Effect of Nitric Oxide via Cardiopulmonary Bypass on Ventilator-Free Days in Young Children Undergoing Congenital Heart Disease Surgery: The NITRIC Randomized Clinical Trial

IMPORTANCE

In children undergoing heart surgery, nitric oxide administered into the gas flow of the cardiopulmonary bypass oxygenator may reduce postoperative low cardiac output syndrome, leading to improved recovery and shorter duration of respiratory support. It remains uncertain whether nitric oxide administered into the cardiopulmonary bypass oxygenator improves ventilator-free days (days alive and free from mechanical ventilation).

OBJECTIVE

To determine the effect of nitric oxide applied into the cardiopulmonary bypass oxygenator vs standard care on ventilator-free days in children undergoing surgery for congenital heart disease.

DESIGN, SETTING, AND PARTICIPANTS

Double-blind, multicenter, randomized clinical trial in 6 pediatric cardiac surgical centers in Australia, New Zealand, and the Netherlands. A total of 1371 children younger than 2 years undergoing congenital heart surgery were randomized between July 2017 and April 2021, with 28-day follow-up of the last participant completed on May 24, 2021.

INTERVENTIONS

Patients were assigned to receive nitric oxide at 20 ppm delivered into the cardiopulmonary bypass oxygenator (n = 679) or standard care cardiopulmonary bypass without nitric oxide (n = 685).

MAIN OUTCOMES AND MEASURES

The primary end point was the number of ventilator-free days from commencement of bypass until day 28. There were 4 secondary end points including a composite of low cardiac output syndrome, extracorporeal life support, or death; length of stay in the intensive care unit; length of stay in the hospital; and postoperative troponin levels.

RESULTS

Among 1371 patients who were randomized (mean [SD] age, 21.2 [23.5] weeks; 587 girls [42.8%]), 1364 (99.5%) completed the trial. The number of ventilator-free days did not differ significantly between the nitric oxide and standard care groups, with a median of 26.6 days (IQR, 24.4 to 27.4) vs 26.4 days (IQR, 24.0 to 27.2), respectively, for an absolute difference of -0.01 days (95% CI, -0.25 to 0.22; P = .92). A total of 22.5% of the nitric oxide group and 20.9% of the standard care group developed low cardiac output syndrome within 48 hours, needed extracorporeal support within 48 hours, or died by day 28, for an adjusted odds ratio of 1.12 (95% CI, 0.85 to 1.47). Other secondary outcomes were not significantly different between the groups.

CONCLUSIONS AND RELEVANCE

In children younger than 2 years undergoing cardiopulmonary bypass surgery for congenital heart disease, the use of nitric oxide via cardiopulmonary bypass did not significantly affect the number of ventilator-free days. These findings do not support the use of nitric oxide delivered into the cardiopulmonary bypass oxygenator during heart surgery.

TRIAL REGISTRATION

anzctr.org.au Identifier: ACTRN12617000821392.

Direct true lumen cannulation in type A acute aortic dissection: A review of an 11 years' experience

Objectives

Direct true lumen cannulation (DTLC) of the aorta is an alternative cardiopulmonary bypass cannulation technique in the context of type A acute aortic dissection (A-AAD). DTLC has been reported to be effective in restoring adequate perfusion to jeopardized organs. This study reports and compares operative outcomes with DTLC or alternative cannulation techniques in a large cohort of patients with A-AAD.

Methods

All patients who underwent surgery for A-AAD between January 2006 and January 2017 in Mainz university hospital were reviewed. The choice of cannulation technique was left to the operating surgeon, however DTLC was our preference in patients who were in state of shock or showed signs of tamponade or hypoperfusion, in cases of potential cerebral malperfusion, as well as in patients who were under resuscitation.

Results

A total of 528 patients (63% males, mean age 64±13.8 years) underwent emergency surgery for A-AAD. The DTLC technique was used in 52.4% of patients. The DTLC group of patients had worse clinical status at the time of presentation with more shock, tamponade, true lumen collapse, cerebral and other malperfusion states. New neurologic events were diagnosed in around 8% of patients in each group following surgery, but there was a trend for quicker neurological recovery in the DTLC-group. Early mortality rates, short-term and long-term survival rates did not differ between the two groups.

Conclusions

DTLC is a safe cannulation technique that enables effective antegrade true lumen perfusion in complicated A-AAD scenarios, and is an advantageous addition to the aortic surgeons’ armamentarium.

Development and accuracy evaluation of a degree of occlusion visualization system for roller pumps used in cardiopulmonary bypass

In roller pumps used for cardiopulmonary bypass (CPB), the degree of blockage within the tube resulting from compression of the tube by the rollers, or the degree of occlusion, is closely related to hemolysis, with both tight occlusive and non-occlusive degrees promoting hemolysis. There are as yet no international standards regarding methods of adjusting occlusiveness, and the amount of mechanical stress exerted upon blood remains unknown. To prevent hemolysis during CPB using roller pumps, there is a need to clarify and quantitatively assess the mechanical stress of the occlusiveness of the roller pump. In this study, we have developed a degree of occlusion quantification system which constructs the flow channel shape within an occluded tube from red optical density images, and we have verified the validity of this system. Utilizing a linear actuator, an acrylic roller and raceway, a solution colored with simulated blood powder, and a 3/8-inch vinyl chloride tube, this system uses a camera to capture red optical density images within an occluded tube and constructs the tube flow channel shape using a formula manipulation system. To verify the accuracy of this system, we compared the thickness of a cross-section of the flow channel constructed with the degree of occlusion quantification system with the thickness of a cross-section of silicone cured under the same occlusion conditions. Our experiments indicated that for areas with a small tube gap, this system can construct highly accurate three-dimensional shapes and obtain quantitative indicators assessing the degree of occlusion.

Cardiopulmonary bypass and internal thoracic artery: Can roller or centrifugal pumps change vascular reactivity of the graft? The IPITA study: A randomized controlled clinical trial

Background

Cardiopulmonary bypass (CPB) induces a systemic inflammatory response (SIRS) and affects the organ vascular bed. Experimentally, the lack of pulsatility alters myogenic tone of resistance arteries and increases the parietal inflammatory response. The purpose of this study was to compare the vascular reactivity of the internal thoracic arteries (ITAs) due to the inflammatory response between patients undergoing coronary artery bypass grafting (CABG) under CPB with a roller pump or with a centrifugal pump.

Methods

Eighty elective male patients undergoing CABG were selected using one or two internal thoracic arteries under CPB with a roller pump (RP group) or centrifugal pump (CFP group). ITA samples were collected before starting CPB (Time 1) and before the last coronary anastomosis during aortic cross clamping (Time 2). The primary endpoint was the endothelium-dependent relaxation of ITAs investigated using wire-myography. The secondary endpoint was the parietal inflammatory response of arteries defined by the measurements of superoxide levels, leukocytes and lymphocytes rate and gene expression of inflammatory proteins using. Terminal complement complex activation (SC5b-9) and neutrophil activation (elastase) analysis were performed on arterial blood at the same times.

Results

Exposure time of ITAs to the pump flow was respectively 43.3 minutes in the RP group and 45.7 minutes in the CFP group. Acetylcholine-dependent relaxation was conserved in the two groups whatever the time. Gene expression of C3 and C4a in the artery wall decreased from Time 1 to Time 2. No oxidative stress was observed in the graft. There was no difference between the groups concerning the leukocytes and lymphocytes rate. SC5b-9 and elastase increased between Time 1 and Time 2.

Conclusion

Endothelium-dependent relaxation of the internal thoracic arteries was preserved during CPB whatever the type of pump used. The inflammatory response observed in the blood was not found in the graft wall within this time frame.

Trial registration

Name of trial study protocol: IPITA

Registration number (ClinicalTrials.gov): NCT04168853.

Efficiency of Minimized Circuits of a Heart Roller Pump on Systemic Inflammatory Response Syndrome and Multiorgan Effects in a Rat Model

BACKGROUND

The aim of this study is to compare the effects of tubing length on systemic inflammatory response syndrome and myocardial protection in a rat model of cardiopulmonary bypass (CPB) from a histological standpoint.

