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Effects of physical training in intermittent claudication

Mechanisms for increased claudication distance following physical training were studied in ten patients with peripheral arterial insufficiency. The exercise capacity on a bicycle ergometer increased by an average of 26% after 3--4 months of training (P less than 0.05). Neither maximum lower leg blood flow during the exercise test nor oxygen uptake at exhaustion changed significantly after training (-8% and +5%, respectively), whereas popliteal-venous O2-saturation was lower at exhaustion after the training than before (8.5 +/- 3.2 and 11.4 +/- 4.6, respectively, P less than 0.05). Anaerobic glycolysis, as evidenced by the lactate release, was also lowered after the training (P less than 0.05). In conclusion, the present study shows that the increased exercise capacity following physical training in claudicants is associated with an increased local aerobic working capacity despite a virtually unchanged blood flow. This increased aerobic exercise capacity might partly be explained by an increased O2 extraction in the lower leg during exercise.

Lower leg blood flow in intermittent claudication

Lower leg blood flow was measured at rest and both during and after graduated bicycle exercise in five healthy men and in seventeen patients suffering from various degrees of obliterating arteriosclerosis of the lower limbs. A thermodilution technique was used for flow determinations. The subject exercised in the sitting position and the work load was increased stepwise from a starting load of 100 kpm/min (100 kpm/min load increment every second minute until exhaustion). Three flow phases were depicted during and after the exercise: the aerobic phase, the phase of relative ischaemia and a postexercise phase. During exercise, lower leg blood flow increased approximately twenty times in healthy subjects, while in the arteriosclerotic subjects there was a two-fold to ten-fold increase in flow. In patients with serious distal and proximal stenoses a proximal steal phenomenon was demonstrated during submaximal and maximal exercise. A close correlation was found between maximum individual work load capacity and maximum lower leg blood flow (r = 0.71, P less than 0.001). In the patient group lower leg blood flow at a certain work load was 45% (P less than 0.001) higher in the sitting than in the supine position.

Endothelial cells of the cardiac microvasculature during and after cold cardioplegic ischaemia: Comparison of Endothelial and Myocyte Damage

Ultrastructural changes in endothelial cells of the myocardial microvasculature were studied in 18 patients who underwent aortocoronary bypass surgery under cold ischaemic cardioplegia. Biopsy specimens for electron microscopy were taken from the right atrium before and at the end of aortic cross-clamping and after 20 and 60 min of reperfusion. At the end of the cold ischaemic cardioplegia, the endothelial cells showed reduced numbers of pinocytotic vesicles, moderate intracellular oedema and slight nuclear changes. During reperfusion the endothelial changes became more pronounced and interstitial oedema developed. These changes persisted, or even increased in the first 60 min of reperfusion, in contrast to the myocytic changes, which tended to regress. The endothelial cells of the myocardial microvasculature thus appeared to be more vulnerable than the myocytes to cold ischaemic cardioplegia and reperfusion. Focally reduced blood reperfusion due to endothelial swelling and interstitial oedema did not seem to be the main cause of the focal postischaemic myocytic damage.

Multiply Beta-lactam Resistant Enterobacter cloacae Infections Linked to the Environmental Flora in a Unit for Cardiothoracic and Vascular Surgery

During the period March 1987-May 1988, postoperative infection or colonization with Enterobacter cloacae occurred in 9/379 (2.4%) patients who underwent cardiovascular surgery. Five of the patients were infected with multiply beta-lactam resistant E. cloacae, of whom 4 had been infected with an identical, resistant strain during intervals of months. This strain was also found in the environmental flora of the cardiovascular operating suite and in a sink reservoir in the surgery department. All 4 patients with the identical resistant strain had serious complications during the postoperative period with symptoms of septicaemia in 3, multiorgan failure and shock in 2, and mediastinitis in 3. The single resistant strain of a different serotype was also associated with severe postoperative complications. The 4 sensitive strains were all different serotypes. None caused septicaemia, one was associated with mediastinitis, another with an uncomplicated sternum infection, and 2 were from sputum. In the 3 latter patients with sensitive strains and few postoperative complications, cephalosporins had not been used during the pre- or postoperative period.

