Venous air in the bypass circuit: a source of arterial line emboli exacerbated by vacuum-assisted drainage

Does the venous cannulation method affect gaseous embolic load to the patient during extracorporeal circulation?

IntroductionCardiopulmonary bypass (CPB) is essential for cardiac surgery but poses risks, including gaseous micro emboli (GME). While the incidence of stroke-a common clinical consequence of embolism-ranges from 1-5% in cardiac surgery, prevalence of GME during CPB remain poorly understood.ObjectivesTo quantitatively compare GME incidence in the arterial line between cavoatrial and bicaval cannulation during open-heart surgery. Secondary exploratory objectives include evaluating the impact of venous reservoir volume on GME, and the correlation between GME in the venous and arterial lines.MethodsThis single center randomized controlled trial was conducted at Sahlgrenska University Hospital, Sweden. Patients ≥18 years undergoing planned aortic valve repair/replacement with cavoatrial cannulation, or mitral valve repair/replacement with bicaval cannulation, with or without coronary artery revascularization, were screened for eligibility. Patients were further randomized to either venous reservoir volume of ≥300 mL (control) or 200-300mL (intervention). GME detection was performed using GAMPT BCC300 with probes positioned at multiple locations within the CPB circuit.Results39 patients were included. No significant differences in GME quantity in the arterial line were observed between the cannulation methods (count p=.444; volume p=967). Similarly, no significant differences were found based on venous reservoir volume (count p=.074; volume p=.166). Furthermore, no significant correlation was observed between GME in venous line entering the arterial line (count p-value=492; volume p-value=.750). The CPB circuit effectively removed 99.14% of GME, with no adverse events reported.ConclusionNo significant differences were found in arterial GME count or volume between cavoatrial and bicaval cannulation during CPB. These findings underscore the importance of the bypass circuit's air-handling capacity, as well as the role of modern oxygenators and arterial line filters in effectively minimizing the passage of GME. Trial Registration:ClinicalTrials.gov Identifier: NCT05820828URL: https://clinicaltrials.gov/ct2/show/NCT05820828.

Vacuum assisted and gravitational venous drainage in aortic valve surgery: A propensity-match study

INTRODUCTION

Vacuum assisted venous drainage (VAVD) is widely adopted in minimally invasive cardiac surgery. VAVD enables the advantage of using smaller cannulae in a reduced surgical field while allowing satisfactory drainage and pump flow. The production of gaseous micro-emboli is a recognized risk associated with VAVD, however no difference in clinical endpoints have been reported between patients operated on with gravity venous drainage (GVD) or with VAVD. Due to the paucity of data on selected surgical populations, we sought to evaluate the early outcomes of patients undergoing isolated aortic valve replacement using VAVD or GVD.

METHODS

Data on 521 patients between 09/2016 and 09/2022 were retrieved from our internal database. Patients were divided into two groups according to use VAVD or GVD. A propensity match analysis was performed to account for difference between the two groups.

RESULTS

The propensity match provided two well balanced cohorts with 129 patients each. A minimally invasive access was used in 97% of the cases in VAVD group vs 98% in GVD group (p = .68). Mean cardiopulmonary by-pass (CPB) time was 71 vs 73 min (p = .74), respectively. There was no difference in lactates peak (p = .19) and urine output during CPB (p = .74). We registered two in-hospital deaths in VAVD cohort (1.6%) vs. no mortality in GVD group (p = .5). Postoperative cerebral stroke occurred in 1 patient in GVD cohort vs. 0 in VAVD (p = 1). Severe postoperative acute kidney injury complicated the course in 16 patients in GVD group and in 5 patients who had VAVD (p = .012). VAVD was associated with a higher number of patients with elevated postoperative AST (p = .07) and Troponin I (p = .01) values.

CONCLUSIONS

The use of VAVD during isolated aortic valve replacement was not associated with increased risks of postoperative complications and in-hospital mortality with results that were at least similar to those registered in a matched cohort of patients operated on with GVD.

Development of a cannula device for gas fraction removal in surgical drains

The development of low-traumatic surgical drains aimed at maximum possible separation of blood and air, is an important trend in modern medicine. The objective of this work is to create an inexpensive, user-friendly and low-traumatic dynamic blood aspiration system (DBAS). The system allows effective separation of blood and air when drawing blood from a wound under vacuum conditions required for blood aspiration. The operating principle of the system is to separate liquid and gas fractions of the blood-air mixture by modifying the blood intake cannula. The effect is achieved by applying the principles of centrifugal forces of a rotating blood-air flow combined with Archimedes lift forces.

Vacuum-assisted venous drainage in adult cardiac surgery: a propensity-matched study

OBJECTIVES

Conventional cardiopulmonary bypass with gravity drainage leads inevitably to haemodilution. Vacuum-assisted venous drainage (VAVD) utilizes negative pressure in the venous reservoir, allowing active drainage with a shortened venous line to reduce the priming volume. The goal of this study was to analyse the efficacy and safety of VAVD.

METHODS

Data on 19 687 patients (18 681 with gravity drainage and 1006 with VAVD) who underwent cardiac operations between 1 January 2015 and 31 January 2018 were retrospectively collected from a single centre. Propensity matching identified 1002 matched patient pairs with VAVD and gravity drainage for comparison of blood product transfusion rate, major morbidities and in-hospital mortality rates.

RESULTS

The blood transfusion rate of the VAVD group was lower than that of the gravity drainage group (28.1% vs 35% for red blood cells, 13% vs 18% for fresh frozen plasma and 0.1% vs 1.8% for platelets; P = 0.0009, 0.0020 and <0.0001, respectively). The mean difference (95% confidence interval) between the groups for red blood cells, fresh frozen plasma and platelets was -6.9% (-11.0% to -2.8%), -5.0% (-8.1% to -1.8%) and -1.7% (-2.5% to -0.9%), respectively. No difference was observed regarding the major morbidities of cerebrovascular accidents, acute kidney injury, hepatic failure and perioperative myocardial infarction and the in-hospital deaths between the 2 groups.

CONCLUSIONS

VAVD was associated with a reduction in blood product transfusions, and an increase in the risk of major morbidities and in-hospital deaths of the VAVD group was not observed.

Impact of Vacuum-Assisted Venous Drainage on Forward Flow in Simulated Pediatric Cardiopulmonary Bypass Circuits Utilizing a Centrifugal Arterial Pump Head

Objective

To analyze the impact of vacuum-assisted venous drainage (VAVD) on arterial pump flow in a simulated pediatric cardiopulmonary bypass circuit utilizing a centrifugal pump (CP) with an external arterial filter.

Methods

The simulation circuit consisted of a Quadrox-I Pediatric oxygenator, a Rotaflow CP (Maquet Cardiopulmonary AG, Rastatt, Germany), and a custom pediatric tubing set primed with Lactated Ringer's solution and packed red blood cells. Venous line pressure, reservoir pressure, and arterial flow were measured with VAVD turned off to record baseline values. Four other conditions were tested with progressively higher vacuum pressures (-20, -40, -60, and -80 mmHg) applied to the baseline cardiotomy pressure. An arterial filter was placed into the circuit and arterial flow was measured with the purge line in both open and closed positions. These trials were repeated at set arterial flow rates of 1500, 2000, and 2500 mL/min.

