Augmented femoral venous return

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.

Transfusion-free neonatal cardiopulmonary bypass using a TinyPump

BACKGROUND

We devised a miniaturized circuit incorporating a TinyPump in the venous line to amplify the venous return. We compared this system to the conventional blood-primed circuit and investigated whether this circuit could maintain hematocrit levels without blood transfusion and reduce coagulation and inflammatory cascades.

METHODS

Thirteen 1-week-old piglets (3.7 ± 0.2 kg) were divided into group M (miniaturized circuits with TinyPump-assisted venous drainage without blood, n = 7) and group C (conventional circuits with blood priming, n = 6). Cardiopulmonary bypass (CPB) was performed at 150 to 180 mL·kg(-1)·min(-1) for 2 hours, including 60 minutes of cardioplegic cardiac arrest. Modified ultrafiltration (MUF) was subsequently performed. Data were acquired before CPB and after the end of MUF.

RESULTS

The priming volume including the hemofilter circuit of the main circuit required 152 mL in group M and 300 mL in group C. The mean hematocrit values in group M and group C were not significantly different during CPB (21.5% ± 2.0% versus 23.2% ± 1.3%) or after MUF (30.7% ± 2.1% versus 32.9% ± 4.0%). After MUF, group M had lower thrombin-antithrombin complex levels (16.7 ± 5.0 ng/mL versus 28.4 ± 8.4 ng/mL, p < 0.01) and interleukin-8 levels (2,867 ± 758 pg/mL versus 13,730 ± 5,220 pg/mL, p < 0.01) than group C. The pulmonary vascular resistance index was lower in group M after MUF (4,105 ± 862 dynes·cm(-5)·kg(-1) versus 6,304 ± 1,477 dynes·cm(-5)·kg(-1), p < 0.01). The lung water content was also better in group M (83.7% ± 0.5% versus 84.9% ± 0.5%, p < 0.01).

CONCLUSIONS

The minicircuit with TinyPump-assisted venous drainage successfully maintained acceptable hematocrit levels and the cardiopulmonary function in neonatal piglets. Employing this technique may attenuate blood requirements and inflammatory responses, thereby improving the clinical outcomes of neonatal open-heart surgery.

Use of a soft reservoir bag in a fully heparin-coated closed-loop cardiopulmonary bypass system for distal aortic perfusion during aortic surgery

A fully heparin-coated closed-loop cardiopulmonary bypass system has recently been introduced into clinical practice. Without a venous reservoir, however, it does not allow control of the preload to the heart. We connected a soft reservoir bag in parallel with a centrifugal pump to enable preload control and clinically evaluated this modified system for distal aortic perfusion during aortic surgery. We have used the modified system in 17 patients since November 2002. For venous drainage, we use long narrow cannulae (21 +/- 2 French). We administered 1 mg/kg heparin without cardiotomy suction and 2 mg/kg heparin with suction. We compared the clinical results with those in 13 patients who underwent distal aortic perfusion with an open cardiopulmonary bypass circuit between January 2002 and February 2004. We also analyzed factors affecting the coagulation system in these 30 patients using multiple regression analysis. With the modified system, venous drainage was adequate despite the use of smaller cannulae, and heparin reduction was not associated with thrombotic complication or elevated D-D dimer levels. Abrupt rises in proximal aortic pressure on aortic cross-clamping could be avoided by allowing blood to drain into the soft reservoir bag. Clinical results were not different from those with an open system. In the multiple regression analysis, the peak activated clotting time tended to correlate with postoperative platelet counts. This system is effective in controlling the preload to the heart and allows the safe reduction of heparin dosage. It therefore seems useful for distal aortic perfusion during aortic surgery.

A new expandable cannula to increase venous return during peripheral access cardiopulmonary bypass surgery

Peripheral cannulation for cardiopulmonary bypass (CPB) is of prime interest in minimally invasive open heart surgery. As CPB is initiated with percutaneous cannulae, venous drainage is impeded due to smaller vessel and cannula size. A new cannula was developed which can change shape in situ and therefore may improve venous drainage. An in vitro circuit was set-up with a penrose latex tubing placed between the preload reservoir and the cannula, encasing the cannula's inlet and simulating the vena cava. The preload (P) was stabilised at 2 and at 5 mmHg respectively. The maximum flow rate was determined for 4 conditions: passive venous drainage (PVD) and assisted venous drainage (AVD) using a centrifugal pump at the 2 preload settings. We compared the results of the prototype cannula to classical femoral venous cannulae: basket 28Fr, a thoracic 28Fr and a percutaneous 27Fr. Under PVD conditions and a CVP of 2 mmHg, the prototype cannula's flow rate outperformed the next best cannula by 14% (p=0.0002) and 13% under AVD conditions (p=0.0001). Under PVD conditions and a CVP of 5 mmHg, the prototype cannula outperformed the percutaneous cannula by 19% (p=0.0001) and 14% under AVD conditions (p=0.0002). The new cannula outperforms the classical percutaneous venous cannulae during all of the four conditions tested in vitro.

