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Biomedical subjects

G Solares

Publications and source records attributed to G Solares.

At least 19 recordsLinked to original sources
PubMed1998

Propofol concentrations in whole blood: influence of anticoagulants and storage time.

Blood samples for propofol determination are collected with oxalate, heparin and EDTA, but we have not found any study comparing the influence of those anticoagulants on propofol concentrations. This study was carried out on 50 samples from patients taking propofol for anesthesia or cerebral protection. First, 26 samples were simultaneously collected into tubes containing lithium heparin or sodium fluoride potassium oxalate as anticoagulant. In a second investigation, 24 samples were simultaneously collected into tubes containing heparin or EDTA. Propofol was assayed by HPLC 2 days after sampling and 2 weeks later. In the first assay, propofol concentration in samples collected with heparin were similar to those collected with oxalate (3.65 +/- 3.50 vs. 3.62 +/- 3.49 mg/l, ns) or EDTA (3.89 +/- 2.58 vs. 3.84 +/- 2.67 mg/L, ns). After storing for 2 weeks at 4 degrees C, propofol concentrations were slightly but insignificantly higher than in the first assay in samples collected with heparin (3.58 +/- 3.24 vs. 3.40 +/- 2.92 mg/l, ns), slightly higher in samples with oxalate (3.86 +/- 3.49 vs. 3.62 +/- 3.49 mg/l, p = 0.06), and slightly but significantly lower in samples with EDTA (3.63 +/- 2.67 vs. 3.84 +/- 2.67 mg/l, p < 0.05). It is concluded that the three anticoagulants used in this study seem to be suitable for determination of propofol concentration in whole blood, and that the stability of propofol concentration when samples are stored at 4 degrees C for up 2 weeks is acceptable.

Anticoagulants↗
PubMed1996

Monte Carlo-based treatment planning for boron neutron capture therapy using custom designed models automatically generated from CT data.

PURPOSE: A Monte Carlo-based treatment planning code for boron neutron capture therapy (BNCT), called NCTPLAN, has been developed in support of the New England Medical Center-Massachusetts Institute of Technology program in BNCT. This code has been used to plan BNCT irradiations in an ongoing peripheral melanoma BNCT protocol. The concept and design of the code is described and illustrative applications are presented. METHODS AND MATERIALS: NCTPLAN uses thin-slice Computed Tomography (CT) image data to automatically create a heterogeneous multimaterial model of the relevant body part, which is then used as input to a Monte Carlo simulation code, MCNP, to derive distributions within the model. Results are displayed as isocontours superimposed on precisely corresponding CT images of the body part. Currently the computational slowness of the dose calculations precludes efficient treatment planning per se, but does provide the radiation oncologist with a preview of the doses that will be delivered to tumors and to various normal tissues, and permits neutron irradiation times in Megawatt-minutes (MW-min) to be calculated for specific dose prescriptions. The validation of the NCTPLAN results by experimental mixed-field dosimetry is presented. A typical application involving a cranial parallel-opposed epithermal neutron beam irradiation of a human subject with a glioblastoma multiforme is illustrated showing relative biological effectiveness-isodose (RBE) distributions in normal CNS structures and in brain tumors. Parametric curves for the MITR-II M67 epithermal neutron beam, showing the gain factors (gain factor = minimum tumor dose/maximum normal brain dose) for various combinations of boron concentrations in tumor and in normal brain, are presented. RESULTS: The NCTPLAN code provides good computational agreement with experimental measurements for all dose components along the neutron beam central axis in a head phantom. For the M67 epithermal beam the gain factor for 1, boronophenylalanine for a small midline brain tumor under typical distribution assumptions is 1.4-1.8 x . Implementation of the code under clinical conditions is demonstrated. CONCLUSION: The NCTPLAN code has been shown to be well suited to treatment-planning applications in BNCT. Comparison of computationally derived dose distributions in a phantom compared with experimental measurements demonstrates good agreement. Automatic superposition of isodose contours with corresponding CT image data provides the ability to evaluate BNCT doses to tumor and to normal structures. Calculation of gain factors suggests that for the M67 epithermal neutron beam, more advantage is gained from increasing boron concentrations in tumor than from increasing the boron tumor-to-normal brain ratio.

Boron Neutron Capture Therapy↗
PubMed1995

Photoaging versus intrinsic aging: a morphologic assessment of facial skin.

Histologic studies have become increasingly important in recognizing morphologic differences in photoaged versus intrinsically aged skin. Earlier histologic studies have attempted to evaluate these changes by examining anatomical sites which are not comparable, such as face and buttocks. As part of a multicenter study, we have quantitatively examined a panel of 16 histologic features in baseline facial skin biopsies from 158 women with moderate to severe photodamage. When compared to the postauricular area (photo protected), biopsies of the crow's feet area (photo exposed) had a twofold increase in melanocytes and a statistically significant increase in melanocytic atypia (p < .0001) and epidermal melanin (p < .0001). Other epidermal changes included reduced epidermal thickness (p < .01), more compact stratum corneum (p < .0001) and increased granular layer thickness (p < .0001) in the crow's feet skin. There was increased solar elastosis (p < .0001), dermal elastic tissue (p < .0001), melanophages (p < .0001), perivascular inflammation (p < .05) and perifollicular fibrosis (p < .01) but no change in the number of mast cells or dermal mucin in the photo exposed skin. Our data document quantitative differences in photoaged versus intrinsically aged facial skin and provides the groundwork for future studies to evaluate the efficacy of new treatments for photoaged skin.

Aged↗
PubMed1995

Ultrastructural effects of topical tretinoin on dermo-epidermal junction and papillary dermis in photodamaged skin. A controlled study.

