Does the duration of cardiopulmonary bypass or aortic cross-clamp, in the absence of blood and/or blood product administration, influence the IL-6 response to cardiac surgery?

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.

Concomitant cardiac surgery procedures during left ventricular assist device implantation: single-centre experience

Background

Additional cardiac pathologies including tricuspid or mitral valve regurgitation are common in left ventricular assist device (LVAD) recipients and whether to address them remains controversial. We present our institutional outcomes of concomitant cardiac procedures, other than temporary right ventricular (RV) support, at the time of LVAD implantation.

Methods

From 03/2006 to 06/2020, 352 adult patients {median age 60 [interquartile range (IQR): 52-66] years; INTERMACS level 1 29%; INTERMACS level 2 17%; INTERMACS level 3 23%, INTERMACS level 4-6 31%; male 86%} underwent continuous-flow LVAD [Medtronic HVAD^® (HVAD) 50%; Abbott HeartMate II^TM (HMII) 17%; Abbott HeartMate 3^TM (HM3) 33%] implantation. Concomitant valvular procedures were performed in 86 patients (24%) and the majority of patients received the LVAD as bridge to candidacy (BTC) for transplant (74%). Primary study endpoints were short- and mid-term mortality, as well as need for temporary RV support.

Results

Tricuspid valve annuloplasty was the most frequent concomitant procedure (77%), followed by aortic valve replacements (AVRs) or Park's stitch (33%). Temporary RV support was common in the study cohort (35%) using either extracorporeal life support (ECLS, 37%) or a temporary RV assist device (RVAD, 63%). A less invasive (LIS) implantation technique was pursued in 12%. Thirty-day mortality was comparable between those with and without concomitant surgery (4% vs. 6%, P=0.426). In-hospital mortality was significantly higher for additional interventions (22% vs. 14%, P=0.05), whereas one-year survival was similar (71% vs. 79%, P=0.106).

Conclusions

Concomitant cardiac procedures, especially tricuspid and aortic valve surgery, are frequent but are associated with a higher perioperative morbidity and mortality.

Echocardiographically Measured Epicardial Fat Predicts New-onset Atrial Fibrillation after Cardiac Surgery

Objective

The current study aims to investigate the role of echocardiographically measured epicardial adipose tissue (EAT) thickness in the prediction of new-onset atrial fibrillation (AF) following coronary artery bypass grafting (CABG) surgery.

Methods

One hundred and twenty-four patients scheduled to undergo isolated on-pump CABG due to coronary artery disease were enrolled to the current study. Patient characteristics, medical history and perioperative variables were prospectively collected. EAT thickness was measured using transthoracic echocardiography (TTE). Any documented episode of new-onset postoperative AF (POAF) until discharge was defined as the study endpoint. Fortyfour participants with POAF served as AF group and 80 patients without AF served as Non-AF group.

Results

Two groups were similar in terms of baseline echocardiographic and laboratory findings. In laboratory findings, the groups were similar in terms of the studied parameters, except N-terminal pro-brain natriuretic peptide (NT Pro-BNP), which was higher in AF group than in Non-AF group (P=0.035). The number of left internal mammary artery (LIMA) grafts was not different in both groups. AF group had higher cross-clamp (CC) and cardiopulmonary bypass (CPB) times than Non-AF group (P=0.01 and P<0.001). In multivariate logistic regression analysis, EAT was found an independent predictor for the development of POAF (OR 4.47, 95% CI 3.07-5.87, P=0.001).

Conclusion

We have shown that EAT thickness is associated with increased risk of AF development and can be used as a prognostic marker for this purpose.

Extracorporeal Hemadsorption versus Glucocorticoids during Cardiopulmonary Bypass: A Prospective, Randomized, Controlled Trial

