Robust, defensible, and fair: The AMEE guide to selection into medical school: AMEE Guide No. 153.

Selection is the first assessment of medical education and training. Medical schools must select from a pool of academically successful applicants and ensure that the way in which they choose future clinicians is robust, defensible, fair to all who apply and cost-effective. However, there is no comprehensive and evidence-informed guide to help those tasked with setting up or rejuvenating their local selection process. To address this gap, our guide draws on the latest research, international case studies and consideration of common dilemmas to provide practical guidance for designing, implementing and evaluating an effective medical school selection system. We draw on a model from the field of instructional design to frame the many different activities involved in doing so: the ADDIE model. ADDIE provides a systematic framework of Analysis (of the outcomes to be achieved by the selection process, and the barriers and facilitators to achieving these), Design (what tools and content are needed so the goals of selection are achieved), Development (what materials and resources are needed and available), Implementation (plan [including piloting], do study and adjust) and Evaluation (quality assurance is embedded throughout but the last step involves extensive evaluation of the entire process and its outcomes).HIGHLIGHTSRobust, defensible and fair selection into medical school is essential. This guide systematically covers the processes required to achieve this, from needs analysis through design, development and implementation, to evaluation of the success of a selection process.

Advancing quality culture in health professions education: experiences and perspectives of educational leaders.

The concept of quality culture has gained increased attention in health professions education, drawing on insights that quality management processes and positive work-related attitudes of staff in synergy lead to continuous improvement. However, the directions that guide institutions from quality culture theory to educational practice have been missing so far. A prospective qualitative case study of three health professions education programmes was conducted to explore how a quality culture can be enhanced according to the experiences and perspectives of educational leaders. The data collection was structured by an appreciative inquiry approach, supported with vignette-based interviews. A total of 25 participants (a selection of course coordinators, bachelor coordinators and directors of education) reflected on quality culture themes to learn about the best of what is (Discover), envision positive future developments (Dream), identify actions to reach the desired future (Design), and determine how to support and sustain improvement actions (Destiny) within their own educational setting. The results are presented as themes subsumed under these four phases. The experiences and perspectives of educational leaders reveal that peer learning in teams and communities, attention to professional development, and embedding support- and innovation networks, are at the heart of quality culture enhancement. An emphasis on human resources, (inter)relations and contextual awareness of leaders stood out as quality culture catalysts. Educational leaders are therefore encouraged to especially fuel their networking, communication, coalition building, and reflection competencies.

Endothelial glycocalyx thickness and platelet-vessel wall interactions during atherogenesis.

The endothelial glycocalyx (EG), the luminal cover of endothelial cells, is considered to be atheroprotective. During atherogenesis, platelets adhere to the vessel wall, possibly triggered by simultaneous EG modulation. It was the objective of this study to investigate both EG thickness and platelet-vessel wall interactions during atherogenesis in the same experimental model. Intravital fluorescence microscopy was used to study platelet-vessel wall interactions in vivo in common carotid arteries and bifurcations of C57bl6/J (B6) and apolipoprotein E knock-out (ApoE-/-) mice (age 7 - 31 weeks). At the same locations, EG thickness was determined ex vivo using two-photon laser scanning microscopy. In ApoE-/- bifurcations the overall median level of adhesion was 48 platelets/mm2 (interquartile range: 16 - 80), which was significantly higher than in B6 bifurcations (0 (0 - 16), p = 0.001). This difference appeared to result from a significant age-dependent increase in ApoE-/- mice, while no such change was observed in B6 mice. At the same time, the EG in ApoE-/- bifurcations was significantly thinner than in B6 bifurcations (2.2 vs. 2.5 µm, respectively; p < 0.05). This resulted from the fact that in B6 bifurcations EG thickness increased with age (from 2.4 µm in young mice to 3.0 µm in aged ones), while in bifurcations of ApoE-/- mice this growth appeared to be absent (2.2 µm at all ages). During atherogenesis, platelet adhesion to the wall of the carotid artery bifurcation increases significantly. At the same location, EG growth with age is hampered. Therefore, glycocalyx-reinforcing strategies could possibly ameliorate atherosclerosis.

Leucocyte and platelet adhesion in different layers of the small bowel during experimental total warm ischaemia and reperfusion.

