Biomedical subjects
Publications and source records attributed to D M Long.
Ether, nitrous oxide, halothane, and cyclopropane diffuse through silicone rubber. General anesthesia can be produced in dogs by passing the vapors of any of these anesthetic agents through a coil of silicone rubber tubing, each end of which is placed in an artery and vein. Potential applications include a new method for general anesthesia and a simple accurate vaporizer for halothane.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
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Perfluoroctylbromide, given tracheally either as neat liquid in alveolography or as 10:1 emulsion in bronchography, was cleared roentgenologically from the lungs within 24 hours. Quantitative analysis was performed on a gas chromatograph. The rats were given either 2 ml/kg of neat liquid or 0.4 ml/kg emulsion. One per cent of the neat liquid and 8% of the emulsion were recovered from the tissues respectively 24 hours later. The lungs had the largest amount followed by the intestine, adipose tissue and lymph nodes. Dogs were sacrificed at various intervals following 4 ml/kg of neat liquid or 2 ml/kg of emulsion. Less than 1% of the dose was found in the tissues at 24 hours. A similar pattern of perfluoroctylbromide distribution was observed as in the rats. The tissue contents of perfluoroctylbromide at three months were below the limit of detection. The perfluoroctylbromide levels in the blood and urine of dogs and human volunteers were either non-detectable or barely detectable over a 48-hour period.
Emulsions of radiopaque perfluorocarbon with small particle size were prepared by sonication and concentrated by centrifugation. The emulsions were well tolerated when given intravenously to rats in a dose up to 20 ml/kg. Whole-body angiograms were obtained for up to 6 hours after injection with visualization of vessels smaller then 1 mm. Hepatosplenograms were obtained after 2 hours and for several days after injections of radiopaque perfluorocarbon. Contrast enhancement was also seen in the myocardium, ovaries, adrenal glands, and intestines with brominated perfluorocarbon emulsions.
Alterations in renal blood flow are considered to play an important role in the pathogenesis of acute renal failure. Most techniques designed to assess organ blood flow and microcirculatory disturbances are relatively invasive and cumbersome. This study describes a noninvasive method for the determination of an organ's fractional vascular volume (FVV)-the fraction of an organ occupied by blood vessel lumen. It utilizes computed tomographic (CT) scanning and a contrast agent, perfluoroctylbromide (PFOB), which remains intravascular and is not excreted by the kidney. Acute renal failure (ARF) was induced in rats by intraperitoneal injection of glycerol (5 g/kg). CT scans of kidneys, liver, and heart were performed prior to and following intravenous administration of PFOB. FVV of kidney and liver were calculated prior to induction of ARF and at selected time periods following ARF (20-50 minutes and 60-120 minutes). FVV of the kidney decreased significantly 20-50 minutes following ARF and had returned to control values at 60-120 minutes. Renal histologic abnormalities were more severe at the later time period. Thus, early alterations in blood flow precede pathologic abnormalities in the kidney following glycerol-induced ARF. Determination of an organ's fractional vascular volume is a simple noninvasive technique which provides useful information on the microcirculation during the course of experimental disease.
Perfluoroctylbromide (PFOB), a radiopaque reticuloendothelial system contrast media for computed tomography, has been shown to accumulate in macrophages. In the current study PFOB was tested in rabbits as an abscess imaging agent. Two abscesses were induced in each of 24 rabbits, one in the liver and the other in the peritoneal cavity. CT of the rabbit abdomen was performed four days later, two days after the administration of 5 gm/Kg of PFOB to 12 of these rabbits. The average enhancement of the wall of liver abscesses was by 140 Hounsfield units (HU) relative to the enhanced liver and peritoneal abscesses by 135 HU relative to the control group. This enhancement was secondary to the intense accumulation of PFOB filled macrophages in the abscess wall. In those rabbits where the liver abscess ruptured, the edges of the peritoneal collections enhanced by 147 HU. Regions of inflammation prior to liquifaction enhanced considerably. These areas could not be detected in the animals not receiving PFOB. Though the liquified center of liver abscesses could be seen in the absence of PFOB, none of the peritoneal abscesses could be detected in the animals not receiving PFOB. In contradistinction, all peritoneal abscesses enhanced considerably following PFOB allowing their prospective localization. In conclusion, PFOB accumulates in abscess walls and areas of inflammation producing marked CT enhancement of liver and peritoneal abscess collections. This enhancement allowed the differentiation of peritoneal abscess collections from adjacent bowel.
Thirty-one patients suffering from intractable pain associated with chronic low back syndrome, cancer, and other disorders have been studied after an average of 6 months of treatment by electrical stimulation of the spinal cord applied using electrodes inserted through a Touhy needle into the epidural space. As judged by three different subjective rating methods, epidrual stimulation successfully relieved otherwise intractable chronic pain in from 23 to 26 of the 31 patients. Reported improvements in the ability to perform various everyday activities, and elimination of drug usage by many patients, corroborated this finding.
