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Biomedical subjects

R B King

Publications and source records attributed to R B King.

At least 73 records · Page 4Linked to original sources
PubMed1985

Stability of heterogeneity of myocardial blood flow in normal awake baboons.

Regional myocardial blood flow has been thought to be relatively uniform, in accord with the singular function of myocardial cells. However, considerable spatial heterogeneity has been observed in the hearts of anesthetized animals and in isolated hearts. Studies were undertaken in a total of 13 baboons. Eleven were awake, healthy animals sitting in chairs at rest or feeding, some performed mild leg exercise (wheel turning), and others were subjected to whole body heating; two were anesthetized, methodological controls. Microspheres (15 +/- 3 micron diameter, 0.5 X 10(6)/kg body weight) were injected via a catheter into the apex of the left ventricle while arterial blood was sampled at a constant rate for calculating cardiac output. Microspheres with different labels were injected at six intervals of 20 minutes to several hours. On sacrifice, the hearts were sectioned into 204 locatable pieces (left ventricle, 168; right ventricle, 27; and atria, 9). Average resting myocardial flow was 2.1 +/- 0.2 ml/g per min (mean +/- SD, n = 11). Left and right ventricles and atria comprised 70 +/- 2% (n = 13), 20 +/- 2%, and 10 +/- 2% respectively of the total heart mass while receiving 80 +/- 3%, 16 +/- 2%, and 4 +/- 2% of the total myocardial flow. Thus, mean left ventricular flow was 114 +/- 5% of the average for the whole heart, right ventricular flow was 81 +/- 13%, and atrial flow was 41 +/- 13%. Myocardial flow heterogeneity was marked; in left ventricle, regional flows ranged from one-third to two times the mean, the relative dispersion (= standard deviation/mean) of regional flows, corrected for methodological scatter and temporal variation, was 0.33 +/- 0.06 (n = 67) in the whole heart, 0.26 +/- 0.07 in left ventricle, 0.32 +/- 0.11 in right ventricle, and 0.22 +/- 0.19 in the atria. The pattern of regional flows in each heart tended to remain stable with time. In each piece averaged over time, the relative dispersion due to temporal heterogeneity was 0.11 +/- 0.03 (n = 2040) in the whole heart, 0.09 +/- 0.03 in the left ventricle, 0.15 +/- 0.05 in the right ventricle, and 0.23 +/- 0.06 in the atria. The conclusion is that the degree of spatial heterogeneity of local myocardial flows in conscious primates is similar to that of anesthetized animals and isolated hearts, and is much greater than that due to temporal fluctuations.

Animals↗
PubMed1985

Dynamic computed tomography: intracranial applications.

Rapid sequential computed tomography of the brain after the bolus injection of contrast material provides invaluable information as to the characteristic blood flow of intracranial lesions in a noninvasive manner. Plotted dynamic curves permit accurate diagnosis of particularly difficult cases of infarcts and neoplasms. Dynamic computed tomographic (CT) scanning has become a part of the CT work-up for infarcts, which has allowed their earlier demonstration, detected as areas of hypoperfusion not clearly evident on an initial conventional CT study. Quantitative assessment of vasogenic edema and hypoperfusion are helpful in establishing the diagnosis of infarction and neoplasia. Orbital and parasellar neoplasms can be distinguished accurately from vascular lesions. Dynamic CT studies complemented conventional film screen arteriography in the evaluation of three cases of intracavernous internal carotid artery aneurysm, defining thrombus formation and wall thickness and thus influencing the therapeutic approach. In addition, this modality is useful in differentiating jugular fossa neoplasm from vascular malformation. This review elaborates on the technique involved in dynamic CT scanning and the subsequent results.

Arteriovenous Malformations↗
PubMed1985

Wheelchair push-ups: measuring pressure relief frequency.

Ischial pressure sores (PS) are a long-recognized complication of wheelchair confinement, yet teaching spinal-cord patients to establish lift-off behavior habitually and permanently remains a challenge. A new device was developed to record automatically and continuously the wheelchair lift-off behavior of spinal-cord injured patients. Data from seven patients who used the device for between 768 and 1800 hours each are reported. The device was used to monitor longitudinally the behavioral compliance of each individual with prescribed lift-off intervals using standard teaching procedures. Wide variability between patients and within patients over time was found. Experimental interventions including the use of an electronic timer and written and oral feedback of the previous day's data also varied in their effectiveness. Data from one patient who developed a pressure sore while being monitored suggest that there is no simple relationship between lift-off intervals and PS formation.