Superior myocardial protection with nicorandil cardioplegia.

OBJECTIVE The ATP-sensitive potassium channel (K(ATP)) activator nicorandil used as cardioplegic agent may protect the left ventricle during cardiac arrest. Nicorandil in cold blood was compared with standard hyperkalemic blood and crystalloid cardioplegia. METHODS Twenty-one pigs were randomly assigned to three groups: (1) cold hyperkalemic crystalloid (n=7); (2) cold hyperkalemic blood (n=7); and (3) nicorandil as cardioplegia in cold blood (n=7). Left ventricular mechanical performance, pressure-volume area (PVA) and myocardial oxygen consumption (MVO(2)) were measured before and at 1 and at 2 h after 60 min of cold global ischemia on cardiopulmonary bypass using intraventricular pressure-volume conductance catheters, coronary flow probes and O(2)-content difference. RESULTS The slope (M(w)) of the stroke work end-diastolic volume relationship, the preload recriutable stroke work relationship, was unchanged after ischemia in the nicorandil group, but was reduced to averaged 62.5% (standard deviation 14) of baseline values in both hyperkalemic perfusions (P<0.05). The slope of the MVO(2)-PVA relationship was unchanged after nicorandil cardioplegia while the slope after hyperkalemic blood and crystalloid cardioplegia increased with 33% (P<0.02) and 52% (P<0.02) of baseline values, respectively. CONCLUSIONS Nicorandil as sole cardioplegic agent in cold blood given intermittently preserves left ventricular contractility and myocardial energetics significantly better than traditional forms of cardioplegia after cardiac arrest.

Injury to Human Endothelial Cells in Culture under Conditions Simulating the Use of Vein Grafts for Vascular Surgery

In order to evaluate the effects of various vein graft preparation media at various temperatures, the 51Cr release from cultured human endothelial cells, and the percentage of loosened cells were determined after incubation of the cells with the media. Scanning electron microscopy (SEM) was carried out to visualize any injuring effect of the media. Incubation was performed with either heparinized sodium acetate (HS), HS with 20% human serum added (HSS), or with cell culture medium with human serum, at either 4, 20 or 37 degrees C. Incubation with HS resulted in considerable injury, measured both by 51Cr release and percentage of cell detachment. By SEM cell membrane blisters and ruptures were observed. Increasing the temperature aggravated the harmful effects of HS. HSS hampered these hazardous effects significantly, but a slight increase in 51Cr release was observed when increasing the temperature. When incubated with culture medium, both 51Cr release and percentage of loosened cells were low, even at room or body temperature. From the results of the present study it may be suggested that in order to preserve the venous endothelial lining, simple solutions like HS should be avoided for irrigation and store solution of vein grafts in surgery. As we found increased percentage of loosened endothelial cells when incubation was performed with HSS or culture medium at 4 degrees C, profound cooling probably has no beneficial effect when the endothelial cells are offered an acceptable fluid.

Determination of lower leg blood flow in man by thermodilution

A thermodilution method for measuring distal femoral vein flow in man is presented. The catheter is introduced percutaneously in central direction into the popliteal vein. Tests for accuracy in vitro (r = 0.999, range of true flow 63–2600 ml/min) and in dog experiments (r = 0.994, range of electromagnetic flow measurements 110–780 ml/min) are presented and discussed in relation to the anatomical (dissections on corpses) and functional conditions in the popliteal/distal femoral vein of man. A group of normal persons [7] and of patients suffering from ischaemic lower limb disease [17] were studied at rest and during exercise on an ergometer in supine and sitting positions. In all but two, reliable measurements were obtained. In the normals, a mean resting flow of 114 ml/min (range 82–140 ml/min) was found. The individual coefficient of correlation between load and flow measurements in the normals varied from 0.80 to 0.94 during stepwise increasing load exercise. No serious complications occurred. The method...

