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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Since intermittent cardioplegic reperfusion during an ischemic period may reduce the ischemic stress of the heart at least by lowering myocardial temperature, we compared the post-ischemic recovery of the dog heart following cardioplegia and subsequent continuous ischemia of 1 X 300 minutes at 22 +/- 1 degree C (model 1) and following cardioplegia and subsequent 3 X 100 minutes of ischemia at 17 +/- 1 degree C with intermittent 4-minute cardioplegic reperfusion every 100 minutes (model 2). The parameters of post-ischemic recovery were the cardiac O2 consumption per beat at work (MVO2-E0): HR), the stability of cardiac rhythm, the left ventricular content of high-energy phosphates, and ultrastructure. Solution HTK with a magnesium concentration of 9 mM/L, in clinical use up to the beginning of 1984, resulted in a significantly better post-ischemic recovery in model 1, despite about 40% lesser ischemic stress in model 2. A reduction of Mg concentration from 9 to 4 mM/l, as in the HTK solution clinically tested since February 1984, did facilitate the post-ischemic recovery in model 1 as indicated by the stability of cardiac rhythm but led to a significant improvement of all parameters of recovery in model 2. Moreover, recovery in model 2 after reduced Mg was also clearly better than in model 1 corresponding to the lesser ischemic stress. The parameters myocardial O2 consumption (MVO2) and potassium loss during HTK perfusion containing 9 and 4 mM/l, respectively, gave indications of specific membrane labilizing effects of Mg in the cardioplegic solution HTK.
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PMID:Different effects of cardioplegic solution HTK during single or intermittent administration. 608 14

The aims of this study were (1) to investigate the effect of R 75231, a nucleoside transport inhibitor, on renin-angiotensin release after renal ischemia-reperfusion and (2) to establish a possible protective effect of this drug on renal function. We used a canine model for auto- transplantation of kidneys that had been subjected to 30 min of warm ischemia and subsequently to 24h of cold storage in HTK preservation solution, with immediate contralateral nephrectomy. R 75231 was injected intravenously into six dogs in two equal portions of 0.05 mg/kg both 30 min and 10 min before reanastomosis was established. Another six dogs were used as a control group. At 2 weeks post-transplantation, five out of six dogs in the R 75231 group and one out of six in the control group were still alive. Starting on day 4, serum creatinine was lower in the R 75231 group than in the control group (p < 0.005). In contrast to the control group, an inversion of the median preischemia adenosine/inosine ratio was observed in the R 75231 group after reperfusion (0.4 preischemia vs 4.0 after 60 min of reperfusion). Reperfusion of the graft resulted in an immediate increase in renin, angiotensin I, and angiotensin II venous blood levels in the control group. In the R 75231 group, renin, angiotension I, and angiotensin II levels were significantly lower. We conclude that administration of R 75231 before reperfusion has a protective effect on post-transplant function of kidneys that have been subjected to prolonged warm ischemia. This effect may, at least in part, be ascribed to inhibition of the breakdown and disposal of endogenous adenosine which, in turn, inhibits the excessive stimulation of the renin-angiotensin system in the early phase of reperfusion.
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PMID:Protection of canine renal grafts by renin-angiotensin inhibition through nucleoside transport blockade. 762 81

Investigations of changes in activity of renin and blood pressure after reperfusion of the kidney transplant using HTK solution were carried out by means of an autologous, heterotopic model of kidney transplantation applied to dogs. Duration of cold ischemia was 48 h. According to variations in the composition of the HTK perfusion solution three test groups were set up. During the first 20 min after recirculation in each test group the renal venous and arterial renin activities were measured. Parallel to renin activity, the arterial blood pressure was recorded. During the first few minutes following recirculation of the kidney transplant the renin levels in the venous blood of the kidney were higher in test group 1 (HTK solution, perfusion height 120 cm) than in either of the other two, showing a median maximal increase of 195 ng/ml.h. In test group 2 the maximal venous renin concentration fell to 145 ng/ml.h, while graphs take a more uniform course. Test group 3 (HTK/tryptophan) differed from the others in having further improved renin values. After the 7.5 min of observation normal venous renin concentrations were measured following earlier values for maximal increase between 23.1 ng/ml.h and 120 ng/ml.h (median 61.5 ng/ml.h). The best reperfusion of the kidney was observed in the tryptophan group, albeit without any recognizable positive effects on the other renal functions. Initially low renin values do not necessarily correlate with a smooth postoperative renal function and vice versa. Initial renin values cannot provide a secure basis for predicting instant as well as long-term postoperative functions.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Change in renin activity and blood pressure in the dog autologous kidney transplant model with modified HTK solution]. 776 Jun 55

