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Biomedical subjects

D Lea

Publications and source records attributed to D Lea.

10 recordsLinked to original sources
PubMed2000

Natural variation in the essential oil content of Melaleuca alternifolia Cheel (Myrtaceae).

The composition and yield of oil in 615 trees representing the natural populations of Melaleuca alternifolia, or tea tree, was investigated. A sixth distinct oil chemotype was identified. Of the six chemotypes, one chemotype is dominated by terpinen-4-ol, one by 1,8-cineole, one by terpinolene and the remaining three chemotypes are all dominated by 1,8-cineole and differ in either terpinen-4-ol or terpinolene content. Whilst most chemotypes are present throughout the distribution range, a definite correspondence of oil types with geographic location was found. Terpinen-4-ol types predominate in and around the Bungawalbin basin in the Casino area of northern New South Wales (NSW), high 1,8-cineole types predominate toward the southern end of the distribution around Grafton and terpinolene types predominate in southern Queensland. Preliminary formulae have been developed to allow comparisons of oil data obtained by steam distillation with a static headspace gas chromatography method.

Journal Article↗
PubMed1997

Evaluation of an approach to choosing a left double-lumen tube size based on chest computed tomographic scan measurement of left mainstem bronchial diameter.

OBJECTIVE: Evaluation of an approach to choosing left double-lumen tube size based on chest computed tomographic (CT) scan measurement of left bronchial diameter. DESIGN: Prospective. SETTING: The operating rooms of a university hospital. PARTICIPANTS: Patients scheduled for elective thoracic surgery. INTERVENTIONS: Patients had their left bronchial diameter measured on the preoperative chest CT scan. Left double-lumen tube size for the individual patient was chosen from a protocol based on left bronchial diameter. MEASUREMENTS AND MAIN RESULTS: The double-lumen tube size was considered appropriate for the patient if some air leak was detected when the bronchial cuff was deflated and if airtight seal of the left bronchus was obtained with a bronchial cuff volume of 2 mL or less. In 17 of 20 patients, the double-lumen tube size fulfilled both criteria. In 3 women with left bronchi measuring 10 mm or less, the bronchus was sealed without any air in the bronchial cuff of size 35 Fr left double-lumen tubes. In 1 patient, who was excluded from the study, the double-lumen tube size was chosen based on measurement of the left bronchial diameter on chest radiograph because of motion artifact on the chest CT scan. CONCLUSIONS: Chest CT scan measurement of left bronchial diameter can successfully guide the choice of left double-lumen tube size for an individual patient. In individuals with a small left bronchus measuring less than 10.0 mm in diameter, currently available adult double-lumen tube sizes will tightly wedge in their bronchus.

Adult↗
PubMed1997

Nursing research 'down under'.

1. The major constraints preventing psychiatric nurses from conducting research are lack of time and knowledge. 2. Nurses can be motivated to explore the possibility of conducting research without having necessary skills or knowledge to start. 3. The nursing profession must face its responsibility to support and nurture nurses' interests in conducting and using research.

Adult↗
PubMed1994

The pharmacokinetics of propofol in children using three different data analysis approaches.

BACKGROUND: Accurate dosing of propofol in children requires accurate knowledge of propofol pharmacokinetics in this population. Improvement in pharmacokinetic accuracy may depend on the incorporation of individual patient factors into the pharmacokinetic model or the use of population approaches to estimating the pharmacokinetic parameters. We investigated whether incorporating individual subject covariates (e.g., age, weight, and gender) into the pharmacokinetic model improved the accuracy. We also investigated whether the use of a mixed-effects population model (e.g., the computer program NONMEM) improved the accuracy of the pharmacokinetic model beyond the accuracy obtained with models estimated using two simple approaches. METHODS: We studied 53 healthy, unpremedicated children (28 boys and 25 girls) ranging from 3 to 11 yr of age. Twenty children only received an initial loading dose of 3 mg/kg intravenous propofol. In the remaining 33 children, an initial intravenous propofol dose of 3.5 mg/kg was followed by a propofol maintenance infusion. Six hundred fifty-eight venous plasma samples were gathered and assayed for propofol concentrations. Three different regression techniques were used to analyze the pharmacokinetics: the "standard two-stage" approach, the "naive pooled-data" approach, and the nonlinear mixed-effects modeling approach (as implemented in NONMEM). In both the pooled-data and mixed-effects approaches, individual covariates (age, weight, height, body surface area, and gender) were added to the model to examine whether they improved the quality of the fit. Accuracy of the model was measured by the ability of the model to describe the observed concentrations. RESULTS: The pharmacokinetics of propofol in children were best described by a three-compartment pharmacokinetic model. There were no appreciable differences among the pharmacokinetics estimated using the two-stage, pooled-data, and mixed-effects approaches. Weight was a significant covariate, and the weight-proportional model was supported by all three regression approaches. The pharmacokinetic parameters of the weight-proportional pharmacokinetic model (pooled-data approach) were: central compartment (V1) = 0.52 1 x kg-1; rapid-distribution compartment (V2) = 1.01 x kg-1; slow-distribution compartment (V3) = 8.2 1 x kg-1; metabolic clearance (Cl1) = 34 ml.kg-1 x min-1; rapid-distribution clearance (Cl2) = 58 ml.kg-1 x min-1; and slow-distribution clearance (Cl3) = 26 ml.kg-1 x min-1. The inclusion of age as an additional covariate of V2 statistically improved the model, but the actual improvement in the fit was small. CONCLUSIONS: The pharmacokinetics of propofol in children are well described by a standard three-compartment pharmacokinetic model. Weight-adjusting the volumes and clearances significantly improved the accuracy of the pharmacokinetics. Adjusting the pharmacokinetics for inclusion of additional patient covariates or using a mixed-effects model did not further improve the ability of the pharmacokinetic parameters to describe the observations.

