A potential mechanism of vasodilation after warm heart surgery: The temperature-dependent release of cytokines

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.

Vasoplegic syndrome in patients undergoing heart transplantation

Objectives

To summarize the risk factors, onset time, and treatment of vasoplegic syndrome in patients undergoing heart transplantation.

Methods

The PubMed, OVID, CNKI, VIP, and WANFANG databases were searched using the terms "vasoplegic syndrome," "vasoplegia," "vasodilatory shock," and "heart transplant*," to identify eligible studies. Data on patient characteristics, vasoplegic syndrome manifestation, perioperative management, and clinical outcomes were extracted and analyzed.

Results

Nine studies enrolling 12 patients (aged from 7 to 69 years) were included. Nine (75%) patients had nonischemic cardiomyopathy, and three (25%) patients had ischemic cardiomyopathy. The onset time of vasoplegic syndrome varied from intraoperatively to 2 weeks postoperatively. Nine (75%) patients developed various complications. All patients were insensitive to vasoactive agents.

Conclusions

Vasoplegic syndrome can occur at any time during the perioperative period of heart tranplantation, especially after the discontinuation of bypass. Methylene blue, angiotensin II, ascorbic acid, and hydroxocobalamin have been used to treat refractory vasoplegic syndrome.

Effect of 6% Hydroxyethyl Starch 130/0.4 on Inflammatory Response and Pulmonary Function in Patients Having Cardiac Surgery: A Randomized Clinical Trial

BACKGROUND

Cardiac surgery with cardiopulmonary bypass induces a profound inflammatory response that, when severe, can lead to multiorgan system dysfunction. Preliminary data suggest that administration of hydroxyethyl starch (HES) solutions may mitigate an inflammatory response and improve pulmonary function. Our goal was to examine the effect of 6% HES 130/0.4 versus 5% human albumin given for intravascular plasma volume replacement on the perioperative inflammatory response and pulmonary function in patients undergoing cardiac surgery.

METHODS

This was a subinvestigation of a blinded, parallel-group, randomized clinical trial of patients undergoing elective aortic valve replacement surgery at the Cleveland Clinic main campus, titled "Effect of 6% Hydroxyethyl Starch 130/0.4 on Kidney and Haemostatic Function in Cardiac Surgical Patients." Of 141 patients who were randomized to receive either 6% HES 130/0.4 or 5% human albumin for intraoperative plasma volume replacement, 135 patients were included in the data analysis (HES n = 66, albumin n = 69). We assessed the cardiopulmonary bypass-induced inflammatory response end points by comparing the 2 groups' serum concentrations of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and macrophage migration inhibitory factor (MIF), measured at baseline and at 1 and 24 hours after surgery. We also compared the 2 groups' postoperative pulmonary function end points, including the ratio of partial pressure of arterial oxygen to fraction of inspired oxygen (Pao2:Fio2 ratio), dynamic lung compliance, oxygenation index (OI), and ventilation index (VI) at baseline, within 1 hour of arrival to the intensive care unit, and before tracheal extubation. The differences in the postoperative levels of inflammatory response and pulmonary function between the HES and albumin groups were assessed individually in linear mixed models.

RESULTS

Serum concentrations of the inflammatory markers (TNF-α, IL-6, MIF) were not significantly different (P ≥ .05) between patients who received 6% HES 130/0.4 or 5% albumin, and there was no significant heterogeneity of the estimated treatment effect over time (P ≥ .15). The results of pulmonary function parameters (Pao2:Fio2 ratio, dynamic compliance, OI, VI) were not significantly different (P ≥ .05) between groups, and there was no significant heterogeneity of the estimated treatment effect over time (P ≥ .15).

CONCLUSIONS

Our investigation found no significant difference in the concentrations of inflammatory markers and measures of pulmonary function between cardiac surgical patients who received 6% HES 130/0.4 versus 5% albumin.

Shear stress associated with cardiopulmonary bypass induces expression of inflammatory cytokines and necroptosis in monocytes

Cardiopulmonary bypass (CPB) is required during most cardiac surgeries. CBP drives systemic inflammation and multiorgan dysfunction that is especially severe in neonatal patients. Limited understanding of molecular mechanisms underlying CPB-associated inflammation presents a significant barrier to improve clinical outcomes. To better understand these clinical issues, we performed mRNA sequencing on total circulating leukocytes from neonatal patients undergoing CPB. Our data identify myeloid cells, particularly monocytes, as the major cell type driving transcriptional responses to CPB. Furthermore, IL-8 and TNF-α were inflammatory cytokines robustly upregulated in leukocytes from both patients and piglets exposed to CPB. To delineate the molecular mechanism, we exposed THP-1 human monocytic cells to CPB-like conditions, including artificial surfaces, high shear stress, and cooling/rewarming. Shear stress was found to drive cytokine upregulation via calcium-dependent signaling pathways. We also observed that a subpopulation of THP-1 cells died via TNF-α-mediated necroptosis, which we hypothesize contributes to post-CPB inflammation. Our study identifies a shear stress-modulated molecular mechanism that drives systemic inflammation in pediatric CPB patients. These are also the first data to our knowledge to demonstrate that shear stress causes necroptosis. Finally, we observe that calcium and TNF-α signaling are potentially novel targets to ameliorate post-CPB inflammation.

Effects of Minimal Extracorporeal Circulation on the Systemic Inflammatory Response and the Need for Transfusion after Coronary Bypass Grafting Surgery

Objectives

The aim of this study is to compare the effects of the minimal extracorporeal circulation (MiECT) on postoperative systemic inflammatory response and the need for transfusion in patients undergoing open heart surgery with cardiopulmonary bypass.

