Association between arrhythmias and reduced red cell deformability following cardiopulmonary bypass

Red Cell Distribution Width and Risk of Atrial Fibrillation and Subsequent Thromboembolism: The Tromsø Study

Introduction  Red cell distribution width (RDW) is associated with cardiovascular diseases, including atrial fibrillation (AF) and venous thromboembolism (VTE). Whether RDW is a risk marker for thromboembolic events in AF patients is scarcely known. We aimed to assess the association between RDW and the risk of AF, and AF-related VTE and ischemic stroke, in a population-based cohort.

Methods  We measured RDW in 26,111 participants from the Tromsø Study (1994–1995), and registered incident AF cases through December 31, 2013. Among participants with AF, first-ever VTEs and ischemic strokes were registered from the date of AF diagnosis through the end of follow-up. We calculated hazard ratios (HRs) with 95% confidence intervals (CIs) for AF by quartiles of RDW. Furthermore, we calculated cause-specific HRs for VTE and ischemic stroke by tertiles of RDW for participants with AF.

Results  There were 2,081 incident AF cases during a median of 18.8 years of follow-up. Subjects with RDW in the highest quartile (RDW ≥ 13.3%) had 30% higher risk of AF than those in the lowest quartile (RDW ≤ 12.3%). Among those with AF, subjects with RDW in the upper tertile had a doubled risk of ischemic stroke (HR 2.07, 95% CI 1.20–3.57). In contrast, RDW was not associated with incident VTE in subjects with AF.

Conclusion  RDW was significantly associated with incident AF in a general population. Among subjects with AF, high RDW was associated with ischemic stroke, but not VTE.

Red blood cell distribution width: A marker of anisocytosis potentially associated with atrial fibrillation

The incorporation of biomarkers in the actually used risk scores seem to be helpful for early identifying atrial fibrillation (AF) patients at higher risk. The aim of this critical review of the scientific literature is to investigate the potential clinical significance of red blood cell distribution width (RDW) in AF. A systematic electronic search was carried out to identify all articles describing an epidemiological association between RDW and AF in adult human populations. Data abstraction was conducted on a final number of 35 articles (13 cross-sectional, 12 prospective and 10 retrospective studies). The results of these epidemiological investigations were all virtually concordant to emphasize that an enhanced RDW value is not only a predictive factor and a marker of AF but its measurement may also be helpful for predicting the risk of developing many adverse complications in patients with AF, such as recurrence and duration of AF, hospitalization for heart failure, bleeding, left atrial thrombosis and stasis, thromboembolic events and mortality. AF patients with RDW values exceeding the local reference range may be more aggressively investigated and managed, in order to identify and attenuate the impact of possible underlying disorders causing both anisocytosis and AF.

Influence of Pathologic Blood Cell Microrheology on Myocardial Microcirculation in Cardiac Surgery Using Cardiopulmonary Bypass

A possible link between blood trauma and the myocardial microcirculation was prospectively studied in 27 patients undergoing cardiac surgery. Blood trauma was assessed microrheologically by analysis of gross red cell filtration rate (RFR) and plasma white cell filtration rate (p-WFR). Laser Doppler flow metry (LDF) was used to assess microflow in the myocardium before and after coronary bypass grafting.

The LDF% was significantly reduced in the ischemic parts of the myocar dium, by 25% compared with 52% in the nonischemic myocardium (p < 0.01). After grafting, the grafted ischemic myocardium increased the LDF to 55% (p < 0.001) to levels comparable to those of the nonischemic myocardium, but the normal nonischemic, nongrafted myocardium reduced its microflow to 42% (p < 0.02). The RFR taken simultaneously showed a significant reduction by 34% from 45 to 30μL/sec (p < 0.001). The p-WFR fell significantly by 39% from 33 to 20 μL/sec (p < 0.05). The type of operation did not significantly influence the RFR and p-WFR values. There was a positive correlation between the LDF and RFR (r=0.86, p < 0.01) and between LDF and p-WFR (r=0.77, p < 0.01).

Surgery with cardiopulmonary bypass (CPB) reduces the microcirculation in the myocardium. The rheology of blood cells is reduced during CPB. Studies to preserve the blood cells and the microcirculation during and after CPB are required.