This study was undertaken in order to obtain information on the mode of reaction of the contractile apparatus after different forms of cardiac arrest, global ischemia and reperfusion, as well as on possible correlations between the contraction state of myofibrils and biochemical parameters. During the survival time, before the level of 3 mumol/gww creatine phosphate (CP) is reached, the contraction state shows only minor changes. During the revival time in which ATP tissue concentrations decay to 4 mumol/gww, the contribution of ATP, lactate, anorganic phosphate (Pa) and acidosis to the degree of relaxation depends on the method of cardiac arrest. At defined biochemical values, the degree of relaxation is comparable after aortic cross clamping (ACC) and St. Thomas perfusion, but significantly different compared to HTK perfusion. Thus, during the revival time, the relaxation of sarcomeres depends predominantly on the composition of the solutions used for cardiac arrest. The re-entry of contraction below 3 mumol/gww ATP is correlated with the ATP concentration, independent of the form of cardiac arrest. Reperfusion after HTK or St. Thomas cardioplegia and reversible ischemia leads to the focal formation of contraction bands, which do not occur during ischemia. This contraction state is significantly more pronounced after reperfusion of St. Thomas arrested hearts. Thus, the contraction state of myofibrils is influenced not only by alterations in metabolite concentrations, but also by the composition of cardioplegic solutions and by the characteristic conditions (sufficient energy, oxygen and Calcium) during reperfusion.
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PMID:The contraction state of myofibrils during global ischemia and after reperfusion following different forms of cardiac arrest. Correlation with metabolic parameters in the canine heart. 799 68

The efficiency of a preservation medium, histidine-buffered lactobionate solution (HBLS), was determined by measuring post-ischemic recoveries of ATP and intracellular pH under Krebs-Henseleit buffer (KHB) perfusion. We used NMR spectroscopy to study the effect of 24-h cold ischemia, followed by 4 degrees C then 37 degrees C reperfusion on the isolated rat liver. Three media were compared: University of Wisconsin solution (UW-lactobionate); Bretschneider's solution (HTK); HBLS and HBLS supplemented with 2 mM Gly and 2 mM Cys (HBLSg2) or with 10 mM Gly and 2 mM Cys (HBLSg10). All values were compared to control values measured during pre-ischemic cold perfusion with KHB (ATP = 8.60 +/- 0.6 mumol/g of dry weigh and pH(in) = 7.41 +/- 0.05). The main result from 31P NMR data concerned ATP recovery during cold reperfusion, which was significantly higher in the HBLS group (112 +/- 10%) as compared to the UW and HTK groups (around 66%). The presence of glycine decreased ATP recovery (88 +/- 8% in HBLSg2, 79 +/- 15% in HBLSg10). Higher values of recovered pHin were observed in livers stored in histidine buffered solutions (around 7.30) as compared to UW (around 7.20); histidine was by 13C NMR proved to accumulate in the liver cells, thus ensuring a good buffering capacity. The thermal transition induced a decrease in both ATP level and pHin in all groups. This might be the result of a stimulation of the carbohydrate metabolism (as demonstrated by 13C NMR) especially when glycine was present in the storage solution.
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PMID:31P NMR studies of rat liver cold preservation with histidine-buffered lactobionate solution. 830 4

