VOL: 101, ISSUE: 29, PAGE NO: 46
Sharon Eustice, MSc, BPhil, RN, DN, is nurse consultant for continence, Cornwall and Isles of Scilly Health Community; Adrian Wragg, MB, FRCP, is consultant and senior lecturer in geriatric medicine, University College Hospitals, London
Nocturia has been defined as one or more voids (of urine) at night, each of which is preceded and followed by sleep (Abrams et al, 2002; van Kerrebroeck et al, 2002). It is a condition that can influence health status and quality of life; for example, daytime sleepiness can occur as a result of loss of sleep at night, and the resultant loss of energy can render many older people prone to accidents, such as falls (Box 1).
Overview of nocturia
It is unfortunate that nocturia is frequently considered a benign condition and a natural part of ageing. Lundgren (2004) suggests that over 50 per cent of both men and women over 60 are affected by this complaint. Yoshimura et al (2004) used a health screening questionnaire on 6,517 individuals (30 per cent female and 70 per cent male) and found that diabetes and hypertension are significant risk factors for nocturia. However, gender was not identified as an indicator.
Although there are multiple factors that can result in nocturia, it can be categorised in three ways:
Low nocturnal bladder capacity - This is defined as a nocturnal void of urine that is less in volume than the largest single voided volume in a 24-hour period (Weiss and Blaivas, 2000). Common causes include over-active bladder, bladder obstruction, infection, inflammation and malignancy. This results in low nocturnal bladder capacity, and may cause nocturnal frequency.
Nocturnal polyuria - Matthiesen et al (1996) suggest that nocturnal polyuria occurs when the nocturnal urine volume is greater than 6.4ml/kg of body weight. Saito et al (1993) suggest that nocturnal polyuria is the volume of urine passed at night that exceeds one-third of the total daily urine output. This statement is supported by Weiss and Blaivas (2000) who offer a definition of nocturia as 35 per cent or more of the 24-hour urine output. The fundamental feature of this type of nocturia is that more urine is produced during sleep than would normally be expected, and that this is greater than the bladder capacity which, in turn, creates the need to get up more than once in the night to void, or nocturnal enuresis (loss of urine during sleep) occurs.
Asplund (2004) reports that 24-hour urine output is usually normal or only slightly increased when a patient presents with nocturia, but that there is a shift in diuresis from daytime to night-time. This is thought to be a result of vasopressin system disruption. Vasopressin, also called antidiuretic hormone, regulates urine output by stimulating the reabsorption of water by the kidneys and reducing the production of urine. A reduction in the nocturnal levels of vasopressin or no detectable levels of the hormone is associated with nocturia.
Mixed aetiology nocturia - Some patients may present with both of the above and this is known as a mixed aetiology nocturia.
Causes of nocturia
Nocturia is thought to have a number of causes (Box 2), and treatment of the underlying cause can resolve the problem. However, there remains a degree of confusion about the causes of nocturia. A study by Rembratt (2003) found no significant association with hypertension, heart failure, angina pectoris, diabetes mellitus, snoring, use of diuretics or hypnotics or treatment for these conditions. What was observed, was a significant association between the number of nocturnal voids and incontinence, daytime urge incontinence and nocturnal thirst, suggesting a close association between nocturia and the occurrence of over-active bladder, or the frequency-urgency syndrome (Rembratt et al, 2003).
It is essential to establish what the patient regards as normal bladder function and how she/he is affected by the symptoms of nocturia. Fig 1 illustrates a simple algorithm to assist with the diagnosis of nocturia.
The usual pattern of fluid intake and alcohol consumption should be ascertained, as high consumption of, for example, caffeine may affect symptoms. A detailed drug history should look for the taking of any medication that might predispose to nocturnal voiding; for example, phenytoin, or odd timing of medication (for example, diuretics in the evening), in which case alterations to the regime should be made if possible. Assessment should then seek to exclude significant lower urinary tract pathology and associated disease; for example, Parkinson’s disease or urological/gynaecological conditions. Laboratory tests should be carried out to exclude metabolic causes of polyuria such as diabetes mellitus, and tests to exclude heart failure should be considered if dependent oedema in the lower limbs is a problem.
Bladder diary - The patient should be asked to compile a 24-hour bladder diary over three days so as to allow health professionals to assess the symptoms of nocturia (Jaffe-Jamison et al, 2002; Jackson, 1999). A distinction can then be made between low nocturnal bladder capacity and nocturnal polyuria, which will have a significant bearing on pharmacological management.
The options for treatment will depend on which category of nocturia has been identified. Treatment algorithms may be useful for clinical decision-making (Marinkovic et al, 2004; Weiss and Blaivas, 2000).
Treatment of nocturnal polyuria - Treatment of nocturnal polyuria should centre on the underlying reason for increased urine production at night. However, there will be occasions when the patient does not respond to this. Simple conservative measures, such as elevating oedematous legs in the afternoon to redistribute fluid from the interstitial space to the central circulation, may create a diuresis before bedtime. Other measures may include restricting fluids, or applying compression hosiery to reduce a build up of fluid in the lower limb. Taking diuretics at teatime rather than later in the evening was shown to be effective in the management of nocturnal polyuria in a randomised controlled clinical trial (Reynard et al, 1998). The treatment of choice for Mrs Emery was desmopressin acetate, a vasopressin analogue used to reduce night-time urine production.
Mattiasson et al (2002) studied 151 patients (average age 64.5 years), 86 of whom were treated in an experimental group with desmopressin acetate. The researchers found that nocturnal voids reduced by 43 per cent in this group compared with 12 per cent in the control group. Although this medication is not licensed for use with people over 65 years, it is suggested that it is safe for this age group (Weatherall, 2004; Lose et al, 2003; 2004; Kuo, 2002; Cannon et al, 1999; Asplund et al, 1998). The drug should not be used for patients with cardiac failure.
Desmopressin should be started at a dose of 0.1mg, and then increased every third night until the desired effect on bladder symptoms is achieved. Adverse events, most notably hyponatraemia, are a concern when the drug is prescribed for older people. Special precautions are therefore necessary, such as measuring serum sodium after three days of treatment, after dose adjustments or as any side-effects become apparent.
The patient’s medication should be reviewed to identify other drugs that may cause hyponatraemia, such as anticonvulsants and diuretics. Patients receiving desmopressin therapy must be reminded to curb their fluid intake in the evening to help minimise fluid retention.
Treatment of low nocturnal bladder capacity - Managing low nocturnal bladder capacity will require specific treatment of the underlying cause; for example, treatment of an over-active bladder or infection. For those patients with a mixed aetiology, the predominant category should be treated first.
Nocturia should not be underestimated, as it has a direct and indirect effect on the health and social part of a person’s life. Patients who present to clinicians with symptoms of nocturia should be assessed. If there is evidence of nocturia, comprehensive assessment will determine a category of low nocturnal bladder capacity, nocturnal polyuria, or a combination of both.
Treatment needs to be directed to reduce nocturnal voids and/or nocturnal volume, depending on the initial findings.