Adult↗
PubMed1984

Intracranial pressure monitoring in comatose patients with cerebral hemorrhage.

Intracranial pressure (ICP) was measured continuously in ten consecutive comatose patients with intracerebral hemorrhage. Eight hemorrhages were ganglionic, one was thalamic, and one was lobar. The ICP at the time of insertion of the monitoring device was below 20 mm Hg in four patients, 20 to 30 mm Hg in four, and above 30 mm Hg in two. Of the seven patients whose ICP remained above 20 mm Hg despite aggressive medical therapy, three had the clot removed surgically and all three survived, although one died of sepsis a month later. The remaining four patients with uncontrolled ICP all died of the syndrome of brain death. Of tht three patients whose ICP was persistently below 20 mm Hg, one survived and two subsequently died of sepsis after improving neurologically for the first week. Intracranial pressure monitoring did not cause any morbidity. Raised ICP is related to mortality in comatose patients with cerebral hemorrhage, and ICP monitoring may be useful in guiding therapy, especially the timing and selection of patients for surgery.

Adult↗
PubMed1984

Normal and abnormal function of the hypothalamic-pituitary-adrenocortical system in man.

The first half of this manuscript is devoted to a review of the methods used and the results obtained in the published measurements of the normal responses to tests of the three main types of hypothalamic-pituitary-adrenocortical (HPA) activity in man. These are, I, basal, unstressed activity leading to appropriate levels of total daily production of cortisol in the characteristic circadian pattern; II, responses to feedback stimulation of HPA activity by metyrapone administration; and III, responses to tests of the effects of stress on the HPA system including the effects of hypoglycemia, induced fever, vasopressin administration, and ACTH injections and infusions. The advantages and shortcomings of each type of procedure are discussed. The second half of this paper describes the authors' attempts to establish the limits of normality of standard and modified methods of evaluating the HPA system. The defined limits of normality have been used to assess the HPA function in 158 patients with known or suspected disorders of the HPA system. In normal controls, halfhourly plasma cortisol determinations established the normality of circadian and postprandial fluctuations and of mean plasma cortisol concentration, 6.2 +/- 0.3 (SEM) micrograms/dl, which were closely approximated by determinations every 6 h. Metyrapone, given in a dose of 500 mg every 2 h for 24 h increased urinary 17-OHCS excretion to 10.5-32.6 mg/day or to 1.7-7.8 times basal excretion rate. Increasing rates of insulin infusion disclosed significant relationships between resulting plasma glucose and cortisol concentrations. The slopes of the delta cortisol/delta glucose responses were similar after insulin infusions (0.46 +/- 0.05) and after insulin injections, 0.15 U/kg (0.43 +/- 0.09), and were always greater than 0.20 micrograms/mg. This index provides a useful objective measure of the normality of responses to hypoglycemic stress, 0.20-0.87 micrograms/mg. Adrenocortical responses to iv infusions of ACTH (cosyntropin 0.25 mg) may be equivocal at 2 h but are clear cut at 4, 6 and 8 h. Of 158 patients in whom hypopituitarism was known or suspected because of the presence of a pituitary tumor, acromegaly, hyperprolactinemia, or clinical features, HPA function was found to be entirely normal in 88 patients and partially or severely abnormal in the remaining 70 patients.(ABSTRACT TRUNCATED AT 400 WORDS)

17-Hydroxycorticosteroids↗
PubMed1983

Influence of heat stress on exercise-induced changes in regional blood flow in sheep.

Radioactive microspheres were used to measure cardiac output and blood flow to most major tissues in sheep at rest and during treadmill exercise (3- to 6-fold increase in metabolic rate for 30 min) in thermoneutral (TN) [dry bulb temperature (Tdb) = 16 degrees C, wet bulb temperature (Twb) = 12 degrees C] and mildly hot (MH) (Tdb = 40 degrees C, Twb = 23 degrees C) environments. During exercise, rectal temperature increased more under MH than under TN conditions; exercise-induced changes in the major central cardiovascular parameters were unaffected by MH. Exercise in TN caused mild hypocapnia, and in MH, severe respiratory alkalosis. Skin blood flow in the torso decreased during exercise in TN and MH. Extremity skin blood flow was increased by heat but not exercise. Exercise-induced increases in flows to respiratory muscles and upper respiratory tract tissues were greatly enhanced in MH. Exercise caused large increases in blood flow to fore- and hindlimb muscles, which were less in MH than in TN. Effects of MH on exercise-induced changes in flow to these and other tissues (e.g., abdominal viscera and adipose tissue) are discussed in terms of the conflicting requirements of energy expenditure and body temperature regulation during exercise in sheep and other species, particularly humans.

