Prognosis with asymptomatic pulmonary nodules.
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Humans↗
Biomedical subjects
M Mehta
Publications and source records attributed to M Mehta.
Usefulness of endothelin-1 as a predictor of response to head-up tilt-table testing in children with syncope.
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Adolescent↗
Ankylosing spondylitis: lateral approach to spinal anaesthesia for lower limb surgery.
We describe three patients with long-standing ankyolsing spondylitis (AS) who underwent lower limb joint surgery under spinal anaesthesia. At preoperative assessment, it was considered that intubation of the trachea was likely to be difficult or impossible and previous general anaesthesia was associated with increased morbidity. Midline approach spinal anaesthesia failed but the lateral approach was successful. Spinal anaesthesia was induced using a 24 gauge Sprotte (Pajunk) needle with 3.5 ml heavy bupivacaine 0.5% at the L3-4 interspace with the patients in the sitting position. This resulted in adequate sensory blockade for the surgical procedure. None of the patients required airway interventions but equipment and aids to secure airway were available.
Adult↗
Neuropsychological deficits in tests of executive function in asymptomatic and symptomatic HIV-1 seropositive men.
There has been much debate about the exact nature and time of onset of the cognitive impairments associated with infection by the human immunodeficiency virus type 1 (HIV-1). Studies to date have not reached consistent conclusions. The present study comprised 22 asymptomatic and 18 symptomatic HIV-1 seropositive men, whose only risk factor for contraction of the virus was sexual intercourse, and 18 seronegative controls matched for age and IQ. Subjects were given computerized neuropsychological tests from the CANTAB battery, which assessed visuospatial memory, attention and executive function. Both the asymptomatic and the symptomatic HIV-1 seropositive subjects showed a selective pattern of deficits relative to the controls. In addition, the seropositive subjects were subtly but significantly impaired on tests of executive function but unimpaired on certain tests of visual memory. This finding supports an hypothesis that frontostriatal dysfunction occurs in HIV-1 infected individuals prior even to the expression of clinical symptoms.
Adult↗
Metal corrosion of tracheostomy apparatus.
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Bronchography↗
The minimum alveolar concentration of isoflurane in patients undergoing bilateral tubal ligation in the postpartum period.
BACKGROUND: The minimum alveolar concentration (MAC) of volatile anesthetics is decreased during pregnancy, but MAC in the early postpartum period has not been reported. The aim of this study was to determine the MAC of isoflurane and to evaluate the relation between MAC and serum progesterone and beta-endorphin in patients after delivery. METHODS: Eight patients undergoing elective bilateral tubal ligation during general anesthesia in the early postpartum period (< 12 h postpartum) and eight patients undergoing this procedure in the late postpartum period (12-25 h postpartum) were studied. Eight patients undergoing bilateral tubal ligation more than 6 weeks after delivery served as control subjects. Anesthesia was induced with propofol and maintained with isoflurane in oxygen to a steady end-tidal concentration of 0.8-1.0 vol% for 10 min. Reaction to a standardized electric stimulation applied to the forearm was graded as positive (gross or delayed movement) or negative. By using the bracketing technique, the concentration of isoflurane was increased or decreased by 0.1 vol%, depending on the positive or negative responses. RESULTS: The MAC (mean +/- SD) in patients in the early postpartum period was significantly less (0.75 +/- 0.17 vol%) than that in control subjects (1.04 +/- 0.12 vol%; P < 0.01) and that in patients in the late postpartum period (0.95 +/- 0.2 vol%; P < 0.05). The difference in MAC values between late postpartum and control was not significant (P > 0.05). There was an inverse correlation between progesterone concentration postpartum and time after delivery (r = -0.527; P = 0.036), but P = 0.744). There was no correlation between plasma progesterone or beta-endorphin and MAC by multiple regression (r = 0.166; P = 0.950). CONCLUSIONS: Isoflurane MAC remains 28% less than normal within the 1st 12 h postpartum and then returns to normal 12-25 h after delivery.
Adult↗
Family response to paranoid and non-paranoid schizophrenic patients.
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Adolescent↗
Current radiosurgery practice: results of an ASTRO survey. Task Force on Stereotactic Radiosurgery, American Society for Therapeutic Radiology and Oncology.