METHODS

Twelve adult male Wistar Albino rats weighing >180 g were randomly selected and divided into 2 groups. In 1 group, the pump lines were kept 1 m shorter than standard. The right jugular vein and tail artery were cannulated using a 16-gauge catheter. Animals received 500 IU/kg intravenous heparin. Cardiac index and rectal temperature were set at 2.4 mL and 36°C, respectively. Total line volume was maintained at 8 mL. A roller pump was adjusted to supply a blood flow of 6 to 28 mL/min (mean 10 mL/min), similar to the typical cardiac output of rats. CPB duration was 15 minutes throughout the experiment. After sacrifice, tissue samples were collected from heart, liver, and kidney for histomorphologic examination.

RESULTS

All histochemical and histomorphologic analyses, performed by 2 blinded researchers, revealed band loss in cardiomyocytes, mononuclear (MNL) cell infiltration, and impaired fibrillar organization in the standard-line group. Additionally in that group, sinusoidal dilatation in the liver, low-level congestion, focal necrosis, and periportal MNL infiltration were noted. In the shorter-line group, on the other hand, MNL cell infiltration, band loss in myofibrils, and cardiomyocyte degeneration were rarely observed. Higher liver congestion and lower MNL cell infiltration were observed in the shorter-line group. No significant differences were found in kidney samples.

CONCLUSION

In a shorter-line roller pump test model, less multiorgan damage and fewer systemic inflammatory responses were observed. It may be applicable to keep CPB lines as close to the table as possible, especially in pediatric cardiac surgery cases.

Benefits of Continuous Monitoring of PCO2 Obtained from a System Applied to Membrane Oxygenator Exhaustion of the Cardiopulmonary Bypass Circuit

OBJECTIVE

To observe the impact of the use of capnography system adapted to cardiopulmonary bypass (CPB). To measure the concordance between values obtained from continuous monitoring of partial pressure of carbon dioxide in membrane oxygenator exhaustion (PeCO2) and the results observed on arterial blood gas test.

METHODS

Participated in this study 40 patients submitted to elective cardiovascular surgery with CPB. They were divided into two groups: Group 1, with 20 patients submitted to the surgical procedure using blood gas analysis at intermittent intervals (20 - 30 minutes); Group 2, with 20 patients operated with a capnography system adapted applied to membrane oxygenator exhaustion and blood gas test. A test was used to compare arterial partial pressure of carbon dioxide (PaCO2) from group 1 and group 2. In group 2, the strength of the correlation between PeCO2 and PaCO2 was evaluated by a linear regression test. The Bland-Altman method was used to determine the degree of agreement between the two variables.

RESULTS

Average and standard deviation of Group 1's PaCO2 (34.6 ± 7.44) and Group 2's PaCO2 / PeCO2 (36.5 ± 4.42) / (39.9 ± 3.98). There was no statistically significant difference in PaCO2 between the groups (P = 0.21). In group 2, PeCO2 and PaCO2 analyzed corrected for esophageal temperature obtained a positive linear correlation (r = 0.79, P < 0.001), the degree of agreement presented an average 3.47 ± 2.70 mmHg.

CONCLUSION

The continuous PeCO2 monitoring from cardiopulmonary bypass circuit has a positive impact on the result of PaCO2. This instrument confirms and maintains the carbon dioxide (CO2) values into reference parameters.

Fibonacci's Golden Ratio-An Innovative Approach to the Design and Management of Extra-Corporeal Circulation

Technological advances in the field of extracorporeal circulation (ECC) over the past decade have led to numerous methods for monitoring metabolism and coagulation during cardiopulmonary bypass (CPB), as well as materials with improved biocompatibility, which has reduced the risk associated with cardiopulmonary bypass. However, ECC is still predominantly based on a traditional design that involves the use of roller pumps. This exposes the patient to a variety of pathophysiological consequences, both intra- and postoperative, such as postoperative cognitive disorders, hemolysis and hemodilution, systemic inflammation and changes in coagulation. This article describes the advantages of an ECC circuit inspired by the Fibonacci Golden Ratio, which does not use a roller pump, in a prospective study on patients undergoing elective cardiac surgery, compared to conventional ECC. During CPB, echocardiography was used to estimate the quality of fluid dynamics in the extracorporeal circuit and the patient's arterial vessels, a DO2 management system was used to evaluate metabolism, and an electronic system was used to determine gaseous microemboli (GME) counts. Fibonacci ECC offered superior intraoperative fluid dynamics, reduced the production of and improved the elimination of GME, and improved intraoperative metabolism, particularly with regard to oxygen delivery and extraction. The improvements in fluid dynamics and metabolic variables were associated with a reduction in the incidence of pathophysiological events compared to the conventional system, particularly regarding transitory cognitive disorders, and a shorter stay in intensive care.

Sixty Years After Tetralogy of Fallot Correction

This report describes one of the early cases of open surgical correction of tetralogy of Fallot performed by C. Walton Lillehei and colleagues at the University of Minnesota and discusses findings from the patient's follow-up 60 years later.

Impact of Heparin- or Nonheparin-Coated Circuits on Platelet Function in Pediatric Cardiac Surgery

BACKGROUND

Extracorporeal circuit coating has been shown to improve coagulation derangements during pediatric cardiopulmonary bypass (CPB). This study compared platelet function and hemostasis activation in pediatric cardiac surgery conducted with nonheparin coating (Balance; Medtronic, Minneapolis, MN) versus heparin-based coating (Carmeda; Medtronic) circuits.

METHODS

A prospective, randomized, double-center trial was conducted in children older than 1 month undergoing congenital heart disease treatment. Blood samples were collected at baseline (T0), 15 minutes after the start of CPB (T1), and 15 minutes (T2) and 1 hour after the conclusion of CPB (T3). The primary end point of the study was to detect potential differences in β-thromboglobulin levels between the two groups at T2. Other coagulation and platelet function indicators were analyzed as secondary end points.

RESULTS

The concentration of β-thromboglobulin increased significantly at T2 in both groups. However, there was no significant difference between the groups across all time points. There was no difference in the secondary end points between the groups.

CONCLUSIONS

The two circuits showed similar biological effects on platelet function and coagulation. This observation may be useful in optimizing the conduct of CPB and in rationalizing its cost for the treatment of congenital heart disease.

Bloodless Heart Surgery for an 11-kg Infant of the Jehovah's Witness Faith Undergoing Second Repair for Complete Atrioventricular Canal

Bloodless pediatric cardiac surgery is the intent of most surgical centers especially in the Jehovah's Witness population where it is a desire not to administer blood products because of religious belief. It is a tremendous feat, considering that most pediatric cardiovascular prime volumes are more than 20% of the patient's estimated blood volume (EBV). We report on our bloodless strategy for a 2-year old Jehovah's Witness with trisomy 21 and complete atrioventricular canal repair, who underwent atrial septal defect and ventricular septal defect patch closure, pulmonary artery debanding, and pulmonary arterioplasty. We modified our circuit to reduce our prime volume to approximately 10% of the EBV and removed 200 mL of the patient's blood before surgery as acute normovolemic hemodilution. We did not alter our institutional standards for transfusion of blood and blood products. The post cardiopulmonary bypass (CPB) hematocrit was 30%. We conclude that bloodless CPB surgery can be performed safely in Jehovah's Witness patients with a carefully planned interdisciplinary approach.

[Surgical Devices for Minimally Invasive Cardiac Surgery(MICS)]

Minimally invasive cardiac surgery(MICS)rapidly has become popular in recent years. To perform meticulous surgical procedures in the limited space, specially designed surgical instruments are very useful. For excellent exposure of the surgical target, thoracoscopic system with high imaging quality such as 4K or 3D HD endoscopy is often used. An articulated rib spreader and/or soft tissue retractor is also useful since those instruments do not interfere with other surgical instruments. A suture catcher is used to pull traction sutures through the chest wall. There are various types of atrial retractor designed for MICS. For fine manipulation in the limited space, long-shafted forceps, needle holders, and scissors are necessary. Those instruments reach deeply located targets and do not interfere surgeon's and endoscopic view or other instruments. A knot pusher is another essential device to tie knots through a small incision. The automatic tying device is available outside the country. For cardiopulmonary bypass, cannulas designed for peripheral access are used. Most of those cannulas have multiple side holes that work well for excellent perfusion and drainage. There are also specially designed aortic cross-clamps. To make surgeons more comfortable and improve quality of MICS, surgical devices for MICS need to be further innovated.