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.

Venoarterial air embolus: a complication of vacuum-assisted venous drainage

Minimal access techniques with cardiopulmonary bypass use smaller cannula systems for management of cardiopulmonary bypass. To augment flow rates through the smaller cannula, the technique of vacuum-assisted venous drainage has been used. We describe a complication of vacuum-assisted venous drainage by inadvertent positive pressurization of the venous circuit resulting in a paradoxic air embolus across a patent atrial septal defect. Hazards of the current cardiopulmonary bypass systems and techniques for avoiding this potential complication are discussed.

Development of a completely closed circuit using an air filter in a drainage circuit for minimally invasive cardiac surgery

The completely closed circuit system is the future direction of cardiopulmonary bypass because of its compactness and superior biocompatibility. The most serious obstacle for clinical application is the sucking of air bubbles into the drainage circuit. The purpose of this study was to remove the air bubbles from the drainage circuit. Infusing 50 ml/min of air bubbles into the drainage circuit of the usual closed circuit, and infusing 50, 100, and 150 ml/min of air into the drainage circuit of a newly developed closed circuit (drainage circuit using an air filter), the number and size of air bubbles were observed at the outlet of the arterial filter. In the usual closed circuit, many air bubbles of over 40 microm were detected within 5 s at a blood flow of 4 L/min because the centrifugal pump decreased the size of the bubbles, which then passed through the oxygenator and arterial filter. Air bubbles of over 40 micro were not detected in the newly developed closed circuit within 5 min at a blood flow of 4 L/min. The removal of air mixed into the completely closed circuit was possible with a drainage circuit using an air filter that was developed. The clinical use of the completely closed circuit for minimally invasive cardiac surgery (MICS) became possible based on this development.

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.

Laboratory testing of femoral venous cannulae: effect of size, position and negative pressure on flow

Femoral venous cannulae (17-28 French) were tested to compare flows obtained by their placement in a simulated inferior vena cava (IVC) or right atrium (RA) and by varying drainage pressures using gravity siphon drainage or a centrifugal pump in the venous line. The circuit consisted of conventional tubing and equipment including a segment of thin-walled latex tubing to simulate the IVC connected to a flexible reservoir to simulate the RA. The test fluid was a 40% glycerin solution. Flow was measured at height differentials of 30-60 cm (cannula-to-inlet of hard-shell venous reservoir) and with a -10 to -80 mmHg negative pressure created by the centrifugal pump. A roller pump returned the test fluid to a flexible bag to maintain a filling pressure of 0-1 mmHg. Flow increased modestly with an increasing height differential. When negative pressure was applied with the centrifugal pump, flow increased 10% and 18% (IVC and RA positions, respectively) compared to gravity siphon drainage conditions. There also was a tendency for flow to plateau or cease when the centrifugal pump was used at higher levels of negative pressure or when larger cannulae were used. We conclude: (1) position of smaller cannulae in the RA yield better flows than when the cannulae are larger and placed in the IVC; (2) smaller-sized cannulae are capable of achieving higher flows when the centrifugal pump is used; (3) cannulae must be properly positioned to achieve maximum flow; (4) the centrifugal pump will augment flow, but should be regulated to avoid extreme negative pressures; and (5) cannula design has no demonstrable effect on flow.

Augmented venous return for minimally invasive open heart surgery with selective caval cannulation

OBJECTIVE

Minimally invasive open heart surgery involves limited intrathoracic cannulation sites necessitating cardiopulmonary bypass to be initiated via peripheral access using percutaneous cannulae with the tip placed into the right atrial cavity. However, surgery involving the opening of the right heart obliges the surgeon to maintain the end of the cannulae into the vena cavae. The impeded venous return due to the smaller diameter may be alleviated by inserting a centrifugal pump in the venous line.

METHODS

Right anterior mini-thoracotomy and exposure of the femoral site were performed before the patient was heparinized. Cannulation of the femoral artery, the inferior vena cava via the femoral vein and the superior vena cava through the mini-thoracotomy was performed and cardiopulmonary bypass was initiated. Venous drainage was augmented with the centrifugal pump. Cardiac arrest was provoked and both vena cavae were snared before performing the intracardiac procedure.