PURPOSE: Although there is increasing interest in radiosurgery, little quantitative data regarding current patterns of radiosurgery practice are available. We developed a radiosurgery questionnaire to obtain information on radiosurgery practice. METHODS AND MATERIALS: We distributed the questionnaire to the entire membership of the American Society of Therapeutic Radiology and Oncology in early 1993. Responses were obtained from 74 facilities that practice radiosurgery, corresponding to over 6000 treatments carried out since 1983 by 135 radiation oncologists and 130 physicists. RESULTS: Most respondents were found to work within a multidisciplinary team, consisting of the following specialists (average hours devoted per patient on day of treatment in parentheses): radiation oncologist (3.8), neurosurgeon (3.2), physicist (6.1), radiologist (0.7), nurse (2.7), other (3.0). On average, neurosurgeons and nurses who perform Gamma Knife radiosurgery devote significantly more time-per-patient on the day of treatment than their peers who perform linac radiosurgery. On average, less experienced radiation oncologists and physicists (< or = 24 months experience, or < or = 50 patients treated) devote significantly more time-per-patient on the day of treatment than their more experienced peers. Although there are many more linac radiosurgery facilities than Gamma Knife facilities, on average the number of patients treated per month per facility is significantly larger at the latter. On average, follow-up responsibilities are nearly equally shared by radiation oncologists and neurosurgeons, except at Gamma Knife facilities, where neurosurgeons assume a larger percentage of follow-up responsibility. The percentages of patients treated at linac facilities for metastases or primary CNS malignancy are larger than the corresponding percentages at Gamma Knife facilities; the opposite is true for arteriovenous malformation, acoustic neuroma, and meningioma. CONCLUSION: Current radiosurgery practice usually involves a team approach, with participation of specialists from radiation oncology, neurosurgery, physics, radiology, and nursing. The average number of M.D. and Ph.D. hours required per treatment on the day of radiosurgery is high.
Canada↗
Laparoscopic gastrojejunostomy: a case presentation.
Laparoscopic gastrojejunostomy is demonstrated as an alternative to open gastric bypass procedures. We performed the operative procedure safely and with reasonable anesthesia time, using stapling devices. It is hoped that further patient benefit will be obtained from this laparoscopic procedure in the future.
Adenocarcinoma↗
Treatment of arteriovenous malformations with stereotactic radiosurgery employing both magnetic resonance angiography and standard angiography as a database.
Twenty-one arteriovenous malformations were prospectively evaluated using magnetic resonance angiography and compared with stereotactic angiography. The goals were to establish the feasibility of magnetic resonance angiography, compare it to stereotactic angiography, employ magnetic resonance angiography in follow-up, and semiquantify flow. A correlative evaluation between flow and response to stereotactic radiosurgery was carried out. Phase contrast angiograms were obtained at flow velocities of 400, 200, 100, 60, and 20 cm/sec. The fractionated velocities provided images that selectively demonstrated the arterial and venous components of the arteriovenous malformations. Qualitative assessment of the velocity within the arteriovenous malformations and the presence of fistulae were also determined by multiple velocity images. In addition, 3-dimensional time-of-flight magnetic resonance angiograms were obtained to define the exact size and shape of the nidus. This technique also permitted evaluation of the nidus and feeding arteries for the presence of low flow aneurysms. Correlation between the two imaging modalities was carried out by subjective and semiquantitative estimation of flow velocity and estimation of nidus size. The following velocity parameters were employed: fast, intermediate, slow, and none (arteriovenous malformation obliterated). In 19 of 21 (90.5%) arteriovenous malformations, magnetic resonance angiography was equal or superior to stereotactic angiography for flow quantification and visualization of the nidus. Only 2 of 21 arteriovenous malformations were better demonstrated by stereotactic angiography than by magnetic resonance angiography (failure rate of 9.5%). The nidus size in one case was clearly underestimated by stereotactic angiography and would have resulted in a geographic miss without magnetic resonance angiography. Seven post-radiosurgery arteriovenous malformations were evaluated for follow-up with both magnetic resonance angiography and stereotactic angiography. In 6 of 7 arteriovenous malformations, magnetic resonance angiography response matched stereotactic angiography response. Correlation of flow with outcome was carried out for 14 arteriovenous malformations using magnetic resonance angiography only. Interestingly, all nine arteriovenous malformations with intermediate or slow flow demonstrated partial or complete obliteration; whereas only 3 of 5 fast flow arteriovenous malformations achieved a response with a median follow-up of 10 months. This early analysis suggests that slower flowing arteriovenous malformations may obliterate faster after stereotactic radiosurgery and flow parameters could be employed to predict response. In conclusion, magnetic resonance angiography permits semiquantitative flow velocity assessment and may therefore be superior to stereotactic angiography. An additional advantage of magnetic resonance angiography is the generation of serial transverse images which can replace the conventional CT scan employed for stereotactic radiosurgery treatment planning.(ABSTRACT TRUNCATED AT 400 WORDS)
Cerebral Angiography↗
Pharmacokinetic evaluation of drug interactions with anti-human immunodeficiency virus drugs. VI. Effect of the calcium channel blocker nimodipine on zidovudine kinetics in monkeys.