Technique of Complete Heart Isolation with Continuous Cardiac Perfusion During Cardiopulmonary Bypass: New Opportunities for Gene Therapy

Cardiopulmonary bypass (CPB) featuring complete heart isolation and continuous cardiac perfusion is a very promising approach for solving the problem of efficient gene delivery. In the technique presented here, separate pumps are used for the systemic and cardiac circuits. This system permits continuous isolated arrested heart perfusion through optimizing a number of delivery parameters including temperature, flow rate, driving pressure, ionic composition, and exposure time to the cardiac vessels. During complete cardiac isolation, the blood vector concentration trended from 11.51 ± 1.73 log genome copies (GCs)/cm³ to 9.84 ± 1.65 log GC/cm³ (p > .05). Despite restructuring a very high concentration to the heart, GCs were detectable in the systemic circuit. These values over time were near negligible by comparison but detectable 1.66 ± .26 during 20 minutes of recirculation and did not change (p > .05). After the completion of the recirculation interval and subsequent washing procedure, the initial systemic blood vector GC concentration slightly increased to 2.08 ± .38 log GCs/cm³ (p > .05). During the recirculation period, we supported flow via the cardiac circuit around 300 mL/min. In this technique of heart isolation with continuous cardiac perfusion, >99% of the vector remains in coronary circulation during recirculation period. The animal's non recirculation blood, or that in the system, was routinely tested during and after recirculation to contain much less than 1% of the original dose obtained via logging concentration of therapeutic over time. All of the sheep in this group recovered from anesthesia and received critical postoperative care, including all organ function, in the first 24-36 hours. Twenty-one sheep (84%) survived to euthanasia at 12 weeks. Average CPB time was 107 ± 19.0 minutes and cross-clamp time was 49 ± 7.9 minutes. This technology readily provides multiple pass recirculation of genes through the heart with minimal side effects of collateral expression of other organs.

M. chimaera: A Multi-Headed Pathogen

We present the case of a 64-year-old man with Mycobacterium chimaera prosthetic aortic valve endocarditis likely acquired through exposure to a contaminated heater-cooler device used for cardiopulmonary bypass during valve replacement. This case demonstrates multi-system involvement with a non-tuberculous mycobacterial species that was previously not considered a significant human pathogen. We review the key features of the case and review published literature regarding an international outbreak of M. chimaera arising from point-source contamination during the manufacturing process. This report highlights the importance of clinician awareness of this international outbreak.

A Small Scale Oxygenator for Cardiopulmonary Bypass in Rats

Cardiopulmonary bypass (CPB) devices replace transiently the function of both heart and lungs, allowing the investigator to work safely on a stopped heart. Although this technology has greatly improved since its first applications in the early 1950's there is still no definitive rat CPB model, various experiments reporting drawbacks like pulmonary edema, large priming volumes, etc. We present a new oxygenator that can be used in cardiopulmonary bypass experiments in rats, simple in design and efficient in function, in which the process of blood oxygenation takes place in a vertical cylinder filled up with air or oxygen, with blood being spread onto the wall and then trickling down in a thin layer that facilitates the oxygen transfer. The oxygenation is efficient, the pO2 reaches levels of almost 150 mmHg (physiological level is around 100 mmHg) in conditions of oxygen saturation of over 99% (normal levels 95%-98%).

Reduced Systemic Heparin Dose with Phosphorylcholine Coated Closed Circuit in Coronary Operations

In this prospective cohort study we addressed the clinical impact of a reduced anticoagulation protocol on the hospital outcome of patients undergoing coronary revascularization with cardiopulmonary bypass.

364 consecutive low to moderate risk patients scheduled for elective isolated coronary operations were admitted to the study. 184 patients (Control Group) received conventional open circuits and full systemic anticoagulation (target activated clotting time 480 seconds); 180 patients (Intraoperative ECMO group) received closed, phosphorylcholine coated circuits and a reduced systemic heparin dose (target activated clotting time 320 seconds).

Patients of the Intraoperative ECMO group had less requirement for allogeneic blood products (odds ratio 0.55, 95% confidence interval 0.34–0.92, p= 0.02), a significant containment of blood loss (374 ± 278 mL vs. 463 ± 321 mL in Control group, p= 0.005) a lower postoperative peak serum creatinine levels (1.19 ± 0.48 mg/dL vs. 1.41 ± 0.94 mg/dL in Control group, p= 0.048), and a significant lower rate of severe morbidity (odds ratio 0.27, 95% confidence interval 0.09–0.81, p= 0.02). A reduction of systemic anticoagulation is feasible with a non-heparin-bonded, closed biocompatible circuit, and results in a significant improvement of the outcome of low to moderate risk coronary patients.

Augmentation of Abdominal Organ Perfusion during Cardiopulmonary Bypass with a Novel Intra-aortic Pulsatile Catheter Pump

Background

Current pulsatile pumps for cardiopulmonary bypass (CPB) are far from satisfactory because of the poor pulsatility. This study was undertaken to examine the efficiency of a novel pulsatile catheter pump on pulsatility and its effect on abdominal organ perfusion during CPB.

Methods

Twelve pigs weighing 89±11 kg were randomly divided into a pulsatile group (n=6) and a non-pulsatile group (n=6). All animals had a CPB for 120 min, aorta clamped for 60 min, temperature down to 32°C, and a perfusion flow of 60 ml/kg/min. In the pulsatile group, a 21 Fr intra-aortic pulsatile catheter, which was connected to a 40 mL membrane pump, was placed in the descending aorta and activated by a balloon pump driver during the first 90 minutes of CPB until aortic declamping. Hemodynamics, organ blood flow, body metabolism, and blood trauma were studied during experiments.

Results

Compared with the non-pulsatile group during CPB, the pulsatile group had a higher systolic blood pressure (P&0.01), higher mean arterial pressure (P&0.05), and higher blood flow to the superior mesenteric artery (P&0.05). The hemodynamic energy, indicated by the energy equivalent pressure (EEP) was higher in the gastrointestinal tract and kidney in the pulsatile group (P&0.01, P&0.01). Abdominal organ perfusion status, as indicated by SvO2 in the inferior vena cava, was higher in the pulsatile group (P&0.05) 30 min after cessation of CPB. Hemolysis indicated by release of free hemoglobin during CPB was similar in the two groups.

Conclusion

Applying the pulsatile catheter pump in the descending aorta is effective in supplying the pulsatile flow to the abdominal organs and results in improved abdominal organ perfusion during the ischemic phase of CPB.

Use of a Modified Cardiopulmonary Bypass Circuit for Suction Embolectomy with the AngioVac Device

The AngioVac suction cannula and circuit were designed for the percutaneous removal of soft thrombus and emboli in procedures requiring extracorporeal circulatory support. We describe a modification of the AngioVac suction catheter and cardiopulmonary bypass (CPB) circuit to effectively remove thrombus while maintaining the ability to rapidly initiate full CPBs during a medical crisis. This article will discuss the design concepts of the modified circuit as well as procedural protocols and considerations. The design modifications of incorporating an oxygenator, reservoir, and bridge allow for an increased flexibility that allows adaption to veno-venous extracorporeal membrane oxygenation or full CPB support when required for oxygenation or hemodynamic support.

A Dedicated Perfusion Electronic Medical Record with Discrete Epic Integration

Enterprise electronic medical records (EMR) have largely become a standard since their use was mandated by The American Recovery and Reinvestment Act of 2009. However, perfusion departments have adopted true perfusion EMRs at various rates. In our efforts to integrate with the institutions EMR while enjoying the benefits of an EMR designed specifically for perfusion practice, we developed a discrete data integration solution between Epic and the Spectrum Medical VIPER Perfusion EMR. This report describes our perfusion EMR selection criteria, design challenges, and documentation process.

