Biomedical subjects
J F Garcia
Publications and source records attributed to J F Garcia.
Cervical spine movement during airway management: cinefluoroscopic appraisal in human cadavers.
The objective of this study was to determine which airway maneuvers cause the least cervical spine movement. A controlled laboratory investigation was performed in a radiologic suite, using eight human traumatic arrest victims who were studied within 40 minutes of death. All subjects were ventilated by mask and intubated orally, over a lighted oral stylet and flexible laryngoscope, and nasally. Cinefluoroscopic measurement of maximum cervical displacement during each procedure was made with the subjects supine and secured by hard collar, backboard, and tape. The mean maximum cervical spine displacement was found to be 2.93 mm for mask ventilation, 1.51 mm for oral intubation, 1.65 mm for guided oral intubation, and 1.20 mm for nasal intubation. Ventilation by mask caused more cervical spine displacement than the other procedures studied (ANOVA: F = 9.298; P = .00004). It was concluded that mask ventilation moves the cervical spine more than any commonly used method of endotracheal intubation. Physicians should choose the intubation technique with which they have the greatest experience and skill.
Imaging rounds #106. Medial subtalar dislocation.
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Case report 582: Lumbosacral meningocele and aortic aneurysm in Marfan syndrome.
A patient with Marfan syndrome presented with enlargement of lumbosacral spinal canal with a bulky meningocele, and a fusiform aneurysm of the ascending aorta. In Marfan syndrome, the presence of a meningocele is extremely rare, but 60% of the patients develop cardio-vascular complications (a frequent cause of death). MRI is the imaging technique of choice for the diagnosis of meningocele and aortic aneurysm.
[Aneurysmal bone cyst of the ethmoid. Apropos of a case].
Repeated epistaxis in a 12 year old child revealed an aneurysmal bone cyst of ethmoid, an exceptional localization for this lesion. Modern imaging techniques (CT scan, NMR) provided precise data on its extent, primordial for decision as to surgical approach. NMR imaging was more effective than the CT scan for diagnosis, since blood lakes were identified, and for determination of extent, since tumoral elements were distinguished from sinusal retentions.
Erythropoietin-hematocrit feedback circuit in the anemia of end-stage renal disease.
Deficient erythropoietin (EP) production is thought to be a key factor in the pathogenesis of the anemia of end-stage renal disease. We describe the interrelationships between radioimmunoassayed plasma EP levels, reticulocyte counts corrected for anemia (CRC) and hematocrit (HCT) under challenge by hemorrhage, transfusions and hemodialysis in 32 chronically-hemodialyzed patients. Spontaneous hemorrhage resulted in a decrease in HCT (P = 0.001) and increases in both EP (P = 0.006) and CRC levels (P = 0.0065). Transfusions of two units of packed red cells into each of 16 patients suppressed EP (P = 0.0004) and CRC (P less than 0.0001) after about 28 and 42 hours, respectively. Repeat transfusions after one to 27 days resulted in similarly significant suppressions of both EP and CRC, except the CRC remained on higher levels for prolonged periods of times. Within a few hours after each transfusion of 2,3-diphosphoglycerate-poor red cells, both EP (P = 0.009) and CRC (P = 0.007) increased temporarily between one to 18 and three to 38 hours, respectively. Hemodialysis resulted in alkalinization (P = 0.008) of blood but not in changes of EP or CRC counts. The data show that, with the EP-HCT feedback loop persisting, increased endogenous hormone levels elicit erythropoietic responses, and that the regulation of EP levels may involve determinants such as oxy-deoxyhemoglobin interactions.
Immunoreactive erythropoietin studies in hypoxic rats and the role of the salivary glands.
Rat erythropoietin (Ep) cross-reacts in the radioimmunoassay (RIA) for human Ep developed in this laboratory. Immunoreactive Ep was measured in serum and tissues of male rats in response to short-term hypoxia (0.43 atm for 24 h). In the unstimulated rat all tissues examined had low levels of Ep, with the exception of the submaxillary or salivary gland (SG). Exposure to hypoxia for 24 h resulted in significant increases in kidney and serum levels of Ep, with no apparent change in SG content. Sialectomy immediately prior to exposure reduced renal Ep production and serum levels significantly after 4 h of exposure. Nephrectomy (N) confirmed previous results by others: Ep production after exposure to hypoxia was reduced but not abolished. The effect of N plus sialectomy was identical to that of N alone, thus excluding the SG as a source of extrarenal Ep in nephrectomized rats. The long-term effect of SG ablation to the same constant stimulus was a steady decline of the Ep response during the first week after surgery, both in renal production and serum levels. Thereafter, from one to six weeks the serum levels remained constant, being higher than in the unstimulated rat but significantly lower than in intact hypoxic animals. No cross-reactivity in the RIA was found with renin, renin substrate, nerve and epidermal growth factor, or somatomedins. If this Ep-like substance in the SG were the source of extrarenal Ep, it should have been possible to document an increase in serum concentration before an increase could be measured in renal content. It appears, however, that the presence of the SG is necessary for renal tissue to be able to synthesize Ep during hypoxia.
