Cardiopulmonary bypass: development of John Gibbon's heart-lung machine

[Peripheral extracorporeal membrane oxygenation in perioperative medicine : Principles, indications and challenges]

In recent years the number of patients treated in intensive care units by extracorporeal membrane oxygenation (ECMO) due to severe respiratory failure or cardiogenic shock has steadily increased [1]. Consequently, the number of invasive procedures and operations in these patients has also increased. A fundamental understanding of these systems and the clinical indications is therefore helpful for the practicing (non-cardiac) surgeon. This review article focuses on peripheral ECMO procedures: venovenous (V-V) ECMO for patients with respiratory failure and venoarterial (V-A) ECMO for circulatory support in cardiogenic shock.

Cardioprotection in cardiovascular surgery

Since the invention of cardiopulmonary bypass, cardioprotective strategies have been investigated to mitigate ischemic injury to the heart during aortic cross-clamping and reperfusion injury with cross-clamp release. With advances in cardiac surgical and percutaneous techniques and post-operative management strategies including mechanical circulatory support, cardiac surgeons are able to operate on more complex patients. Therefore, there is a growing need for improved cardioprotective strategies to optimize outcomes in these patients. This review provides an overview of the basic principles of cardioprotection in the setting of cardiac surgery, including mechanisms of cardiac injury in the context of cardiopulmonary bypass, followed by a discussion of the specific approaches to optimizing cardioprotection in cardiac surgery, including refinements in cardiopulmonary bypass and cardioplegia, ischemic conditioning, use of specific anesthetic and pharmaceutical agents, and novel mechanical circulatory support technologies. Finally, translational strategies that investigate cardioprotection in the setting of cardiac surgery will be reviewed, with a focus on promising research in the areas of cell-based and gene therapy. Advances in this area will help cardiologists and cardiac surgeons mitigate myocardial ischemic injury, improve functional post-operative recovery, and optimize clinical outcomes in patients undergoing cardiac surgery.

Effect of cardiopulmonary bypass on plasma and erythrocytes oxylipins

BACKGROUND

Oxylipins, the oxidative metabolites of polyunsaturated fatty acids (PUFAs), serve as key mediators of oxidative stress, inflammatory responses, and vasoactive reactions in vivo. Our previous work has established that hemodialysis affects both long chain fatty acids (LCFAs) and oxylipins in plasma and erythrocytes to varying degrees, which may be responsible for excess cardiovascular complications in end-stage renal disease. In this study, we aimed to determine changes in blood oxylipins during cardiopulmonary bypass (CPB) in patients undergoing cardiac surgery to identify novel biomarkers and potential metabolites of CPB-related complications. We tested the hypothesis that CPB would differentially affect plasma oxylipins and erythrocytes oxylipins.

METHODS

We conducted a prospective observational study of 12 patients undergoing elective cardiac surgery with expected CPB procedure. We collected venous and arterial blood samples before CPB, 15 and 45 min after the start of CPB, and 60 min after the end of CPB, respectively. Oxylipins profiling in plasma and erythrocytes was achieved using targeted HPLC-MS mass spectrometry.

RESULTS

Our results revealed that most venous plasma diols and hydroxy- oxylipins decreased after CPB initiation, with a continuous decline until the termination of CPB. Nevertheless, no statistically significant alterations were detected in erythrocytes oxylipins at all time points.

CONCLUSIONS

CPB decreases numerous diols and hydroxy oxylipins in blood plasma, whereas no changes in erythrocytes oxylipins are observed during this procedure in patients undergoing cardiac surgery. As lipid mediators primarily responsive to CPB, plasma diols and hydroxy oxylipins may serve as potential key biomarkers for CPB-related complications.

