Perfusion

Introduction: Donor blood supplies are diminishing, becoming more costly and these transfusions lead to higher mortality in cardiac patients. The transfusion risks and the literature highlight the need for an alternative similar to cell salvage to be routinely considered. The Xtra is the first cell saver to be launched since 2001 and will undoubtedly initiate evolution towards the ‘next generation’ of cell savers. It is also the first to be launched in a new era where the demand for electronic perfusion data management (EPDM) has grown.

Results: The user interface (UI) was easy to use. The increased data entry options improved the quality of the recordable data. The integrated data management system (DMS) was comprehensive. Data was easy to manage and enabled central data compilation, which reduces repeated data, the risk of inconsistent data inventory and provides the potential for research and analyses. The haematocrit of the processed blood is a key quality indicator for cell salvage. The comparison of the manufacturer’s integrated protocol, Popt, to our team’s own protocol showed that Popt delivered a higher haematocrit on its ‘1st bowl’ (59.1% compared to 57.3%) and its ‘total process’ end product haematocrit was 0.68% higher. The Popt cycle took an average of 330s, whereas our own settings completed in just over 300s.

Conclusion: The Xtra is a device which will lead the evolution of ‘next generation’ cell saver technology. The user interface and data management system provide export options and the ability to record the level of data required for good EPDM. This is essential to ‘future proof’ cell salvage technology. The manufacturer’s integrated protocol achieved a higher end product haematocrit than our perfusion team’s best practice. The design of the Xtra is contemporary, but the DMS equips this cell saver for the new era that faces both Perfusion and Cardiac Surgery.

Objectives: Femoral artery cannulation is routinely used in circulatory support scenarios for cardiorespiratory support in patients with acute cardiac and/or pulmonary decompensation. During prolonged perfusion, this may cause acute ischemia of the leg and, in the worst case, even amputation. The aim of this experimental study was to test a newly designed arterial cannula allowing proximal and distal blood flow.

Methods: Veno-arterial cardiopulmonary bypass was established in three calves (67.6 ± 5.1 kg). The venous line was secured by cannulation of the external jugular vein. The arterial line of each animal was secured by cannulation of iliac arteries on both legs. On one side, we used a modified SmartCannula (SmartCannula 18Fr 130 mm) and, on the other side, a standard rectilinear BioMedicus cannula system was used, 19 Fr for retrograde and an 8 Fr BioMedicus shunt for anterograde flow toward the leg. An ultrasonic flow probe was used to quantify the perfusion of the distal leg.

Results: At 0.5, 1.0, 1.5, and 2.0 l/min, the anterograde leg blood flow increased steadily for each cannula, but remained higher in the self-expanding cannula. That is, the 8 F rectilinear cannula achieved a blood flow of 0.02 ± 0.01, 0.1 ± 0.04, 0.22 ± 0.09, and 0.21 ± 0.02 l/min, respectively, and the 18 F self-expanding cannula achieved 0.06 ± 0.02, 0.15 ± 0.03, 0.24 ± 0.07 and 0.36 ± 0.04 l/min.

Conclusion: The modified self-expanding cannula exhibited superior distal arterial flow compared to the routinely used rectilinear shunt system. This has a potential to reduce ischemic events of the inferior extremity in prolonged perfusion.

Objective: To construct an ideal extracorporeal life support (ECLS) circuit in terms of hemodynamic performance, each component of the circuit should be evaluated. Most cannulae manufacturers evaluate their products using water as the priming solution. We conducted this study to evaluate the different sizes of arterial and venous cannulae in a simulated neonatal ECLS circuit primed with human blood.

Methods: The simulated neonatal ECLS circuit was composed of a Capiox Baby RX05 oxygenator, a Rotaflow centrifugal pump and a heater & cooler unit. Three Medtronic Bio-Medicus arterial cannulae (8Fr, 10Fr, 12Fr) and three venous cannulae (10Fr, 12Fr, 14Fr) were tested in seven combinations (8A-10V, 8A-12V, 10A-10V, 10A-12V, 10A-14V, 12A-12V, 12A-14V). All the experiments were conducted using human blood at a hematocrit of 40% and at a constant temperature of 37°C. The “tip to tip” priming volume of the entire circuit was 135ml. The blood volume of the pseudo patient was 500ml.

