By O. Mortis. Southwestern University.
The Cushing response (described by famous neurosurgeon flex when the plantar surface is stimulated discount claritin 10 mg amex. Harvey Cushing) consists of the development of hyperten- The neurophysiological details of how the deficit in sion cheap 10 mg claritin with visa, bradycardia, and apnea in patients with increased in- corticospinal input actually produces these commonly tracranial pressure most often a result of tumors or other le- encountered abnormalities in muscle tone and reflex sions, such as hemorrhage, that compress the brain. A current theory is pressure is transmitted downward to the brainstem and dis- that the disturbance of central control reduces the torts the medulla, where the centers for blood pressure, threshold of the stretch reflex but does not alter its gain. Correct interpre- References tation of these abnormalities in vital signs permits begin- Lance JW. The control of muscle tone, reflexes, and move- ning treatments that reduce intracranial pressure. Quantitative relations an artificial respirator, and then instituting hyperventilation between hypertonia and stretch reflex threshold in spastic to lower the blood PCO2 to produce cerebral vasoconstric- hemiparesis. Another autonomic reaction from the CNS that is uti- CASE STUDY FOR CHAPTER 6 lized daily in hospitals is the response of fetal heart rate Autonomic Dysfunction as a Result of CNS Disease to compression of the head during labor. During uterine A 30-year-old patient came to the hospital emergency contractions, the fetal head is temporarily compressed. Previously he the cranium are not yet fused, the pressure of the con- had experienced only mild, infrequent tension traction is transmitted to the brain. Because of the nism of cardiac slowing as cited for the Cushing re- intensity of this new headache, he is treated with in- sponse is presumed to cause the temporary bradycardia. Additional factors, such as umbilical cord com- consciousness declines to the point of responding only pression, may also produce patterns of slowing outside to painful stimuli. The central nervous system and cardiovascular the blood is thought to be a ruptured cerebral artery control in health and disease.
The diagnostic odds ratio (DOR) can be added 10mg claritin, but better not alone cheap 10mg claritin mastercard, as a same odds ratio can relate to different combinations of sensitivity and specificity. Main outcome measures should be reported with their 95% confidence intervals (CI). When setting inclusion criteria, most reviewers will try to define a more or less homogeneous set of studies. The reality, however, is that even then most diagnostic reviews suffer from considerable heterogeneity. When different studies have largely different results, this can be because of either random error or heterogeneity. To test for homogeneity of sensitivity and specificity, a 2 test or an extension of Fisher’s exact test for small studies35 can be used. This may offer some guidance, although the power of this test tends to be low. A basic but very informative method when searching for heterogeneity is to produce a graph in which the individual study outcomes are plotted, together with their 95% confidence intervals (Figure 8. Searching for the presence of an (implicit) cut-off point effect Estimates of diagnostic accuracy differ if not all studies use the same cut- off point for a positive test result or for the reference standard. The interpretation of test results often depends on human factors (for example radiology, pathology, etc. In such cases different studies may use a different implicit cut-off point. Variation in the parameters of accuracy may be partly due to variation in cut-off points. One can test for the presence of a cut-off point effect between studies by calculating a Spearman correlation coefficient between the sensitivity and the specificity of all included studies.
This conversion may occur almost immediately order claritin 10mg on-line, as with energy used for active transport or heat produced as a by-product of muscular activity buy claritin 10 mg amex. Other energy is con- verted to heat only after a delay, as when the energy used FIGURE 29. In addition, some of the energy released by his metabolic Metabolic Rate and Sites of Heat Production at Rest. In a resting and fasting young adult man it is about 45 2 2 W/m (81 W or 70 kcal/hr for 1. As a rate of heat storage in the body, manifested as changes in by-product of their metabolic processes, these organs pro- tissue temperatures. E, R, C, K, and W are positive if they represent energy Factors other than body size that affect metabolism at losses from the body and negative if they represent energy rest include age and sex (Fig. The ratio of metabolic rate to surface area is high- temperature neither rises nor falls. When the body is not est in infancy and declines with age, most rapidly in child- in heat balance, its mean tissue temperature increases if S hood and adolescence and more slowly thereafter. This situation have high metabolic rates in relation to surface area because commonly lasts only until the body’s responses to the tem- of the energy used to synthesize the fats, proteins, and other perature changes are sufficient to restore balance. Similarly, a ever, if the thermal stress is too great for the thermoregu- woman’s metabolic rate increases during pregnancy to sup- latory system to restore balance, the body will continue to ply the energy needed for the growth of the fetus. However, gain or lose heat until either the stress diminishes suffi- a nonpregnant woman’s metabolic rate is 5 to 10% lower ciently or the animal dies. Because so many fac- Relative Masses and Metabolic Heat tors affect metabolism at rest, metabolic rate is often meas- TABLE 29. Metabolic rate measured under these % of conditions is called basal metabolic rate (BMR). The com- Heat Production monly accepted conditions for measuring BMR are that the % of person must have fasted for 12 hours; the measurement Body Mass Rest Exercise must be made in the morning after a good night’s sleep, be- Brain 2 16 1 ginning after the person has rested quietly for at least 30 Trunk viscera 34 56 8 minutes; and the air temperature must be comfortable, Muscle and skin 56 18 90 about 25 C (77 F).