Effects of alterations in left ventricular filling, contractility, and systemic vascular resistance on the ascending aortic blood velocity waveform of normal subjects.

OBJECTIVES: To confirm the consistent effects on Doppler-measured aortic blood flow velocity waveform variables of alterations in left ventricular preload, afterload, and inotropy using pharmacologic and physiologic maneuvers. SETTING: Medical school laboratory. SUBJECTS: Healthy volunteers. INTERVENTIONS: Increasing infusion rates of dobutamine (1.25 to 5 micrograms/kg.min), esmolol (1.25 to 5 mg/min), phentolamine (1.25 to 5 mg/min), methoxamine (1.25 to 5 mg/min), metaraminol (1.25 to 5 mg/min), and placebo (1.25 to 5 mL of 0.9% saline/min) and increasing plasma removal (0.5 to 1 L) in awake, rested, supine subjects. MEASUREMENTS AND MAIN RESULTS: Ascending aortic blood flow was measured by the suprasternal Doppler approach allowing calculation of waveform variables of stroke distance and minute distance (linear measures of stroke volume and cardiac output), peak velocity, mean acceleration and flow time corrected for heart rate. An index of systemic vascular resistance was obtained by dividing mean systemic BP by the minute distance. Inotropic changes predominantly affected peak velocity and mean acceleration. Changes in preload mainly affected the flow time corrected for heart rate, whereas afterload changes had an intermediate effect. Unsuspected but subsequently confirmed hemodynamic effects were seen with esmolol and metaraminol. CONCLUSIONS: Aortic blood flow velocity waveform variables measured by Doppler ultrasound can be used to noninvasively follow changes in left ventricular preload, afterload, and inotropy.     

Changes in alpha 2-adrenoceptors on vascular smooth muscle and neural membranes following hypertension induced by renal ischemia.

alpha 2-Adrenoceptors were characterized on neural and vascular membranes from 2-kidney-1-clip renal hypertensive (RHT) and normotensive (NT) rats. Rats were sacrificed 6 weeks after induction of renal ischemia, and the specific binding of 3H-clonidine to smooth muscle membranes form tail arteries and neural membranes from various brain regions was examined. Additionally, isometric contractions of helically cut tail artery strips produced by various alpha-adrenoceptor agonists were measured. Scatchard analysis indicated an increased number of high-affinity binding sites on the smooth muscle membranes from RHT rats (Bmax = 43.5 +/- 1.4 fmol/mg protein) compared to that from the NT rats (25.4 +/- 3.8 fmol/mg protein). An increased contractile sensitivity to clonidine was also observed in tail artery strips from RHT rats (EC50 for RHT = 3.04 x 10(-8) M; NT = 1.52 x 10(-7) M). In neural tissue, the number of alpha 2-adrenoceptor-binding sites was significantly increased in the locus coeruleus from RHT rats, but not in the amygdala, hypothalamus, parietal cortex, hippocampus or lower brain stem. These results demonstrate that renal ischemia produces changes in both peripheral and neural alpha 2-adrenoceptor density. The increase in smooth muscle alpha 2-adrenoceptors might also provide a partial explanation for the supersensitivity to adrenergic agonists in this model of hypertension.     

Reversible and irreversible effects of chemical fixation on the NMR properties of single cells.

The effects of chemical fixation are known to alter MR parameters, such as relaxation times and the apparent diffusion coefficient (ADC) of water. It is often assumed that such changes are reversible after samples have been reimmersed in a buffer solution for a sufficient period of time. In this study we characterize the changes associated with fixation of single Xenopus laevis oocytes and their subsequent reimmersion in buffer. Substantial reductions in both T(1) and T(2) values were measured for all compartments of the cell after fixation, with the cytoplasm showing larger changes than the nucleus. After reimmersion in buffer, there were small but statistically significant differences in MR parameters between fresh and reimmersed cells. Experiments with a gadolinium (Gd) contrast agent showed evidence of irreversible changes in the permeability of cellular membranes to small molecules.     

The incidence of postoperative wound healing problems following sagittal ramus osteotomies stabilized with miniplates and monocortical screws.