Extracorporeal hemadsorption may reduce inflammatory reaction in cardiopulmonary bypass (CPB) surgery. Glucocorticoids have been used during open-heart surgery for alleviation of systemic inflammation after CPB. We compared intraoperative hemadsorption and methylprednisolone, with usual care, during complex cardiac surgery on CPB, for inflammatory responses, hemodynamics, and perioperative course. Seventy-six patients with prolonged CPB were recruited and randomized, with 60 included in final analysis. Allocation was into three groups: Methylprednisolone (n = 20), Cytosorb (n = 20), and Control group (usual care, n = 20). Proinflammatory (TNF-α, IL-1β, IL-6, and IL-8) and anti-inflammatory (IL-10) cytokines which complement C5a, CD64, and CD163 expression by immune cells were analyzed within the first five postoperative days, in addition to hemodynamic and clinical outcome parameters. Methylprednisolone group, compared to Cytosorb and Control had significantly lower levels of TNF-α (until the end of surgery, p < 0.001), IL-6 (until 48 h after surgery, p < 0.001), and IL-8 (until 24 h after surgery, p < 0.016). CD64 expression on monocytes was the highest in the Cytosorb group and lasted until the 5^th postoperative day (p < 0.016). IL-10 concentration (until the end of surgery) and CD163 expression on monocytes (until 48 h after surgery) were the highest in the Methylprednisolone group (p < 0.016, for all measurements between three groups). No differences between groups in the cardiac index or clinical outcome parameters were found. Methylprednisolone more effectively ameliorates inflammatory responses after CPB surgery compared to hemadsorption and usual care. Hemadsorption compared with usual care causes higher prolonged expression of CD64 on monocytes but short lasting expression of CD163 on granulocytes. Hemadsorption with CytoSorb® was safe and well tolerated. This trial is registered with clinicaltrials.gov (NCT02666703).

Association of T Cell-Derived Inflammatory Cytokines With Acute Kidney Injury and Mortality After Cardiac Surgery

Introduction

Animal models of renal ischemia-reperfusion injury (IRI) demonstrate that interferon (IFN)-γ producing T-helper (Th)-1 cells worsen acute kidney injury (AKI), whereas interleukin (IL)-4– and IL-13–producing Th2 cells lead to repair. We tested the association of these cytokines with AKI and mortality in patients who underwent cardiac surgery.

Methods

In 1444 participants of a multicenter, prospective, observational cohort, we measured 10 plasma biomarkers before and after cardiac surgery (IFN-γ, IL-4, IL-13, tumor necrosis factor [TNF]-α, IL-1β, IL-2, IL-6, IL-8, IL-10, and IL-12p70) and combined these biomarkers using principal component analysis (PCA). We also tested independent associations of Th1 (IFN-γ) and Th2 (IL-4 and IL-13) biomarkers with clinical outcomes of postoperative AKI and 1-year mortality.

Results

AKI occurred in 492 participants (34%), and 1-year mortality occurred in 81 participants (6%). Within 6 hours after surgery, IFN-γ, IL-4, and IL-13 increased 2.1-, 6.0-, and 4.6-fold, respectively, from their preoperative levels. Patients with higher levels of IFN-γ had higher odds of AKI (adjusted odds ratio per log change, 1.35 [1.13, 1.6]) and mortality (1.51 [1.17, 1.94]). Patients with higher levels of IL-4 and IL-13 also had higher odds of AKI (1.26 [1.09, 1.46] and 1.4 [1.16, 1.69], respectively) and mortality (1.46 [1.18, 1.82] and 1.71 [1.27, 2.31], respectively). Adding biomarkers to the clinical variables through use of PCA improved the area under the curve by 0.01 for AKI and 0.04 for mortality, resulting in final areas under the curve of 0.85 (0.83–0.87) and 0.76 (0.70–0.81), respectively.

Conclusion

Both Th1 and Th2 cytokines increased immediately after cardiac surgery and were associated with AKI and 1-year mortality. Our findings indicate activation of both Th1 and Th2 pathways after cardiac surgery rather than predominance of either pathway.

Identification of clinical factors predicting warfarin sensitivity after cardiac surgery

Background

Warfarin is commonly initiated post-cardiac surgery to reduce the risk of intracardiac thrombus formation. Studies have found that sensitivity is increased after cardiac surgery and anticoagulation is subsequently difficult to manage. This study set out to identify clinical markers of increased warfarin sensitivity in patients after cardiac surgery, and build a model that can predict warfarin sensitivity, and improve safety in this setting.

Methods

The study was an observational, retrospective cohort design. Clinical parameters including left ventricular ejection fraction (LVEF), cross-clamp time, age, serum albumin and C-reactive protein concentrations were collected from consenting patients who had undergone cardiac surgery and were prescribed postoperative warfarin. The warfarin dose index (WDI) was calculated for each patient from their international normalized ratio (INR) and warfarin dose, as a measure of sensitivity.