Reduced White Blood Cell Microrheology and Postoperative Complications Associated with Cardiopulmonary Bypass

The effect of cardiopulmonary bypass (CPB) trauma and damage to the white blood cells (WBC) was prospectively studied in relation to myocardial microcirculation and postoperative complications in 45 patients undergoing cor onary bypass operations for angina pectoris. The filtrability of a suspension of white cells in plasma (P-WFR) was analyzed during CPB and in the first week following coronary bypass operations for angina pectoris. The damage to white cells due to CPB reduced filtrability by about 40% (p < 0.05) and a reduced filtrability was noted even one week after successful surgery. In 25 patients the microflow in the myocardium was semiquantitatively assessed intraoperatively by laser Doppler flowmetry (LDF%), and there was a positive correlation be tween P-WFR and LDF% (r=0.84, p < 0.01). The most common complication requiring treatment was cardiac arrhythmias (atrial fibrillation or flutter 12/45, 27%). Myocardial infarction, 9%; A-V blocks, 4%; respiratory insuffi ciency, 4%; cerebrovascular accident, 2%, and infections, 4% were also noted. The trauma to the WBC during CPB appears to reduce myocardial microflow and could be a factor in triggering postoperative complications. Studies to pro tect the WBC or remove damaged WBC during and even after CPB would appear to be warranted.

Red Cell Deformability Changes as a Prognostic Indicator of Postoperative Morbidity in Cardiac Surgery Using Cariopulmonary Bypass

Preoperative and intraoperative red cell deformability assessed by a standard microfiltration technique was used to study the gross rheologic changes of red cells due to disease and mechanical trauma in relation to postoperative compli cations following the use of cardiopulmonary bypass (CPB) for elective heart surgery in 142 patients in NYHA (New York Heart Association) class III. The red cell filtration rate (RCFR) in μL/s was determined before surgery and grouped rheologically into four functional classes (GTCA = Gothenborg Cardio-Thoracic Association). Compared with their laboratory's normal reference for 200 healthy individuals (mainly blood donors) (61 ± 9 μL/s ± 2 SD), the RCFR was signifi cantly reduced by 21% (p < 0.05) to GCTA class I (1-25% reduction) in 18 pa tients, by 34% (p<0.01) to class II (26-50% reduction) in 99, and by 54% (p<0.001) to class III (51-75% reduction) in 25. Significant RCFR reductions during CPB were seen in all the groups, where the mean reduction was lowest in class I (15% p<0.001) and highest in class III (76% p<0.001) as compared with normal subjects.

The analyses of complications showed that significantly higher frequencies of bleeding, blood transfusion, respirator usage, and arrhythmia were found in class III than in class I (1.5 vs 0.8 L, p<0.05; 3 vs 1.5 units, p < 0.05; 14 vs 6 hours, p<0.05 respectively).

The authors conclude that preoperative red blood cell deformability testing and grading of the patients' microrheologic status of red blood cells can be a complement to the NYHA function classification and can also be useful for study ing the morbid effects of surgical trauma associated with CPB.

Red blood cell damage during experimental prolonged perfusion with membrane oxygenation using fresh human blood

