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APS Physiology in Medicine reviews, 1998-2011

Review articles explicating basic science for clinicians. From the American Physiological Society.

Physiology in Medicine: 2007-2011

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Afshar, M., M. Raju, et al. (2011). "Narrative review: tetanus-a health threat after natural disasters in developing countries." Annals of Internal Medicine 154(5): 329-335.

Tetanus is an expected complication when disasters strike in developing countries, where tetanus immunization coverage is often low or nonexistent. Collapsing structures and swirling debris inflict numerous crush injuries, fractures, and serious wounds. Clostridium tetani infects wounds contaminated with dirt, feces, or saliva and releases neurotoxins that may cause fatal disease. Clusters of infections have recently occurred after tsunamis and earthquakes in Indonesia, Kashmir, and Haiti. The emergency response to clusters of tetanus infections in developing countries after a natural disaster requires a multidisciplinary approach in the absence of an intensive care unit, readily available resources, and a functioning cold-chain system. It is essential that injured people receive immediate surgical and medical care of contaminated, open wounds with immunization and immunoglobulin therapy. Successful treatment of tetanus depends on prompt diagnosis of clinical tetanus, treatment to ensure neutralization of circulating toxin and elimination of C. tetani infection, control of spasms and convulsions, maintenance of the airway, and management of respiratory failure and autonomic dysfunction.

Druey, K. M. and P. R. Greipp (2010). "Narrative review: the systemic capillary leak syndrome." Annals of Internal Medicine 153(2): 90-98.

The systemic capillary leak syndrome (SCLS) is a rare disease of reversible plasma extravasation and vascular collapse accompanied by hemoconcentration and hypoalbuminemia. Its cause is unknown, although it is believed to be a manifestation of transient endothelial dysfunction due to endothelial contraction, apoptosis, injury, or a combination of these. Fewer than 150 cases of SCLS have been reported, but the condition is probably underrecognized because of its nonspecific symptoms and signs and high mortality rate. Patients experience shock and massive edema, often after a nonspecific prodrome of weakness, fatigue, and myalgias, and are at risk for ischemia-induced organ failure, rhabdomyolysis and muscle compartment syndromes, and venous thromboembolism. Shock and edema reverse almost as quickly as they begin, at which time patients are at risk for death from flash pulmonary edema during rapid fluid remobilization. Diagnosis is made clinically and by exclusion of other diseases that cause similar symptoms and signs, most notably sepsis, anaphylaxis, and angioedema. Acute episodes are treated with vasopressor therapy and judicious fluid replacement, possibly with colloid solutions for their osmotic effects, to prevent the sequelae of underperfusion. Between episodes, patients may be treated with theophylline and terbutaline, which clinical experience suggests may reduce the severity and frequency of acute episodes. Prognosis is uncertain, but patients who survive an initial severe SCLS episode are estimated to have a 10-year survival rate greater than 70%. Much remains to be learned about SCLS, and clinicians should consider the diagnosis in patients with unexplained edema, increased hematocrit, and hypotension. [References: 90]

Flaherty, K. T. (2010). "Narrative review: BRAF opens the door for therapeutic advances in melanoma." Annals of Internal Medicine 153(9): 587-591.

Patients with metastatic melanoma have a poor prognosis and limited treatment options. In about one half of analyzed patients with metastatic melanoma, a mutated signal transduction molecule has been identified: v-raf murine sarcoma viral oncogene homolog B1 (BRAF). This molecule is part of an intracellular signaling cascade and may play a role in many different types of cancer. This article provides an overview of the current treatment options for metastatic melanoma and describes the pathophysiology underlying the development of therapies based on inhibition of BRAF. It summarizes findings of phase 1 and phase 2 studies of BRAF inhibitor therapy primarily in patients with metastatic melanoma, who have shown objective response rates of 70% to 80%. However, initial responses have not been sustained, with a median time to relapse of approximately 9 months. Clinicians should be aware of phase 3 trials of these agents and trials combining these therapies with other novel therapies because, at a minimum, BRAF inhibitors seem to be valuable as palliative therapy for metastatic melanoma.

Kelesidis, T., I. Kelesidis, et al. (2010). "Narrative review: the role of leptin in human physiology: emerging clinical applications." Annals of Internal Medicine 152(2): 93-100.