Results

A total of 41 patients were recruited to the study. Logarithmically transformed WDI (log WDI) significantly correlated with LVEF, cardiopulmonary bypass (CPB) time, cross-clamp time, baseline INR and co-administration of amiodarone (p < 0.05). When added to a linear regression model, LVEF and cross-clamp time produced a model that accounted for 41% of the variance in log WDI (R² = 0.41), p = 0.0002). Applying a log WDI cutoff value of -0.349 discriminated between patients who develop an INR > 4 and those who do not, with a sensitivity of 75% and a specificity of 70%.

Conclusions

This single-centre study has highlighted two risk factors for increased warfarin sensitivity post-cardiac surgery. Further research is needed to confirm these findings in a wider, more diverse population, and to validate this model.

Outcomes in patients undergoing complex cardiac repairs with cross clamp times over 300 minutes

BACKGROUND

Long cross clamp times have been associated with poor clinical outcomes, yet some patients require extremely long ischemic times to repair complex surgical problems. The purpose of this study was to examine short and mid-term survival and to identify risk factors for mortality and morbidity in patients with cross clamp times greater than or equal to 300 min.

METHODS

Review of our institution's Society of Thoracic Surgeons database identified 202 patients who underwent surgical procedures necessitating aortic cross clamp times 300 min or greater between 2001 and 2012. Short-term (30-day) clinical outcomes were derived from this database and survival was assessed utilizing the Social Security Death Index. Univariate and multivariate analyses were used to determine the relationship between independent variables and mortality and postoperative outcomes.

RESULTS

The average age of the patients was 69.5 ± 10.6 (mean ± standard deviation) years and the mean ejection fraction was 52 ± 12 %. 70.3 % of patients were male. Mean cross clamp time was 346 ± 45 min, and total bypass time was 421 ± 70 min. Thirty-day mortality was 12.4 %. The incidence of bleeding and stroke were 6.4 % and 4.0 % respectively. Prolonged ventilation occurred in 26.7 % of patients, and incidence of renal failure was 10.4 %. One, three, five, and seven year survival of the patients who survived the first 30 days post-surgery was 91.9 %, 83.2 %, 75.6 % and 65.7 % respectively. Proportional hazards analysis determined that the statistically significant hazard ratios for mid-term mortality for female gender, age, and prolonged postoperative ventilation were 2.11, 1.04 and 2.72, respectively (p < 0.05 for each).

CONCLUSIONS

Cardiac procedures requiring extremely long ischemic times have significant early mortality and morbidity. However, mid-term survival in the patients who survive is good. Decision-making regarding operability in complex cases should allow for long ischemic times.

Lymphatic pump treatment repeatedly enhances the lymphatic and immune systems

BACKGROUND

Osteopathic practitioners utilize manual therapies called lymphatic pump techniques (LPT) to treat edema and infectious diseases. While previous studies examined the effect of a single LPT treatment on the lymphatic system, the effect of repeated applications of LPT on lymphatic output and immunity has not been investigated. Therefore, the purpose of this study was to measure the effects of repeated LPT on lymphatic flow, lymph leukocyte numbers, and inflammatory mediator concentrations in thoracic duct lymph (TDL).

METHODS AND RESULTS

The thoracic ducts of five mongrel dogs were cannulated, and lymph samples were collected during pre-LPT, 4 min of LPT, and 2 hours post-LPT. A second LPT (LPT-2) was applied after a 2 hour rest period. TDL flow was measured, and TDL were analyzed for the concentration of leukocytes and inflammatory mediators. Both LPT treatments significantly increased TDL flow, leukocyte count, total leukocyte flux, and the flux of interleukin-8 (IL-8), keratinocyte-derived chemoattractant (KC), nitrite (NO2(-)), and superoxide dismutase (SOD). The concentration of IL-6 increased in lymph over time in all experimental groups; therefore, it was not LPT dependent.

CONCLUSION

Clinically, it can be inferred that LPT at a rate of 1 pump per sec for a total of 4 min can be applied every 2 h, thus providing scientific rationale for the use of LPT to repeatedly enhance the lymphatic and immune system.