[Value of adrenaline in opaque arthrography of the knee. Comparative study of 100 cases].
A prospective study evaluated efficacy of adrenaline in image improvement of opaque arthrography of knee. Of the 100 cases assessed, adrenaline was combined with contrast medium in 50%. Quality of images was compared by double reading of couples of images taken at end of examination. Marked improvement was observed in 2 of 3 cases and it is proposed to use adrenaline routinely to prolong quality of initial arthrogram.
Radioimmunoassay of erythropoietin in chronic uraemia or anephric patients.
The erythropoietin (Ep) plasma titre of 41 anaemic patients with normal renal function or with renal insufficiency (with or without kidney) was measured by RIA and compared to values observed with the polycythaemic mouse assay. A good correlation was found with both methods (r = 0.88). However, about 20% of samples gave higher values with the bioassay. 21 Ep titres measurable by the bioassay ranged from 40 to 4400 mU (mean 717.1 mU) compared to 14.8 to 3788 mU (mean 484.7 mU) measured by the RIA. Low levels of Ep plasma titre have been observed in patients with renal insufficiency and no difference was found between nephric uraemic patients and the anephric group. These results suggest that the increased blood requirements in anephrics are not due to a smaller production of Ep, but ultimately to the presence of an inhibitor of erythropoiesis. The well-known inverse relationship between haematocrit and Ep level was not found in renal insufficiency. However, some humoral regulation of erythropoiesis seems to persist in these patients since the elevation of red blood cells by transfusions was followed by a decrease of the Ep level.
Chest radiographs obtained with shaped filters: evaluation by observer performance tests.
The effectiveness of a shaped filter in improving nodule and infiltrate detection was measured by observer performance testing. Seven observers read 152 test radiographs of the chest obtained from human volunteers. Half the test radiographs had target images. Observer performance in detecting nodule or infiltrate images was compared with the shaped-filter system and with a conventional chest imaging system. The results were analyzed using receiver operating characteristic (ROC) techniques and indicate that the filter technique was not significantly different from the conventional technique in infiltrate depiction. Observer performance in detecting nodules was slightly worse on images obtained with the shaped-filter system.
Temporal response of immunoreactive erythropoietin to acute hypoxemia in fetal sheep.
Acute hypoxemia was produced in chronically catheterized sheep fetuses to determine the response time necessary to increase plasma immunoreactive erythropoietin (Ep) concentration. Sodium nitrite (0.2 mM) was infused via a fetal vein to induce fetal hypoxemia. The resultant fetal methemoglobinemia was associated with a predictable, incremental decrease in arterial oxygen content. Twelve nitrite infusions were performed in eight fetal sheep preparations (gestational ages 115-146 days). Mean methemoglobin level increased to 33% of total Hb after 1-2 h of NaNO2 infusion. These results were compared to those obtained in nine control studies in eight fetuses in which no change was observed for plasma Ep, arterial oxygen content, PaO2, pHa, or whole blood lactate. In the nitrite infused group, however, a significant and progressive increase in mean plasma Ep level over baseline levels was observed during the 4th and 5th h of hypoxemia (p less than 0.01). This change in Ep was significantly greater compared to the control group. These results, however, were confounded by the concomitant development of a lactic acidemia secondary to the fetal hypoxemia. To examine the theoretic possibility that lactic acidemia may primarily affect fetal Ep levels, an additional group of five fetuses was infused with L-lactic acid for the same time period. Although the decrements in pHa and whole blood lactate levels achieved in these fetuses were in excess of those observed during the nitrite infusions, this possibility was ruled out since no change in fetal plasma Ep levels occurred. We conclude that during the 4th h of acute fetal hypoxemia a predictable, progressive increase in plasma Ep level is observed.(ABSTRACT TRUNCATED AT 250 WORDS)
Erythropoietin kinetics in rats: generation and clearance.