BACKGROUND: Ischaemia and reperfusion (IR) of the small bowel is involved in many clinical conditions. A key component in IR-induced tissue damage is microvascular dysfunction. The aim was to investigate the role of leucocytes and platelets in capillary flow impediment and tissue damage. METHODS: Anaesthetized rats were subjected to 30 min warm ischaemia of the small bowel, followed by 1 h reperfusion. To elucidate the influence of leucocytes on platelet adhesion, leucocyte-vessel wall interactions induced by IR were prevented by anti-platelet activating factor (PAF) or anti-intercellular adhesion molecule (ICAM)-1. Intravital videomicroscopy was performed and tissue injury was evaluated histologically. RESULTS: In submucosal venules, IR induced an increase in the median number of interacting leucocytes from 3 to 10 and 20 leucocytes per 100-microm venule segment after 10 and 60 min reperfusion respectively. Anti-PAF or anti-ICAM-1 completely attenuated this increase, resulting in an eightfold improvement in submucosal capillary flow and reduced tissue injury. Shedding of villi no longer occurred. Platelet-vessel wall interactions occurred particularly in submucosal venules, but were not affected by anti-PAF or anti-ICAM-1. CONCLUSION: Small bowel IR initiated an inflammatory and thrombotic response in the submucosal layer only. Attenuation of leucocyte adhesion improved submucosal capillary perfusion, preventing shedding of mucosal villi.

Two-photon microscopy of vital murine elastic and muscular arteries. Combined structural and functional imaging with subcellular resolution.

Understanding vascular pathologies requires insight in the structure and function, and, hence, an imaging technique combining subcellular resolution, large penetration depth, and optical sectioning. We evaluated the applicability of two-photon laser-scanning microscopy (TPLSM) in large elastic and small muscular arteries under physiological conditions. Elastic (carotid) and muscular (uterine, mesenteric) arteries of C57BL/6 mice were mounted in a perfusion chamber. TPLSM was used to assess the viability of arteries and to visualize the structural components elastin, collagen, nuclei, and endothelial glycocalyx (EG). Functionality was determined using diameter changes in response to noradrenaline and acetylcholine. Viability and functionality were maintained up to 4 h, enabling the assessment of structure-function relationships. Structural vessel wall components differed between elastic and muscular arteries: size (1.3 vs. 2.1 microm) and density (0.045 vs. 0.57 microm(-2)) of internal elastic lamina fenestrae, smooth muscle cell density (3.50 vs. 1.53 microm(-3)), number of elastic laminae (3 vs. 2), and adventitial collagen structure (tortuous vs. straight). EG in elastic arteries was 4.5 microm thick, covering 66% of the endothelial surface. TPLSM enables visualization and quantification of subcellular structures in vital and functional elastic and muscular murine arteries, allowing unraveling of structure-function relationships in healthy and diseased arteries.

Capillaries and flow redistribution play an important role in muscle blood flow reserve capacity.

Perfusion of skeletal muscle varies considerably during rest, exercise, or when arteries are occluded. The extent that a muscle can adapt to changes in flow demand is often expressed as the ratio of the highest inducible flow and control flow, the microvascular blood flow reserve capacity (MBFRC). However, perfusion of the nutritive capillaries of skeletal muscle may not only be improved by the increase in blood flow proportional to the increase in arterial flow, but also by diverting originally shunted flow towards the muscle proper. Consequently, MBFRC is not a good measure of capillary flow reserve, unless the assessed flow in both conditions is purely nutritive in nature. Therefore, in critical conditions, flow measurements in large vessels are not appropriate to assess MBFRC. In muscle, capillaries are compliant, i.e., with varying transmural pressure capillary diameter varies. During high perfusion states, when capillary transmural pressure is increased, capillary compliance results in increased capillary diameter and, hence, in reduced resistance and increased exchange surface area. This results in improved perfusion and enlarged capillary exchange surface area. In low perfusion states, capillary diameter is reduced. This augments the detrimental effects of the low perfusion status. Operative restoration of perfusion pressure not only increases the driving force for perfusion, but also leads to (passive) dilatation of the capillary bed and an extra reduction in resistance to flow, and, hence, a disproportional increase in flow.

Effects of experimental lower-limb ischaemia-reperfusion injury on the mesenteric microcirculation.