The effects of prolonged perfusion of oxygenated blood have previously been studied with respect to haemolysis and cell morphology. The aim of this study was to examine the effect of mechanical trauma on the microrheology of red blood cells during experimental prolonged perfusion with membrane oxygenation (PPMO). Red blood cell damage was assessed by blood rheological parameters using a St George's filtrometer. Red blood cell filtration rate (RFR, μl/s), clogging rate (RBC-CR, 102%/ml), clogging particle (RBC-CP, 106/ml), mean corpuscular volume (MCV) and haematocrit (Hct) were analysed at the start of PPMO and after 24, 48 and 72 hours. RFR values were 81.3 ± 3.7 at the start, 79.2 ± 7.6 (24 h, p < 0.01), 42.3 ± 8.4 (48 h, p < 0.001) and 25.1 ± 7.0 (72 h, p < 0.001). The mean RBC-CR was 2.45 ± 0.53 at the start; this increased to 3.58 ± 0.9, 6.62 ± 0.92 and then reduced to 4.77 ± 1.39 at 24 (p < 0.0001), 48 (p < 0.0001) and 72 (p < 0.02) hours respectively. Mean RBC-CP at the start was 3.29 ± 0.55; this increased to 3.42 ± 0.72, 5.29 ± 0.68 and 6.09 ± 1.07 at 24, 48 and 72 hours respectively (NS at 24 h and 48 h, p < 0.04 at 72 h). The mean MCV (fl) at the start was 86 ± 4; this increased to 101 ± 2, 111 ± 4 and 119 ± 4 at 24, 48 and 72 hours respectively (p < 0.001). Mean Hct (%) at the start was 33 ± 2; this increased to 38 ± 2, 38 ± 2 and 48 ± 2 at 24, 48 and 72 hours respectively (p < 0.05 at 24 and 48 hours, p < 0.001 at 72 hours). The mean pH and CO 2 (kPa.s) levels were 7.38 ± 0.04 and 4.1 ± 0.7 respectively. This study suggested that there was a continuous loss of red cell rheology during PPMO, which could lead to disturbed microcirculation, thereby increasing the risk of organ ischaemia, hypoxia, dysfunction and failure.

Effects of Alprostadil (synthetic prostaglandin E1) on red and white cell filterability during cardiopulmonary bypass

Reduced blood cell rheology due to mechanical blood trauma is associated with reduced microcirculation and organ dysfunction during and following cardiac surgery using cardiopulmonary bypass (CPB). The influence of prostaglandin E1 (PGE1) on the blood cell rheology was studied in 24 patients undergoing coronary artery bypass grafting surgery with the use of CPB. Intra-operative infusion of PGE1 was given to 12 patients in a dose of 20ng/kg/min; the other 12 patients served as controls. Red and white cell rheology were measured by red and white cell filtration rate (RFR and WFR) respectively, applying a standard bulk filtration technique. Blood samples were collected pre-operatively, at the start of CPB, after 30 minutes, 60 minutes, 90 minutes and at the end of CPB. Results showed that the mechanical trauma of CPB was better tolerated in the PGE1 group, where RFR and WFR showed significant lower losses during CPB (p < 0.001, p < 0.001). These results indicate that PGE1 has beneficial effects on red and white cell deformability during CPB. The improvement of blood rheology would be expected to lead to better microcirculation in the vital organs.

The inflammatory response and extracorporeal circulation

Defining the cause of organ and tissue dysfunction associated with the use of perfusion systems will produce methods of prevention or treatment and improve patient outcome. The problem is the plethora of triggers, effectors, and mediators in this process, which can now be measured. Each new measureable compound becomes another biochemical "smoking gun" without physiological data to show any relevance to the human problem. This review critically compares and contrasts the role of certain, largely novel, initiation, amplification, and cytotoxic mechanisms in the inflammatory response of the myocardium and pulmonary systems after a period of cardiopulmonary bypass. The available evidence strongly points to the process being different for each of these tissue beds. These data suggest that ensuring normal lung and heart functions after surgery will require separate therapeutic strategies.

A mathematical analysis of haemorheologic factors during cardiopulmonary bypass for congenital heart disease

Rheologic properties of blood are impaired by cardiac surgery using cardiopulmonary bypass. This study was set out to establish a mathematical model in order to assess seven known haemorheologic factors and evaluate their degrees of influence on blood rheology in cardiopulmonary bypass. Sixteen patients undergoing elective congenital cardiac surgery were studied. High shear blood viscosity, low shear blood viscosity, haematocrit, red blood cell filtration rate, red blood cell electrophoresis time, plasma viscosity and fibrinogen were monitored. The method for mathematical calculation was the stepwise regression analysis. The results showed that both high shear and low shear blood viscosity were mainly influenced by haematocrit and plasma viscosity. Red blood cell filterability contributed more than red blood cell electrophoresis time for low shear blood viscosity. The mathematical model was re-tested statistically and demonstrated that the selected factors in the model represented approximately 75% of rheologic changes during the surgery. Therefore, this mathematical analysis can be used to estimate the role of various possible haemorheologic factors and evaluate cardiopulmonary bypass techniques and therapeutic interventions.

