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Biomedical subjects

H D Nguyen

Publications and source records attributed to H D Nguyen.

32 records · Page 2Linked to original sources
PubMed1994

MR of fetal central nervous system abnormalities.

PURPOSE: To investigate whether MR can provide additional information on fetuses with central nervous system abnormalities as demonstrated by ultrasonography. METHODS: Fetal MR examinations were studied prospectively in 22 pregnant women whose fetuses showed evidence of anomalies on ultrasound performed in the High-Risk Obstetric Clinic. RESULTS: In 19 of 22 cases, postpartum confirmatory diagnoses were obtained by MR or CT examinations, autopsy, or surgery. In general, the image quality of MR is comparable with that of ultrasound. However, in six of 22 cases (27%), MR provided additional information that altered the ultrasound diagnosis; these included cases of infarction, diastematomyelia, normal hemimegalencephaly with early myelination, Dandy-Walker variant, and lipoma. All of these cases had postpartum confirmation. The additional information changed the treatment in three of six patients (no intervention or elective abortion). CONCLUSIONS: In certain situations MR can add valuable information to that obtained by sonography in the evaluation of the fetal central nervous system.

Central Nervous System↗
PubMed1992

Postoperative atrial fibrillation in cancer surgery: preoperative risks and clinical outcome.

Postoperative atrial fibrillation (AF) is a recognized complication of cancer surgery. The purpose of this study was to define preoperative risk factors for AF, and to evaluate the clinical significance of the arrhythmia. We reviewed the medical records of 43 patients with postoperative AF admitted to the surgical intensive care unit (SICU). All patients were older than 60 years, 79% had a history of cigarette smoking, and 44% had hypertension. AF occurred an average of 2.8 days following surgery, and lasted an average of 2.1 days. No significant complications developed, and there were no long-term sequelae. This study suggests that, in cancer patients, postoperative AF is a disease of elderly patients. In addition the arrhythmia appears to be a relatively transient and benign phenomenon. Prolonged monitoring in an intensive care setting may not be necessary for asymptomatic, hemodynamically stable patients.

Aged↗
PubMed1992

The application of contrast agents in the evaluation of neoplasms of the central nervous system.

Magnetic resonance evaluation of central nervous system neoplasms has improved tremendously since the introduction of gadolinium-based contrast agents. The optimal application of these agents in clinical imaging, however, has not been well established. The article discusses the recent application of these agents to a number of intracranial neoplasms, including metastases, gliomas, pituitary adenomas, and acoustic neurinomas/cerebellopontine angle tumors.

Brain Neoplasms↗
PubMed1991

The neuromuscular effects of ORG9426 in patients receiving balanced anesthesia.

In searching for a nondepolarizing muscle relaxant with intermediate duration but more rapid onset of action than the presently available compounds, the neuromuscular and circulatory effects of ORG9426 were investigated in two studies in humans receiving fentanyl, droperidol, thiopental, and nitrous oxide-oxygen anesthesia. Eighty patients, randomly assigned to one of four groups of 20 each, received 0.12, 0.16, 0.20, or 0.24 mg/kg ORG9426. In the first study, the doses (in milligrams per kilogram) of ORG9426 that caused 50% (ED50), 90% (ED90), or 95% (ED95) neuromuscular block were determined by the individual dose-response method; they were 0.170, 0.268, and 0.305 mg/kg, respectively. In the second study, after induction of anesthesia, patients received 0.6 mg/kg (about 2 x ED95) of ORG9426, either in a single bolus (group 1) or in two unequal (0.1 and 0.5 mg/kg) increments 4 min apart (group 2). After the administration of 0.6 mg/kg ORG9426, maximal neuromuscular block developed in 1.5 +/- 0.12 min in group 1 and in 1.2 +/- 0.14 min in group 2. Patients tracheas were intubated after development of the maximal neuromuscular effect of the intubating dose and after the recording of heart rate and systolic and diastolic blood pressure. There was no difference in the clinical duration of the intubating doses, which were 40.0 +/- 3.2 (15-73) min in group 1 and 39.3 +/- 2.4 (19-57) min in group 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Neuromuscular and cardiovascular effects of pipecuronium.