BACKGROUND: Ischaemia-reperfusion (I-R) of the leg is associated with functional and structural changes in the intestine. This study assessed whether acute hind-limb I-R in rats induced a reduction in perfusion and/or signs of an inflammatory response in the intestine. METHODS: Rats were subjected to 2 h of unilateral hind-limb ischaemia followed by 2 h of reperfusion (I-R group, n = 9) or to a sham procedure (control group, n = 9). Mesenteric microvascular diameters, red blood cell velocity, blood flow and leucocyte-vessel wall interactions during reperfusion were measured using intravital microscopy. RESULTS: Blood pressure and heart rate decreased from 30 min of reperfusion onwards in the I-R group compared with controls. From 15 min after the start of reperfusion, mesenteric arteriolar and venular red blood cell velocity and blood flow decreased by 40-50 per cent. Microvascular diameters and leucocyte-vessel wall interactions did not change. CONCLUSION: Restoration of blood flow to an acutely ischaemic hind limb led to a significant decline in the splanchnic microcirculatory blood flow. There were, however, no signs of an early inflammatory response in the gut.

Microcirculatory effects of experimental acute limb ischaemia-reperfusion.

BACKGROUND: The object of this study was to develop an animal model in which changes in microvascular haemodynamics and leucocyte-vessel wall interactions due to acute limb ischaemia-reperfusion (I/R) can be measured in the skin. Furthermore, it was investigated whether these changes are related to local muscle injury. METHODS: Male Lewis rats were subjected to unilateral limb ischaemia for 1 h (n = 8) or 2 h (n = 8) by cuff inflation, or to a sham protocol (n = 6). Intravital video microscopic measurements of leucocyte-vessel wall interactions, venular diameter, red blood cell velocity and reduced velocity (which is proportional to wall shear rate) were performed in skin venules before ischaemia and at 0.5, 1, 2, 3 and 4 h after the start of reperfusion. Oedema and leucocyte infiltration of ischaemic/reperfused skeletal muscle were quantified histologically. RESULTS: In skin venules, both 1 and 2 h of ischaemia induced a significant increase in leucocyte rolling (six and five times baseline, respectively; P < 0.05) and adherence during reperfusion (eight and four times baseline; P < 0.05). No significant increase in muscular leucocyte infiltration was detected. After an initial hyperaemic response of 180 per cent of baseline values (P < 0.05), blood flow decreased to about 60 per cent after 4 h of reperfusion in skin venules of both experimental groups. I/R induced tibial muscle oedema, the severity of which depended on the ischaemic interval (wet to dry ratio: control, 4.0; 1 h, 4.5 (P not significant); 2 h, 5.8 (P < 0.05)). CONCLUSION: A non-invasive animal model was developed that enables investigation of the consequences of acute limb I/R.

Tumor angiogenesis factors reduce leukocyte adhesion in vivo.

Leukocyte-endothelium interactions are diminished in tumors. It is reported here that, in a tumor-free in vivo model, angiogenic factors can down-regulate leukocyte adhesion to endothelium. Slow releasing pellets were loaded with either basic fibroblast growth factor (bFGF), vascular endothelial cell growth factor (VEGF) or vehicle alone and were placed in the scrotum of mice. After 3 days, a single intrascrotal injection of 1 microg/kg IL-1beta was given 4 h before vessels of the cremaster muscle were investigated for leukocyte rolling and adhesion by means of intravital microscopy. Exposure of normal tissue to either bFGF or VEGF resulted in markedly decreased levels of cytokine-induced leukocyte adhesion. Suppression of leukocyte rolling was not observed. Instead a moderate enhancement of rolling by VEGF was found. The observed differences could not be explained by differences in fluid dynamic parameters or systemic leukocyte counts. In conclusion, evidence is presented that, in vivo, angiogenic factors significantly reduce leukocyte adhesion, the final step preceding leukocyte infiltration. This observation may explain why tumors escape from immune surveillance.

The influence of prostaglandins on leukocyte-endothelium interactions in rabbit mesenteric venules.

