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Biomedical subjects

R Caldwell

Publications and source records attributed to R Caldwell.

At least 19 recordsLinked to original sources
PubMed1997

Survival and risk factors for death after cardiac transplantation in infants. A multi-institutional study. The Pediatric Heart Transplant Study.

BACKGROUND: Despite the increasing application of cardiac transplantation in infants, reported survival rates vary, and risk factors for death are poorly understood. METHODS AND RESULTS: To examine early survival and risk factors for death in infants (< 1 year of age) undergoing cardiac transplantation, 141 infants (36 < 1 months of age) underwent primary cardiac transplantation between January 1, 1993, and January 1, 1995, at 23 centers in the Pediatric Heart Transplant Study (PHTS). Diagnoses were hypoplastic left heart syndrome (66%), other congenital heart disease (17%), cardiomyopathy (14%), and other (3%). Actuarial survival after cardiac transplantation was 84% at 1 month, 70% at 1 year, and 69% at 2 years, with the greatest hazard for death within the first 3 months. The principal cause of death was early graft failure in 20 patients (52% of deaths), infection in 10 (26% of deaths), and rejection in 4 (10%). On the basis of multivariate analysis, risk factors for early mortality were history of previous sternotomy (P = .0003), nonidentical blood type donor (P = .01), recipient non-blood group A (P = .02), and donor cause of death other than closed head trauma (P = .04). Diagnosis at listing, waiting time (mean, 1.3 months), graft ischemic time (mean, 228 minutes; range, 68 to 479 minutes), and recipient ventilatory or inotropic support at listing were not predictive for mortality after transplant. CONCLUSIONS: The higher mortality rate observed with infant heart transplantation is due to a higher mortality within the first month after transplantation as a result of early graft failure. Strategies to improve donor heart function at implantation would have the greatest impact on survival after infant cardiac transplantation.

Actuarial Analysis↗
PubMed1996

The ampS-nprE (124 degrees-127 degrees) region of the Bacillus subtilis 168 chromosome: sequencing of a 27 kb segment and identification of several genes in the area.

A stretch of DNA approximately 27 kb in length, adjacent to the nprE gene of Bacillus subtilis, has been sequenced. The sequenced fragment carries a total of 23 ORFs. Of these, 15 could be assigned probable functions based on homologies to characterized genes either in B. subtilis or in other organisms. The sequencing of this region has also allowed us to assign to this area adeC and strB, previously located on the other side of nprE, between nprE and the pyr operon.

Bacillus subtilis↗
PubMed1995

Superoxide dismutase improves posttraumatic cortical blood flow in rats.

Oxygen free radicals, such as the superoxide anion, are known to mediate damage to the cerebral microcirculation following traumatic brain injury. The purpose of this study was to determine if superoxide dismutase (SOD), a scavenger of superoxide anion, could alter posttraumatic cortical blood flow. Following barbiturate anesthesia, rats were surgically prepared for moderate fluid percussion brain injury. Cortical blood flow contralateral to the site of injury was measured using laser-Doppler flowmetry. Laser-Doppler flowmetry assesses flow by measuring cell volume and velocity, which are multiplied electronically to give flow. Starting 10 min before injury, animals received either superoxide dismutase (24,000 U/kg bolus, followed by continuous infusion of 1600 U/kg/min) or an equal volume of saline. Blood pressure, heart rate, and cortical blood flow were measured up to 1 h posttrauma. Rats receiving superoxide dismutase had significantly higher cortical blood flow posttrauma (F = 6.91, p < 0.02). One hour posttrauma, the blood flow in SOD-treated rats was 89 +/- 8% of preinjury baseline, whereas this value was only 66 +/- 6% of control in saline-treated rats. SOD caused not only greater blood velocity but also less reduction in cortical blood volume after injury. There were no significant differences between the groups with respect to blood pressure or heart rate. This study further supports the role of oxygen radical-mediated cerebrovascular dysfunction following traumatic brain injury and is the first to show the beneficial effect of SOD on cortical blood flow following fluid percussion brain injury.

Animals↗
PubMed1994

Cardiac transplantation in infants and children.

Cardiac transplantation has become a more frequently used therapeutic modality for select cardiac pathology in infants and children. Since June 1986, 30 pediatric patients (19 male and 11 female) ranging in age from 4 days to 15 years (11 < or = 1 month old) have undergone orthotopic cardiac transplantation at our institution. Indications included idiopathic cardiomyopathy (n = 8), hypoplastic left heart syndrome (n = 13), and other forms of complex congenital heart disease (n = 9). There have been four operative and three late deaths only in the groups with hypoplastic left heart syndrome and other forms of complex congenital heart disease. Cumulative survival is 77% after a mean follow-up of 30 months (range, 6 to 77 months). Three operative deaths were attributable to pulmonary hypertension, and the other was due to pulmonary hemorrhage. Two late deaths were secondary to allograft rejection, and the third was due to infection. There has been uniform survival in the group with idiopathic cardiomyopathy, and intermediate-term survival rates are 78% and 62% in the groups with complex congenital heart diseases and hypoplastic left heart syndrome, respectively (p = 0.15). Although longer-term results are necessary, orthotopic cardiac transplantation appears to be an acceptable mode of therapy for endstage heart disease in the pediatric age group and technically can be performed despite complex malformations of the great arteries or atria.

