Biomedical subjects
Publications and source records attributed to M P Casey.
A patient with the acquired immunodeficiency syndrome (AIDS) developed severe cyanosis after bronchoscopy (oxygen saturation 34%) from methaemoglobinaemia. This was thought to be due to enhanced absorption of local anaesthetic from the nasopharynx or trachea as a result of candidiasis. The patient responded dramatically to intravenous methylene blue.
Serial pulmonary imaging has proved to be effective in the evaluation of patients undergoing total joint arthroplasty. A clinical dilemma arises in asymptomatic patients whose postoperative pulmonary images differ from the preoperative images. The authors prospectively evaluated 403 patients with serial imaging to determine the significance of changed postoperative images in asymptomatic patients undergoing total hip or knee arthroplasty. Twenty-two (5.5%) patients had significant changes on postoperative images. Seventeen were asymptomatic; all but one underwent pulmonary angiography. Documented pulmonary emboli were demonstrated in 100% of patients whose postoperative images changed to indicate a high probability of pulmonary embolism, 71% whose images changed to a moderate probability, and 0% whose images changed to indeterminate probability. Overall, pulmonary emboli occurred in 76% of all asymptomatic patients with significantly change postoperative images. Asymptomatic pulmonary embolism is a significant occurrence after total hip or knee repair, and a changed lung scan with appropriate clinical evaluation is an accurate indicator of pulmonary emboli in asymptomatic postarthroplasty patients.
The effect of Harrington rod sagittal plane contouring, or lack of it, on total lumbar, segmental lumbar, and lumbosacral lordosis was studied retrospectively in a series of 36 patients operated on for idiopathic scoliosis. Regardless of contouring, there was a decrease in total lumbar lordosis and lordosis above L4, with an increase in lordosis below L5. Although not statistically significant, patients with contoured rods had less loss of segmental (L1-4) lordosis and less increase in segmental lumbosacral lordosis (L4-S1) than the noncontoured group. Although helpful, additional steps beyond concave rod contouring appear to be necessary to consistently preserve lumbar lordosis.
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While the posterolateral technique is the accepted fusion method for chronic mechanical back pain, the results are variable and the indications are narrow. In an attempt to resolve this problem the role of internal fixation has been explored. Relative stiffness and strength under flexion loading of four lumbosacral fixation systems--(1) translaminar facet joint screws, (2) Luque rectangular box, (3) Luque fixation to the pelvis via the Galveston technique, and (4) two-part pelvic spinal rod system--were evaluated and compared to the normal spine with and without posterior ligaments. The stiffness of the normal intact spine was found to be nonlinear: the bending moment is a function of the square of the flexion rotation. Internal fixation resulted in a twofold increase in stiffness. Facet screws were 20% stiffer and the pelvic-spinal system 2.3 times stiffer (p = 0.001) than the Luque systems but all had similar strength. A retrospective study of 135 consecutive posterolateral lumbosacral spine fusions was conducted to determine what factors improved the fusion rate, clinical results, and time to fusion. Diagnosis and previous surgical treatment, discectomy or fusion, were of no significance. The radiographic and clinical results were highly correlated (p = 0.0001). Electrical stimulation failed to improve the results. Internal fixation with facet joint screws or rods to the pelvis was found to statistically decrease the pseudarthrosis rate and reduce the time required for spine fusion (p = 0.02). The surgical technique consists of translaminar facet screws and segmental fixation to the pelvis using a new implant system.
Based on a review of the literature and experience with over 100 surgically treated thoracolumbar spinal injuries, the following information summarizes present knowledge of the subject. Reduction and internal fixation of the injured spine allows early mobilization of all patients, regardless of neurologic deficit, while protecting the neurologic structures from further injury and enhancing their recovery. The ability of the posterior ligamentous complex and the anterior bony column to withstand physiologic loads must be assessed by the history, physical examination, and radiography; then the injured structures should be protected from load or their function replaced by an appropriate surgical implant. Maximum neurologic recovery can be expected with prompt and complete decompression by reduction of the deformity, restoration of the spinal canal, and rigid internal fixation. The internal fixation system selected must provide compression for posterior injuries and distraction for anterior injuries, resist bending in combined injuries, and always restore normal spine shape. The rod-long, fuse-short technique provides the advantages of a more accurate reduction and a more secure fixation, and the minimum length of the fused region results in a more normal spine. The advantages of prompt and rigid but temporary internal fixation justify the risks both short- and long-term.
Major advances have been made in respiratory intensive care over the past three decades. The poliomyelitis epidemics provided the first major impetus for the development of techniques to maintain respiratory support via mechanical means. Principles of bronchial toilet were also established at that time. Development of blood gas electrodes permitted the application of physiologic principles to the management of acute respiratory failure. Recognition of the role of oxygen toxicity and fluid retention allowed a more rational approach to the management of acute respiratory failure. This management in turn was advanced with the introduction of PEEP. Because of the advances made over the last three decades, technology is no longer the limiting factor in survival from acute respiratory failure. If major advances are to be made in the future, a greater understanding of the basic anatomy, biochemistry, and physiology of the lung is necessary.
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