Controlled reperfusion reduces hemorheological alterations in a porcine infrarenal aortic-clamping ischemia-reperfusion model.

INTRODUCTION: Restoration of blood flow after prolonged acute ischemia causes further injury to tissues. The role of increased oxidative stress is emphasized in the pathogenesis, and impairment of hemorheological factors may also hinder proper microcirculation. Controlled reperfusion at lowered pressure with diluted blood may help to decrease reperfusion injury. METHODS: Four-hour infrarenal aortic clamping was performed in 16 Yorkshire pigs. In 8 animals blood flow was restored subsequently (full reperfusion, FR), in the other 8 animals clamping was followed by an initial 30 minutes of controlled reperfusion (CR) at 60 mmHg pressure with a 1 : 1 ratio mixture of blood and reperfusion solution. Blood samples were taken before the intervention, at the end of ischemia, 15 minutes, 60 minutes, 1 day and 1 week after the start of reperfusion. Hemorheological parameters were measured. RESULTS: Hematocrit, plasma and whole blood viscosity decreased significantly during CR, these attenuated at 1 day. At 1 week whole blood and plasma viscosities were elevated in the FR group. Erythrocyte deformability did not change significantly at any measurements. Erythrocyte aggregation decreased during CR but not in FR, and was found elevated in both groups at 1 week. CONCLUSION: Our results suggest slightly improved hemorheological properties in case of controlled reperfusion compared to full reperfusion, which may help to reduce tissue damage.

Antiplatelet effect of acetylsalicylic acid, metamizole and their combination - in vitro and in vivo comparisons.

BACKGROUND: Acetylsalicylic acid (ASA) plays an important role in the treatment and prevention of cardiovascular diseases. Metamizole (MET) is an analgesic and antipyretic medicine, it is not used as an antiplatelet drug. OBJECTIVES: We aimed to examine the antiplatelet effect of MET and the possible interactions between the drugs. METHODS: In our in vitro investigations different concentrations of ASA and MET solutions were added to blood. To examine the interactions MET and ASA were added together. In our in vivo crossover study intravenous MET, oral ASA or both drugs together were administered. Epinephrine and adenosine-diphosphate induced platelet aggregation was determined by optical aggregometry. RESULTS: Epinephrine-induced aggregation was completely inhibited in all ASA and MET concentrations in vitro. Lower, ineffective concentration of MET prevented the antiplatelet effect of ASA. The inhibition was completely restored when higher concentration of ASA was used or when ASA was added first. Our in vivo study showed that in the MET group rapid onset of inhibition was developed and there was no inhibition after one day. In the ASA group platelet aggregation decreased slowly but still had significant inhibitory effect after 72 hours. Combined therapy showed similar changes to the MET group. CONCLUSION: Antiplatelet effect of MET and ASA did not differ significantly in vitro. The observations may indicate a competitive interaction between the two drugs. The in vivo experiments showed that intravenously administered MET is an effective antiplatelet drug and can be considered as a therapeutic alternative, when ASA cannot be used in oral form.

Effects of ethanol on red blood cell rheological behavior.

Consumption of red wine is associated with a decreased risk of several cardiovascular diseases (e.g., coronary artery disease, stroke), but unfortunately literature reports regarding ethanol's effects on hemorheological parameters are not concordant. In the present study, red blood cell (RBC) deformability was tested via laser ektacytometry (LORCA, 0.3-30 Pa) using two approaches: 1) addition of ethanol to whole blood at 0.25%-2% followed by incubation and testing in ethanol-free LORCA medium; 2) addition of ethanol to the LORCA medium at 0.25%-6% then testing untreated native RBC in these media. The effects of ethanol on deformability for oxidatively stressed RBC were investigated as were changes of RBC aggregation (Myrenne Aggregometer) for cells in autologous plasma or 3% 70 kDa dextran. Significant dose-related increases of RBC deformability were observed at 0.25% (p < 0.05) and higher concentrations only if ethanol was in the LORCA medium; no changes occurred for cells previously incubated with ethanol then tested in ethanol-free medium. The impaired deformability of cells pre-exposed to oxidative stress was improved only if ethanol was in the LORCA medium. RBC aggregation decreased with concentration at 0.25% and higher for cells in both autologous plasma and dextran 70. Our results indicate that ethanol reversibly improves erythrocyte deformability and irreversibly decreases erythrocyte aggregation; the relevance of these results to the health benefits of moderate wine consumption require further investigation.

Moderate red wine consumption improves hemorheological parameters in healthy volunteers.