Effect of mechanical ventilation during cardiopulmonary bypass on end-expiratory lung volume in the perioperative period of cardiac surgery: an observational study

BACKGROUND

Many studies explored the impact of ventilation during cardiopulmonary bypass (CPB) period with conflicting results. Functional residual capacity or End Expiratory Lung Volume (EELV) may be disturbed after cardiac surgery but the specific effects of CPB have not been studied. Our objective was to compare the effect of two ventilation strategies during CPB on EELV.

METHODS

Observational single center study in a tertiary teaching hospital. Adult patients undergoing on-pump cardiac surgery by sternotomy were included. Maintenance of ventilation during CPB was left to the discretion of the medical team, with division between "ventilated" and "non-ventilated" groups afterwards. Iterative intra and postoperative measurements of EELV were carried out by nitrogen washin-washout technique. Main endpoint was EELV at the end of surgery. Secondary endpoints were EELV one hour after ICU admission, PaO₂/FiO₂ ratio, driving pressure, duration of mechanical ventilation and post-operative pulmonary complications.

RESULTS

Forty consecutive patients were included, 20 in each group. EELV was not significantly different between the ventilated versus non-ventilated groups at the end of surgery (1796 ± 586 mL vs. 1844 ± 524 mL, p = 1) and one hour after ICU admission (2095 ± 562 vs. 2045 ± 476 mL, p = 1). No significant difference between the two groups was observed on PaO₂/FiO₂ ratio (end of surgery: 339 ± 149 vs. 304 ± 131, p = 0.8; one hour after ICU: 324 ± 115 vs. 329 ± 124, p = 1), driving pressure (end of surgery: 7 ± 1 vs. 8 ± 1 cmH₂O, p = 0.3; one hour after ICU: 9 ± 3 vs. 9 ± 3 cmH₂O), duration of mechanical ventilation (5.5 ± 4.8 vs 8.2 ± 10.0 h, p = 0.5), need postoperative respiratory support (2 vs. 1, p = 1), occurrence of pneumopathy (2 vs. 0, p = 0.5) and radiographic atelectasis (7 vs. 8, p = 1).

CONCLUSION

No significant difference was observed in EELV after cardiac surgery between not ventilated and ventilated patients during CPB.

Acute Massive and Submassive Pulmonary Embolism: Historical Considerations/Surgical Techniques of Pulmonary Embolectomy/Novel Applications in Donor Lungs with Pulmonary Emboli

Pulmonary embolectomy has a chequered history but the quest to surgically treat a patient diagnosed with pulmonary embolism effectively spurred the development of cardiopulmonary bypass and a new dawn for cardiac surgery. The advent of cardiopulmonary bypass, extracorporeal membrane oxygenation, and computed tomography pulmonary angiogram has allowed rapid diagnosis and made surgical pulmonary embolectomy a relatively safe procedure that should be considered when indicated. Pulmonary emboli in donor lungs, often get rejected for transplantation. Ex vivo lung perfusion is among newly available technology with the ability to not only recondition marginal lungs but also treat donor lung pulmonary embolisms, effectively increasing the donor pool.

A Meta-Analysis of Early, Mid-term and Long-Term Mortality of On-Pump vs. Off-Pump in Redo Coronary Artery Bypass Surgery

We aimed to compare the early, mid-term, and long-term mortality between on-pump vs. off-pump redo coronary artery bypass grafting (CABG). We conducted a systematic search for studies comparing clinical outcomes of patients who underwent on-pump vs. off-pump redo CABG. We pooled the relevant studies quantitatively to compare the early (perioperative period, whether in hospital or within 30 days after discharge), mid-term (≥1 year and <5 years), and long-term (≥5 year) mortality of on-pump vs. off-pump redo CABG. A random-effect model was applied when there was high heterogeneity (I2 > 50%) between studies. Otherwise, a fixed-effect model was utilized. After systematic literature searching, 22 studies incorporating 5,197 individuals (3,215 in the on-pump group and 1,982 in the off-pump group) were identified. A pooled analysis demonstrated that compared with off-pump redo CABG, on-pump redo CABG was associated with higher early mortality (OR 2.11, 95%CI: 1.54-2.89, P < 0.00001). However, no significant difference was noted in mid-term mortality (OR 1.12, 95%CI: 0.57-2.22, P = 0.74) and long-term mortality (OR 1.12, 95%CI: 0.41-3.02, P = 0.83) between the two groups. In addition, the complete revascularization rate was higher in the on-pump group than the off-pump group (OR 2.61, 95%CI: 1.22-5.60, P = 0.01). In conclusion, the off-pump technique is a safe and efficient alternative to the on-pump technique, with early survival advantage and similar long-term mortality to the on-pump technique in the setting of redo CABG, especially in high-risk patients.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42021244721.

