Does leucocyte depletion during cardiopulmonary bypass improve oxygenation indices in patients with mild lung dysfunction?

Association of Acute Systemic Inflammation with Patient-Centric Postoperative Pulmonary Complications After Elective Cardiac Surgery

BACKGROUND

Postoperative pulmonary complications (PPCs) occur frequently after cardiac surgery. Absolute postoperative values of biomarkers of inflammation (interleukin [IL]-6, IL-8, and tumor necrosis factor-alpha [TNF-α]) and alveolar epithelial injury (soluble receptor for advanced glycation end-products [sRAGE]) have been associated with hypoxia and prolonged ventilation. However, relationships between these biomarkers and PPCs, contextualized to preoperative inflammation and perioperative lung injury risk factors, are uncertain. We aimed to determine associations between perioperative increases in biomarkers of inflammation and alveolar epithelial injury with a patient-centric PPC definition in adult cardiac surgical patients, accounting for the influence of intraoperative risk factors for lung injury.

METHODS

Adults undergoing elective cardiac surgery were eligible for this observational cohort study. Blood concentrations of IL-6, IL-8, TNF-α, and sRAGE were collected after anesthesia induction (baseline) and on postoperative day 1 (POD 1). The primary outcome was the occurrence of moderate or severe PPCs, graded using a validated scale, in POD 0 to 7. We estimated the association between POD 1 IL-6, IL-8, TNF-α, and sRAGE concentrations and moderate/severe PPC presence using separate logistic regression models for each biomarker, adjusted for baseline biomarker values and risk factors for postoperative lung injury (age, baseline PaO2/FiO2, left ventricle ejection fraction [LVEF], procedural type, cardiopulmonary bypass duration, and transfusions). Covariables were chosen based on relevance to lung injury and unadjusted between-group differences among patients with versus without PPCs. The secondary outcome was postoperative ventilation duration, which was log-transformed and analyzed using linear regression, adjusted using the same variables as the primary outcome.

RESULTS

We enrolled 204 patients from 2016 to 2018. Biomarkers were analyzed in 2023 among 175 patients with complete data. In adjusted analyses, POD 1 IL-8 and IL-6 were significantly associated with moderate/severe PPCs. The odds ratio (OR) for developing a PPC for every 50 pg/mL increase in POD 1 IL-8 was 7.19 (95% confidence interval [CI], 2.13-28.53, P = .003) and 1.42 (95% CI, 1.13-1.93, P = .01) for every 50 pg/mL increase in POD 1 IL-6. In adjusted analyses, postoperative ventilation duration was significantly associated with POD 1 sRAGE; each 50 pg/mL increase in sRAGE was associated with a 25% (95% CI, 2%-52%, P = .03) multiplicative increase in hours of ventilation. TNF-α was not significantly associated with PPCs or ventilation duration.

CONCLUSIONS

Acute systemic inflammation is significantly associated with PPCs after elective cardiac surgery in adults when taking into consideration preoperative inflammatory burden and perioperative factors that may influence postoperative lung injury.

Strategies to attenuate maladaptive inflammatory response associated with cardiopulmonary bypass

Cardiopulmonary bypass (CPB) initiates an intense inflammatory response due to various factors: conversion from pulsatile to laminar flow, cold cardioplegia, surgical trauma, endotoxemia, ischemia-reperfusion injury, oxidative stress, hypothermia, and contact activation of cells by the extracorporeal circuit. Redundant and overlapping inflammatory cascades amplify the initial response to produce a systemic inflammatory response, heightened by coincident activation of coagulation and fibrinolytic pathways. When unchecked, this inflammatory response can become maladaptive and lead to serious postoperative complications. Concerted research efforts have been made to identify technical refinements and pharmacologic interventions that appropriately attenuate the inflammatory response and ultimately translate to improved clinical outcomes. Surface modification of the extracorporeal circuit to increase biocompatibility, miniaturized circuits with sheer resistance, filtration techniques, and minimally invasive approaches have improved clinical outcomes in specific populations. Pharmacologic adjuncts, including aprotinin, steroids, monoclonal antibodies, and free radical scavengers, show real promise. A multimodal approach incorporating technical, circuit-specific, and pharmacologic strategies will likely yield maximal clinical benefit.