Results

The use of progressively higher vacuum caused a reduction in effective arterial flow from 1490±0.00 to 590±0.00, from 2020±0.01 to 1220±0.00, and from 2490±0.0 to 1830±0.01 mL/min. Effective forward flow decreased with increased levels of VAVD.

Conclusion

The use of VAVD reduces arterial flow when a CP is used as the main arterial pump. The reduction in the forward arterial flow increases as the vacuum level increases. The loss of forward flow is further reduced when the arterial filter purge line is kept in the recommended open position.

An independent flow probe is essential to monitor pump flow during cardiopulmonary bypass.

Vascular air embolism: A silent hazard to patient safety

PURPOSE

To narratively review published information on prevention, detection, pathophysiology, and appropriate treatment of vascular air embolism (VAE).

MATERIALS AND METHODS

MEDLINE, SCOPUS, Cochrane Central Register and Google Scholar databases were searched for data published through October 2016. The Manufacturer and User Facility Device Experience (MAUDE) database was queried for "air embolism" reports (years 2011-2016).

RESULTS

VAE may be introduced through disruption in the integrity of the venous circulation that occurs during insertion, maintenance, or removal of intravenous or central venous catheters. VAE impacts pulmonary circulation, respiratory and cardiac function, systemic inflammation and coagulation, often with serious or fatal consequences. When VAE enters arterial circulation, air emboli affect cerebral blood flow and the central nervous system. New medical devices remove air from intravenous infusions. Early recognition and treatment reduce the clinical sequelae of VAE. An organized team approach to treatment including clinical simulation can facilitate preparedness for VAE. The MAUDE database included 416 injuries and 95 fatalities from VAE. Data from the American Society of Anesthesiologists Closed Claims Project showed 100% of claims for VAE resulted in a median payment of $325,000.

CONCLUSIONS

VAE is an important and underappreciated complication of surgery, anesthesia and medical procedures.

Hemolysis During Open-Heart Surgery With Vacuum-Assisted Venous Drainage at Different Negative Pressures in Pediatric Patients Weighing Less Than 10 kilograms

BACKGROUND

This study examined the degree of hemolysis during vacuum-assisted venous drainage at different negative pressures to identify an adequate negative pressure that provides effective venous drainage without significant hemolysis in open-heart surgery in children weighing less than 10 kg.

METHODS

Patients weighing less than 10 kg who underwent surgery for ventricular septal defect or atrial septal defect from 2011 to 2014 were enrolled. We used one of four negative pressures (20, 30, 40, or 60 mm Hg) for each patient. We measured haptoglobin, plasma hemoglobin, aspartate aminotransferase, and lactate dehydrogenase levels in the patients' blood three times perioperatively and determined the potential correlation between the change in each parameter with the level of negative pressure.

RESULTS

Forty-six patients were enrolled in this study (mean age: 7.1 ± 7.0 months, mean body weight: 6.1 ± 1.8 kg). There were no significant differences according to the degree of negative pressure with respect to patient age, body weight, cardiopulmonary bypass (CPB) time, aorta cross-clamping time, blood flow during CPB, or lowest body temperature. All parameters that we measured reflected progression of hemolysis during CPB; however, the degree of change in the parameters did not correlate with negative pressure.

CONCLUSION

In pediatric patients weighing less than 10 kg, the change in the degree of hemolysis did not differ with the amount of negative pressure. We may apply negative pressures up to 60 mm Hg without increasing the risk of hemolysis, with almost same the level of hemolysis using negative pressures of 20, 30, and 40 mm Hg for effective venous drainage and an ideal operative field during open-heart surgery.

Bubbles and bypass: an update

Bubbles in the bloodstream are not a normal condition -yet they remain a fact of cardiopulmonary bypass (CPB), having been extensively studied and documented since its inception some 50 years ago. While detectable levels of gaseous microemboli (GME) have decreased significantly in recent years and gross air embolism has been nearly eliminated due to increased awareness of etiologies and technological advances, methods of use of current perfusion systems continue to elicit concerns over how best to totally eliminate GME during open-heart procedures. A few studies have correlated adverse neurocognitive manifestations associated with excessive quantities of GME.

Newer techniques currently in vogue, such as vacuum-assisted venous drainage, low-prime perfusion circuits, and carbon dioxide flooding of the operative field, have, in some instances, exacerbated the problem of gas embolism or engendered secondary complications in the safe conduct of CPB. Doppler monitoring (circuit or transcranial) primarily remains a research tool to detect GME emanating from the circuit or passing into the patients’ cerebral vasculature. Newer developments not yet widely available, such as multiple-frequency harmonics, may finally provide a tool to distinguish particulate microemboli from GME and further delineate the clinical significance of GME.

Peripheral cardiopulmonary bypass with modified assisted venous drainage and transthoracic aortic crossclamp: optimal management for robotic mitral valve repair

The purpose of this study was to evaluate peripheral cardiopulmonary bypass (CPB) with modified assisted venous drainage (MAVD) and transthoracic aortic cross-clamping to maintain a bloodless surgical field, adequate myocardial protection, systemic flow and pressure during robotic surgical repair of the mitral valve. Peripheral CPB was established with a standard Duraflo®-coated closed circuit with femoral arterial and venous cannulation. An additional 17 Fr wire-bound cannula was inserted into the right internal jugular vein and drainage rates of 200-400 mL/min were regulated using a separate roller-head pump. A transthoracic aortic crossclamp with antegrade cardioplegia was used for myocardial protection. Mitral valve (MV) repair was then performed through two 1-cm ports for the robotic arms and a 4-cm intercostal incision for the camera and passing suture. From October 2001 to October 2002, 25 patients underwent robotic MV repair. Average surgical times include leaflet resection and repair, 20 min, and insertion of annuloplasty ring, 28 min; average perfusion times, crossclamp 88 min and total bypass time of 126 min. There were no incisional conversions, no reoperations for bleeding and no deaths, strokes or perioperative myocardial infarctions. Twenty-one (84%) patients were extubated in the operating room. Average LOS was 2.7 days with eight (32%) patients discharged home in less than 24 hours. In conclusion, peripheral CPB with gravity drainage of the lower body and MAVD of the upper body allow safe and effective support during robotically assisted minimally invasive MV repair. This approach may be applied to other forms of minimally invasive cardiac surgery that requires CPB.

The Great Britain and Ireland perspective: current perfusion safety issues, preparing for the future

The Great Britain and Ireland (GBI) recommendations for standards of monitoring and alarms during cardio-pulmonary bypass (CPB) came into force in January 2004. While perfusion departments in Great Britain and Ireland should now have a good baseline level of safety, it is important that department-specific safety is also considered. Patient safety is paramount, but safety within our speciality must also take into account the protection of the perfusionists’ health and the protection of their careers. These different aspects of safety are fundamentally interrelated.

This paper focuses on the importance of careful assessment, implementation and documentation when a new component or technique is being introduced to the CPB circuit, even when the aim is to increase safety.

