Perfusion (United Kingdom)

Cardiac surgery with cardiopulmonary bypass (CPB) is associated with the development of a systemic inflammatory response that can often lead to dysfunction of major organs. The systemic inflammation can be assessed intra- and postoperatively by measuring concentrations of inflammatory mediators in plasma and tissues. These concentrations, however, do not always correlate with the degree of observed organ dysfunction.

Various strategies have been used to reduce inflammatory phenomena in patients undergoing CPB. Cardiac surgery without CPB has been performed increasingly with satisfactory results over the past few years. Attenuation of systemic inflammation and improved outcome in high risk patients are potential benefits of this technique.

The emergence and expanding performance of cardiac surgical procedures without the use of CPB has given us an excellent tool to investigate the relative importance of CPB as a cause of systemic inflammation.

Aprotinin is a protease inhibitor which is used in cardiac surgical patients for its haemostatic effects. Aprotinin has anti-inflammatory properties, the nature of which have not been completely clarified.

This article presents a summary of the published literature investigating inflammatory response and organ dysfunction in patients who have cardiac surgery without CPB. It also presents an overview of recent data on the anti-inflammatory action mechanisms of aprotinin.

Background: The new concept of mini-extracorporeal circulation (MECC) for coronary artery bypass grafts (MCABG) consists of minimal priming volume, a heparin-coated closed circuit, a centrifugal pump, active drainage, blood cardioplegia and a cell-saving device. The potential organ protective effect of this technique during CABG is unknown. Initial clinical outcomes, oxidative stress, alveolar shunting and need for blood transfusion were investigated for MCABG patients. Subsets of these data were compared to outcomes of matched groups of patients operated conventionally (CCABG) and off-pump (OPCAB).

Methods: Data of 184 patients were gathered and analysed from a prospective observational database system. This database consists of the initial experience with the first 114 MCABG operations. Of these, the clinical outcome was investigated. In a subset of 60 MCABGs, need for transfusion was monitored and compared to 60 CCABGs. Serum concentrations of malondialdehyde (MDA), allantoin/urate ratios, shunt fractions and lung epithelium-specific proteins (CC16) were measured as biomarkers of damage during MCABG, CCABG and OPCAB (n-30).

Results: Patient groups were similar concerning age, risk and number of distal anastomoses. Clinical outcomes are shown for MCABGs only. During MCABG, need for trans-fusion was significantly reduced compared to CCABG (pB/0.001). Serum concentrations of MDA and allantoin/urate ratios showed significantly reduced oxidative stress during MCABG compared to CCABG. During MCABG, F-shunts were reduced shortly after surgery. Increased concentrations of pneumoprotein CC16 were measured during CCABG compared to MCABG (data submitted).

Conclusion: Short-term clinical outcomes of MCABG patients are satisfactory. Compared to CCABG the need for transfusion is significantly reduced when a MECC is used. Oxidative stress parameters show a tendency towards improved global organ protection compared to CCABG. F-shunt fractions and CC16 concentrations suggest reduced alveolar damage during MCABG. In a prospective study, the protective effect of mini-CABG has to be confirmed.

One challenge in providing extracorporeal circulation is to supply optimal flow while minimising adverse effects, such as haemolysis. To determine if the recent generation constrained vortex pumps with their inherent design improvements would lead to reduced red cell trauma, we undertook a study comparing three devices. Utilizing a simulated short-term ventricular assist circuit primed with whole human blood, we examined changes in plasma free haemoglobin values over a six-day period. The three pumps investigated were the Maquet Rotaflow, the Levitronix PediVAS and the Medos Deltastream DP3.This study demonstrated that all three pumps produced low levels of haemolysis and are suitable for use in a clinical environment. The Levitronix PediVAS was significantly less haemolytic than either the Rotaflow (p<0.05) or the DP3 (p<0.05). There was no significant difference in plasma free haemoglobin between the Rotaflow and the DP3 (p=0.71).

Cardioplegic arrest and cardiopulmonary bypass are key triggers of myocardial injury during aortic valve surgery. Cardioplegic ischaemic arrest is associated with disruption to metabolic and ionic homeostasis in cardiomyocytes. These changes predispose the heart to reperfusion injury caused by elevated intracellular reactive oxygen species and calcium. Cardiopulmonary bypass is associated with an inflammatory response that can generate systemic oxidative stress which, in turn, provokes further damage to the heart. Techniques of myocardial protection are routinely applied to all hearts, irrespective of their pathology, although different cardiomypathies respond differently to ischaemia and reperfusion injury. In particular, the efficacy of cardioprotective interventions used to protect the hypertrophic heart in patients with aortic valve disease remains controversial. This review will describe key cellular changes in hypertrophy, response to ischaemia and reperfusion and cardioplegic arrest and highlight the importance of optimising cardioprotective strategies to suit hypertrophic hearts.