Leptin is a hormone secreted by adipose tissue in direct proportion to amount of body fat. The circulating leptin levels serve as a gauge of energy stores, thereby directing the regulation of energy homeostasis, neuroendocrine function, and metabolism. Persons with congenital deficiency are obese, and treatment with leptin results in dramatic weight loss through decreased food intake and possible increased energy expenditure. However, most obese persons are resistant to the weight-reducing effects of leptin. Recent studies suggest that leptin is physiologically more important as an indicator of energy deficiency, rather than energy excess, and may mediate adaptation by driving increased food intake and directing neuroendocrine function to converse energy, such as inducing hypothalamic hypogonadism to prevent fertilization. Current studies investigate the role of leptin in weight-loss management because persons who have recently lost weight have relative leptin deficiency that may drive them to regain weight. Leptin deficiency is also evident in patients with diet- or exercise-induced hypothalamic amenorrhea and lipoatrophy. Replacement of leptin in physiologic doses restores ovulatory menstruation in women with hypothalamic amenorrhea and improves metabolic dysfunction in patients with lipoatrophy, including lipoatrophy associated with HIV or highly active antiretroviral therapy. The applications of leptin continue to grow and will hopefully soon be used therapeutically. [References: 70]

Levine, S. J. and S. E. Wenzel (2010). "Narrative review: the role of Th2 immune pathway modulation in the treatment of severe asthma and its phenotypes." Annals of Internal Medicine 152(4): 232-237.

New therapeutic approaches are needed for patients with severe asthma who are refractory to standard therapy comprising high doses of inhaled corticosteroids plus long-acting beta(2)-agonists. Current treatment guidelines for patients with severe asthma from the National Asthma Education and Prevention Program recommend the addition of oral corticosteroids, which are associated with substantial morbidity, and, for those with allergic asthma, anti-IgE. Genetic and translational studies, as well as clinical trials, suggest that in a subgroup of patients, the pathobiology of severe asthma is mediated by immune pathways driven by T-helper 2 (Th2)-type CD4(+) T cells, which produce a characteristic repertoire of interleukins (ILs), including IL-4, IL-5, and IL-13. Therefore, biological modifiers of Th2-type ILs, such as monoclonal antibodies, soluble receptors, and receptor antagonists, are a rational strategy for developing new treatment approaches but will need to be targeted to selected patients in whom the appropriate Th2 immune pathway is "active." The benefits of immune-modifier therapies targeting Th2-type cytokines, however, need to be weighed against the toxicities associated with inhibition of key biological pathways, as well as the expense of future medications. Therefore, future clinical trials need to clearly establish the efficacy and safety of biological modifiers of Th2 immune pathways before these approaches can enter routine clinical practice for the treatment of severe asthma. [References: 44]

Rosenbloom, J., S. V. Castro, et al. (2010). "Narrative review: fibrotic diseases: cellular and molecular mechanisms and novel therapies." Annals of Internal Medicine 152(3): 159-166.

Abnormal and exaggerated deposition of extracellular matrix is the hallmark of many fibrotic diseases, including systemic sclerosis and pulmonary, liver, and kidney fibrosis. The spectrum of affected organs, the usually progressive nature of the fibrotic process, the large number of affected persons, and the absence of effective treatment pose an enormous challenge when treating fibrotic diseases. Delineation of the central role of transforming growth factor-beta (TGF-beta) and identification of the specific cellular receptors, kinases, and other mediators involved in the fibrotic process have provided a sound basis for development of effective therapies. The inhibition of signaling pathways activated by TGF-beta represents a novel therapeutic approach for the fibrotic disorders. One of these TGF-beta pathways results in the activation of the nonreceptor tyrosine kinase cellular Abelson (c-Abl), and c-Abl inhibitors, including imatinib mesylate, diminishing the fibrogenic effects of TGF-beta. Thus, recently acquired basic knowledge about the pathogenesis of the fibrotic process has enabled the development of novel therapeutic agents capable of modifying the deleterious effects of the fibrotic diseases. [References: 117]

Spivak, J. L. (2010). "Narrative review: Thrombocytosis, polycythemia vera, and JAK2 mutations: The phenotypic mimicry of chronic myeloproliferation." Annals of Internal Medicine 152(5): 300-306.

