Citations

ABSTRACTWe describe a thymidine-dependent small-colony variant ofStaphylococcus aureusassociated with left ventricular assist device infection and prosthetic valve and pacemaker endocarditis.

The quality of student life in combined baccalaureate-M.D. degree programs has rarely been investigated although these programs address widely recognized problems in medical education. Through the use of an environmental stress inventory, 183 students' perceptions of the learning environment of a combined-degree program were examined. Students in that program rated few situations in their environment as stressful. Yet, they were significantly concerned about information overload and attendant time problems, just as their peers in 4-yr. schools were. Unlike their 4-yr. counterparts, however, they did not see relations with other students and faculty as problematic. Their scores on the inventory were best predicted at each year level by a combination of personal characteristics, notably living arrangements, sex, and to a lesser extent, introversion.

Background and Purpose —Orthostatic and other stresses trigger tachycardia associated with symptoms of tremulousness, shortness of breath, dizziness, blurred vision, and, often, syncope. It has been suggested that paradoxical cerebral vasoconstriction during head-up tilt might be present in patients with orthostatic intolerance. We chose to study middle cerebral artery (MCA) blood flow velocity (BFV) and cerebral vasoregulation during tilt in patients with orthostatic intolerance (OI). Methods —Beat-to-beat BFV from the MCA, heart rate, CO 2 , blood pressure (BP), and respiration were measured in 30 patients with OI (25 women and 5 men; age range, 21 to 44 years; mean age, 31.3±1.2 years) and 17 control subjects (13 women and 4 men; age range, 20 to 41 years; mean age, 30±1.6 years); ages were not statistically different. These indices were monitored during supine rest and head-up tilt (HUT). We compared spontaneous breathing and hyperventilation and evaluated the effect of CO 2 rebreathing in these 2 positions. Results —The OI group had higher supine heart rates ( P <0.001) and cardiac outputs ( P <0.01) than the control group. In response to HUT, OI patients underwent a greater heart rate increment ( P <0.001) and greater reductions in pulse pressure ( P <0.01) and CO 2 ( P <0.001), but total systemic resistance failed to show an increment. Among the cerebrovascular indices, all BFVs (systolic, diastolic, and mean) decreased significantly more, and cerebrovascular resistance (CVR) was increased in OI patients ( P <0.01) compared with control subjects. In both groups, hyperventilation induced mild tachycardia ( P <0.001), a significant reduction of BFV, and a significant increase of CVR associated with a fall in CO 2 . Hyperventilation during HUT reproduced hypocapnia, BFV reduction, and tachycardia and worsened symptoms of OI; these symptoms and indices were improved within 2 minutes of CO 2 rebreathing. The relationships between CO 2 and BFV and heart rate were well described by linear regressions, and the slope was not different between control subjects and patients with OI. Conclusions —Cerebral vasoconstriction occurs in OI during orthostasis, which is primarily due to hyperventilation, causing significant hypocapnia. Hypocapnia and symptoms of orthostatic hypertension are reversible by CO 2 rebreathing.