Hydration and outcome in older patients admitted to hospital (The HOOP prospective cohort study).

BACKGROUND: Older adults are susceptible to dehydration due to age-related pathophysiological changes. We aimed to investigate the prevalence of hyperosmolar dehydration (HD) in hospitalised older adults, aged ≥65 years, admitted as an emergency and to assess the impact on short-term and long-term outcome. METHODS: This prospective cohort study was performed on older adult participants who were admitted acutely to a large U.K. teaching hospital. Data collected included the Charlson comorbidity index (CCI), national early warning score (NEWS), Canadian Study of Health and Aging (CSHA) clinical frailty scale and Nutrition Risk Screening Tool (NRS) 2002. Admission bloods were used to measure serum osmolality. HD was defined as serum osmolality >300 mOsmol/kg. Participants who were still in hospital 48 h after admission were reviewed, and the same measurements were repeated. RESULTS: A total of 200 participants were recruited at admission to hospital, 37% of whom were dehydrated. Of those dehydrated, 62% were still dehydrated when reviewed at 48 h after admission. Overall, 7% of the participants died in hospital, 79% of whom were dehydrated at admission (P = 0.001). Cox regression analysis adjusted for age, gender, CCI, NEWS, CSHA and NRS demonstrated that participants dehydrated at admission were 6 times more likely to die in hospital than those euhydrated, hazards ratio (HR) 6.04 (1.64-22.25); P = 0.007. CONCLUSIONS: HD is common in hospitalised older adults and is associated with poor outcome. Coordinated efforts are necessary to develop comprehensive hydration assessment tools to implement and monitor a real change in culture and attitude towards hydration in hospitalised older adults.

The pathophysiology of fluid and electrolyte balance in the older adult surgical patient.

BACKGROUND & AIMS: Age-related physiological changes predispose even the healthy older adult to fluid and electrolyte abnormalities which can cause morbidity and mortality. The aim of this narrative review is to highlight key aspects of age-related pathophysiological changes that affect fluid and electrolyte balance in older adults and underpin their importance in the perioperative period. METHODS: The Web of Science, MEDLINE, PubMed and Google Scholar databases were searched using key terms for relevant studies published in English on fluid balance in older adults during the 15 years preceding June 2013. Randomised controlled trials and large cohort studies were sought; other studies were used when these were not available. The bibliographies of extracted papers were also searched for relevant articles. RESULTS: Older adults are susceptible to dehydration and electrolyte abnormalities, with causes ranging from physical disability restricting access to fluid intake to iatrogenic causes including polypharmacy and unmonitored diuretic usage. Renal senescence, as well as physical and mental decline, increase this susceptibility. Older adults are also predisposed to water retention and related electrolyte abnormalities, exacerbated at times of physiological stress. Positive fluid balance has been shown to be an independent risk factor for morbidity and mortality in critically ill patients with acute kidney injury. CONCLUSIONS: Age-related pathophysiological changes in the handling of fluid and electrolytes make older adults undergoing surgery a high-risk group and an understanding of these changes will enable better management of fluid and electrolyte therapy in the older adult.

The influence of serial feeding of drinks at different temperatures on thermoregulatory responses during cycling.

In this study, we examined thermoregulatory responses to ingestion of separate aliquots of drinks at different temperatures during low-intensity exercise in conditions of moderate heat stress. Eight men cycled at 50% (s = 3) of their peak oxygen uptake (VO2peak) for 90 min (dry bulb temperature: 25.3 degrees C, s = 0.5; relative humidity: 60%, s = 5). Four 400-ml aliquots of flavoured water at 10 degrees C (cold), 37 degrees C (warm) or 50 degrees C (hot) were ingested after 30, 45, 60, and 75 min of exercise. Immediately after the 90 min of exercise, participants cycled at 95% VO2peak to exhaustion to assess exercise capacity. There were no differences between trials in rectal temperature at the end of the 90 min of exercise (cold: 38.11 degrees C, s = 0.30; warm: 38.10 degrees C, s = 0.33; hot: 38.21 degrees C, s = 0.30; P = 0.765). Mean skin temperature between 30 and 90 min tended to be influenced by drink temperature (cold: 34.49 degrees C, s = 0.64; warm: 34.53 degrees C, s = 0.69; hot: 34.71 degrees C, s = 0.48; P = 0.091). Mean heart rate from 30 to 90 min was higher in the hot trial (129 beats . min(-1), s = 7; P < 0.05) than on the cold (124 beats . min(-1), s = 9) and warm trials (126 beats . min(-1), s = 8). Ratings of thermal sensation were higher on the hot trial than on the cold trial at 35 and 50 min (P < 0.05). Exercise capacity was similar between trials (P = 0.963). The heat load and debt induced by periodic drinking resulted in similar body temperatures during low-intensity exercise in conditions of moderate heat stress due to appropriate thermoregulatory reflexes.