The myeloproliferative disorders polycythemia vera, essential thrombocytosis, and primary myelofibrosis are clonal disorders arising in a pluripotent hematopoietic stem cell, causing an unregulated increase in the number of erythrocytes, leukocytes, or platelets, alone or in combination; eventual marrow dominance by the progeny of the involved stem cell; and a tendency to arterial or venous thrombosis, marrow fibrosis, splenomegaly, or transformation to acute leukemia, albeit at widely varying frequencies. The discovery of an activating mutation (V617F) in the gene for JAK2 (Janus kinase 2), a tyrosine kinase utilized by hematopoietic cell receptors for erythropoietin, thrombopoietin, and granulocyte colony-stimulating factor, provided an explanation for the shared clinical features of these 3 disorders. Constitutive JAK2 activation provides a growth and survival advantage to the hematopoietic cells of the affected clone. Because signaling by the mutated kinase utilizes normal pathways, the result is overproduction of morphologically normal blood cells, an often indolent course, and (in essential thrombocytosis) usually a normal life span. Because the erythropoietin, thrombopoietin, and granulocyte colony-stimulating factor receptors are all constitutively activated, polycythemia vera is the potential ultimate clinical phenotype of the JAK2 V617F mutation and, as a corollary, is the most common of the 3 disorders. The number of cells expressing the JAK2 V617F mutation (the allele burden) seems to correlate with the clinical phenotype. Preliminary results of clinical trials with agents that inhibit the mutated kinase indicate a reduction in splenomegaly and alleviation of night sweats, fatigue, and pruritus. [References: 59]

Tobin, M. J., F. Laghi, et al. (2010). "Narrative review: ventilator-induced respiratory muscle weakness." Annals of Internal Medicine 153(4): 240-245.

Clinicians have long been aware that substantial lung injury results when mechanical ventilation imposes too much stress on the pulmonary parenchyma. Evidence is accruing that substantial injury may also result when the ventilator imposes too little stress on the respiratory muscles. Through adjustment of ventilator settings and administration of pharmacotherapy, the respiratory muscles may be rendered almost (or completely) inactive. Research in animals has shown that diaphragmatic inactivity produces severe injury and atrophy of muscle fibers. Human data have recently revealed that 18 to 69 hours of complete diaphragmatic inactivity associated with mechanical ventilation decreased the cross-sectional areas of diaphragmatic fibers by half or more. The atrophic injury seems to result from increased oxidative stress leading to activation of protein-degradation pathways. Scientific understanding of ventilator-induced respiratory muscle injury has not reached the stage where meaningful controlled trials can be done, and thus, it is not possible to give concrete recommendations for patient management. In the meantime, clinicians are advised to select ventilator settings that avoid both excessive patient effort and excessive respiratory muscle rest. The contour of the airway pressure waveform on a ventilator screen provides the most practical indication of patient effort, and clinicians are advised to pay close attention to the waveform as they titrate ventilator settings. Research on ventilator-induced respiratory muscle injury is in its infancy and portends to be an exciting area to follow. [References: 36]

Wang, L., J. G. Seidman, et al. (2010). "Narrative review: harnessing molecular genetics for the diagnosis and management of hypertrophic cardiomyopathy." Annals of Internal Medicine 152(8): 513-520, W181.

Unexplained cardiac hypertrophy, the diagnostic criterion for hypertrophic cardiomyopathy (HCM), occurs in 1 in 500 adults. Insights into the genetic cause and molecular pathophysiology of HCM are reshaping clinical paradigms for diagnosis and treatment of this common myocardial disorder. Human genetic studies have established that dominant mutations in the proteins that make up the contractile apparatus (the sarcomere) cause HCM. With the current availability of clinical gene-based diagnostics, pathogenic mutations in affected patients can be defined, which can suggest a clinical course and allow definitive preclinical identification of family members at risk for HCM. Genetic discoveries have also fostered mechanistic investigations in model organisms that are engineered to carry human HCM mutations. Novel therapeutic targets have emerged from these fundamental studies and are currently under clinical assessment in humans. The combination of contemporary gene-based diagnosis with new strategies to attenuate disease development and progression is changing the natural history of lifelong cardiac symptoms, arrhythmias, and heart failure from HCM. [References: 70]

Greenlee, M., C. S. Wingo, et al. (2009). "Narrative review: evolving concepts in potassium homeostasis and hypokalemia." Annals of Internal Medicine 150(9): 619-625.

