Transmission of human immunodeficiency virus (HIV) is known to occur perinatally, through sexual contact, and after exposure to infected blood or blood products. The possibility that breast milk may transmit HIV continues to be evaluated. There is no epidemiologic evidence that contact with saliva, tears, or urine has resulted in HIV infection. However, because HIV has (in some cases rarely) been isolated from these body fluids, guidelines have been developed to reduce more extensive exposures to such secretions. Laboratory and epidemiologic data strongly indicate that HIV is not transmitted through immune globulin preparations, the hepatitis B vaccine, or contact with insects. Increasing evidence from many studies also indicates that HIV is not transmitted through casual contact. All individuals need to be aware of how HIV is and is not transmitted, to reduce high-risk behaviors and to avoid unnecessary fears and actions.

This report reviews the current applications of magnetic resonance imaging of the central nervous system. Since its introduction into the clinical environment in the early 1980s, this technology has had a major impact on the practice of neurology. It has proved to be superior to computed tomography for imaging many diseases of the brain and spine. In some instances it has clearly replaced computed tomography. It is likely that it will replace myelography for the assessment of cervicomedullary junction and spinal regions. The magnetic field strengths currently used appear to be entirely safe for clinical application in neurology, except in patients with cardiac pacemakers or vascular metallic clips. Some shortcomings of magnetic resonance imaging include its expense, the time required for scanning, and poor visualization of cortical bone.

Corneal transplantation is the most common form of organ transplantation practiced in the United States. Two procedures for transplantation are utilized. Penetrating keratoplasty is used in about 90% of the cases, with lamellar keratoplasty being utilized in the remaining situations. Demand for corneal transplantation exceeds the available supply of corneas. Advances in procurement and preservation must continue to meet this demand. Finally, these procedures are not without complications, and these are discussed to provide a clear risk-benefit analysis.

Neural tube defects (NTDs) are a group of malformations of the brain and spinal cord that originate at various times during gestation. The most common NTDs are anencephaly and meningomyelocele, which arise during the process of neurulation, a well-defined period between the 17th and 30th day after ovulation. These NTDs are clinically apparent by being open, ie, leaving nervous tissue exposed, in contrast to postneurulation NTDs that are skin covered. The incidence of NTDs is declining in several areas of the world, including the United States. While the reasons for this are unclear, there seems to be some effect from prenatal diagnosis, genetic counseling, and possibly nutritional supplementation.

Nitroglycerin and the long-acting nitrates are beneficial in stable and unstable angina pectoris and acute myocardial infarction and as adjunctive therapy in congestive heart failure. Nitroglycerin compounds relax vascular smooth muscle, producing venous, arterial, and arteriolar dilatation. These actions are modulated by stimulation of intracellular cyclic guanosine monophosphate. Nitrate efficacy in ischemic heart disease is due to peripheral venous and arterial vasodilatation that results in decreased myocardial oxygen consumption. Nitrates also dilate coronary arteries and collaterals, reverse coronary vasoconstriction, and enlarge some coronary atherosclerotic lesions. Nitrates improve exercise performance in stable angina pectoris. Intravenous nitroglycerin should be used in the initial treatment of unstable angina. Nitrates may be beneficial in myocardial infarction for control of ischemic pain, acute hypertension, and left ventricular failure. In subjects with congestive heart failure, nitrates reduce symptoms and improve exercise tolerance. Nitrate tolerance is a problem with continuous nitrate therapy. Tolerance is most likely to occur with frequent dosing or the use of long-acting nitrates, particularly transdermal nitroglycerin disks, and can be prevented or reversed with intermittent-dosing regimens.

State-of-the-art magnetic resonance imaging (MRI) generates high-resolution images of the cardiovascular system. Conventional MRI techniques provide images in six to ten minutes per tomographic slice. New strategies have substantially improved the speed of imaging. The technology is relatively expensive, and its cost-effectiveness remains to be defined in relation to other effective, less expensive, and noninvasive technologies, such as echocardiography and nuclear medicine. The ultimate role of MRI will depend on several factors, including the development of specific applications such as (1) noninvasive angiography, especially of the coronary arteries; (2) noninvasive, high-resolution assessment of regional myocardial blood flow distribution (eg, using paramagnetic contrast agents); (3) characterization of myocardial diseases using proton-relaxation property changes; and (4) evaluation of in vivo myocardial biochemistry. The three-dimensional imaging capability and the ability to image cardiovascular structures without contrast material give MRI a potential advantage over existing noninvasive diagnostic imaging techniques. This report analyzes current applications of MRI to the cardiovascular system and speculates on their future.