Machine Perfusion of the Human Heart

This brief communication about machine perfusion of potential human donor hearts describes its historical development. Included in the review are both the isolated perfusion of donor hearts retrieved from heart beating and non-heart-beating donors. Additionally, some detail of in-situ (within the donor body) normothermic regional reperfusion of the heart and other organs is given. This only applies to the DCD donor heart. Similarly, some detail of ex-situ (outside the body) heart perfusion is offered. This article covers the entire history of the reperfusion of donor hearts. It takes us up to the current day describing 6 years follow-up of these donor machine perfused hearts. These clinical results appear similar to the outcomes of heart beating donors if reperfusion is managed within 30 min of normothermic circulatory determined death. Future developments are also offered. These are 3-fold and include: i. the pressing need for objective markers of the clinical outcome after transplantation, ii. the wish for isolated heart perfusion leading to improvement in donor heart quality, and iii. a strategy to safely lengthen the duration of isolated heart perfusion.

Inflammation and Oxidative Stress in the Context of Extracorporeal Cardiac and Pulmonary Support

Extracorporeal circulation (ECC) systems, including cardiopulmonary bypass, and extracorporeal membrane oxygenation have been an irreplaceable part of the cardiothoracic surgeries, and treatment of critically ill patients with respiratory and/or cardiac failure for more than half a century. During the recent decades, the concept of extracorporeal circulation has been extended to isolated machine perfusion of the donor organ including thoracic organs (ex-situ organ perfusion, ESOP) as a method for dynamic, semi-physiologic preservation, and potential improvement of the donor organs. The extracorporeal life support systems (ECLS) have been lifesaving and facilitating complex cardiothoracic surgeries, and the ESOP technology has the potential to increase the number of the transplantable donor organs, and to improve the outcomes of transplantation. However, these artificial circulation systems in general have been associated with activation of the inflammatory and oxidative stress responses in patients and/or in the exposed tissues and organs. The activation of these responses can negatively affect patient outcomes in ECLS, and may as well jeopardize the reliability of the organ viability assessment, and the outcomes of thoracic organ preservation and transplantation in ESOP. Both ECLS and ESOP consist of artificial circuit materials and components, which play a key role in the induction of these responses. However, while ECLS can lead to systemic inflammatory and oxidative stress responses negatively affecting various organs/systems of the body, in ESOP, the absence of the organs that play an important role in oxidant scavenging/antioxidative replenishment of the body, such as liver, may make the perfused organ more susceptible to inflammation and oxidative stress during extracorporeal circulation. In the present manuscript, we will review the activation of the inflammatory and oxidative stress responses during ECLP and ESOP, mechanisms involved, clinical implications, and the interventions for attenuating these responses in ECC.

Predictors of aortic clamp time duration and intensive care unit length of stay in elective adult cardiac surgery

Background

Aortic cross-clamp utilized during cardiac surgery facilitates motionless and bloodless surgical field. However, the duration of clamp time has an inverse effect on early post-operative recovery period. In this study, we sought to examine the predictors of aortic clamp duration and intensive care unit length of stay.

