Preservation of myocardial function by mechanical circulatory support during prolonged ischaemia

The effect of mechanical circulatory support on left ventricular (LV) function was evaluated during prolonged myocardial ischaemia. Regional wall thickening of a normal and an ischaemic LV region were determined in eight calves (mean body weight 76 kg) using pairs of ultrasonic crystals. LV end-diastolic (mmHg) and peak systolic (mmHg) pressure as well as maximum dP/dt (mmHg s−) were calculated from LV high-fidelity pressure tracings. The left circumflex coronary artery was ligated proximally for 6 h and reperfused for 18 h. Circulatory support by the assist device was performed from the beginning of ischaemia to the end of the experiment. After a mean time of 4 h all animals showed ventricular fibrillation, which was converted successfully in six animals after a mean time interval of 5 h. Five animals survived after 24 h. The non-surviving animals had larger infarcts, greater creatine kinase release and a larger drop in cardiac output during ischaemia. Haemodynamic measurements were carried out after turning off the assist device. Inotropic stimulation with 0-68 mg . min− dopamine i. v. was performed at the end of the study. LV regional function showed systolic bulging during myocardial ischaemia. After 18 h of reperfusion, the ischaemic wall recovered and showed normal systolic wall thickening in the presence of an increased LV preload. LV relaxation was prolonged after reperfusion, suggesting diastolic dysfunction. It is concluded that mechanical circulatory support is effective in protecting myocardial function during prolonged ischaemia in approximately two-thirds of the animals, despite severe ischaemic ventricular dysfunction and intermittent ventricular fibrillatio

Left ventricular volume determination in dogs: a comparison between conductance technique and angiocardiography

Left ventricular (LV) volume was determined simultaneously by monoplane cineangiocardiography and conductivity using a multielectrode conductance catheter at rest and during pressure loading in seven mongrel dogs (mean body weight 22 kg). LV volumes were calculated frame-by-frame (75 frames s−1) by angiocardiography and matched with instantaneous volumes obtained by conductivity. There was an excellent correlation between the two techniques at rest (correlation coefficient, r = 0.96) and during pressure loading (r = 0.92) when the data of each dog were pooled. The standard error of estimate of the mean angiographic volume was 4%. The slope of the regression analysis showed a small but significant (P <0.01) decrease from 0.365 at rest to 0.289 during pressure loading, whereas the intercept remained unchanged (24 versus 26 ml). Since no calibration for parallel conductivity of the surrounding tissue was performed, LV end-systolic volume was significantly over- and LV ejection fraction significantly underestimated whereas LV end-diastolic volume was estimated correctly by the conductance technique. It is concluded that LV end-diastolic volume can be determined accurately by the conductance technique in dogs. However, LV end-systolic volume is significantly over- and ejection fraction significantly under-estimated. Since there is a good correlation between angiocardiography and conductivity, exact determination Of LV volumes and ejection fraction is feasible using a correction factor. The change is slope of the regression equation between angiocardiography and conductivity suggests a change in conductivity of the surrounding tissue during pressure loading which limits the application of the conductance catheter to stable haemodynamic situations or calls for repeated calibrations by an independent technique during acute intervention

Regional diastolic dysfunction in postischaemic myocardium in calf: effect of nisoldipine

Objective: The aim was to assess the effect of nisoldipine on left ventricular systolic and diastolic function during prolonged myocardial ischaemia. Methods: The left circumflex coronary artery was ligated for 2 h and reperfused for 4 h in 12 calves. The animals were randomised to a control group (n=6) or to treatment with 1.25 mg·h−1 intravenous nisoldipine (n=6) during 2 h of ischaemia. Circulatory support by a ventricular assist device was performed throughout the experiment except for the time of haemodynamic measurements. Regional wall thickening of a normal and an ischaemic left ventricular region was determined using pairs of ultrasonic crystals. Left ventricular pressure was measured by micromanometry. Left ventricular wall thickness and regional wall stiffness at a common preload of 10 mm Hg were calculated using an elastic model with shifting asymptote. Results: Ten animals survived after 6 h. No difference was observed in systolic function between controls and nisoldipine treated animals. Systolic thickening of the ischaemic wall remained depressed 4 h after reperfusion and showed some recovery after dopamine infusion. Ischaemic wall stiffness at a common preload was lower after nisoldipine during ischaemia and reperfusion than in controls. Control wall stiffness remained unchanged during the whole experiment with and without nisoldipine. Diastolic thinning of the ischaemic wall was prevented by nisoldipine during ischaemia and after reperfusion. Conclusions: Prolonged myocardial ischaemia is associated with increased myocardial stiffness of the ischaemic wall. Mechanical unloading can help to bridge the acute phase but cannot prevent postischaemic diastolic dysfunction of the ischaemic wall. Nisoldipine has a beneficial effect on regional diastolic function during ischaemia and reperfusion by decreasing regional wall stiffness and preventing diastolic thinning of the ischaemic wall. Cardiovascular Research 1993;27:531-53

Does retrograde cerebral perfusion via superior vena cava cannulation protect the brain?