Humans are intermittently exposed to large variations in potassium intake, which range from periods of fasting to ingestion of potassium-rich meals. These fluctuations would abruptly alter plasma potassium concentration if not for rapid mechanisms, primarily in skeletal muscle and the liver, that buffer the changes in plasma potassium concentration by means of transcellular potassium redistribution and feedback control of renal potassium excretion. However, buffers have capacity limits, and even robust feedback control mechanisms require that the perturbation occur before feedback can initiate corrective action. In contrast, feedforward control mechanisms sense the effect of disturbances on the system's homeostasis. This review highlights recent experimental insights into the participation of feedback and feedforward control mechanisms in potassium homeostasis. New data make clear that feedforward homeostatic responses activate when decreased potassium intake is sensed, even when plasma potassium concentration is still within the normal range and before frank hypokalemia ensues, in addition to the classic feedback activation of renal potassium conservation when plasma potassium concentration decreases. Given the clinical importance of dyskalemias in patients, these novel experimental paradigms invite renewed clinical inquiry into this important area. [References: 41]

Joy, T. R. and R. A. Hegele (2009). "Narrative review: statin-related myopathy." Annals of Internal Medicine 150(12): 858-868.

Statin-related myopathy is a clinically important cause of statin intolerance and discontinuation. The spectrum of statin-related myopathy ranges from common but clinically benign myalgia to rare but life-threatening rhabdomyolysis. Observational studies suggest that myalgia can occur in up to 10% of persons prescribed statins, whereas rhabdomyolysis continues to be rare. The mechanisms of statin-related myopathy are unclear. Options for managing statin myopathy include statin switching, particularly to fluvastatin or low-dose rosuvastatin; nondaily dosing regimens; nonstatin alternatives, such as ezetimibe and bile acid-binding resins; and coenzyme Q10 supplementation. Few of these strategies have high-quality evidence supporting them. Because statin-related myopathy will probably become more common with greater numbers of persons starting high-dose statin therapy and the increasing stringency of low-density lipoprotein cholesterol level targets, research to better identify patients at risk for statin myopathy and to evaluate management strategies for statin-related myopathy is warranted. [References: 87]

Sowers, J. R., A. Whaley-Connell, et al. (2009). "Narrative review: the emerging clinical implications of the role of aldosterone in the metabolic syndrome and resistant hypertension." Annals of Internal Medicine 150(11): 776-783.

The prevalence of obesity, diabetes, hypertension, and cardiovascular and chronic kidney disease is increasing in developed countries. Obesity, insulin resistance, and hypertension commonly cluster with other risk factors for cardiovascular and chronic kidney disease to form the metabolic syndrome. Emerging evidence supports a paradigm shift in our understanding of the renin-angiotensin-aldosterone system and in aldosterone's ability to promote insulin resistance and participate in the pathogenesis of the metabolic syndrome and resistant hypertension. Recent data suggest that excess circulating aldosterone promotes the development of both disorders by impairing insulin metabolic signaling and endothelial function, which in turn leads to insulin resistance and cardiovascular and renal structural and functional abnormalities. Indeed, hyperaldosteronism is associated with impaired pancreatic beta-cell function, skeletal muscle insulin sensitivity, and elevated production of proinflammatory adipokines from adipose tissue, which results in systemic inflammation and impaired glucose tolerance. Accumulating evidence indicates that the cardiovascular and renal abnormalities associated with insulin resistance are mediated in part by aldosterone acting on the mineralocorticoid receptor. Although we have known that mineralocorticoid receptor blockade attenuates cardiovascular and renal injury, only recently have we learned that mineralocorticoid receptor blockade improves pancreatic insulin release, insulin-mediated glucose utilization, and endothelium-dependent vasorelaxation. In summary, aldosterone excess has detrimental metabolic effects that contribute to the metabolic syndrome and endothelial dysfunction, which in turn contribute to the development of resistant hypertension as well as cardiovascular disease and chronic kidney disease. [References: 56]

Vetter, M. L., S. Cardillo, et al. (2009). "Narrative review: effect of bariatric surgery on type 2 diabetes mellitus." Annals of Internal Medicine 150(2): 94-103.

