Measuring central corneal thickness with ultrasound pachymetry.

PURPOSE: To determine how many ultrasound pachymetry measurements are required to obtain a reasonable estimate of central corneal thickness. METHODS: Five central corneal thickness measurements were obtained from each eye of 101 patients with normal corneas. The means of fewer than five readings were compared with the mean of five values for each eye to determine the incremental clinical value of additional measurements. RESULTS: Compared with the mean of five values, fewer than three measurements per eye provided a mean central corneal thickness value with inadequate confidence. Conversely, means of more than three readings provided little additional confidence over means of three values. CONCLUSIONS: Central corneal thickness by ultrasound pachymetry can be adequately assessed in the majority of eyes by taking three measurements per eye.     

High-dose vecuronium neuromuscular block: a comparison of arrhythmias and onset of block during sufentanil anaesthesia

This study compared the heamodynamic effects of sufentanil with those observed following concomitant sufentanil and highdose vecuronium administration to determine whether vecuronium induces bradyarrhythmias. Sixty coronary artery bypass patients were stratified into beta blocker (n = 30) or non-beta blocker (n = 30) groups and following induction with sufentanil (9 ± 3 μg · kg^?1) and midazolam (0.07 ± 0.04 mg · kg^?1), received either succinylcholine 1 mg · kg^?1 (SxCh), vecuronium 0.3 mg · kg^?1 (Vec 0.3), or vecuronium 0.5 mg · kg^?1 (Vec 0.5). Using a Holter ECG monitor, bradyarrhythmias were classified as mild (HR 46–50), moderate (HR 40–45) or severe (HR < 40). In the pre-induction period, there were no differences in the incidence of mild, moderate or severe bradyarrhythmias among the SxCh, Vec 0.3 or Vec 0.5 groups, in either the beta blocker or non-beta blocker groups. Following induction, there were similar reductions in mean heart rate and mean arterial pressure in all three muscle relaxant groups in both the beta and the non-beta blocker groups; however, there was no difference in the incidence of mild, moderate or severe bradyarrhythmias among the SxCh, Vec 0.3 or Vec 0.5 groups. The Vec 0.5 beta blocker group had a higher incidence of mild bradyarrhythmias (32 ± 36%) than the Vec 0.5 non-beta blocker group (2 ± 3% P = 0.017). Using EMG recording, the onset time of maximal neuromuscular block for the Vec 0.3 group (108 ± 17 sec) was longer (P < 0.05) than the SxCh (76 ±21 sec) and Vec 0.5 (82 ± 13 sec) groups, which were similar. We conclude: (i) vecuronium does not affect HR or the incidence of bradyarrhythmias following sufentanil administration and that the observed reduction in HR and mean arterial pressure were due to sufentanil administration, (ii) vecuronium (0.5 mg · kg^?1) provides an onset time of neuromuscular block similar to SxCh, and (iii) patients taking beta blockers preoperatively are more prone to develop bradyarrhythmias during sufentanil administration.     

Infusion of a stable prostacyclin analogue, iloprost, to patients with peripheral vascular disease: lack of antiplatelet effect but risk of thromboembolism.

PURPOSE: Prostacyclin, a potent inhibitor of platelet function and vasodilator, has been used to treat peripheral vascular disease. The aim of this study was to monitor the thrombotic status of patients treated by infusion of a stable prostacyclin analogue, iloprost. PATIENTS AND METHODS: Thirteen patients with peripheral vascular disease underwent iloprost infusion for 3 days (8 hours each day) in a dose ranging from 0.5 to 2 ng/kg/minute. Variable parameters of thrombosis such as platelet reactivity (shear-induced hemostatic plug formation and thrombus formation on a collagen fiber), coagulation, and spontaneous thrombolysis (dislodgment of hemostatic plugs) were measured from non-anticoagulated blood samples by hemostatometry immediately before and 1 hour after the infusion and on the last day, 4 hours after initiation of the infusion. RESULTS: Analysis of data from all patients 1 hour after the infusion showed no changes in platelet reactivity and spontaneous thrombolysis, but coagulation was significantly enhanced. In four patients, significant platelet hyperreactivity was observed after the infusion. Four of the five patients tested while undergoing iloprost infusion showed an enhanced thrombotic reaction and markedly enhanced coagulation. Iloprost employed in vitro in a concentration that corresponds to the therapeutic peak blood level caused no inhibition of platelet function but significantly enhanced coagulation. The threshold in vitro iloprost concentration at which anti-platelet effect and increased spontaneous thrombolysis were observed was twice that of the therapeutic blood level. CONCLUSIONS: These findings challenge the view that antagonism of platelet function is an important factor of iloprost therapy. Furthermore, platelet hyperreactivity in some patients and markedly enhanced coagulation during and after infusion of iloprost in general, represent a risk of thromboembolism, especially as patients are already in a prethrombotic condition.     