Heat and cold : what does the environment do to the marathon runner?

The marathon poses a considerable physical challenge for athletes of all levels. When combined with high heat and humidity, not only is performance potentially compromised, but health and well-being are also at risk. There are well recognised effects of heat and hydration status on the cardiovascular and thermoregulatory systems that can account for the decreased performance and increased sensation of effort that are experienced when competing in the heat. Elevated exercise heart rate and core temperature at the same absolute exercise intensity are commonly reported. Dehydration occurring during exercise in the heat and results in reductions in stroke volume, cardiac output and blood pressure, as well as a marked decline in blood flow to the working muscles. Recent work suggests that hyperthermia may have a direct affect on the CNS and the brain may contribute to fatigue during prolonged exercise in a warm environment. At present, evidence supports a significant role of catecholaminergic neurotransmission, but there are a number of metabolic and circulatory perturbations occurring within the brain that may also be important in the fatigue process.

Comparison of water turnover rates in young swimmers in training and age-matched non-training individuals.

Total body water (TBW) and water turnover rates (WTR) of 8 competitive swimmers (SW) and 6 age-matched non-training individuals (CON) were determined using deuterium oxide dilution and elimination. During the 7-day study, individuals in the SW group trained 9 times, swimming on average 42.4 km, while the CON group did no regular exercise. Water temperature in the swimming pool was between 26 and 29 degrees C during training sessions. Body mass at the beginning and end of the study period remained essentially the same in the SW (67.8+/- 6.3 kg) and CON (61.1 +/- 8.5 kg) groups. Mean +/- SD TBW of the SW (38.7+/- 5.6 L) was similar to that of the CON (37.5 +/- 8.0 L). Mean WTR was faster in the SW (54 +/- 18 ml x kg x day(- 1) than the CON (28+/- 21 ml x kg x day(-1)). Mean daily urine output was similar in the SW (14 +/- 5 ml x kg x day(-1)) and CON (14+/- 3 ml x kg x day(-1)). Calculated non-renal daily water loss was faster in the SW (41 +/- 21 ml x kg x day(-1)) than the CON (13 +/- 20 ml x kg x day(-1)). This study demonstrates that WTR are faster in young swimmers who exercise strenuously in cool water than in non-training individuals and that the difference was due to the approximately 3-times greater non-renal water losses that the exercising group incurred. This suggests that exercise-induced increases in sweat rates are a major factor in water loss in swimmers training in cool water.

Dietary supplements.

For the athlete training hard, nutritional supplements are often seen as promoting adaptations to training, allowing more consistent and intensive training by promoting recovery between training sessions, reducing interruptions to training because of illness or injury, and enhancing competitive performance. Surveys show that the prevalence of supplement use is widespread among sportsmen and women, but the use of few of these products is supported by a sound research base and some may even be harmful to the athlete. Special sports foods, including energy bars and sports drinks, have a real role to play, and some protein supplements and meal replacements may also be useful in some circumstances. Where there is a demonstrated deficiency of an essential nutrient, an increased intake from food or from supplementation may help, but many athletes ignore the need for caution in supplement use and take supplements in doses that are not necessary or may even be harmful. Some supplements do offer the prospect of improved performance; these include creatine, caffeine, bicarbonate and, perhaps, a very few others. There is no evidence that prohormones such as androstenedione are effective in enhancing muscle mass or strength, and these prohormones may result in negative health consequences, as well as positive drug tests. Contamination of supplements that may cause an athlete to fail a doping test is widespread.

PASSCLAIM - Physical performance and fitness.

OBJECTIVE: The aim of the EC Concerted Action PASSCLAIM was to develop a set of methods and procedures for assessing the scientific support for function-enhancing and health-related claims for foods and food components. This paper presents a critical review of the existing methods to evaluate the different aspects of physical performance and fitness needed to support claims on foods and food ingredients intended to enhance specific physiological functions. DESIGN AND RESULTS: Based on an inventory of labelling claims on available sport nutrition products, seven physiological functions in the field of physical performance and fitness were identified: 1) strength and power, 2) endurance, energy supply and recovery, 3) hydration/re-hydration, 4) flexibility, 5) tissue growth, 6) free radical scavenger capacity and 7) immune function. For each function the existing methodology was reviewed critically and judged on suitability to generate scientific support for physiological function claims on foods. CONCLUSIONS: A database of methods including advantages and disadvantages of use has been generated for considering the scientific support of claims on foods and food ingredients relating to physical performance and fitness. It will contribute to the formulations of guidelines for assessing the scientific support of enhanced function or reduced disease risk claims on foods.