Clinical Hemorheology and Microcirculation

Purpose: Microvascular perfusion, pivotal for adequate tissue oxygenation is potentially linked to outcome in critical care therapy. Mechanical ventilation (MV) and positive end-expiratory pressure (PEEP) as standard concepts of respiratory management are known to have deleterious effects on regional organ perfusion especially in the splanchnic area. As these effects have been attributed to different physiologic mechanisms, the purpose of this study was to investigate the effect of positive pressure ventilation on extra-abdominal tissue perfusion in non-surgical intensive care patients. Methods: Sublingual microcirculation was evaluated in 46 severely ill patients (group 1: n=26 requiring MV and PEEP; group 2: n=20 spontaneous breathing) admitted to the intensive care unit using sidestream darkfield intravitalmicroscopy. According to current guidelines, sublingual vessels were categorized by means of size and flow in semi-quantitative categories determining microvascular flow index (MFI). Total microvascular flow index (TMFI) was calculated for each patient as mean value of flow in all vessel categories. Results: No significant difference was observed between both groups in microvascular flow index in each vessel category and in total microvascular flow index. Patients requiring mechanical ventilation presented with more comorbidities and higher acuity of illness scores resulting in a higher ICU mortality, which however was not accompanied by microcirculatory differences at the time of measurement. Conclusion: Mechanical ventilation and PEEP have no general deleterious effects on microvascular perfusion of the sublingual mucosa. However, further clinical studies are required to investigate potential effects of higher levels of ventilation pressure or PEEP on microvascular perfusion.

Different bones have different blood supplies, which may influence bone healing. Therefore, elucidation of the mechanisms involved in the regulation of bone marrow blood flow in different bones is of high clinical importance. To assess the micro circulation of bone marrow of the femur and tibia simultaneously, flow velocities were continuously measured by a two-channel laser-Doppler flowmeter. The probes were introduced into the femoral and tibial diaphysis, respectively, in the anesthetized rabbit. Changes in micro circulation of the bone marrow were elicited by intra-arterial bolus injections of vasoactive substances: epinephrine (E), calcitonine-gene related peptide (CGRP), substance P (SP), sodium nitroprusside (SNP), E and Ebrantil. Systemic arterial blood pressure was recorded with an electro-manometer. Micro vascular resistance (MVR) and 50% recovery time (50RT) to baseline flow level were calculated from the measured data. Flow velocity in the femur was significantly higher. Epinephrine considerably reduced micro vascular blood flow, which could be significantly warded off by Ebrantil. CGRP and SP did not change MVR. Application of SNP resulted in reduction of flow velocity, but it also decreased MVR. No statistically significant differences were found between reactions of the micro circulation in the two marrows. These results suggest that there are no significant differences between the blood flow response patterns of these two bone marrow sites, thus the regulation patterns of the micro circulation of the two bones are also similar.

We report discordant imaging findings of a small persistent type II endoleak in a 72-year-old man who had undergone endovascular aneurysm repair (EVAR) of an abdominal aortic aneurysm. Although the aneurysm was growing in size digital subtraction angiography could not detect an endoleak, but time-resolved CT-angiography and contrast enhanced ultrasound did detect a small type II endoleak.

There is little information regarding the behaviour of red blood cell deformability in macrocytosis. We have determined in 114 patients with macrocytosis (MCV > 97 fL) and in 115 age and sex-matched subjects with normocytosis (VCM < 97 fL) erythrocyte deformability by means of ektacytometric techniques (Rheodyn SSD) measuring the erythrocyte elongation index (EEI) at 12, 30 and 60 Pa. Patients with macrocytosis showed statistically higher EEI at all the shear stresses tested when compared with controls (p < 0.001). When patients with macrocytosis were classified according to their main diagnosis as hepatic or renal disease, HIV and miscellaneous, 66.7%, 41.7%, 36.7% and 33.3% of patients, respectively, showed a EEI 60 higher than 61.8% (mean value of the control group + 2 SD). Linear regression analysis demonstrates that MCV, bilirubin, triglycerides and alanine aminotransferase were the main variables influencing EEI 60. An increased surface/volume ratio of the red blood cells may be the main cause related with a higher erythrocyte deformability in a relevant percentage of macrocytosis. Further research is required to confirm our findings by designing case-control pathology-specific studies.

