A novel technique for cardiopulmonary bypass using vacuum system for venous drainage with pressure relief valve: an experimental study

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.

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.

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.

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.

History of cardiopulmonary bypass (CPB)

The development of cardiopulmonary bypass (CPB), thereby permitting open-heart surgery, is one of the most important advances in medicine in the 20th century. Many currently practicing cardiac anesthesiologists, cardiac surgeons, and perfusionists are unaware of how recently it came into use (60 years) and how much the practice of CPB has changed during its short existence. In this paper, the development of CPB and the many changes and progress that has taken place over this brief period of time, making it a remarkably safe endeavor, are reviewed. The many as yet unresolved questions are also identified, which sets the stage for the other papers in this issue of this journal.

A Brief History of Cardiopulmonary Bypass

The development and application of cardiopulmonary bypass (CPB) to permit open heart surgery is considered among the most important clinical advances in medicine during the last half of the 20th century. The birth of CPB for cardiac surgery is attributed to its first successful clinical use by John Gibbon Jr, 51 years ago but its practical clinical use really began in the spring and summer of 1955 when 2 groups led by John Kirklin at the Mayo Clinic and C Walton Lillehei at the University of Minnesota, initiated the routine use of CPB for open heart surgery. However, considerable developments were necessary and preceded the clinical accomplishment of CPB, and much has followed to make it the remarkably safe and effective procedure that it has become today. Many currently practicing cardiac anesthesiologists, cardiac surgeons, and perfusionists are unaware of how brief its history is and how much the practice of CPB has changed during its short existence. The aim of this article is to review this fascinating history and the lessons that can be learned from this review, and to indicate the opportunities that still exist for advancement.

Venous drainage--gravity or assisted?

Since the early start of cardiopulmonary bypass, vascular access has been recognized as a main variable for obtaining optimal blood flow during cardiopulmonary bypass. In particular, venous drainage can limit the maximum flow as the wide, low-resistance, collapsible veins are connected with smaller stiff cannulas and tubing. Due to the introduction of long venous cannulas for minimally invasive cardiac surgery and the desire to limit hemodilution during cardiopulmonary bypass, more and more centers have started using assisted venous drainage techniques. This article gives an overview of these techniques, with their respective advantages and disadvantages.

Perfusionist strategies for blood conservation in pediatric cardiac surgery

There is increasing concern about the safety of homologous blood transfusion during cardiac surgery, and a restrictive transfusion practice is associated with improved outcome. Transfusion-free pediatric cardiac surgery is unrealistic for the vast majority of procedures in neonates or small infants; however, considerable progress has been made by using techniques that decrease the need for homologous blood products or even allow bloodless surgery in older infants and children. These techniques involve a decrease in prime volume by downsizing the bypass circuit with the help of vacuum-assisted venous drainage, microplegia, autologous blood predonation with or without infusion of recombinant (erythropoietin), cell salvaging, ultrafiltration and retrograde autologous priming. The three major techniques which are simple, safe, efficient, and cost-effective are: a prime volume as small as possible, cardioplegia with negligible hydric balance and circuit residual blood salvaged without any alteration. Furthermore, these three techniques can be used for all the patients, including emergencies and small babies. In every pediatric surgical unit, a strategy to decrease or avoid blood bank transfusion must be implemented. A strategy to minimize transfusion requirement requires a combined effort involving the entire surgical team with pre-, peri-, and postoperative planning and management.

The clinical pathway for fast track recovery of school activities in children after minimally invasive cardiac surgery

BACKGROUND

Minimally invasive cardiac surgery is now becoming standard in the correction of simple congenital cardiac malfbrmations. We introduced a clinical pathway for fast track recovery of school activities in children after minimally invasive cardiac surgery, and assessed the function of the pathway in children with atrial or ventricular septal defects, comparing minimally invasive surgery to repair through a conventional full sternotomy.

METHODS

We studied 15 children of school age who underwent repair of an atrial or ventricular septal defect through a lower midline sternotomy, and 10 children undergoing repair through a full sternotomy. The clinical pathway was for extubation to take place in the operating room, echocardiographic evaluation on the 5th postoperative day, and discharge home on the 7th postoperative day, with return to school within 2 weeks, and resumption of all gymnastic activity within 6 weeks of the minimally invasive surgery.

