Further studies on the mechanism of vasodepressor response in cats after intravenous administration of venom from the snake Dendroaspis jamesoni (Jameson''s mamba)

Further studies on the mechanism of vasodepressor response in cats after intravenous administration of venom from the snake Dendroaspis jamesoni (Jameson's mamba). Toxicon 15, 561–570, 1977.—Intravenous administration of Dendroaspis jamesoni venom in cats produced a biphasic vasodepressor response; an initial brief fall followed by a sustained secondary hypotension. Prior atropine administration abolished the initial hypotensive response and the secondary fall was prevented by transection of spinal cord at C₂. In spinal cord transected and atropinized animals, both vasodepressor components were absent. Chromatographic analysis of the venom provided two fractions which were eluted with normal saline and administered i.v. Fraction 1 whose migration was very close to that of acetylcholine produced a brief hypotensive response which was abolished by prior atropinization. Administration of other fraction, with slower migration characteristics, produced a sustained vasodepressor phenomenon. Five fractions of the venom were separated by starch gel electrophoresis. Of these, fraction V also caused a sustained fall in blood pressure which was abolished after transection of spinal cord (C₂). On the basis of present observations and those reported earlier, a cholinergic mediation for the initial fall in the blood pressure and a central locus of action possibly at the vasomotor centre for the sustained secondary hypotension is suggested.     

Assisted ventilation and survival of extremely low birthweight infants

Objective : To determine the incremental consumption of ventilator resources associated with the improving survival rate of extremely low birthweight (ELBW, birthweight 500–999 g) infants, from the time assisted ventilation was introduced. Methodology : Cohort study of ELBW infants born in one tertiary perinatal centre (The Royal Women's Hospital, Melbourne). All ELBW infants born from 1971 to 1993 were included in the study. Inhospital survival rates and patient-days of assisted ventilation were the main outcome measures. Discrete eras of relatively stable survival rate and consumption of ventilator resources were identified. These comprised the years 1971–74, 1977–83, 1985–90, and 1992–93. Cost-effectiveness ratios (the incremental consumption of ventilator resources per additional survivor) were calculated between adjacent eras by dividing the increment in the consumption of ventilator resources by the increment in the survival rate. Results : The survival rates rose progressively between eras (6.2, 33.9, 49.1, 68.8%, respectively, as did the consumption of ventilator resources (0.1, 6.6, 16.2, 24.7 patient-days of assisted ventilation per livebirth, respectively). The cost-effectiveness ratio deteriorated initially, increasing from 23.2 to 63.5 additional patient-days of assisted ventilation per additional survivor, but then improved, falling to 43.1 additional patient-days of assisted ventilation per additional survivor in the last era. These changes were even more marked for those of birthweight 750-999 g (20.0, 63.2 to 35.9 additional patient-days of assisted ventilation per additional survivor, respectively). In contrast, the cost-effectiveness ratio was initially worse for those of birthweight 500-749 g, being three-fold higher than for the larger infants, and only improved substantially in the last era (59.8, 58.3 to 44.1 additional patient-days of assisted ventilation per additional survivor, respectively). Conclusions : The initial deterioration in cost-effectiveness ratios between successive eras probably reflected the increased availability of resources for assisted ventilation, without any other major advances in perinatal care. The improvement in cost-effectiveness in the last era reflected, in part, the increased use of antenatal steroid therapy and the introduction of exogenous surfactant to neonatal intensive care.     

Popliteal venous aneurysm

Two new cases of popliteal venous aneurysm, confirmed with findings from venography, are added to seven previously reported cases revealed in the authors' search of the English-language literature. This rare anomaly usually shows as recurrent pulmonary emboli in patients with no underlying predisposition to deep venous thrombosis. Physical examination is usually not helpful in the diagnosis. Results of combined real-time and Doppler ultrasound should indicate the diagnosis, but venography is necessary for confirmation and further anatomic detail. Surgical treatment has been fraught with complications. Eight patients, including these two new cases, have undergone surgery, and none have had a recurrence of pulmonary embolism following surgery.     