This study investigates how far mitochondrial swelling in the ischemic heart is influenced by factors pertaining to anaerobic energy turnover. Canine hearts were arrested by aortic cross clamping or cardioplegically with St. Thomas or HTK solution and incubated at 25 degrees C in the solution used for cardiac arrest. Samples of the left ventricle were taken at the end of cardiac arrest and during ischemia for structural evaluation and biochemical analysis. The extracellular pH in the interventricular septum was measured. Mitochondrial swelling was determined with the surface to volume ratio, a parameter independent of the reference space. Values obtained for different swelling were related to defined metabolite concentrations and pHe values to establish possible correlations between structural and biochemical parameters in the ischemic heart. At the onset of ischemia and during the breakdown of creatine phosphate (CP) to 3 mumol/g wet weight mitochondrial volume depends on the method of cardiac arrest and does not increase significantly in any of the three groups. The degree of mitochondrial swelling after depletion of CP correlates with the decline in ATP independent of the form of cardiac arrest. Characteristic values of the surface to volume ratio ascertained at different times of ischemia for all groups correspond to determined ATP concentrations. Acid pHe values seem to intensify mitochondrial swelling. With increased lactate concentrations mitochondria swell, but first initially the degree of swelling differs significantly in the forms of cardiac arrest investigated. Thus, the surface to volume ratio is a powerful and valid ultrastructural parameter, which makes correlations between mitochondrial structure and metabolism possible and furthermore indicates a strong correlation between mitochondrial swelling and ATP-concentration in the ischemic heart.
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PMID:Close correlations between mitochondrial swelling and ATP-content in the ischemic canine myocardium. A combined morphometric and biochemical study. 833 76

This study compares the ultrastructure of beating canine hearts with that of hearts subjected to different clinically common forms of cardiac arrest. The contraction state per test field was ascertained according to a specially developed classification. The volume density of myofibrils and the surface to volume ratio of mitochondria were used as parameters for cellular and mitochondrial swelling. Contraction bands were not found in any of the differently pretreated hearts. Following immersion fixation, contractions as well as over- and hypercontractions in beating, fibrillating, and St. Thomas-arrested hearts are significantly more pronounced than in HTK-arrested hearts. Cellular and mitochondrial volumes were similar in beating and fibrillating hearts. St. Thomas-perfusion significantly decreased cellular and mitochondrial volume compared to beating hearts, but these values were in the same range as in fibrillating hearts. Only HTK-solution actually led to a strong reduction of these compartments. Compared to immersion, perfusion fixation after coronary perfusion with cardioplegic solutions led to comparable cellular volumes, but significantly elevated the percentage of relaxed sarcomeres and significantly reduced mitochondrial swelling. The best structural preservation of myocytes was found after HTK-perfusion and perfusion fixation. Such ultrastructural quantitative and morphometrical parameters are powerful tools since results confirm that the degree of myocardial preservation depends on the method of cardiac arrest. This forms the basis for the choice of preconditions for subsequent ischemia. Furthermore, significant alterations of myocardial ultrastructure depend on a combination of the functional state of the heart, the method of cardioplegia, and the technique of fixation.
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PMID:Preservation of cardiac myocytes subjected to different preconditions: a comparative morphometric study of beating, fibrillating, and cardioplegically arrested canine hearts. 843 Sep 12

The regeneration of peripheral nerve grafts was evaluated in a rat model, after pretreating the grafts with Schwann cell culture medium, HTK organ preservation solution, and normal saline, under cold ischemic conditions for different time periods. Following orthotopic replantation of the grafts into donor animals, the quality of regeneration was assessed after 6 weeks, compared to positive controls (autologous transplantation) and negative controls (acellular grafts). The regenerative quality in the Schwann cell culture groups with ischemic periods of 32 and 72 hr was comparable to normal controls. Significantly minor regeneration was detected in specimens undergoing 14 and 120 hr of ischemia in the Schwann cell culture medium and in the HTK and normal saline groups, regardless of ischemic time. Among the conclusions was that controlled proliferation of Schwann cells seems to be a basic principle for preservation of peripheral nerve grafts.
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PMID:Preservation of peripheral nerve grafts: a comparison of normal saline, HTK organ preservation solution, and DMEM Schwann cell culture medium. 858 58