RESULTS

In those having a lower midline sternotomy, postoperative hospital stay was 7.4 +/- 0.8 days, with return to school 8.0 +/- 2.4 days after discharge. They resumed gymnastics 41 +/- 11 days after the minimally invasive surgery. In those having a full sternotomy, in contrast, these parameters were 13.5 +/- 2.7, 23.1 +/- 8.4, and 95 +/- 43 days, respectively. Of the 15 children undergoing a minimally invasive approach, 12 (80%) fulfilled the criterions of our clinical pathway.

CONCLUSIONS

We conclude that minimally invasive cardiac surgery can safely be performed in children. In addition to its cosmetic role, the technique has added value in promoting early return to normal school life, including gymnastics.

Biochemical evaluation of vacuum-assisted venous drainage: a randomized, prospective study

AIMS OF THE STUDY

In this prospective, randomized study, we investigate the potential advantages of vacuum-assisted venous drainage (VAVD), compared to gravitational drainage (GD), in patients undergoing first-time coronary artery bypass graft (CABG) surgery, concerning biochemical markers of organ and blood cell damage.

MATERIALS AND METHODS

Seventy-two consecutive patients were randomized into two groups ['Vacuum' (VAVD) n=36; 'Not vacuum' (GD) n=36]. VAVD was achieved using a wall vacuum source and with a suction regulator connected to the vent port of the hardshell venous reservoir. In the VAVD group, we used 28-French venous cannulas, and 36-French in the GD group. In the VAVD group, we measured arterial perfusion flow (APF) and the venous reservoir volume (VRV) with and without vacuum application just after starting extracorporeal circulation (ECC). Six blood samples were drawn at different times before, during and after ECC. Routine blood tests were performed to evaluate hemolysis, and hepatic and renal function.

RESULTS

The two groups were similar in terms of preoperative and operative characteristics. There were no significant differences in biochemical markers of organ function or hemolysis between the two groups. In the VAVD patients, platelet count was higher at 24 h after the end of the operation (VAVD 151.77+/-50.28 microl versus Not vacuum 124.93+/-41.60 microl, p=0.028). With the narrower venous cannulas (28-French), only VAVD achieved a satisfactory APF (VAVD 2.35+/-0.38 l/min/m2 versus GD 1.88+/-0.27 l/min/m2, p=0.002), with a larger VRV (VAVD 1091.67+/-421 ml versus GD 808.33+/-284.31 ml, p=0.025).

CONCLUSION

Vacuum-assisted venous drainage is a technique comparable to gravitational drainage with regard to hemolysis and organ perfusion. It allows better perfusion flow and heart decompression with smaller venous cannulas. This study suggests reduced platelet consumption with VAVD.

Biomaterial development for cardiopulmonary bypass

Cardiopulmonary bypass (CPB) is dependent on materials foreign to the patient for its successful application. When blood comes into contact with these so-called biomaterials, an inappropriate inflammatory response, which can be life-threatening in some patients, may develop. The reason for this inappropriate activation of host defence mechanisms is not entirely clear, however a number of strategies have evolved over the years to minimize this unwanted sequelae of CPB. These strategies include surface coating of the materials of the circuit, using new materials thought to improve biocompatibility, and using a number of pharmacological interventions designed to suppress the inflammatory response. Recently, there has been some evidence which indicates that the plasticizer employed in the polyvinyl chloride (PVC) tubing of the CPB circuit may play a part in the development of the inflammatory response. The work described in this paper tends to support this thesis. These studies showed that by washing the plasticizer from the surface of the PVC tubing, the biocompatibility, as reflected in the upregulation of CD11b on the surface of neutrophils, was enhanced. Furthermore, the use of non-plasticized substitutes for PVC had a similar effect. The benefit from removing the plasticizer was similar to that gained from surface coating with heparin, one of the conventional approaches to reducing the inflammatory response to CPB.

Clinical application of vacuum-assisted cardiopulmonary bypass with a pressure relief valve

OBJECTIVES

Hemodilution induced by cardiopulmonary bypass (CPB) often prevents open heart operations without blood transfusion because of a large CPB-priming volume. A vacuum-assisted venous drainage system appears to overcome this problem and our previous experimental study demonstrated the beneficial effect of a vacuum-assisted CPB with a pressure relief valve. In this study, we clinically applied this novel system, and evaluated its efficacy by comparing it with the results of a conventional siphon-dependent drainage system.