Brachial plexus: correlation of MR imaging with CT and pathologic findings

Thirty-two patients with symptoms referable to the brachial plexus were evaluated with magnetic resonance (MR) imaging. Sixteen patients had undergone concurrent computed tomography (CT). MR imaging demonstrated normal findings in 16, 12 neoplasms, three cases of trauma, and one case of possible neural edema. Of the 16 patients with normal findings on MR images, eight had CT scans that were also normal. In one patient, MR images showed that the "mass" seen on CT was actually a tortuous blood vessel. In six of the 12 cases of neoplasm in which CT scans were available, MR imaging revealed more extensive disease. In the other six cases of tumor, MR imaging provided sufficient clinical information to obviate the need for CT or any other imaging modality. MR imaging provided definitive diagnoses in the three cases of trauma without further imaging. In one patient with paresthesia, MR imaging showed high signal intensity of the nerves on T2-weighted images, which was compatible with neural edema. A concurrent CT scan was normal.     

Anatomy of the hip: correlation of coronal and sagittal cadaver cryomicrosections with magnetic resonance images

Summary Magnetic resonance imaging (MRI) is noninvasive and provides images with higher soft tissue contrast than possible with any other imaging modality. Unlike CT which depicts anatomy in the axial plane, MRI is capable of producing images in thin cross sections acquired directly in any plane, usually axial, coronal or sagittal planes. The use of diagnostic MR images is facilitated by an understanding of the detailed anatomy that is depicted. The purpose of this study was to identify anatomical structures in coronal and sagittal cryomicrosections of the hip region. Thin cryosections of the hips of fresh-frozen cadavers were obtained by a method developed by one of the authors (WR). These sections were matched with thin-section, high resolution MR images of a normal volunteer. The complex anatomy of the hip and its surrounding muscles, tendons and ligaments was exquisitely depicted on both the cadaver microcryosections and the matched MRT images.

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Anatomie de la hanche: corrélation entre les microsections et les résultats de l'imagerie en résonance magnétique

Résumé L'imagerie en résonance magnétique (IRM) est une technique non invasive qui permet d'obtenir des images des parties molles avec un contraste plus élevé que toutes les autres techniques. A la différence du scanner qui décrit l'anatomie dans le seul plan axial transverse, l'IRM est capable de donner des images en coupes fines obtenues directement dans n'importe quel plan: couramment dans les plan axial, transverse et sagittal. L'interprétation des images IRM est facilitée par la compréhension de l'anatomie détaillée de la région étudiée. Le propos de ce travail est d'identifier les structures anatomiques dans des plans de coupes sagittales et coronales de la région de l'articulation coxo-fémorale. Des coupes fines de pièces congelées ont été obtenues à partir de douze cadavres selon une méthode mise au point par l'un des auteurs (WR). Ces sections ont été comparées avec des coupes IRM fines faites en haute résolution chez un volontaire sain. L'anatomie complexe de la hanche et des muscles qui l'entourent ainsi que des tendons et des ligaments est décrite avec précision sur les coupes anatomiques et les images IRM.

     

Vena caval filter splaying: potential complication of use of the titanium Greenfield filter

Significant structural and mechanical differences exist between the titanium and stainless steel versions of the Greenfield filter (GF). The titanium GF has a longer leg length (49 mm vs 43 mm), a greater span (38.5 mm vs 28.0 mm), and a larger hook angle (41 degrees vs 23.5 degrees). In vitro tests demonstrated approximately sevenfold greater filter length shortening (a measure of filter splaying) for the titanium GF in response to a given applied load. These differences resulted in marked filter splaying and inferior vena cava (IVC) perforation in three patients in whom a titanium GF had been inserted. The aorta was penetrated by a filter leg in one patient, and abdominal or back pain was present in all three patients. In vitro tests involving thrombosis within a latex balloon revealed that the titanium GF, but not the stainless steel GF, remained splayed even in the face of clot retraction. Design modifications, possibly using shorter, thicker filter legs and using reduced hook angles, should be made in the titanium GF to decrease the risk of filter splaying and IVC perforation before widespread use of this device.     

Recurrent pterygia: results of postoperative treatment with Sr-90 applicators

Recurrent pterygia in 42 patients (48 eyes) were treated locally with strontium-90 irradiation from May 1967 to May 1988. The 31 male patients had an average age of 52 years; the 11 female patients, 46 years. All patients underwent surgical resection of the recurrent pterygia with use of the bare-sclera technique. During the immediate postoperative period the surgical site was treated with an Sr-90 applicator (beta irradiation). Doses ranged from 10 to 70 Gy (average, 50 Gy). Follow-up times ranged from 8 to 136 months (median, 14 months). The local control rate was 89%. Four of the five recurrences were in patients treated with doses of 1,000-1,500 cGy (P less than .0002). None of the patients developed cataracts or any other serious complications.