Contribution of endogenous bradykinin to fibrinolysis, inflammation, and blood product transfusion following cardiac surgery: a randomized clinical trial

Bradykinin increases during cardiopulmonary bypass (CPB) and stimulates the release of nitric oxide, inflammatory cytokines, and tissue-type plasminogen activator (t-PA), acting through its B2 receptor. This study tested the hypothesis that endogenous bradykinin contributes to the fibrinolytic and inflammatory response to CPB and that bradykinin B2 receptor antagonism reduces fibrinolysis, inflammation, and subsequent transfusion requirements. Patients (N = 115) were prospectively randomized to placebo, ε-aminocaproic acid (EACA), or HOE 140, a bradykinin B2 receptor antagonist. Bradykinin B2 receptor antagonism decreased intraoperative fibrinolytic capacity as much as EACA, but only EACA decreased D-dimer formation and tended to decrease postoperative bleeding. Although EACA and HOE 140 decreased fibrinolysis and EACA attenuated blood loss, these treatments did not reduce the proportion of patients transfused. These data suggest that endogenous bradykinin contributes to t-PA generation in patients undergoing CPB, but that additional effects on plasmin generation contribute to decreased D-dimer concentrations during EACA treatment.

Approach to postoperative fever in pediatric cardiac patients

Fever in the postoperative period in children undergoing surgery for congenital heart disease is fairly common and tends to cause anxiety to both the surgeon and the patient. Such fever is associated with the metabolic response to trauma, systemic response to the cardiopulmonary bypass, hypothermia, presence of drainage tubes, drugs, blood transfusion as well as infections. Establishing the diagnosis requires proper assessment of the patient with focused history, targeted physical examination and judicious use of investigations with the knowledge of the common causes.

Remote ischaemic preconditioning does not alter perioperative cytokine production in high-risk cardiac surgery

RATIONALE

Remote ischaemic preconditioning (RIPC) is a novel cardioprotective strategy that uses brief intermittent limb ischaemia to protect the myocardium and other organs from perioperative ischaemic damage. The precise mechanism through which this protective effect occurs is unknown, but potentially could be related to changes in blood-borne mediators such as cytokines.

OBJECTIVE

To determine whether RIPC alters inflammatory cytokine expression in a double-blind, randomised, controlled trial of patients undergoing high-risk cardiac surgery.

METHODS AND RESULTS

Serum interleukin (IL)-6, IL-8, and IL-10 levels from 95 patients randomised to RIPC (n=47) or control treatment (n=48) were measured preoperatively, and 1, 2, 3, 6 and 12 h after cross-clamp removal. Systemic concentrations of all cytokines were increased from baseline following surgery, and, compared with simple procedures, complex surgeries were associated with significantly higher release of IL-6 (ratio of mean area under the curves 1.54 (95% CI 1.02 to 2.34), p=0.04) and IL-10 (1.97 (1.16 to 3.35), p=0.012). No significant difference in mean cytokine levels between the RIPC and control groups was detected at any time point, irrespective of the type of surgery undergone.

CONCLUSIONS

High levels of IL-6, IL-8 and IL-10 are produced during high-risk cardiac surgery, and RIPC does not alter these elevated perioperative cytokine concentrations. Identification of factors that influence the ability to induce RIPC-mediated cardioprotection should be the priority of future research.

TRIAL REGISTRATION

is in the Australian New Zealand Clinical Trials Registry (http://www.anzctr.org.au; ACTRN12609000965202).

Procalcitonin kinetics in pediatric patients with systemic inflammatory response after open heart surgery

OBJECTIVE

To evaluate procalcitonin and C-reactive protein as markers of inflammation severity and their value in predicting development of organ failure after pediatric open heart surgery.

DESIGN

Prospective, observational, clinical study.

SETTING

Single university hospital.

PATIENTS

Thirty-three pediatric patients with systemic inflammatory response syndrome (SIRS; n=19) and SIRS+organ failure (SIRS+OF; n=14) following open heart surgery were included.

MEASUREMENTS AND RESULTS

Plasma procalcitonin and C-reactive protein levels were measured before and after the operation, and 1, 2, 3, and 4 days after surgery. Patients were evaluated daily to assess organ failure. Postoperative procalcitonin levels in the SIRS+OF group were significantly higher than in the SIRS group. C-reactive protein levels were similar between the groups throughout the study period. Peak procalcitonin levels were found to be positively correlated with aortic cross-clamp and cardiopulmonary bypass times, duration of mechanical ventilation, intensive care unit and hospital stay, mortality and organ failure development. Peak procalcitonin was found to be a good predictor of postoperative organ failure development and mortality. However, the predictive value of peak C-reactive protein for organ failure and mortality was found to be weak. Double-peak procalcitonin curves were observed in SIRS+OF patients with infection during the intensive care unit stay.

