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Biomedical subjects

N W Rizk

Publications and source records attributed to N W Rizk.

At least 19 recordsLinked to original sources
PubMed1998

Unsuspected pulmonary embolism: prospective detection on routine helical CT scans.

PURPOSE: To determine the prevalence of unsuspected pulmonary embolism (PE) on routine thoracic helical computed tomographic (CT) scans and to quantify the improvement in PE detection by using a cine-paging mode on a workstation instead of hard-copy review. MATERIALS AND METHODS: Seven hundred eighty-five patients referred for routine contrast medium-enhanced thoracic CT within 9 months were prospectively recruited. Helical CT was performed. Studies were prospectively interpreted by four radiologists. Two radiologists performed routine, undirected, hard-copy consensus review for official interpretation; two of three thoracic radiologists independently performed a dedicated workstation-based search for PE. The presence of PE involving the main, lobar, or segmental pulmonary arteries was assigned a score of 1-5 (1 = definitely negative, 5 = definitely positive) by each independent reviewer. Patients with a score of 4 or 5 underwent lower-extremity ultrasound, ventilation-perfusion scintigraphy, or both, followed by pulmonary CT angiography if the findings were still equivocal. RESULTS: Twelve (1.5%) of the 785 patients had unsuspected PE, with an inpatient prevalence of 5% (eight of 160) and an outpatient prevalence of 0.6% (four of 625). Of the 12 patients with unsuspected PE, 10 (83%) had cancer. Of the 81 inpatients with cancer, seven (9%) had unsuspected PE. A dedicated workstation-based search resulted in detection of PE in three more patients (25%) than did hard-copy interpretation. CONCLUSION: The prevalence of unsuspected PE was highest among inpatients with cancer. A directed, workstation-based search can improve the PE detection rate over that with hard-copy review.

Adolescent↗
PubMed1998

Intracranial hypotension presenting with severe encephalopathy. Case report.

A patient with severe and protracted symptoms from intracranial hypotension is described. The patient's presentation was marked by diffuse encephalopathy and profound depression of consciousness. This case report expands the presently known clinical spectrum of this uncommon and generally benign illness. The clinical and laboratory findings typically observed in the syndrome of intracranial hypotension are outlined. The pathophysiological mechanisms of the phenomenon are briefly discussed. Intracranial hypotension is a potentially severe illness with specific treatments that are distinct from the treatment of most neurological diseases. Three cardinal features--postural headache, pachymeningitis, and descent of midline cerebral structures--should prompt the diagnosis.

Adult↗
PubMed1996

Imaging in lung cancer.

The diagnosis, staging, and follow-up of lung cancer is a clinical and therapeutic challenge. Recent radiographic advances are critical to the management of patients with lung cancer. This review focuses on state-of-the-art chest imaging modalities, including plain radiography, computed tomography; magnetic resonance imaging, as well as the newest technique, positron-emission tomography, and discusses the current literature.

Diagnostic Imaging↗
PubMed1995

Preemptive ganciclovir administration based solely on asymptomatic pulmonary cytomegalovirus infection in allogeneic bone marrow transplant recipients: long-term follow-up.

The use of ganciclovir at the time of cytomegalovirus (CMV) infection but before disease onset has been termed "preemptive" therapy. This preemptive ganciclovir administration has been shown to be an effective method for preventing severe CMV disease after allogeneic bone marrow transplantation (BMT), but the optimal method of CMV surveillance is not clear. The purpose of this study was to evaluate effectiveness, side effects, and long-term outcome of preemptive ganciclovir therapy in allogeneic BMT recipients when ganciclovir is prescribed solely on the basis of CMV detection in day +35 bronchoalveolar lavage (BAL). In a consecutive cohort of 202 HLA-matched recipients of sibling donor marrow transplantations, 163 received prospective BAL and were given preemptive ganciclovir if CMV-positive; 39 had disqualifying complications and were not eligible for BAL. Over the 36-month follow-up, CMV disease occurred in 21 (10%) of the 202 BMT recipients; there was one CMV-related death. In the 60 subjects (37% of the total 163) who received preemptive ganciclovir based on positive CMV-BAL, two (3%) developed CMV disease during the first 120 days post-BMT and two more developed late disease. Among the 103 BAL-negative subjects, CMV disease occurred in eight (8%) during the first 120 days and in three (3%) at > 120 days. Forty-three percent of all CMV disease occurred either before day +35 BAL (four cases) or at late times after BMT (five cases). The negative predictive value of BAL was 91%, allowing for the occurrence of 52% of all CMV disease in subjects considered CMV-BAL-negative. Nevertheless, using this treatment method, no significant differences in neutropenia rates or in 36-month survival were noted in the high-risk group having pulmonary CMV infection (compared with the group without pulmonary CMV). Thus, a strategy of preemptive ganciclovir based on a single BAL can reduce the complications caused by CMV; however, improved surveillance methods are necessary to eliminate all CMV disease.

Antiviral Agents↗
PubMed1995

Needle, transbronchial, thoracoscopic, or open lung biopsy in interstitial lung disease.

The specific diagnosis of interstitial lung disease has conventionally been determined by lung biopsy. Lung biopsy also is useful for assessing disease activity and prognosis, and is sometimes useful in deciding on the necessity of therapy. The availability of newer biopsy techniques and the interaction of these techniques with current generation imaging modalities has changed the role of biopsy in interstitial lung disease. This review reports on the indications, techniques, and limitations of biopsy procedures and places them in the context of the use of current imaging methods, as reflected in recent literature.

Biopsy↗
PubMed1990

The diagnosis of Wegener's granulomatosis from transbronchial biopsy specimens.

