Lecture 41-42 Case Based Learning PDF

Temperature control • Heat stroke is an uncommon entity, especially in a younger population. Its presentation is often abrupt in the setting of physical exertion or excessive climatic heat. It may present non-specifically but often has a neurological component which may be transient or permanent...

Temperature control • Heat stroke is an uncommon entity, especially in a younger population. Its presentation is often abrupt in the setting of physical exertion or excessive climatic heat. It may present non-specifically but often has a neurological component which may be transient or permanent in the setting of prolonged hyperthermia Fever Heatstroke • If the air is dry and sufficient convection air currents, a person can withstand several hours of air temperature at 130°F • If air is 100% humidified or if the body is in water, the body temperature begins to rise whenever the environmental temperature rises above about 94°F Heatstroke • When the body temperature rises beyond a critical temperature, into the range of 105°F to 108°F, heatstroke is likely to develop. • The symptoms include dizziness, abdominal distress, sometimes accompanied by vomiting, sometimes delirium, and eventually loss of consciousness if the body temperature is not soon decreased. • These symptoms are often exacerbated by a degree of circulatory shock brought on by excessive loss of fluid and electrolytes in the sweat. Heatstroke Treatment • Hyperpyrexia is also exceedingly damaging to the body tissues, especially the brain. • Few minutes of very high body temperature can sometimes be fatal. • immediate treatment: placing the person in a cold-water bath, a muscle relaxant may be administered in some cases, or sponge or spray cooling of the skin along with blowing cool air over the moist skin may be more effective and more practical for rapidly decreasing the body core temperature. The pathological findings in a person who dies of hyperpyrexia are local hemorrhages and parenchymatous degeneration of cells throughout the entire body Case 2 • Hypothermia is defined as a human body temperature below 95°F (35°C). Onset occurs when heat loss from the body exceeds heat generated by normal metabolism and/or special means of raising the body temperature, such as shivering. Heat is lost by conduction (usually in water), convection (in the air), and by evaporation in the air from wet clothing or the surface of the body to the environment. Most cases of hypothermia are accidental in unsuspecting victims Exposure of the Body to Extreme Cold • Unless treated immediately, a person exposed to ice water for 20 to 30 minutes ordinarily dies because of heart standstill or heart fibrillation • The internal body temperature will have fallen to about 77°F. • If warmed rapidly by the application of external heat, the person’s life can often be saved. Part of the reason for this diminished temperature regulation is that the rate of chemical heat production in each cell is depressed almost twofold for each 10°F decrease in body temperature. Chemical heat production in each cell is depressed almost twofold for each 10°F Frostbite • body is exposed to extremely low temperatures; phenomenon called frostbite • especially in the lobes of the ears and in the digits of the hands and feet • Gangrene often follows thawing, and the frostbitten areas must be removed surgically. • When the temperature of tissues falls almost to freezing, the smooth muscle in the vascular wall becomes paralyzed because of the cold, and sudden vasodilation occurs, often manifested by a flush of the skin. • This mechanism helps prevent frostbite by delivering warm blood to the skin. • This mechanism is far less developed in humans than in most animals that live in the cold all the time. Artificial Hypothermia • decrease the temperature of a person by first administering a strong sedative to depress the reactivity of the hypothalamic temperature controller and then cooling the person with ice or cooling blankets until the temperature falls. • The temperature can then be maintained below 90°F for several days to a week or more by continual sprinkling of cool water or alcohol on the body • Such artificial cooling has been used during heart surgery so that the heart can be stopped artificially for many minutes at a time Cooling to this extent does not cause tissue damage, but it does slow the heart and greatly depresses cell metabolism so that the body’s cells can survive 30 minutes to more than 1 hour without blood flow during the surgical procedure. Prolonged or chronic fatigue • The fatigue's duration can be described as recent (onset within 1 month before presentation), prolonged (lasting 1–6 months) or chronic (lasting > 6 months). For patients with recent or prolonged fatigue, a history and physical examination often help to identify the cause, but we have found that these are often less helpful for distinguishing the cause of