Pieces of epidemiological evidence have supported that moderate red wine consumption reduces the risk of cardiovascular diseases (French-paradox). Our previous in vitro experiment has demonstrated favourable hemorheological effects of red wine, alcohol-free red wine extract and ethanol. Thirty-nine healthy, non-smoking male volunteers between 18-40 years were assigned into two groups: control group had drunk water, while red wine group had consumed 2 dl of red wine each day at dinner for 3 weeks. No alcohol had been drunk for one week prior to the study. Blood was obtained in the morning of the first and last day. Hematocrit (Hct), plasma (PV) and whole blood viscosity (WBV) (Hevimet 40 capillary viscometer), red blood cell (RBC) aggregation (Myrenne and LORCA aggregometer) and deformability (LORCA ektacytometer) were measured and Hct/WBV ratio was calculated to determine oxygen carrying capacity. Hct was adjusted to 40%. Hct and PV were not affected. WBV remained unchanged in controls, but it considerably decreased in the red wine group compared to the 3-week control group, while Hct/WBV ratio became significantly higher in the red wine group compared to the control (p < 0.05). RBC aggregation significantly decreased in the red wine group and became significantly lower compared to the 3-week controls (p < 0.05). Red wine significantly increased RBC deformability (p < 0.05) at high shear stress. Our results show that moderate red wine consumption has beneficial effects on hemorheological parameters which may contribute to the French-paradox.

The role of hemorheological factors in cardiovascular medicine.

Cardiovascular diseases (CVD) are the most frequent cause of death throughout the world. The coronary vessel system is a special part of the circulation since there is a continuous change in blood flow, perfusion pressure and shear rate during each cardiac cycle. It is also the place of the narrowest capillaries in the human body, therefore the role of rheological alterations may be of greater importance than in the other parts of the circulatory system. During the past decades, our group has investigated hemorheological parameters (HP) in over 1,000 patients diagnosed with various forms of ischemic heart disease (IHD). In one prospective study, we measured the HP of patients with acute coronary syndrome (ACS). On admission, all examined variables were significantly worse than those of control subjects. During the hospital phase, some of the HP showed further deterioration, and HP remained in the pathologic range during the follow-up period. In another study, we showed that HP are in close correlation with the severity of coronary artery disease. In patients treated with percutaneous coronary intervention, changes in HP were very similar to those observed in subjects with ACS. In a recent study, we analyzed HP in patients undergoing CABG surgery. Our data suggest a hemorheological advantage of off-pump surgery. In another study low Hct/WBV ratio can be regarded as a risk factor of cardiac death in IHD. Our data indicate that rheological parameters are significantly altered in patients with IHD: the extent of the alterations is in excellent correlation with the clinical severity of the disease. Our findings prove that HP play a critical role in the pathogenesis of myocardial ischemia. In recent in vitro and in vivo studies we have investigated the effects of red wine on hemorheological parameters. Our results show that moderate red wine consumption has beneficial effects on hemorheological parameters which may contribute to the French paradox.

Reviewing data reduction methods for ektacytometry.

Ektacytometry quantifies erythrocyte deformability by measuring the elongation of suspended red blood cells subjected to a range of shear stresses. Raw shear stress-elongation index plots are difficult to interpret and thus data reduction methods characterizing the relationship using few parameters without loss of information and good reproducibility are essential, especially for the clinician. Two such curve fitting formulas, used widely in the literature for this purpose, are reviewed herein. The Lineweaver-Burke method overestimates maximal deformability if shear stresses below 1 Pa are applied. A modified version of the formula estimates maximal deformation more accurately but gives little weight to data at low shear stresses. Neither method is accurate if negative elongation indices are present (artifact phenomenon when measurement is performed from high to low shear stresses). The Streekstra-Bronkhorst method provides efficient data reduction though the theoretical background of the formula is incorrect. The parameters have expressive meaning; however, both maximal and minimal deformations are slightly underestimated. Moreover, parameters are biased according to the range of measured shear stresses.

The influence of on-pump and off-pump coronary artery bypass grafting on hemorheological parameters.

