Biomedical subjects
Publications and source records attributed to J Conway.
This useful listing of references on radiology administration covers topics from equipment selection to computerization. In addition to available written references, the authors provide information on PC-based access to data bases.
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To evaluate the course, use of diagnostic modalities, management, and outcome of aortic thrombosis associated with umbilical artery catheterization, we reviewed 20 cases of aortic thrombosis diagnosed by ultrasonography (n = 16) or aortography (n = 4) over 4 years. Fourteen of 20 infants had severe perinatal asphyxia, suggesting that asphyxia predisposes to aortic thrombosis. Ultrasonography provided information about the size, location, and configuration of the thrombus and was useful in following thrombus size with therapy. Radionuclide renography-scintigraphy demonstrated abnormal renal function in all 11 patients scanned. Six patients with minor thrombosis (hypertension as the only sign) improved without specific therapy. Nine infants had moderate thrombosis (multiple signs but normal urine output); all survived with a variety of therapies; two were not given anticoagulant or fibrinolytic agents; three improved with heparin alone; and one had surgery without recurrence of the thrombus. Resolution of moderate thrombosis followed streptokinase therapy in two of three infants. All five babies with anuria from major thrombosis died. Hepatic infarction associated with aortic thrombosis was found in three of three autopsies.
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The role of liquid crystal thermography (LCT) in the investigation of nerve root compression due to lumbosacral lateral spinal stenosis was evaluated using a quantitative analysis technique. In 28 healthy volunteers, normal lower limb dermatomal asymmetry was found to follow a Gaussian distribution, with a normal range of less than 1.0 degree for the lower limbs and less than 1.9 degrees for the feet. The results of LCT from a patient group were compared with those from other investigations, with the following results: clinical assessment (107 patients), 53% agreement; myelography (60 patients), 45% agreement; computerized tomography (35 patients), 46% agreement; electromyography (27 patients), 41% agreement; and surgical findings (19 patients), 53% agreement. Each method of investigation was compared against the surgeon's final overall assessment. Clinical assessment agreed in 76%, myelography in 71%, computerized tomography in 71%, and electromyography in 70%. However, agreement could be demonstrated in only 48% of cases using LCT; therefore, it would appear that LCT is by far the least reliable of these techniques in the diagnosis of nerve root compression.
Blood pressure is an inherently variable phenomenon. In addition to this the level rises in the clinical setting; a response which is extremely variable. Problems therefore arise in the diagnosis and treatment of hypertension. Studies have shown that blood pressure can reliably be measured at home either with a stationary or ambulatory apparatus. The readings which are reproducible are generally lower than those obtained in the clinic. Ambulatory recordings are a more reliable guide to prognosis and to the response to hypotensive agents. Home recordings should therefore be more widely used in diagnosis and treatment of the disorder.
The records of 18 children with hematogenous pelvic osteomyelitis seen over a four-year period were reviewed. The mean age of the patients was 7.8 years and their most common presenting symptoms were gait disturbance (present in 94%) and pain about the hip (61%) with only mild limitation of motion; 11 (61%) of 18 patients were afebrile at presentation. Although leukocytosis was uncommon, the erythrocyte sedimentation rate was almost always elevated (greater than 40 mm/hr in 94% of the patients). While initial plain roentgenograms were usually normal, gallium citrate Ga 67 and technetium Tc 99m oxidronate scintigrams were abnormal in all patients who underwent these studies. Computed tomography proved to be a useful complementary study to radionuclide scintigraphy, yielding positive findings in nine of 11 cases. Patients presented for medical care a median of 2.5 days after the onset of symptoms, whereas a longer period of time (median, 7.5 days) was required to establish the correct diagnosis after presentation for care. The only observed complications occurred in two patients in whom there was significant delay in institution of therapy. Prevention of complications from pelvic osteomyelitis lies in early recognition and appropriate treatment of the disease. In our experience, newer imaging techniques facilitate prompt diagnosis.
The sebum excretion rate (SER) was measured above and below the neurological lesion in seventeen male and four female paraplegic patients and at comparable sites in a similar number of age-matched controls. There was no significant difference between paraplegics and controls for forehead SER. For the thigh SER there was a highly significant difference between paraplegics and controls (t = 6.27:P less than 0.001), the level for paraplegics being twice that for controls. Simultaneous thigh skin temperature measurements showed no significant difference between paraplegics and controls.
Blood pressure variability throughout the day has been found to be inversely related to baroreflex sensitivity, as is the response to injected phenylephrine, mental stress and sleep. It is concluded that variability in blood pressure results in some degree from defective buffering of blood pressure by the baroreceptors.
Ten patients who failed to achieve a satisfactory blood pressure level with dual therapy of a diuretic and a beta-blocker were allocated to captopril, nifedipine and methyldopa in random order as third-line therapy. Four patients failed to respond to any third-line agent; one patient responded to all three agents, two to nifedipine and captopril and one only to captopril. Third-line therapy is frequently ineffective and several agents may have to be tried to achieve an adequate response.
We investigated whether changes in baroreflex sensitivity could explain the drop in blood pressure after exercise in 12 borderline hypertensive subjects. Intra-arterial blood pressure and baroreflex sensitivity (phenylephrine method) were measured before and 10, 20, 40 and 60 min after maximal exercise. Systolic blood pressure was lower at all stages after exercise. Baroreflex sensitivity was reduced at 10 min, recovered at 20 min and rose above control values at 40 and 60 min. Although the baroreflex sensitivity recovers slowly after exercise, at 40 and 60 min it is higher than the control value and could therefore contribute to the sustained reduction in blood pressure after a period of heavy exercise.
A study to assess the possible use of a microwave radiometric system for tomographic thermal mapping during hyperthermia treatment has been examined using a computer model. Results indicate that as few as ten waveguide probes in contact with the body may be sufficient for spatial resolution of the heated region. A single probe microwave radiometer has been constructed and used to obtain scan data in a water phantom as an initial stage in the verification of the computer results.
In order to study blood pressure variability we have measured blood pressure, heart rate, plasma noradrenaline and adrenaline concentration and plasma renin activity during sleep and during the waking process in 20 subjects with borderline hypertension. The responses to a number of standardized tests were also measured. These were reading, mental arithmetic, change in posture, physical exercise and the response to intravenously injected phenylephrine and noradrenaline. The sensitivity of the baroreflex for heart rate control was also determined from the relationship between heart period (R-R interval) and change in systolic pressure after the injection of phenylephrine. Blood pressure was also recorded continuously for 24 hours. From the lowest levels achieved during sleep, blood pressure rose as the subjects regained consciousness but was not restored to its baseline value until mental activity was also restored by reading. Blood pressure rose further with mental arithmetic. These changes were accompanied by a greater proportional rise in plasma adrenaline than in plasma noradrenaline concentrations. Plasma renin activity changed little. The pressor responses to phenylephrine and noradrenaline were inversely related to baroreceptor sensitivity. The fall in blood pressure with sleep and the rise with mental arithmetic was also inversely related to the sensitivity of the reflex. Systolic pressure recorded throughout the day was inversely related to the R-R interval in each subject. The slope of this relationship and range of R-R interval was greatest in the subjects with the most sensitive baroreflexes.
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Blood pressure variability has been studied from 24-h direct arterial pressure recordings in 109 subjects (36 normals and 73 hypertensives). Baroreflex sensitivity was also measured. From the 24-h record a linear relationship was found between systolic pressure and heart period. The slope was related to baroreflex sensitivity (r = 0.66, P less than 0.001). Those with shallow slopes had a high systolic pressure level and greater variability, thus efficient control of heart rate limits blood pressure variability.