Pipecuronium bromide (Arduan) is a bisquaternary, steroid-type neuromuscular blocking agent in clinical use in Eastern Europe. Before its introduction into clinical practice in the USA, in the first phase of this study the neuromuscular potency of pipecuronium was determined under "balanced" and enflurance anaesthesia by the cumulative log dose-response method in 30 patients each. In the second phase the intubation and onset times, clinical duration of the first and repeated doses, spontaneous recovery index, reversibility of its residual neuromuscular effect by an anticholinesterase and its effect on heart rate and blood pressure was compared with the same variables observed in patients, anaesthetized with identical techniques but who had received vecuronium or pancuronium. The neuromuscular potency of pipecuronium was greater under enflurane (ED95 = 23.6 +/- 1.1 micrograms.kg-1 (mean +/- SEM)] than under balanced (ED95 = 35.1 +/- 17 micrograms.kg-1) anaesthesia. Pipecuronium was more potent than vecuronium under both balanced (ED95 = 45.8 micrograms.kg-1) and enflurane anaesthesia (ED95 = 27.4 micrograms.kg-1). Following the administration of 2 x ED95 doses there were no clinically significant differences in the intubation or onset times of pipecuronium, vecuronium and pancuronium. Under balanced anaesthesia the clinical duration of 2 x ED95 dose of pipecuronium (110.5 +/- 0.3 min) or pancuronium (115.8 +/- 8.1 min) were similar and about three times longer than that of vecuronium (36.3 +/- 2.1 min). The recovery indices of pipecuronium (44.5 +/- 8.2 min) and pancuronium (41.3 +/- 4.2 min) were also similar and about three times longer than that of vecuronium (14.3 +/- 1.4 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

A simple method for monitoring muscular relaxation during continuous infusion of vecuronium.

There is considerable individual variation in the dose of vecuronium required for the maintenance of surgical relaxation. Therefore to provide uninterrupted relaxation without overdosage it is advisable to regulate the IV infusion of vecuronium on the basis of appropriate monitoring. Monitoring with mechanomyography (MMG) or electromyography requires costly equipment and is too complex for routine clinical use. Visual observation of the adductor pollicis muscle contracting against zero resistance is not suitable for the reliable assessment of the degree of neuromuscular (NM) block. For clinical purposes satisfactory monitoring can be achieved with the simple device (Myoscan) described. The reliability of the Myoscan was tested in 30 patients by simultaneous monitoring of the force of contraction of the adductor pollicis on one side with the Myoscan and on the contralateral side with the MMG. Retrospective analysis of the MMG indicated that the conduct of anaesthesia would have been virtually the same if it would have been based on MMG monitoring.

Adult↗
PubMedDate not supplied

MR imaging of ventriculomegaly--a qualitative and quantitative comparison of communicating hydrocephalus, central atrophy, and normal studies.

Both communicating hydrocephalus and central atrophy cause ventricular dilatation. However, patients with hydrocephalus may require treatment. The aim of this study was to assess qualitatively and quantitatively the efficacy of MR imaging in the differentiation of communicating hydrocephalus from central atrophy. The midsagittal T1-weighted MR images of 33 patients with communicating hydrocephalus, 31 patients with central atrophy, and 23 normal subjects were evaluated qualitatively and quantitatively. This included configuration of the aqueduct; area of the septum pellucidum, third ventricle, and fourth ventricle; and morphology of the corpus callosum. Distal dilatation of the aqueduct was detected in 33.3% of patients with communicating hydrocephalus and in none of those with central atrophy. The corpus callosum was elevated in patients with communicating hydrocephalus when compared with that in patients with central atrophy. In conclusion, an analysis of midsagittal T1-weighted images has identified useful qualitative and quantitative criteria in the differentiation of communicating hydrocephalus from central atrophy. The configuration of the aqueduct with funneling at the fourth ventricular end strongly suggests the presence of communicating hydrocephalus rather than central atrophy alone.

Aged↗
PubMedDate not supplied

Pituitary metastases: MR findings.

Tumors metastatic to the pituitary gland are uncommon, and they are difficult to differentiate radiologically from pituitary adenomas. We retrospectively reviewed the MR examinations and clinical records of nine patients with radiographic and/or clinical evidence of pituitary metastases. The most common clinical symptoms included cranial nerve deficits (67%) and/or pituitary dysfunction (30%). Both occurred acutely and progressed rapidly over 1-4 weeks in all patients. Cranial nerve involvement was predominantly multiple (83%), a reflection of involvement of the adjacent cavernous sinus. In contrast to previous reports indicating a predilection for symptoms related to posterior lobe involvement (71%), our study shows that symptoms related to the anterior lobe are as common as posterior lobe symptoms. Useful MR findings included a relatively small, enhancing pituitary lesion (< or = 1.5 cm in 56%) that was relatively isointense to brain on both T1- and T2-weighted images (78%) and involvement of the hypothalamus/pituitary infundibulum (44%) or cavernous sinus (56%).