Results: Flow rates increased linearly with increasing size in both venous and arterial cannulae at the same pump speeds. The increase in flow rate was greater when changing the arterial cannulae (next size larger) compared to changing the venous cannulae (next size larger). The pressure drops of the arterial cannula were correlated with the flow rates, regardless of the pseudo patient pressure and the venous cannula used simultaneously.

Conclusions: The results show the difference in flow ranges and pressure drops of seven combinations of arterial and venous cannulae. It also suggests that the arterial cannula, not the venous cannula, has greater impact on the flow rate when a centrifugal pump is used in a neonatal ECLS circuit. The results of this study have been translated to further advancing the clinical practice in our institution.

Extracorporeal assist systems for respiratory and circulatory failure are increasingly used in intensive care medicine. Important technical innovations over the past years have resulted in improved biocompatibility and, consequently, reduced complication rates. Extracorporeal membrane oxygenation (ECMO) technology experienced a surge of use during the influenza A (H1N1) pandemic, but transport of unstable patients with life-threatening ARDS is still hazardous. We describe the first successful application of a newly developed, compact and easily portable ECMO device in a patient with severe ARDS due to influenza A (H1N1). Support with the miniaturized ECMO resulted in immediate improvement of gas exchange and a highly protective ventilation. Inspiratory pressure was decreased from 40 to 29 cmH₂O and tidal volume per kilogram of predicted bodyweight could be reduced from 6.5 to 3.3 mL.

Small and efficient heart-lung assist systems will become a tool of growing importance in intensive care medicine, both for profound respiratory and cardiac failure in the future. The reduced weight and compact design of the device greatly facilitates transport and handling of unstable patients on ECMO.

Introduction: Non-invasive cerebral monitoring with the INVOS cerebral oximeter is an accepted good indicator of cerebral metabolism. In recent years, it has been used in the monitoring of patients who underwent cardiac surgery. Herein, we describe the INVOS trend during cardiopulmonary bypass (CPB) in a cohort of patients operated in our institution for congenital heart disease.

Patients and methods: Between December 2009 and March 2010, 40 patients (mean age 8.4 years; range 11 days-60 years) underwent cardiac surgical procedures using CPB. Values of INVOS cerebral parameter, pH, oxygen saturation, and CO₂ level were collected pre CPB, during cooling, re-warming and weaning, and post CPB. INVOS parameters were evaluated according to CPB priming, age and preoperative oxygen saturation.

Results: Patients were divided according to CPB priming (haematic vs clear), age (≤1 vs >1 year of age) and oxygen saturation (≤92% vs >92%). During the operations, the trend demonstrated a reduction in INVOS value at the institution of CPB and a further reduction during the cooling phase in all groups.This has been correlated to the loss of pulsatile flow. However, the value recovered during re-warming, weaning and CPB discontinuation. Cyanotic patients presented a lower cerebral oximetry compared to acyanotic patients during the whole CPB period. Between age and priming groups, we noticed a statistical difference in cerebral oximetry, with a lower value in the younger patients and in the haematic priming group. This might be interrelated because all patients younger than 1 year old always received haematic CPB priming. Conclusions: We demonstrated that cerebral oximetry decreases with the loss of pulsatile flow regardless of the mean arterial pressure and, furthermore, is not directly related to the haematocrit value in patients with reduced pulmonary blood flow.

Extracorporeal life support (ECLS) offers lifesaving mechanical circulatory support for patients afflicted with respiratory and/or cardiac failure. Neonatal respiratory patients have higher survival rates compared to pediatric patients, while, for cardiac cases, pediatric patients are more likely to survive. The indications for ECLS have been expanded due to the improved technology and favorable outcomes. However, the rate of mortality and morbidity for ECLS patients remains significant. Mechanical complications still comprise a large percentage of ECLS complications, leaving definite room for improvement in ECLS circuit technology in the future. As a pre-clinical evaluating tool, translational research will provide more useful information for the selection of ECLS devices, encourage further development of ECLS technology, and, ultimately, benefit the patients.

