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Biomedical subjects

M McRae

Publications and source records attributed to M McRae.

At least 19 recordsLinked to original sources
PubMed2001

Use of percutaneous gastrojejunostomy feeding tubes in the rehabilitation of stroke patients.

OBJECTIVE: To determine the characteristics of and complications in the rehabilitation of stroke patients in whom percutaneous gastrojejunostomy (PGJ) feeding tubes have been placed. DESIGN: Retrospective cohort study. SETTING: A rehabilitation unit in a tertiary care hospital. PARTICIPANTS: Stroke patients (n = 563) admitted to a tertiary care hospital over a 10-year period. INTERVENTION: PGJ feeding tubes. MAIN OUTCOME MEASURES: Evidence of aspiration in all videofluoroscopic modified barium swallow (VMBS) studies was noted. For patients with a PGJ feeding tube, the following were recorded: stroke location; results of subsequent VMBS reports; length of time from stroke onset to PGJ feeding tube insertion; total time the PGJ feeding tube remained in situ; discharge disposition; and concurrent feeding status. Follow-up was at 1-year poststroke. Complications during the inpatient stay attributable to the PGJ feeding tube were recorded. RESULTS: Thirty-two of all 563 (5.7%) stroke patients admitted and 28 of the 115 (24.3%) proven aspirators, as shown on VMBS studies, had a PGJ feeding tube inserted. Twenty-one of the 563 (3.7%) stroke patients were discharged to the community with PGJ feeding tubes in place. The tubes were inserted on average 37 days after stroke onset. Seventeen of all 88 (19.3%) brainstem stroke patients and 15 of all 29 (51.7%) brainstem stroke patients with documented aspiration had feeding tubes inserted, whereas only 15 of 475 (3.2%) hemispheric stroke rehabilitation patients received a tube. Eleven of 32 (34.3%) patients with a feeding tube were able to resume oral feedings at discharge; within 1 year of discharge, 24 of 32 (75%) had done so. Although there were no serious complications resulting from tube insertions, minor complications were documented in more than 50% of the cases. The tubes were associated with prolonged institutionalization in only 1 case; most patients were discharged on a home tube-feeding program. CONCLUSIONS: PGJ feeding tubes were placed in approximately 1 of every 20 of our stroke rehabilitation patients. One third of the tubes were removed before the patients were discharged from rehabilitation and 75% were removed within 1 year. Insertion of the tubes was most common in patients with evidence of aspiration and in patients with brainstem strokes. Complications caused by the tube were minor and all patients but 1 who were discharged with feeding tubes were able to manage the home tube-feeding program.

Cohort Studies↗
PubMed2000

Midface fractures.

Fractures of the middle portion of the facial skeleton are commonly referred to as midface or LeFort fractures. While significant progress has been made in terms of evaluation and treatment of such fractures, they remain a challenge for the maxillofacial surgeon. In this section, we will review the principles of midface fracture evaluation and repair, emphasizing the importance of understanding biomechanics and controversies that exist in respect to repair sequencing.

Dental Occlusion↗
PubMed1999

Frequency of videofluoroscopic modified barium swallow studies and pneumonia in stroke rehabilitation patients: a comparative study.

OBJECTIVE: To study the association between the frequency of videofluoroscopic modified barium swallow (VMBS) studies and the incidence of pneumonia in stroke rehabilitation patients. DESIGN: Retrospective comparative study. SUBJECTS AND SETTING: Five hundred sixty-three consecutive stroke patients admitted to one hospital rehabilitation unit in London, Ontario, Canada were compared with 461 consecutive stroke patients admitted to another hospital rehabilitation unit in the same city. INTERVENTIONS: The number of initial and total VMBS studies and the timing from stroke onset to initial VMBS studies. MAIN OUTCOME MEASURE: Incidence of pneumonia. RESULTS: At the first hospital, 146 patients (25.9%) had 232 total VMBS studies performed, whereas at the second hospital 57 patients (12.4%) had 73 total studies (p<.001). For the first 15 days there was no significant difference in the number of initial VMBS studies performed (8.2% vs. 9.2%). There was a marked difference in the number of initial VMBS studies performed after 15 days (17.2% vs. 2.0%, p<.0001). The difference between the hospitals in the number of VMBS studies in patients with brain stem strokes was not statistically significant, but for patients with hemispheric stroke, the difference was statistically significant. Pneumonia developed in 12 patients at the first hospital (2.1%) and 10 patients at the second hospital (2.2%), a difference that was not significant. CONCLUSIONS: The more frequent use of VMBS beyond 15 days after stroke was not associated with a change in the incidence of pneumonia among hemispheric stroke rehabilitation patients, assuming the two units were otherwise similar.