Percutaneous lumbar medial branch neurotomy is a technique for facet denervation in which the target is specifically the medial branch of the dorsal ramus. The radiology of the technique is illustrated, and the technical aspects of the procedure are described. The accuracy of previous techniques for facet denervation as compared with medial branch neurotomy is reviewed in a comparative analysis of radiographs illustrating the various techniques. It is suggested that the greater accuracy of medial branch neurotomy will permit a more adequate trial of the rationale and efficacy of facet denervation.
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31 patients suffering from intractable pain associated with chronic low back syndrome, terminal cancer, and other disorders have been studied after an average 6 months' treatment by electrical stimulation of the spinal cord applied via electrodes inserted through a Tuohy needle into the epidural space. As judged by three different subjective rating methods, epidural stimulation successfully relieved otherwise intractable chronic pain in from 23 to 26 of the 31 patients. Reported improvements in the ability to perform various everyday activities, and elimination of drug usage by many patients, corroborate this finding. The side effects of stimulation, both as reported subjectively and as measured objectively by sensory testing, were not clinically significant. Spontaneous electrode displacements, leading to loss of analgesia and requiring minor surgery for repositioning, were encountered frequently, as were lead wire failures necessitating replacement. The partially implanted, externally powered stimulation system presently in use also suffers from problems of reliability and convenience to the patient.
Open-ended ventriculocisternal perfusion techniques for determining cerebrospinal fluid production and absorption rates are severely restricted by the absolute requirement that steady state conditions be present. A new closed recirculatory spinal perfusion technique is described. Because steady state equilibrium is not necessary, numerous determinations at multiple intracranial pressures or under varied experimental conditions are possible within relatively brief perfusion periods. Cerebrospinal fluid (CSF) and nondiffusible albumin tracer are rapidly recirculated through the spinal subarachnoid space in a cephalad direction. The concentration of fluorescein-tagged albumin is continuously monitored as the CSF is circulated through a fluorometric flow cell. Measured continuously, intracranial pressure (ICP) is regulated by changing the volume of the external perfusion circuit with a syringe pump connected in series to the recirculatory spinal perfusion. CSF formation and absorption rates are calculated from measurements of albumin concentration, concentration changes with time, ICP, syringe pump infusion rate, and the external perfusion circuit volume. In dogs, data can be collected after only 45 minutes for mixing; perfusions at four or five intracranial pressures in addition to normal resting pressure can be completed within 2 to 3 hours. The data from 15 perfusions in 14 dogs are presented. The method provides normal resting pressure values of CSF production and absorption consistent with those values in the literature determined by traditional ventriculocisternal perfusion techniques. Determinations at multiple intracranial pressures suggest a proportional relationship between absorption and ICP. No consistent acute change in CSF formation with pressures to 50 mm Hg can be inferred from these data.
A case of pleomorphic xanthoastrocytoma is reported with light and electron microscopic findings. This unusual tumor arose in a 15-year-old male. The tumor consisted predominantly of nests of xanthomatous cells and plump spindle cells surrounded by a prominent reticulin network. There was considerable cellular pleomorphism with abundant bizarre giant cells and multinucleated cells. Occasional mitoses were present. Electron microscopy and immunoperoxidase localization of glial fibrillary acidic protein (GFAP) confirmed the glial nature of the tumor. Recognition of this tumor is important. Despite its "m alignant" appearance, the tumor characteristically has a relatively good prognosis and should not be confused with high-grade gliomas or meningeal sarcomas, which require aggressive therapy.
One hundred consecutive patients with postsurgical "failed back" syndrome (PSFBS) without fusion and 100 patients with PSFBS with fusion were evaluated with direct CT, two-dimensional (2D) multiplanar, and three-dimensional (3D) imaging. In the patients with and without fusion, 3D images were found to best display the following: the surgical procedure and its extent, lateral neural foraminal narrowing, and fractures of the posterior elements. The 3D images enabled optimal demonstration of fusion: solidity, pseudarthrosis, incorporation of transverse processes and facet joints, and transitional syndrome. In the patients without fusion, 3D images provided improved appraisal of surgical results in 31%; it showed additional fracture(s) in 9%, better displayed lateral neural foraminal narrowing in 42%, and showed additional posterior element fractures in 11% as compared to axial and 2D multiplanar reconstructed (MPR) scans. Three-dimensional imaging uncovered incomplete fusion in 17%, transitional syndrome in 13%, and pseudarthrosis in 6%. Thus, the 3D imaging provided additional information over the direct axial and MPR images (2D images) in 56 of 100 patients without fusion and 76 of 100 patients with fusion. At our institution, this imaging modality is now routinely performed in this patient population.