Circuits with surface modifying additive alter the haemodynamic response to cardiopulmonary bypass

Effects of interventions targeting the systemic inflammatory response to cardiac surgery on clinical outcomes in adults

BACKGROUND

Organ injury is a common and severe complication of cardiac surgery that contributes to the majority of deaths. There are no effective treatment or prevention strategies. It has been suggested that innate immune system activation may have a causal role in organ injury. A wide range of organ protection interventions targeting the innate immune response have been evaluated in randomised controlled trials (RCTs) in adult cardiac surgery patients, with inconsistent results in terms of effectiveness.

OBJECTIVES

The aim of the review was to summarise the results of RCTs of organ protection interventions targeting the innate immune response in adult cardiac surgery. The review considered whether the interventions had a treatment effect on inflammation, important clinical outcomes, or both.

SEARCH METHODS

CENTRAL, MEDLINE, Embase, conference proceedings and two trial registers were searched on October 2022 together with reference checking to identify additional studies.

SELECTION CRITERIA

RCTs comparing organ protection interventions targeting the innate immune response versus placebo or no treatment in adult patients undergoing cardiac surgery where the treatment effect on innate immune activation and on clinical outcomes of interest were reported.

DATA COLLECTION AND ANALYSIS

Searches, study selection, quality assessment, and data extractions were performed independently by pairs of authors. The primary inflammation outcomes were peak IL-6 and IL-8 concentrations in blood post-surgery. The primary clinical outcome was in-hospital or 30-day mortality. Treatment effects were expressed as risk ratios (RR) and standardised mean difference (SMD) with 95% confidence intervals (CI). Meta-analyses were performed using random effects models, and heterogeneity was assessed using I2.

MAIN RESULTS

A total of 40,255 participants from 328 RCTs were included in the synthesis. The effects of treatments on IL-6 (SMD -0.77, 95% CI -0.97 to -0.58, I2 = 92%) and IL-8 (SMD -0.92, 95% CI -1.20 to -0.65, I2 = 91%) were unclear due to heterogeneity. Heterogeneity for inflammation outcomes persisted across multiple sensitivity and moderator analyses. The pooled treatment effect for in-hospital or 30-day mortality was RR 0.78, 95% CI 0.68 to 0.91, I2 = 0%, suggesting a significant clinical benefit. There was little or no treatment effect on mortality when analyses were restricted to studies at low risk of bias. Post hoc analyses failed to demonstrate consistent treatment effects on inflammation and clinical outcomes. Levels of certainty for pooled treatment effects on the primary outcomes were very low.

AUTHORS' CONCLUSIONS

A systematic review of RCTs of organ protection interventions targeting innate immune system activation did not resolve uncertainty as to the effectiveness of these treatments, or the role of innate immunity in organ injury following cardiac surgery.

A clinical, renal and immunological assessment of Surface Modifying Additive Treated (SMART™) cardiopulmonary bypass circuits

Biocompatible cardiopulmonary bypass (CPB) circuits aim to reduce contact activation and its physiological consequences. We investigated the hypothesis that use of Surface Modifying Additive (SMA)-treated circuits (Sorin Group Ltd) compared with non-SMA circuits would be associated with preservation of blood pressure during CPB and modulation of perioperative subclinical renal function (urinary α-1-microglobulin (α-1-m)) and plasma and urinary cytokine changes. In a study of low-risk CABG patients ( n=40), randomized to SMA ( n=20) versus non-SMA circuits ( n=20), we found better preserved blood pressure at CPB initiation in SMA patients (p <0.05), particularly in ACE-inhibited SMA patients ( n=11) versus ACE-inhibited non-SMA patients ( n=10) (p <0.05). Plasma anti-inflammatory IL-10, as well as urinary α-1-m, were elevated 48 hours postoperatively (p <0.05). SMA patients also had lower blood loss (p <0.05). SMA circuits have some clinical benefit, especially in ACE-inhibited patients.

Does contemporary oxygenator design influence haemolysis?

Based on their design, all membrane oxygenators generate a certain resistance to flow. In clinical practice, this resistance is calculated by measuring both blood flow and the pressure drop over the oxygenator. Historically, some designs, such as the Kolobow spiral coil oxygenator and the Cobe flat sheet oxygenator, had quite a high pressure drop, but were, nevertheless, considered very haemocompatible. Today, both medium and low pressure drop oxygenators are commercially available. Based on physics and the existing literature, this review aims to investigate whether pressure drop by itself can be considered an independent factor of haemolysis.

Failure of surface-modified bypass circuits to improve platelet function during pediatric cardiac surgery

OBJECTIVE

Surface-modified cardiopulmonary bypass circuits have been shown to improve platelet function and decrease postoperative bleeding after heart surgery in adults. Two surface-modified cardiopulmonary bypass circuits are approved and commercially available for pediatric cardiac surgery. There have been few studies demonstrating the efficacy of these modifications for children. We performed a prospective, randomized trial comparing surface-modified cardiopulmonary bypass circuits to a standard unmodified circuit in pediatric cardiac surgery.

