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

Hemodynamic evaluation of a new pulsatile blood pump during low flow cardiopulmonary bypass support

BACKGROUND

The VentriFlo^® True Pulse Pump (VentriFlo, Inc, Pelham, NH, USA) is a new pulsatile blood pump intended for use during short-term circulatory support. The purpose of this study was to evaluate the feasibility of the VentriFlo and compare it to a conventional centrifugal pump (ROTAFLOW, Getinge, Gothenberg, Sweden) in acute pig experiments.

METHODS

Pigs (40-45 kg) were supported by cardiopulmonary bypass (CPB) with the VentriFlo (n = 9) or ROTAFLOW (n = 5) for 6 h. Both VentriFlo and ROTAFLOW circuits utilized standard CPB components. We evaluated hemodynamics, blood chemistry, gas analysis, plasma hemoglobin, and microcirculation at the groin skin with computer-assisted video microscopy (Optilia, Sollentuna, Sweden).

RESULTS

Pigs were successfully supported by CPB for 6 h without any pump-related complications in either group. The VentriFlo delivered an average stroke volume of 29.2 ± 4.8 ml. VentriFlo delivered significantly higher pulse pressure (29.1 ± 7.2 mm Hg vs. 4.4 ± 7.0 mm Hg, p < 0.01) as measured in the carotid artery, with mean aortic pressure and pump flow comparable with those in ROTAFLOW. In blood gas analysis, arterial pH was significantly lower after five hours support in the VentriFlo group (7.30 ± 0.07 vs. 7.43 ± 0.03, p = 0.001). There was no significant difference in plasma hemoglobin level in both groups after six hours of CPB support. In microcirculatory assessment, VentriFlo tended to keep normal capillary flow, but it was not statistically significant.

CONCLUSIONS

VentriFlo-supported pigs showed comparable hemodynamic parameters with significantly higher pulse pressure compared to ROTAFLOW without hemolysis.

Review Article: Comparison of perfusion modes on microcirculation during acute and chronic cardiac support: is there a difference?

Although heart-lung machines and cardiac assist devices have been used successfully for acute and chronic cardiac support for decades, controversies still remain concerning the benefits of pulsatile and non-pulsatile perfusion. The core of the debate is whether enough energy is generated by the artificial pulse to keep capillary beds open and cell metabolism stabilized during acute or chronic cardiac support. In other words, does artificial pulsatility exist in the microcirculation: small vessels of less than 100 μm in diameter? Many investigators have tried to use different tools and biomarkers to reflect directly or indirectly the state of the microcirculation when comparing the two different perfusion modes during acute and chronic cardiac support. However, the results are controversial. First, direct observation of the state of the microcirculation during acute and chronic cardiac support is limited; and reports concerning direct observation of the microcirculation with different perfusion modes in contemporary literature are rare. Secondly, different investigators have used their own criteria to define pulsatile flow. Therefore, it is necessary to develop more efficient methodologies, enabling direct observation of the microcirculation during acute and chronic cardiac support and also establish common criteria that will precisely quantify the pulsatile flow in terms of energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE) levels. Using these critical parameters may explain how excess energy is created by pulsatile flow and maintains perfusion through the microcirculation by ensuring capillary patency. Perfusion (2007) 22, 115—119.

Effect of pulsatile perfusion during cardiopulmonary bypass in terms of radial artery sphygmogram

OBJECTIVE

To investigate a quantitative method for using radial artery pulse waveforms to assess the effect of pulsatile flow during cardiopulmonary bypass (CPB).

METHODS

A total of 34 adults with heart disease who underwent open-heart surgery between April 2010 and January 2011 were randomized into a pulsatile perfusion group (n = 17) and a non-pulsatile perfusion group (n = 17). Radial arterial pulse waveforms of pulsatile and non-pulsatile perfusion patients were observed and compared before and during CDB.

RESULTS

No pulse waveform could be detected at patients' radial artery in both groups when the aorta was cross-clamped. Pulse waveforms could be detected at pulsatile perfusion patients' radial artery, but could not be detected at non-pulsatile perfusion patients' radial artery during CPB. Additionally, patients' pulse waveforms during pulsatile perfusion were lower than those before the operation.

CONCLUSION

Our findings indicate that radial artery sphygmogram can be used as a valid indicator to evaluate the effectiveness of pulsatile perfusion during CPB.