Knowledge of the civil justice system and the trends in medical negligence claims are an integral part of perfusionist safety. Perfusion in Great Britain and Ireland is rightly striving for professional recognition from the Health Professions Council (HPC). As we raise the profile of perfusion, we educate more people about the importance of our role and level of responsibility within the cardiac operating team. This will increase the potential for medical negligence claims to be directed specifically at our speciality. All these issues are discussed in detail.

Miniature cardiopulmonary bypass — the Hammersmith experience

The decision to embark on a miniature cardiopulmonary bypass programme requires careful planning. The objective of this paper is to present our experience and initial findings for consideration by our multidisciplinary peers, who may wish to implement this technology at their own hospitals. The paper reviews the evolution of our programme over the first 150 clinical cases and our current position on the advantages and disadvantages of miniature cardiopulmonary bypass. Perfusion (2007) 22, 161—166.

Single, percutaneous, femoral venous cannulation for cardiopulmonary bypass

Percutaneous femoral venous cannulation for cardiopulmonary bypass has emerged as an indispensable technique in the management of cardiac surgical procedures requiring cardiopulmonary bypass. A review of cases at Brigham and Women's Hospital (Boston, MA, USA) relying solely on percutaneous femoral venous cannulation for venous return to the heart-lung machine demonstrated achievable blood flow and complexity of case-load. Operations performed in this manner include, but are not limited to, coronary artery bypass grafting (CABG), valve, CABG/valve, and aortic procedures. Minimally invasive procedures and re-operations comprise a portion of each group. Complications of cardiopulmonary bypass and site-related complications were considered. Percutaneous femoral venous cannulation is a safe method to provide most patients with adequate venous return to perform any cardiac surgery. Patients demanding greater flow than this method will provide, may require a second venous cannula at some time during cardiopulmonary bypass. Perfusion (2007) 22, 211—215.

Vacuum-assisted drainage in cardiopulmonary bypass: advantages and disadvantages

Systematic review of vacuum assisted drainage in cardiopulmonary bypass, demonstrating its advantages and disadvantages, by case reports and evidence about its effects on microcirculation. We conducted a systematic search on the period 1997-2012, in the databases PubMed, Medline, Lilacs and SciELO. Of the 70 selected articles, 26 were included in the review. Although the vacuum assisted drainage has significant potential for complications and requires appropriate technology and professionalism, prevailed in literature reviewed the concept that vacuum assisted drainage contributed in reducing the rate of transfusions, hemodilutions, better operative field, no significant increase in hemolysis, reduced complications surgical, use of lower prime and of smaller diameter cannulas.

Advances in Perfusion Techniques: Minimally Invasive Procedures

There is a growing demand from patients and referring physicians for minimally invasive cardiac surgery. Minimally invasive cardiac procedures are technically unique from conventional cardiac procedures and require a thorough understanding of the surgical, anesthetic, and perfusion strategies. Strategies include routine use of augmented venous drainage, alternative arterial and venous cannulation sites, and special cannulas designed for minimally invasive procedures. The following review describes the strategies and safety systems that should be considered when performing minimally invasive cardiac surgery.

Miniaturized cardiopulmonary bypass: the Hammersmith technique

Background

Conventional Cardiopulmonary Bypass (cCPB) is a trigger of systemic inflammatory reactions, hemodilution, coagulopathy, and organ failure. Miniaturised Cardiopulmonary Bypass (mCPB) has the potential to reduce these deleterious effects. Here, we describe our standardised ‘Hammersmith’ mCPB technique, used in all types of adult cardiac operations including major aortic surgery.

Methods

The use of mCPB remains limited by the diversity of technologies which range from extremely complex, micro systems to ones very similar to cCPB. Our approach is designed around the principle of balancing the benefits of miniaturisation; reducing foreign surface area while maintaining patient safety.

Results

From January 2010 to March 2011, a single surgeon performed 184 consecutive operations (Euro score Logistic 8.4+/-9.9): 61 aortic valve replacements, 78 CABGs, 25 aortic valve replacement and CABG and 17 other procedures (major aortic surgery, re-do operations or double/triple valve replacements).

Our clinical experience suggests that:

i. Venous drainage is optimally maintained using kinetic energy.

ii. Venous collapse pressure depends on the patient’s anatomy and cannula size, but most importantly on the negative pressure generated by venous drainage.

iii. The patient-prime interaction is optimised with antegrade and retrograde autologous priming, which mixes the blood and prime away from the tissues and results in a reduced oncotic destabilization.

iv. mCPB is a safe and reproducible technique

Conclusion

The Hammersmith mCPB is a “next generation” system which uses standard commercially available components. It aims to maintain safety margin and the benefit of miniaturised system whilst reducing the human factor demands.

Brain emboli distribution and differentiation during cardiopulmonary bypass

OBJECTIVE

Cardiopulmonary bypass (CPB) is a lifesaving practice in cardiac surgery, but its use frequently is associated with cerebral injury and neurocognitive dysfunctions. Despite the involvement of numerous factors, microembolism occurring during CPB seems to be one of the main mechanisms leading to such alterations. The aim of the present study was to characterize the occurrence of cerebral microembolism with reference to microembolic amount, nature, and distribution in different combinations of cardiac procedures and CPB on the microembolic load.

DESIGN

A retrospective observational clinical study.

SETTING

A single-center regional hospital.

PARTICIPANTS

Fifty-five patients undergoing elective cardiac surgery with CPB.

INTERVENTIONS

Bilateral detection of the patients' middle cerebral arteries using a multifrequency transcranial Doppler.

MEASUREMENTS AND MAIN RESULTS

Patients were divided into 3 groups depending on the CPB circuit used (open, open with vacuum, or closed). There was a significant difference between the number of solid and gaseous microemboli (p<0.001), with the solid lower than the gaseous ones. The number of solid microemboli was affected by group (p< 0.05), CPB phase (p<0.001), and laterality (p<0.01). The number of gaseous microemboli was affected only by group (p<0.05) and CPB phase (p<0.001). Generally, the length of CPB phase did not affect the number of microemboli.

CONCLUSIONS

Surgical procedures combined with CPB circuits, but not the CPB phase length, affected the occurrence, nature, and laterality of microemboli.

Excessive negative venous line pressures and increased arterial air bubble counts during miniaturized cardiopulmonary bypass: an experimental study comparing miniaturized with conventional perfusion systems

OBJECTIVES

Miniaturized cardiopulmonary bypass (MCPB) is increasingly used in cardiac surgery, because it can lower clinically significant complications such as systemic inflammatory response, haemolysis and high transfusion requirements. A limitation of MCPB is the risk of excessive negative pressure in the venous line during volume depletion, probably leading to gaseous microembolism.

METHODS

In an experimental study with 24 pigs, we compared conventional open cardiopulmonary bypass (CCPB group, n = 11) with MCPB (n = 13). The same pump and identical tubing materials were used in both groups. Primary endpoints were pressure values in the venous line and the right atrium as well as the amount of air bubbles >500 µm. Secondary endpoints were biochemical parameters of systemic inflammatory response, ischaemia, haemodilution and haemolysis.

