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Biomedical subjects

D Hamilton

Publications and source records attributed to D Hamilton.

At least 37 records · Page 2Linked to original sources
PubMed1999

Prevention of tracheal aspiration using the pressure-limited tracheal tube cuff.

A new design of tracheal tube cuff, the pressure-limited cuff, used with a constant-pressure inflation system, was compared with a high-volume low-pressure cuffed tracheal tube for leakage of dye placed in the subglottic space into the trachea. Patients requiring ventilation on the intensive care unit were randomly allocated into two groups, one for each type of cuff, and blue food dye was instilled daily via a fine catheter above the cuff into the subglottic space. There were eight patients in the high-volume low-pressure group and seven in the pressure-limited cuff group. Dye leaked into the trachea in seven (87%) of the high-volume low-pressure group compared with none (0%) of the pressure-limited cuff group (p < 0.01). This study demonstrates that the pressure-limited cuffed tracheal tube, in combination with a constant-pressure inflation device, prevents leakage of fluid into the lungs that occurs with high-volume low-pressure cuffs in the critically ill, intubated patient.

Air Pressure↗
PubMed1999

Efficacy and complications of morphine infusions in postoperative paediatric patients.

The aim of the study was to evaluate the efficacy and the incidence of clinically significant adverse drug reactions (ADRs) in paediatric patients receiving continuous intravenous morphine infusions for acute postoperative pain. Definitions were established for ADRs and data were collected in an immediately retrospective fashion for a maximum of 72 h in 110 patients >/=5 three months of age (0.3-16.7 years) receiving morphine infusions and admitted to a general ward over a three month convenience sampling period. Inadequate analgesia occurred in 65.5% of patients during the first 24 h of therapy and occurred most frequently in patients with infusion rates of 20 microg.kg-1.h-1 or less. Nausea/vomiting was the most commonly experienced ADR (42.5%). The incidence of respiratory depression was 0% (95% CI=0-3.3%). Other ADRs included: urinary retention (13.5%), pruritus (12.7%), dysphoria (7.3%), hypoxaemia (4.5%), discontinuation of morphine for treatment of an ADR (3.6%), and difficulty in arousal (0.9%). The most common ADRs associated with morphine infusions were inadequate analgesia (in the first 24 h) and nausea/vomiting. There were no cases of respiratory depression. Methods of avoiding initial inadequate analgesia and treating nausea and vomiting associated with morphine infusions are needed.

Acute Disease↗
PubMed1999

The diagnosis of segmental transplant renal artery stenosis by captopril renography.

The captopril renogram test has been shown to be a sensitive test for the diagnosis of renal artery stenosis in native and transplanted kidneys. Most reports have involved only stenosis of the main renal artery. Although segmental renal artery stenosis has been diagnosed successfully in native kidneys, it is not clear whether the captopril renogram test can diagnose segmental renal artery stenosis in a transplanted kidney. The authors report two cases of successful identification, by the captopril renogram test, of functionally significant stenosis in an intrarenal branch of a single transplant renal artery.

Adult↗
PubMed1999

Body surface area correction in single-sample methods of glomerular filtration rate estimation.

Single-sample methods of estimating glomerular filtration rate (GFR) are used routinely, in a number of institutions, to calculate values of total plasma clearance (TPC), which are then converted to GFR. Adjustment of the final estimate for body surface area (BSA) is not adequate to allow adult equations to be used in children and work has been undertaken to seek an age-independent technique. The aim of this study was to evaluate the ability of an alternative method of correcting for BSA, of scaling the plasma sample activity, to achieve an age-independent solution. The accuracy of the scaled TPC values was compared with a monoexponential analysis as the 'gold' standard. Data from 60 patients were analysed using 16 single-sample models. Patients were chosen so that 10 could be allocated to each of six categories involving three age groups (0-3 years, 4-17 years and 18+ years) and two classes of TPC (< 40 and > 40 ml.min-1). Adjustment of the plasma activity gave more accurate results than correction of the final estimate in 87% of the categories for 15 of the models. This improvement was particularly apparent in the case of adult equations applied to child data, which gave results similar to those obtained using child equations, indicating that they can be used with equal accuracy.