Results

Six hundred and nine adult patients presented for elective cardiac surgery between December 2019 and December 2020 were enrolled. The age of patients ranged from 18 to 82 years (mean 55.62 years, SD ± 12.3 years). Male/female ratio is 4.6:1. Most patients (87.2%) were planned for coronary artery bypass grafting (CABG) and 78 patients (12.8%) for single heart valve procedure. Operative time (OT) ranged from 120 to 402 min and averaged 259.4 min (SD ± 45.9 min). ACC time ranged from 15 to 159 min and averaged 50.56 min (SD ± 19.4 min). Factors associated with significantly longer ACCT were: smoking (OR = 1.89 (95% CI 1.3–2.74), p value = 0.01), respiratory disease (OR = 0.48 (95% CI 0.24–0.96), p value = 0.039), obesity (OR = 1.76 (95% CI 1.18–2.63), p value = 0.005) and AVR (OR = 2.11 (95% CI 1.17–3.83), p value = 0.013). Low cardiac output syndrome (LCOS) was observed in 19.2% of patients. Longer than average ACCT was associated with increased use of inotropes (p value < 0.001), intra-aortic balloon pump (p value < 0.001) and first 24 h post-operative blood loss (p value < 0.001). The average intensive care unit length of stay (ICULOS) was 1.64 days (SD ± 1.1 days). Patients' ACCT converged positively and significantly on ICULOS (Beta coefficient = 1.013 (95% CI 1.01–1.015), p value < 0.001).

Conclusion

Aortic cross-clamping is a crucial method in cardiac surgery to achieve motionless field; however, prolongation of this method had an incremental risks for the development of low cardiac output syndrome, increased first 24 h post-operative blood loss and longer stay in the intensive care unit.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43044-021-00195-0.

A Cardiac Protection of Germinated Brown Rice During Cardiopulmonary Bypass Surgery and Simulated Myocardial Ischemia

Purpose

The potential cardio-protective property of germinated brown rice (GBR) has been revealed by ameliorating risk factors related to cardiovascular diseases. This study hypothesized that the combination of GBR and cardioplegic solution could protect the cardiomyocytes exposed to simulated ischemic reperfusion injury in vitro study and preserve cardiac function during cardiopulmonary bypass surgery in animal models.

Methods

Primary porcine cardiomyocytes were isolated and experimented cell viability against simulated ischemic reperfusion injury. In a cardiac surgical animal model, six pigs were randomly assigned to receive the two types of cardioplegic solution: i) St. Thomas cardioplegic solution (20 cc/kg); and ii) St. Thomas cardioplegic solution plus GBR (1 mg/kg). During open-heart surgery, the aorta was cross-clamped for 20 minutes, followed by reperfusion for 1 hour. Cardiopulmonary bypass parameters were recorded until the end of the procedure. Furthermore, hemodynamic parameters and arterial blood gas characteristics of animals among groups were monitored at different time points, including baseline before cardiopulmonary bypass (T1), during cardiopulmonary bypass (T2), during aortic clamp on (T3), and aortic clamp off (T4).

Results

Primarily, GBR cotreatment with cardioplegic solution essentially resulted in the improvement of cell viability in primary porcine cardiomyocytes against simulated ischemic reperfusion induction. The findings from cardiac surgery demonstrated that mean arterial pressure and heart rate are constantly stable in cardioplegic solution combined with the GBR group, while the trend of potassium and lactase concentration was decreased in the animals receiving GBR group. Consistently, all parameters from arterial blood gas showed better outcomes in animals receiving GBR; however, there were no statistically significant differences between groups, except hepatic enzymes.

Conclusion

Therefore, GBR might exert cardio-protective effects against ischemic reperfusion injury in the porcine cardiac surgery model due to anti-inflammatory response. These protective actions of GBR may explain the benefits gained from applying GBR products as a possible therapeutic supplement on cardiac diseases.