The aim of this study was to investigate the efficacy of HTK solution for cardioplegia in the continuous 120-minute cross-clamping method in comparison with the conventional GIK method. In an experimental model, the efficacy of ketoglutarate and tryptophan in recovering cardiac function after 6 hours' preservation was evaluated. In Group A, in which ketoglutarate was excluded from the HTK solution, percent developed pressure was significantly decreased (p<0.01) and the released enzyme (CK-MB) was significantly increased, but coronary flow was not significantly changed. In Group B, in which tryptophan was excluded from the HTK solution, a significant decrease in percent developed pressure and coronary flow was seen (p<0.01). This indicated that ketoglutarate and tryptophan were effective in protecting the myocardium during the ischemia. In the clinical study, 54 open heart operations were performed with cardioplegic solution, using either HTK solution or GIK solution. In the HTK Group, the heart was exposed to 120 minutes' of ischemia after the infusion of HTK solution (3L). In the GIK group, intermittent GIK perfusion was performed every 30 minutes in association with continuous cold blood perfusion. Percent fraction shortening and cardiac index were not significantly different. However, CK-MB and HBDH were increased in the GIK group, postoperatively. Histological findings showed deterioration of the mitochondria and myocytes during ischemia in the GIK group. These data suggest that the effect of the cardioplegias in heart preservation was satisfactory in both groups, although the interval of intermittent perfusion was prolonged to 120 minutes in the HTK solution.
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PMID:Effect of HTK solution for myocardial preservation. 869 63

Myocardial infarction in consequence of a coronary artery occlusion presents a serious problem. It is the aim of any emergency revascularization to minimize the ischemia-induced damage or to salvage reversibly injured myocardium. In experiments on 8 anesthetized pigs, myocardial protection by orthograde perfusion with a high-volume cardioplegic solution was studied under controlled conditions. The left anterior descending artery (LAD) was occluded for 60 min. Then cardiopulmonary bypass was instituted and cardioplegia induced by 8 min perfusion of Bretschneider HTK solution into the aortic root. After 15 min global ischemia, the LAD was "revascularized' and 150 min reperfusion followed. Except for the early relaxation (dP/dtmin) and mean thickening velocity in the ischemic myocardium, all variables remained essentially unchanged during LAD occlusion. During the entire reperfusion, heart rate was significantly increased compared to control: 93 +/- 23 vs. 126 +/- 20/min. Left-ventricular (LV) peak pressure was significantly decreased at the end of the reperfusion, 104 +/- 33 and 77 +/- 22 mmHg, as was dP/dtmax:2155 +/- 655 vs. 1720 +/- 895 mmHg/s. Cardiac output was insignificantly decreased at the end of reperfusion, 2.6 +/- 0.6 vs. 2.4 +/- 0.5 L/min, whereas stroke-work index exhibited a significant deterioration: 1.2 +/- 0.6 vs. 0.5 +/- 0.3 mmHg.ml/kg. LV dP/dtmin was significantly impaired after ischemia and at the end of reperfusion, -1575 +/- 385 vs. -855 +/- 310 mmHg/s, while LV end-diastolic pressure exhibited only a moderate increase: 8 +/- 5 vs. 9 +/- 3 mmHg. MVO2, in turn, remained almost constant throughout the protocol for each of two methods by which it was predicted. The results show that global work, MVO2, and external efficiency were unchanged during early and late occlusion compared to control. During the entire reperfusion the myocardium was stunned, i.e. cardiac work was decreased at maintained MVO2. Thus, external efficiency was decreased. From these results we conclude that in reperfused myocardium after cardioplegic arrest, the oxygen is only inefficiently converted to develop force.
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PMID:Cardiac efficiency during coronary occlusion and during reperfusion after emergency revascularization under cardioprotection. 872 96


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