Adolescent↗
PubMed1994

Feasibility of generating hemodynamic pressure curves from noninvasive Doppler echocardiographic signals.

OBJECTIVES: This study was designed to determine the feasibility of Doppler generation of accurate, complete right ventricular and pulmonary artery pressure curves in patients with Doppler-measurable tricuspid and pulmonary regurgitation. BACKGROUND: Doppler-derived flow velocities have been used to assess right ventricular systolic pressure; pulmonary artery systolic, diastolic and mean pressures, and left ventricular systolic and diastolic pressures. Instantaneous gradient across any area of discrete narrowing is accurately derived using the simplified Bernoulli equation (4V2). Invasive catheterization is currently the only means of generating intracardiac pressure curves. Noninvasively derived pressure curves using Doppler echocardiography would be a considerable advance in the assessment of normal and pathologic cardiac hemodynamics. METHODS: Right ventricular and pulmonary artery pressure curves were generated in 18 of 22 patients with measurable tricuspid and pulmonary valve regurgitation using superimposition of Doppler-measured tricuspid and pulmonary valve blood flow velocities on an assumed right atrial pressure. Doppler-measured right ventricular and pulmonary artery pressure curves were compared with simultaneous catheterization-measured curves. RESULTS: Doppler-derived pulmonary artery systolic pressure (Doppler PAP) correlated with simultaneous catheter-measured pulmonary artery pressure (Cath PAP) by the equation Doppler PAP = 0.92(Cath PAP) + 4.5, r = 0.98. Other Doppler-derived pressure measurements that correlated at near identity with the catheterization-measured corresponding measurement include Doppler-derived pulmonary artery mean pressure (Doppler mean PAP) [Doppler mean PAP = 0.85(Cath mean PAP) + 2.6, r = 0.97], and Doppler-derived right ventricular pressure (Doppler RVP) [Doppler RVP = 0.84(Cath measured RVP) + 7.9, r = 0.98]. Doppler-derived pulmonary, artery diastolic pressure (Doppler PAP diast) did not correspond as well in this study [Doppler PAP diast = 0.45(Cath PAP diast) + 6.6, r = 0.83]. CONCLUSIONS: Clinically usable right ventricular and pulmonary artery pressure curves can be derived by superimposing Doppler-measured tricuspid and pulmonary valve blood flow velocities in patients with tricuspid and pulmonary valve regurgitation.

Blood Flow Velocity↗
PubMed1992

Cost effective EMIT assays, for drugs of abuse in urine, using the Eppendorf EPOS analyser.

Laboratories with an increasing work load of drug abuse testing require high turnover techniques at low cost. Syva's EMIT system is suitable for modification onto modern automated instrumentation and, with reagent dilution, costs can be significantly reduced. We describe the modification of these assays onto the Eppendorf EPOS analyser which can process 300 samples an hour at a cost of 13p per test.

Cost-Benefit Analysis↗
PubMed1991

Adenocarcinoma of the small intestine in Crohn's disease: a unique finding.

Development of adenocarcinoma of the small bowel is rare. We present this report of a patient with a long-standing history of Crohn's disease who was found to have the 95th reported case of adenocarcinoma developed in the presence of Crohn's. The unique feature of this case is the finding of two distinctly separate carcinomas in the same surgical specimen. With report of this case and a review of the literature, certain characteristics are presented in hopes of raising suspicions sufficiently to detect this malady at an earlier stage.

Adenocarcinoma↗
PubMed1990

Congenital aneurysm of the left atrial wall in infancy.

A 5-month-old male infant with congenital left atrial aneurysm is reported. The youngest patient previously reported was 2 1/2 years old. This case is unusual because the patient was an infant and because of the degree of mitral insufficiency and acute cardiac decompensation observed in the patient.

Heart Aneurysm↗
PubMed1989

A capillary column gas-chromatographic method for the identification of drugs of abuse in urine samples.

This paper describes the application of capillary column gas liquid chromatography (GLC) to the analysis of urine samples for drugs of abuse. A simple basic extraction into butylacetate is followed by temperature programmed analysis from 90 degrees C to 310 degrees C to provide a comprehensive screen for basic drugs. Retention data are presented for approximately 300 compounds. The use of capillary column GLC is compared with packed column methods used previously in this laboratory. The reproducibility of retention data and sensitivity of this analysis for several commonly encountered drugs are presented.