Adipose Tissue↗
PubMed1982

The role of adrenergic mechanisms in thermoregulatory control of blood flow through capillaries and arteriovenous anastomoses in the sheep hind limb.

The possible role of adrenergic mechanisms in thermoregulatory changes in the partition of femoral blood flow between nutrient (capillary) and non-nutrient (arteriovenous anastomoses, AVA) circuits in the hind limb of conscious sheep has been investigated employing radioactive microsphere and electromagnetic blood flow measurement techniques. Constriction of AVAs, normally induced by spinal cooling, could be inhibited by phentolamine, whereas dilatation of AVAs, normally induced by spinal heating, could be inhibited by noradrenaline or methoxamine. AVA constriction could be induced by noradrenaline or methoxamine, or dilatation by phentolamine. Isoprenaline had a small dilator and propranolol a small constrictor effect on AVAs. It is concluded that adrenergic pathways involving predominantly alpha-receptors play a role in thermoregulatory changes in skin blood flow (through AVAs) elicited by manipulation of CNS temperature; under these conditions, beta-receptors do not play any role, although manipulation of their activity will influence AVAs under non-thermoregulatory conditions. Capillary blood flows in skin, bone and fat were sensitive, at different ambient temperatures and to varying degrees, to some alpha- and beta-adrenergic agents.

Animals↗
PubMed1982

Aorto-iliac reconstructions for intermittent claudication.

Over a 12-year period, 290 aortofemoral reconstructions were performed for intermittent claudication involving 449 legs in 262 patients. The accumulative patency rate in surviving patients was 79 per cent at 5 years. The patency rate was significantly better in patients who stopped smoking after operation, and in men compared with women. Dacron grafts were significantly more successful than endarterectomy in men. If there was no associated superficial femoral artery occlusion, endarterectomy and Dacron bypass grafts were equally successful, but Dacron bypass grafts were significantly superior to endarterectomy if the superficial femoral artery was severely stenosed or occluded. The success rates for improving the patients' intermittent claudication were 90 per cent at 3 months and 72 per cent at 3 years. The success rate at 3 years was 80 per cent if the superficial femoral artery was patent but only 62 per cent if the superficial femoral artery was severely stenosed or occluded. Mortality and morbidity rates fell markedly in the last 6 years of the study.

Aorta↗
PubMed1982

Recurrent intracranial hypertension and a midbrain glioma.

At the age of 36, this patient's clinical picture satisfied the criteria for the diagnosis of benign intracranial hypertension. After an essentially symptom-free interval, she developed new symptoms 17 years later that proved to be the result of a associated with glial-lined cavities in the midbrain and malignant glioma in the splenium. The possibility of a relationship between these disparate events is considered.

Adult↗
PubMed1982

Bulging lumbar intervertebral disk: myelographic differentiation from herniated disk with nerve root compression.

Deformities of the margins of the contrast material-filled lumbar thecal sac are common findings at myelography in patients with low back pain, but not all such deformities are due to herniated disks. Differentiation at Amipaque myelography between a diffusely bulging disk (unlikely to cause nerve root compression) and a herniated disk (which typically causes nerve root compression) is based on the curvature and extent of the extradural deformity of the anterolateral margin of the contrast-filled sac and on the presence of fusiform widening of the most distal part of the affected nerve root. The deformity caused by a bulging disk is rounded, usually symmetrical (although occasionally more prominent on one side), and does not extend above or below the disk space; the nerve root is uniform in caliber and normal in size. The deformity caused by a herniated disk is angular and extends cephalad and/or caudal to the level of the disk space; the affected nerve root is usually widened in its most distal visible part. A consecutive series of 33 patients with clinically suspected lumbar disk herniation and no previous history of back surgery underwent laminectomy. Using the criteria listed above for differentiation of bulging from herniated disk on Amipaque myelography, the myelographic diagnosis was correct in all six operatively confirmed bulging disks and in 26 (96%) of 27 operatively verified disk herniations.

False Negative Reactions↗
PubMed1982

Nonsurgical approach to congenital scalp and skull defects.

The management of congenital scalp and skull defects, as generally advocated, is surgical. The authors report such a case that was treated conservatively. At her 3-year follow-up review, the patient's scalp and skull defects and other associated cutaneous defects were fully reconstituted. Such a nonoperative approach, while rarely reported, emphasizes the natural course that some of these lesions may follow. The literature on aplasia cutis congenita is briefly reviewed.

Bandages↗