Trees as indicators of subterranean water flow from a retired radioactive waste disposal site

Tree sampling helped locate a subterranean flow of tritiated water from a low-level radioactive waste disposal site that had not been detected by well water monitoring alone. Deciduous trees growing in a natural forest on the hillsides downslope from the site were sampled for the presence of tritiated water in sap of maple trees and in leaf water extracted from oak and hickory trees. Elevated concentrations of 3H were detected in the leaf water extracted from several trees located 50 m downslope from the western boundary of the fenced exclusion zone. A 3-m-deep well drilled near these trees indicated that the source of tritiated water was a narrow zone of subterranean flow.     

Predicting needs for special education resources for mental retardation from birth defects records.

Planning of service delivery systems for children with special health care needs would be enhanced by knowledge of numbers of cases anticipated in defined geographic areas. A method is described for predicting numbers of children who will likely have mental retardation sufficient to require special education services, based on the birth prevalence of birth defects and clinicians' estimates of the likelihood of mental retardation associated with each specific birth defect. This method is applied to the 1980-82 birth cohort of a 28-county area of south and central Arkansas, and it is compared with special education enrollment data for children ages 6 to 8 in academic year 1988-89. According to this estimate, children with birth defects may account for 32 to 56 percent of the cases of mental retardation among 6- to 8-year-olds reported by the public schools.     

Arterial and Venous Pharmacokinetics of Ropivacaine with and without Epinephrine after Thoracic Paravertebral Block

Background: Animal and volunteer studies indicate that ropivacaine is associated with less neurologic and cardiac toxicity than bupivacaine. Ropivacaine may offer advantages when used for thoracic paravertebral block. This study was designed to describe the pharmacokinetics of ropivacaine after thoracic paravertebral block.

Methods: Twenty female patients undergoing elective unilateral breast surgery were randomly assigned to receive a single bolus thoracic paravertebral injection of 2 mg/kg ropivacaine, with or without 5 [mu]g/ml epinephrine. Simultaneous arterial and venous blood samples were obtained for plasma ropivacaine assay. Data were analyzed with NONMEM, using two possible absorption models: conventional first-order absorption and absorption following the inverse gaussian density function.

Results: Epinephrine reduced the peak plasma concentrations and delayed the time of peak concentration of ropivacaine in both the arterial and venous blood. The time course of drug input into the systemic circulation was best described by two inverse gaussian density functions. The median bioavailability of the rapid component was approximately 20% higher when epinephrine was not used. The mean absorption times were 7.8 min for the rapid absorption phase and 697 min for the slow absorption phase, with wide dispersion of the absorption function for the acute phase. The half-time of arterial-venous equilibration was 1.5 min.     

A multicenter clinical trial of gadolite oral suspension as a contrast agent for MRI

The purpose of this study was to assess the effectiveness and safety of Gadolite Oral Suspension as a gastrointestinal (GI) contrast agent for MRI in a phase II and two phase III multicenter clinical trials. Gadolite was administered to 306 patients with known or suspected abdominal and/or pelvic disease. MRI with T1- and T2-weighted sequences was performed before and after ingestion. Efficacy was evaluated by having two masked readers rate the certainty of their MR diagnosis (0 = uncertain, 1 = probable, 2 = definite) on randomly presented pre- and post-Gadolite Oral Suspension enhanced images. Principal investigators also evaluated the images and established the final diagnosis. Vital signs, clinical chemistries, and adverse events were documented. Blood and urine samples were analyzed for gadolinium content to determine whether Gadolite Oral Suspension was absorbed systemically. Certainty in MR diagnosis increased significantly (P < .001) for both blinded readers between pre- and post-Gadolite images (.49–1.18 for reader 1; .46–1.53 for reader 2). Sensitivity, specificity, and accuracy also increased for both masked readers. No gadolinium was detected in blood or urine samples. There were no serious adverse events and no apparent drug-related trends in mean vital signs or laboratory values. Gadolite is a highly effective, safe, and well tolerated contrast agent for clinical use with MRI.