Adult↗
PubMedDate not supplied

MR evaluation of acoustic schwannoma with fractional contrast doses.

OBJECTIVE: To investigate the utility of lower contrast medium doses for the detection and conspicuity of acoustic schwannomas. MATERIALS AND METHODS: The L/B (L, lesion; B, background) ratios or lesion contrast of 17 pathologically proven acoustic schwannomas studied with a standard dose (0.1 mmol/kg) of gadopentetate dimeglumine was measured. In addition, 22 patients with acoustic schwannomas were studied prospectively with fractional doses using the incremental dose technique. Each patient received an initial bolus injection of one-eight the standard dose (0.0125 mmol/kg) followed by an injection of one-eighth, one-fourth, and one-half the standard dose at 5 min intervals to achieve a cumulative dose of one-fourth, one-half and full dose, respectively. Imaging was performed immediately after each injection. RESULTS: Standard dose--The L/B ratios of pathologically proven acoustic schwannomas to mastoid air cells ranged from 14.8 to 41.2 (mean +/- SEM, 28.0 +/- 1.95), which were approximately 17 times more than those of intraparenchymal lesions. Fractional cumulative dose--Qualitative visual analysis demonstrated that all acoustic schwannomas showed apparent enhancement at one-fourth dose. Intense enhancement was noted at one-half and full dose. Quantitative analysis demonstrated the mean L/B ratios between the acoustic schwannomas and mastoid air cells of the precontrast and one-eighth, one-fourth, one-half, and full dose studies were 8.33 +/- 0.52, 11.21 +/- 0.75, 13.02 +/- 0.83, 15.38 +/- 0.98, and 18.03 +/- 1.36, respectively. CONCLUSION: The L/B ratios or lesion contrast of acoustic schwannomas at various fractional contrast medium doses was significantly higher compared with that of intraparenchymal lesions. Thus, the standard contrast medium dose may not be necessary for detection of acoustic schwannomas, and a fractional dose may be sufficient. Although the optimal fractional dose remains to be determined, one-half of the standard dose (0.05 mmol/kg) appears to be sufficient because of intense enhancement at this dose.

Contrast Media↗
PubMedDate not supplied

Cystic acoustic schwannomas: MR characteristics.

PURPOSE: To evaluate the spectrum of MR characteristics of cystic acoustic schwannoma and to investigate its incidence. METHODS: We retrospectively reviewed the MR findings and clinical records of 16 patients with cystic acoustic schwannomas. In addition, the MR examinations of 411 consecutive patients referred for clinical suspicion of acoustic schwannomas were reviewed retrospectively to assess the incidence of acoustic schwannomas with cystic lesions arising from the internal auditory canal. RESULTS: Of the 16 acoustic schwannomas with MR evidence of intramural cysts, 11 tumors had single small cysts, and five had multiple intramural cysts of variable size. Intramural cysts in 11 of the 16 tumors exhibited higher signal intensity than that of cerebrospinal fluid; the remainder were isointense to cerebrospinal fluid on both T1- and T2-weighted images. All intramural cysts showed circumferential enhancement after contrast administration. Nine of the 16 cystic acoustic schwannomas also had MR evidence of extramural/arachnoid cysts. Six of the extramural/arachnoid cysts had epicenters away from the dural interface, and the other three cysts were broadly based against the dura. The incidence of cystic acoustic schwannomas was 11.3% and association with extramural/arachnoid cysts 7.5%. CONCLUSION: Our series suggests that cystic changes in acoustic schwannomas and the association with extramural/arachnoid cysts are not as rare as previously reported by other diagnostic methods. The high signal intensity of intramural cysts is probably related to necrotic material, blood, or colloid-rich fluid. The difference in the MR characteristics of extramural/arachnoid cysts associated with acoustic schwannomas and those of typical arachnoid cysts not associated with neoplasia may be related to higher protein and/or colloid contents secreted by the tumor. Most extramural/arachnoid cysts had epicenters between the tumor and brain, suggesting that the most likely mechanism of formation is peritumoral adhesions. It creates a pseudo-duplication caused by the trapping of fluid between the leptomeninges and the mass, resulting in an acquired type of arachnoid cyst.

Adult↗