METHODS

Sixty patients undergoing open heart operation were divided into Group V (vacuum-assisted system, n=30) and Group S (siphon-dependent system, n=30). The vacuum-assisted system contains a powerful vacuum generator and a pressure relief valve to keep the negative pressure in the reservoir constant when the blood suction is used.

RESULTS

The CPB-priming volume was significantly smaller in Group V (V vs. S: 1071+/-88 vs. 1405+/-137 ml; P<0.01), resulting in the lower hemodilution in Group V evidenced by the minimum hemoglobin level (V vs. S: 6.83+/-1.06 vs. 5.78+/-0.79 mg/dl; P<0.01) and blood transfusion rate (V vs. S: 9 vs. 20%; P<0.01). There were no significant differences in the plasma free hemoglobin level and the reduction ratio of plasma haptoglobin between the groups.

CONCLUSIONS

These data demonstrate that this vacuum-assisted CPB can provide simplification of the CPB circuit, resulting in a smaller CPB-priming volume and lower hemodilution. This vacuum-assisted CPB may attenuate the negative effect of CPB by minimizing hemodilution and appears to be a useful modification to accomplish no blood-requiring open heart operations.

The effect of circuit surface area on CD11b(mac-1) expression in a rat recirculation model

The aim of the study was to assess the effect of exposed surface area of diethylhexylphthalate plasticized polyvinylchloride (PVC) on the expression of the adhesion molecule CD11b(mac-1) on neutrophils and to determine whether there is any apparent advantage in the current trend in reducing circuit surface area in terms of neutrophil activation. The study was carried out using a parallel plate rodent recirculation biomaterial testing model on 4 groups of 10 adult male Sprague Dawley rats weighing between 350 and 450 g. One group comprised the control group in which there was no biomaterial exposure. In the remaining 3 groups, the animals were subjected to either high (48 cm2), intermediate (24 cm2), or low (12 cm2) biomaterial surface area exposure. The parallel plate test cell was connected to the right femoral circulation and recirculation initiated at a flow rate of 1.5 ml/min for a period of 60 min. Blood samples were taken at 0, 30, and 60 min for the assessment of CD11b expression. Cd11b was assessed using flow cytometric analysis on neutrophils. The results demonstrated that there was a surface area related effect in the upregulation of CD11b. The difference at the terminal sample point between the highest surface area group (293.95 +/- 18.57%) and the low surface area group (133.80 +/- 49.31%) was highly statistically significant (p < 0.001). These results demonstrate that there may be some gain in terms of reduced inflammatory response from reducing the exposed surface area of PVC in extracorporeal perfusion circuits.

Assisted venous drainage cardiopulmonary bypass in congenital heart surgery

BACKGROUND

A novel active venous drainage perfusion circuit was designed to achieve effective venous return through small venous cannulas. The efficacy and safety of this new system was investigated and compared with a conventional gravity drainage system.

METHODS

Four hundred consecutive patients undergoing open heart repair of congenital heart lesions by one surgeon were studied. The first 200 patients were supported by gravity drainage and the next 200 patients were supported by assisted venous drainage. No patient in the time period was excluded from the study.

RESULTS

The two groups did not differ significantly in weight, bypass time, or cross-clamp time. Priming volumes were less in the assisted group than in the gravity group (576+/-232 mL versus 693+/-221 mL, p < 0.001). Venous cannula size was smaller in the assisted group when compared with the gravity group (33.2F+/-7.4F versus 38.5F+/-7.1F, p < 0.001). There was a trend to lower operative mortality in the assisted drainage group (5 of 200, 2.5% versus 11 of 200, 5.5%; p = 0.10). Hospital stay and pulmonary, infectious, and neurologic complications were comparable in both groups. Cardiac complications were less common in the assisted group than in gravity group (22 of 200, 11% versus 38 of 200, 19%; p = 0.017). Hematologic complications were less common in the assisted group than the gravity group (6 of 200, 3% versus 19 of 200, 9.5%; p < 0.01).