It is widely believed that thoracotomy is necessary to obtain biopsy specimens adequate for the histopathologic demonstration of pulmonary Wegener's granulomatosis (WG). We report five patients with WG who were diagnosed by transbronchial biopsy (TBB). In three cases, a diagnosis of WG was made by TBB alone. In the other two patients, subsequent open lung biopsies confirmed the TBB findings but did not add essential diagnostic information. Our experience suggests TBB may be appropriate as the initial diagnostic procedure in selected cases of suspected WG. This approach requires an understanding of the diverse histologic features of WG and the correlation of clinical and pathologic data.

Adolescent↗
PubMed1987

Nonoxidative microbicidal activity in normal human alveolar and peritoneal macrophages.

Although Toxoplasma gondii multiplies within normal murine alveolar and peritoneal macrophages, it is killed by normal rat alveolar and peritoneal macrophages. The killing by rat macrophages is by a nonoxidative mechanism. Studies on normal human alveolar macrophages have reported disparate results in regard to their ability to inhibit or kill T. gondii. We considered it of interest to explore further the effect of normal human alveolar and peritoneal macrophages on T. gondii. Unstimulated alveolar macrophages from each of seven individuals demonstrated a marked ability to kill or inhibit multiplication of T. gondii in vitro (e.g., the number of parasites per 100 alveolar macrophages was 31 at time zero and 2 at 18 h, whereas this value increased from 37 at time zero to 183 at 18 h in murine macrophages assayed in parallel). In quantitative assays of superoxide, alveolar macrophages released a substantial amount of superoxide when exposed to phorbol myristate acetate or to candidae. In contrast, alveolar macrophages incubated with T. gondii released no more superoxide than when in medium alone. Scavengers of superoxide anions, hydrogen peroxide, singlet oxygen, and hydroxyl radicals failed to inhibit killing of T. gondii by alveolar macrophages. Peritoneal macrophages from each of six normal women undergoing laparoscopy killed T. gondii in vitro; results of quantitative superoxide assays and scavenger experiments demonstrated that no oxidative burst was triggered in these macrophages by exposure to T. gondii. These data indicate that normal human alveolar and peritoneal macrophages can kill an intracellular parasite by nonoxidative mechanisms and suggest that these mechanisms are important in inhibition or killing of other opportunistic intracellular pathogens.

Adult↗
PubMed1985

Selection of patients with non-small-cell lung carcinoma for surgical resection.

Cancer of the lung is rapidly increasing in incidence in both sexes and soon will overtake breast cancer as the most deadly cancer in women. Selection of patients with non-small-cell carcinoma for surgical resection is largely based on preoperative clinical staging, using the American Joint Committee on Cancer's TNM-based group staging protocol. Determining the presence or absence of mediastinal nodal metastasis is paramount and is currently best achieved by computed tomographic scanning of the chest and biopsy of enlarged nodes via mediastinoscopy. Certain types of stage III lesions, previously excluded from surgical treatment, are now recognized as operable.

Humans↗
PubMed1984

Site of deposition and factors affecting clearance of aerosolized solute from canine lungs.

We determined the influence of several factors on lung solute clearance using aerosolized 99mTc-diethylenetriaminepentaacetate. We used a jet nebulizer-plate separator-balloon system to generate particles with an activity median aerodynamic diameter of 1.1 micron, administered the aerosol in a standard fashion, and determined clearance half times (t1/2) with a gamma-scintillation camera. The following serial studies were performed in five anesthetized, paralyzed, intubated, mechanically ventilated dogs: 1) control, with ventilatory frequency (f) = 15 breaths/min and tidal volume (VT) = 15 ml/kg during solute clearance; 2) repeat control, for reproducibility; 3) increased frequency, with f = 25 breaths/min and VT = 10 ml/kg; 4) positive end-expiratory pressure (PEEP) of 10 cmH2O; 5) unilateral pulmonary arterial occlusion (PAO); and 6) bronchial arterial occlusion (BAO). Control t1/2 was 25 +/- 5 min and did not change in the repeat control, increased frequency, or BAO experiments. PEEP markedly decreased t1/2 to 13 +/- 3 min (P less than 0.01), and PAO increased it to 37 +/- 6 min (P less than 0.05). We conclude that clearance from the lungs by our method is uninfluenced by increased frequency, increases markedly with PEEP, and depends on pulmonary, not bronchial, blood flow.

Aerosols↗
PubMed1983

Mechanism of cough and bronchoconstriction induced by distilled water aerosol.

We studied the relationship between cough and bronchoconstriction caused by inhaled distilled water aerosol in 8 subjects with asthma by measuring specific airways resistance (SRaw) and recording cough while subjects breathed serially increasing volumes of distilled water or normal saline aerosol produced by an ultrasonic nebulizer. We performed the distilled water dose-response curves after no treatment and after treatment with cromolyn aerosol, lidocaine aerosol, or atropine aerosol in doses of 0.2 mg and 2.0 mg on separate days. Without prior treatment, distilled water aerosol caused cough in 7 of 8 subjects and a marked increase in SRaw in every subject, whereas saline aerosol did not cause cough or a greater than 50% increase in SRaw in any subject. The 2 doses of atropine caused an equivalent reduction in baseline SRaw, but 2.0 mg caused greater inhibition of water-induced bronchoconstriction than did 0.2 mg. Neither dose of atropine inhibited cough. These data suggest that water-induced bronchoconstriction involves cholinergic nerves and that water-induced cough is not dependent on bronchoconstriction. Lidocaine inhibited cough but not bronchoconstriction, whereas cromolyn inhibited bronchoconstriction but not cough, suggesting that cromolyn does not inhibit bronchoconstriction by a generalized inhibition of airway afferent nerves.

Adolescent↗