Bariatric surgery leads to substantial and durable weight reduction. Nearly 30% of patients who undergo bariatric surgery have type 2 diabetes, and for many of them, diabetes resolves after surgery (84% to 98% for bypass procedures and 48% to 68% for restrictive procedures). Glycemic control improves in part because of caloric restriction but also because gut peptide secretion changes. Gut peptides, which mediate the enteroinsular axis, include the incretins glucagon-like peptide-1 and glucose-dependent insulinotropic peptide, as well as ghrelin and peptide YY. Bariatric surgery (particularly bypass procedures) alters secretion of these gut hormones, which results in enhanced insulin secretion and sensitivity. This review discusses the various bariatric procedures and how they alter the enteroinsular axis. Familiarity with these effects can help physicians decide among the different surgical procedures and avoid postoperative hypoglycemia.

Brodsky, R. A. (2008). "Narrative review: paroxysmal nocturnal hemoglobinuria: the physiology of complement-related hemolytic anemia." Annals of Internal Medicine 148(8): 587-595.

Clinical Principles: Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematopoietic stem-cell disorder caused by a somatic mutation in a gene known as phosphatidylinositol glycan class A (PIGA). It may arise de novo or in the setting of acquired aplastic anemia. Clinical presentation can include hemolytic anemia, hemoglobinuria, thrombosis, severe fatigue, abdominal pain, and esophageal spasm. Thrombosis, the leading cause of death from PNH, most commonly occurs in abdominal and cerebral veins. Therapeutic options include supportive care, bone marrow transplantation, and monoclonal antibody therapy with the terminal complement inhibitor eculizumab. Pathophysiologic Principles:The product of the PIGA gene is required for the biosynthesis of a glycolipid anchor that attaches a class of membrane proteins known as glycosylphosphatidylinositol (GPI)– anchored proteins to the cell surface. The absence of GPI-anchored proteins leads to complement- mediated intravascular hemolysis, because 2 important complement regulatory proteins (CD55 and CD59) are missing from PNH cells. Hemolysis in PNH occurs intravascularly. This leads to release of free hemoglobin, a potent nitric oxide scavenger. Depletion of nitric oxide at the tissue level contributes to fatigue, esophageal spasm, thrombosis, and male erectile dysfunction. Eculizumab decreases hemolysis in PNH by binding to C5 and blocking the terminal portion of the complement cascade.

LeGrand, S. B., D. Leskuski, et al. (2008). "Narrative review: furosemide for hypercalcemia: an unproven yet common practice." Annals of Internal Medicine 149(4): 259-263.

Although primary hyperparathyroidism is the most common cause of hypercalcemia, cancer is the most common cause requiring inpatient intervention. An estimated 10% to 20% of all patients with cancer have hypercalcemia at some point in their disease trajectory, particularly in advanced disease. Aggressive saline hydration and varying doses of furosemide continue to be the standard of care for emergency management. However, a review of the evidence for the use of furosemide in the medical management of hypercalcemia yields only case reports published before the introduction of bisphosphonates, in contrast to multiple randomized, controlled trials supporting the use of bisphosphonates. The use of furosemide in the management of hypercalcemia should no longer be recommended. [References: 49]

McDonnell, W. M. and E. Guenther (2008). "Narrative review: do state laws make it easier to say "I'm sorry?"." Annals of Internal Medicine 149(11): 811-816.

Initiatives intended to reduce the frequency and impact of medical errors generally rely on recognition and disclosure of medical errors. However, fear of malpractice liability is a barrier to physician disclosure. Some U.S. state legislatures have attempted to encourage physicians to disclose medical errors by enacting "apology laws." The authors reviewed the codified statutes of each of the 50 states and the District of Columbia to determine the prevalence and characteristics of such apology laws. They found that many states have recently adopted apology laws and that there is variability in these laws. The authors review some of the important differences in these laws and explore the potential impact of apology laws. [References: 66]

Newman, J. H., J. A. Phillips, 3rd, et al. (2008). "Narrative review: the enigma of pulmonary arterial hypertension: new insights from genetic studies." Annals of Internal Medicine 148(4): 278-283.