chronic fatigue. Recovery of Muscle Glycogen • Recovery from exhaustive muscle glycogen depletion is not a simple matter (1) in people who consume a high-carbohydrate diet; (2) in people who consume a high-fat, high-protein diet; and (3) in people who consume no food. Note that for persons who consume a high-carbohydrate diet, full recovery occurs in about 2 days Nutrients Used during Muscle Activity • Not all the energy from carbohydrates comes from the stored muscle glycogen. In fact, almost as much glycogen is stored in the liver as in the muscles, and this glycogen can be released into the blood in the form of glucose and then taken up by the muscles as an energy source. • glucose solutions given to an athlete to drink during the course of an athletic event can provide as much as 30% to 40% of the energy required during prolonged events such as marathon races. Effect of Athletic Training on Muscles and Muscle Performance The upper curve the approximate percentage increase in strength that can be achieved in a previously untrained young person by this resistive training program, demonstrating that the muscle strength increases about 30% during the first 6 to 8 weeks but almost plateaus after that time. Along with this increase in strength is an approximately equal percentage increase in muscle mass, which is called muscle hypertrophy. • In old age, many people become so sedentary that their muscles atrophy tremendously. In these cases, however, muscle training may increase muscle strength more than 100%. • Some people have considerably more fast-twitch than slow-twitch fibers, and others have more slow-twitch fibers; • this factor could determine to some extent the athletic capabilities of different individuals. • Athletic training may change the relative proportions of fast-twitch and slow-twitch fibers as much as 10%. • However, the relative proportions of fast-twitch and slow-twitch fibers seem to be determined to a great extent by genetic inheritance, which in turn helps determine which area of athletics is most suited to each person: some people appear to be born to be marathoners, whereas others are born to be sprinters and jumpers. Limits of Pulmonary Ventilation Case 4- Supplement safety is never guaranteed • • • Supplements • First, some persons believe that caffeine increases athletic performance. In one experiment performed by a marathon runner, running time for the marathon was improved by 7% through judicious use of caffeine in amounts similar to those found in one to three cups of coffee. Yet experiments by other investigators have failed to confirm any advantage, thus leaving this issue in doubt. • male sex hormones (androgens) or other anabolic steroids to increase muscle strength undoubtedly can increase athletic performance under some conditions, especially in women and even in men. However, anabolic steroids also greatly increase the risk of cardiovascular disease because they often cause hypertension, decreased high-density blood lipoproteins, and increased low-density lipoproteins, all of which promote heart attacks and strokes. Case 5: Body Fitness Prolongs Life • Multiple studies have shown that people who maintain appropriate body fitness, using judicious regimens of exercise and weight control, have the additional benefit of prolonged life. Especially between the ages of 50 and 70 years, studies have shown mortality to be three times less in the most fit people than in the least fit people. Why does body fitness prolong life? • Body fitness and weight control greatly reduce cardiovascular disease. • (1) maintenance of moderately lower blood pressure and • (2) reduced blood cholesterol and low-density lipoprotein along with increased high-density lipoprotein. • As pointed out earlier, these changes all work together to reduce the number of heart attacks, brain strokes, and kidney disease. Why does body fitness prolong life? • The athletically fit person has more bodily reserves to call on when he or she does become sick. • For example, an 80-year-old, nonfit person may have a respiratory system that limits oxygen delivery to the tissues to no more than 1 L/min; this means a respiratory reserve of no more than 3-fold to 4-fold. • However, an athletically fit old person may have twice as much reserve. This extra reserve is especially important in preserving life when the older person experiences conditions such as pneumonia that can rapidly require all available respiratory reserve. • In addition, the ability to increase cardiac output in times of need (the “cardiac reserve”) is often 50% greater in the athletically fit old person than in the nonfit old person. Why does body fitness prolong life? • Exercise and overall body fitness also reduce the risk for several chronic metabolic disorders such as insulin resistance and type 2 diabetes • Improved body fitness also reduces the risk for several types of cancers, including breast, prostate, and colon cancer