macrosomia
Measure baby’s abdominal circumference weekly until birth
How do insulin pumps work?
deliver insulin in a more physiological way - basal rate then bolus around meals
What are the disadvantages of insulin pumps?
no background insulin in system if pump fails
training and self management
What is continuous glucose monitoring
monitor sits in interstitial fluid and gives a reading every 5 minutes
- insulin can be adjusted according to pattern
What is a closed loop system
artificial pancreas
aim is to remove patient management from equation creating a closed loop between pump and monitor