RESULTS

Nearly 20% of venous pressure values were below -150 mmHg and approximately 10% of the right atrial pressure values were below -100 mmHg in the MCPB group, during the experiment. No such low values were observed in the CCPB group. In addition, the number of large arterial air bubbles was higher in the MCPB group compared with the CCPB group (mean ± standard deviation [SD]: 13 444 ± 5709 vs 0.9 ± 0.6, respectively; P < 0.001). Bubble volume was also significantly larger during MCPB compared with CCPB (mean ± SD: 1522 ± 654 vs 4.1 ± 2.5 µl, respectively; P < 0.001). Blood levels of interleukin-6, free haemoglobin and creatine kinase were significantly higher in the CCPB group compared with the MCPB group.

CONCLUSIONS

Despite the benefits of MCPB regarding systemic inflammatory response and haemolysis, this technique is associated with excessive negative venous line pressures and a significant increase in the number and volume of arterial air bubbles compared with CCPB. Mini-perfusion systems and the management of MCPB require further refinements to avoid such adverse effects.

Can minimized cardiopulmonary bypass systems be safer?

Although a growing body of evidence indicates superiority of minimized cardiopulmonary bypass (mCPB) systems over conventional CPB systems, limited venous return can result in severe fluctuations of venous line pressure which can result in gaseous emboli. In this study, we investigated the influence of sub-atmospheric pressures and volume buffer capacity added to the venous line on the generation of gaseous emboli in the mCPB circuit.

Two different mCPB systems (MEC - Maquet, n=7 and ECC.O - Sorin, n=8) and a conventional closed cardiopulmonary bypass (cCPB) system (n=12) were clinically evaluated. In the search for a way to increase volume buffer capacity of mCPB systems, we additionally evaluated the ‘Better Bladder’ (BB) in a mock circulation by simulating, repeatedly, decreased venous return while measuring pressure and gaseous embolic activity.

Arterial gaseous emboli activity during clinical perfusion with a cCPB system was the lowest in comparison to the mCPB systems (312±465 versus 311±421 with MEC and 1,966±1,782 with ECC.O, counts per 10 minute time interval, respectively; p=0.03). The average volume per bubble in the arterial line was the highest in cases with cCPB (12.5±8.3 nL versus 8.0±4.2 nL with MEC and 4.6±4.8 nL with ECC.O; p=0.04 for both). Significant cross-correlation was obtained at various time offsets from 0 to +35 s between sub-atmospheric pressure in the venous line and gaseous emboli activity in both the venous and arterial lines. The in vitro data showed that incorporation of the BB dampens fluctuations of venous line pressure by approximately 30% and decreases gaseous emboli by up to 85%.

In conclusion, fluctuations of sub-atmospheric venous line pressure during kinetic-assisted drainage are related to gaseous emboli. Volume buffer capacity added to the venous line can effectively dampen pressure fluctuations resulting from abrupt changes in venous return and, therefore, can help to increase the safety of minimized cardiopulmonary bypass by reducing gaseous microemboli formation resulting from degassing.

Generation, detection and prevention of gaseous microemboli during cardiopulmonary bypass procedure

Neuropsychological injury after cardiopulmonary bypass (CPB) is one of the most serious and costly complications arising from the procedure. Gaseous microemboli (GME) have long been implicated as one of the principal causes. There are two major sources of GME: surgical and manual manipulation of the heart and arteries; and the components of the extracorporeal circuit, including the type of pump, different perfusion modes, the design of the oxygenator and reservoir, and the use of vacuum assisted venous drainage (VAVD), all of which have a great impact on the delivery of existing GME to the patients. Transcranial cranial Doppler (TCD) has been used for more than two decades to assess and monitor the quality of extracorporeal perfusion with regard to the blood flow velocity of the middle cerebral arteries (MCA) and emboli detection, contributing to the achievement of better perfusion results. The Emboli Detection and Classification (EDAC) Quantifier has been able to detect and track microemboli in CPB circuits up to 1,000 microemboli per second at flow rates ranging from 0.2 L/min to 6.0 L/min. The deleterious effects of GME are multiple, including damage to the cerebral vascular endothelium, disruption of the blood-brain barrier, complement activation, leukocyte aggregation, increased platelet adherence, and fibrin deposition in the micro-vasculature. Improvements in perfusion equipment and in perfusion and surgical techniques have led to a dramatic reduction in the occurrence of GME during cardiac surgery. Although the clinical relevance of cerebral air embolization in causing neurological damage is unclear, every single person involved in perfusion and surgical technology should be aware of the risk of embolization and strictly regulate clinical behavior. Related research should also be done to improve the design of circuit components and clinical practice with a view to eliminating air bubbles during CPB procedure.

Ferraris VA, Brown JR, Despotis GJ, Hammon JW, Reece TB, Saha SP, Song HK, Clough ER, Shore-Lesserson LJ, Goodnough LT, Mazer CD, Shander A, Stafford-Smith M, Waters J, Baker RA, Dickinson TA, FitzGerald DJ, Likosky DS, Shann KG. 2011 update to the Society of Thoracic Surgeons and the Society of Cardiovascular Anesthesiologists blood conservation clinical practice guidelines

BACKGROUND

Practice guidelines reflect published literature. Because of the ever changing literature base, it is necessary to update and revise guideline recommendations from time to time. The Society of Thoracic Surgeons recommends review and possible update of previously published guidelines at least every three years. This summary is an update of the blood conservation guideline published in 2007.

METHODS

The search methods used in the current version differ compared to the previously published guideline. Literature searches were conducted using standardized MeSH terms from the National Library of Medicine PUBMED database list of search terms. The following terms comprised the standard baseline search terms for all topics and were connected with the logical 'OR' connector--Extracorporeal circulation (MeSH number E04.292), cardiovascular surgical procedures (MeSH number E04.100), and vascular diseases (MeSH number C14.907). Use of these broad search terms allowed specific topics to be added to the search with the logical 'AND' connector.

RESULTS

In this 2011 guideline update, areas of major revision include: 1) management of dual anti-platelet therapy before operation, 2) use of drugs that augment red blood cell volume or limit blood loss, 3) use of blood derivatives including fresh frozen plasma, Factor XIII, leukoreduced red blood cells, platelet plasmapheresis, recombinant Factor VII, antithrombin III, and Factor IX concentrates, 4) changes in management of blood salvage, 5) use of minimally invasive procedures to limit perioperative bleeding and blood transfusion, 6) recommendations for blood conservation related to extracorporeal membrane oxygenation and cardiopulmonary perfusion, 7) use of topical hemostatic agents, and 8) new insights into the value of team interventions in blood management.

CONCLUSIONS

Much has changed since the previously published 2007 STS blood management guidelines and this document contains new and revised recommendations.

Pre-clinical laboratory evaluation of the new 'AF' arterial line filter range

INTRODUCTION

The presence of emboli was recognised relatively early in the history of open heart surgery. The emboli produced during cardiopulmonary bypass have the predisposition to distribute into, and ultimately obstruct, microvessels of all tissues. The Sorin Group has recently developed a new range of arterial line filters. Before the Sorin AF range of filters was released for pre-launch clinical trials, our group performed in vitro laboratory testing of the AF range against a selection of commercially available filters on the global market.