We examined the thiobarbituric acid-reactive substances (TBARS) as an index of lipid peroxidation, and the total antioxidant status (TAS) in 81 unprofessional athletes subdivided into three subgroups. The first group included 28 subjects who practised endurance sports, the second included 30 subjects who practised mixed sports, the third included 23 subjects who practised power sports. We enrolled also a group of 61 sedentary controls (SC). TBARS were increased and TAS was decreased in the whole group of athletes in comparison with SC; an almost similar behaviour was present also subdividing athletes according to the practised sport. A significant negative correlation between these two parameters emerged in SC but not in the whole group of athletes. Unless for the athletes that practised endurance sports a similar trend was found in athletes that practised mixed and power sports. In conclusion, at rest the symmetrical behaviour between the lipid peroxidation increase and the TAS decrease, observed in sedentary controls, was not evident in unprofessional athletes who practised different sports.

The present study investigated the hemorheological and endothelial alterations in sickle cell trait (SCT) carriers in response to a submaximal exercise. Eleven SCT carriers and 11 subjects with normal hemoglobin performed submaximal exercise for 15 min. Blood was sampled at rest, at the end of exercise, and at 2 and 24 h of recovery. Hemorheological alterations observed in the SCT group were as follows: 1) lower RBC deformability at high shear stress at all time-points, with no relation to oxidative stress, 2) higher disaggregation threshold at all time-points, suggesting RBC hyper-aggregation, and 3) higher blood viscosity at the end of exercise and during recovery. Exercise had a specific influence on the levels of the soluble cell adhesion molecules P and L-selectin in the SCT carriers, with higher P-selectin levels at all time-points and a greater increase in L-selectin levels during recovery. SCT carriers had slightly decreased nitrite levels at 24h of recovery, which might be clinically insignificant. In conclusion, the hemorheological alterations in association with lower NO production found in the SCT carriers are probably not sufficient to explain the medical complications sometimes reported in SCT carriers after exercise.

In the present study, the role of the nucleus and its contribution to the deformability of the passive neutrophils was investigated. To determine the rheological properties of the nucleus and of the neutrophil itself, deformation tests on single neutrophil and sequestered nucleus have been performed by micropipette under low aspiration pressure (80 Pa = 2–3 P_cr). The stiffness of the nucleus was found to be larger than that of the neutrophil, and its viscosity was found almost ten-fold higher. A subpopulation of neutrophils (Sub-A) showed two phases of deformation, a first rapid phase and a second phase with a constant deformation rate up to their full entrance, with an apparent viscosity μ_{app-second-Phase}(N_Sub-A) = 286 ± 123 Pa·s, calculated by the liquid drop model. Another subpopulation (Sub-B) of the tested neutrophils displayed three deformation phases: a first one reflecting the rapid entry of cell into the micropipette, a second with constant deformation rate, and a third phase, with a slower, also constant, deformation rate were recorded. The corresponding apparent viscosities were found as μ_{app-second-Phase}(N_Sub-B) = 341 ± 94 Pa·s and μ_{app-third-Phase}(N_Sub-B) = 1651 ± 734 Pa·s. The apparent viscosity values of the neutrophilic nucleus, μ_app (N_nucl) = 2468 ± 1345 Pa·s and of the whole neutrophil calculated in the third phase of deformation, μ_{app-third-Phase}(N_Sub-B) = 1651 ± 734 Pa·s were comparable. These results support our hypothesis that the nucleus plays a significant role in the mechanical and rheological behavior of the neutrophil, especially when it has to pass through openings much smaller than its size.

Patients with hypertension have evidence of platelet activation. Mean platelet volume (MPV), an indicator of platelet activation has been shown to be elevated in patients with hypertension. Prehypertension is also associated with an increase in cardiovascular morbidity and mortality. The aim of this study was to assess the MPV in patients with prehypertension and hypertension. This study included newly diagnosed and untreated 87 prehypertensive patients, 30 hypertensive patients and 35 normotensive control subjects matched for age, gender, and body mass index. All patients and controls gave informed consent. The MPV values of patients with prehypertension and hypertension were significantly higher than those of the control group (8.4 ± 0.8 and 8.8 ± 0.7 versus 7.9 ± 0.5 fl; p < 0.05 and p < 0.001 respectively). It was also higher in hypertensives than in prehypertensives (8.8 ± 0.7 versus 8.4 ± 0.8 fl; p < 0.05). However, we found that the presence of the hypertension (β = 0.28, P = 0.003) was only significant predictors of higher MPV in a multivariable model that adjusted for other variables. We have shown that, MPV, an indicator of platelet activation was significantly higher in patients with prehypertension and hypertension when compared with control subjects. We have also showed that MPV was also higher in patients with hypertension than in patients with prehypertension. However, presence of the hypertension was only significant predictor of higher MPV.