Child↗
PubMed1992

Has outpatient quality assurance improved performance?

A prospective study of the outpatient department was undertaken as part of a quality assurance initiative to improve patient care. Senior managers and clinicians set realistic performance targets for attendances, availability of records, waiting times and delay in correspondence to general practitioners. From February 1989 to January 1990, performance was analysed each month, and data and subsequent management changes publicised. The results show improvements in all areas studied, which supports the generally held belief that clinicians wish to improve the care offered to patients.

Appointments and Schedules↗
PubMed1989

Sufentanil and alfentanil pattern of consumption during patient-controlled analgesia: a comparison with morphine.

Pattern of drug consumption and side effects of sufentanil and alfentanil were compared to morphine, using "on-demand" patient-controlled analgesia (PCA). After a non-narcotic general anesthetic, a bolus dose of the narcotic was given intravenously towards the end of surgery. PCA was started in the recovery room. Data were retrieved postoperatively for a total of 24 h. Results showed a wide range of pattern of drug consumption and uniform acceptance of therapy by the nurses and the patients in all the groups. The frequency of use of incremental doses was greater than 2-2.5-fold for the sufentanil and alfentanil groups, respectively, compared with morphine. The bolus dose of the narcotics failed to achieve adequate analgesia for 2 h for morphine and sufentanil and for 6 h for alfentanil. Overall patients were most sedated with morphine and least sedated with sufentanil. At the time intervals sampled, there was a higher incidence of oxygen desaturation--less less than 95% with morphine and alfentanil, compared with sufentanil. There was a similar incidence of nausea in all the groups. Further study is needed to determine precisely the best dose regimens for sufentanil and alfentanil, especially in reference to optimum loading doses. Sufentanil appears to be a promising drug for PCA use.

Acute Disease↗
PubMed1988

Predicting hospital charges for trauma care.

Diagnosis related groups (DRGs) have sharply decreased the amount of compensation hospitals can expect for providing trauma care. A total of 637 patients admitted for acute traumatic injuries between Oct 1, 1985, and July 30, 1986, had their DRG classifications, Injury Severity Scores, trauma scores, and ages compared with hospital charges in an attempt to identify factors that could be used to accurately predict hospital charges. The best prediction of charges was obtained when DRG assignment was combined with Injury Severity Scores and age. When the equation obtained by this approach was applied to a separate population of 301 patients, the average difference between the actual charge and that predicted was $38 and would have led to a 33-fold decrease in money lost by the hospital. Altering the DRG payment schedule as proposed would allow hospitals to be fairly compensated for the care of trauma patients.

Adolescent↗
PubMedDate not supplied

Pharmacodynamic effects of three doses of ORG 9426 used for endotracheal intubation in humans.

STUDY OBJECTIVE: To determine the pharmacodynamic characteristics of three incremental doses of ORG 9426 used for endotracheal intubation in patients. DESIGN: Double-blind, randomized administration of one of three doses of intravenous ORG 9426. SETTING: Inpatients requiring surgery at Georgetown University Medical Center. PATIENTS: Thirty-six patients, ages 18 to 65, ASA physical status I, II, and III, scheduled for general surgery. INTERVENTIONS: After Georgetown University Institutional Review Board approval and patient consent, patients were premedicated with midazolam or droperidol. Anesthesia was induced with thiopental sodium and fentanyl. Anesthesia was maintained with 60% nitrous oxide in oxygen. The ulnar nerve was stimulated supramaximally with a 2 Hz train-of-four (TOF) every 20 seconds. Thumb contractions were measured with a force transducer. When TOF and anesthesia were stable, 2, 2.5, or 3 times the ED95 of ORG 9426 (570 micrograms/kg, 710 micrograms/kg, or 850 micrograms/kg) was administered randomly. Tracheal intubation was attempted at maximal depression of the first TOF response (T1). MEASUREMENTS AND MAIN RESULTS: The following parameters were measured: time interval from the injection of ORG 9426 to 90% depression of T1 (T1 90% block), maximal T1 depression (onset time), intubating conditions, clinical duration (time for return of T1 to 25% of control), heart rate (HR), blood pressure (BP), and any adverse clinical experience. ORG 9426 provided adequate intubating conditions in all patients but two, independent of the dose used. Its onset time was rapid, but increasing the dose did not shorten the onset. T1 90% block was achieved rapidly (75 +/- 25 seconds to 78 +/- 18 seconds, means +/- SD). The clinical duration of ORG 9426 was relatively short and lengthened with increasing doses (from 36 +/- 18 minutes at 570 micrograms/kg to 42 +/- 10 minutes at 850 micrograms/kg. Spontaneous twitch recovery from 10% to 25% was similar in all dosage groups (5 +/- 1 minutes to 6 +/- 4 minutes). No clinically significant changes in HR and BP and no adverse clinical experiences were noted in any group. CONCLUSION: These findings warrant further clinical evaluation of ORG 9426 for induction and maintenance of muscle relaxation in humans.

Adolescent↗