Pulmonary arterial hypertension (PAH) occurs as an idiopathic disease (formerly called primary pulmonary hypertension) and as a consequence of other illnesses. These illnesses include connective tissue diseases, portal hypertension, diet and stimulant drug use, HIV infection, and congenital heart disease. Inherited susceptibility to PAH occurs in families and is almost always due to mutations in genes of the TGF-beta family of receptors. The most common mutation leading to PAH is in bone morphogenetic protein receptor type 2 (BMPR2), originally discovered to be involved in bone healing. Mutations in BMPR2 have also been found in patients with idiopathic PAH, although the true prevalence of this susceptibility has not been determined. About 20% of individuals with a BMPR2 mutation develop symptomatic pulmonary hypertension. Evidence is growing that imbalanced activation of other TGF-beta receptors coupled with reduced activity of mutated BMPR2 increases the likelihood of development of PAH. Many signaling systems have been found to participate in PAH, including K channels, serotonin, angiopoietin, and cyclooxygenases. An interaction of these signaling systems with BMPR2 is a focus of research in PAH. Approaches to altering the imbalance of activation of BMPR2 and other TGF-beta receptors may yield future therapies for PAH. [References: 47]

Sullivan, L. E. and D. A. Fiellin (2008). "Narrative review: buprenorphine for opioid-dependent patients in office practice." Annals of Internal Medicine 148(9): 662-670.

The profile of opioid dependence in the United States is changing. Abuse of prescription opioids is more common than that of illicit opioids: Recent data indicate that approximately 1.6 million persons abuse or are dependent on prescription opioids, whereas 323,000 abuse or are dependent on heroin. Despite this prevalence, nearly 80% of opioid-dependent persons remain untreated. One option for expanding treatment is the use of buprenorphine and the buprenorphine-naloxone combination. Buprenorphine is a partial opioid agonist that can be prescribed by trained physicians and dispensed at pharmacies. This article addresses the clinical presentation of a patient with opioid dependence and describes the relatively new practice of office-based treatment with buprenorphine-naloxone. The different components of treatment; the role of the physician who provides this treatment; and the logistics of treating this growing, multifaceted patient population are also examined. [References: 86]

Abeles, A. M., M. H. Pillinger, et al. (2007). "Narrative review: the pathophysiology of fibromyalgia." Annals of Internal Medicine 146(10): 726-734.

Primary fibromyalgia is a common yet poorly understood syndrome characterized by diffuse chronic pain accompanied by other somatic symptoms, including poor sleep, fatigue, and stiffness, in the absence of disease. Fibromyalgia does not have a distinct cause or pathology. Nevertheless, in the past decade, the study of chronic pain has yielded new insights into the pathophysiology of fibromyalgia and related chronic pain disorders. Accruing evidence shows that patients with fibromyalgia experience pain differently from the general population because of dysfunctional pain processing in the central nervous system. Aberrant pain processing, which can result in chronic pain and associated symptoms, may be the result of several interplaying mechanisms, including central sensitization, blunting of inhibitory pain pathways, alterations in neurotransmitters, and psychiatric comorbid conditions. This review provides an overview of the mechanisms currently thought to be partly responsible for the chronic diffuse pain typical of fibromyalgia. [References: 111]

Ali, B. and A. M. Zafari (2007). "Narrative review: cardiopulmonary resuscitation and emergency cardiovascular care: review of the current guidelines." Annals of Internal Medicine 147(3): 171-179.

Erratum in

  • Ann Intern Med. 2007 Oct 16;147(8):592

Sudden cardiac death is a major clinical problem, causing 300,000 to 400,000 deaths annually and 63% of all cardiac deaths. Despite the overall decrease in cardiovascular mortality, the proportion of cardiovascular death from sudden cardiac death has remained constant. Survival rates among patients who have out-of-hospital cardiac arrest vary from 5% to 18%, depending on the presenting rhythm. The latest guidelines for cardiopulmonary resuscitation (CPR) and emergency cardiovascular care published by the American Heart Association include substantial changes to the algorithms for basic life support and advanced cardiovascular life support. For unwitnessed cardiac arrest, immediate defibrillation of the patient is no longer recommended. Rather, 2 minutes of CPR before defibrillation is now recommended. People in cardiac arrest should no longer receive stacked shocks. The compression-ventilation ratio has been changed from 15:2 to 30:2. This article is a contemporary review of the management of CPR and emergency cardiovascular care. It examines current practice and data supporting use of CPR, along with changes in the management of sudden cardiac death.

Calabrese, L. H., D. W. Dodick, et al. (2007). "Narrative review: reversible cerebral vasoconstriction syndromes." Annals of Internal Medicine 146(1): 34-44.