RESULTS

Twenty consecutive patients were operated on using this technique (15 males/five females; age: 44.8 +/- 14.3 years; bodyweight: 73.5 +/- 15.1 kg; body surface area: 1.8 +/- 0.2 m2; theoretical blood flow rate: 4.4 +/- 0.5 l/min). The cannula sizes were 21.9 +/- 2.2 Fr for the femoral artery, 26.5 +/- 1.7 Fr for the inferior vena cava and 23.8 +/- 2.5 Fr for the superior vena cava. Venous drainage through the single inferior vena cava cannula was 2.1 +/- 0.6 l/min (48.8 +/- 13.3% of the theoretical flow). Adding the superior vena cava cannula increased the venous flow to 3.1 +/- 0.4 l/min (70.7 +/- 9.6% of the theoretical value, P < 0.005). The use of the centrifugal pump increased the flow to 4.1 +/- 0.6 l/min (93.4 +/- 8.9% of the theoretical flow, P < 0.001) with a mean inlet negative pressure of -69 +/- 10.2 mmHg. The mean bypass time was 64.0 +/- 24.6 min for a mean operative time of 226.3 +/- 61.0 min. Minimum venous saturation was 69.4 +/- 8.5%.

CONCLUSIONS

Despite the smaller diameter of the vena cavae compared to the right atrium, and a smaller internal diameter of percutaneous cardiopulmonary bypass cannulae compared to classic ones; the centrifugal pump improves the venous drainage significantly so that minimally invasive open heart procedures can be performed under optimal and safe perfusion conditions.

Total extrathoracic cardiopulmonary support with kinetic assisted venous drainage: experience in 50 patients

Extrathoracic cardiopulmonary bypass is used in special situations when normal access to the right atrium and aorta is difficult or not practicable. Femero-femoral bypass using gravity drainage is effective for partial cardiopulmonary support, but cannot usually provide adequate venous drainage for full circulatory support. Kinetic assisted venous drainage (KAVD) is the process of applying a controlled suction on the venous line with a kinetic pump to augment venous drainage. KAVD has been used in 50 patients where femero-femoral bypass was selected as the mode of circulatory support. These cases included: redo-operations with significant sternal adhesions (15), minimally invasive port-access cardiac surgery (12), haemodynamic instability (10), left thoracotomy (10), and others (3). In 11 cases, a second venous catheter was added because of protocol. No appreciable increase in venous return occurred with the addition of a second drainage catheter. All patients were adequately supported and a 20-40% increase in venous return was observed once KAVD was implemented. A wide variety of different venous catheters have been used with KAVD. Optimal use relates to having a thin-walled catheter with multiple side holes, not exerting an excessive negative pressure with the pump and positioning the catheter tip at the right atrio-superior vena cava junction. Optimal catheter tip placement is enhanced by using transoesophageal echocardiography. KAVD is best regulated by measuring the siphon generated by the kinetic pump. When the inlet pressure is properly monitored and controlled, KAVD can provide adequate venous drainage to completely support the circulation on a single femoral venous cannula.

Continuous retrograde cardiac perfusion decreases risk of reoperative coronary artery bypass grafting

Embolization of atheromatous debris from old saphenous vein grafts is a major factor that increases the risk of reoperative coronary artery bypass grafting (CABG) when compared with primary CABG. To decrease this risk, a technique consisting of minimal dissection of the heart prior to cross clamping, continuous retrograde coronary sinus perfusion with 32 degrees C blood, and temporary posterior cardiac interventricular vein occlusion, during which time all dissection and anastomoses are performed, was evaluated prospectively in 130 consecutive patients from January 2, 1991, through February 28, 1995. This group was compared with a cohort of 1107 patients undergoing primary CABG performed concurrently. The two groups were similar in age (median sixty-eight years), incidence of hypercholesterolemia, peripheral vascular disease, smoking history, and left main stem stenosis. More patients undergoing reoperative CABG had previous myocardial infarctions (61.5% vs 54.5%), a higher incidence of triple-vessel coronary artery disease (89.2% vs 77.1%, P = 0.002), and a lower ejection fraction (54.0% vs 56.9%). The median interval from primary CABG to reoperative CABG was one hundred twenty-seven months with a range of 2.5 to two hundred seventy-nine months. The cross clamp time (median one hundred three vs sixty-nine minutes, P = 0.000001) and perfusion time (median one hundred thirty-four vs ninety-four minutes, P = 0.000001) were significantly higher in the reoperative CABG group. The requirements for inotropic support postoperatively, perioperative myocardial infarction (1.5% vs 2.4%, P = 0.397), and mortality (3.1% vs 3.4%, P = 0.54) were statistically equivalent in the two groups. These data reveal that continuous retrograde coronary sinus perfusion, posterior cardiac interventricular vein occlusion, and single cross-clamping technique improve outcomes of reoperative CABG to that approaching primary CABG.

Extracorporeal circuit design considerations for giant intracranial aneurysm repair

Clinical perfusionists must be able to modify the existing extracorporeal circuit in order to accommodate a specific surgical pathology. The clipping of a giant intracranial middle cerebral artery aneurysm, unapproachable with conventional neurosurgical techniques, required the use of a modified closed cardiopulmonary bypass circuit combined with deep hypothermia and total circulatory arrest. In-hospital discussions with anaesthesia, cardiac surgery, neurosurgery, and cardiology enabled an informed team approach directed towards the successful treatment of this complex neurosurgical lesion.