Is There a Relationship between Pressure Gradients through Contemporary Oxygenators and Immune Cell Proliferation during Cardiopulmonary Bypass? A Pilot Study

There have been many advances in the perfusion equipment used for cardiopulmonary bypass (CPB) surgery. A key component, the membrane oxygenator, has had a number of modifications in recent years and a recent clinical evaluation demonstrated disparity in various aspects of device performance. One difference among oxygenators, which to-date has received little attention, was the impact on the patient's immune cells, with some oxygenators producing a significantly greater increase in immune cell numbers after cross clamp. Such increases in immune cell proliferation may contribute to the development of a systemic inflammatory response (SIR), which has been demonstrated to have a negative impact on patient outcomes. Although factors contributing to immune cell proliferation during CPB are recognized to be multi-factorial, the goal of the current communication was to perform an ad hoc analysis of these raw data for evidence that pressure gradients through an oxygenator contributes to this outcome. Despite the observation that higher-pressure gradient oxygenators appeared to associate with increased immune cell proliferation, no correlation was detected in this analysis. This finding, however, provides further evidence for the complex nature of inflammation during CPB, which deserves ongoing discussion and investigation.

Use of Volatile Anesthetic Agent in Extracorporeal Circuit as a Cause of Break in Polycarbonate Connector-Lessons Learnt

Mishaps, near misses, and lethal incidents are known to occur during cardiopulmonary bypass. We share one such rare case of break in polycarbonate connector because of the use of isoflurane in extracorporeal circuit and its successful management.

Lean Flow: Optimizing Cardiopulmonary Bypass Equipment and Flow for Obese Patients-A Technique Article

The goal of this chart review was to investigate the use of down-sized cardiopulmonary bypass (CPB) circuits for obese patients. The effects of transitioning from larger to smaller oxygenators, reservoirs, and arteriovenous tubing loops were evaluated through a retrospective review of 2,816 adult non-congenital procedure perfusion records. This technique report and case series is a continuation of our original prescriptive CPB circuit quality improvement project. An algorithm was derived to adjust body surface area (BSA) to lower body mass index (BMI) to provide down-sized extracorporeal circuit components capable of meeting the metabolic needs of the patient. As a result of using smaller circuits, decreased priming volumes led to significantly increased hemoglobin (HB) nadirs (p < .05) leading to significant decreases in homologous donor blood product exposures (p < .05). Patients with large BSAs were supported safely with smaller circuits by using lean body mass (LBM)-adjusted BSA and target blood flow algorithm. Based on this case series, large BMI patients may be safely supported with smaller circuits selected based on BSAs adjusted more toward LBM. Use of smaller circuits in high BMI patients led to higher HB nadirs and less donor blood components during the surgical procedure. Renal function and hospital stay were not affected by this approach.

Unexplained Obstruction of an Integrated Cardiotomy Filter During Cardiopulmonary Bypass

Cardiopulmonary bypass (CPB) is considered relatively safe in most cases, yet is not complication free. We present a case of an integrated cardiotomy filter obstruction during CPB, requiring circuit reconfiguration. Approximately an hour after uneventful initiation of CPB the integrated cardiotomy filter became obstructed over several minutes, requiring circuit reconfiguration using an external cardiotomy filter to maintain functionality. Following reconfiguration, CPB was maintained with a fully functional circuit allowing safe patient support throughout the remainder of CPB. Postoperatively, there was no sign of thrombus or mechanical obstruction of the filter, which was sent to the manufacturer for analysis. The cause of the obstruction was unclear even after chemical analysis, visual inspection, and a review of all techniques and products to which the patient was exposed. The patient had a generally routine hospital stay, with no signs or symptoms related to the incident. To our knowledge, this is the first report describing an obstructed integrated cardiotomy filter. An appropriate readiness plan for such an incident includes proper venting of the filter chamber, a method for detecting an obstruction, and a plan for circuit reconfiguration. This case illustrates the need for a formal reporting structure for incidents or "near miss" incidents during CPB.

The Impact of Roller Pump vs. Centrifugal Pump on Homologous Blood Transfusion in Pediatric Cardiac Surgery

Centrifugal pumps are considered to be less destructive to blood elements (1) when compared to roller pumps. However, their large prime volumes render them unsuitable as arterial pumps in heart lung machine (HLM) circuitry for children. In November of 2014, the circuit at Arnold Palmer Hospital, a Biomedicus BP-50 with kinetic assist venous drainage (KAVD) and 1/4″ tubing was converted to a roller pump in the arterial position with gravity drainage. Vacuum-assisted venous drainage (VAVD) was mounted on the HLM as a backup, but not used. Tubing was changed to 3/16″ in the arterial line in patients <13 kg. A retrospective study with a total of 140 patients compared patients placed on cardiopulmonary bypass (CPB) with Biomedicus centrifugal pumps and KAVD (Centrifugal Group, n = 40) to those placed on CPB with roller pumps and gravity drainage (Roller Group, n = 100). Patients requiring extra-corporeal membrane oxygenation (ECMO)/cardio-pulmonary support (CPS) or undergoing a hybrid procedure were excluded. Re-operation or circulatory arrest patients were not excluded. Prime volumes decreased by 57% from 456 ± 34 mL in the Centrifugal Group to 197 ± 34 mL in the Roller Group (p < .001). There was a corresponding increase in hematocrit (HCT) of blood primes and also on CPB. Intraoperative homologous blood transfusions also decreased 55% from 422 mL in the Centrifugal Group to 231 mL in the Roller Group (p < .001). The Society of Thoracic Surgeons--European Association for Cardio-Thoracic Surgery (STAT) categorized intubation times and hospital length of stay (LOS) for all infants showed a trend toward reduction, but was not statistically significant. Overall mortality was 5% utilizing the centrifugal configuration and 0% in the roller pump cohort. We demonstrated that the transition to roller pumps in the arterial position of the HLM considerably reduced our priming volume and formed a basis for a comprehensive blood conservation program. By maintaining higher HCTs on CPB, we were able to reduce intraoperative homologous blood transfusions.

Evaluation of a new condensed extra-corporeal circuit for cardiac surgery: a prospective randomized clinical pilot study

This prospective randomized clinical pilot study was conducted to evaluate a recently introduced reduced volume CPB system that is coated with the biopassive Xcoating™. Twenty-two patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB), either with a fully heparin-coated CPB circuit (control, n=11) or with an Xcoating™ coated condensed extra-corporeal circuit (CondECC, n=11), were included.

We examined activation of the complement system (C3bc and C4bc), activation of neutrophils (BPI), the acute phase response (interleukin (IL)-6, and acute phase proteins (LBP, AGP, and CRP)), myocardial tissue injury (troponin T), hemolysis (free hemoglobin (FHb)), and clinical outcome parameters. Preoperative risk profiles were identical for both patient groups. All patients went through the procedure without major complications and were discharged from the hospital. FHb and BPI levels at the end of pump support ( p <0.01) and at 15 min after the administration of protamine ( p <0.05) were significantly higher in the control group. In addition, FHb levels were still significantly elevated upon arrival on the cardiothoracic intensive care unit (CICU) in the control group ( p <0.05). C3bc and C4bc, acute phase proteins, IL-6, and troponin T concentrations, and clinical outcome variables were identical in both patient groups.

In conclusion, the evaluated condensed extracorporeal circuit is a flexible and multifunctional CPB sytem that offers safe procedures. Furthermore, the results indicate improved biocompatibility of this option for extracorporeal circulation.

The use of a mini bypass system (Cobe Synergy) without venous and cardiotomy reservoir in a mitral valve repair: a case report

The use of mini cardiopulmonary bypass circuits is an emerging technology. The venous and cardiotomy reservoir have been excluded from the circuit. This results in a reduction of the blood contact surface area and of the priming volume.

Entrainment of venous air, however, remains a drawback in the widespread acceptance of using these mini circuits.

The technique described resolves this problem by automatic removal of venous air, and explains how this mini cardiopulmonary bypass circuit was utilized on a 64-year-old female presented for a mitral valve repair.

In the absence of a cardiotomy reservoir, an autotrans-fusion cell separator was used to process shed blood and, after CPB, the residual pump blood.

This mini bypass circuit, with the safety feature to remove automatically venous air, provided an additional degree of protection.

In our experience, mini bypass circuits allow us safely to perform cardiopulmonary bypass during valve procedures.