Aged↗
PubMed1996

Pneumonia associated with aspiration following stroke.

OBJECTIVE: To determine the association between demonstrated aspiration and pneumonia in stroke patients. METHODS: Chart review of 441 consecutive stroke patients admitted to a stroke rehabilitation unit within 4 months of their stroke over an 8-year period. Videofluoroscopic modified barium swallow (VMBS) was performed on all patients suspected of aspirating. In all patients, the presence or absence of pneumonia was noted. RESULTS: Eighty-four of the 441 (19.0%) stroke patients transferred for rehabilitation demonstrated aspiration of thin liquids on VMBS. Twelve of the 441 (2.7%) developed pneumonia while in hospital, either in the acute or rehabilitation phases. The incidence of pneumonia among proven aspirators on VMBS was 10 of 84 (11.9%) patients. Two of the 357 (0.6%) patients who were presumed nonaspirators developed pneumonia. Brain stem and right hemispheric stroke patients had a higher incidence of pneumonia. CONCLUSIONS: Pneumonia is an uncommon complication of stroke. However, approximately 12% of stroke rehabilitation patients diagnosed as aspirators on VMBS developed pneumonia, a 20-fold increase over presumed nonaspirators. VMBS is a potentially valuable tool in determining those patients at risk of aspiration pneumonia.

Acute Disease↗
PubMed1996

Gain changes in the accommodative convergence cross-link.

The output of the accommodative vergence cross-link, the AC/A ratio, was measured before and after subjects viewed through a telestereoscope which increased their interocular separation (pd) approximately fourfold. The initial paradigm was designed to force an increase in the AC/A ratio in that subjects alternately fixated targets set at differing distances. In this paradigm, the varying vergence demands could not be met by a constant increase in phasic or tonic vergence responses. In a second paradigm, only one target was viewed at a fixed position from the eye. Now the constant vergence demand could be met by a set increase in phasic and/or tonic vergence. A significant increase in the AC/A ratio was found in the two-target study but not in the single-target study. Increases in the accommodative vergence gain did show considerable individual differences. Tonic vergence changes were interpolated from the data. This parameter increased significantly in both cases but more so when two targets were alternately fixated. This finding is consistent with current near triad models which predict that accommodative convergence input acts along with disparity vergence input to increase tonic levels of convergence. When AC/A ratios were calculated using clinical measures of the phoria at 6 and 0.4 m, increases were found in the two-target study and to a lesser degree in the single-target study. This clinical method of AC/A measure appears to have been confounded by changes in tonic vergence.

Accommodation, Ocular↗
PubMed1994

Prevalence and recovery of aspiration poststroke: a retrospective analysis.

This retrospective study was undertaken to review aspiration documented by videofluoroscopic modified barium swallow (VMBS) examination in a group of patients admitted to a stroke rehabilitation unit. Forty-two of 54 patients tested demonstrated evidence of aspiration of thin liquids on VMBS performed an average of over 5 weeks following the onset of stroke. However, only patients in whom there was clinical concern of aspiration (54 of 255 stroke patients admitted to the rehab unit) were tested with VMBS evaluation. With this limitation in mind, aspiration was demonstrated in at least 9.9% of all unilateral right hemispheric patients, 12.1% of unilateral left hemispheric, 24% of bilateral hemispheric, and 39.5% of brainstem stroke patients. Of the 42 patients in whom aspiration of thin liquids was demonstrated, 31 underwent repeat VMBS studies an average of 6 weeks after the initial VMBS. 7 of these 31 (22.6%) no longer showed aspiration on VMBS. Eighteen of the 42 patients (43%) clinically stopped aspirating over this 6-week period.

Aged↗
PubMed1992

Identification of proteins binding to interferon-inducible transcriptional enhancers in hematopoietic cells.

The binding of nuclear proteins of hematopoietic cells to transcriptional enhancers of interferon-inducible genes has been studied before and after exposure to alpha-interferon. Mobility shift assays show that a complex formed with interferon-inducible transcriptional enhancers before interferon induction contains a 73- and 84-kDa protein. Amino acid sequencing of the oligoaffinity column purified 73- and 84-kDa proteins showed that they belonged to a family of DNA-binding proteins which have been previously identified to exhibit binding in a sequence nonspecific manner to the ends of fragmented DNA or the origin of replication of adenovirus Type 2 DNA and sequence-specific binding to the distal regions of the U1 small nuclear RNA promoter, the promoter of the transferrin receptor gene, and the transcriptional regulatory regions of HLA genes. Following exposure to alpha-interferon, more slowly migrating complexes appeared which contained a 48-kDa protein, a 95-kDa protein, and a 105-kDa protein which bound to the 9-27 transcriptional enhancer in a sequence-specific manner.