Coadministration of zidovudine (AZT) and nimodipine, a calcium-channel blocker, is a potential therapeutic regimen in acquired immunodeficiency syndrome patients based on the report that nimodipine can prevent human immunodeficiency virus-induced neurotoxicity in vitro. An evaluation of the pharmacokinetics of AZT and its glucuronide metabolite 3'-azido-3'-deoxy-5'-O-beta-D-glucopyranurosylthymidine (GAZT) in the presence and absence of nimodipine in monkeys was undertaken. After 20 mg/kg of AZT given i.v. in the presence and absence of nimodipine, nimodipine caused a significant reduction (41%) in the volume of distribution of AZT at steady state and a 22% decrease in total clearance. The disposition of GAZT was also influenced by nimodipine, causing a large increase in its area under the plasma concentration-time curve. Renal excretion data for AZT and GAZT, although inconclusive, suggested nimodipine caused a decrease in the renal clearance of AZT with a minimal change in the renal clearance of GAZT. The combined effects of nimodipine on the clearance of AZT and volume of distribution at steady state produced no change in its elimination half-life.
Animals↗
Effect of vehicle on skin penetration and retention of a lipophilic red tide toxin (PbTx-3).
The purpose of this study was to determine the effect of carrier vehicle on the penetration of brevetoxin ([3H]PbTx-3) into skin layers and receptor fluid. Disks of guinea-pig skin were mounted on penetration chambers. Epidermal surfaces were dosed with 0.320 microgram/cm2 of PbTx-3 dissolved in 50 microliters of vehicle [water, methanol, or dimethylsulfoxide (DMSO)]. In vitro skin penetration by PbTx-3 during 24 hr of exposure was 6.2, 2.3 and 26% for water, methanol, and DMSO, respectively (expressed as % of dose applied).
Animals↗
Comparison of the partition coefficient and skin penetration of a marine algal toxin (lyngbyatoxin A).
Lyngbyatoxin A is produced by marine algae, and causes local cutaneous toxicity in swimmers. The purpose of this research was (1) to determine the partition coefficient of lyngbyatoxin A in octanol/water and (2) to use methods in vitro to measure the penetration and distribution of lyngbyatoxin A in guinea pig and human skin. Discs of excised guinea pig and human skin were mounted in diffusion chambers that exposed the epidermal surface to air and bathed the dermis with HEPES-buffered Hanks' balanced salt solution with gentamicin sulphate. The epidermal surfaces were dosed with 26 micrograms lyngbyatoxin A/cm2 dissolved in 13 microliters dimethyl sulphoxide/cm2. The diffusion chambers were incubated at 36 degrees C for varying periods (1.0-24 hr). HPLC was used to quantify lyngbyatoxin A. Skin penetration was calculated by summing the amount of lyngbyatoxin A recovered from the dermis and receptor fluid. The mean partition coefficient for lyngbyatoxin A was 1.53. Penetration of lyngbyatoxin A (expressed as a percentage of dose, n = 3) in guinea pig and human skin was 23 and 6.2 (respectively) after 1 hr of topical exposure. The amount of lyngbyatoxin A in the dermis and receptor fluid did not change significantly over time.
Animals↗
Sequential comparison of low dose rate and hyperfractionated high dose rate endobronchial radiation for malignant airway occlusion.
A pilot trial (S2) was conducted at the University of Wisconsin to determine the feasibility, efficacy, and toxicity of hyperfractionated high dose rate endobronchial radiation. To avoid multiple bronchoscopies, an optimized hyperfractionated schema was derived from the linear-quadratic model. Utilizing a single bronchoscopy, 31 patients with malignant airway occlusion received 4 Gy x 4 fractions over 2 days at 2 cm from source center using a high dose rate remote afterloader. Response and morbidity were compared to a previous trial (S1) in which 66 patients were treated with conventional low dose rate endobronchial radiation. Response was assessed by change in performance status, symptom resolution, percent of lifetime rendered symptom-free or improved, and radiographic reaeration. These parameters were highly comparable between the two groups. The mean ECOG performance status improved from 2.2 to 1.8 for S1 and 2.1 to 1.6 for S2; symptom improvement or resolution was noted in 78% for S1 and 79% for S2; lifetime rendered symptom-free or improved was 54% for S1 and 57% for S2; and the overall radiographic response rate was 78% for S1 and 85% for S2. The overall incidence of fistulae was 7/101. We conclude that endobronchial radiation is an effective and safe modality for palliation, and hyperfractionated high dose rate endobronchial radiation achieves responses similar to low dose rate endobronchial radiation with a similar complication rate.