Leukocyte filtration and leukocyte modulation therapy during extracorporeal cardiopulmonary resuscitation in a porcine model of prolonged cardiac arrest

Extracorporeal cardiopulmonary resuscitation (ECPR) is emerging as a feasible and effective rescue strategy for prolonged cardiac arrest (CA). However, prolonged total body ischemia and reperfusion can cause microvascular occlusion that prevents organ reperfusion and recovery of function. One hypothesized mechanism of microvascular "no-reflow" is leukocyte adhesion and formation of neutrophil extracellular traps. In this study we tested the hypothesis that a leukocyte filter (LF) or leukocyte modulation device (L-MOD) could reduce NETosis and improve recovery of heart and brain function in a swine model of prolonged cardiac arrest treated with ECPR. Thirty-six swine (45.5 ± 2.5 kg, evenly distributed sex) underwent 8 min of untreated ventricular fibrillation CA followed by 30 min of mechanical CPR with subsequent 8 h of ECPR. Two females were later excluded from analysis due to CPR complications. Swine were randomized to standard care (Control group), LF, or L-MOD at the onset of CPR. NET formation was quantified by serum dsDNA and citrullinated histone as well as immunofluorescence staining of the heart and brain for citrullinated histone in the microvasculature. Primary outcomes included recovery of cardiac function based on cardiac resuscitability score (CRS) and recovery of neurologic function based on the somatosensory evoked potential (SSEP) N20 cortical response. In this model of prolonged CA treated with ECPR we observed significant increases in serum biomarkers of NETosis and immunohistochemical evidence of microvascular NET formation in the heart and brain that were not reduced by LF or L-MOD therapy. Correspondingly, there were no significant differences in CRS and SSEP recovery between Control, LF, and L-MOD groups 8 h after ECPR onset (CRS = 3.1 ± 2.7, 3.7 ± 2.6, and 2.6 ± 2.6 respectively; p = 0.606; and SSEP = 27.9 ± 13.0%, 36.7 ± 10.5%, and 31.2 ± 9.8% respectively, p = 0.194). In this model of prolonged CA treated with ECPR, the use of LF or L-MOD therapy during ECPR did not reduce microvascular NETosis or improve recovery of myocardial or brain function. The causal relationship between microvascular NETosis, no-reflow, and recovery of organ function after prolonged cardiac arrest treated with ECPR requires further investigation.

The potential of the novel leukocyte removal filter in cardiopulmonary bypass

Cardiopulmonary bypass (CPB) is indispensable for cardiac surgery but leads to systemic inflammatory responses and leukocyte activation, possibly due to blood contact with the surface of the CPB unit, surgical, ischemic reperfusion injury, etc. Systemic inflammatory responses during CPB result in increased morbidity and mortality. Activation of leukocytes is an important part of this process and directly contributes to coagulopathy and hemorrhage. This inflammatory response may contribute to the development of postoperative complications, including myocardial dysfunction, respiratory failure, renal and neurologic dysfunction, altered liver function and ultimately, multiple organ failure. Various pharmacologic and mechanical strategies have been developed to minimize the systemic inflammatory response during CPB. For example, leukocyte removal filters were developed in the 1990s for incorporation into the CPB circuit. However, studies of this approach have yielded conflicting findings. The purpose of this was to review the studies of a novel leukocyte removal filter in patients undergoing CPB.

Pulmonary Protection Strategies in Cardiac Surgery: Are We Making Any Progress?

Pulmonary dysfunction is a common complication of cardiac surgery. The mechanisms involved in the development of pulmonary dysfunction are multifactorial and can be related to the activation of inflammatory and oxidative stress pathways. Clinical manifestation varies from mild atelectasis to severe respiratory failure. Managing pulmonary dysfunction postcardiac surgery is a multistep process that starts before surgery and continues during both the operative and postoperative phases. Different pulmonary protection strategies have evolved over the years; however, the wide acceptance and clinical application of such techniques remain hindered by the poor level of evidence or the sample size of the studies. A better understanding of available modalities and/or combinations can result in the development of customised strategies for the different cohorts of patients with the potential to hence maximise patients and institutes benefits.

