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Miyamoto T, Sunagawa G, Dessoffy R, Karimov JH, Grady P, Naber JP, Vincent D, Sale SM, Kvernebo K, Tran VNP, Moazami N, Fukamachi K. Hemodynamic evaluation of a new pulsatile blood pump during low flow cardiopulmonary bypass support. Artif Organs 2021; 46:643-652. [PMID: 34780074 DOI: 10.1111/aor.14119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 10/05/2021] [Accepted: 11/11/2021] [Indexed: 11/24/2022]
Abstract
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.
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Affiliation(s)
- Takuma Miyamoto
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Gengo Sunagawa
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Raymond Dessoffy
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Jamshid H Karimov
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Patrick Grady
- Department of Thoracic and Cardiovascular Surgery, Miller Family Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | | | | | - Shiva M Sale
- Department of Cardiothoracic Anesthesiology, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Knut Kvernebo
- Department of Cardio-thoracic Surgery, Oslo University Hospital, Ullevaal, Oslo, Norway
| | - Van N P Tran
- Department of Cardio-thoracic Surgery, Oslo University Hospital, Ullevaal, Oslo, Norway
| | - Nader Moazami
- Department of Cardiothoracic surgery, New York University's Langone Health, New York, New York, USA
| | - Kiyotaka Fukamachi
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
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Surman TL, Abrahams JM, Manavis J, Finnie J, Christou C, Williams GK, Walls A, Frantzis P, Adams M, Edwards J, Worthington MG, Beltrame J. The susceptibility of the aortic root: porcine aortic rupture testing under cardiopulmonary bypass. J Cardiothorac Surg 2021; 16:283. [PMID: 34602088 PMCID: PMC8489069 DOI: 10.1186/s13019-021-01667-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 09/20/2021] [Indexed: 11/30/2022] Open
Abstract
Background In our earlier study on the functional limits of the aneurysmal aortic root we determined the pig root is susceptible to failure at high aortic pressures levels. We established a pig rupture model using cardiopulmonary bypass to determine the most susceptible region of the aortic root under the highest pressures achievable using continuous flow, and what changes occur in these regions on a macroscopic and histological level. This information may help guide clinical management of aortic root and ascending aorta pathology.
Methods Five pigs underwent 4D flow MRI imaging pre surgery to determine vasopressor induced wall sheer stress and flow parameters. All pigs were then placed on cardiopulmonary bypass (CPB) via median sternotomy, and maximal aortic root and ascending aorta flows were initiated until rupture or failure, to determine the most susceptible region of the aorta. The heart was explanted and analysed histologically to determine if histological changes mirror the macroscopic observations.
Results The magnetic resonance imaging (MRI) aortic flow and wall sheer stress (WSS) increased significantly in all regions of the aorta, and the median maximal pressures obtained during cardiopulmonary bypass was 497 mmHg and median maximal flows was 3.96 L/m. The area of failure in all experiments was the non-coronary cusp of the aortic valve. Collagen and elastin composition (%) was greatest in the proximal regions of the aorta. Collagen I and III showed greatest content in the inner aortic root and ascending aorta regions. Conclusions This unique porcine model shows that the aortic root is most susceptible to failure at high continuous aortic pressures, supported histologically by different changes in collagen content and subtypes in the aortic root. With further analysis, this information could guide management of the aortic root in disease. Supplementary Information The online version contains supplementary material available at 10.1186/s13019-021-01667-9.
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Affiliation(s)
- Timothy Luke Surman
- D'Arcy Sutherland Cardiothoracic Surgical Unit, Royal Adelaide Hospital, Adelaide, SA, Australia.