Conditions during coronary artery bypass grafting (CABG) performed on beating heart (off-pump) are more physiological than using extracorporeal perfusion (on-pump). The present study aims to examine the hemorheological aspects of the two techniques. Blood samples were taken from patients undergoing on-pump (n = 25) and off-pump (n = 22) CABG, upon arrival to the operating theatre, after 20 and 40 minutes during the operation, after closing the thorax, on the 1st and 2nd postoperative days, and during the 2nd and 6th month control check-ups. Hematocrit (Hct), plasma and whole blood viscosity (PV, WBV; Hevimet 40 capillary viscometer), red blood cell (RBC) aggregation (Myrenne RBC aggregometer, LORCA) and deformability (LORCA, Carat FT-1 filtrometer), and platelet aggregation (Carat TX4 aggregometer) were determined. The morphology of red blood cells was investigated by scanning electron microscopy (SEM). Hct, PV, WBV and RBC aggregation decreased significantly during the early phase of the surgery, they started to recover during the postoperative period, and reached the baseline values by the 2nd and 6th month control check-ups. These parameters were significantly lower in samples taken after 20 and 40 minutes in the on-pump group. SEM showed rather damaged and malformed cells in case of on-pump surgery. Ektacytometry showed no significant difference, but RBC deformability was impaired during on-pump surgery when measured by filtrometry. The decrease in platelet aggregation was more pronounced by the end of surgery in case of on-pump technique. During CABG rheological parameters change less when using the off-pump method, and mechanical damage of RBCs are also smaller. The off-pump technique seems to be favorable from a hemorhelogical point of view.

In vitro hemorheological effects of red wine and alcohol-free red wine extract.

The French paradox is based on epidemiological evidence which supports that moderate red wine consumption reduces the risk of cardiovascular diseases. A number of experimental animal studies reported favourable cardiovascular effects of alcohol-free red wine extract (AFRW). Our study was designed to determine red wine and AFRW induced changes in various hemorheological parameters. These effects may play a role in the pathophysiology of the French paradox regarding the cardiovascular protective impacts of red wine. Blood samples of healthy volunteers were mixed with red wine to achieve alcohol concentrations of 1 per thousand, 3 per thousand and 10 per thousand, respectively, with equivalent amount of AFRW or physiological saline. Blood samples were pretreated with red wine or AFRW in order to prove the protective effects on erythrocytes from impairment of deformability caused by the free radical generator phenazine methosulfate (PMS). Erythrocyte aggregation (Myrenne and LORCA), deformability (LORCA) and platelet aggregation (Carat TX4) were measured. Erythrocyte aggregation using Myrenne aggregometer was inhibited by red wine and AFRW compared to the saline treated samples. The difference reached already significance at 1 per thousand concentration at the AFRW samples (p < 0.05). Furthermore, red wine caused stronger inhibition than AFRW. The difference between the two agents became significant at 10 per thousand concentration (p < 0.05). LORCA aggregation index and threshold shear rate supported these results at the highest concentration. Erythrocyte deformability of healthy volunteers did not change significantly for any concentrations of red wine and AFRW. On the other hand AFRW at 3 per thousand concentration significantly prevented erythrocytes from impairment of deformability caused by PMS (p < 0.05). Platelet aggregation was significantly inhibited by the highest concentration of AFRW (p < 0.05). Our results show that red wine and AFRW have some beneficial effects on hemorheological parameters that may contribute to the French paradox.

Correlation between oxytocin neuronal sensitivity and oxytocin-binding sites in the amygdala of the rat: electrophysiological and histoautoradiographic study.

Central nucleus (Ce), basomedial and medial nuclei of the amygdala (AMG), and some parts of the striato-pallidal system, present high densities of oxytocin (OT)-binding sites. In order to examine whether these OT-binding sites are functional receptors, the OT neuronal sensitivity and the presence of OT-binding sites were investigated using electrophysiological and autoradiographical techniques. To identify the AMG cells, electrical stimulation of the oval subnucleus of the bed nucleus of the stria terminalis (Ov) and of the parabrachial nucleus (Pb) were performed. Somatic and auditory sensory stimulations were also tested. OT was applied by iontophoresis during extracellular single unit recordings of cells which were localized in frontal brain sections subsequently used for histoautoradiographic detection of OT-binding sites. Cells responding to Ov nucleus stimulation were located in the AMG, mainly in the Ce nucleus, whereas those responding to Pb nucleus stimulation were distributed in the Ce nucleus and in the postero lateral part of the caudate putamen. Iontophoretic OT application excited 45% of the recorded cells (43/96) among which OT alone activated spontaneous firing rate of 30 and potentiated the L-Glutamate (GLU)-induced activation on 13. These OT-sensitive neurons were located mainly in the AMG and caudate putamen areas containing OT-binding sites. These results strongly suggest that OT-binding sites found in the AMG are functional receptors upon which OT could act as a neurotransmitter and as a neuromodulator to regulate autonomic functions.