Airway Obstruction↗
Weight consideration in the use of cerrobend beam blocks.
The technique of using customized field blocking to protect sensitive normal tissue during megavoltage radiation treatment is common practice in modern radiation therapy. The introduction of CT-based treatment planning has revolutionized customized field shaping. We carried out a prospective evaluation of 54 cerrobend blocks during a one-month time period. The goals of this study were to analyze the specific block patterns and correlate these with field size, block weight, and field setup. Factors contributing to excessively large and heavy cerrobend blocks defined as > or = 20 lbs. were identified. Twenty-two percent of blocks were found to be excessively large and one-third of these were a consequence of planning decisions. A review of these situations suggests that alternative methods would have avoided the excessive weight. Concerns have been raised regarding the safety of large and heavy cerrobend blocks. These blocks were therefore analyzed in terms of tray sag and tray break-point. Our data suggest that within this clinical range of block weight, neither tray sag nor tray break-point are of significant concern.
Humans↗
Pharmacokinetic evaluation of drug interactions with anti-human immunotrophic virus (HIV) Drugs. III. 2',3'-Dideoxycytidine (ddC) and zidovudine in monkeys.
A pharmacokinetic evaluation of a potential drug interaction between zidovudine (AZT) and dideoxycytidine (ddC) was conducted in monkeys. Each of six animals received 20 mg/kg of AZT intragastrically in the absence and presence of an intravenous steady-state dosage regimen of ddC. The regimen was designed to produce steady-state ddC plasma concentration of 1.77 micrograms/ml for 30 min. Plasma and urine samples were analyzed for AZT, its major glucuronide metabolite, GAZT, and ddC by HPLC techniques. Pharmacokinetic parameters for AZT and GAZT were calculated by non-compartmental methods. The mean apparent clearance of AZT was 1.40 and 1.78 L/hr/kg in the absence and presence of ddC, respectively. The mean AUC for GAZT was 36.39 micrograms-hr/ml in the absence of ddC and 28.81 micrograms-hr/ml in the presence of ddC. No statistical differences were found in these and other pharmacokinetic parameters in the absence and presence of ddC. The absence of an effect on AZT's pharmacokinetics by ddC is attributed to the primary metabolic and renal elimination pathways for AZT and ddC, respectively. The results of this study provide a rational basis to design combined AZT-ddC treatment regimens in AIDS patients.
Animals↗
Effect of stimulus contrast on simultaneous steady-state pattern reversal electroretinogram and visual evoked response.
We studied the effect of stimulus pattern contrast on the simultaneously recorded pattern reversal electroretinogram (PERG) and pattern reversal visual evoked response (PVER) at 5 check sizes. The stimulus contrast ranged from 24 to 95% in 6 steps of 0.1- or 0.15-log unit increments. PERG amplitude showed a linear increase with an increase in pattern contrast at all check sizes. PVER amplitude showed an increase up to a certain pattern contrast, but was saturated upon further increase in stimulus contrast at all check sizes. The PERG amplitude-check size function curve showed a flattened, inverted-U shape only with the highest contrast and low-pass filter shape or flat shape with lower contrasts. The PVER amplitude-check size function curve showed an inverted-U shape (bandpass filter shape) at all contrasts. These characteristics to the changes in contrast and the spatial frequency tuning suggest that PVER is processed in a different location of visual pathway than PERG.
Adult↗
Methods for in vitro skin absorption studies of a lipophilic toxin produced by red tide.
The penetration and distribution of [3H]PbTx-3 into pig skin was determined using in vivo and in vitro methods. The dose used in each topical study was 0.3-0.4 micrograms/cm2 skin, with dimethylsulfoxide as the vehicle. In the in vivo study, mean cutaneous absorption after 48 h (expressed as percentage of the dose) was 11.5% (n = 3). In the in vitro study, mean cutaneous absorption after 48 h was 1.6% (n = 12), when based on accumulation of radioactivity in receptor fluid, or 9.9% when based on receptor fluid and dermis. [3H]PbTx-3 readily penetrated through the epidermis into the dermis, reaching maximal dermal accumulation at 4 h (9.1% in vivo and 18% in vitro). At 24 h, the amount in the dermis decreased to 2.3% and 15% in vivo and in vitro, respectively and at 48 h the amount in the dermis decreased to 8.2% in vitro. These results demonstrate the important role of the dermis as a reservoir for a lipophilic compound in both in vivo and in vitro percutaneous absorption studies.
Administration, Topical↗