The effects of propofol compared to high-dose fentanyl anesthesia on rheologic parameters in coronary artery surgery

Propofol has previously been found to decrease hematocrit values. Because hematocrit is an important determinant of blood viscosity, lower hematocrits may cause a decrease in blood viscosity, improving blood flow and oxygen delivery. This phenomenon may be beneficial in certain intraoperative situations. To study the influence of two anesthetic techniques on a variety of rheologic parameters, 32 patients scheduled for coronary artery bypass grafting (CABG) were divided into two groups. Group I (n = 18) was induced with high-dose fentanyl anesthesia (100 micrograms/kg), and group II (n = 16) with a combination of propofol and fentanyl anesthesia (1 to 1.5 mg/kg and 35 to 50 micrograms/kg, respectively). Maintenance anesthesia continued with infusions of the same drugs. Blood and plasma viscosity, hematocrit, erythrocyte aggregation factor, and erythrocyte deformability were measured preoperatively, intraoperatively, and up to 48 hours postoperatively. Whole blood viscosity was corrected to a standard hematocrit of 0.45. The two groups were comparable with respect to age, bypass duration, blood loss, urine output, transfusions, and fluid management. Erythrocyte deformability did not decrease during or after cardiopulmonary bypass (CPB). In both groups, hematocrit and blood and plasma were decreased significantly during and after CPB (P < 0.01) and returned to baseline levels 48 hours after surgery. After induction and before CPB, blood viscosity was only decreased in group II. However, the corrected blood viscosity was significantly elevated at all shear rates in group II compared to group I at 24 and 48 hours postoperatively (P < 0.01). In group II at these sampling times, this parameter was also significantly elevated compared to preoperative values.(ABSTRACT TRUNCATED AT 250 WORDS)

The clinical importance of erythrocyte deformability, a hemorrheological parameter

Hemorheology, the science of the flow behavior of blood, has become increasingly important in clinical situations. The rheology of blood is dependent on its viscosity, which in turn is influenced by plasma viscosity, hematocrit, erythrocyte aggregation, and erythrocyte deformability. In recent years it has become apparent that the shape and elasticity of erythrocytes may be important in explaining the etiology of certain pathological situations. Thus, clinicians have become increasingly interested in hemorheology in general and erythrocyte deformability in particular. In the course of time, many clinical studies have been performed, but no concise review has thus far been published. This article encompasses a review of the clinically based literature on this subject.

Acute embolic lower limb ischaemia is associated with decreased red cell deformability

Red cell deformability is an important determinant of peripheral blood flow. In this study the red cell filtration rate (RFR) was measured in 17 patients admitted for acute embolic lower limb ischaemia. The severity of the limb ischaemia on admission was scored from 0 to 6 depending on the degree of pain, and loss of motor and sensibility functions in the ischaemic extremity. Patients who presented with very severe ischaemia on admission underwent early embolectomy whereas those with less severe ischaemia (range from 0 to approximately 3 in ischaemic score) initially were treated conservatively with heparin. Red cell filtration rate was assessed with a standard microfiltration method and expressed in microliters/sec. On admission the RFR averages 30 +/- 5 microliters/sec (mean +/- S.D.), significantly lower than the corresponding value in a normal population of similar age (50 +/- 5 microliters/sec). There was an inverse relationship (r = 0.74, P less than 0.001 by use of linear regression analysis) between the ischaemic score and the RFR on admission, with low RFR values being related to high ischaemic scores. Forty-eight hours after revascularisation, the RFR had improved significantly in the patients having undergone successful revascularisation, whereas it was unchanged in conservatively treated patients. It is concluded that patients with acute embolic lower limb ischaemia have an impaired red cell filtration rate suggesting decreased red cell deformability, the impairment being related to the severity of the ischaemia. A poor red cell filtration rate on admission is related to increased risk of postoperative gangrene and/or cardiac death. Successful revascularisation, but not conservative heparin treatment is associated with increasing deformability.