RESULTS

The Sorin AF620 and AF640 demonstrate both the smallest prime volume and smallest surface contact area (92ml and 290 cm(2), respectively).The results of the GME Handling Efficiency experiments ranged by 39.6%, from 95.9% to 56.3%. In terms of an air bolus handling, the results of the Limit Bolus experiment ranged by 97 ml, from 147.5 ml down to 50 ml. The pressure drop across all the filters was measured under steady state experimental conditions. All of the above investigations were considered against surface area and prime volume.

CONCLUSION

It is clear from the results that some commercially available arterial line filters perform better than others, not only in overall performance, but also with regard to individual characteristics. Evaluating arterial line filters for hospital-specific use has to balance pressure drop, surface area, micro air handling, prime volume and gross air handling; all points need to be considered. In the AF620 and AF640, Sorin boast that they are the two smallest prime and smallest surface area filters commercially available on the global market. The Sorin AF filter range performs well in all of the areas we investigated and will be a competitive option for centres, irrespective of which characteristics they use to evaluate and select their arterial line filter.

In vitro and in vivo evaluation of Dideco’s paediatric cardiopulmonary circuit for neonates weighing less than five kilograms

The neonate cardiopulmonary bypass (CPB) circuit, including a KIDS D100 oxygenator (The Sorin Group, Mirandola, Italy) and a D130 arterial filter (The Sorin Group), was evaluated in vitro with respect to the removal of free micro gas bubbles. No gas bubbles > 40µm were measured after the arterial filter D130 upon manual introduction of 10 ml of air into the venous line or during the use of vacuum-assisted venous drainage (VAVD). The D130 arterial filter removed 88 % of gas bubbles < 40 µm during manual introduction of air into the venous line; however, only 50 % of gas bubbles < 40 µm were removed during the use of VAVD.

The same CPB circuit was evaluated in vivo to compare with another CPB circuit, including a D901 oxygenator (The Sorin Group) and arterial filter D736 (The Sorin Group), in 155 neonates weighing ≤5 kg. The D100 circuit required significantly less priming volume than the D901 circuit. Postoperative haemoglobin was significantly higher, artificial ventilation time was significantly shorter and postoperative bleeding was significantly less in the D100 group. This neonate CPB circuit effectively removed the gas bubbles and required up to 37% less priming volume and, thus, decreased the need for blood transfusion.

An in vitro comparison of the ability of three commonly used pediatric cardiopulmonary bypass circuits to filter gaseous microemboli

Background: The purpose of this study was to compare the ability of three commonly used pediatric cardiopulmonary bypass (CPB) circuits to filter gaseous microemboli (GME) in an in vitro model. Methods: Devices were tested at different levels of two specific independent variables: volume of air injected (1, 3, 5ml) and percentage of each oxygenator’s rated flow (50%, 75%, 100%, 125%). The air-handling ability of each CPB circuit was determined by the Emboli Detection and Classification Quantifier (Luna Innovations Inc., Roanoke,VA). Results: At all tested conditions, the FX-05 allowed a higher percentage of GME when compared to either one or both of the other two CPB circuits. When comparing oxygenators at similar absolute flow rates, the KIDS D100/D130 CPB circuit performed worse compared to the other two CPB circuits. C onclusions: The combination of the Baby RX-05 oxygenator and Capiox AF02 arterial line filter provides the highest level of protection from air emboli in an in vitro investigation.

Influence of venous reservoir level on microbubbles in cardiopulmonary bypass

Patients undergoing open-heart surgery may, post-operatively, suffer from neurological disorders due to microbubbles created during extracorporeal circulation. Venous air is not completely removed in open hard-shell venous reservoirs. We, therefore, investigated the relationship between venous reservoir blood level and the amount of microbubbles in different commercially available reservoirs for comparison and determination of safe level. An in vitro flow loop with a heart-lung machine was used to compare three different reservoirs (Maquet, Sorin and Medtronic) at different levels. Microbubbles were measured after the reservoir and after the arterial filter with a GAMPT BCC200 detector. Microbubble count and volume were significantly higher with decreasing reservoir level (p = 0.014), but not as much as earlier studies have shown. Reducing the level from 1000 ml to 250 ml resulted in a 12.4% increase in bubble volume after the reservoir and 40.2% after the arterial filter. There was an almost linear trend towards more bubble volume with decreasing reservoir level (R2 = 0.98-0.83). There was a significant difference in microbubbles between the 3 tested reservoirs, up to 32.6%, p < 0.001 measured after the reservoir. Bubble volume from the Sorin reservoir was markedly lower after the arterial filter than from the Medtronic and Maquet reservoirs (up to 60 times p < 0.001). A lower reservoir level results in a moderate rise in microbubbles passing the reservoir. The minimum levels recommended by the manufacturers are safe. There was a significant difference in bubbles between the different reservoirs, especially after the arterial filter.

Beneficial effects of modern perfusion concepts in aortic valve and aortic root surgery

Minimized perfusion circuits (MPC) were found to reduce side effects of standard extracorporeal circulation (ECC). We evaluated the safety and efficacy of the ROCsafe™ MPC for aortic valve and aortic root surgery. One hundred and seventy patients were randomized for surgery using either MPC [n = 85, 30 female/55 male, mean age: 69.8 ± 11.8 years; aortic valve replacement (AVR): n = 40; AVR + coronary artery bypass graft (CABG): n = 31; David operation: n = 3; aortic root replacement (ARR): n = 11] or ECC [n = 85, 29 female/56 male, mean age: 67.7 ± 9.5 years; AVR: n = 39; AVR+CABG: n = 35, David operation: n = 2; ARR: n = 9]. Neurological status, length of ICU stay, C-reactive protein (CRP), blood count, transfusion requirements and bleeding volume were analyzed. The MPC system provided ultrasound-controlled de-airing. A small roller pump and a flexible reservoir were used for left ventricular venting. As a control, we used a standard ECC with cardiotomy suction and hard-shell reservoir. Cross-clamp time (MPC: 76.5 ± 29.5; ECC: 79.0 ± 34.0 min) and bypass time (MPC: 103.0 ± 37.9; ECC: 106.9 ± 44.9 min) were comparable between groups. Transfusion requirements (red blood cells: MPC: 1.5 ± 1.5 vs. ECC: 2.2 ± 2.1 units [p = 0.05], frozen plasma: MPC: 1.2 ± 1.8 vs. ECC: 1.9 ± 2.4 units [p = 0.03]), postoperative bleeding (MPC: 521 ± 283 vs. ECC: 615 ± 326 ml/24 h, p = 0.09) were lower using MPC. ICU stay was shorter with MPC (1.6 ± 1.6 days) compared to ECC (2.4 ± 2.8 days, p = 0.001). One stroke occurred in each group. The ROCsafe™ MPC provides safe circulatory support for a wide range of aortic valve surgeries. Transfusion requirements, postoperative bleeding and length of ICU stay were markedly reduced compared to standard extracorporeal perfusion.

Detection and Elimination of Microemboli Related to Cardiopulmonary Bypass

Background— Neurobehavioral impairment is a common complication of coronary bypass surgery. Cerebral microemboli during cardiopulmonary bypass (CPB) are a principal mechanism of cognitive injury. The aim of this work was to study the occurrence of cerebral embolism during CPB and to evaluate the effectiveness of evidence-based CPB circuit component and process changes on the exposure of the patient to emboli.