Patient-controlled analgesia (PCA) provides improved titration of analgesic drugs, thereby minimizing individual pharmacokinetic and pharmacodynamic differences. Patient-controlled analgesia decreases patient anxiety resulting from delays in receiving pain-relieving medication and from the slow onset of analgesic action when these drugs are administered either intramuscularly or in the extradural space. With PCA therapy, patients are reportedly able to maintain a near optimal state of analgesia with minimal sedation and few side effects. The potential for overdose can be minimized if small bolus doses are used with a mandatory lockout interval between successive doses. Finally, studies of the cost-effectiveness of PCA therapy are important if this therapeutic approach is to achieve more widespread acceptance.

The American Medical Association Council on Long Range Planning and Development has identified trends in the environment of medicine that are likely to affect the future of obstetrics and gynecology practice. The professional liability crisis is among the most potent factors affecting the types and numbers of services that obstetricians and gynecologists will provide in the future. The setting for obstetrics and gynecology practice is likely to be affected by advances in technology and trends in delivery and reimbursement systems. Two factors with potential to affect the organization of practice are the high numbers of women entering the specialty and increasing practice expenses, largely associated with liability costs. Other factors affecting future patterns of delivery include the anticipated aging of the female population and the changing social and economic roles of women. In particular, the feminist movement has focused more attention on women's health care and is expected to have a continuing impact on the delivery of obstetric and gynecologic care. The Council concludes that the most salient issues for the specialty in the future will be the following: (1) the direction of the professional liability crisis, (2) medical practice competition, (3) the feminization of poverty, (4) ethical issues arising from technological and social imperatives, (5) the changing gender profile of the specialty, and (6) the impact of the feminist movement on women's health care.

Changes in continuing medical education (CME) during the past three decades have been controversial and complex. A 1950s-style, small-scale, voluntary activity has evolved, in 1987, into broad-scale programs with accredited sponsors and with ties to relicensure. Within the next three decades, CME will be directed by methods chosen by specialty boards for recertification and by exploitation of computer and telecommunication technology. Written recertification examinations can waste physicians' time studying material that will not improve care of their patients. We hope improved methods of analysis of individual practices, on-the-spot access to pertinent medical information, and better communication among physicians can be incorporated into recertification procedures. Policies established now will shape CME for decades to come. We encourage a coordinated effort by medical specialty boards, medical societies, hospitals, medical schools, computer corporations, telecommunication firms, granting agencies, and the National Library of Medicine to ensure the most effective and efficient recertification and CME policies.

The growing number of couples seeking to adopt may have outstripped the number of babies in the United States available for adoption. Although increased availability and use of abortion have resulted in fewer single women continuing their pregnancies, the increased tendency of unmarried mothers to raise rather than relinquish their children has, in particular, limited the number of babies available for adoption. Despite the unpopularity of adoption among women with unintended pregnancies, addressing this option remains an important part of pregnancy counseling. Appropriate obstetric care of women placing their babies for adoption includes acknowledgment of the loss these women experience. Knowledge of adoption resources and willingness to discuss adoption can help physicians provide better care of unintentionally pregnant as well as infertile patients.

A new class of drugs, which inhibit de novo cholesterol biosynthesis, significantly reduces the blood cholesterol concentrations in hypercholesterolemic patients. Four separate inhibitors have lowered plasma total cholesterol and low-density lipoprotein (LDL) levels in humans by 20% to 40%: mevastatin (Compactin), lovastatin (mevinolin), pravastatin (CS-514, Eptastatin, and SQ 31000), and simvastatin (Synvinolin, MK-733). In addition to lowering total and LDL cholesterol concentrations, the plasma concentration of the potentially atherogenic B apolipoprotein is also reduced by 20% to 40%. The reduction in the levels of circulating atherogenic lipoprotein particles occurs as a result of decreased synthesis and enhanced removal of LDLs by the LDL receptor pathway in hepatocytes. Moreover, the levels of high-density lipoprotein cholesterol, which are inversely related to atherosclerosis, increase in concentration with treatment by these drugs. If the short-term safety of these drugs extends to ongoing long-term studies and if cardiovascular morbidity and mortality are affected by their use, this class of hypolipidemic agent will markedly facilitate the effective treatment of hypercholesterolemia.

Medical imaging methods traditionally have depicted variations in one or two simple physical variables in tissues, eg, physical density, atomic number, acoustic velocity, and radioactivity concentration. Magnetic resonance images reveal differences in several variables, with the prominent variables reflecting complex energy transfer mechanisms that occur at the atomic and nuclear levels. Furthermore, the relative contributions of these variables to the image are readily altered by changing the pulse sequence and the pulsing times within the sequence. These changes dramatically affect the image and its characterization of normal and abnormal anatomy. Hence, magnetic resonance images and their contributions to diagnostic medicine can be properly appreciated only if one has some understanding of the procedures by which they are produced.