A 4.3 kg, three-month-old patient, diagnosed with a perimembranous ventricular septal defect, presented for cardiac surgery. Upon initiation of cardiopulmonary bypass (CPB), the patient developed carboxyhemoglobinemia (11.1%). Potential sources for the unexpected acquired carboxyhemoglobinemia were sought quickly. Testing of residual blood from the unit of packed red blood cells (PRBCs) used to prime the CPB circuit revealed a carboxyhemoglobin (COHb) of 15.1 %. A decrease in cerebral oximetry (rSO₂) on CPB was initially felt to be a result of the elevated COHb levels. When ventilation of the oxygenator with 100% oxygen (O₂) failed to decrease COHb levels, a partial exchange transfusion was performed with reduction in COHb to 7.1%. The operation was completed successfully and the patient’s COHb levels returned to normal within 75 minutes.

Post case analysis of events and data collected during the case revealed a broader differential for explaining the compromised patient’s O₂ delivery than the transient acquired carboxyhemoglobinemia. A partial obstruction of the superior vena cava could have triggered the drop in rSO₂ on CPB.

Follow-up of the donor blood confirmed the donor had previously undiagnosed carboxyhemoglobinemia as a result of chronic carbon monoxide exposure from a faulty vehicle exhaust system.

Introduction: The aim of the present study was to evaluate the clinical outcome of a normal stress technetium-99m (99mTc)-Sestamibi single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) with different probabilities of coronary artery disease (CAD).

Material and Methods: A total of 1,047 subjects with a normal 99mTc-MIBI SPECT were followed up for one year and hard and soft cardiac events were assessed. Hard cardiac events were defined as cardiac death or non-fatal myocardial infarction (MI). Soft cardiac events included the patient’s development of recurrent chest pain requiring coronary revascularization or significant stenosis in coronary arteries on angiography.

Results: Overall, 1,047 patients (248 men and 799 women; mean age: 60.07 ± 12.31, range 29—92) were enrolled. Three hard cardiac events occurred in the groups; two had cardiac arrest and one non-fatal MI. As a result, the annualized hard cardiac event rate was 0.28%, the annualized cardiac mortality rate was 0.19%, and the rate of overall annualized cardiac events was 1.25%. Furthermore, there was a significant difference in cardiac events among patients with various pretest likelihoods of CAD (p value=0.04).

Conclusion: Our data confirmed that patients with a normal 99mTc-Sestamibi myocardial SPECT are associated with a very low incidence of cardiovascular events.

The hypothesis was tested whether retrograde autologous priming (RAP) of the cardiopulmonary bypass system, compared to a standard primed system (NON-RAP group), results in less haemodilution and less transfusion of packed red blood cells. Retrospectively, data was collected from the medical charts of one hundred patients undergoing elective coronary artery bypass grafting using cardiopulmonary bypass. Fifty patients where RAP was used have been compared to fifty patients using NON-RAP. The prime volume in the NON-RAP group was 1,627±108 mL versus 782±96 mL in the RAP group (p<0.001). The lowest haematocrit during perfusion was 22% in the NON-RAP group versus 26% when the RAP technique was used (p<0.001). In the NON-RAP group, 26% of the patients received packed red cells in contrast to 6% in the RAP group (p<0.012). A positive association was found between RAP and less transfusion of packed red blood cells (p<0.012). In conclusion, retrograde autologous priming, reducing the prime volume of the cardiopulmonary bypass system, causes less haemodilution and reduces intraoperative transfusion of packed red blood cells.

Background: Blood for activated clotting time (ACT) measurement to verify the effect of the initial dose of heparin before cannulation in heart surgery has traditionally been drawn 5 minutes (min) after injection of the heparin. However, there has been an increasing demand to reduce the waiting time. The aim of this study was to investigate if ACT measured 1, 2, 3 and 4 min after heparin injection is as reliable as ACT measured 5 min after heparin injection.

Materials and methods: Fifty adult patients undergoing routine cardiac surgery with a heart-lung machine. Heparinization was obtained with unfractioned porcine heparin. The ACT was measured with 5 Hemochron® Jr. machines 1, 2, 3, 4 and 5 min after the heparin injection. Full heparinization was defined as an ACT >400 seconds.

Results: At 1 and 2 min, 94% (n=47) of the ACTs were > 400. All ACTs >400 seconds after 2 min remained >400 seconds at 3, 4 and 5 min. Mean values declined from 533 to 498. ANOVA analysis showed statistically significantly higher values at 1, 2 and 3 min, compared to 5 min, but not at 4 min. However, the estimated differences were small: 3.7-36 seconds. There was no significant difference between variances for the five sample times. Standard deviation declined from 123 to 100. Values at 2 min correlated as well as those at 5 min with mean 1-5 min values.