A novel roller pump for physiological flow

Having physiological correct flow waveforms is a key feature for experimental studies of blood flow, especially in the process of developing and testing a new medical device such as stent, mechanical heart valve, or any implantable medical device that involves circulation of blood through the device. It is also a critical part of a perfusion system for cardiopulmonary bypass and extracorporeal membrane oxygenation procedures. This study investigated the feasibility of a novel roller pump for use in experimental flow phantoms. Flow rates of carotid flow profile measured directly with the ultrasonic flow meter matched well with the reference flow rates programmed into the machine with similarity index of 0.97 and measured versus programmed flow rates at specific time‐points of peak systolic velocity (PSV): 0.894 vs 0.880, end systolic velocity (ESV): 0.333 vs 0.319, and peak diastolic velocity (PDV): 0.514 vs 0.520 L/min. Flow rates derived from video analysis of the pump motion for carotid, suprarenal, and infrarenal flows also matched well with references with similarity indices of 0.99, 0.99, and 0.96, respectively. Measured flow rates (mean/standard deviation) at PSV, ESV, and PDV time‐points for carotid: 0.883/0.016 vs 0.880, 0.342/0.007 vs 0.319, and 0.485/0.009 vs 0.520; suprarenal: 3.497/0.014 vs 3.500, 0.004/0.003 vs 0, and 1.656/0.073 vs 1.453; infrarenal: 4.179/0.024 vs 4.250, −1.147/0.015 vs −1.213, and 0.339/0.017 vs 0.391 L/min, respectively. The novel roller pump is suitable for benchtop testing of physiological flow.

Younger age is associated with greater early neurocognitive decline postcardiopulmonary bypass

Objective

To examine the effect of aging on postoperative neurocognitive decline (NCD) in cardiac surgery patients.

Methods

Patients undergoing coronary artery bypass graft or open aortic valve replacement were administered the Repeatable Battery for the Assessment of Neuropsychological Status at preoperative, postoperative day (POD) 4, and 1 month. Blood samples were collected at preoperative, 6 hours postoperative, and POD 4. Plasma interleukin (IL)-6, tumor necrosis factor-α, and C-reactive protein (CRP) levels were quantified. Quality of life was measured with the 12-Item Short Form Health Survey. Data were analyzed using paired ratio and unpaired t tests with Welch's correction, and linear regression for cytokine levels.

Results

NCD occurred in 15 patients (N = 33, 45.5%). Dichotomized at age extremes (<60 years; ≥75 years), youngest patients had greater preoperative scores (P = .02) with lower scores by POD 4 (P = .03). There was no NCD in the oldest patients, and scores were not different between age groups on POD 4 (P = .08). Regression at 1 month showed NCD scores again declined by age (n = 15), with younger scores returning toward baseline (P = .008). Regression analyses showed decline by age at 6 hours postoperative and POD 4 in plasma CRP levels (P = .05 6 hours, P = .02 POD 4). Dichotomizing IL-6 levels by age (<70 years, ≥70 years) demonstrated that levels were greater in younger versus older patients at 6 hours postoperative (P = .03), but not on POD 4.

Conclusions

Younger patients tend to have better cognitive scores before surgery but scores at POD 4 are similar to those of older patients, with this trend disappearing at 1 month. IL-6 and CRP upregulation is greater in younger patients, suggesting that a robust perioperative inflammatory response may be associated with reduction in neurocognitive function, and this may be greater in younger versus older patients.

