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Biomedical subjects

L A Madsen

Publications and source records attributed to L A Madsen.

7 recordsLinked to original sources
PubMed1998

Force-detected magnetic resonance without field gradients.

A novel method of nuclear magnetic resonance (NMR) is described which promises to be preferable to known general methods at sample length scales below approximately 100 microm. Its advantages stem from the seemingly paradoxical combination of a homogeneous static magnetic field and detection of a mechanical force between a spin-bearing sample and a magnet assembly. In contrast to other methods of force-detected nuclear magnetic resonance (FDNMR), the method is characterized by better observation of magnetization, enhanced resolution, and no gradient (BOOMERANG), and it is generally applicable with respect to sample composition, pulse sequence, and magnetic field strength. Further advantages of portability and low cost stem from the small instrument volume and mass and promise to extend the use of NMR to new applications and environments. A sensitivity analysis, relevant to spectroscopy or imaging, quantifies the advantage of BOOMERANG relative to magnetic induction using microcoils and to FDNMR methods that rely on large gradients of the magnetic field at the sample.

Magnetic Resonance Spectroscopy↗
PubMed1993

Treatment of 171 patients with pulmonary tuberculosis resistant to isoniazid and rifampin.

BACKGROUND AND METHODS: The frequency of infection with multidrug-resistant Mycobacterium tuberculosis is increasing. We reviewed the clinical courses of 171 patients with pulmonary disease due to M. tuberculosis resistant to rifampin and isoniazid who were referred to our hospital between 1973 and 1983. The patients' records were analyzed retrospectively. Their regimens were selected individually and preferably included three medications that they had not been given previously and to which the strain was fully susceptible. RESULTS: The 171 patients (median age, 46 years) had previously received a median of six drugs and shed bacilli that were resistant to a median of six drugs. Thus, their regimens were frequently not optimal. Of 134 patients with sufficient follow-up data, 87 (65 percent) responded to chemotherapy (as indicated by negative sputum cultures for at least three consecutive months); 47 patients (35 percent) had no response, as shown by continually positive cultures. The median stay in the hospital was more than seven months. In a multivariate analysis, an unfavorable response was significantly associated with a greater number of drugs received before the current course of therapy (odds ratio, 4.0; 95 percent confidence interval, 1.6 to 9.9; P < 0.001) and with male sex (odds ratio, 2.5; 95 percent confidence interval, 1.1 to 6.2; P < 0.03). Twelve of the patients with responses subsequently had relapses. The overall response rate was 56 percent over a mean period of 51 months. Of the 171 patients, 63 (37 percent) died, and 37 of these deaths were attributed to tuberculosis. CONCLUSIONS: For patients with pulmonary tuberculosis that is resistant to rifampin and isoniazid, even the best available treatment is often unsuccessful. Only about half of such patients eventually have negative sputum cultures despite carefully selected regimens administered for extended periods. Failure to control this resistant infection is associated with high mortality and ominous implications for the public health.

Adolescent↗
PubMed1993

Ten-year experience with artificial pneumoperitoneum for end-stage, drug-resistant pulmonary tuberculosis.

Artificial pneumoperitoneum is a form of collapse therapy that was used in the treatment of cavitary pulmonary tuberculosis before the availability of antimycobacterial chemotherapy. We report a series of cases of far-advanced pulmonary disease due to multiple-drug-resistant Mycobacterium tuberculosis, wherein artificial pneumoperitoneum with or without subsequent surgical extirpation was used as an adjunct to chemotherapy. Overall, among these desperate cases, therapeutic pneumoperitoneum provided no clear benefit.

Adult↗
PubMed1991

Chronic tuberculous empyema with bronchopleural fistula resulting in treatment failure and progressive drug resistance.

We treated five patients with a past history of tuberculous pleural infection that led to chronic, quiescent, loculated empyema. Reactivation of TB was associated with formation of BPF and recovery of drug-susceptible Mycobacterium tuberculosis from sputum. All patients had recurrence of positive sputum cultures that yielded tubercle bacilli resistant to drugs they were receiving. The lungs demonstrated gross thickening with calcification of both visceral and parietal pleura. Two patients underwent retreatment chemotherapy followed by decortication-empyemectomy and lung resection surgery; both are now culture-negative for TB. One patient received retreatment chemotherapy but refused surgery; he remains clinically stable with negative sputum cultures. Two other patients' organisms became drug-resistant and they remain sputum-culture positive. We believe that thick, calcified pleural walls limit penetration of drugs into the infected empyema space, resulting in suboptimal drug concentrations and drug resistance. Intensified chemotherapy and surgical intervention should be considered in these cases.

Aged↗
PubMed1989

Drug-resistant tuberculosis.

Multiply resistant tuberculosis is on the rise throughout the world. It poses the risk that an increasing percentage of patients will have disease that cannot be cured in economically limited nations and, thus, resistant tubercle bacilli will be spread in an exponential manner. For such patients in the United States, aggressive chemotherapy, coupled with surgery in cases of localized disease, is the best hope for cure.

Adult↗