Adolescent↗
PubMed1998

Mutations in the pore regions of the yeast K+ channel YKC1 affect gating by extracellular K+.

The product of the Saccharomyces cerevisiae K+-channel gene YKC1 includes two pore-loop sequences that are thought to form the hydrophilic lining of the pore. Gating of the channel is promoted by membrane depolarization and is regulated by extracellular K+ concentration ([K+]o) both in the yeast and when expressed in Xenopus oocytes. Analysis of the wild-type current now shows that: (i) [K+]o suppresses a very slowly relaxing component, accelerating activation; (ii) [K+]o slows deactivation in a dose-dependent fashion; and (iii) Rb+, Cs+ and, to a lesser extent, Na+ substitute for K+ in its action on gating. We have identified single residues, L293 and A428, at equivalent positions within the two pore loops that affect the [K+]o sensitivity. Substitution of these residues gave channels with reduced sensitivity to [K+]o in macroscopic current kinetics and voltage dependence, but had only minor effects on selectivity among alkali cations in gating and on single-channel conductance. In some mutants, activation was slowed sufficiently to confer a sigmoidicity to current rise at low [K+]o. The results indicate that these residues are involved in [K+]o sensing. Their situation close to the permeation pathway points to an interaction between gating and permeation.

Cations, Monovalent↗
PubMed1998

Auxin-induced stress potentiates trans-activation by a conserved plant basic/leucine-zipper factor.

The promoter element activation sequence-1 (as-1) confers tissue-specific and signal-responsive transcription in plants. Hormone and chemical stress cues are thought to activate as-1-dependent transcription through specific basic/leucine-zipper proteins, termed TGA factors, that bind this element. We report here that a highly conserved TGA factor of tobacco, TGA1a, can selectively activate transcription in response to micromolar concentrations of auxin hormones or their analogs. This induction is chemically specific, as a range of other compounds tested at similar concentrations had little or no effect. Auxin was found to augment the trans-activation potential of TGA1a through carboxyl-terminal residues. The amino-terminal domain of TGA1a, by gain-of-function assays, was found to both constitutively activate transcription and maximize the response to auxin. Further evidence indicates that the trans-activation potential of this domain in TGA1a is repressed, under basal conditions, by carboxyl-terminal residues. Because TGA1a and endogenous TGA factors are stimulated by auxin only at concentrations that inhibited cell growth, this response is likely to involve chemical stress.

Basic-Leucine Zipper Transcription Factors↗
PubMed1998

Quadrupled semitendinosus-gracilis autograft fixation in the femoral tunnel: a comparison between a metal and a bioabsorbable interference screw.

Although semitendinosus-gracilis (SG) grafts for anterior cruciate ligament reconstruction have many potential benefits, effective fixation remains a challenge. This study assessed differences between the maximum pullout forces needed to detach a quadrupled SG graft from a femoral tunnel when secured by either a metal or a bioabsorbable interference screw. Sixteen paired fresh frozen quadrupled SG autografts (x, 8.4 mm; range, 7-10 mm) from 8 donors were anchored into cadaveric femoral tunnels by either a 7-mm metal or a 7-mm bioabsorbable screw after bone mineral density (BMD) assessment and before undergoing a longitudinal 20 mm/min traction force. Statistical analysis compared BMD (gm/cm2), insertional torque (N-m), and maximum load at pullout (N) between screw types. Insertional torques (.28-1.21, N-m range) did not correlate (P>.05) to BMD or maximum load at pullout (x +/- S.D.) 242 +/- 90.7 N (metal screw) and 341.1 +/- 162.9 N (bioabsorbable screw). Differences did not exist between the maximum load at pullout for bioabsorbable or metal screw fixation (P = .16). Careful graft preparation, sizing, and matched tunnel placement enables interference fit and fixation capable of reliably withstanding the low-level rehabilitation loads to which the graft is exposed until bony ingrowth occurs.

Absorption↗
PubMed1998

Two lyophilized polymer matrix recombinant human bone morphogenetic protein-2 carriers in rabbit calvarial defects.

