Heat illness. II. Pathogenesis.

The effects of elevated temperatures and the time-temperature combinations for irreversible damage are outlined. Coagulation abnormalities and the effects on the kidney, liver, heart, brain and serum enzymes, the role of electrolytes and water, including salt deficiency and the controversial question of salt supplements, potassium deficiency, changes in other electrolytes and sweat solutes, and rhabdomyolysis (including a discussion of experimental work on dogs) are reviewed. The section ends with a discussion of the effects of drugs and an account of a recent fatal case of heat stroke which may have been triggered by chlorpromazine therapy.     

Heat illness. I. Epidemiology.

Reliable information on the epidemiology of heat illness has come, until recently, mainly from the armed forces and, to a lesser extent, from some industries and civil communities. Data from the records of the British Army, Royal Navy, Royal Air Force, Indian Armed Forces, U.S. Army and forces engaged in the Arab-Israeli wars, from the South African gold mining corporations and Persian Gulf oil tankers, and from civilian communities, mainly in the U.S.A., are reviewed and discussed with particular reference to the classification of heat illness and definition of the terms used, and the effects on acclimatized and non-acclimatized personnel and on other sections of the civilian communities most at risk, i.e. the old and very young. This section concludes with an outline of the classification of acute heat illnesses from 1899 to the eighth revision of the WHO International Classification of Diseases in 1967.     

Heat illness

A 17-year-old girl collapsed during a field hockey practice on a hot August afternoon, apparently suffering from heat illness, which is responsible for about 5,000 deaths annually. A panel of experts explores this girl's case, discusses heat illness in general, and makes recommendations about diagnosis, prevention, and treatment.     

急性受热及热适应对机体免疫系统的影响

雄性ＳＤ大鼠随机分为５组：２５℃对照组，３７℃每天２ｈ共７天热适应组，４２℃分别受热３０ｍｉｎ、６０ｍｉｎ，９０ｍｉｎ的３个热处理组。检测全血淋巴细胞转化率、α－醋酸萘酯酶活性、腹腔巨噬细胞活性和吞噬功能。结果显示：７天热适应组与受热３０ｍｉｎ组即明显降低，随受热时间延长（超过３０ｍｉｎ），巨噬细胞吞噬功能显著降低，不能形成吞噬峰。７天热适应组与受热３０ｍｉｎ组用ＰＨＡ刺激全血淋巴细胞转化的刺激指数比对照组稍高，但差异不明显（Ｐ＞０．０５），而６０ｍｉｎ和９０ｍｉｎ受热却使该指数显著下降（Ｐ分别为０．００３１和０．００６３）。α－醋酸萘酯酶除热适应组降低外，其余各组无明显变化。结果提示，急性受热时机体免疫系统功能有受抑制倾向。     

耐热锻炼对钙和镁代谢的影响

目的　观察耐热锻炼对钙、镁代谢的影响 ,以探明夏季高温下体力锻炼时补充钙、镁的需要。方法　 2 0名健康青年男子 ,在炎热气候下 (三球温度指数WBGT 31 8℃ )进行 5km越野锻炼 ,2周内锻炼 1 0～ 1 2次。锻炼期前一天和后一天进行高温快步行进标准试验 (WBGT 30 3℃ ,受试者负重 1 6kg ,以速度为 4～5km/h快步行进 90min ,共 7km)。结果　耐热锻炼获得了热习服 ,显著提高了耐热能力。热应激时 ,汗钙、镁浓度分别为 1 35 2mmol/L和 0 36 4mmol/L ;热习服后 ,汗钙、镁浓度分别降低 34 6 %和 36 8% (P <0 0 5 ) ,全天流失量分别减少 1 1 2mg和 1 9 6mg。热应激日粪、尿钙排出量分别为 2 0 5 1mg和 31 4 2mg ,镁分别为2 0 7 6mg和 4 1 82mg;热习服后 ,粪钙、镁都分别减少 2 1 5 % (P <0 0 5 ) ,尿钙增加 1 8 1 % ,而尿镁减少6 6 %。热应激日钙、镁分别负平衡 2 6 1mg和 1 2 4mg ;热习服后热应激日钙负平衡 2 0 5mg ,镁则基本接近平衡。血清钙原处于正常值低限 ,镁尚在正常水平 ,热应激后钙升镁降 (P <0 0 5 ) ;热习服后 ,血清钙降至正常值以下 ,镁也下降 7 7% (P <0 0 5 ) ;高温快步行进标准试验后 ,血清钙下降 ,并与锻炼期前差异有非常显著性 (P <0 0 1 ) ,而实验期间钙、镁摄取量仅为 30     