PURPOSE: Titanium plates and monocortical screws are commonly used to stabilize the mandible following sagittal split ramus osteotomies. Despite widespread use of this type of fixation, there is a paucity of large studies evaluating the infection rate and need for hardware removal. MATERIALS AND METHODS: This study is a retrospective cohort evaluation of 1,066 consecutive mandibular sagittal ramus osteotomies in 533 patients, performed between January 2002 and December 2003. All osteotomies were stabilized with 4-hole miniplates and 2.0 mm x 5.0 mm monocortical screws. Study variables included disturbances of wound healing, age, gender, plate and screw position, direction of mandibular movement, adjunctive procedures performed, and the patient's medical history. Data were collected by chart and radiographic review. The above variables were analyzed using Fisher's exact test, Chi-square, Cochran-Armitage Trend Test, and multiple logistic regression. RESULTS: Of 533 patients 26% (138) demonstrated wound healing problems. This occurred in 15% of all 1,066 osteotomy sites. 6.5% of plates required removal in 10% of patients. In no case did disturbance of wound healing or plate removal result in non-union or relapse of the osteotomy. Wound healing problems were fewer when mandibular osteotomies were done in conjunction with maxillary surgery (18.9% versus 29.1%). Disturbances of wound healing were not related to the direction of movement of the mandible and were lower when hardware was placed closer to the inferior border. CONCLUSION: An overall low incidence (6.5%) of hardware infection requiring plate removal was found in this study. Screw proximity to the osteotomy site did not correlate with higher rates of healing problems, but there was a statistically significant trend of fewer disturbances of healing when the hardware was placed closer to the inferior border of the mandible.     

Comparative bond strength of brackets cured using a pulsed xenon curing light with 2 different light-guide sizes.

Light curing of composite resin material beneath orthodontic brackets is common in clinical orthodontics. Experiences with composite resins and high-intensity lights indicate some advantages to staged curing of the composite. In this study, the shear/peel bond strength of orthodontic brackets bonded to bovine enamel and cured with a pulsed xenon plasma arc light was compared with that of bonds cured with a conventional tungsten-quartz-halogen light and a nonpulsed xenon plasma arc light. The pulsed light provided less light energy than the nonpulsed lights. A small and a larger light-guide tip were used with the pulsed xenon plasma arc light. Three different orthodontic composite resin adhesives were tested with each light. The pulsed xenon plasma arc light resulted in either the same or decreased shear/peel bond strength when compared with the nonpulsed lights. There appeared to be no advantage to the use of a pulsed xenon plasma arc light in bonding orthodontic brackets. Results from using either a small or a large light-guide tip varied with the adhesive tested.     

SRTR Center-Specific Reporting Tools: Posttransplant Outcomes

Measuring and monitoring performance—be it waiting list and posttransplant outcomes by a transplant center, or organ donation success by an organ procurement organization and its partnering hospitals—is an important component of ensuring good care for people with end-stage organ failure. Many parties have an interest in examining these outcomes, from patients and their families to payers such as insurance companies or the Centers for Medicare and Medicaid Services; from primary caregivers providing patient counseling to government agencies charged with protecting patients.
The Scientific Registry of Transplant Recipients produces regular, public reports on the performance of transplant centers and organ procurement organizations. This article explains the statistical tools used to prepare these reports, with a focus on graft survival and patient survival rates of transplant centers—especially the methods used to fairly and usefully compare outcomes of centers that serve different populations. The article concludes with a practical application of these statistics—their use in screening transplant center performance to identify centers that may need remedial action by the OPTN/UNOS Membership and Professional Standards Committee.     

Eyelid movements during blinking in patients with Parkinson's disease.

We examined eyelid movements during spontaneous, voluntary, and trigeminal reflex blinks in 16 patients with mild to moderate Parkinson's disease (PD) off medication and 14 controls. Voluntary and reflex blink amplitudes tended to be smaller than normal for PD patients, whereas eyelid kinematics (amplitude-maximum velocity relationship) for all three blink types were normal. Spontaneous blink rate was less than normal for 10 patients and abnormally high for 6 patients. A significant positive correlation between spontaneous blink amplitude and blink rate was found. These observations suggest that PD modifies the gain of a premotor blink circuit shared by spontaneous, voluntary, and reflex blinks.