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PubMed2005

Pernio in pediatrics.

Pernio, or chilblains, is a localized inflammatory lesion of the skin resulting from an abnormal response to cold. Five cases were seen among adolescent female patients who presented to our rheumatology service in a pediatric tertiary care center in the winter of 2003 to 2004. All 5 patients were thin (BMI of <25th percentile) and had either toes or fingers that were affected. For each, laboratory evaluation results were unremarkable, including negative antinuclear antibody profile results. Symptomatic treatment, with or without medication, was recommended. Pernio most commonly occurs among young women but may occur among older individuals or among children. Because pernio develops among susceptible individuals who are exposed to nonfreezing cold, the lesions usually begin in the fall or winter and disappear in the spring or early summer. Acute pernio may develop 12 to 24 hours after exposure to the cold. Single or multiple erythematous, purplish, edematous lesions appear, accompanied by intense pain, itching, or burning. Chronic pernio occurs with repeated exposure to the cold and the persistence of lesions. In an acute exacerbation, the major differential diagnosis alternative would be Raynaud's phenomenon, which consists of sharply demarcated cutaneous pallor and cyanosis, followed by erythema, of far shorter duration (hours rather than days). Frostbite is freezing of tissue, with resultant tissue necrosis. Several conditions have been described as predisposing subjects to pernio, including the presence of cryoproteins, excessive cold exposure, and anorexia nervosa among children and systemic lupus erythematosus and antiphospholipid antibodies among adults. It is important, therefore, when evaluating a patient with pernio, both to exclude an underlying diagnosis and to determine whether additional testing is necessary. The lesions of acute pernio are usually self-limited but may lead to recurrent disease. The involved limb should be cleaned and dried, and rewarming should occur. Prevention is the best form of therapy, and cold exposure should be minimized after an initial insult. The prognosis for properly treated pernio is excellent. Nifedipine, which produces vasodilation, has been demonstrated to be effective in reducing pain, facilitating healing, and preventing new lesions of pernio. We think that the 5 cases seen in our rheumatology clinic represent an increase, compared with prior years; the dermatology clinic at the University of Colorado reported a series of 8 children treated during a 10-year period. The reasons for the possible increase are likely multifactorial, with cold climate, a vulnerable population with thin body habitus, and cold exposure all being contributing causes. Of note, the quality of cold in Colorado is quite dry; however, the winter of 2003 to 2004 was not particularly colder or drier than prior years. All patients were very thin, and thin body habitus may be associated with increased cutaneous vasoreactivity. It is also unclear how these cases of pernio may reflect that winter's fashion trends (2 patients reported wearing sandals in winter). General pediatricians, particularly those who practice in colder climates, should be aware of the presentation and treatment of pernio in childhood.

Acute Disease↗
PubMed1991

Physiology of exercise in the cold.

Recreational and job requirements have increased the incidence in which humans exercise in cold environment. Understanding the physiological responses while exposed to cold entails knowledge of how exercise and cold interact on metabolic, cardiopulmonary, muscle and thermal aspects of human performance. Where possible, distinction are made between responses in cold air and cold water. While there is no consensus for diets most appropriate for working cold exposures, the evidence is strong that adequate amounts of carbohydrate are necessary. Carbohydrate loading appears to be efficacious, as it is for other athletic endeavours. Contrary to conventional wisdom, the combination of exercise and cold exposure does not act synergistically to enhance metabolism of fats. Free fatty acid (FFA) levels are not higher, and may be lower, with exercise in cold air or water when compared to corresponding warmer conditions. Glycerol, a good indicator of lipid mobilisation, is likewise reduced in the cold, suggesting impaired mobilisation from adipose tissue. Catecholamines, which promote lipolysis, are higher during exercise in cold air and water, indicating that the reduced lipid metabolism is not due to a lack of adequate hormonal stimulation. It is proposed that cold-induced vasoconstriction of peripheral adipose tissue may account, in part, for the decrease in lipid mobilisation. The respiratory exchange ratio (RER) is often similar for exercise conducted in warm and cold climates, suggesting FFA utilisation is equivalent between warm and cold exposures. The fractional portion of oxygen consumption (VO2) used for FFA combustion may decrease slightly during exercise in the cold. This decrease may be related to a relative decrease in oxygen delivery (i.e. muscle blood flow) or to impaired lipid mobilisation. Venous glucose is not substantially altered during exercise in the cold, but lactate levels are generally higher than with work in milder conditions. The time lag between production of lactate within the muscle and its release into the venous circulation may be increased by cold exposure. Minute ventilation is substantially increased upon initial exposure to cold, and a relative hyperventilation may persist throughout exercise. With prolonged exercise, though, ventilation may return to values comparable to exercise in warmer conditions. Exercise VO2 is generally higher in the cold, but the difference between warm and cold environments becomes less as workload increases. Increases in oxygen uptake may be due to persistence of shivering during exercise, to an increase in muscle tonus in the absence of overshivering, or to nonshivering thermogenesis. Heart rate is often, but not always, lower during exercise in the cold.(ABSTRACT TRUNCATED AT 400 WORDS)

Body Temperature Regulation↗
PubMed2004

Tissue and external insulation estimates and their effects on prediction of energy requirements and of heat stress.