OBJECTIVE: The retrograde cerebral perfusion via cannulation of the superior vena cava is a widespread method for optimising protection of the brain during hypothermic circulatory arrest. METHODS: In 14 cadavers (8 females, 6 males) of the local department of pathology, an examination was performed to check the competence of the valves of the internal jugular veins. After a complete preparation of the superior vena cava, the innominate vein and both internal jugular veins, ligating all side branches, a retrograde perfusion on 7 cadavers was installed, documenting flow and pressure of each internal jugular vein (IJV) in vitro. Afterwards, the veins were opened and their valves inspected. RESULTS: In all 14 cadavers, anatomically and functionally competent valves on the right proximal IJV were found. Only 1/14 cadaver had no valve in the left proximal IJV. Additional rudimentary and incompetent valves could be identified in 1/14 cadaver on the distal right IJV, and in 2/14 cadavers on the left IJV. Retrograde flow measurement of 7/14 cadavers revealed 0 ml/min in 4/7 cadavers, 6 ml/min in 1/7, 340 ml/min in 1/7 and 2500 ml/min in 1/7 cadaver. CONCLUSIONS: As a rule, anatomically and functionally competent valves in the proximal IJV are present. In human beings, they obstruct the direct retrograde inlet to the intracranial venous system, which suggests an unbalanced and unreliable perfusion of the brain. Therefore, retrograde cerebral perfusion by cannulating the superior vena cava may help flushing out embolism and supporting 'the cold jacket' of the brain. However, its effect of retrograde backflow cannot be a sign of adequate cerebral perfusion

Optimization of venous return tubing diameter for cardiopulmonary bypass

OBJECTIVE: To determine the optimal venous tubing diameter for adult cardiopulmonary bypass (CPB) to improve gravity drainage and to reduce priming volume. METHODS: (A) Maximum bovine blood flow rates by gravity drainage were assessed in vitro for four different tubing diameters (1/2, 3/8, 5/16,1/4 inch) with three different lengths and various pre- and afterloads. Based on the results of (A) and multiple regression analyses, we developed equations to predict tubing sizes as a function of target flows. (C) The equations obtained in (B) were validated by ex vivo bovine experiments. (D) The clinically required maximal flows were determined retrospectively by reviewing 119 perfusion records at Zurich University. (E) Based on our model (B), the clinical patient and hardware requirements, the optimal venous tubing diameter was calculated. (F) The optimized venous tubing was evaluated in a prospective clinical trial involving 312 patients in Hangzhou. RESULTS: For a mean body surface area of 1.83+/-0.2 m(2), the maximal perfusion flow rate (D) achieved with 1/2-inch (=1.27 cm(2)) venous tubing was 4.62+/-0.57 l/min (range: 2.50-6.24 l/min). Our validated model (B,C) predicted 1.0 cm(2) as optimal cross-sectional area for the venous line. New tubing packs developed accordingly were used routinely thereafter. The maximal flow rate was 4.93+/-0.58 l/min (range: 3.9-7.0) in patients with a mean body surface area of 1.62+/-0.21 m(2). CONCLUSION: The new venous tubing with 1.0-cm(2) cross-sectional area improves the drainage in the vast majority of adult patients undergoing CPB and reduces the priming volume (-27 ml/m). Reduced hemodilution can prevent homologous transfusions if a predefined transfusion trigger level is not reached

Diminishing benefits of urban living for children and adolescents’ growth and development

Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income&nbsp;countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was &lt;1.1 kg m–2 in the vast majority of&nbsp;countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified

Mechanische Kreislaufunterstutzung mittels miniaturisierter Archimedischer Schraube. [Mechanical circulatory assist using a miniaturized Archimedes screw]

An axial flow blood pump (Archimedes screw) for intraarterial left ventricular assist was evaluated in comparison to standard roller pump left heart bypass (LHBP) in 13 bovine experiments (bodyweight 74 +/- 15 kg). Full systemic heparinization (ACT greater than 500 s) was used for LHBP in comparison to limited systemic heparinization (ACT greater than 180 s) for axial. A standard battery of blood samples was taken before and at regular intervals throughout perfusion: (table; see text) Transarterial access and relatively limited blood trauma appear to be the main advantages of the evaluated axial flow blood pump. However, the impossibility to assess the pump flow may be a major problem for the management of the failing left ventricle

Injuries Among Slovenian Physical Education Teachers: A Cross-Sectional Study

A cross-sectional study was carried out to examine the frequency and types of serious injuries in physical educators throughout their professional career, in relation to their gender, age and teaching level, certain factors causing the injuries and the consequences of those injuries on their working ability. The subjects (n = 468) answered a self-administered questionnaire. In men, one group's higher frequency of injuries was 1.8 (95% CI [1.26, 2.57]) times higher than in women. Every year in age increased the odds for moving into a group with a higher frequency of injuries by 7.6% (95% CI [1.06, 1.10]). The most common injuries for both genders were lower limb injuries. The most common cause of injury was the teacher's own mistake. Over 60% of teachers had to modify their teaching after an injury. It is necessary to further explore preventive strategies to reduce injuries in these workers