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Biomedical subjects

R B King

Publications and source records attributed to R B King.

At least 19 recordsLinked to original sources
PubMed1992

Persistent pain inhibits contralateral somatosensory cortical activity in humans.

To assess cortical activity during pain perception, regional cerebral blood flow (rCBF) studies were done in humans using single photon emission computed tomography (SPECT) with the radiotracer Tc99m-HMPAO and magnetic resonance imaging localization. Normalized SPECT data were analyzed by region of interest and change distribution. Contralateral somatosensory rCBF was decreased when the digits of the hand were immersed in a hot water bath for 3 min which was rated as moderately painful (persistent pain). No decrease was observed when the hand was immersed in tepid water (control). In contrast, cortical rCBF was increased during vibratory and sensorimotor tasks, in the contralateral somatosensory and sensorimotor areas, respectively. These results indicate that pain perception in man is associated with somatosensory cortical inhibition.

Adult↗
PubMed1992

Clean and sterile intermittent catheterization methods in hospitalized patients with spinal cord injury.

The purpose of this study was to compare the incidence of urinary infection using clean intermittent catheterization with the incidence of infection using sterile intermittent catheterization in patients hospitalized with spinal cord injury who were not receiving prophylactic antibiotics. Forty-six patients were assigned randomly to a clean (n = 23) or sterile (n = 23) study group. Catheterizations were done at least every six hours. Infection was defined as bacteriuria greater than or equal to 100,000 organisms/mL or greater than or equal to 10,000 organisms per mL with fever of 100 degrees F or greater. Results of urinary dipslides were recorded daily. Twenty-eight subjects (60.9%) converted to greater than or equal to 100,000 organisms per mL. Method of catheterization was neither associated significantly with development of greater than or equal to 100,000 organisms per mL. (X2[1,46] = .36, p = .55) nor with symptomatic infections (X2[1,46] = .15, p = .70). Data support the use of clean intermittent catheterization under the conditions used in this study, including the use of a sterile catheter each day and careful monitoring of infection and technique. Before using this method with other diagnostic groups or in different clinical settings, further investigation is needed.

Adolescent↗
PubMed1991

The neurosciences and neurosurgery.

Enhancing the time-honored bonds between the neurosciences and neurosurgery is essential. The basic neurosciences are the foundation upon which fundamental scientific training and clinical research depend. Together these form the resource essential to improving the public health. Both now face severe restraints in the support systems available to them, limited degrees of reciprocity, and uncertain human resources. It is critical that the neurosurgical and neuroscience communities renew and enhance their joint commitment and trust so that both can more effectively work together to secure resources appropriate to maintaining the cutting edge on behalf of the public health.

Cost Allocation↗
PubMed1991

Certification, accreditation, and specialization in the 1990s.

Subspecialization was one of the inevitable consequences of merging medicine with science in the early years of this century. The differentiation of human endeavors increases exponentially with new knowledge, technology, and services. Our current patterns of accreditation, certification, and graduate medical education are being seriously challenged by new patterns of subspecialization. How realistically and creatively we respond to this challenge will be a key element in preserving the management of these functions primarily within the purview of the profession.

Accreditation↗
PubMed1990

Fractal descriptions for spatial statistics.

Measures of spatial statistics have been available for estimating means, calculating or assessing differences, estimating nearest neighbor distances, and such, but have not provided a general approach to describing variances. Because measures of heterogeneity depend upon choosing a particular element size in the domain, estimates of apparent heterogeneity are larger with high-resolution observations than with low-resolution data. Many descriptors might be used to describe the relationships between apparent heterogeneity and the size of the observed spatial elements, but we have found that fractal relationships provide concise and precise descriptions of many types of data over large ranges of element sizes. Perhaps more importantly, the fractal approaches give additional insight, such as measures of spatial correlation, and often suggest ways of approaching the underlying basis of the heterogeneity.

Animals↗
PubMed1990

Molecular and particulate depositions for regional myocardial flows in sheep.

The deposition of microspheres in small tissue regions is not strictly flow dependent. In comparison with the soluble flow marker 2-iododesmethylimipramine (IDMI), deposition of 16.5-microns microspheres was mildly but systematically biased into high flow regions of rabbit hearts (Bassingthwaighte JB, Malone MA, Moffett T-C, King RB, Little SE, Link JM, Krohn KA. Am J Physiol 1987;253 (Heart Circ Physiol 22):H184-H193). To examine the possibility of bias in larger hearts, a similar study was undertaken in sheep. 141Ce- and 103Ru-labeled 16.5-microns microspheres in one syringe and 125I- and 131I-DMI in another syringe were injected simultaneously into the left atrium of five open-chest sheep while obtaining reference blood samples from the femoral artery. In six other sheep, one microsphere type and one IDMI were used. Hearts were removed 1 minute after injection, cut into approximately 254 pieces averaging 217 mg, and regional deposition densities calculated for each tracer from the isotopic counts. Correlations in the five animals between the two differently labeled IDMIs and between the two microspheres were both greater than or equal to 0.98. In all 11 sheep, scatter plots of microsphere deposition densities versus IDMI densities showed that differences between microspheres and IDMI had substantially more scatter (0.84 less than r less than 0.98) but were not random. Microsphere depositions tended to be lower than IDMI depositions in low flow regions and higher in high flow regions, in accord with the expected bias that at a bifurcation a microsphere is most likely to enter the branch with higher flow. There was less bias ascribable to endomyocardial/epicardial maldistribution. Thus, while microsphere depositions appear to err systematically with respect to flow when the regions of interest are small enough that the diameters of their arterioles are only a few times those of the microspheres, microspheres are, in sheep as in rabbits, adequate for estimating regional flows.

