Regional vascular responses to thromboxane A2 analogue and their blockade with vapiprost, a selective thromboxane receptor blocking drug, in anesthetized dogs.

Regional vascular responses to the thromboxane A2 analogue U46619 and effects of the selective thromboxane receptor blocking drug vapiprost on these responses were examined in anesthetized dogs. Hemodynamic responses to U46619 (0.5 micrograms/kg into the left atrium), norepinephrine (NE, 0.3 microgram/kg, i.v.) and angiotensin II (AII, 30 or 60 ng/kg, i.v.) were periodically tested before and after administration of vapiprost (10, 30 or 100 micrograms/kg, i.v.) or its vehicle. In the absence of vapiprost, U46619 increased total peripheral (TPR), vertebral (VR), coronary (CR) and renal (RR) vascular resistance by 60.1 +/- 4.7%, 33.6 +/- 4.9%, 15.3 +/- 1.3% and 120.8 +/- 17.4%, respectively, indicating that vasoconstrictor responses to U46619 were most prominent in the renal vascular bed as compared to those in the vertebral or coronary vasculatures. Vapiprost as well as the vehicle did not affect the base-line hemodynamics. However, vapiprost apparently inhibited the U46619-induced vasoconstriction in all measured vascular beds in a dose-related manner without attenuating vasoconstrictor responses to NE compared to the inhibitions of VR and CR. These results demonstrate that there was a regional difference both in the vasoconstrictor responses to U46619 and in the blocking effects of vapiprost, and indicate that vapiprost is a potent and selective antagonist for thromboxane receptors in vivo.     

Primary staging of laryngeal and hypopharyngeal cancer: CT,MR imaging and dual-energy CT

Laryngeal and hypopharyngeal cancer, in particular T4a disease associated with cartilage invasion and extralaryngeal spread, needs to be evaluated accurately because treatment can impact heavily on a patient's quality of life. Reliable imaging tools are therefore indispensible. CT offers high spatial and temporal resolution and remains the preferred imaging modality. Although cartilage invasion can be diagnosed with acceptable accuracy by applying defined criteria for combinations of erosion, lysis and transmural extralaryngeal spread, iodine-enhanced tumors and non-ossified cartilage are sometimes difficult to distinguish. MR offers high contrast resolution for images without motion artifacts, although inflammatory changes in cartilage sometimes resemble cartilage invasion. With dual-energy CT, combined iodine overlay images and weighted average images can be used for evaluation of cartilage invasion, since iodine enhancement is evident in tumor tissue but not in cartilage. Extralaryngeal spread can be evaluated from CT, MR or dual-energy CT images and the routes of tumor spread into the extralaryngeal soft tissue must be considered; (1) via the thyrohyoid membrane along the superior laryngeal neurovascular bundle, (2) via the inferior pharyngeal constrictor muscle, and (3) via the cricothyroid membrane. Radiologists need to understand the advantages and limitations of each imaging modality for staging of laryngeal and hypopharyngeal cancer.     

Lymph nodes of patients with regional metastases from head and neck squamous cell carcinoma as a predictor of pathologic outcome: size changes at CT before and after radiation therapy

BACKGROUND AND PURPOSE: Viable tumor in a neck dissection specimen is important in predicting prognosis and directing treatment. Our purpose was to clarify the importance of size changes of regional metastases from head and neck squamous cell carcinoma on CT scans obtained before and after radiation therapy (RT) as a predictor of pathologic outcome. METHODS: Thirty-seven heminecks in 34 patients who underwent pre-RT CT, RT, post-RT CT, and post-RT neck dissection were reviewed. Thirteen hemineck specimens were pathologically positive. Decrease ratios of the largest axial dimension of the lymph nodes between the pre- and post-RT CT studies were calculated. RESULTS: Six of 37 heminecks had a decrease ratio greater than 50%. These yielded negative specimens after planned neck dissection. In two of 37 heminecks, the largest axial dimension of the largest node increased between studies, resulting in negative decrease ratio. One (decrease ratio, -20%) had a positive specimen, and the other (decrease ratio, -3%) had a negative specimen. No interval change in size in the largest node was noted in one of the 37 heminecks; its specimen was positive. Average decrease ratios were 41.2% (range, -3% to 62%) in the negative specimen group (n = 24) and 27.2% (range, -20% to 50%) in the positive specimen group (n = 13). Univariate analysis revealed that the decrease ratio was not a significant predictor of a positive surgical specimen (P =.154). CONCLUSION: Heminecks in which the decrease ratio was greater than 50% tended to have a negative surgical specimen. However, this trend was not statistically significant.     