We examined the effects of daily topical application of 0.05% tretinoin cream on photodamaged Caucasian facial skin by electron microscopy. Specimens obtained pretreatment, after 6 and 12 months of tretinoin therapy (20 patients), and after 6 months of vehicle treatment (5 patients) were compared in a blinded fashion, with special attention to the dermoepidermal junction and papillary dermis. Baseline specimens disclosed various degrees of damage including reduplication of basal lamina, smudging and sparsity of collagen fibers, and nodular arrangement of degenerated microfibrils in the papillary dermis. No significant changes were observed at 6 months in the papillary dermis of either tretinoin-treated or vehicle-treated patients. After 12 months of tretinoin treatment, however, disorganized collagen fibers, which were conspicuous in 11 patients at baseline, were replaced by new well-organized collagen fibers in a wavy pattern in 6 patients. In addition, the amount of nodularly degenerated microfibrillar material decreased in 15 of 18 patients with this finding at baseline. In contrast, no significant change was noted in the number of anchoring fibrils per unit length of the lamina densa. These observations provide further evidence that topical treatment with 0.05% tretinoin produces papillary dermal reconstruction, for which more than 6 months of application were required.

Administration, Topical↗
PubMed1994

Could the piggyback operation in liver transplantation be routinely used?

OBJECTIVE: To determine if orthotopic liver transplantation with inferior vena cava preservation, performed without using caval cross clamping or venovenous bypass, can minimize hemodynamic instability and low renal perfusion pressure. DESIGN: A prospective case series of 44 consecutive adult orthotopic liver transplantations, with a maximum follow-up of 30 months. SETTING: An institutional university referral center. PATIENTS: Between November 1990 and May 1993, 39 consecutive adult liver transplant recipients underwent transplantation with the following primary diagnoses: alcoholic cirrhosis (n = 23), viral cirrhosis (n = 9), primary biliary cirrhosis (n = 2), Wilson's disease (n = 2), primary sclerosing cholangitis (n = 1), fulminant hepatic failure (n = 1), and secondary hepatic malignant neoplasm (n = 1); five had repeated orthotopic liver transplantation. INTERVENTION: Orthotopic liver transplantations were performed using the piggyback technique, but with placement of the vascular clamp on the inferior vena cava laterally instead of across it so that it remained patent throughout the anhepatic stage. Favorable anatomic conditions in the recipients were not considered; venovenous bypass was not used. MAIN OUTCOME MEASURES: Intraoperative hemodynamic profile, blood loss and replacement, surgical time and complications, and patient survival. RESULTS: No significant hemodynamic changes with lateral clamping and no increases in surgical complications, rate of retransplantation, blood product requirements, or survival rate compared with the standard procedure. CONCLUSION: The piggyback operation could be routinely used in orthotopic liver transplantation.

Adult↗
PubMed1991

Proliferative inhibition of human breast carcinoma cells by high concentration estradiol does not alter radiosensitivity.

The proliferation of ER+ malignant mammary epithelial cells (MMEC), MCF-7 and T-47D, was markedly inhibited by 10 microM 17 beta-estradiol (E2), while the ER- line, MDA-MB-231, was minimally affected. This concentration of E2 did not alter the proportion of non-viable cells or the plating efficiency. The decrease in proliferation was not associated with any consistent alteration in the cell kinetic profile between lines, though there was clearly no dominant cell cycle re-assortment after a two day incubation. Colony forming ability after exposure to ionizing irradiation was compared for proliferating and confluent MMEC to cells incubated in 10 microM E2 for two days. The presence of E2 resulted in no significant differences for any of the linear quadratic curve fitting parameters or for mean inactivation doses for both subconfluent and confluent cultures. Further, 10 microM E2 had no effect on the ability of cells to recover from split radiation fractions. There were no differences in the amount of DNA single strand break induction with E2, but there was a significant shortening in the repair halftime with E2 for the ER- MDA-MB-231 cells. Though high concentrations of E2 can markedly inhibit the proliferation of ER+ MMEC, this does not alter sensitivity to ionizing irradiation.

Breast Neoplasms↗
PubMed1987

Carcinoid syndrome and intravenous cyproheptadine.

The anaesthetic management of a patient with the carcinoid syndrome is reported. Important cardiovascular complications occurred immediately after tracheal intubation and during manipulation of metastases. Hypertensive crises were controlled with intravenous cyproheptadine, although hypotension and drowsiness were observed due to its use.

Aged↗
PubMed1987

Epidural analgesia for post-caesarean pain relief: a comparison between morphine and fentanyl.

In 20 post-operative patients who had undergone caesarean section, morphine 2 mg or fentanyl 75 micrograms in 0.9% saline were given epidurally in a randomized study, to compare their effectiveness in providing post-operative pain relief and the incidence of untoward reaction. There was a faster onset of action (P less than 0.01) and the quality of pain relief was substantially better after epidural fentanyl (P less than 0.01). However, the duration of action was markedly longer after epidural morphine (P less than 0.01). There was a significantly greater incidence of urinary retention after morphine administration (P less than 0.05). It is suggested that fentanyl gives better relief of pain than morphine when given epidurally.

Analgesia↗
PubMed1986

Amiodarone, phaeochromocytoma and cardiomyopathy.

The anaesthetic management of a patient with a phaeochromocytoma and cardiomyopathy is described. The control of dysrhythmias was the major problem. Ventricular dysrhythmias were treated with lignocaine, and intravenous amiodarone was used to control the supraventricular rhythm disturbances.

Adrenal Gland Neoplasms↗