Development of cardiopulmonary bypass – A historical review

The idea of isolated organ perfusion, a precursor of cardiopulmonary bypass, came by Legalois in 1812. First isolated organ perfusion was described by Loebell in 1849. The first closed system for oxygenation and returning the blood through arteries was created by Frey and Gruber in 1885. Gibbon Jr. is considered the father of extracorporeal circulation. In spring of 1934 he began constructing a machine for extracorporeal circulation in Boston. He published the first description of this system in 1937. Gibbon won the grant of the International Business Machines Corporation for developing the machine in 1947. Together they developed Model I in 1949 and Model II in 1951. After a few unsuccessful attempts in 1952, the first successful surgical intervention on the heart (closure of atrial septal defect) using cardiopulmonary bypass was performed on May 6, 1953. In 1945, Kirklin and his working group reported on a series of eight successfully treated patients in a row who underwent surgery with extracorporeal circulation. First successful valve surgery under the direct vision was performed by Dodrill in 1952, using his “Michigan Heart” machine as a right heart bypass. Using cardiopulmonary bypass, cardiac surgeons can deal with the complex cardiac pathology and save millions of lives.

Continuous Blood Viscosity Monitoring System for Cardiopulmonary Bypass Applications

This paper proposes an algorithm that estimates blood viscosity during cardiopulmonary bypass (CPB) and validates its application in clinical cases. The proposed algorithm involves adjustable parameters based on the oxygenator and fluid types and estimates blood viscosity based on pressure-flow characteristics of the fluid perfusing through the oxygenator. This novel nonlinear model requires four parameters that were derived by in vitro experiments. The results estimated by the proposed method were then compared with a conventional linear model to demonstrate the former's optimal curve fitting. The viscosity (η_e) estimated using the proposed algorithm and the viscosity (η) measured using a viscometer were compared for 20 patients who underwent mildly hypothermic CPB. The developed system was applied to ten patients, and η_e was recorded for comparisons with hematocrit and blood temperature. The residual sum of squares between the two curve fittings confirmed the significant difference, with p < 0.001. η_e and η showed a very strong correlation with R² = 0.9537 and p < 0.001. Regarding the mean coefficient of determination for all cases, the hematocrit and temperature showed weak correlations at 0.33 ± 0.14 and 0.22 ± 0.21, respectively. For CPB measurements of all cases, η_e was more than 98% distributed in the range from 1 to 3 mPa⋅s. This new system for estimating viscosity may be useful for detecting various viscosity-related effects that may occur during CPB.

Selective Heart, Brain and Body Perfusion in Open Aortic Arch Replacement

Open aortic arch replacement is a complex and challenging procedure, especially in post dissection aneurysms and in redo procedures after previous surgery of the ascending aorta or aortic root. We report our experience with the simultaneous selective perfusion of heart, brain, and remaining body to ensure optimal perfusion and to minimize perfusion-related risks during these procedures. We used a specially configured heart-lung machine with a centrifugal pump as arterial pump and an additional roller pump for the selective cerebral perfusion. Initial arterial cannulation is achieved via femoral artery or right axillary artery. After lower body circulatory arrest and selective antegrade cerebral perfusion for the distal arch anastomosis, we started selective lower body perfusion simultaneously to the selective antegrade cerebral perfusion and heart perfusion. Eighteen patients were successfully treated with this perfusion strategy from October 2012 to November 2015. No complications related to the heart-lung machine and the cannulation occurred during the procedures. Mean cardiopulmonary bypass time was 239 ± 33 minutes, the simultaneous selective perfusion of brain, heart, and remaining body lasted 55 ± 23 minutes. One patient suffered temporary neurological deficit that resolved completely during intensive care unit stay. No patient experienced a permanent neurological deficit or end-organ dysfunction. These high-risk procedures require a concept with a special setup of the heart-lung machine. Our perfusion strategy for aortic arch replacement ensures a selective perfusion of heart, brain, and lower body during this complex procedure and we observed excellent outcomes in this small series. This perfusion strategy is also applicable for redo procedures.

Effect of Normobaric versus Hypobaric Oxygenation on Gaseous Microemboli Removal in a Diffusion Membrane Oxygenator: An In Vitro Comparison

Gaseous microemboli (GME) are an abnormal physiological occurrence during cardiopulmonary bypass and extracorporeal membrane oxygenation (ECMO). Several studies have correlated negative sequelae with exposure to increased amounts of GME. Hypobaric oxygenation is effective at eliminating GME in hollow-fiber microporous membrane oxygenators. However, hollow-fiber diffusion membrane oxygenators, which are commonly used for ECMO, have yet to be validated. The purpose of this study was to determine if hypobaric oxygenation, compared against normobaric oxygenation, can reduce introduced GME when used on diffusion membrane oxygenators. Comparison of a sealed Quadrox-iD with hypobaric sweep gas (.67 atm) vs. an unmodified Quadrox-iD with normal atmospheric sweep gas (1 atm) in terms of GME transmission during continuous air introduction (50 mL/min) in a recirculating in vitro circuit, over a range of flow rates (3.5, 5 L/min) and crystalloid prime temperatures (37°C, 28°C, and 18°C). GME were measured using three EDAC Doppler probes positioned pre-oxygenator, post-oxygenator, and at the arterial cannula. Hypobaric oxygenation vs. normobaric oxygenation significantly reduced hollow-fiber diffusion membrane oxygenator GME transmission at all combination of pump flows and temperatures. There was further significant reduction in GME count between the oxygenator outlet and at the arterial cannula. Hypobaric oxygenation used on hollow-fiber diffusion membrane oxygenators can further reduce GME compared to normobaric oxygenation. This technique may be a safe approach to eliminate GME during ECMO.

Effects of Purge-Flow Rate on Microbubble Capture in Radial Arterial-Line Filters

The process of microbubble filtration from blood is complex and highly dependent on the forces of flow and buoyancy. To protect the patient from air emboli, arterial-line filters commonly use a micropore screen, a large volume housing with purpose-built shape, and a purge port to trap, separate, and remove circulating microbubbles. Although it has been proposed that an insufficient buoyancy force renders the purge port ineffective at removing microbubbles smaller than 500 μm, this research attempts to investigate the purge flow of an arterial-line filter to better understand the microbubble removal function in a typical radial filter design. As its primary objective, the study aims to determine the effect of purge-flow rate on bubble capture using air bolus injections from a syringe pump with 22-gauge needle and Doppler ultrasound bubble detection. The measureable bubble size generated in the test circuit ranged between 30 and 500 μm, while purge flow was varied between .1 and .5 L/min for testing. Statistical analysis of the test data was handled using a repeated measures design with significance set at p < .05 level. Outcomes demonstrated that higher purge flows yielded higher bubble counts, but the effect of purge-flow rate on bubble capture decreased as bubble size increased. Results also showed that purge flow from the test filter was capable of capturing all bubble sizes being generated over the entire flow range tested, and confirms utility of the purge port in removing microbubbles smaller than 500 μm. By analyzing bubble counts in the purge flow of a typical radial-filter design, this study demonstrates that currently available micropore filter technology is capable of removing the size range of bubbles that commonly pass through modern pump-oxygenator systems and should continue to be considered during extracorporeal circulation as a measure to improve patient safety.

Comparison of two different extracorporeal circuits on cerebral embolization during cardiopulmonary bypass in children

Objective: To compare the effect of two different extra-corporeal circuits on the counts of high-intensity transient signals (HITS) during pediatric cardiopulmonary bypass (CPB). Methods: Transcranial Doppler was used to detect HITS associated with extracorporeal sources during the period of aortic crossclamping in the middle cerebral artery of children undergoing CPB. Based on body size, children were assigned one of two extracorporeal circuits (A or B). Circuit A included a D-705 oxygenator and associated reservoir, and circuit B included a Lilliput oxygenator and reservoir. Patients were further classified into two groups according to the complexity of surgical repair: single simple lesions or multiple complex lesions. Results: We studied 109 pediatric patients. Surgery for multiple complex lesions was associated with longer periods of aortic crossclamping and CPB (p <0.0001). The median count of extra-corporeal HITS was 12 (25th, 75th percentiles: 3, 51). The type of extracorporeal circuit (p=0.012) and the complexity of surgical repair (p <0.0001) had an effect on the HITS counts. The use of circuit A was associated with higher HITS counts during surgery for multiple complex lesions compared to single simple lesions (p <0.0001). Conversely, no differences were found with the use of circuit B between these two surgical groups (p >0.25). During surgery for multiple complex lesions, patients treated with circuit A showed higher HITS counts than those with circuit B (p <0.01), but there were no circuit-related differences in HITS counts (p=0.30) during single simple lesions. Conclusion: Variations in the design characteristics of extracorporeal circuits can increase cerebral emboli during CPB in children. This may be related to the reduced ability of some circuits to remove emboli during long periods of CPB for complex congenital heart-surgery.