Contradictory results have been reported concerning the effects of prostaglandins (PGs) on leukocyte-endothelium interactions. Therefore, we investigated the in vivo effects of PGE1, PGE2, Iloprost (a stable PGI2-analogue), and also of a combination of these PGs on leukocyte rolling and FMLP-induced leukocyte adhesion in venules of rabbit mesentery. This preparation was used because of its low level of vasoactivity, eliminating hemodynamic effects on leukocyte-endothelium interactions. The mesentery was superfused with PGs or vehicle. After 30 min FMLP was added to the PG-solution for 15 min, whereupon the tissue was superfused with the PG-solution alone for another 30 min. Neither the PGs nor the cocktail influenced leukocyte rolling. During FMLP administration leukocyte adhesion increased and leukocyte rolling decreased; adhesion was highest in the presence of PGE2. The FMLP-induced decrease in leukocyte rolling was similar in all groups. After FMLP administration had been stopped the number of adherent cells almost returned to baseline and the level of leukocyte rolling increased, the baseline level being reached only in the presence of PGE2. In conclusion, these findings indicate that the effects of PGs on leukocyte-endothelium interactions are limited.

Total warm ischemia and reperfusion impairs flow in all rat gut layers but increases leukocyte-vessel wall interactions in the submucosa only.

OBJECTIVE: To study the effect of warm ischemia and reperfusion (I/R) on local perfusion and leukocyte-vessel wall interactions in vivo in all small bowel layers, and to quantify small bowel tissue injury histologically and by measuring intestinal fatty acid binding protein (I-FABP) release from the enterocytes. SUMMARY BACKGROUND DATA: Gut injury as a result of I/R plays a pivotal role in a variety of clinical conditions, such as small bowel transplantation, heart or aortic surgery, and (septic) shock. The precise mechanism behind I/R injury and the role of microvascular changes remain unclear. The influence of warm I/R of the gut on microvascular parameters in the different gut layers has not been studied before. METHODS: Anesthetized Lewis rats were either subjected to 30 minutes of ischemia and 1 hour of reperfusion or sham-treated as controls. After ligating the inferior mesenteric artery, total warm ischemia was induced by clamping the superior mesenteric artery. Intravital video microscopic measurements were obtained at intervals. Tissue injury of the small bowel and other organs was histologically evaluated afterward. In addition, plasma levels of I-FABP were determined to measure enterocyte damage. RESULTS: After ischemia, mean red blood cell velocity decreased significantly in all layers of the small bowel, but no diameter changes were observed. Leukocyte-vessel wall interactions increased in the submucosa but not in the muscle layers. Plasma levels of I-FABP significantly increased from 30 minutes of reperfusion onward. The intestinal mucosa was severely injured; no histologic damage was detected in other tissues. CONCLUSIONS: This is the first in vivo study showing that total warm ischemia of the rat gut impairs perfusion in the whole small bowel, whereas leukocyte-vessel wall interactions increase in the submucosal layer only. Therefore, the early inflammatory response to I/R seems to be limited to the submucosa. Both microvascular effects may have contributed to the severe morphologic and functional mucosal injury observed after I/R.

Effect of repetitive asphyxia on leukocyte-vessel wall interactions in the developing chick intestine.

BACKGROUND/PURPOSE: Information on leukocyte-vessel wall interactions (LVWI) during development of the immature intestine is scarce. The authors designed an experimental model for studying the microcirculation in the developing intestine of chick fetuses at days 13 (n = 12), 15 (n = 17), and 17 (n = 19) of incubation (0.6, 0.7, and 0.8 of the incubation time, respectively) using intravital microscopy. METHODS: The authors investigated whether episodes of asphyxia increase LVWI and induce tissue damage in the developing intestine. Asphyxia was induced by clamping of the chorioallantoic vein for 6 periods of 5 minutes each, with 5-minute intervals, whereas in sham groups a sham procedure was performed. Video recordings were made before as well as 10, 20, and 30 minutes after the end of the asphyxia or sham protocol. RESULTS: Baseline number of rolling leukocytes per minute significantly increased (P < .001) from 0 at 0.6 incubation to 1.5 and to 4 at 0.7 and 0.8 incubation time, respectively. At 0.6 and 0.7 incubation no adherent leukocytes were observed under baseline conditions, whereas at 0.8 incubation single leukocytes adhered to the venular wall. LVWI variably increased during the course of the experiments. Asphyxia neither enhanced LVWI nor induced histological damage in the intestine. CONCLUSIONS: These findings indicate that (1) leukocyte-vessel wall interactions mature during fetal development, and (2) repetitive episodes of asphyxia induce neither an inflammatory response nor histological tissue injury in the developing intestine from 0.6 to 0.8 incubation. The authors hypothesize that immaturity of leukocyte-vessel wall interactions, as part of the nonspecific host defense to invading bacteria, might play a role in the development of necrotizing enterocolitis in premature neonates.

