Most diabetic complications are due to poor blood glucose control, particularly if this is prolonged. The Diabetes Control and Complications Trial1 showed that with type-1 diabetes, the risk of complications such as renal damage and eye disease increases with an HbA1c level above 9 per cent and is raised considerably if it is above 12 per cent.
Patients with type-2 diabetes are more at risk of vascular complications such as MI, stroke and peripheral vascular disease, but are also at risk of small vessel disease.
The UKPDS2 found that strict control of HbA1c to ≤7 per cent resulted in a 25 per cent risk reduction for complications such as eye and kidney disease compared with poorly-controlled patients.
The key to minimising complications is to control blood glucose, BP and hyperlipidaemia. If this is done together with a programme promoting a healthy lifestyle, regular exercise and not smoking, risk is further reduced.
Hypoglycaemia is a significant complication of poorly managed diabetes, and patients should understand the danger to cerebral function of repeated, severe hypoglycaemic episodes.
They should be advised how to avoid hypoglycaemia, and this should include carers and, if appropriate, co-workers. Patients must also be aware of the additional risks of hypoglycaemic attacks in situations such as driving and swimming.
Ketoacidosis is a serious metabolic complication and usually occurs in patients with type-1 diabetes during concomitant illness, surgery or trauma. Patients and carers need to be able to recognise potentially dangerous situations and signs of ketoacidosis; management involves early admission to hospital.
Disease of the coronary arteries, the cerebral vasculature and the peripheral arteries are all common, potentially serious complications of diabetes. Minimising the risk involves good blood glucose control and encouraging the patient to make appropriate lifestyle choices.
Hypertension must be vigorously treated. NICE recommends that for patients with type-2 diabetes with kidney, eye or cerebrovascular damage, the target BP should be <130/80mmHg. For others, the target BP is <140/80mmHg. In primary care, type-2 diabetes evaluation should be based on the systolic value.
Lipid control also needs careful consideration. In type-1 diabetes, the timing of intervention with statins is an unresolved issue, and the question of whether all type-2 diabetics should receive a statin is much debated.
With these uncertainties and differences in opinion, it may be wise to check if your PCT has a specific policy.
Aspirin and thrombotic risk
NICE recommends that patients it defines as moderately high risk - this includes patients over 35 years, having a poor family history, belonging to a high-risk ethnic group, and/or have abnormalities of lipids or BP - should take aspirin 75mg daily. Diabetes UK currently recommends aspirin for all diabetics over the age of 50, whatever their other risk factors.
However, guidelines are under review in the light of UK research carried out in 2008,3 which found no benefit from aspirin or antioxidant treatment in the prevention of MI in patients with diabetes.
Diabetic retinopathy is a major cause of impaired vision and blindness, but is largely preventable by good diabetic control, and treatable if detected early.
Over 40 per cent of patients who have had diabetes for 15 years or more have some evidence of retinal involvement.
Patients should have eye examinations annually, including digital photography. Should new vessel formation, pre-proliferative retinopathy or maculopathy be detected at the eye examination, the patient should have a rapid review by an ophthalmologist.
Diabetic nephropathy tends to develop after many years and results in progressive loss of renal function. The first evidence is usually microalbuminuria.
Diabetic patients should have an annual assessment of their albumin:creatinine ratio by first-pass morning urine and serum creatinine measurement.
If the result is >2.5mg/mmol for men or >3.5mg/mmol for women, this should first be confirmed and the patient then started on an ACE inhibitor or, if not tolerated, an ARB.
Other signs of possible renal impairment, including rise in BP, sudden proteinuria, haematuria and systemic ill-health, should be investigated.
All patients with evidence of renal damage should receive an ACE inhibitor.
Patients may experience deterioration of renal function and in end-stage failure will require dialysis or be considered for transplantation.
Diabetic neuropathy mainly affects the sensory nerves, although the motor nerves may be affected. Sensory loss to the feet can lead to considerable disability due to ulceration of the skin or Charcot osteoarthropathy.
Skin problems can be minimised by annual foot surveillance that includes education of the patient and looking for deformity, impaired sensation and checking the peripheral pulses.
Diabetic neuropathy can produce neuropathic pain. Initially this can be treated with simple analgesics and practical measures such as foot cradles.
If these measures are ineffective, low dosage tricyclic drugs can be tried, followed by a trial of gabapentin.
Male diabetic patients should be asked annually whether erectile dysfunction is a problem. Patients affected can be prescribed sildenafil, tadalafil and vardenafil. If these are ineffective, referral for specialist management should be considered.
It helps to bear in mind that particular symptoms in a diabetic patient may represent a complication of their disease rather than a simple intercurrent illness.
Psychological problems are also frequently encountered in patients with diabetes, and should be borne in mind.
- Dr Barnard is a former GP in Fareham, Hampshire
1. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes nellitus. The Diabetes Control and Complications Trial Research Group. N Engl J Med 1993; 329: 977-86.
2. Tight blood pressure control and risk of macrovascular and microvascular complications in type 2 diabetes. UK Prospective Diabetes Study Group. BMJ 1998; 317: 703-13.
3. The prevention of progression of arterial disease and diabetes (POPADAD) trial: factorial randomised placebo controlled trial of aspirin and antioxidants in patients with diabetes and asymptomatic peripheral arterial disease. Prevention of Progression of Arterial Disease and Diabetes Study Group; Diabetes Registry Group; Royal College of Physicians Edinburgh. BMJ 2008; 337: a1840.