Chromatography, Gas↗
PubMed1988

Management of asymptomatic intracardiac missiles using echocardiography.

A child sustained a low-velocity airgun pellet injury to the left ventricle. No cardiovascular compromise was produced. The foreign body was localized by two-dimensional echocardiography to the left ventricular chamber near the mitral valve, and subsequently removed through a left atriotomy incision. In asymptomatic patients, missiles clearly embedded within a chamber wall may be observed; all others should be removed. Two-dimensional echocardiography is recommended for localization.

Child↗
PubMed1985

Surgery for discrete subvalvular aortic stenosis: actuarial survival, hemodynamic results, and acquired aortic regurgitation.

Discrete membranous subaortic stenosis (DMSS) accounts for 8 to 30% of congenital left ventricular outflow obstruction. The immediate effectiveness of surgical resection of this discrete obstructing membrane has been well documented, but little has appeared regarding late clinical and hemodynamic follow-up. Fifty-three patients with DMSS underwent operation at our institution from 1957 to 1983. Most (78%) were symptomatic, 79% had left ventricular hypertrophy (LVH) by electrocardiogram, and 92% had roentgenographic evidence of cardiomegaly preoperatively. Catheterization revealed a mean preoperative left ventricular-aortic gradient of 89 mm Hg. Twenty-eight patients had associated aortic insufficiency (AI) on the initial aortogram. Seven patients acquired AI in the interim between the first and second preoperative catheterization. Our patients have been followed for up to 12 years postoperatively. There have been 2 early and 3 late deaths. (Actuarial analysis revealed 5- and 10-year survival of 95% and 83%, respectively.) Seventy-one percent of the previously symptomatic patients noted relief of their preoperative complaints, and 45% of those with LVH had a regression in voltage. Cardiomegaly as determined by chest roentgenogram decreased in 45%. The left ventricular-aortic gradient fell to an average of 35 mm Hg a year postoperatively. Surgical treatment of congenital subvalvular aortic stenosis is effective in reducing the preoperative symptoms and the left ventricular-aortic gradient. It appears that DMSS causes AI.

Actuarial Analysis↗
PubMed1984

Albumin influences sulfobromophthalein transport by hepatocytes of each acinar zone.

To determine whether profiles of decreasing concentration were generated among hepatocytes of the liver acinus during the transport of sulfobromophthalein sodium (BSP), rat livers were perfused with various concentrations of this dye (10 microM to 1 mM) in the presence and absence of albumin. After steady-state conditions for the biliary secretion of BSP had been attained, pieces of liver were rapidly frozen. Following the alkalinization of cryostat-cut sections, the relative concentration of BSP in hepatocytes of each zone and the effect of albumin on this localization were quantitated by microspectrophotometry. The results showed that BSP, perfused in the absence of albumin, was efficiently extracted by the liver (95% on a single pass), generating distinct profiles of decreasing cellular concentration from zone 1 to zone 3 at every concentration of BSP. However, the addition of albumin to the perfusate greatly reduced the extraction of BSP from the sinusoidal compartment and resulted in the abolition of the differences in BSP content between hepatocytes of zone 1 and zone 3. These results represent a direct demonstration that, as predicted by mathematical modeling, binding of BSP to albumin indeed results in a more homogeneous distribution of BSP within the liver acinus. A simple and direct microspectrophotometric method is therefore available to follow the changes in the relative concentration of BSP among the hepatocytes of the various acinar zones.

Animals↗
PubMed1984

Acute trazodone poisoning: clinical signs and plasma concentrations.

A total of 70 patients presenting with suspected acute trazodone poisoning were notified to the Poisons Unit (National Poisons Information Service for England) from August 1980 until March 1983. Detailed follow-up information was obtained on 41 patients, 22 of whom were thought to have ingested trazodone alone. In these latter patients drowsiness (11), ataxia (5), nausea/vomiting (4) and dry mouth (2) were the manifestations of toxicity reported most frequently, only 2 patients became unconscious (grade 2 or 3 coma), and all recovered uneventfully with no more than minimal supportive therapy. The presence of trazodone was confirmed in 8 out of 9 patients from whom specimens (blood and urine) were received. The highest plasma trazodone concentrations (15 and 19 mg/l, respectively) were both associated with only drowsiness and ataxia. However, in 2 further patients moderate plasma trazodone concentrations (4.2 and 8.2 mg/l, respectively) were associated with deep (grade 3-4) coma, although 1 of these latter patients had also ingested ethanol (plasma concentration 3.0 g/l). Although acute trazodone poisoning does not appear to be associated with cardiac arrhythmias or convulsions, these results emphasise that drowsiness and ataxia are commonly encountered, while coma may occur in severe cases. The possible contribution of metabolites of trazodone to toxicity and the potentiating effect of co-ingested drugs or alcohol must be remembered.

Adolescent↗