Effects of surgical sympathectomy on skin blood flow in a rat model of chronic limb ischemia.

The role of lumbar sympathectomy in the treatment of limb ischemia secondary to arteriosclerosis obliterans has been controversial. Increased temperature and rubor of the skin, which usually follow sympathectomy, have generally been interpreted as indicative of improved nutritive skin blood flow. However, the existence of a (nonnutritive) thermoregulatory level of skin microcirculation makes such an extrapolation questionable. We investigated the total (mainly thermoregulatory) skin blood flow (TSBF) in the hindlimb of 15 male Lewis rats by means of laser Doppler flowmetry and the nutritive skin blood flow (NSBF) by means of capillary microscopy (red blood cell velocity). Transcutaneous oximetry was used to assess skin oxygenation (SO). Measurements were performed before and 2 and 28 days after ligation of the common iliac and iliolumbar artery. Subsequently, either a surgical resection of the sympathetic chain (L2-L6) was performed or a sham operation. Measurements were repeated 2 and 28 days later. For the group of 15 rats as a whole, TSBF (p < 0.05), NSBF (p < 0.05), and SO (p < 0.05) were found to be drastically reduced at day 2 after litigation compared to preligation values. This reduction partially recovered during the following weeks. TSBF (p < 0.05) and NSBF (p < 0.05), however were still reduced at day 28 after ligation compared to preligation values, whereas the SO at this time tended to be lower (p = 0.11). In the sympathectomy group the TSBF was found to be increased at day 2 (p < 0.05) and day 28 (p < 0.05) after sympathectomy, both compared to values obtained at day 28 after ligation. Sympathectomy did not have an effect on NSFB and SO. The sham procedure had no effect on the TSBF, NSBF, or SO. These results indicate that in case of lower limb ischemia, sympathectomy improves skin blood flow at the thermoregulatory but not the nutritive level of skin microcirculation. This may be related to the fact that the thermoregulatory vessels are mainly sympathetically controlled, whereas the nutritive capillaries are mainly controlled by local (nonneural) factors.

The role of mast cells and histamine in leukocyte-endothelium interactions in four rat strains.

The objective of the present study was to determine the role of mast cells and histamine in leukocyte-endothelium interactions in mesenteric venules of four rat strains: Brown Norway, Lewis, Sprague-Dawley and Wistar. Intravital microscopy showed that the mast cell stabilizer cromoglycate (5 mg/kg i.v. just before exteriorization of the mesentery) did not affect the baseline level and velocity of leukocyte rolling in any of the four strains. This finding is in agreement with the observation that cromoglycate pretreatment only slightly influenced mast cell degranulation in all strains except the Brown Norway. After mast cell stabilization, only in Sprague-Dawley did topical administration of histamine (10(-4) M) result in a significant increase in the level of leukocyte rolling and a decrease in the rolling velocity compared with the time control. Histamine induced leukocyte adhesion only in the Brown Norway strain. In conclusion, the hypothesis presented in other studies, that degranulation of mast cells, and more specifically the release of histamine, is of major importance for the induction of leukocyte-endothelium interactions in rat mesenteric venules is not generally applicable; the present study shows a clear strain dependency.

Endogenous nitric oxide protects against thromboembolism in venules but not in arterioles.