Methods and Results— M-Mode Doppler was used to detect emboli in the inflow and outflow of cardiopulmonary circuit and in the right and left middle cerebral arteries. Doppler signals were merged into a single display to allow real-time associations between discrete clinical techniques and emboli detection. One hundred sixty-nine isolated coronary artery bypass grafting (CABG) patients were studied between 2002 and 2008. There was no statistical difference in median microemboli detected in the inflow of the CPB circuit, (Phase I, 931; Phase II, 1214; Phase III, 1253; Phase IV, 1125; F [3,158]=0.8, P =0.96). Significant changes occurred in median microemboli detected in the outflow of the CPB circuit across phases, (Phase I, 702; Phase II, 572; Phase III, 596; Phase IV, 85; F [3,157]=13.1, P <0.001). Significant changes also occurred in median microemboli detected in the brain across phases, (Phase I, 604; Phase II, 429; Phase III, 407; Phase IV, 138; F [3,153]=14.4, P <0.001). Changes in the cardiopulmonary bypass circuit were associated with an 87.9% (702 versus 85) reduction in median microemboli in the outflow of the CPB circuit ( P <0.001), and a 77.2% (604 versus 146) reduction in microemboli in the brain ( P <0.001).

Conclusions— Changes in CPB techniques and circuit components, including filter size and type of pump, resulted in a reduction in more than 75% of cerebral microemboli.

Microbubbles detection during cardiopulmonary bypass with transoesophageal echocardiography: a case report

INTRODUCTION

Microembolic signals are usually detected with transcranial doppler during cardiac surgery.This report focuses on suggesting the transesophageal echocardiography as a different diagnostic approach to detect microemboli during cardiopulmonary bypass.

CASE PRESENTATION

A 58 year old male patient, caucasian race, was operated on video assisted minimally invasive mitral valve repair using right minithoracotomy approach. His past medical history included an uncontrolled hypertension, dyslipidemia, insulin dependent diabetes mellitus, carotid arteries stenosis. The extracorporeal circulation was performed with femoral-femoral artery and venous approach. Negative pressure for vacuum assist venous drainage was applied in order to facilitate venous blood return. The patient had a brain monitoring with bilateral transcranial doppler of middle cerebral arteries and a double channels electroencephalogram. A three dimensional transesophageal echocardiography to evaluate the mitral valve repair was performed.During the cardiopulmonary bypass a significant microembolic activity was detected in the middle cerebral arteries spectrum velocities due to gas embolism from venous return. Simultaneous recording of microbubbles was also observed on the descending thoracic aorta transesophageal echo views.

CONCLUSION

During the aortic cross-clamping time the transesophageal echocardiography can be useful as an alternative method to assess the amount of gas embolism coming from cardiopulmonary bypass. These informations can promote immediate interaction between perfusionist, surgeon and anesthesiologist to perform adequate manoeuvres in order to reduce the microembolism during extracorporeal circulation.

Aortic surgery using total miniaturized cardiopulmonary bypass

PURPOSE

Few centers have attempted aortic surgery using miniaturized cardiopulmonary bypass (MCPB) systems due to concerns of air handling. The extra corporeal circuit optimized (ECCO) total MCPB system uses a venous air removal device and a parallel soft-shell reservoir that allows for venting of the heart. At our institution, total MCPB is used for all coronary artery bypass graft patients. Our objective was to assess the suitability of the ECCO total MCPB system during aortic surgery.

DESCRIPTION

Fifty consecutive and unselected aortic procedures using the ECCO system were undertaken. Surgical feasibility, air removal ability, and blood transfusion requirements were audited to determine the efficacy of this technique.

EVALUATION

The bypass time was 81.6 +/- 28.0 minutes and the ischemic time was 56.7 +/- 18.9 minutes. Total MCPB handled 1,910 +/- 404 mL of vented blood with 96 venous air removal device activations noted. The blood product transfusion rate was 12%, which was below the surgical transfusion rate for our unit. There were no complications.

CONCLUSIONS

Aortic surgery can be undertaken safely and effectively using the ECCO total MCPB system.

Surgical, anesthetic, perfusion-related advances in minimal access surgery

As we enter the fifth decade in cardiac surgery, traditionally cardiac surgery has been performed using a median sternotomy with cardiopulmonary bypass providing great access to the heart and all the surrounding structures. During the last decade, there has been a paradigm shift in the methods by which surgery has been performed. The invasiveness of many procedures has been dramatically reduced, with significantly superior outcomes, as evidenced by improved survival, fewer complications, and quicker return to functional health and productive life. This resulted in significant interest and excitement in adopting less invasive techniques in cardiac surgery. Unfortunately, this was an unrealistic expectation due to the limitations that existed in cardiac surgical techniques and conventional endoscopic instruments, cardiac anesthesia, and cardiopulmonary bypass techniques. In this article, the advances in minimally invasive surgical, cardiac anesthesia, and cardiopulmonary bypass techniques in the evolution of minimal access cardiac surgery are summarized.

Microemboli detection on extracorporeal bypass circuitsa

Numerous authors have associated gaseous microembolization with adverse cerebral outcomes during cardiopulmonary bypass (CPB). The introduction to this review provides background on the connection between microemboli and adverse cerebral outcomes. This connection is often difficult to quantify, as outcomes depend on a number of factors, including the size of the bubble, where it passes through the patient, patient co-morbidities and other factors. Nonetheless, numerous studies have shown statistically significant differences in the mean number of cerebral emboli detected in patients that stroked and those that did not, as well as for patients with major cardiac complications and patients with a longer length of hospital stay. Our introduction is followed by case reports and laboratory studies showing how monitoring for gaseous microemboli (GME) can be used to reduce the embolic load delivered to the patient through the bypass circuit. These methods include improved qualification of bypass circuit design prior to surgery, modification of priming procedures to reduce air in the circuit at the start of surgery, new methods for injecting drugs into the circuit during surgery, and better detection of removal of sources of air during surgery. The review concludes with background on the ultrasonic detection of GME, comparing through-transmission gross air detectors and Doppler ultrasound technology with fixed-beam ultrasonic imaging of emboli, a new ultrasonic technique that images moving emboli in the blood using a single ultrasound transducer element in a fixed position. This overview is meant to shed light on why different ultrasonic detection technologies report widely varying counts and emboli loads, and why fixed-beam ultrasonic imaging represents an improvement in the ability to monitor, measure and quantitate embolic load during CPB.