Heat illness in the U.S. mining industry

BACKGROUND: Heat illness is relatively common in the underground metalliferous mines of South Africa and Australia. Little is known about heat illness in other forms of mining and there have been no studies of heat illness in the US mining industry. METHODS: Mine Safety and Health Administration (MSHA) accident, injury, illness, and employment data were used to study heat illness reported by the US mining industry from January 1, 1983 to December 31, 2001. RESULTS: Five hundred thirty eight cases of heat illness were reported. None of these cases were fatal. Four hundred twenty seven cases (79.4%) occurred in the summer months of June, July, and August. Incidence rates of heat illness in underground mining ranged from 0.00275/10(6) person-hours for coal, to 0.168/10(6) person-hours for metal, rate-ratio = 61.1 (P < 0.001). Incidence rates in surface mining ranged from 0.0265/10(6) person-hours for coal, to 0.0644/10(6) person-hours for stone, rate-ratio = 2.43 (P < 0.001). Incidence rates in mills/preparation plants ranged from 0.0255/10(6) person-hours for coal, to 0.417/10(6) person-hours for stone, rate-ratio = 16.4 (P < 0.001). CONCLUSIONS: Heat illness occurs most frequently in stone mills, metal mills, and underground metal mines. Preventive measures should target the summer months of June, July, and August.     

不同锻炼方式对热习服和脱习服影响的研究

１６名男战士，分成越野锻炼和行军、越野联合锻炼２组，每组８人，２周内分别锻炼１０～１２次（天）．热应激踏车试验显示建立了热习服，联合锻炼比越野锻炼获得的热习服水平高．越野锻炼中断１５天．心血管系统获得的热河服巳经消失；中断３０天，体温调节的热习服也完全消退。但联合锻炼中断３０天，心血管系统对热应激的习服仍有部分保留．     

Methods to Estimate Acclimatization to Urban Heat Island Effects on Heat- and Cold-Related Mortality

Background:

Investigators have examined whether heat mortality risk is increased in neighborhoods subject to the urban heat island (UHI) effect but have not identified degrees of difference in susceptibility to heat and cold between cool and hot areas, which we call acclimatization to the UHI.

Objectives:

We developed methods to examine and quantify the degree of acclimatization to heat- and cold-related mortality in relation to UHI anomalies and applied these methods to London, UK.

Methods:

Case–crossover analyses were undertaken on 1993–2006 mortality data from London UHI decile groups defined by anomalies from the London average of modeled air temperature at a 1-km grid resolution. We estimated how UHI anomalies modified excess mortality on cold and hot days for London overall and displaced a fixed-shape temperature-mortality function (“shifted spline” model). We also compared the observed associations with those expected under no or full acclimatization to the UHI.

Results:

The relative risk of death on hot versus normal days differed very little across UHI decile groups. A 1°C UHI anomaly multiplied the risk of heat death by 1.004 (95% CI: 0.950, 1.061) (interaction rate ratio) compared with the expected value of 1.070 (1.057, 1.082) if there were no acclimatization. The corresponding UHI interaction for cold was 1.020 (0.979, 1.063) versus 1.030 (1.026, 1.034) (actual versus expected under no acclimatization, respectively). Fitted splines for heat shifted little across UHI decile groups, again suggesting acclimatization. For cold, the splines shifted somewhat in the direction of no acclimatization, but did not exclude acclimatization.