Published data were used to develop improved equations to predict tissue insulation (TI) and external insulation (EI) and their effects on maintenance requirements of Holstein cattle. These are used to calculate lower critical temperature (LCT), energy cost of exposure to temperatures below LCT, and excess heat accumulating in the body at temperatures above LCT. The National Research Council classifies TI by age groups and body condition score; and in the EI equation air velocity effects are linear and coat insulation values are derived from beef animals in cold climates. These lead to low LCT values, which are not compatible with known effects of environment on the performance of Holsteins in warm climates. Equations were developed to present TI as a function of body weight, improving prediction of TI for animals of similar age but differing in body weight. An equation was developed to predict rate of decrease of TI at ambient temperatures above LCT. Nonlinear equations were developed that account for wind effects as boundary layer insulation effects dependent on body weight and air velocity. Published data were used to develop adjustments for hair coat effects on EI in Holstein cows. While by NRC equations, wind has negligible effects on heat loss, the recalculated effects of air velocity on heat loss were consistent with published effects of forced ventilation on the responses of the Holstein cow. The derived LCT was higher by 10 to 20 degrees C than that calculated by NRC (2001) and accounted for known Holstein performance in temperate and warm climates. These equations pointed to tentative significant effects of cold (-10 degrees C) on energy requirements (7 Mcal/d) further increased by 1 m/s wind (15 Mcal/d), even in high-producing cows. Needs for increased heat dissipation and estimating heat stress development at ambient temperatures above the LCT are predicted. These equations can be used to revise NRC equations for heat exchange.

Aging↗
PubMed1996

Energy expenditure variations in soldiers performing military activities under cold and hot climate conditions.

This study assessed the energetic status of soldiers exposed to intense physical activities in cold and warm weather. Thirty subjects participated in a two-phase study group A (n = 18) in the winter phase and group B (n = 12) in the summer phase. Energy expenditure (EE) was measured by the doubly labeled water technique; after a single, oral dosing of 2H(2)18O, daily urine samples were collected for 12 successive days. Energy intake (EI) was assessed from detailed food records analyzed by computerized food charts. Energy balance was calculated as the difference between EI and EE for each subject. Mean (+/- SE) daily EE was 4,281 +/- 170 and 3,937 +/- 159 kcal/day for the winter and summer groups, respectively. Daily EI was 2,792 +/- 124 kcal/day in group A and almost identical in group B. A negative energy balance of 1,422 +/- 163 kcal/day and 924 +/- 232 kcal/day (not significant) was calculated for groups A and B, respectively. Energy expenditure is primarily determined by the level of activity rather than by climate conditions; EI is insufficient to offset the high energy requirements under these conditions.

Adult↗
PubMed1995

Body temperature, rate of biosynthesis, and evolution of genome size.

An optimality model relating the rate of biosynthesis to body temperature and gene duplication is presented to account for several observed patterns of genome size variation. The model predicts (1) that poikilotherms living in a warm climate should have a smaller genome than poikilotherms living in a cold climate, (2) that homeotherms should have a small genome as well as a small variation in genome size relative to their poikilothermic ancestors, (3) that cold geological periods should favor the evolution of poikilotherms with a large genome and that warm geological periods should do the opposite, and (4) that poikilotherms with a small genome should be more sensitive to changes in temperature than poikilotherms with a large genome. The model also offers two explanations for the empirically documented trend that organisms with a large cell volume have larger genomes than those with a small cell volume. Relevant empirical evidence is summarized to support these predictions.

Animals↗
PubMed1983

Climatic conditions and migration: an econometric inquiry.

"This paper has examined the impact of climate on migration. It has compared the results that are obtained when various indicators of climatic conditions, both those which have been used in the literature and those which have not, are included in a regression used to explain migration behavior. The results suggest that individuals do indeed consider climatic conditions in different areas when deciding where to live; people generally prefer areas which have moderate climates to areas which have either extremely hot or extremely cold climates. The results also indicate that the climate variables which yield the best results are generally those which have not been used in the literature." The study is based on U.S. data concerning in-migration to 36 SMSAs between 1960 and 1970.

Americas↗
PubMed1986

A controlled study on the effect of treatment with cromolyn sodium pressurized aerosol on bronchial reactivity in patients with asthma.

The effect of cromolyn sodium (CS) pressurized aerosol on bronchial hyperreactivity was assessed by comparison with placebo in a double-blind crossover study of 14 adult patients with clinically stable asthma. The trial was performed in a cold climate during the pollen-free winter months and the patient's risk of exposure to clinically relevant allergens was judged to be low. The dose was two puffs, each of 1 mg CS or placebo, four times daily over two successive 4-week periods, the order of treatment being decided by random allocation. No significant difference between treatments was observed in bronchial reactivity to histamine, determined as PC15. There was no difference between treatments with regard to symptoms, which were slight, or daily peak expiratory flow recordings, which showed minimal circadian variation. The results suggest that, although prolonged treatment with CS may decrease bronchial reactivity by reducing airway inflammation secondary to the assault of allergic stimuli, the drug probably has little or no effect on the basal bronchial reactivity in asthma.

Adolescent↗