| | - John Matthew Abrahams
- D'Arcy Sutherland Cardiothoracic Surgical Unit, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - Jim Manavis
- Department of Medical and Health Sciences, University of Adelaide Health Sciences, Adelaide, SA, Australia
| | - John Finnie
- Department of Medical and Health Sciences, University of Adelaide Health Sciences, Adelaide, SA, Australia
| | - Chris Christou
- Preclinical, Imaging, and Research Laboratories, South Australian Health and Medical Research Institute, Gilles Plains, Adelaide, SA, Australia
| | - Georgia Kate Williams
- Preclinical, Imaging, and Research Laboratories, South Australian Health and Medical Research Institute, Gilles Plains, Adelaide, SA, Australia.,National Imaging Facility, Brisbane, Australia
| | - Angela Walls
- Dr Jones and Partners, South Australian Health and Medical Research Institute, Adelaide, SA, Australia
| | - Peter Frantzis
- D'Arcy Sutherland Cardiothoracic Surgical Unit, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - Mark Adams
- D'Arcy Sutherland Cardiothoracic Surgical Unit, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - James Edwards
- D'Arcy Sutherland Cardiothoracic Surgical Unit, Royal Adelaide Hospital, Adelaide, SA, Australia
| | | | - John Beltrame
- D'Arcy Sutherland Cardiothoracic Surgical Unit, Royal Adelaide Hospital, Adelaide, SA, Australia.,Cardiology Department, The Queen Elizabeth Hospital, Adelaide, SA, Australia
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Pesonen E, Passov A, Salminen US, Ilmakunnas M, Vento A, Aittomäki J, Andersson S, Schramko A. Heparin Binding Protein in Adult Heart Surgery. Ann Thorac Surg 2019; 107:1154-1159. [DOI: 10.1016/j.athoracsur.2018.10.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 09/15/2018] [Accepted: 10/01/2018] [Indexed: 11/16/2022]
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4
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Indrebø M, Berg A, Holmstrøm H, Seem E, Guthe HJ, Wiig H, Norgård G. Fluid accumulation after closure of atrial septal defects: the role of colloid osmotic pressure. Interact Cardiovasc Thorac Surg 2018; 26:307-312. [PMID: 29049836 DOI: 10.1093/icvts/ivx334] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 09/13/2017] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES Following paediatric cardiac surgery with cardiopulmonary bypass (CPB), there is a tendency for fluid accumulation. The colloid osmotic pressure of plasma (COPp) and interstitial fluid (COPi) are determinants of transcapillary fluid exchange but only COPp has been measured in sick children. The aim of this study was to assess the net colloid osmotic pressure gradient in children undergoing atrial septal defect closure. METHODS Twenty-three patients had interventional and 18 had surgical atrial septal defect closures. Interstitial fluid was harvested using a wick method before and after surgery with CPB with concomitant blood samples. COP was measured using a colloid osmometer for small fluid samples. Baseline COP was compared with data from healthy children. RESULTS COPp at baseline was 21.9 ± 2.8 and 21.4 ± 2.2 mmHg in the interventional and surgical groups, respectively, and was significantly lower than in healthy children (25.5 ± 3.1 mmHg) (P < 0.001). In the surgical group, the use of CPB significantly reduced COPp to 16.9 ± 2.9 mmHg (P < 0.001) and the colloid osmotic gradient [ΔCOP (COPp - COPi)] to 2.9 ± 3.8 mmHg (P < 0.001) compared with interventional procedure. One hour after the procedure, COPi was 15.6 ± 3.8 mmHg and 9.9 ± 2.1 mmHg (P < 0.001) and the ΔCOP was 5.4 ± 3.0 mmHg and 9.1 ± 3.1 mmHg (P < 0.003) in the interventional and surgical groups, respectively. CONCLUSIONS Baseline COPp and COPi were lower in atrial septal defect patients compared with healthy children. The significantly lower COP gradient during CPB may explain the tendency for more fluid accumulation with pericardial effusion in the surgical group. The increased COP gradient after CPB may represent an oedema-preventive mechanism.
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Affiliation(s)
- Marianne Indrebø
- Department of Pediatrics, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Paediatric Cardiology, Division of Paediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
| | - Ansgar Berg
- Department of Paediatrics, Haukeland University Hospital, Bergen, Norway.,Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Henrik Holmstrøm
- Department of Pediatrics, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Paediatric Cardiology, Division of Paediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
| | - Egil Seem
- Department of Cardiothoracic Surgery, Division of Cardiovascular and Pulmonary Diseases, Oslo University Hospital, Oslo, Norway
| | - Hans Jørgen Guthe
- Department of Paediatrics, Haukeland University Hospital, Bergen, Norway
| | - Helge Wiig
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Gunnar Norgård
- Department of Paediatric Cardiology, Division of Paediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
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Kara A, Akin S, Dos Reis Miranda D, Struijs A, Caliskan K, van Thiel RJ, Dubois EA, de Wilde W, Zijlstra F, Gommers D, Ince C. Microcirculatory assessment of patients under VA-ECMO. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2016; 20:344. [PMID: 27776535 PMCID: PMC5078964 DOI: 10.1186/s13054-016-1519-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 09/30/2016] [Indexed: 12/03/2022]