Animals↗
PubMed1989

Temporal fluctuations in regional myocardial flows.

Considerable spatial heterogeneity has been observed in regional myocardial blood flow in isolated hearts and in both anesthetized and conscious animals. In order to study how local blood flow varies with time, the data obtained by King et al. (1985) from ten awake, healthy baboons were analyzed to estimate the role of temporal fluctuations. Four to six distributions of regional flows were estimated at intervals of 4 min to 27 h, using 15 mu diameter microspheres and dividing each heart into 204 locatable pieces (average piece mass = 0.17 g). The technique averages over the 40 s of the injection giving no measure of fluctuations over a few seconds. The temporal variation in regional blood flow, expressed as the relative dispersion (SD/mean) of the temporally separated measurements about the mean flow for each piece and corrected for methodological noise, was 12% for the whole heart (10828 observations). For the left ventricle, the temporal variation was 10% (8806 observations), for the right ventricle 14% (1455 observations), and for the atria 22% (567 observations). On a relative basis, temporal fluctuation was greatest in regions having low flows. Since the magnitude of the changes in flow distributions was the same after 4 min as it was in several hours, we conclude that much of the "twinkling" is a high frequency phenomenon occurring over seconds to a few minutes. Further, it is concluded that regional myocardial blood flow in conscious primates is relatively stable with time, temporal fluctuations causing only about one third of the variation between regions.

Animals↗
PubMed1989

Challenges in recertification.

We must now face perhaps one of the great changes that is emerging in our practice of medicine of this century: recertification, based not on testing of cognitive skills, but focused on a quality assurance program for clinical performance and satisfactory outcome criteria. Certification is not the same as recertification; each serves a necessary function. For recertification we need to be able to assess physician performance in practice. Standard testing practices in graduate medical education work well in the setting for which they were developed. However, we now need to devise better ways to measure the continuing accrual of knowledge and the consequences of the application of that knowledge in the practice of modern medicine. How can such a determination be made? Who will administer the programs? How can we as physicians assure the public that we are capable of maintaining high standards of performance throughout a physician's practice career?

Certification↗
PubMed1989

Fractal nature of regional myocardial blood flow heterogeneity.

Spatial variation in regional flows within the heart, skeletal muscle, and in other organs, and temporal variations in local arteriolar velocities and flows is measurable even with low resolution techniques. A problem in the assessment of the importance of such variations has been that the observed variance increases with increasing spatial or temporal resolution in the measurements. This resolution-dependent variance is now shown to be described by the fractal dimension, D. For example, the relative dispersion (RD = SD/mean) of the spatial distribution of flows for a given spatial resolution, is given by: RD(m) = RD(mref).[m/mref]1-Ds where m is the mass of the pieces of tissue in grams, and the reference level of dispersion, RD(mref), is taken arbitrarily to be the RD found using pieces of mass mref, which is chosen to be 1 g. Thus, the variation in regional flow within an organ can be described with two parameters, RD(mref) and the slope of the logarithmic relationship defined by the spatial fractal dimension Ds. In the heart, this relation has been found to hold over a wide range of piece sizes, the fractal Ds being about 1.2 and the correlation coefficient 0.99. A Ds of 1.2 suggests moderately strong correlation between local flows; a Ds = 1.0 indicates uniform flow and a Ds = 1.5 indicates complete randomness.

Animals↗
PubMed1987

Validity of microsphere depositions for regional myocardial flows.