CONCLUSION

In the SIRS+OF group peak procalcitonin levels were found to be highly predictive for mortality and organ failure development, whereas C-reactive protein levels were not. Daily procalcitonin measurements in SIRS+OF patients may help identify the postoperative infection during the follow-up period.

Impact of angiotensin converting enzyme inhibition on post-coronary artery bypass interleukin 6 release

BACKGROUND

Angiotensin 1 converting enzyme (ACE) inhibitors reduce morbidity and mortality after coronary artery bypass graft surgery (CABG). This benefit may result from an anti-inflammatory action.

OBJECTIVE

To examine the effect of ACE inhibition on interleukin 6 (IL-6) concentrations after CABG.

PATIENTS AND METHODS

161 patients undergoing elective first time CABG were recruited, of whom 41 (25%) were receiving ACE inhibitor treatment; 21 patients with confounding postoperative complications were excluded. After these exclusions there were 33 patients (24%) on ACE inhibitor treatment. Plasma IL-6 was measured preoperatively and again six hours after CABG.

RESULTS

Baseline IL-6 concentrations (geometric mean (SEM)) were non-significantly lower among the patients receiving ACE inhibitors (3.7 (0.1) v 4.3 (0.1) pg/ml, p = 0.12). Overall, post-CABG IL-6 concentrations increased significantly (mean rise 177 (12) pg/ml, p < 0.0005). This response was blunted among ACE inhibitor treated patients. Median increases in IL-6 concentrations were 117 v 193 pg/ml, for treated v non-treated patients, respectively (Kruskal-Wallis, p = 0.02), with peak postoperative IL-6 concentrations lower among the subjects receiving ACE inhibitors than in untreated subjects (142 (19) v 196 (13) pg/ml, p = 0.02). The effect of ACE inhibitors remained significant after multivariate analysis (p = 0.018).

CONCLUSIONS

ACE inhibitor treatment is associated with a reduction in IL-6 response to CABG. The data suggest that this class of drug may have a direct anti-inflammatory effect, which could explain some of its clinical benefit.

Influence of surgical procedures on interleukin-6 and monocyte chemotactic and activating factor responses: CABG vs. valvular surgery

Interleukin-6 (IL-6) and monocyte chemotactic and activating factor/monocyte chemoattractant protein-1 (MCAF/MCP-1) play pivotal roles in systemic inflammation, immune response, and tissue damage after cardiopulmonary bypass (CPB). Previous reports have described transient rises in IL-6 and MCAF after CPB, but the data seem to vary according to the different surgical procedures used. To evaluate the influence of the different surgical procedures on the proinflammatory cytokine responses, we compared perioperative serum IL-6 and MCAF release in coronary artery bypass grafting (CABG) and valvular surgery cases. Eighteen CABG (CABG group) and 7 single valvular cardiac surgery patients (valve group) were included in this study. Blood samples were taken to measure the serum concentrations of IL-6 at the induction of anesthesia, at the removal of the aortic cross-clamp, at the end of CPB, at the end of surgery, and 24 h after the termination of surgery. Serum IL-6 and MCAF were assayed by ELISA. Serum IL-6 increased immediately after aortic declamping and reached its peak at the end of surgery in both groups. Serum IL-6 concentrations at the end of surgery and 24 h after surgery were significantly higher in the valve group than in the CABG group (123.9 +/- 21.7 pg/ml vs. 79.7 +/- 10.4 pg/ml, p = 0.049; 113.6 +/- 25.0 pg/ml vs. 39.9 +/- 11.5 pg/ml, p = 0.006, respectively). Serum MCAF increased immediately after aortic declamping, and the MCAF level at the end of surgery was significantly higher in the valve group than in the CABG group (1118.4 +/- 353.9 pg/ml vs. 241.0 +/- 71.2 pg/ml, p = 0.002, respectively). IL-6 and MCAF may play important roles in the pathophysiology of surgical damage with CPB, and the different surgical procedures appear to affect the proinflammatory cytokine release after cardiac surgery differently.