Prospective study on cardiopulmonary bypass prime reduction and its effect on intraoperative blood product and hemoconcentrator use

Purpose: Evaluate the feasibility and clinical significance of crystalloid prime reduction during the initiation of cardiopulmonary bypass (CPB) using a modified bridge on the cardioplegia delivery system.

Methods: Prospective trial of crystalloid prime reduction using a standard Duraflow®-coated CPB circuit and Vanguard® 2:1 cardio plegia delivery system. Standard prime volume was 1500 cc of Plasmalyte. Prime was reduced via the bridge in the cardioplegia system during initiation of CPB. Packed red blood cells (PRBC) were transfused for hematocrit (Hct) less than 24% while rewarming. A hemoconcentrator was used if the patient’s circulating blood volume exceeded 150% of calculated. All data were prospectively collected.

Results: Two hundred and twenty-two consecutive patients undergoing cardiac surgery utilizing CPB were evaluated. There were 107 patients with normal prime volume (NPV) and 115 patients with reduced prime volume (RPV). There was no significant difference in sex, mean age, weight, body surface area (BSA), pre-op Hct, procedure time or procedure between the two groups. There was no difference in total crystalloids infused by the anesthetists (average NPV 1205 cc versus RPV 1148 cc). The average RPV was 622 cc (range 400 - 1100 cc) or a 59% reduction. Post-op Hct revealed no difference (NPV 28% versus RPV 29%). There was a 24% reduction in patients requiring PRBC (NPV n=23 versus RPV n=18). The use of hemoconcentrators was reduced by 49% (NPV n=18 versus RPV n=11). The average urine output for both groups exceeded 100 cc/hour while on CPB.

Conclusion: Using a modified cardioplegia delivery system is a safe and effective method of CPB prime reduction. A RPV resulted in fewer patients requiring PRBC transfusions and fewer hemoconcentrators used. Based on our experience, we would recommend attempting to reduce prime volume in all patients undergoing CPB.

Use of a dynamic bubble trap in the arterial line reduces microbubbles during cardiopulmonary bypass and microembolic signals in the middle cerebral artery

Neurological complications remain an important cause of morbidity and mortality of patients following cardiopulmonary bypass (CPB). Microemboli, as well as cerebral hypoperfusion, are the main postulated mechanisms. This study demonstrates that the insertion of a dynamic bubble trap (DBT) into the curcuit reduces microbubbles in the arterial line and microembolic signals (MES) in the middle cerebral arteries (MCAs).

We investigated 12 patients during coronary artery bypass grafting (CABG). The DBT was inserted between the arterial filter and the arterial cannula. For detection of microemboli before and after the DBT, a special ultrasound Doppler device was used. MES were detected by transcranial Doppler monitoring in both MCAs of the patients. Microbubbles and MES were counted during bypass. These data were compared to 12 patients who were operated in a previous period without the use of a DBT. There were no significant differences in both groups with respect to gender, age, crossclamp and bypass time and number of anastomoses. In the group without a DBT in the circuit, a mean of 6311 microbubbles per operation could be observed distal to the arterial filter, corresponding to 282 MES. After inclusion of a DBT, we could register, in the second group, 8496 microemboli proximal and 2915 distal of the DBT, corresponding to 89 MES per operation. The reduction rate of microbubbles in the tubing was 65.7%, corresponding to a reduction in MES of about 86.2%. We conclude that the insertion of a DBT in the arterial line of CPB circuit protects the cerebrovascular system from microembolic events, as demonstrated by lower MES counts.

Standards update on perfusion equipment and practice

Standards applying to the manufacture, testing and labeling of perfusion components and equipment, as well as those dealing with clinical use of extracorporeal circulation, have been promulgated by both standards-setting organizations and professional organizations. The rationale and purpose for device standards are discussed, and many organizations and the processes involved in developing standards are described. Perfusion checklists used during equipment set-up, use and at termination have a long track record of acceptance by clinicians. Evolving techniques have prompted revisions to the basic perfusion checklist, which should be considered a guide for development of institution-specific checklists. Current and future work by international standards-setting organizations is described.

Ex vivo evaluation of a new neonatal/infant oxygenator: comparison of the Terumo CAPIOX® Baby RX with Dideco Lilliput 1 and Polystan Safe Micro in the piglet model

Objective: A newly developed neonatal and infant oxygenator with a nonheparin biocompatible polymer coating, low priming volume (43 mL), high oxygen transfer, wide operating range (<1.5 L/min) and low pressure drop represents a promising solution for cardiac surgery in neonates and infants. We compared the new CAPIOX® Baby RX, Terumo (BRX) with two commonly used neonatal oxygenators: Dideco Lilliput 1 (DL1) and Polystan Safe Micro (PSM) in a piglet model.

Methods: Fifteen piglets (5.6±1.3 kg) were placed on standardized cardiopulmonary bypass (CPB) for 6 hours using one of the three oxygenators ( n = 5 in each group). After 120 min, the system was cooled to 25°C for 60 min and then returned to normothermia. Arterial and venous blood gas data and temperature were recorded continuously by a CDI500 System (Terumo). Pressure drop, FiO2 and gas flow were recorded. Blood samples were taken before CBP, after 10 min, before and after cooling, and at the end. Total blood counts, thrombin-antithrombin complex and plasma-free haemoglobin (PfHb) were measured.

Results: All oxygenators showed acceptable performance for the duration of CPB. The BRX had lower mean gas flow (0.33±0.05 L/min) and FiO2 (0.43± 0.02%) throughout CPB than the DL1 (1.14±0.25 L/min, p = 0.006 and 0.60±0.02%, p = 0.009, respectively) or the PSM (1.47±0.87 L/min and 0.54±0.08%, p = ns). Pressure drop in the BRX group ranged from 12 to 22 mmHg. This was significantly lower than in the DL1 group (39-65 mmHg, p = 0.005). In the PSM group, values ranged between 24 and 33 mmHg (p = ns). The increase in PfHb at six hours was significantly lower in the BRX (11.3±4.2 ng/dL) versus the DL1 (42.2±6.1 ng/dL, p = 0.004) and the PSM (56.7±15.5 ng/dL, p = 0.045).

Conclusions: The BRX is as safe as the DL1 and the PSM, with superior performance in pressure drop, efficient blood gas management and lower haemolysis. The BRX exhibited the lowest prime, hold-up volume and breakthrough time.

Comparison of hollow-fiber membrane oxygenators in terms of pressure drop of the membranes during normothermic and hypothermic cardiopulmonary bypass in neonates

The objective of this study was to investigate the effects of two hollow-fiber membrane oxygenators, the Capiox SX10 and the Lilliput 901, on pressure drop of the membranes during normothermic and hypothermic cardiopulmonary bypass (CPB) in neonates.

Methods: Twenty-six congenital heart surgery patients (n=13 in each group) with a mean weight of 3 kg were included in this study. Pressure drops of the membranes, pre- and post-oxygenator extracorporeal circuit pressures (ECC) were recorded during normothermic CPB, hypothermic CPB (208C) and after rewarming. There were no differences between the groups in mean arterial pressure, pump flow rate, temperature, duration of CPB, cross- clamp time or the severity of the surgical repairs.

Results: Pressure drop of the Capiox SX10 oxygenator was significantly lower during normothermic (329/10 versus 559/16 mmHg, p B/0.001), hypothermic (389/15 versus 729/18 mmHg, p B/0.001) and post-rewarming (429/13 versus 729/21 mmHg, p B/0.001) periods compared to the Lilliput oxygenator. In the Capiox group, the pre-oxygenator ECC pressure was also significantly lower during normothermic CPB (1429/27 versus 1849/43 mmHg, p B/0.01), hypothermic CPB (1629/30 versus 1999/38 mmHg, p B/0.01) and after rewarming periods (1729/32 versus 2129/42 mmHg, p B/0.01). Post-oxygenator pressures in the Capiox group were also lower than in the Lilliput group, but results were not statistically significant.