Due to the particulate nature of microspheres, their deposition in small-tissue regions may not be strictly flow dependent. To evaluate the importance of rheological and geometric factors and random error, their deposition densities in small regions of rabbit hearts were examined in comparison with those of a new "molecular microsphere," 2-iododesmethylimipramine (IDMI), whose high lipid solubility allows it to be delivered into tissue in proportion to flow, and whose binding in tissue prevents rapid washout. 141Ce- and 103Ru-labeled 16.5-micron spheres in one syringe and [125I]- and [131I]DMI in another syringe were injected simultaneously into the left atrium of open-chest rabbits, while obtaining reference blood samples from the femoral artery. Hearts were removed 1 min after injection, cut into approximately 100 pieces averaging 54 mg, and the regional deposition densities calculated for each tracer from the isotopic counts. Correlations between the differently labeled microspheres were r greater than 0.95 and for the two IDMIs were greater than 0.98. Scatter plots of sphere densities vs. IDMI densities showed that differences between microspheres and IDMI had substantial scatter, 0.87 less than r less than 0.96 and were not random. Microsphere depositions tended to be lower than IDMI depositions at low flows and higher at high flows. The tendency for spheres to be deposited preferentially in high-flow regions may be explained by a bias at bifurcations toward entering the branch with higher flow and secondarily toward entering those branches that are straighter. We conclude that microspheres are generally adequate for estimating regional flows but suffer systematic error when the regions of interest are supplied via arteries of diameters only a few times those of the microspheres.

Animals↗
PubMed1987

A posttraumatic lumbar spinal synovial cyst. Case report.

A patient with posttraumatic lumbar radicular paresthesias is presented. The preoperative diagnosis of an epidural synovial cyst was considered. At surgery, an epidural synovial microcystic mass was found emanating from a distracted L4-5 facet joint and dissecting into the layers of the ligamentum flavum. A brief review of the condition is presented.

Accidental Falls↗
PubMed1987

Cortical localization and monitoring during cerebral operations.

Cortical sensory potentials have been evoked under general anesthesia by median nerve stimulation and direct cortical stimulation of the motor cortex in 35 consecutive patients with mass lesions in the middle half of the cerebral hemispheres. The evoked potentials produce movement that is useful in localizing the pre- and postcentral gyri. Ultrasound has also been used to aid in the selection of access routes to subcortical lesions while sparing the cerebral cortex bordering the rolandic fissure. In five of these 35 patients, the sensory evoked response was also monitored throughout selected portions of their operative procedures. Representative cases have been presented to illustrate how observations made with these methods have been used to facilitate the patient's intraoperative management in an effort to limit postoperative morbidity.

Adolescent↗
PubMed1986

Effects of exercise and heat stress on regional blood flow in pregnant sheep.

Radioactive microspheres were used to measure cardiac output and blood flow to most major tissues, including those in the pregnant uterus, in late-pregnant ewes at rest and during treadmill exercise (approximately 3-fold increase in metabolic rate for 30 min) in thermoneutral (TN) (dry bulb temperature (Tdb) = 13 degrees C, wet bulb temperature (Twb) = 10 degrees C) and mildly hot (MH) (Tdb = 40 degrees C, Twb = 27 degrees C) environments. Exercise caused major increases in blood flow to respiratory muscles, nonrespiratory limb muscles, and adipose tissue, and flow was decreased to some gastrointestinal tissues, spleen, pancreas, and to placental and nonplacental tissues in the pregnant uterus. Heat exposure had relatively little effect on these exercise-induced changes, except that flow was further increased in the respiratory muscles. Results are compared with those of a similar study on nonpregnant sheep in which changes in muscle, skin, and visceral flows during exercise were attenuated by heat exposure. It is suggested that redistribution of blood flow from the pregnant uterus, which in resting ewes took 22% of cardiac output, is a significant buffer against the potentially deleterious effects of combined exercise and heat stress on blood flow to exercising muscles and thermoregulatory tissues.

Animals↗
PubMed1985

Skin AVA and capillary dilatation and constriction induced by local skin heating.

In conscious sheep, total femoral blood flow and flow through arteriovenous anastomoses (AVAs) and capillaries (CAP) in skin of the hindleg were measured employing electromagnetic and radioactive microsphere techniques. Core temperature (Tc) was manipulated using intravascular heat exchangers and hindleg skin temperature (Tsk) was manipulated by immersion in temperature controlled water. With Tc set 1 degree C above normal, AVA flow was highest at the lowest Tsk tested (34 degrees C); AVAs progressively constricted as Tsk was increased from 34 to 40-41 degrees C, then dilated again as Tsk reached the highest levels tested (42-44 degrees C). Skin CAP flow was not altered by Tsk of 34 to 42 degrees C but was increased at a Tsk of 44 degrees C. Therefore total skin blood flow followed essentially the same pattern as AVA flow; total femoral flow also followed this pattern. When Tc was set 0.5 degrees C below normal, AVA flow was low at all levels of Tsk. It is concluded that Tc plays a dominant role in control of skin blood flow, however, once Tc is at a level requiring increased heat loss, Tsk exerts an extremely potent influence on the nature and magnitude of changes in skin blood flow. The pattern of flow changes appears to reflect principally a negative feedback mechanism aimed at maintaining Tsk at approximately 40 degrees C; this may contrast with mechanisms associated with sweating and/or active vasodilatation in other species.

Animals↗