Screeningautonomic neuropathy symptomatic patients

Apart from blood pressure, tests for autonomic neuropathy are usually reserved for symptomatic patients. Some are complex. The following can be done with a sphygmomanometer and an ECG machine:

1 Lying and standing systolic blood pressure. Normal fall < 10 mmHg; abnormal fall > 30 mmHg.

2 Heart rate during and after Valsalva manoeuvre. Find pulse, ask patient to breathe in, then to try to push the breath out hard against a closed glottis for as long as they can. Count the pulse once they've started. Then count the rate as they relax afterwards. It is much easier with an ECG machine. Rate during/rate after: normal > 1.21; abnormal < 1.20. Do not do this in people with proliferative retinopathy.

3 Heart rate after standing '30:15 test'. Attach the ECG and make sure the patient will be able to get up easily. Once the ECG is recording continuously ask the patient to stand and mark the ECG as they start to do so. Calculate the ratio of the longest R—R interval (about the 30th beat after they start standing over the shortest R—R interval (about the 15th beat after they start standing): normal > 1.04; abnormal < 1.0.

These tests are fraught with practical difficulties (patients who find it hard to stand up, ECG leads fall off, etc.).

Postural hypotension

There may be a marked fall of blood pressure for some minutes after standing, with or without feelings of dizziness. Some patients have falls or blackouts. Some patients cannot even sit up in bed without fainting. Postural hypotension can be made worse by fluid depletion, hypotensive treatment, diuretics, nitrates and other vasodilators, psychotropic drugs (such as tricyclics).

Remove or reduce drugs worsening the situation and ensure adequate hydration. Compression stockings may help, as may fludrocortisone in severe cases.

Altered sweating

Patients may sweat less on the feet but more in the upper half of the body. This includes gustatory sweating—facial sweating precipitated by spicy or highly flavoured foods. Avoiding these foods may help. The lack of moisture in the feet may lead to dry skin and moisturizing cream can be used except between the toes.

Gastroparesis

Slow stomach emptying can cause abdominal discomfort, hypoglycaemia, and vomiting. In rare cases the vomiting may be debilitating and require hospital admission. Metoclopramide may improve stomach emptying. Oesophageal motility may also be abnormal and some patients may experience swallowing problems.

Diarrhoea or constipation

Either of these symptoms should be investigated in the usual way before attributing them to diabetic neuropathy. Diabetic diarrhoea can be distressing. It comes in bouts of days or weeks, with urgency, especially at night. Codeine or loperamide may help. In more severe cases a short trial of a broad spectrum antibiotic like neomycin is sometimes successful. The rationale is that this reduces bacterial overgrowth in the abnormal bowel. Constipation can be treated by continuing the high-fibre diet (but not if there is gastroparesis), plenty of soft fruit, and laxatives if needed.

Urinary retention

This occurs imperceptibly. The bladder slowly enlarges with an increasing postmiction volume. This forms a reservoir for infection. Once the patient is made aware of the problem, regular urination with pressure in the suprapubic region may help. If the person suffers recurrent urinary infections, prophylactic antibiotics such as trimethoprim may be required. Other causes of urinary retention, such as prostatism, must be excluded. They may coincide.

Sudden death

This may obviously happen at any time but people with autonomic neuropathy are at especial risk if they become hypoxic or during anaesthesia. The anaesthetist should always be made aware that the patient has autonomic neuropathy and anaesthesia should be performed only in a hospital with full resuscitation and medical support.

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