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Systemic complications of diabetes

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Dr Ken Ho
MBBS(Hons) FRACP PhD Endocrinologist
Macquarie University Hospital, Campelltown Hospital, Ryde Hospital, Sydney NSW

 

Diabetes is a common metabolic condition affecting millions world-wide—7.4 per cent of Australians have diabetes; 16.3 per cent of the Australian population has pre-diabetes with a predicted lifetime diabetes risk of greater than 50 per cent.1

Diabetes is classified as type 1, type 2 or gestational.2  Type 1 diabetes arises from immune-mediated destruction of pancreatic islets resulting in diminished insulin, and glucagon production. Individuals suffer severe hypoglycaemia and hyperglycaemia.

Type 2 diabetes is characterised by insulin resistance and beta cell dysfunction. It is associated with obesity, physical inactivity, diets high in saturated fats, genes, medical illness and drugs, such as corticosteroids. Type 2 diabetes, hypertension, deranged lipids and obesity are collectively known as the Metabolic Syndrome.

Gestational diabetes is considered a pre-type 2 diabetic condition. Affected women are overweight and have a lifetime risk of type 2 diabetes.

 

Acute symptoms and complications

 

Uncontrolled hyperglycaemia is associated with metabolic acidosis and electrolyte disturbances. Diabetic ketoacidosis (DKA) ensues if untreated and results in multi-organ failure and coma. In milder situations, patients experience increased thirst, urination, unexplained weight loss, severe fatigue and blurred vision. They can develop infections of skin, urine and chest. Management is by increasing fluid intake orally or intravenously, replacing electrolytes, taking extra doses of oral anti-diabetic medications or insulin, and antibiotics for infection.3

 

Chronic complications

 

Chronic complications arise from years of poor glycaemic control.4 They are categorised into macrovascular, microvascular and neuropathic.

Macrovascular complications include diseases of the cardiovascular, cerebrovascular, peripheral vascular systems and limb amputations. Microvascular complications include retinopathy, nephropathy and cognitive impairment.

Dilated eye examinations can detect early diabetic retinopathy and are regarded as an integral part of optometry. People with diabetes are encouraged to have a dilated retina eye examination annually, but many diabetes sufferers do not attend regular eye check-ups. It is important to remember that the best way for a diabetic patient to prevent unnecessary vision loss is through annual retina eye examinations.

As the readers of Pharma are familiar with diabetic ocular complications, this aspect will not be discussed in this article. Neuropathic complications are categorised into peripheral or autonomic.

 

Cardiovascular

 

Diabetic individuals suffering heart attacks often describe non-specific symptoms such as fatigue or shortness of breath. They are investigated with electrocardiogram, exercise stress test or coronary angiogram.5 They are started on anti-platelet and lipid lowering agents, and encouraged to stop smoking. They may be suitable for percutaneous coronary intervention (PCI) such as balloon angioplasty with stenting or coronary artery bypass grafting (CABG). Patients who survive heart attacks develop chronic heart failure, reduced exercise tolerance and greatly diminished quality of life.

 

Cerebrovascular

 

An early warning of stroke is a transient ischaemic attack (TIA). Typical symptoms are tingling of an extremity, face or body, incoherent speech or acute confusion. Symptoms may last for up to 24 hours but persistence indicates a stroke in progress. Immediate assessment with brain CT or MRI, carotid duplex ultrasound and blood work is recommended. Anti-platelet and lipid lowering agents are commenced. Glycaemic, blood pressure and anti-smoking strategies must be instituted. Carotid endarterectomy may be proposed. This involves removing atheromatous plaques adherent to carotid endothelium. Individuals with recurrent strokes develop vascular dementia.6 However, diabetes is also a risk factor for Alzheimer’s disease.7

 

Peripheral vascular

 

Atheromatous accumulation leads to occlusion of peripheral limb arteries. Patients experience intermittent claudication pains exacerbated by walking. Collateral vessel formation can form natural bypasses and creates a stable situation for years. However, acute thrombus occlusion results in severe rest pain and threatens the limb. Patients may present with dusky, pulseless foot. They should be investigated with arterial leg Doppler ultrasound and referred for percutaneous endoluminal angioplasty or femoropopliteal bypass surgery. 

 

Peripheral neuropathy

 

Individuals affected by peripheral neuropathy experience reduced, altered and uncomfortable sensations of extremities. Their reduced ability to sense their physical environment results in recurrent feet ulcerations, infection, necrosis and limb amputations. They should be referred to high-risk foot services at major hospitals for fitment with CAM (controlled ankle motion) boots which can redistribute abnormal foot pressures and heal ulcers.8

189-OL.Figure -1_F 

Autonomic neuropathy

 

The autonomic nervous system controls heart rate, blood pressure, sweating, gastro-oesophageal and bowel functions, and penile erection. Affected individuals describe symptoms that include postural hypotension, bradycardia, dry skin, nausea, gastro-oesophageal reflux, chronic diarrhoea or constipation and erectile dysfunction.

 

Nephropathy

 

The kidney has millions of nephrons comprising glomerular capillaries, and nephron tubules. Chronically elevated blood glucose damages the glomerulus, resulting in protein leakage into urine, which can lead to the nephrotic syndrome characterised by fluid retention, and pulmonary oedema. When sufficient nephron units fail, renal failure ensues and dialysis treatment is eventually needed.

 

Glycaemic management

 

Prevention of diabetes-related complications requires good glycaemic control. The UK Prospective Diabetes Study (UKPDS) and the Diabetes Control and Complications Trial (DCCT), conducted by the US National Institute of Diabetes and Digestive and Kidney Diseases, showed that type 2 and type 1 diabetic patients have reduced microvascular complications such as retinopathy, and nephropathy if they can achieve HbA1c less than seven per cent.9

Ten years on, these individuals were protected from subsequent heart attacks, strokes and death;10,11 however, individuals who are aggressively managed report weight gain and frequent hypoglycaemia.

The ACCORD study in 2008 showed that rapidly achieving tight glycaemic control is associated with increased mortality in older diabetic patients with pre-existing cardiovascular complications.12  Therefore, glycaemic management must be individualised.13

 

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  12. Action to Control Cardiovascular Risk in Diabetes Study G, Gerstein HC, Miller ME, Byington RP, Goff DC Jr et al. Effects of intensive glucose lowering in type 2 diabetes. N Engl J Med 2008; 358: 2545-2559.
  13. Gunton JE, Cheung NW, Davis TM, Zoungas S, Colagiuri S, Australian Diabetes S. A new blood glucose management algorithm for type 2 diabetes: a position statement of the Australian Diabetes Society. Med J Aust 2014; 201: 650-653. 


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