Conclusions: These results suggest that the Capiox SX10 hollow-fiber membrane oxygenator produced significantly lower membrane pressure drops and pre- and post-oxygenator ECC during normothermic and hypothermic CPB. Thus, blood trauma with the Capiox during extracorporeal circulation may be significantly lower compared to the Lilliput. Further studies, including the level of complements, platelets, neutrophils and cytokines, with these oxygenators are warranted.

Testing of heat exchangers in membrane oxygenators using air pressure

All heat exchangers (HE) in membrane oxygenators are tested by the manufacturer for water leaks during the production phase. However, for safety reasons, it is highly recommended that HEs be tested again before clinical use. The most common method is to attach the heater-cooler to the HE and allow the water to recirculate for at least 10 min, during which time a water leak should be evident. To improve the detection of water leaks, a test was devised using a pressure manometer with an integrated bulb used to pressurize the HE with air.

The cardiopulmonary bypass system is set up as per protocol. A pressure manometer adapted to a 1/2″ tubing is connected to the water inlet side of the oxygenator. The water outlet side is blocked with a short piece of 1/2″ dead-end tubing. The HE is pressurized with 250 mmHg for at least 30 sec and observed for any drop.

Over the last 2 years, only one oxygenator has been detected with a water leak in which the air-method leak-test was performed. This unit was sent back to the manufacturer who confirmed the failure.

Even though the incidence of water leaks is very low, it does occur and it is, therefore, important that all HEs are tested before they are used clinically. This method of using a pressure manometer offers many advantages, as the HE can be tested outside of the operating room (OR), allowing earlier testing of the oxygenator, no water contact is necessary, and it is simple, easy and quick to perform.

Effects of two differently heparin-coated extracorporeal circuits on markers for brain and myocardial dysfunction

Objective: The two most commonly used heparin-coated systems for cardiopulmonary bypass (CPB) are the Carmeda Bio-Active Surface (CBAS) (Medtronic, Minneapolis, MN, USA) and the Duraflo II coating (Baxter Healthcare, Irvine, CA, USA). The two surfaces are technically unequal and previous experimental studies have demonstrated disparities in effects on the immune system and blood cells. However, little is known concerning the influence of the two surfaces on markers for brain and myocardial dysfunction.

Methods: Forty patients undergoing elective, primary coronary bypass grafting with CPB were prospectively randomized to either the CBAS system or the Duraflo II circuit. During and after CPB, biological markers for brain dysfunction and myocardial injury were analysed.

Results: Both markers for brain dysfunction S-100B and neuron-specific enolase (NSE) increased significantly during CPB ( p =0.01). The elevation during bypass correlated significantly with the duration of CPB ( r = 0.39 and r= 0.38, respectively, both p< 0.02). NSE was somewhat more elevated in the Duraflo II group at the end of CPB ( p =0.01) and 5 h after CPB ( p= 0.02); for S-100B, there were no intergroup differences. Also, the markers related to myocardial injury, myoglobin and creatine kinase (CK-MB) mass increased during CPB ( p= 0.01), while elevation of troponin-I occurred 5 h after CPB ( p= 0.01). There were no statistically significant intergroup differences. No significant correlation was seen between the release of cardiac markers and the duration of CPB. The clinical course was similar in both groups.

Conclusions: Except for a slightly higher elevation of NSE at the end of CPB and 5 h after CPB in the Duraflo II group, there were no significant differences between the CBAS group and the Duraflo II group concerning markers for brain and myocardial dysfunction.

A new top-loading venous bag provides vacuum-assisted venous drainage

A new venous bag has been developed, prototyped, and tested. The new bag has its inlet, outlet purge, and infusion tubes extending upward from the top of the bag, and are threaded through, bonded to, and sealed within a flat rigid top plate. This design allows the bag to be hung from its top plate by its tubes. It also allows the bag to be: 1) dropped into or removed from its holder, as is done with existing hard-shell reservoirs so that its weight pulls it into the holder without the need for eyelets and hooks and 2) placed closer to the floor so that gravity drainage is facilitated. The V-Bag® (VB) is easily sealed within an accompanying rigid housing. Once sealed, vacuum applied to the housing is transmitted across the flexible walls of the bag to the venous blood. Thus, vacuum-assisted venous drainage (VAVD) is obtained as it is with a hard-shell reservoir, but without any contact of air with the blood. Bench tests, using a circuit that simulated the venous side of the cardiopulmonary bypass (CPB) circuit, showed that applying suction to the housing increased venous flow, and the fractional increase in flow was not a function of the venous cannula, but of the level of vacuum applied. In the gravity drainage mode, the bubble counts at the outlet of the V-Bag compared to two other bags were lower at any pumping condition. When used in the VAVD mode, bubble counts were two orders of magnitude lower than when using kinetically assisted venous drainage (KAVD) with a centrifugal pump. Results obtained with the VB suggest its clinical usefulness.

Evaluation of coated oxygenators in cardiopulmonary bypass systems and their impact on neurocognitive function

Introduction: Coronary artery bypass graft surgery (CABG) using cardiopulmonary bypass (CPB) is assumed to be associated with a decline of neurocognitive functions. This study was designed to analyse the neurocognitive function of patients with coronary heart disease before and after CABG and to determine possible protective effects of oxygenator surface coating on neurological outcome.

Methods: Forty patients scheduled for selective CABG were prospectively randomized into two groups of 20 patients each according to the type of hollow-fibre membrane oxygenator used. Non-coated oxygenators (Group A) were compared to phosphorylcholine (PC)- coated oxygenators (Group B). A battery of six neurological tests was administered preoperatively, 7 - 10 days and 4 - 6 months after surgery.

Results: One patient of Group A suffered from a perioperative stroke and died on postoperative day 3, presumably because of sudden heart failure. Two patients of Group A (10%) developed a symptomatic transitory delirious psychotic syndrome (STPT) on postoperative days 3 and 5. None of the patients of Group B had perioperative complications. The test analysis revealed a trend of declined neurocognitive function early after CABG, but did not show any difference in neurocognitive outcome between the two groups.

Discussion: PC coating of the oxygenators did not show any significant benefit on neurocognitive function after CABG using CPB.

A clinical, renal and immunological assessment of Surface Modifying Additive Treated (SMART™) cardiopulmonary bypass circuits

Biocompatible cardiopulmonary bypass (CPB) circuits aim to reduce contact activation and its physiological consequences. We investigated the hypothesis that use of Surface Modifying Additive (SMA)-treated circuits (Sorin Group Ltd) compared with non-SMA circuits would be associated with preservation of blood pressure during CPB and modulation of perioperative subclinical renal function (urinary α-1-microglobulin (α-1-m)) and plasma and urinary cytokine changes. In a study of low-risk CABG patients ( n=40), randomized to SMA ( n=20) versus non-SMA circuits ( n=20), we found better preserved blood pressure at CPB initiation in SMA patients (p <0.05), particularly in ACE-inhibited SMA patients ( n=11) versus ACE-inhibited non-SMA patients ( n=10) (p <0.05). Plasma anti-inflammatory IL-10, as well as urinary α-1-m, were elevated 48 hours postoperatively (p <0.05). SMA patients also had lower blood loss (p <0.05). SMA circuits have some clinical benefit, especially in ACE-inhibited patients.

Extracorporeal membrane oxygenation to cardiopulmonary bypass with a single circuit exposure

Due to the short supply of donor organs available, many patients decompensate or die while waiting for transplantation. Options for mechanical support for infants and pediatrics with congenital heart disease are limited because of the patient’s size and device availability. Extracorporeal membrane oxygenation (ECMO) is the most common means of cardiac and respiratory support for these patients. One of the many indications for ECMO use in cardiac patients is as a bridge to transplantation, with patients being transported to the operating room (OR) on ECMO support. Converting the ECMO circuit to an open cardiopulmonary bypass system in the OR minimizes the patient’s exposure to new circuitry, decreases further donor exposures and provides continuous support for patients in cardiac and/or respiratory failure. In addition, the ability to use modified ultrafiltration post-bypass aids in reducing extracellular fluid, increasing the hematocrit and improving hemodynamic stability following an extended duration of ECMO and bypass support. The integrity of the ECMO circuit is maintained and can be converted back to ECMO for support postoperatively if needed.