Options in extracorporeal support of multiple organ failure

Multiorgan failure is among the most frequent reasons of death in critically ill patients. Based on extensive and long-term use of renal replacement therapy, extracorporeal organ support became available for other organ failures. Initially, most of these techniques (e.g. extracorporeal membrane oxygenation, extracorporeal CO₂ removal [ECCO2R] and extracorporeal liver support) were used as stand-alone single organ support systems. Considering multiple interactions between native organs (“crosstalk”), combined or integrated extracorporeal organ support (ECOS) devices are intriguing. The concept of multiple organ support therapy (MOST) providing simultaneous and combined support for different failing organs was described more than 15 years ago by Ronco and Bellomo. This concept also implicates overcoming the “compartmentalized” approach provided by different single organ specialized professionals by a multidisciplinary and multiprofessional strategy. The idea of MOST is supported by the failure of several recent studies on single organ support including liver and lung support. Improvement of outcome by ECOS necessarily depends on optimized patient selection, integrated organ support and limitation of its side effects. This implicates challenges for engineers, industry and healthcare professionals. From a technical viewpoint, modular combination of pre-existing technologies such as renal replacement, albumin-dialysis, ECCO2R and potentially cytokine elimination can be considered as a first step. While this allows for stepwise and individual combination of standard organ support facilities, it carries the disadvantage of large extracorporeal blood volume and surfaces as well as additive costs. The more intriguing next step is an integrated platform providing the capacity of multiple organ support within one device. (This article is freely available.)

Numerical Investigation of Blood Flow Characteristics through Cannulated Aorta

Cannulation of the aorta is done in order to provide oxygenation and circulatory function through the use of the heart lung machine during cardio-pulmonary bypass (CPB). The nature of the blood flow through the aorta and its ramifications during CPB is mostly linear as compared to the physiological flow, which is pulsatile in nature. This leads to the development of multiple morbidities caused by the development of emboli and atheromas. Perioperative postoperative care is necessitated by these conditions. As such the understanding of the blood flow characteristics is necessitated in order to effectively prevent the formation of emboli and to prevent the "Sandblasting" effect. The authors in this work seek to investigate the nature of blood flow through the aorta under such circumstances. The results obtained show the nature of blood flow in the cannulated aorta as well as the optimum angle of placement of the cannula with respect to the aortic wall.

Low tidal volume mechanical ventilation against no ventilation during cardiopulmonary bypass heart surgery (MECANO): study protocol for a randomized controlled trial

Background

Postoperative pulmonary complications are a leading cause of morbidity and mortality after cardiac surgery. There are no recommendations on mechanical ventilation associated with cardiopulmonary bypass (CPB) during surgery and anesthesiologists perform either no ventilation (noV) at all during CPB or maintain low tidal volume (LTV) ventilation. Indirect evidence points towards better pulmonary outcomes when LTV is performed but no large-scale prospective trial has yet been published in cardiac surgery.

Design

The MECANO trial is a single-center, double-blind, randomized, controlled trial comparing two mechanical ventilation strategies, noV and LTV, during cardiac surgery with CPB. In total, 1500 patients are expected to be included, without any restrictions. They will be randomized between noV and LTV on a 1:1 ratio. The noV group will receive no ventilation during CPB. The LTV group will receive 5 breaths/minute with a tidal volume of 3 mL/kg and positive end-expiratory pressure of 5 cmH2O. The primary endpoint will be a composite of all-cause mortality, early respiratory failure defined as a ratio of partial pressure of oxygen/fraction of inspired oxygen <200 mmHg at 1 hour after arrival in the ICU, heavy oxygenation support (defined as a patient requiring either non-invasive ventilation, mechanical ventilation or high-flow oxygen) at 2 days after arrival in the ICU or ventilator-acquired pneumonia defined by the Center of Disease Control. Lung recruitment maneuvers will be performed in the noV and LTV groups at the end of surgery and at arrival in ICU with an insufflation at +30 cmH20 for 5 seconds. Secondary endpoints are those composing the primary endpoint with the addition of pneumothorax, CPB duration, quantity of postoperative bleeding, red blood cell transfusions, revision surgery requirements, length of stay in the ICU and in the hospital and total hospitalization costs. Patients will be followed until hospital discharge.

Discussion

The MECANO trial is the first of its kind to compare in a double-blind design, a no-ventilation to a low-tidal volume strategy for mechanical ventilation during cardiac surgery with CPB, with a primary composite outcome including death, respiratory failure and postoperative pneumonia.

Trial registration

ClinicalTrials.gov, NCT03098524. Registered on 27 February 2017.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2321-9) contains supplementary material, which is available to authorized users.