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BRITISH MEDICAL JOURNAL
Heat waves and dehydration in the elderly Recognising the early warning signs can save lives. The heat wave of 2003 caused an excess mortality of 150% across all age groups, with the largest increase (160-200%) in older people. Excess mortality was high across the whole of western Europe (>50,000 deaths) but highest in big cities such as Paris (1,854 deaths). The death rate was particularly high in cities that were unaccustomed to high temperatures, and cities with warmer climates, such as those in southern France, were spared. This death toll was not followed by a subsequent decline in death rate, which can occur when serious environmental stress causes premature mortality in the frailest people. No universally accepted definition of a heat wave exists. An alarm signal should be given for frail older people when the outdoor temperature exceeds 90 °F (32 °C) for three days or more, which is the most universally accepted definition of a heat wave. Meteorologists predict that global warming will dramatically increase the number of such periods. The main causes of death in unexpected warm periods are dehydration, heat-related morbidity (heat stress, heat exhaustion, hyperthermia, heat syncope, and heat stroke), cardiovascular events, renal failure, complications of delirium, and respiratory diseases. Dehydration with or without concurrent electrolyte disturbances in itself is an important cause of death, but it is also an important factor in most other causes of death, including the vicious cycle of thermoregulatory failure. Older people who live in big cities that are not prepared for heat waves or in areas with clear "heat island" effects - in older buildings without insulation or air conditioning, or with a bedroom located directly under the roof that keeps the heat longer than the rest of the atmosphere - have the highest risk of heat-related morbidity. Frail older people who lived alone, who had low socioeconomic status, pre-existing chronic diseases, and were taking several drugs - such as diuretics, neuroleptics, benzodiazepines, and non-steroidal anti-inflammatory drugs - had the highest heat-related mortality in Italy and France during the 2003 heat wave and in a report from the United States. The key pathophysiological problem is early dehydration. Having extracellular and intracellular water further jeopardises thermoregulation through decreased production of sweat and a reduced direct loss of skin warmth because dehydrated skin provides increased insulation. The severity of dehydration depends more on the relative loss than on the absolute loss of total body water - both intracellular and extracellular. The lower a person's body weight and total body water, the sooner the loss of even a small amount of body water will cause symptoms and signs of dehydration.This is why the reduction in total body water, a common sigh of ageing, is an intrinsic risk factor for dehydration in elderly people. Thirst and the capacity to conserve salt and water reduce with age and are the most important additional risk factors. |
If older adults function independently they fulfil their daily water needs easily through their meals and social drinking. However, a substantial number of older people (up to 25% of people aged 85 and over) drink less than one litre (35 fluid ounces) of fluid a day. The limited capacity of homeostatic mechanisms and the increased dependency on caregivers become important when fluid balance is at risk - for example, in unexpected heat. Nationally, implementation of preventive measures such as electronic alerting systems, education of populations at risk (to dress lightly, take frequent showers, and avoid alcohol), introduction of reflective paving and roofing systems, and increased planting of urban vegetative cover can reduce heat-related mortality. For the individual, recognising frailty, such as in older people who have shown a gradual decline in physical or mental performance during the past year, can help select those who need careful monitoring of fluid balance. This may consist of daily weighing and regular (for example, weekly) measurements of serum sodium and creatinine concentrations. All frail older people should drink two litres of water, milk, or fruit juice every day. In case of weight loss, this should be augmented with fluid equalising the loss of weight in the past 24 hours. Drugs that suppress thirst (such as selective serotonin reuptake inhibitors, angiotensin converting enzyme inhibitors, anti-Parkinson drugs), disturb thermoregulation (such as antipsychotics, beta blockers, and drugs with anticolinergic properties), or disturb fluid balance (such as diuretics and lithium) should be reconsidered, temporarily stopped, or their dose reduced. |
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Jacques Havermans, pharmacist - Basic Pharma Manufacturing BV
TO WHOM IT CONCERNS
For more than 25 years the World Health Organisation (WHO) and The United Nations Children's Fund (UNICEF) have recommended a single formulation of glucose-based Oral Rehydration Salts (ORS) to prevent or treat dehydration from diarrhoea, irrespective of the cause or the age group affected. This product, with a total osmolarity of 311 mOsm/l has proven effective and without apparent adverse effects in worldwide use.
Citric acid is necessary, at a certain level, to achieve a disintegration time which is in accordance with the European Pharmacopoeia for effervescent tablets. In the scientific literature no disadvantages and/or side-effects could be found when using a citrate solution with a concentration of 22 mmol/l.
However, an "improved" formulation in Salamex® has been developed which reduced stool output and reduced the incidence of vomiting. This was achieved by reducing the solution's glucose and salt (NaCI) concentrations to 75 mmmol/l and, as a result, reducing the total osmolarity of the ORS solution to 245 mOsm/l. This ORS product was introduced in 2001.
Especially for children suffering from acute, non-cholera diarrhoea, and for children suffering from cholera, this Salamex® ORS formulation proved to have significant clinical benefits.
Jacques Havermans, pharmacist Basic Pharma Manufacturing bv (Geleen, 22.12.2008)