Pulmonary complications of cardiopulmonary bypass

Pulmonary complications after the use of extracorporeal circulation are common, and they range from transient hypoxemia with altered gas exchange to acute respiratory distress syndrome (ARDS), with variable severity. Similar to other end-organ dysfunction after cardiac surgery with extracorporeal circulation, pulmonary complications are attributed to the inflammatory response, ischemia-reperfusion injury, and reactive oxygen species liberated as a result of cardiopulmonary bypass. Several factors common in cardiac surgery with extracorporeal circulation may worsen the risk of pulmonary complications including atelectasis, transfusion requirement, older age, heart failure, emergency surgery, and prolonged duration of bypass. There is no magic bullet to prevent or treat pulmonary complications, but supportive care with protective ventilation is important. Targets for the prevention of pulmonary complications include mechanical, surgical, and anesthetic interventions that aim to reduce the contact activation, systemic inflammatory response, leukocyte sequestration, and hemodilution associated with extracorporeal circulation.

Anesthetic Management for Cardiopulmonary Bypass

Cardiopulmonary bypass has revolutionized the practice of cardiac surgery and allows safe conduct of increasingly complex cardiac surgery. A brief review of the bypass circuit is undertaken in this review. A more thorough review of the anesthetic management is accomplished including choice of anesthetic medications and their effects. The inflammatory response to cardiopulmonary bypass is reviewed along with interventions that may help ameliorate the inflammation.

Leukocyte depletion during cardiopulmonary bypass in routine adult cardiac surgery

OBJECTIVES

Cardiopulmonary bypass (CPB) elicits an inflammatory response which is potentially harmful and that is partly caused by activation of leukocytes. Despite promise from earlier studies, however, the value of intraoperative leukocyte-depletion (LD) remains equivocal. We studied the effect of LD during routine cardiac surgery.

METHODS

For a short period (2.5 months), all operations at our institution were performed with leukocyte filters (Pall, East Hills, NY, USA) in the arterial and cardioplegia lines of the CPB. Those patients operated immediately before and after this period served as controls.

RESULTS

In each group, 266 predominantly male (70%) patients were studied. A broad spectrum of operations including emergency surgery was evaluated, which was comparable between the groups (P=0.41). There were no significant differences regarding the preoperative data, but the preoperative leukocyte count tended to be lower in the leukodepletion-group (7961±2415 vs. 8444±2951, P=0.050). Despite this, no difference between the groups regarding the postoperative leukocyte count was observed. Significantly more LD-patients were extubated within 12 h postoperatively (69% vs. 60% in the control-group, P=0.029), but there were no significant differences regarding 30-day mortality (0.4% vs. 1.1%, P=0.37), transfusion requirements or major morbidity.

CONCLUSIONS

In a retrospective study on adding LD filters to all cardiac operations with CPB in adults, we did not observe a clear benefit of intraoperative LD with the strategy used (continuous filtration plus filtration of cardioplegia).

Strategies to prevent intraoperative lung injury during cardiopulmonary bypass

During open heart surgery the influence of a series of factors such as cardiopulmonary bypass (CPB), hypothermia, operation and anaesthesia, as well as medication and transfusion can cause a diffuse trauma in the lungs. This injury leads mostly to a postoperative interstitial pulmonary oedema and abnormal gas exchange. Substantial improvements in all of the above mentioned factors may lead to a better lung function postoperatively. By avoiding CPB, reducing its time, or by minimizing the extracorporeal surface area with the use of miniaturized circuits of CPB, beneficial effects on lung function are reported. In addition, replacement of circuit surface with biocompatible surfaces like heparin-coated, and material-independent sources of blood activation, a better postoperative lung function is observed. Meticulous myocardial protection by using hypothermia and cardioplegia methods during ischemia and reperfusion remain one of the cornerstones of postoperative lung function. The partial restoration of pulmonary artery perfusion during CPB possibly contributes to prevent pulmonary ischemia and lung dysfunction. Using medication such as corticosteroids and aprotinin, which protect the lungs during CPB, and leukocyte depletion filters for operations expected to exceed 90 minutes in CPB-time appear to be protective against the toxic impact of CPB in the lungs. The newer methods of ultrafiltration used to scavenge pro-inflammatory factors seem to be protective for the lung function. In a similar way, reducing the use of cardiotomy suction device, as well as the contact-time between free blood and pericardium, it is expected that the postoperative lung function will be improved.

Cryopreserved arterial allograft reconstruction after excision of thoracic malignancies

BACKGROUND

The purpose of this study was to evaluate the long-term clinical and immunologic outcome of cryopreserved arterial allograft (CAA) revascularization of intrathoracic vessels invaded by malignancies.

METHODS

Since January 2002, consecutive patients whose intrathoracic vessels were invaded by malignancies were operated on and revascularizion made using human lymphocyte antigen (HLA)- and ABO-mismatched CAAs. Immunologic studies were performed preoperatively, and 1, 3, 6, 12, and 24 months postoperatively. Postoperative oral anticoagulation therapy was not given.

