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?

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.

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.

Femoropopliteal bypass using autogenous vein and modified human umbilical vein. A comparative study

This study is based on 223 consecutive femoro-popliteal and femorotibial bypass grafts performed between January 1978 and June 1985 at the Western General Hospital. Autogenous vein grafts demonstrated better 5 year patency rates (54%) than modified human umbilical vein (32%). The superiority of autogenous vein was even more marked when anastomoses were to below knee vessels: 56% compared with 26% at 5 years. Grafts anastomosed to the superficial femoral artery had similar long term patency to those anastomosed to the common femoral artery. When grafts were required for severe ischaemia, similar 5 year patency rates were achieved with autogenous vein (35%) and modified human umbilical vein (30%). The 5 year limb salvage rate in severe ischaemia was 72% for autogenous vein and 63% for modified human umbilical vein. The findings confirm that modified human umbilical vein is a satisfactory alternative when autogenous vein is not available.

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.

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.

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.

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.

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.

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.

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.

Spinal vascular tumors: dilemmas in diagnosis and management

Three case reports of spinal vascular tumors illustrate the need for well-organized and thorough neuroradiological and neurosurgical planning to achieve an initial cure without delay and to avoid inadequate operative procedures.

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.

Warfarin-induced iliopsoas hemorrhage with subsequent femoral nerve palsy

We present the case of a 28-year-old man on chronic warfarin therapy who sustained a minor muscle tear and developed increasing pain and a flexure contracture of the right hip. Surgical exploration revealed an iliopsoas hematoma and femoral nerve entrapment, resulting in a femoral nerve palsy and partial loss of quadriceps functions. Anticoagulant-induced femoral nerve palsy represents the most common form of warfarin-induced peripheral neuropathy; it is characterized by severe pain in the inguinal region, varying degrees of motor and sensory impairment, and flexure contracture of the involved extremity.

Early aneurysmal degeneration of human umbilical vein bypass grafts

Three cases of early aneurysmal degeneration of modified human umbilical vein (HUV) grafts in the femorodistal segment are described. One such graft is the first reported with multiple true aneurysms. The pathology and management of this complication is discussed.

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.

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)

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.

Multiple simultaneous intracerebral hematomas. Clinical, radiologic, and pathologic findings in two patients

The simultaneous occurrence of two intracerebral hematomas in different arterial territories of the brain is rare. We report the clinical, radiologic, and post-mortem findings in two such cases. The absence of readily identifiable vascular disease in such patients suggests that a subtle degenerative process may be active in the pathogenesis of this condition.

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.

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.