Conclusion: The range of the ACT values tends to diminish over time and, consequently, the reliability of the results increases. However, the difference is small and has little or no clinical relevance. Giving time for the circulation to distribute the heparin in the bloodstream, we recommend measuring the ACT two min after heparin administration.

During cardiopulmonary bypass (CPB), red blood cell transfusions may be required to correct dilutional anemia. The decision-making process for transfusions is usually based on the level of hemoglobin.This study investigates the hypothesis that oxygen-derived variables (mixed venous oxygen saturation, SvO₂, and oxygen extraction rate, O₂ER) may be more reliable predictors of the efficacy of the transfusion.

Thirty-six patients for 41 transfusion episodes during CPB were retrospectively analyzed. For each patient, oxygen-derived variables, including SvO₂ and O₂ER, were measured before and after the transfusion. No changes in pump flow were allowed between the two measurements. The efficacy of transfusion was defined as an increase in SvO₂ of at least 5%.

We identified 11 transfusion episodes leading to an efficacious SvO ₂ increase. Factors associated with the efficacy of the transfusion were a low SvO₂ and a high O₂ER. No association was found with hemoglobin values, unless for a trend for efficacy of transfusion in patients with very low (<6 g/dL) hemoglobin values. Cut-off values of 68% for SvO₂ and 39% for O₂ER were predictive for the efficacy of red blood cell transfusions, with a high accuracy (c-statistics 0.856 and 0.848, respectively) and negative and positive predictive values exceeding 82%. In conclusion, SvO₂ and O₂ER are better than the hemoglobin value for guiding the decision-making process of red blood cell transfusions to correct hemodilutional anemia during CPB.

Rotation thromboelastography (ROTEM) is a screening method that allows the rapid detection of plasma- and platelet-related haemostatic abnormalities. To use this procedure more efficiently, reference values depending on gender, age, and oral contraception are required. In this study, five cohorts of healthy subjects were examined by ROTEM upon activation of the extrinsic or intrinsic pathway of coagulation, or recalcification alone. The cohorts comprised male subjects below (1) and above (2) 45 years of age, female subjects below 45 years of age with (3) or without (4) oral contraception, and female subjects above 45 years (5) without hormone replacement therapy. A significant influence of gender, age, and oral contraception on parameters determined by ROTEM was observed. Thus, adjustment for age, gender, and oral contraception is required when ROTEM is used to screen for distinct abnormalities of haemostasis.

Central venous catheters are mandatory during every major procedure involving extracorporeal circulation. Air emboli potentially could enter the circulation through this device when negative pressure is applied in the venous cannula. The following experimental study was initiated by a fatal massive air embolus during a vascular procedure involving cardiopulmonary bypass. An experimental setup was established, simulating a real scenario. The experiment was performed with a 40% glycerol/water mixture which exhibits properties and fluid dynamics close to blood. A heart-lung machine provided circulation of the fluid. The flow was adjusted according to the gravitational status. A triple-lumen central venous catheter with one line open to air was lowered into the liquid. The disconnected lumen of the central venous catheter was manipulated so it approached and was located in close proximity to the venous cannula. An air flow of up to 300 ml/min could be obtained from the central venous catheter with a flow in the cardiopulmonary bypass circuit of 2.3 L/min. A linear relationship was observed between flow in the circuit and air flow. Consecutive measurements proved consistent with acceptable results, proving that a disconnected central venous catheter might, under certain circumstances, be a source of massive air emboli during cardiopulmonary bypass.

Persistent left superior vena cava (PLSVC) represents the most frequent congenital malformation of the thoracic venous drainage system. In adults referred to surgery for an acquired cardiac disease, abnormal venous drainage may be missed if not carefully researched. Discovering a previously undiagnosed PLSVC during cardiopulmonary bypass (CPB) may present some inconvenience for both the perfusionist and the surgeon, especially during a minimally invasive approach. The authors believe PLSVC probably may represent an under-reported condition. A careful screening of patients undergoing cardiac surgery may prove helpful. In particular, a complete echocardiographic study may help to better diagnose this condition before surgery.

Different signs may raise the suspicion of PLSVC and should be carefully researched during preoperative patient work-up.