CONCLUSIONS

These findings suggest that assisted venous drainage is safe in congenital heart operations and facilitates the use of smaller venous cannulas.

Vacuum assisted cardiopulmonary bypass in minimally invasive cardiac surgery: its feasibility and effects on hemolysis

The present study describes a cardiopulmonary bypass (CPB) technique that incorporates vacuum assisted venous drainage and arterial return using a centrifugal pump in minimally invasive cardiac surgery (MICS). The technique was performed on 40 patients scheduled to undergo MICS. The proposed CPB technique enables a good operative field to be obtained even through a limited incision through the use of peripheral cannulation using small cannulae. Vacuum pressure was applied to the venous reservoir (-43 +/- 14 mm Hg) to maintain adequate CPB flow (>2.4 L x min-1 x M-2). The effects of CPB on hemolysis were subsequently compared between patients who underwent the proposed procedure (MICS group; n = 6) and a control group who underwent coronary arterial bypass grafting (CABG group; n = 6) with conventional CPB. Plasma free hemoglobin (FHb) increased and plasma haptoglobin (Hp) decreased during CPB in both groups, with no significant difference between the groups. By the next day, FHb had returned to pre-CPB levels whereas Hp remained lower in both groups. Again, these values did not differ significantly between groups. Thus, we conclude that the proposed CPB technique is useful in MICS with acceptable effects on hemolysis.

Impact of modifying priming components and fluid administration using miniaturized circuitry in neonatal cardiopulmonary bypass

Following a succession of changes in circuitry and priming additives between 1993 and 1998, a comprehensive re-evaluation of neonatal cardiopulmonary bypass (CPB) practice was undertaken. Samples from 10 infants (Group 1) undergoing CPB were evaluated for osmolality, oncotic pressure, total protein, hematocrit, glucose, and electrolytes (Na+, K+, iCa2+). These samples were tested at six measurement points: (1) after priming, (2) patient pre-CPB, (3) CPB-start, (4) CPB-mid, (5) CPB-end, and (6) post-modified ultrafiltration (MUF). Prime volumes were also carefully measured as well as the type and amount of volume given during CPB. After evaluating the initial data, changes in protocol regarding mannitol, calcium correction, and oncotic strength on CPB were made. Following implementation of these protocol changes, a second set (Group 2) of 10 infants was identically evaluated. Group 1 prime osmolality was 379 +/- 44 mOsm/kg, while Group 2 prime osmolality was 324 +/- 14 mOsm/kg (p = 0.003). There were no differences in osmolality between groups during bypass and osmolality was unaffected by modified ultrafiltration. Ionized calcium levels were significantly different at the end of bypass between Group 1, 0.6 +/- 0.1 mmol/l; and Group 2, 1.17 +/- 0.24 mmol/l (p < 0.001). In Group 1, there was a 40% drop (p = 0.001) in colloid osmotic pressure (COP) levels from pre-CPB (13.3 +/- 3.4 mmHg) to CPB-end (8.8 +/- 1.2 mmHg). In Group 2, there were no differences in COP during CPB. COP levels of Group 1 and Group 2 at CPB-end were 8.8 +/- 1.2 mmHg and 14 +/- 1.9, respectively (p < 0.0001). Total volume addition during bypass for Group 1 was 363.5 +/- 148.7 ml and for Group 2 was 245.1 +/- 92.2 ml (p < 0.05). In conclusion, progressive changes in neonatal circuits and techniques can have potentially wide-ranging effects on electrolyte and osmotic/oncotic homeostasis. An audit of perfusion management through expanded laboratory tests is recommended, especially in periods of change.