Because nitric oxide (NO) inhibits aggregation and adhesion of blood platelets, NO may play a role in platelet-vessel wall interactions. Therefore, the purpose of this study was to investigate the involvement of endogenous NO in thromboembolic processes, as induced by wall puncture, in rabbit mesenteric arterioles and venules (diameters 20 to 43 microm). In venules, inhibition of NO synthase by superfusion of the mesentery with N omega-nitro-L-arginine (L-NA; 0.1 mmol/L) significantly increased the duration of embolization (from 50 seconds to 511 seconds) and the number of emboli produced (from 2 to 11 emboli per vessel), while the median period of time needed to produce an embolus was not influenced. On the contrary, in arterioles, L-NA had no significant effect on embolization (duration of embolization: 426 seconds in the control and 382 seconds in the L-NA group, with 20 and 12 emboli per vessel, respectively). Addition to the L-NA superfusate of L-arginine (L-ARG; 1 mmol/L), the active precursor for endogenous NO synthesis, resulted in a complete reversal of the L-NA effects in venules, while addition of the inactive D-arginine (D-ARG; 1 mmol/L) had no effect. Addition of L-ARG and D-ARG had no significant effect in arterioles. Addition to the L-NA superfusate of the exogenous NO donor sodium nitroprusside (0.1 micromol/L) also resulted in reversal of the L-NA effects in venules, while in arterioles, it slightly but significantly decreased embolization duration. The differences in effect of L-NA on embolization between arterioles and venules were not caused by differences in fluid dynamic conditions. It is concluded that the role of endogenous NO in inhibiting thromboembolic processes is more important in venules than in arterioles.

Different effects of anesthetics on spontaneous leukocyte rolling in rat skin.

In immunological reactions, leukocytes need to travel from the intravascular space through the vessel wall into the surrounding tissue. The first step in this process is leukocyte rolling, which has often been studied in anesthetized animals. In this study, we investigated the effect of pentobarbital, Hypnorm and both components of the latter, fentanyl and fluanisone, on this primary leukocyte-endothelial cell interaction. Using intravital brightfield video microscopy, observations were made in postcapillary venules in the intact skin of the nailfold of trained conscious Lewis rats. Subsequently, the animals were anesthetized and observations were made in vivo. Leukocyte rolling was significantly elevated after injection of Hypnorm or fentanyl, while pentobarbital and fluanisone had no effect. None of the anesthetics affected leukocyte rolling velocity. Blood flow was significantly increased only after injection of Hypnorm and fluanisone. No correlation existed between the relative changes in leukocyte rolling and concomitant changes in blood flow. The results show that the level of leukocyte rolling can be affected by anesthetics. These changes are probably not mediated by changes in local hemodynamics. Pentobarbital anesthesia does not influence leukocyte rolling. Therefore, pentobarbital is a suitable anesthetic for observation of leukocyte rolling in skin. Hypnorm significantly increases the level of rolling in skin venules. This effect seems to be caused mainly by fentanyl.

Effects of different durations of total warm ischemia of the gut on rat mesenteric microcirculation.

BACKGROUND: Gut injury due to ischemia and reperfusion (I/R) plays a pivotal role in many clinical conditions, such as small bowel transplantation, heart or aortic surgery in adults, and necrotizing enterocolitis in neonates. The influence of ischemic events on microcirculatory mechanisms is not well understood. Therefore, we studied, in vivo, local perfusion and leukocyte-vessel wall interactions before and after different periods of total warm ischemia of the whole gut and subsequent reperfusion in mesenteric microvessels. MATERIALS AND METHODS: Groups of pentobarbital-anaesthetized Lewis rats were subjected to 15 (n = 9), 30 (n = 12), or 60 min (n = 5) of total warm gut ischemia and 2 h reperfusion. As control a sham group (n = 10) was included. After ligating the inferior mesenteric artery, total warm ischemia was induced by clamping the superior mesenteric artery. Before and at different time periods after start of reperfusion intravital video microscopic measurements were performed. RESULTS: Rats subjected to 60 min ischemia died during the early reperfusion phase. Fifteen, 30, and 60 min ischemia induced in venules a significant decrease in blood flow, while diameter changes were not observed. This flow decrease was severe in the 15- and 30-min ischemia groups, dropping to 40 and 25% of control, respectively. Following 60 min ischemia blood flow did not exceed 10% of control. The total number of interacting leukocytes, a parameter which includes both leukocyte rolling and adhesion in venules, increased up to 5 or 10 times its control value following 15 or 30 min ischemia, respectively. Leukocyte-vessel wall interactions could not be studied in the 60-min ischemia group, due to the low blood flow. CONCLUSIONS: Even short periods of total warm ischemia of the whole gut induce severe attenuation of venular blood flow with an increase in leukocyte-vessel wall interactions. These changes increase with prolongation of the ischemic period. A 60-min period of total warm ischemia is fatal during the early reperfusion phase.