RESULTS

Twenty-six patients aged 53.1 +/- 15 years with a nonsmall-cell lung cancer (n = 10), invasive mediastinal tumors (n = 7), pulmonary artery sarcoma (n = 3), laryngeal (n = 2), or other rare lung neoplasms (n = 4) underwent operation. Cardiopulmonary bypass was used in 10 cases (38%), and all resections were pathologically complete. Revascularization was either for venous (n = 12) or arterial (n = 14) vessels, and a total of 30 allografts revascularized the superior vena cava (n = 6), pulmonary artery (n = 7), innominate vein (n = 3) or artery (n = 2), ascendent (n = 4) or descending (n = 1) aorta, and subclavian vein (n = 3) or artery (n = 4). Hospital morbidity and mortality were 50% (n = 13) and 3.8% (n = 1), respectively, all CAA unrelated. With a median follow-up of 18 months (range, 3 to 60+), 5-year survival and allograft patency were 84% and 95%, respectively. Preoperative anti-HLA antibodies were detected in 2 patients (7.7%) and a postoperative anti-HLA antibody response, clinically irrelevant, in 1 of 24 patients (4%).

CONCLUSIONS

Revascularization of intrathoracic venous and arterial vessels in patients with malignancies using HLA- and ABO-mismatched CAA is technically feasible and clinically attractive because of no infection risk and postoperative anticoagulation, and excellent long-term survival, patency, and nonimmunogeneicity.

The effects of various leukocyte filtration strategies in cardiac surgery

It is known that cardiopulmonary bypass causes an inflammatory reaction with an associated morbidity and mortality. Several anti-inflammatory strategies have been implemented to reduce this response, including leukocyte removal from the circulation using specialised filters. The aim of this study is to systematically review the available evidence on leukocyte filtration in cardiac surgery, focusing on its effect on systemic inflammation and whether this has influenced clinical outcomes. Five electronic databases were systematically searched for studies reporting the effect of leukocyte filtration at any point within the cardiopulmonary bypass circuit in humans. Reference lists of all identified studies were checked for any missing publications. Two authors independently extracted the data from the included studies. Whilst systemic leukodepleting filters do not appear to consistently lower leukocyte counts, they may preferentially remove activated leukocytes. Small improvements in early post-operative lung function in patients receiving systemic leukodepletion have been reported, but this does not lead to reduced hospital stay or decreased mortality. There is substantial evidence that cardioplegic leukocyte filtration attenuates the reperfusion injury at a cellular level, but this has not been translated into clinical improvements. Finally, whilst various strategies involving multiple leukocyte filters, or the incorporation of pharmacological agents into leukocyte-depleting protocols have been evaluated, the current available results are not conclusive. Our study suggests that there is not enough high quality or consistent evidence to draw guidelines regarding the use of leukocyte-depleting filters within routine cardiac surgical practice.

Changes in muscle compartment pressure after cardiopulmonary bypass

PURPOSE

Hemodilution and inflammation lead to edema and increased muscle compartment pressure after cardiac surgery. The aim of this study was to find whether muscle compartment pressure was affected by the addition of albumin and mannitol to the pump prime, heparin coating or leukocyte depletion. Additionally, we studied the relationship between intraocular pressure and lower leg muscle compartment pressure. Edema during and following cardiac surgery is due to hemodynamic, osmotic and inflammatory changes, according to Starling's Law. We attempted to influence the osmotic balance and reduce the inflammatory response in order to reduce the edema.

METHODS

Thirty-six patients who underwent cardiac surgery were randomly allocated into four groups. Group A received albumin and mannitol into the pump prime. Group B had an, heparin-coated perfusion system, Group C had a leukocyte-depletion arterial line filter and Group D was the control group, where intraocular pressure was also measured.

RESULTS

Lower leg muscle compartment pressure increased significantly during and after cardiac surgery in all groups, but this increase was significantly less in Group A than in the control group 24 h after surgery. No correlation was found between muscular compartment pressure and intraocular pressure. The intraocular pressure profile is different from the muscular compartment pressure and recovers much faster.

CONCLUSION

Lower leg muscle compartment pressure and intraocular pressure behave differently during and after cardiac surgery. Albumin and mannitol added to the pump prime decreases muscle compartment pressure after cardiac surgery.