We have developed a lyophilized bone morphogenetic protein (BMP) delivery device that can be formulated to control release over 2 to 8 weeks. Bioerodible poly (d,l lactide-co-glycolide) particles loaded with 90 micrograms recombinant human BMP-2 were suspended in either carboxymethylcellulose (CMC) or methylcellulose (MC) implants. Plain CMC and MC implants served as controls, as did a nonimplanted group. A total of 40 rabbits was evaluated histologically 2, 4, or 8 weeks after receiving circular full-thickness 15-mm calvarial defects. MC appeared to prevent prolapse of periosteum and dura into the defects and did not elicit bone growth. Addition of BMP improved the result. CMC implants appeared to encourage bone growth even in the absence of BMP. When BMP was added, new bone formed earlier. CMC may influence new bone formation because it is hydrophilic. MC is less hydrophilic and may cause undue inflammation. Either can be combined with BMP to produce unitary devices that are easy to make and use.

Animals↗
PubMed1998

Sleep studies of adults with severe or profound mental retardation and epilepsy.

Sleep patterns of people with mental retardation have received little research attention. This is an important gap in knowledge because understanding the relation between sleep and wakefulness may be critical to care provision. Descriptive sleep information on 28 people with severe or profound mental retardation and epilepsy was presented here. Sleep EEG data, studied both conventionally and by means of a neural network-based sleep analysis system suggest atypical sleep stages with significant depletion of REM sleep and a predominance of "indiscriminate" non-REM sleep. Sleep diaries completed by caregivers reveal lengthy sleep period times, especially among those with profound mental retardation. Possible explanations for these results and their implications were discussed.

Adolescent↗
PubMed1997

Classification of mild Alzheimer's disease by artificial neural network analysis of SPET data.

An evaluation of the performance of artificial neural networks (ANNs) for the classification of probable Alzheimer's disease (pAD) patients was undertaken using data extracted from four regions of interest constructed on single photon emission tomographic (SPET) cerebral perfusion images. Two studies using feed-forward neural networks (FFNNs) were undertaken. The first was to determine if it would be possible to classify pAD patients and normal subjects in a mixed group, comprising 29 patients diagnosed as having pAD varying in severity from mild, established dementia to moderate dementia and 10 healthy control subjects. The second was to determine if the networks generated in the first study could prospectively classify 15 additional patients with very mild or mild cognitive impairment. The results were compared to those obtained using the same data and discriminant analysis. The relative performances of the two analysis techniques were assessed on the basis of the area under receiver operating characteristics (ROC) curves. The FFNN successfully classified all datasets in the first study, achieving an area under the ROC curve of 1.00, whereas discriminant analysis achieved 0.94. When tested on data from the second group, the areas under the ROC curves varied between 0.86 and 1.00 for the FFNN, whereas that for discriminant analysis was 0.99. We conclude that FFNNs can accurately classify pAD patients with mild to moderate dementia using data obtained from SPET cerebral perfusion images.

Aged↗
PubMed1997

Seat belt injuries and sigmoid colon trauma.

Colonic seat belt injuries are rare but carry higher mortality rates than small bowel injuries. The case of a 44 year old man is described who had severe sigmoid colon compression injury from his seat belt a few days after a road traffic accident.

Accidents, Traffic↗
PubMed1997

Toward a theory of social pharmacology: the actor-spectator paradox applied to the psychotropic prescribing process.

Traditionally, drug prescribing was regarded as part of the physician's decision-making role. However, recently it has been recognized that such a perspective is insufficient to understand the psychotropic prescribing process. To understand this process, a drug communication perspective is necessary. This article describes the actor-spectator paradox and its influence on drug communication and psychotropic drug prescribing. The actor-spectator paradox postulates that the actor and the spectator have divergent perspectives about the cause of the actor's behavior. The spectator makes assumptions about the actor's cognitive system other than the actor herself is making. This difference is often the basis for misunderstandings between a health professional and a patient. If a health professional can learn to make more realistic assumptions about a patient's cognitive system, communication between the two will improve. In the same way a patient has to learn to make more realistic assumptions about the cognitive systems of health professionals. The actor-spectator paradox can be applied to different areas of Social Pharmacology such as the diagnosis of patients suffering from mental health problems, drug compliance, informed consent, and the prescribing of psychotropics.

Decision Making↗
PubMed1997

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Education, Nursing, Baccalaureate↗