Reversible cerebral vasoconstriction syndromes (RCVS) comprise a group of diverse conditions, all characterized by reversible multifocal narrowing of the cerebral arteries heralded by sudden (thunderclap), severe headaches with or without associated neurologic deficits. Reversible cerebral vasoconstriction syndromes are clinically important because they affect young persons and can be complicated by ischemic or hemorrhagic strokes. The differential diagnosis of RCVS includes conditions associated with thunderclap headache and conditions that cause irreversible or progressive cerebral artery narrowing, such as intracranial atherosclerosis and cerebral vasculitis. Misdiagnosis as primary cerebral vasculitis and aneurysmal subarachnoid hemorrhage is common because of overlapping clinical and angiographic features. However, unlike these more ominous conditions, RCVS is usually self-limited: Resolution of headaches and vasoconstriction occurs over a period of days to weeks. In this review, we describe our current understanding of RCVS; summarize its key clinical, laboratory, and imaging features; and discuss strategies for diagnostic evaluation and treatment. [References: 97]

Clarke, J. T. R. (2007). "Narrative review: Fabry disease." Annals of Internal Medicine 146(6): 425-433.

Fabry disease is an X-linked, hereditary, lysosomal storage disease caused by deficiency of the enzyme alpha-galactosidase A, which results in the accumulation of the neutral glycosphingolipid globotriaosylceramide (Gb3) in the walls of small blood vessels, nerves, dorsal root ganglia, renal glomerular and tubular epithelial cells, and cardiomyocytes. It is a complex, multisystem disorder that is characterized clinically by chronic pain and acroparesthesia, gastrointestinal disturbances, characteristic skin lesions (angiokeratomata), progressive renal impairment, cardiomyopathy, and stroke. Enzyme replacement therapy (ERT) with intravenous infusions of recombinant human alpha-galactosidase A consistently decreases Gb3 levels in plasma and clears lysosomal inclusions from vascular endothelial cells. The effects of ERT on other tissues are not as obvious, suggesting that treatment must be initiated early in the course of the disease to be optimally effective or that some complications of the disease are not responsive to enzymes delivered intravenously. [References: 112]

Cohen, M. S., C. Gay, et al. (2007). "Narrative review: antiretroviral therapy to prevent the sexual transmission of HIV-1." Annals of Internal Medicine 146(8): 591-601.

Antiretroviral therapy (ART) has prolonged and improved the lives of persons infected with HIV. Theoretically, it can also be used to prevent the transmission of HIV. The pharmacology of ART in the male and female genital tract can be expected to affect the success of the intervention, and ART agents differ considerably in their ability to concentrate in genital tract secretions. Emergency ART is considered to be the standard of care after occupational exposures to fluids or tissues infected with HIV. More recently, ART for prophylaxis after nonoccupational HIV exposures has been widely used and most countries have developed specific guidelines for its implementation. However, developing clinical trials to prove the efficacy of ART postexposure prophylaxis has not been possible. Experiments with rhesus macaques suggest that therapy must be offered as soon as possible after exposure (within 72 hours) and must be continued for 28 days. Additional nonhuman primate experiments have demonstrated protection from HIV infection with ART preexposure prophylaxis, and several clinical trials are under way to evaluate the safety and efficacy of this approach. The degree to which ART offered to infected persons reduces infectiousness is of considerable public health importance, but the question has not been sufficiently answered. This article provides a review of the data on the use of ART to prevent the sexual transmission of HIV and identify challenges to improving and clarifying this approach. [References: 106]

Kado, D. M., K. Prenovost, et al. (2007). "Narrative review: hyperkyphosis in older persons." Annals of Internal Medicine 147(5): 330-338.

Hyperkyphosis is a widely recognized yet largely ignored condition. Although there are no uniform diagnostic criteria for hyperkyphosis, current studies estimate its prevalence among older adults at 20% to 40%. The causes and consequences of hyperkyphosis are not well understood. Some physicians think that fractures cause hyperkyphosis and that management strategies should focus solely on diagnosis and treatment for osteoporosis. Recent studies, however, demonstrate that many older adults who are most affected by hyperkyphosis do not have vertebral fractures. Hyperkyphosis may be independently associated with an increased risk for adverse health outcomes, including impaired pulmonary function, decreased physical function capabilities, and future fractures. With the growing older population, we now need research that leads to a deeper understanding of the causes, consequences, and treatment of this common condition. [References: 103]