METHODS

Sixty-nine children (median 6 months old) undergoing first-time cardiac surgery were enrolled and randomized to an uncoated circuit or one of the two commercially available surface modified circuits for their operation. Blood samples were collected at baseline, on cardiopulmonary bypass, at the end of rewarming, after protamine, and at 18 to 24 postoperative hours. Platelet count, beta-thromboglobulin, and thromboelastography with and without abciximab were measured. Postoperative chest tube outputs and blood product utilization were also analyzed.

RESULTS

The platelet counts, beta-thromboglobulin levels, thromboelastographic measures of platelet function, and postoperative bleeding were not significantly different between the surface-modified cardiopulmonary bypass circuit groups and the control group.

CONCLUSION

Currently available surface-modified cardiopulmonary bypass circuits do not significantly improve platelet function or clinical outcomes after routine pediatric cardiac surgery.

Modulation of systemic inflammatory response after cardiac surgery

Cardiac surgery and cardiopulmonary bypass initiate a systemic inflammatory response largely determined by blood contact with foreign surfaces and the activation of complement. It is generally accepted that cardiopulmonary bypass initiates a whole-body inflammatory reaction. The magnitude of this inflammatory reaction varies, but the persistence of any degree of inflammation may be considered potentially harmful to the cardiac patient. The development of strategies to control the inflammatory response following cardiac surgery is currently the focus of considerable research efforts. Diverse techniques including maintenance of hemodynamic stability, minimization of exposure to cardiopulmonary bypass circuitry, and pharmacologic and immunomodulatory agents have been examined in clinical studies. This article briefly reviews the current concepts of the systemic inflammatory response following cardiac surgery, and the various therapeutic strategies being used to modulate this response.

Effects of Methylprednisolone and a Biocompatible Copolymer Circuit on Blood Activation During Cardiopulmonary Bypass

BACKGROUND

Cardiopulmonary bypass (CPB) induces derangements in physiology characterized by activation of blood pathways that may contribute to multiorgan dysfunction. This trial addresses the efficacy of a biocompatible surface alone and in combination with steroids in inhibiting these changes.

METHODS

In a factorial design, patients undergoing coronary artery bypass grafting were randomized (four groups; n = 17 per group) to CPB utilizing control circuits or a circuit prepared with a surface modifying active copolymer (SMA-CPB), with or without methylprednisolone (MPSS, 1 g intravenous). Leukocyte and complement activation, cytokine release, and bradykinin generation were measured. Clinical outcomes (blood loss, transfusion, arterial pressure response, and postoperative cardiac and pulmonary functions) were also examined.

RESULTS

The SMA-CPB was associated with a significant inhibition of elastase release (p = 0.026) and bradykinin generation (p = 0.027) during CPB. Terminal complement complex (TCC) generation was inhibited as an effect of SMA-CPB (p = 0.047). There was an interaction of SMA-CPB and MPSS to decrease both TCC (p = 0.042) and bradykinin generation (p = 0.028). There were strong effects of MPSS in inhibiting release of interleukin 6 (IL-6) (p = 0.007) and IL-8 (p < 0.001) and tissue plasminogen activator over time (p = 0.009) as well as decreasing peak day 1 creatine kinase (CK, p = 0.015) levels. Clinical effects of MPSS included decreased atrial fibrillation (p = 0.02), improved cardiac index over time, increased pulmonary compliance, and increased insulin need.

CONCLUSIONS

This trial suggests a potential beneficial effect for combined strategies to minimize inflammation after CPB. The specific effect of MPSS in decreasing postoperative atrial fibrillation and CK warrants further investigation of its role as a potential myocardial protective agent.

Magnetic resonance imaging to detect acute cerebral events in on-pump and hybrid-pump patients

BACKGROUND

Conventional cardiopulmonary bypass results in cerebral ischemic sequelae that may be reduced with hybrid pump technologies, such as the CardioVention system (CardioVention, Santa Clara, CA, USA). CardioVention differs from conventional bypass in that it has a novel air elimination module and reduced membrane surface area and priming volume. This preliminary study tested whether this pump confers neurological safety advantages over conventional bypass.

METHODS

Ten patients were studied, with 6 assigned to on-pump coronary artery bypass grafting and 4 to the CardioVention system. No patients had any stroke history. Within 72 hours postsurgery, each underwent diffusion-weighted magnetic resonance imaging, a sensitive test for cerebral ischemic events.

RESULTS

Two on-pump patients (33%) had postoperative findings on imaging, but none of the CardioVention patients demonstrated comparable changes ( P =.47). No patients had symptoms of acute stroke.

CONCLUSION

Postoperative magnetic resonance imaging showed a trend toward a greater rate of ischemic events in patients undergoing traditional on-pump surgery. These preliminary findings suggest that hybrid pump technologies, such as the CardioVention system, may attenuate the risk of short-term neurological complications. Future studies are indicated to confirm these subclinical ischemic changes and to correlate them with long-term neurocognitive changes.