Abstract
Background Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is an effective technique for providing emergency mechanical circulatory support for patients with cardiogenic shock. VA-ECMO enables a rapid restoration of global systemic organ perfusion, but it has not been found to always show a parallel improvement in the microcirculation. We hypothesized in this study that the response of the microcirculation to the initiation of VA-ECMO might identify patients with increased chances of intensive care unit (ICU) survival. Methods Twenty-four patients were included in this study. Sublingual microcirculation measurements were performed using the CytoCam-IDF (incident dark field) imaging device. Microcirculatory measurements were performed at baseline, after VA-ECMO insertion (T1), 48–72 h after initiation of VA-ECMO (T2), 5–6 days after (T3), 9–10 days after (T4), and within 24 h of VA-ECMO removal. Results Of the 24 patients included in the study population, 15 survived and 9 died while on VA-ECMO. There was no significant difference between the systemic global hemodynamic variables at initiation of VA-ECMO between the survivors and non-survivors. There was, however, a significant difference in the microcirculatory parameters of both small and large vessels at all time points between the survivors and non-survivors. Perfused vessel density (PVD) at baseline (survivor versus non-survivor, 19.21 versus 13.78 mm/mm2, p = 0.001) was able to predict ICU survival on initiation of VA-ECMO; the area under the receiver operating characteristic curve (ROC) was 0.908 (95 % confidence interval 0.772–1.0). Conclusion PVD of the sublingual microcirculation at initiation of VA-ECMO can be used to predict ICU mortality in patients with cardiogenic shock. Electronic supplementary material The online version of this article (doi:10.1186/s13054-016-1519-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Atila Kara
- Department of Intensive Care, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands. .,Department of Intensive Care, Hacettepe University Faculty of Medicine, Ankara, Turkey. .,Department of Intensive Care, Erasmus MC, University Medical Center Rotterdam, Room H-603 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands.
| | - Sakir Akin
- Department of Intensive Care, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands.,Department of Cardiology, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands
| | - Dinis Dos Reis Miranda
- Department of Intensive Care, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands
| | - Ard Struijs
- Department of Intensive Care, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands
| | - Kadir Caliskan
- Department of Cardiology, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands
| | - Robert J van Thiel
- Department of Intensive Care, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands
| | - Eric A Dubois
- Department of Cardiology, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands
| | - Wouter de Wilde
- Department of Cardiothoracic Surgery, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands
| | - Felix Zijlstra
- Department of Cardiology, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands
| | - Diederik Gommers
- Department of Intensive Care, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands
| | - Can Ince
- Department of Intensive Care, Erasmus MC, University Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE, Rotterdam, The Netherlands
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6
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Elvevoll B, Lundemoen S, Svendsen ØS, Mongstad A, Grong K, Kvalheim VL, Husby P. Does Roller Pump-Induced Pulsatile CPB Perfusion Affect Microvascular Fluid Shifts and Tissue Perfusion? Ann Thorac Surg 2016; 102:564-72. [PMID: 27139370 DOI: 10.1016/j.athoracsur.2016.02.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 12/15/2015] [Accepted: 02/01/2016] [Indexed: 10/21/2022]
Abstract
BACKGROUND Pulsatile versus nonpulsatile cardiopulmonary bypass (CPB) perfusion remains debated. Beneficial effects on tissue perfusion, inflammation, and microvascular fluid exchange have been linked to pulsatile perfusion by some investigators and denied by others. This study evaluated fluid extravasation and tissue perfusion during nonpulsatile or pulsatile roller pump-induced CPB perfusion. METHODS Fourteen pigs underwent roller pump-induced pulsatile (n = 7) or nonpulsatile CPB perfusion (n = 7) for 90 minutes. Fluid input/losses, colloid osmotic pressures (plasma/interstitium), hematocrit, serum electrolytes, serum proteins, tissue perfusion, and total tissue water content were measured, and plasma volume and fluid extravasation were calculated. RESULTS Fluid additions/losses, plasma volume, and fluid extravasation changed similarly in both groups during CPB with no between-group differences. Neither was between-group differences observed for tissue perfusion and total tissue water content, with one exception. Total tissue water content of the right (3.92 ± 0.26 versus 4.32 ± 0.28 g/g dry weight) and left ventricle (4.02 ± 0.25 versus 4.33 ± 0.24 g/g dry weight) was lowered in the pulsatile group. CONCLUSIONS No important differences were found between pulsatile and nonpulsatile CPB perfusion for microvascular fluid balance and tissue perfusion.