Conclusions:

We have proposed two analytical methods for estimating the degree of acclimatization to the heat- and cold-related mortality burdens associated with UHIs. The results for London suggest relatively complete acclimatization to the UHI effect on summer heat–related mortality, but less clear evidence for cold–related mortality.

Citation:

Milojevic A, Armstrong BG, Gasparrini A, Bohnenstengel SI, Barratt B, Wilkinson P. 2016. Methods to estimate acclimatization to urban heat island effects on heat- and cold-related mortality. Environ Health Perspect 124:1016–1022; http://dx.doi.org/10.1289/ehp.1510109     

Heat Acclimatization,Cooling Strategies,and Hydration during an Ultra-Trail in Warm and Humid Conditions

The aim of this study was to assess the history of exertional heat illness (EHI), heat preparation, cooling strategies, heat related symptoms, and hydration during an ultra-endurance running event in a warm and humid environment. This survey-based study was open to all people who participated in one of the three ultra-endurance races of the Grand Raid de la Réunion. Ambient temperature and relative humidity were 18.6 ± 5.7 °C (max = 29.7 °C) and 74 ± 17%, respectively. A total of 3317 runners (56% of the total eligible population) participated in the study. Overall, 78% of the runners declared a history of heat-related symptoms while training or competing, and 1.9% reported a previous diagnosis of EHI. Only 24.3% of study participants living in temperate climates declared having trained in the heat before the races, and 45.1% of all respondents reported a cooling strategy during the races. Three quarter of all participants declared a hydration strategy. The planned hydration volume was 663 ± 240 mL/h. Fifty-nine percent of the runners had enriched their food or drink with sodium during the race. The present study shows that ultra-endurance runners have a wide variability of hydration and heat preparation strategies. Understandings of heat stress repercussions in ultra-endurance running need to be improved by specific field research.     

Heat illness during working and preventive considerations from body fluid homeostasis

The purposes of this review are to show pathophysiological mechanisms for heat illness during working in a hot environment and accordingly provide some preventive considerations from a viewpoint of body fluid homeostasis. The incidence of the heat illness is closely associated with body temperature regulation, which is much affected by body fluid state in humans. Heat generated by contracting muscles during working increases body temperature, which, in a feedback manner, drives heat-dissipation mechanisms of skin blood flow and sweating to prevent a rise in body temperature. However, the impairment of heat-dissipation mechanisms caused by hard work in hot, humid, and dehydrated conditions accelerates the increase in body temperature, and, if not properly treated, leads to heat illness. First, we overviewed thermoregulation during working (exercising) in a hot environment, describe the effects of dehydration on skin blood flow and sweating, and then explained how they contributes to the progression toward heat illness. Second, we described the advantageous effects of blood volume expansion after heat acclimatization on temperature regulation during exercise as well as those of restitution from dehydration by supplementation of carbohydrate-electrolyte solution. Finally, we described that the deteriorated thermoregulation in the elderly is closely associated with the impaired body fluid regulation and that blood volume expansion by exercise training with protein supplementation improves thermoregulation.     

From illness to symbol and symbol to illness.

This paper explores two aspects of the relationship between illness and social symbols: one in which illnesses become symbols; the other, in which symbols become implicated in processes that eventuate in illness. Illness is first discussed as a symbol of social beliefs, attitudes, norms, values, and other social phenomena conceptualized in relation to them. This symbolization is analyzed as it relates to various dimensions of illness that lend themselves to figurative thinking. The paper then turns to processes through which social symbols may generate illness. In this regard, ways in which social symbols may attract people to behavior that puts their health at risk are discussed. The paper concludes with an analysis of how the development of illness may be affected by the relationship between social symbols and somatization.