A New Minimized Perfusion Circuit Provides Highly Effective Ultrasound Controlled Deairing

Minimized perfusion circuits (MPCs) have been criticized for insufficient air elimination. The deairing capabilities of a new MPC, including an ultrasound controlled deairing unit, were compared to a standard extracorporeal circuit (ECC) in a laboratory setup. During blood flow of 4.0l/min, we injected 30-cc air over a period of 30 s into the venous line of both systems (n = 10 measurements/15-min intervals). Air was detected during the first 2 min post injection using a dual-channel ultrasound bubble counter. Venous air bubble measurements were made after the MPC bubble trap and the ECC hard-shell reservoir, respectively. Arterial air bubble data were obtained after the arterial filters (40 microm). Venous bubble count was significantly (P < 0.01) reduced in the MPC group (5-250 microm, 681 +/- 177; >40 microm, 288 +/- 92) compared with the ECC group (5-250 microm, 19 272 +/- 682; >40 microm, 7642 +/- 520). After the arterial filter, minimal numbers of air bubbles (5-250 microm, 172 +/- 59; >40 microm, 0) could be detected in the MPC group, but large amounts of air (5-250 microm, 16 194 +/- 1072; >40 microm, 3732 +/- 997) were measured in the ECC group. The air elimination of the modern MPC is superior to conventional ECC, which may result in a reduction of neurological complications.

Reduction in Air Bubble Size Using Perfluorocarbons During Cardiopulmonary Bypass in the Rat

BACKGROUND

Perfluorocarbon (PFC) emulsions are artificial oxygen-carrying compounds with a high solubility for gases that have experimentally been shown to ameliorate cerebral air embolism. Cerebral air embolism has been associated with adverse cerebral outcomes after cardiac surgery using cardiopulmonary bypass (CPB). We designed this study to test whether PFC emulsions could reduce the volume of bubbles within the CPB circuit.

METHODS

Male Sprague-Dawley rats undergoing 60 min of normothermic nonpulsatile CPB were randomized to one of the three groups. The PFC group (n = 10) received 60% O(2)/36% N(2)/4% CO(2) via the membrane oxygenator and 2.7 g/kg (4.5 mL/kg) of PFC into the venous reservoir; the control group (n = 10) received the same gas mixture and 4.5 mL/kg of saline; the N(2)O group (n = 6) was exposed to 36% N(2)O/60% O(2)/4% CO(2) and received 4.5 mL/kg of saline. After 10 min and 35 min of CPB, 400 microL of air was injected into a bubble chamber in the CPB circuit. After 20 min, the bubble was removed for volumetric analysis.

RESULTS

Compared with baseline, the bubble decreased 13% +/- 5% in size in the PFC group and increased 46% +/- 9% in the nitrous oxide group, both of these changes significantly different from the control group (P < 0.0001).

CONCLUSION

The results suggest that PFC administration may be useful in reducing the volume of gaseous bubbles present during CPB.

Pediatric cardiopulmonary bypass devices: trends in device use for cardiopulmonary bypass and postcardiotomy support

Cardiopulmonary bypass (CPB) devices and techniques have continuously evolved. We have conducted surveys that chronicle the changes in CPB devices and techniques used at North American pediatric cardiac surgery centers since 1989. The aim of this article is to describe trends in cardiopulmonary bypass device use during cardiac surgery and changes in the devices used for extracorporeal life support (ECLS) following cardiac surgery for pediatric patients. The diffusion of innovation in pediatric cardiovascular surgery has not been solely driven by the availability of scientific evidence to support change but rather it has often been related to other factors that influence clinicians willingness to change including; tradition, ease of use, and cost related pressures. The current CPB systems used for cardiac surgery are more homogenous than in previous years. Most centers use a heparin coated or modified surface system comprised of a "hard shell" open venous reservoir, a roller pump, a hollow fiber membrane oxygenator, and arterial line filter. ECLS systems comprised of hollow fiber oxygenators and centrifugal pumps for are gradually replacing the classical ECLS circuit, servo regulated roller pumps and silicone rubber membranes. Nearly 40% of centers use these alternate components in their ECLS systems. Costs, utility, safety and measurable benefit to the patient should guide decisions related to device selection.

Embolic Activity Subsequent to Injection of the Internal Mammary Artery with Papaverine Hydrochloride

BACKGROUND

Neurologic injury is a rare yet devastating outcome of coronary artery bypass grafting surgery. Mechanisms producing both focal and global neurologic injuries include embolization, cerebral hypoperfusion, and hypotension. In this present study, we report an association between variations in the treatment of the internal mammary artery with the detection of cerebral embolic signals.

METHODS

An intensive intraoperative neurologic and physiologic monitoring approach was implemented to associate discrete processes of clinical care with the concurrent detection of cerebral embolic signals, cerebral hypoperfusion, and hypotension. The method of treating the left internal mammary artery was tracked among 68 patients undergoing isolated coronary artery bypass grafting. Cerebral embolic signals were counted within 3 minutes of the treatment of the left internal mammary artery.

RESULTS

Among a series of 68 patients undergoing isolated coronary artery bypass grafting, 22 were not treated with papaverine. Of those treated, 12 received injection intraluminally and 28 had a topical application. Embolic signals were noted concurrently among 7 patients receiving injection of papaverine. No embolic signals were noted among patients who were treated topically.

CONCLUSIONS

We report an association between the injection of papaverine hydrochloride and cerebral embolic signals. Our findings suggest that adoption of topical applications of papaverine hydrochloride may offer opportunities to reduce a portion of cerebral embolic signals in the setting of coronary artery bypass grafting.

The influence of xenon, nitrous oxide and nitrogen on gas bubble expansion during cardiopulmonary bypass

BACKGROUND AND OBJECTIVE

Xenon may have favourable applications in the setting of cardiac surgery. Its advantages include a desirable haemodynamic profile as well as potential cardiac and neuroprotective properties. However, its low solubility may lead to enhanced diffusion into enclosed gas spaces. The purpose of this study was to compare the effects of xenon (Xe), nitrous oxide (N2O) and nitrogen (N2) on gas bubble size during cardiopulmonary bypass (CPB).

METHODS

Rats were randomized to receive 70% Xe, 26% oxygen (O2), 4% carbon dioxide (CO2) (xenon group); 70% N2O, 26% O2, 4% CO2 (nitrous oxide group) or 70% N2, 26% O2, 4% CO2 (nitrogen group) during 90 min of normothermic CPB. Small gas bubbles (300-500 microL; n = 12 per group) were injected into a bubble chamber on the venous side of the bypass circuit. After 10 min of equilibration, they were removed for volumetric analysis.

RESULTS

The increase in bubble size was 2 +/- 2% with nitrogen, 17 +/- 6% with xenon (P = 0.0192 vs. nitrogen) and 63 +/- 23% with nitrous oxide (P = 0.0001 vs. nitrogen). The nitrous oxide group had significantly increased bubble size compared to the xenon group (P = 0.0001).

CONCLUSIONS

During CPB, xenon anaesthesia produced a small increase in gas bubble size compared to nitrogen. Nitrous oxide resulted in significantly larger bubbles compared to both nitrogen and xenon.

Vacuum-Assisted Venous Drainage during Fetal Cardiopulmonary Bypass

We investigated a miniature magnetically levitated centrifugal blood pump intended to deliver 0.3-1.5 l/min of support to neonates and infants. The back clearance gap between the housing and large volume of the rotor, where the suspension and motor bearings are located, forms a continuous leakage flow path. Within the gap, flow demonstrates a very complex three-dimensional structure: the fluid adjacent to the rotating disk tends to accelerate by centrifugal force to flow radially outwards toward the outlet of the impeller against an unfavorable pressure gradient, which in turn forces blood to return along the stationary housing surfaces. Consequently, one or multiple vortices may be generated in the gap to block blood flow and cause the formation of a retrograde and antegrade leakage flow phenomenon at the gap outlet using an optimization process including extensive computational fluid dynamics (CFD) analysis of impeller refinements, we found that secondary blades located along the back or extended to the side surfaces of the rotor have the capacity to reduce and eliminate the retrograde flow in the back clearance gap. Flow visualization confirmed the CFD-predicted flow patterns. This work demonstrates the utility of CFD-based design optimization to optimize the fluid path of a miniature centrifugal pump.