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Affiliation(s)
- Bjørg Elvevoll
- Department of Anesthesia and Surgical Services, Haukeland University Hospital, Bergen, Norway
| | - Steinar Lundemoen
- Department of Heart Disease, Haukeland University Hospital, Bergen, Norway
| | - Øyvind S Svendsen
- Department of Anesthesia and Surgical Services, Haukeland University Hospital, Bergen, Norway
| | - Arve Mongstad
- Department of Heart Disease, Haukeland University Hospital, Bergen, Norway
| | - Ketil Grong
- Department of Clinical Science, Faculty of Medicine and Dentistry, University of Bergen, Bergen, Norway
| | - Venny L Kvalheim
- Department of Heart Disease, Haukeland University Hospital, Bergen, Norway; Department of Clinical Science, Faculty of Medicine and Dentistry, University of Bergen, Bergen, Norway
| | - Paul Husby
- Department of Anesthesia and Surgical Services, Haukeland University Hospital, Bergen, Norway; Department of Clinical Medicine, Faculty of Medicine and Dentistry, University of Bergen, Bergen, Norway.
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7
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Endothelial hyperpermeability after cardiac surgery with cardiopulmonary bypass as assessed using an in vitro bioassay for endothelial barrier function. Br J Anaesth 2016; 116:223-32. [DOI: 10.1093/bja/aev411] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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8
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Husby P. Reply: To PMID 25499482. Ann Thorac Surg 2015; 100:1512-3. [PMID: 26434473 DOI: 10.1016/j.athoracsur.2015.05.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 05/04/2015] [Accepted: 05/07/2015] [Indexed: 10/23/2022]
Affiliation(s)
- Paul Husby
- Department of Clinical Medicine, University of Bergen, Haukeland University Hospital, Bergen, Norway.
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9
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Lundemoen S, Kvalheim VL, Svendsen ØS, Mongstad A, Andersen KS, Grong K, Husby P. Intraaortic counterpulsation during cardiopulmonary bypass impairs distal organ perfusion. Ann Thorac Surg 2014; 99:619-25. [PMID: 25499482 DOI: 10.1016/j.athoracsur.2014.08.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 08/05/2014] [Accepted: 08/15/2014] [Indexed: 11/28/2022]
Abstract
BACKGROUND Recent studies have focused on the use of fixed-rate intraaortic balloon pumping (IABP) during cardiopulmonary bypass (CPB) to achieve pulsatile flow. Because application of an IABP catheter may represent a functional obstruction within the descending aorta, we explored the effect of IABP-pulsed CPB-perfusion with special attention to perfusion above and below the IABP balloon. METHODS Sixteen animals received an IABP catheter that remained turned off position (NP group, n = 8) or was switched to an automatic mode of 80 beats/min during CPB (PP group, n = 8). Flow-data and pressure-data were obtained above and below the IABP balloon. Tissue perfusion was evaluated by microspheres. RESULTS IABP-pulsed CPB-perfusion, as assessed at 30 minutes on CPB, increased proximal mean aortic pressure (p < 0.05) and carotid artery blood flow (p < 0.001), but decreased distal mean aortic pressure (p < 0.001). The decrease of distal mean aortic pressure in the PP group was associated with a 75 % decrease (p < 0.001) of renal tissue perfusion. During nonpulsed perfusion the respective variables remained essentially unchanged compared with pre-CPB levels. CONCLUSIONS Using IABP as a surrogate to achieve pulsatile perfusion during CPB contributes significantly to lowered aortic pressure in the distal portion of aorta and impaired tissue perfusion of the kidneys. The results are focusing on effects that may contribute to organ dysfunction and acute kidney injury. Consequently, assessment of perfusion pressure distal to the balloon should be addressed whenever IABP is used during CPB.
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Affiliation(s)
- Steinar Lundemoen
- Section for Cardiothoracic Surgery, Department of Heart Disease, Haukeland University Hospital, University of Bergen, Bergen, Norway
| | - Venny Lise Kvalheim
- Section for Cardiothoracic Surgery, Department of Heart Disease, Haukeland University Hospital, University of Bergen, Bergen, Norway; Department of Clinical Science, Haukeland University Hospital, University of Bergen, Bergen, Norway
| | - Øyvind Sverre Svendsen
- Department of Anesthesia and Intensive Care, Haukeland University Hospital, University of Bergen, Bergen, Norway
| | - Arve Mongstad
- Section for Cardiothoracic Surgery, Department of Heart Disease, Haukeland University Hospital, University of Bergen, Bergen, Norway
| | - Knut Sverre Andersen
- Section for Cardiothoracic Surgery, Department of Heart Disease, Haukeland University Hospital, University of Bergen, Bergen, Norway
| | - Ketil Grong
- Department of Clinical Science, Haukeland University Hospital, University of Bergen, Bergen, Norway
| | - Paul Husby
- Department of Anesthesia and Intensive Care, Haukeland University Hospital, University of Bergen, Bergen, Norway; Department of Clinical Medicine, Haukeland University Hospital, University of Bergen, Bergen, Norway.
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