This study was undertaken to develop a recovery model of cardiopulmonary bypass (CPB) in rats. Twenty male Wistar rats (475-550 g) were anaesthetized, mechanically ventilated and the femoral vessels cannulated. The extracorporeal circulation circuit comprised a roller pump, a venous reservoir and a modified Capiox 308 paediatric membrane oxygenator. Priming consisted of 20 ml of fresh homologous blood and 15 ml of colloid. Anticoagulation was achieved with heparin (500 IU/kg). Blood gas analysis, blood pressure monitoring and survival studies were performed in CPB ( n=10) and Sham ( n=10) rats.

Partial CPB was always easily established and was conducted at a flow rate of 100 ml/kg/min for 90 min. Blood gas analysis and blood pressure data did not differ between the two groups. All CPB rats survived and the 3-week follow-up period remained uneventful.

The rat model of CPB was easy to perform and was associated with excellent survival. This recovery model should allow us to study the pathophysiological processes underlying post-CPB multiple organ dysfunction.

Soluble endothelial adhesion molecule expression in clinical cardiopulmonary bypass (CPB) was investigated. Neutrophil-mediated endothelial injury plays an important role in CPB-induced organ dysfunction. The adhesion of neutrophil to the endothelium is central to this process. It has been well documented that CPB induces neutrophil activation and changes in neutrophil adhesion molecule expression, but the effect of CPB on endothelial cell activation is not known. This study was designed to measure soluble endothelial adhesion molecules during CPB.

We made serial measurements (by specific enzyme-linked immunoabsorbent assay) of plasma levels of the soluble endothelial adhesion molecules, ICAM-1 and E-selectin in patients undergoing routine CPB ( n =7) and in a control group (thoracotomy, n = 3).

The results show an initial significant decrease during CPB followed by an increase in plasma E-selectin from 29.3 ± 5.1 ng/ml (mean ± SEM) prebypass to 34.0 ± 5.4 ng/ml at 48 h postbypass. Likewise, plasma ICAM-1 significantly decreased during CPB and then increased from 246.3 ± 38.0 ng/ml before bypass to 324.8 ± 25.0 ng/ml and 355.0 ± 23.0 ng/ml at 24 and 48 h after bypass, respectively. The rise in levels is statistically significant ( p < 0.05).

This study shows a decrease in circulating ICAM-1 and soluble E-selectin during CPB and an increase in their levels at 48 h after CPB.

The aim of this study was to monitor and compare the changes in metabolism and blood flow in the skeletal muscles during cardiac operations performed with cardiopulmonary bypass (CPB) and operations without CPB (off-pump) by means of interstitial microdialysis (Figure 1). Surgical revascularization, coronary artery bypass grafting (CABG), was performed in 40 patients randomized to two groups. Twenty patients (On-Pump Group) were operated on using CPB, 20 patients (Off-Pump Group) were operated on without CPB. Interstitial microdialysis was performed by 2 probes of a CMA 60 (CMA Microdialysis AB, Solna, Sweden) inserted into the patient’s deltoid muscle. Microdialysis measurements were performed at 30-minute intervals. Glucose, lactate, pyruvate and glycerol as markers of basic metabolism and tissue perfusion were measured in samples from the first probe, using a CMA 600 Analyzer (CMA Microdialysis AB). Blood flow through the interstitium was monitored by means of dynamic microdialysis of ethanol as a flow-marker in the dialysates taken from the second probe (ethanol dilution technique). Results in both the groups were statistically processed and compared. Both the groups were similar in respect of preoperative characteristics. Dynamic changes of interstitial concentrations of the measured analytes were found in both the patient groups (on-pump vs. off-pump) during the operation. There was no significant difference in dialysate concentrations of glucose and lactate between the groups. Significant differences were detected in pyruvate and glycerol interstitial concentrations, lactate/pyruvate ratio and lactate/glucose ratio between the on-pump vs. off-pump patients. In the Off-Pump Group, pyruvate concentrations were higher and the values of concentrations of glycerol lower. The lactate/pyruvate ratio and the lactate/glucose ratio, indicating the aerobic and anaerobic tissue metabolism status, were lower in the Off-Pump Group. There was no significant difference in dialysate concentrations of ethanol as a flow-marker during the surgery in either of the groups. There was no statistically significant difference between the groups (On-Pump Group vs. Off-Pump Group) comparing the postoperative clinical outcome (ICU stay, ventilation duration, length of hospital stay). The dynamic changes in the interstitial concentrations of the glucose, glycerol, pyruvate and lactate were found in both the groups of patients (On-Pump Group and Off-Pump Group), but there was no difference in local blood flow when the ethanol dilution technique was used. These results showed significantly higher aerobic metabolic activity of the peripheral tissue of patients in the Off-Pump Group vs. the On-Pump Group during the course of cardiac revascularization surgery. Results suggest that extracorporeal circulation, cardiopulmonary bypass, compromises peripheral tissue (skeletal muscles) energy metabolism. These changes have no impact on the postoperative clinical outcome; no significant difference between the groups was found.