Venous drainage method for cardiopulmonary bypass in single-access minimally invasive cardiac surgery: siphon and vacuum-assisted drainage

Vacuum-assisted venous drainage (VAVD) can facilitate venous drainage in single-access minimally invasive cardiac surgery (SAMICS). We retrospectively examined the use of VAVD in SAMICS in our hospital for this report. VAVD has been performed according to a VAVD protocol since 2000. Data from the 110 patients who underwent SAMICS in our institute from January 2000 to June 2002 were reviewed retrospectively. The total negative pressure was maintained at no greater than -90 mmHg. Indications for use of VAVD (protocol) were: insufficient venous return by siphon drainage alone, persistent elevation of the central venous pressure (CVP), and, insufficient venous drainage in the operative field. Of 110 patients, 97 (88.2%) underwent VAVD. The body surface area was significantly smaller in the group that did not require VAVD (the non-VAVD group) than in the group that did (VAVD group) (VAVD group versus non-VAVD group: 1.586 +/- 0.175 versus 1.408 +/- 0.153 m(2), P < 0.001). Other factors such as cardiopulmonary bypass time, aortic cross-clamp time, postoperative maximum lactate dehydrogenase, postoperative maximum creatinine, postoperative maximum blood urea nitrogen were similar in the two groups. VAVD is necessary in SAMICS except for small patients. A VAVD total negative pressure of -90 mmHg did not hinder operative procedures or cause clinical problems.

The dynamic air bubble trap reduces cerebral microembolism during cardiopulmonary bypass

OBJECTIVE

Neuropsychologic disorders are common after coronary artery bypass operations. Air microbubbles are identified as a contributing factor. A dynamic bubble trap might reduce the number of gaseous microemboli.

METHODS

A total of 50 patients undergoing coronary artery bypass operation were recruited for this study. In 26 patients a dynamic bubble trap was placed between the arterial filter and the aortic cannula (group 1), and in 24 patients a placebo dynamic bubble trap was used (group 2). The number of high-intensity transient signals within the proximal middle cerebral artery was continuously measured on both sides during bypass, which was separated into 4 periods: phase 1, start of bypass until aortic clamping; phase 2, aortic clamping until rewarming; phase 3, rewarming until clamp removal; and phase 4, clamp removal until end of bypass. S100 beta values were measured before, immediately after, and 6 and 48 hours after the operation and before hospital discharge.

RESULTS

The bubble elimination rate during bypass was 77% in group 1 and 28% in group 2 (P <.0001). The number of high-intensity signals was lower in group 1 during phase 1 (5.8 +/- 7.3 vs 16 +/- 15.4, P <.05 vs group 2) and phase 2 (6.9 +/- 7.3 vs 24.2 +/- 27.3, P <.05 vs group 2) but not during phases 3 and 4. Serum S100 beta values were equally increased in both groups immediately after the operation. Group 2 patients had higher S100 beta values 6 hours after the operation and significantly higher S100 beta values 48 hours after the operation (0.06 +/- 0.14 vs 0.18 +/- 0.24, P =.0133 vs group 2). Age and S100 beta values were correlated in group 2 but not in group 1.

CONCLUSION

Gaseous microemboli can be removed with a dynamic bubble trap. Subclinical cerebral injury detectable by increases of S100 beta disappears earlier after surgical intervention.

Prebypass filtration of cardiopulmonary bypass circuits: an outdated technique?

Filtration of cardiopulmonary bypass (CPB) priming fluid before connection of the circuit to the patient was first accomplished by arterial line filtration. When dedicated prebypass filters (PBFs) with smaller pore sizes became available, a large number of particles could be found on the filter surface. In recent years, modern manufacturing methods for CPB circuit components were believed to be associated with a reduced number of particles found in components of extracorporeal circuits, making separate filtration of CPB priming solution unnecessary. Microemboli generated during the preparation and priming procedure of the CPB circuit may consist of either solid particles or gaseous emboli and may contribute to patient morbidity. Endotoxins found in infusion solutions and CPB priming solutions may trigger inflammatory responses when administered into the circulatory system. Filtration of crystalloid CPB priming solutions with a PBF consisting of a filter membrane with a pore size of 0.2 microm was found to effectively reduce the number of microemboli. Infusion filters with a filter pore size of 0.2 microm were found to reduce the endotoxin contamination in infusion solutions. Prebypass filtration with filters containing pores of 0.2 pm should be a necessity for contemporary perfusion practice.

Current strategies for optimizing the use of cardiopulmonary bypass in neonates and infants

The use of cardiopulmonary bypass is still necessary for the repair of many congenital cardiac defects. However, exposure to cardiopulmonary bypass can still lead to major morbidity and sometimes mortality, especially in neonates and infants, despite a perfect surgical repair. Various research-based strategies have been used to minimize some of the complications related to cardiopulmonary bypass, including the systemic inflammatory response, hemodilution, and transfusion requirement. This overview provides some of the strategies that we use in our practice in applying cardiopulmonary bypass in the repair of congenital cardiac defects in neonates and infants.

Experience with an elective vacuum assisted cardiopulmonary bypass in the surgical treatment of renal neoplasms extending into the right atrium

PURPOSE

We evaluate the results of an elective cardiopulmonary bypass conceived to minimize the surgical risk related to its use with temporary circulatory arrest and deep hypothermia in the treatment of patients with renal tumor extending into the right atrium.

MATERIALS AND METHODS

From July 1996 to December 2000, 19 patients with renal neoplasm and venous involvement were admitted to our department. Three patients 4, 57 and 58 years old with a right (2) and left (1) renal tumor extending into the right atrium underwent radical nephrectomy and tumor thrombus removal using a normothermic cardiopulmonary bypass. The bypass circuit was connected with a vacuum assisted venous drainage giving a negative pressure of 20 to 40 mm. Hg. Neither circulatory arrest nor hypothermia was used. Tumor thrombus was extracted through a longitudinal "cavotomy" and removed along with the kidney.

RESULTS

Total cardiopulmonary bypass time was 14, 19 and 22 minutes, respectively. No intraoperative or postoperative complications due to surgical technique occurred. No significant bleeding was observed at the time of cavotomy and all neoplastic tissue was removed. Pathological examination documented renal cell carcinoma in 2 cases and Wilms tumor in 1. All the patients are alive 30, 42 and 15 months, respectively, after the operation.

CONCLUSIONS

Normothermic cardiopulmonary bypass with vacuum assisted venous drainage makes circulatory arrest and hypothermia unnecessary and avoids the potential complications associated with these procedures. With respect to veno-venous shunts this technique guarantees complete surgical control of the thrombus and avoids the need for extensive dissection of the retrohepatic vena cava and Pringle maneuver.