A new bladder allows kinetic venous augmentation with a roller pump

Augmented venous drainage improves venous return during minimally invasive cardiac surgery. Two systems to augment drainage are common: in one, a centrifugal pump draws blood from the venous site and pumps it into a venous reservoir. In the other, suction is applied directly to a hard-shell venous reservoir. Both systems overcome the high resistance of the venous cannula when gravity alone is insufficient to provide adequate drainage. Both systems also have shortcomings: in the first approach, the centrifugal pump head can entrap large bubbles, reducing flow and requiring pump stoppage to remove them. Air from the venous line also can be broken up by the centrifugal pump into small bubbles that can pass through the pump head. The direct suction system in the second approach cannot use a closed-bag reservoir, and has the potential to introduce air into the arterial line. We have developed a new venous augmentation system for a closed venous reservoir that provides excellent suction control without the potential to introduce air into the arterial line. Our system replaces the centrifugal pump of the first approach with a roller pump controlled by the Better-Bladder, a new device with FDA 510(k) clearance for long-term pumping. The Better-Bladder is a length of medical tubing, processed to form a thin-walled, enlarged bladder that is sealed within a clear rigid housing. It acts as an in-line reservoir that provides compliance in the venous line and a noninvasive means to measure blood pressure at the pump inlet. The bladder housing can maintain a negative pressure set by the user that controls the degree of gravity drainage. Tests have shown that the Better-Bladder allows for safe, smooth pump control using a roller pump in the venous line.

Vacuum assisted venous drainage (VAVD)

Poor venous drainage is a common problem in cardiac surgery, causing trouble for the surgeon and adverse effects to the patient. Smaller incisions for minimally invasive cardiac surgery require smaller venous catheters. In this study the function, safety and possible benefits of a system for vacuum assisted venous drainage has been tested experimentally and applied clinically. A vacuum regulator ('The Hamlet box') and safety procedures were developed. The system was characterized in vitro in regard to the relationship between vacuum, catheter size, and blood temperature and flow. The clinical study included 54 adult patients, coronary artery bypass graft surgery and valve operations. Venous cannulation was bi-caval with two 24 Fr catheters. All the perfusions were essentially event free, and the system was easy to manage and regulate. Venous drainage was totally adequate, irrespective of the position of the heart, and less fluid was added during the perfusions (a median of 250 ml/patient compared to a median of 1000 ml/patient in the control group). There has been no evidence of increased haemolysis or other adverse effects. All patients were hospital survivors and had uneventful postoperative courses. Vacuum assisted venous drainage is now used routinely, and further studies are under way to develop the system and clarify the physiological effects.

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

BACKGROUND

Arterial emboli cause neurocognitive deficits in cardiac surgical patients. Carotid artery emboli, detected ultrasonically, have been observed after venous air entrainment into the cardiopulmonary bypass circuit. We investigated in vitro the extent to which venous air affected emboli detected in the arterial line downstream from a 40-microm filter.

METHODS

Using salvaged clinical cardiopulmonary bypass circuits, fixed volumes of air were introduced into the venous return line at unrestricted rates and at fixed rates using gravity venous drainage and vacuum-assisted venous drainage. Emboli counts were recorded distal to the arterial line filter using a 2-MHz pulsed-wave Doppler monitor. Emboli counts were similarly recorded after the introduction of carbon dioxide into the venous return line instead of air.

RESULTS

The number of emboli rose with increasing volumes of entrained venous air (p < 0.001), and there was an almost tenfold increase with vacuum-assisted venous drainage (p < 0.0001) compared with gravity venous drainage. Venous air was entrained at a significantly faster rate under vacuum-assisted venous drainage (p < 0.0001). When the entrainment rate of venous air was fixed, the difference in emboli numbers recorded for gravity and assisted venous drainage was not significant. There was a significant reduction in arterial line emboli when carbon dioxide rather than air was entrained under both vacuum-assisted and gravity drainage (p < 0.001).

CONCLUSIONS

Entrained venous air during cardiopulmonary bypass is a potential hazard, particularly during vacuum-assisted venous drainage. Every effort should be made to avoid venous air entrainment.

Minimally invasive cardiac surgery: current status and perspective

Recently, the minimally invasive approach has become a growing aspect in the field of cardiac surgery with the goal of eliminating cardiopulmonary bypass (CPB) and/or median sternotomy. In coronary bypass surgery, the application of this approach is direct anastomosis, primarily of the left internal thoracic artery to the left descending coronary artery under a beating condition without the use of CPB through a small left thoracotomy minimally invasive direct coronary artery bypass (MIDCAB). In the repair of intracardiac lesions, CPB cannot be excluded, but a small right parasternal incision or small partial sternotomy (ministernotomy) has been applied for congenital defects and mitral and aortic valve lesions. With technological advances in CPB, these approaches may become more popular in the near future.