Affinity Labels↗
PubMed1991

Intravascular ultrasound imaging following balloon angioplasty.

Despite its long history and reliability, contrast angiography has several inherent limitations. Because it is a two-dimensional projection image of the lumen contour, the wall thickness cannot be measured and the plaque itself is not visualized. This results in an underestimation of the amount of atherosclerotic disease by angiography. An assessment of atherosclerosis could be improved by an imaging modality: (1) that has an inherent larger magnification than angiography and (2) that directly visualizes the plaque. Intravascular ultrasound fulfils these criteria. This presentation will provide evidence that intravascular ultrasound may prove complimentary or even superior to angiography as an imaging modality. Intravascular ultrasound demonstrates excellent representations of lumen and plaque morphology of in vitro specimens compared with histology. There is very close intraobserver and interobserver variability of measurements made from intravascular ultrasound images. Phantom studies of stenoses in a tube model demonstrate that angiography can misrepresent the severity of stenosis when the lumen contour is irregular and not a typical ellipse, whereas intravascular ultrasound reproduces the cross-sectional morphology more accurately since it images the artery from within. In vitro studies of the atherosclerotic plaque tissue characteristics compare closely with the echo representation of fibrosis, calcification, and lipid material. In addition, in vitro studies of balloon angioplasty demonstrate that intravascular ultrasound accurately represents the changes in the structure of artery segments following balloon dilatation.

Angioplasty, Balloon↗
PubMed1991

Intravascular ultrasound imaging of human coronary arteries in vivo. Analysis of tissue characterizations with comparison to in vitro histological specimens.

BACKGROUND: Intravascular ultrasound imaging was performed in 27 patients after coronary balloon angioplasty to quantify the lumen and atheroma cross-sectional areas. METHODS AND RESULTS: A 20-MHz ultrasound catheter was inserted through a 1.6-mm plastic introducer sheath across the dilated area to obtain real-time images at 30 times/sec. The ultrasound images distinguished the lumen from atheroma, calcification, and the muscular media. The presence of dissection between the media and the atheroma was well visualized. These observations of tissue characterization were compared with an in vitro study of 20 human atherosclerotic artery segments that correlated the ultrasound images to histological preparations. The results indicate that high-quality intravascular ultrasound images under controlled in vitro conditions can provide accurate microanatomic information about the histological characteristics of atherosclerotic plaques. Similar quality cross-sectional ultrasound images were also obtained in human coronary arteries in vivo. Quantitative analysis of the ultrasound images from the clinical studies revealed that the mean cross-sectional lumen area after balloon angioplasty was 5.0 +/- 2.0 mm2. The mean residual atheroma area at the level of the prior dilatation was 8.7 +/- 3.4 mm2, which corresponded to 63% of the available arterial cross-sectional area. At the segments of the coronary artery that appeared angiographically normal, the ultrasound images demonstrated the presence of atheroma involving 4.7 +/- 3.2 mm2, which was a mean of 35 +/- 23% of the available area bounded by the media. CONCLUSIONS: Intravascular ultrasound appears to be more sensitive than angiography for demonstrating the presence and extent of atherosclerosis and arterial calcification. Intracoronary imaging after balloon angioplasty reveals that a significant amount of atheroma is still present, which may partly explain why the incidence of restenosis is high after percutaneous transluminal coronary angioplasty.

Angiography↗
PubMed1990

Assessment of normal and atherosclerotic arterial wall thickness with an intravascular ultrasound imaging catheter.

A prototype intravascular ultrasound imaging catheter with a 20 MHz transducer was used to obtain 59 cross-sectional images in 14 segments of human atherosclerotic arteries. Three distinct components of the arterial wall were visualized on the ultrasound images: a highly reflective intima, an echolucent media, and a moderately reflective adventitia. Images were obtained at 1 mm increments in vitro and were compared with histologic sections at the same levels. Measurements of the arterial layers showed a close correlation between ultrasound images and histologic sections for the thickness of the intimal plaque (r = 0.91), the media (r = 0.83), and the total wall thickness (r = 0.85). The ultrasound images overestimated the mean intimal and total wall thickness by 0.3 mm and 0.7 mm compared to measurements in histologic sections (p less than 0.001). Intravascular imaging with high-frequency ultrasound is an accurate method for measuring microanatomic arterial dimensions and the extent of atheromatous involvement of the arterial wall. This method could represent an important adjunct to traditional angiographic techniques for assessing the severity of atherosclerosis.