Clinical effectiveness of centrifugal pump to produce pulsatile flow during cardiopulmonary bypass in patients undergoing cardiac surgery

Although the centrifugal pump has been widely used as a nonpulsatile pump for cardiopulmonary bypass (CPB), little is known about its performance as a pulsatile pump for CPB, especially on its efficacy in producing hemodynamic energy and its clinical effectiveness. We performed a study to evaluate whether the Rotaflow centrifugal pump produces effective pulsatile flow during CPB and whether the pulsatile flow in this setting is clinically effective in adult patients undergoing cardiac surgery. Thirty-two patients undergoing CPB for elective coronary artery bypass grafting were randomly allocated to a pulsatile perfusion group (n = 16) or a nonpulsatile perfusion group (n = 16). All patients were perfused with the Rotaflow centrifugal pump. In the pulsatile group, the centrifugal pump was adjusted to the pulsatile mode (60 cycles/min) during aortic cross-clamping, whereas in the nonpulsatile group, the pump was kept in its nonpulsatile mode during the same period of time. Compared with the nonpulsatile group, the pulsatile group had a higher pulse pressure (P < 0.01) and a fraction higher energy equivalent pressure (EEP, P = 0.058). The net gain of pulsatile flow, represented by the surplus hemodynamic energy (SHE), was found much higher in the CPB circuit than in patients (P < 0.01). Clinically, there was no difference between the pulsatile and nonpulsatile groups with regard to postoperative acute kidney injury, endothelial activation, or inflammatory response. Postoperative organ function and the duration of hospital stay were similar in the two patient groups. In conclusion, pulsatile CPB with the Rotaflow centrifugal pump is associated with a small gain of EEP and SHE, which does not seem to be clinically effective in adult cardiac surgical patients.

Neonatal Aortic Arch Hemodynamics and Perfusion During Cardiopulmonary Bypass

The objective of this study is to quantify the detailed three-dimensional (3D) pulsatile hemodynamics, mechanical loading, and perfusion characteristics of a patient-specific neonatal aortic arch during cardiopulmonary bypass (CPB). The 3D cardiac magnetic resonance imaging (MRI) reconstruction of a pediatric patient with a normal aortic arch is modified based on clinical literature to represent the neonatal morphology and flow conditions. The anatomical dimensions are verified from several literature sources. The CPB is created virtually in the computer by clamping the ascending aorta and inserting the computer-aided design model of the 10 Fr tapered generic cannula. Pulsatile (130 bpm) 3D blood flow velocities and pressures are computed using the commercial computational fluid dynamics (CFD) software. Second order accurate CFD settings are validated against particle image velocimetry experiments in an earlier study with a complex cardiovascular unsteady benchmark. CFD results in this manuscript are further compared with the in vivo physiological CPB pressure waveforms and demonstrated excellent agreement. Cannula inlet flow waveforms are measured from in vivo PC-MRI and 3 kg piglet neonatal animal model physiological experiments, distributed equally between the head-neck vessels and the descending aorta. Neonatal 3D aortic hemodynamics is also compared with that of the pediatric and fetal aortic stages. Detailed 3D flow fields, blood damage, wall shear stress (WSS), pressure drop, perfusion, and hemodynamic parameters describing the pulsatile energetics are calculated for both the physiological neonatal aorta and for the CPB aorta assembly. The primary flow structure is the high-speed canulla jet flow (∼3.0 m/s at peak flow), which eventually stagnates at the anterior aortic arch wall and low velocity flow in the cross-clamp pouch. These structures contributed to the reduced flow pulsatility (85%), increased WSS (50%), power loss (28%), and blood damage (288%), compared with normal neonatal aortic physiology. These drastic hemodynamic differences and associated intense biophysical loading of the pathological CPB configuration necessitate urgent bioengineering improvements—in hardware design, perfusion flow waveform, and configuration. This study serves to document the baseline condition, while the methodology presented can be utilized in preliminary CPB cannula design and in optimization studies reducing animal experiments. Coupled to a lumped-parameter model the 3D hemodynamic characteristics will aid the surgical decision making process of the perfusion strategies in complex congenital heart surgeries.