Leucocytes and cardiopulmonary bypass: in vitro production of oxygen free radicals and trapping in the reperfused myocardium

The production of oxygen free radicals (OFR) by leucocytes was evaluated ex vivo by chemiluminescence (CL) before, during and after routine coronary artery bypass surgery (group A, n=11). The possibility of leucocyte trapping in the coronary circulation during the early reperfusion period was also investigated (group B, n=9). In group A, arterial blood samples were taken immediately before the start of surgery during anaesthesia, five minutes before and five and 30 minutes after the start of cardiopulmonary bypass (CPB), five minutes before and five and 30 minutes after the start of reperfusion of the heart, and then four and 24 hours after the end of CPB. In group B, arterial and coronary sinus blood samples were simultaneously drawn five and 30 minutes after the release of the aortic crossclamp. All blood samples were corrected for haemodilution. In group A, both CL and the level of circulating leucocytes declined during CPB. The lowest value of CL was measured 30 minutes after the start of CPB (69± 2% of baseline values) (mean±SEM). The lowest level of leucocytes was found after 30 minutes of CPB: 2.6±0.4 (109/l) vs 4.2±0.5 before surgery. Twenty-four hours after CPB, CL was increased to 170±49% and a leucocytosis was present (12.2±1.1). In group B, after five minutes of reperfusion the number of circulating leucocytes in arterial blood was 3.8±0.9 x 10 9/l as compared to 2.2±0.5 x 109/l in the coronary sinus (p<0.0017). However, no such difference was found after 30 minutes of reperfusion. The decreased CL during CPB was probably due to in vivo activation and exhaustion of leucocytes. The postischaemic trapping of these cells may play a pathogenetic role in reperfusion injury.

Improved energy preservation following gentle reperfusion after hypothermic, ischemic cardioplegia in infarcted rat hearts.

The influence of temperature and pressure during early reperfusion after 2 h of hypothermic, cardioplegic ischemia was investigated. Adenosine triphosphate (ATP) and creatine-phosphate (CP) were measured after 45-min reperfusion. The experiments were carried out in normal and previously infarcted rat hearts (the left coronary artery having been ligated 3 weeks earlier). Four groups, each containing six hearts, were studied. Group 1 consisted of normal hearts reperfused with an abrupt rise in temperature and pressure, group 2 of normal hearts exposed to slowly rising temperature and pressure, and group 3 and 4 of previously infarcted hearts. Reperfusion procedures in groups 3 and 4 were the same as in group 1 and 2, respectively. The study showed that previously infarcted hearts have a lowered tolerance to ischemia and that the reperfusion technique may influence the preservation of myocardial energetics, although this influence was not statistically significant in normal hearts following only 2 h of ischemia. The gently reperfused infarcted hearts had energy stores equal to the normal hearts after 2 h of ischemia and 45 min of reperfusion, whereas the infarcted hearts reperfused in a rougher mode had significantly lowered values (P less than 0.05 for ATP and P less than 0.01 for CP).

Exercise-and post-exercise metabolism of the lower leg in patients with peripheral arterial insufficiency.

Exercise- and post-exercise metabolism were studied in the lower legs of six subjects without known arterial insufficiency and in sixteen claudicants. Lower leg blood flow was measured with a thermodilution catheter in the popliteal vein. The catheter allowed blood sampling from the calf before, during and after an exhaustive, stepwise increasing load exercise on a bicycle ergometer. A higher oxygen extraction and higher lactate release during exercise in claudicants than in normal subjects persisted in the post-exercise period (P less than 0.05). Leg arteriopoplitealvenous differences of free fatty acids (FFA) showed an inverse intergroup relationship to that of glucose. Being higher in claudicants than in normal subjects during exercise (P less than 0.05). However, net uptake of FFA was not significantly different in the groups of legs although it appeared increased relative to glucose in claudicants both during and after the exercise. Thus no statistically significant substrate preference was detected although the results suggests a preference for FFA relative to glucose in legs with arterial insufficiency. The study furthermore demonstrated the lag of exercise metabolism into the post-exercise period in such legs and a close relationship between this metabolic delay and the severity of the disease.