Arteries↗
PubMed1989

Intravascular ultrasound cross-sectional arterial imaging before and after balloon angioplasty in vitro.

A prototype ultrasound imaging catheter was evaluated in vitro using 17 human atherosclerotic artery segments before and after balloon dilatation angioplasty. The catheter was 1.2 mm in diameter and incorporated a single 20-MHz ultrasound transducer to obtain cross-sectional images of the arterial lumen. In 15 of the 17 (88%) arteries, high quality images were obtained, which demonstrated clear demarcation between the lumen and the endothelium, the atheroma plaque, the muscular media, and the adventitia. Qualitative characteristics of plaque disruption, dissection, and residual flaps were readily visible. In addition, quantitative information about cross-sectional lumen area was obtained before and after balloon dilatation. The mean cross-sectional lumen area increased from 8.7 to 15.1 mm2 (p less than 0.01) following balloon dilatation. The lumen area measured from the ultrasound images following dilatation correlated closely with the area measured from histologic sections (r = 0.88). The results from this study indicate that a small-diameter ultrasound imaging catheter can be developed that will provide high-resolution qualitative and quantitative information during peripheral and coronary angioplasty.

Angioplasty, Balloon↗
PubMed1986

Maternal position during parturition in normal labor.

While controversy exists as to the relationship between maternal position in labor and such measures as the labor duration, subjective discomfort, and fetal outcome, little appears to be known about the positions women assume in labor when they are permitted to do so without coercion or instruction. To learn more about maternal position in labor, we observed 80 consecutive patients with uncomplicated normal spontaneous vaginal delivery over the course of labor to ascertain the positions volitionally chosen by each. Data were collected on position preferences and phase of labor. All labors were analyzed; a codified lexicon was established to describe the position pattern in each phase and the principal positions the patient assumed over the course of labor. The frequencies and distributions were determined for nulliparas and multiparas separately and rates of position change were assessed. It was found that gravidas chose a number of different principal positions in the early phases of labor, but that they became more narrowly selective in the deceleration phase and second stage; at the same time, they tended to change position more often in late labor.

Adolescent↗
PubMed1982

Is estrogen required for implantation in the ferret?

A series of experiments was designed to further test the hypothesis that ferret corpora lutea synthesize and secrete estrogen between Days 6 and 8 of pregnancy, and that this estrogen is required to initiate implantation of blastocysts on Day 12. Corpora lutea, removed on Day 8 of pregnancy contained significant quantities of testosterone. Incubation of aliquots of the same luteal tissue for 4 h significantly elevated estrogen levels above those of nonincubated controls. Peripheral plasma estrogen levels exhibited a slight increase on Day 8 over those observed on Day 6 of pregnancy (7.9 +/- 3.4 vs. 4.1 +/- 1.1 pg/ml). However, continuous release of estradiol from Days 6-8 from two different sizes of Silastic capsules failed to induce implantation in ovariectomized-progesterone treated ferrets, whereas this same treatment was compatible with nidation in intact ferrets. Administration of the aromatase inhibitor, androsta-1,4,6-triene-3,17-dione (ATD) on Days 5-8 of pregnancy prevented implantation of blastocysts on Day 13. Simultaneous administration of estradiol and ATD failed to reverse the inhibitory effect of ATD. Results of this study confirm that luteal tissue of ferrets possesses at least one aromatizable androgen which is converted to estrogen under physiological conditions. However the data do not support the hypothesis that estrogen is required for implantation in the ferret.

Androstatrienes↗
PubMedDate not supplied

The reproducibility of intravascular ultrasound imaging in vitro.

To determine which factors may affect the image quality when an intravascular ultrasound catheter is used in vivo, the influence of blood, temperature change, and contrast media were evaluated. In addition, to confirm the reproducibility of intravascular ultrasound imaging to measure cross-sectional lumen area, intraobserver and interobserver variability were determined. The findings indicated that ultrasound images in blood are mildly attenuated, that changes from room temperature to body temperature do not have a significant impact on the image quality, that contrast media attenuates the image intensity in a dose-dependent manner, and that the intravascular ultrasound imaging catheter provides a reproducible method for measuring arterial lumen area with excellent intraobserver and interobserver correlation.

Arteriosclerosis↗