Gastrointestinal Motility During Cardiopulmonary Bypass: A Sonomicrometric Study

Cardiopulmonary bypass (CPB) is known to impair the integrity of the gastrointestinal tract. However, little is known about the movement behavior of the gastrointestinal tract during CPB. This study was aimed to assess the gastrointestinal motility with sonomicrometry, a distance measurement using ultrasound, in a porcine model of CPB. Twelve pigs weighing 70-112 kg were having a standard hypothermic CPB for 120 min either with the nonpulsatile flow (n = 6) or the pulsatile flow (n = 6). Before CPB, piezoelectric echo crystals were placed either along the longitudinal or the circular axis of the pylorus. Patterns of gut movement and the total sonomicrometric activity (TSA) were recorded at several time intervals during experiments as qualitative and quantitative parameters of gut motility. Results showed that the intact regular rhythmic pattern of gut movement was detected before CPB. This pattern changed little when CPB started, but it disappeared at 60 min when the body temperature lowered down to 32 degrees Celsius. During the same period, the TSA reduced significantly along the longitudinal as well as the circular directions of the pylorus. There was no significant difference between the nonpulsatile and pulsatile groups. Gut blood flow reduced significantly in both groups, but it was not associated with the reduced sonomicrometric activity. In conclusion, gastrointestinal motility during CPB can be measured qualitatively and quantitatively by sonomicrometry in a large animal model. Suppression of gut motility during CPB does not seem to be associated with the mode of perfusion but with the reduced body temperature during the hypothermic phase of CPB.

An Evaluation of the Benefits of Pulsatile versus Nonpulsatile Perfusion during Cardiopulmonary Bypass Procedures in Pediatric and Adult Cardiac Patients

The controversy over the benefits of pulsatile and nonpulsatile flow during cardiopulmonary bypass procedures continues. The objective of this investigation was to review the literature in order to clarify the truths and dispel the myths regarding the mode of perfusion used during open-heart surgery in pediatric and adult patients. The Google and Medline databases were used to search all of the literature on pulsatile vs. nonpulsatile perfusion published between 1952 and 2006. We found 194 articles related to this topic in the literature. Based on our literature search, we determined that pulsatile flow significantly improved blood flow of the vital organs including brain, heart, liver, and pancreas; reduced the systemic inflammatory response syndrome; and decreased the incidence of postoperative deaths in pediatric and adult patients. We also found evidence that pulsatile flow significantly improved vital organ recovery in several types of animal models when compared with nonpulsatile perfusion. Several investigators have also shown that pulsatile flow generates more hemodynamic energy, which maintains better microcirculation compared with nonpulsatile flow. These results clearly suggest that pulsatile flow is superior to nonpulsatile flow during and after open-heart surgery in pediatric and adult patients.

Precise Quantification of Pulsatility is a Necessity for Direct Comparisons of Six Different Pediatric Heart-Lung Machines in a Neonatal CPB Model

Generation of pulsatile flow depends on an energy gradient. Surplus hemodynamic energy (SHE) is the extra hemodynamic energy generated by a pulsatile device when the adequate pulsatility is achieved. The objective of this study was to precisely quantify and compare pressure-flow waveforms in terms of surplus hemodynamic energy levels of six different pediatric heart-lung machines in a neonatal piglet model during cardiopulmonary bypass (CPB) procedures with deep hypothermic circulatory arrest (DHCA). Thirty-nine piglets (average weight, 3 kg) were subjected to CPB with a hydraulically driven physiologic pulsatile pump (PPP; n=7), Jostra-HL 20 pulsatile roller pump (Jostra-PR; n=6), Stockert Sill pulsatile roller pump (SIII-PR; n=6), Stockert Sill mast-mounted pulsatile roller pump with a miniature roller head (Mast-PR; n=7), Stockert Sill mast-mounted nonpulsatile roller pump (Mast-NP; n=7), or Stockert CAPS nonpulsatile roller pump (CAPS-NP, n=7). Once CPB was begun, each animal underwent 20 minutes of hypothermia, 60 minutes of DHCA, 10 minutes of cold reperfusion, and 40 minutes of rewarming. The pump flow rate was maintained at 150 ml x kg(-1) x min(-1) and the mean arterial pressure (MAP) at 45 mm Hg. In the pulsatile experiments, the pump rate was kept at 150 bpm and the stroke volume at 1 ml/kg. The SHE (ergs/cm3) = 1,332 ([(integral fpdt) / (integral fdt)] - MAP) was calculated at each experimental stage. During normothermic CPB (15 minutes on pump), the physiologic pulsatile pump generated the highest surplus hemodynamic energy (8563 +/- 1918 ergs/cm3, p < 0.001) compared with all other pumps. The Jostra HL-20 and Stockert Sill pulsatile roller pumps also produced adequate surplus hemodynamic energy. Nonpulsatile roller pumps and the Stockert Sill mast-mounted pulsatile roller pump did not generate any extra hemodynamic energy. During hypothermic CPB and after DHCA and rewarming, the results were extremely similar to those seen during normothermic CPB. The surplus hemodynamic energy formula is a novel method to precisely quantify different levels of pulsatility and nonpulsatility for direct and meaningful comparisons. The PPP produced the greatest surplus hemodynamic energy. Most of the pediatric pulsatile pumps (except Mast-PR) generated significant surplus hemodynamic energy. None of the nonpulsatile roller pumps generated adequate surplus hemodynamic energy.