A new practical technique to reduce allogeneic blood exposure and hospital costs while preserving clotting factors after cardiopulmonary bypass: the Hemobag®

Recent data independently linking allogeneic blood use to increased morbidity and mortality after cardiopulmonary bypass (CPB) warrants the study of new methods to employ unique and familiar technology to reduce allogeneic blood exposure. The Hemobag® allows the open-heart team to concentrate residual CPB circuit contents and return a high volume of autologous clotting factors and blood cells to the patient.

Fifty patients from all candidates were arbitrarily selected to receive the Hemobag® (HB) therapy. A retrospective control group of 50 non-Hemobag® (NHB) patients were matched to the HB group patient-by-patient for comparison according to surgeon, type of procedure, age, body surface area (BSA), body weight and CPB time. Many efforts to conserve blood (Cell Saver® and ANH) were employed in both groups. Post-CPB cell washing of circuit contents was additionally employed in the control group.

There were no significant differences between the HB and NHB groups in regard to patient morphology, pre-op cell concentrations, distribution of surgeon or procedures (41% valve, 16% valve/coronary artery bypass graft (CABG), balance CABG), pump and ischemic times and Bayes National Risk scores. The average volume returned to the patient from the HB was 8179/198 mL (1 SD). Average processing time was 11 min. The Hemobag®contained an average platelet count of 2309/80 K/mm3, fibrinogen concentration of 4139/171 mg/dl, total protein of 8.09/2.8 gm/dl, albumin of 4.49/1.2 gm/dl and hematocrit of 439/7%. Factor VII, IX and X levels in three HB contents averaged 259% greater than baseline. Substantial reductions were achieved in both allogeneic blood product avoidance and cost to the hospital with use of the HB.

Infusion of the Hemobag® concentrate appears to recover safely substantial proteins, clotting factor and cell concentration for all types of cardiac procedures, maintaining the security of a primed circuit.

New technology increases perioperative haemoglobin levels for paediatric cardiopulmonary bypass: what is the benefit?

Increasing perioperative haemoglobin level by reducing priming volume and maintaining a safe cardiopulmonary bypass (CPB) system is the aim of every perfusionist. In this study, we have compared the two membrane oxygenators and pump systems used for paediatric bypass at the Royal Children’s Hospital on a regular basis since 1988. We looked at all patients who had the Cobe VPCML (Cobe Laboratories, Denver, CO, USA) and Terumo RX-05 (Terumo Corporation, Tokyo, Japan) oxygenators used for flows from 800 mL/min up to the maximum rated flow for the respective oxygenator from January 2002 until March 2004. The VPCML refers to using only the 0.4-m2 section of the oxygenator. The pump systems used were the Stöckert CAPS (Stöckert Instrumente GmbH, Munich, Germany) and Jostra HL 30 (Jostra AB, Lund, Sweden). Changing from the VPCML to the RX-05 resulted in a 37% reduction in priming volume. The introduction of the Jostra HL 30 with a custom-designed mast system reduced the priming volume by another 15%. This change in priming volume allowed a significant increase, from 6 to 34%, in the percentage of patients who received bloodless primes, and for those patients who received blood primes, an increase in haemoglobin (Hb) on bypass from 8.2 to 9.6 g/dL, on average.

Miniaturization in cardiopulmonary bypass

Cardiopulmonary bypass (CPB) remains the key technology for more complex cardiac operations. The perfusion equipment used nowadays has seen tremendous progress since its introduction into clinical practice 50 years ago. However, overall, CPB is still far from perfect. Major haemodilution is not only a problem for red cell-dependent gas transport, but also for the platelet and humeral factor-dependent coagulation, the protein-dependent intravascular oncotic pressure and so forth. Reduction of the priming volume through further miniaturization of CPB equipment is, therefore, the most obvious next step. A systematic approach needs to optimize all CPB components, including pumps, oxygenator/heat exchanger structures, filters, reservoirs, cardiotomy suction, tubings and cannulas. This report provides an update of already commercially available low prime perfusion devices (e.g., the CORx integrated pump-oxygenator) as well as promising prototypes like the smart suction system and the smartcanula.™

Arterial Limb Microemboli during Cardiopulmonary Bypass: Observations from a Congenital Cardiac Surgery Practice

Gaseous microemboli (GME) are known to be delivered to the arterial circulation of patients during cardiopulmonary bypass (CPB). An increased number of GME delivered during adult CPB has been associated with brain injury and postoperative cognitive dysfunction. The GME load in children exposed to CPB and its consequences are not well characterized. We sought to establish a baseline of arterial limb emboli counts during the conduct of CPB for our population of patients requiring surgery for congenital heart disease. We used the emboli detection and counting (EDAC) device to measure GME activity in 103 consecutive patients for which an EDAC machine was available. Emboli counts for GME <40 μ and >40 μ were quantified and indexed to CPB time (minutes) and body surface area (BSA) to account for the variation in patient size and CPB times. Patients of all sizes had a similar embolic burden when indexed to bypass time and BSA. Furthermore, patients of all sizes saw a three-fold increase in the <40 μ embolic burden and a five-fold increase in the >40 μ embolic burden when regular air was noted in the venous line. The use of kinetic venous-assisted drainage did not significantly increase arterial limb GME. Efforts for early identification and mitigation of venous line air are warranted to minimize GME transmission to congenital cardiac surgery patients during CPB.

Removal of Gross Air Embolization from Cardiopulmonary Bypass Circuits with Integrated Arterial Line Filters: A Comparison of Circuit Designs

Advances in technology, the desire to minimize blood product transfusions, and concerns relating to inflammatory mediators have lead many practitioners and manufacturers to minimize cardiopulmonary bypass (CBP) circuit designs. The oxygenator and arterial line filter (ALF) have been integrated into one device as a method of attaining a reduction in prime volume and surface area. The instructions for use of a currently available oxygenator with integrated ALF recommends incorporating a recirculation line distal to the oxygenator. However, according to an unscientific survey, 70% of respondents utilize CPB circuits incorporating integrated ALFs without a path of recirculation distal to the oxygenator outlet. Considering this circuit design, the ability to quickly remove a gross air bolus in the blood path distal to the oxygenator may be compromised. This in vitro study was designed to determine if the time required to remove a gross air bolus from a CPB circuit without a path of recirculation distal to the oxygenator will be significantly longer than that of a circuit with a path of recirculation distal to the oxygenator. A significant difference was found in the mean time required to remove a gross air bolus between the circuit designs (p = .0003). Additionally, There was found to be a statistically significant difference in the mean time required to remove a gross air bolus between Trial 1 and Trials 4 (p = .015) and 5 (p =.014) irrespective of the circuit design. Under the parameters of this study, a recirculation line distal to an oxygenator with an integrated ALF significantly decreases the time it takes to remove an air bolus from the CPB circuit and may be safer for clinical use than the same circuit without a recirculation line.

Spontaneous fracture and embolization of an inferior vena cava cannula: is it possible?

We present a case of spontaneous fracture and embolization of the distal part of a cannula into the left inferior lobar artery. The embolized fragment was captured with an angioplasty balloon and extracted through the right atrium appendage. No adverse event related to the embolization was observed and the patient was discharged with no sequelae.

A Novel Method to Detect an Oxygenator Defect Prior to Cardiopulmonary Bypass Initiation

Cardiopulmonary bypass (CPB) is a common practice in our era. The medical technology used for cardiac surgery goes through rigorous testing to ensure its safety. Unfortunately, it is not fail proof. Oxygenator failures are a rare occurrence but may lead to catastrophic events. We present a case where the preparation for initiating CPB was complicated by an oxygenator defect. After thorough examination, the oxygenator was found leaking from the gas exhaust port suggesting a disruption in continuity of the fibers. This was found by the vigilance of the perfusionist and a creative method to quickly assess the integrity of the oxygenation device. We describe a simple technique to help diagnose an oxygenator leak.