Detailed studies to analyze the early events of erythropoietin (Ep) secretion and clearance were performed in a rat model using a double antibody radioimmunoassay. Ep clearance was determined following intravenous injection of 1 mL of Ep-rich plasma, 1,080 mU/mL, obtained from phlebotomized rats. Analysis revealed a disappearance curve that conformed to a two-compartment model with an alpha half-life t1/2 of 3.6 minutes and a beta t1/2 of 86 minutes. The volume of distribution was similar to the calculated plasma volume. In anephric animals, there was no change in the plasma clearance rate or the volume of distribution. Rapid Ep secretion was elicited by a single 15 mL/kg phlebotomy (hematocrit decrement 45% to 30%), so that levels reached 20 to 30 times baseline (524 +/- 76 v 24 +/- 7 mU/mL) at five hours, whereas they plateaued for at least 33 hours. The increase in the rate of secretion was geometric, from 9.9 mU/h baseline secretion to 429 mU/h. These data identify a very sensitive and rapidly responsive system for Ep modulation in the rat.
Clinical applications of measurement of serum immunoreactive levels of erythropoietin.
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Open, prospective study of the clinical efficacy of ciprofloxacin.
One hundred patients with infections mostly outside of the urinary tract were studied in a prospective, open manner to ascertain the effectiveness and safety of ciprofloxacin in a variety of clinical situations. There were 41 instances of bacteremia, including 38 with Salmonella typhi, and 21 respiratory, 17 skin and skin structure, 11 bone or joint, 6 gastrointestinal, and 4 urinary tract infections. The patients were given 500 mg of ciprofloxacin orally every 12 h for 2 to 107 days (mean, 15.1 days). Microorganisms isolated disclosed susceptibilities comparable to those reported previously, with a MIC for 90% of the strains of 0.25 microgram/ml. For Streptococcus pneumoniae the MIC for 90% of the strains was 0.03 microgram/ml, and it was higher for Pseudomonas aeruginosa (0.5 microgram/ml), although still in the therapeutic range. Levels in blood were lower than those reported in other series, and no accumulation of the drug during treatment was detected. In 88 instances there was resolution of the infectious process, in 7 there was improvement, in 3 there was a failure to respond, and in 2 the clinical response was indeterminate. Bacteriological eradication was documented in 87 infections. Despite extensive clinical and laboratory examinations before, during, and after therapy, no major abnormalities related to therapy were seen; only one patient required discontinuation of ciprofloxacin due to gastrointestinal intolerance. Ciprofloxacin is an effective and safe therapeutic alternative in many tissue infections caused by susceptible microorganisms.
ROC and contrast detail image evaluation tests compared.
Using both contrast detail and receiver operating characteristic (ROC) evaluation tests, we evaluated different quality images, produced with different film-screen combinations. ROC curves were obtained for six observers who were attempting to detect lung nodules and pulmonary infiltrates. The contrast detail curves were obtained from images of regular circular test patterns of differing contrast, which had been presented to the observers. Our results indicate that contrast detail tests can be used for relative ranking of image systems prior to detailed ROC testing.
Serum immunoreactive erythropoietin levels in patients with polycystic kidney disease as compared with other hemodialysis patients.
Serum erythropoietin levels were randomly collected and measured by a sensitive radioimmunoassay in a hemodialysis population. For analysis, the patients were divided into two groups: those with polycystic kidney disease and those with other kidney diseases. In 12 polycystic kidney disease patients, serum erythropoietin was 22.6 +/- 2.4 mU/ml, hematocrit 29.7 +/- 1.0%, and absolute reticulocyte count 17.0 +/- 4.1 X 10(4)/microliters. In 24 other kidney disease patients, serum erythropoietin was 12.4 +/- 0.7 mU/ml, hematocrit 21.2 +/- 0.8%, and reticulocyte count 7.5 +/- 1.5 X 10(4)/microliters. Serum erythropoietin was 18.5 +/- 0.7 mU/ml in normal controls. Polycystic kidney disease patients manifested higher hematocrit, reticulocyte counts, and serum erythropoietin levels when compared to other kidney disease patients (p less than 0.01). The data suggest (1) an inappropriately low serum erythropoietin level for the severity of anemia in uremic hemodialysis patients and (2) that greater availability of erythropoietin results in more effective erythropoiesis, even in the uremic environment.
Erythropoietin kinetics in normal and uremic sheep.
Homologous erythropoietin (Ep)-rich plasma was infused into sheep to determine the kinetics of this hormone in a large animal model. Ep levels after infusion were measured by radioimmunoassay using a sheep standard. Twenty-seven infusions into normal (14), subtotally nephrectomized (11), and anephric (two) animals were analyzed according to a single-compartment model. The volume of distribution was also calculated, and compared with values obtained indirectly from measurement of chromium 51-labeled red blood cells. The data showed that the t1/2 of the infused hormone was approximately 9 hours and was independent of renal function. After multiple infusions, the t1/2 appeared to shorten. The volume of distribution for this hormone corresponded to the plasma volume of the animals. These studies suggest that Ep, if administered to patients with chronic renal failure, could be given infrequently with little dependence on renal function.
Rapid regional osteolysis from pancreatic carcinoma.
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