Beneficial hemodynamic effects of nicorandil in a canine model of acute congestive heart failure: Comparison with nitroglycerin and cromakalim

Summary— Comparative hemodynamic effects of nicorandil (NCR), nitroglycerin (NTG) and cromakalim (CRM) were examined in a canine model of acute congestive heart failure (CHF). CHF was produced by injections of saponin into coronary arteries of anesthetized dogs followed by volume loading and continuous iv infusion of methoxamine. After the treatment, aortic blood flow (AoF), left ventricular d P /d t and myocardial segment shortening (SS) markedly decreased, while the left ventricular end-diastolic pressure (LVEDP), the right atrial pressure (RAP) and the systemic vascular resistance (SVR) increased. NCR ( n = 6), NTG ( n = 6) and CRM ( n = 8), which were administered iv after production of CHF, caused a comparable reduction in LVEDP. NCR and CRM profoundly increased AoF and SS but NTG did only slightly. On the other hand, NTG and NCR but not CRM significantly reduced RAP. Intracoronary NCR ( n = 8) exerted no or similar effects on SS as well as systemic hemodynamic indices to those observed with iv NCR despite distinct coronary vasodilation. These results indicate that NCR may exert beneficial hemodynamic effects in an experimental CHF mainly due to lessening both afterload and preload rather than the coronary vasodilating effect.     

Effect of polyoxyethylene-modified superoxide dismutase on recovery of myocardial dysfunction after coronary stenosis in dogs

The effects of superoxide dismutase modified with polyoxyethylene (SOD-POE) on impairment of myocardial segment shortening (SS) during coronary stenosis plus pacing-induced tachycardia (CSPT) and the recovery after reperfusion was examined in anesthetized dogs. SOD-POE or saline was administered i.v. 30 min before reperfusion. Changes in hemodynamic variables and SS by CSPT were similar in both groups. However, the SOD-POE group showed improved recovery of SS compared with the control group. Results indicate that oxygen-derived free radicals may partially be involved in the genesis of myocardial dysfunction after CSPT-induced regional ischemia.     

Post-RT CT results as a predictive model for the necessity of planned post-RT neck dissection in patients with cervical metastatic disease from squamous cell carcinoma

PURPOSE: To establish whether the extent of neck disease on postradiation therapy (RT) computed tomography (CT) can predict the likelihood of positive neck nodes and, thereby, the necessity of planned post-RT neck dissection. METHODS AND MATERIALS: Ninety-five patients who underwent post-RT neck dissection within 2 months for squamous cell carcinoma of the head and neck were eligible. Of the 95 patients, 37 (32.7%) of 113 hemineck specimens were pathologically positive. On post-RT CT imaging studies, the number and size of lymph nodes >1 cm were recorded. Internal focal defects and the likelihood of extracapsular spread were graded. RESULTS: If lymph nodes on post-RT CT were < or = 15 mm, free of significant internal focal low-attenuation or calcification, and without imaging evidence of extracapsular spread, the surgical hemineck specimen was positive in 1 (3.4%) of the 29 hemineck specimens. A focal low-attenuation defect (p = 0.0078) and evidence of extracapsular spread (p = 0.0721) seen in the residual nodal mass on CT were independent predictors of a positive surgical specimen by multivariate analysis. CONCLUSION: CT findings on post-RT neck studies can help predict the likelihood of residual disease and, thereby, the necessity of planned post-RT neck dissection.     

Comparative studies of the systemic hemodynamics and myocardial oxygen consumption of FRC 8653, a new Ca++ channel blocker, and nifedipine in anesthetized dogs.

Effects of FRC 8653, a new dihydropyridine derivative, on regional blood flow, cardiac function and myocardial oxygen consumption were examined and compared with those of nifedipine in anesthetized open-chest dogs. Intravenous administration of FRC 8653 at doses of 1, 3 and 10 micrograms/kg dose-dependently decreased aortic pressure and increased aortic, vertebral and coronary blood flow similar to nifedipine. No significant change was observed in left ventricular end-diastolic pressure, left ventricular positive dP/dt and heart rate following i.v. administration of FRC 8653. Myocardial oxygen consumption was dose-dependently decreased by FRC 8653. When changes in mean aortic pressure and aortic and coronary blood flow were compared at the same dose of 10 micrograms/kg i.v., both FRC 8653 and nifedipine showed almost the same degree of reduction of mean aortic pressure, but the time from drug administration to peak responses and the duration for which half the maximal effects were maintained, were significantly longer with FRC 8653 than nifedipine. Results suggest that FRC 8653 may be useful for the treatment of patients with hypertension and ischaemic heart disease.     

Pediatric retropharyngeal lymphadenitis: differentiation from retropharyngeal abscess and treatment implications.

OBJECTIVES: Our objectives were to review the retropharyngeal anatomy, define retropharyngeal adenitis and abscess, and determine if CT may guide the clinician in treatment planning for pediatric retropharyngeal infections. STUDY DESIGN AND SETTING: A retrospective chart review and CT scan review of 30 children with retropharyngeal infections. RESULTS: All patients had retropharyngeal adenitis. Average volume of the low-attenuation focus in the medical treatment group was 1.2 cm3. Average volume in the surgical group was 4 cm3. Surgery patients with no purulent findings were then grouped with the medical treatment group; the average volume of the low-attenuation focus in this group was 2.2 cm3. Average volume in the group in which purulence was identified was 4.4 cm3. CONCLUSION: CT can identify patients with retropharyngeal infections who have a high likelihood of being successfully treated with antibiotics alone. SIGNIFICANCE: CT imaging may assist in avoiding unnecessary surgical exploration.