Methods

Patients were divided into two groups; Group M (n=31) included the patients operated via using the MiECT system and Group C (n=27) included the patients operated via using conventional cardiopulmonary bypass (CPB). Perioperative markers of inflammation after cardiopulmonary bypass in both groups were tested by measuring the levels via chemiluminescent immunometric assay. Blood samples were taken consecutively after anesthesia induction, 30^th minute of CPB, on the 6^th, 24^th, and 48^th hours after cardiopulmonary bypass.

Results

The mean amount of priming solution was significantly lower in Group M when compared to Group C (802.60 ± 48.26 and 1603.71 ± 49.85 ml). The mean hematocrit (Hct) value taken immediately after cardiopulmonary bypass was found to be significantly higher in the MiECT patients with respect to the other group (% 32.71 ± 3.98 and % 28.82 ± 4.39). The transfused amounts of erythrocyte suspension and fresh frozen plasma were found to be significantly lower in patients in Group M when compared to those in Group C. Postoperative mediastinal drainage was also significantly lower in patients in Group M with respect to the other group. There was no significant difference between markers of inflammation.

Conclusion

Our results show that MiECT seems to be more advantageous in terms of priming volume, perioperative hematocrit levels, need for blood and blood product transfusion, and mediastinal drainage with respect to the conventional approach after coronary artery bypass grafting.

Mast cell activation and arterial hypotension during proximal aortic repair requiring hypothermic circulatory arrest

OBJECTIVE

Aortic surgeries requiring hypothermic circulatory arrest evoke systemic inflammatory responses that often manifest as vasoplegia and hypotension. Because mast cells can rapidly release vasoactive and proinflammatory effectors, we investigated their role in intraoperative hypotension.

METHODS

We studied 31 patients undergoing proximal aortic repair with hypothermic circulatory arrest between June 2013 and April 2015 at Duke University Medical Center. Plasma samples were obtained at different intraoperative time points to quantify chymase, interleukin-6, interleukin-8, tumor necrosis factor alpha, and white blood cell CD11b expression. Hypotension was defined as the area (minutes × millimeters mercury) below a mean arterial pressure of 55 mm Hg. Biomarker responses and their association with intraoperative hypotension were analyzed by 2-sample t test and Wilcoxon rank sum test. Multivariable logistic regression analysis was used to examine the association between clinical variables and elevated chymase levels.

RESULTS

Mast cell-specific chymase increased from a median 0.97 pg/mg (interquartile range [IQR], 0.01-1.84 pg/mg) plasma protein at baseline to 5.74 pg/mg (IQR, 2.91-9.48 pg/mg) plasma protein after instituting cardiopulmonary bypass, 6.16 pg/mg (IQR, 3.60-9.41 pg/mg) plasma protein after completing circulatory arrest, and 7.64 pg/mg (IQR, 4.63-12.71 pg/mg) plasma protein after weaning from cardiopulmonary bypass (each P value < .0001 vs baseline). Chymase was the only biomarker associated with hypotension during (P = .0255) and after (P = .0221) cardiopulmonary bypass. Increased temperatures at circulatory arrest and low presurgical hemoglobin levels were independent predictors of increased chymase responses.

CONCLUSIONS

Mast cell activation occurs in cardiac surgery requiring cardiopulmonary bypass and hypothermic circulatory arrest and is associated with intraoperative hypotension.

The Inflammatory Response to Cardiopulmonary Bypass— Should It Be Treated?

Proinflammatory cytokines, including tumor necrosis factor (TNF) α and the interieukins, are important in the metabolic response to injury or infection. Although the importance of cytokine release during cardiopulmonary bypass (CPB) is not fully appreciated, increasing num bers of publications present evidence that cytokine release during CPB is detrimental. In addition, endoge nous inhibitors of cytokine function, including TNF-sol uble receptor and interleukin 1 receptor antagonist, are released in response to elevated proinflammatory cyto kine levels during and after CPB. The involvement of these endogenous inhibitors in the pathophysiology of proinflammatory cytokine-induced solid organ injury after CPB remains to be defined.

Normothermic versus hypothermic cardiopulmonary bypass in children undergoing open heart surgery (thermic-2): study protocol for a randomized controlled trial

Background

During open heart surgery, patients are connected to a heart-lung bypass machine that pumps blood around the body (“perfusion”) while the heart is stopped. Typically the blood is cooled during this procedure (“hypothermia”) and warmed to normal body temperature once the operation has been completed. The main rationale for “whole body cooling” is to protect organs such as the brain, kidneys, lungs, and heart from injury during bypass by reducing the body’s metabolic rate and decreasing oxygen consumption. However, hypothermic perfusion also has disadvantages that can contribute toward an extended postoperative hospital stay. Research in adults and small randomized controlled trials in children suggest some benefits to keeping the blood at normal body temperature throughout surgery (“normothermia”). However, the two techniques have not been extensively compared in children.

Objective

The Thermic-2 study will test the hypothesis that the whole body inflammatory response to the nonphysiological bypass and its detrimental effects on different organ functions may be attenuated by maintaining the body at 35°C-37°C (normothermic) rather than 28°C (hypothermic) during pediatric complex open heart surgery.

Methods

This is a single-center, randomized controlled trial comparing the effectiveness and acceptability of normothermic versus hypothermic bypass in 141 children with congenital heart disease undergoing open heart surgery. Children having scheduled surgery to repair a heart defect not requiring deep hypothermic circulatory arrest represent the target study population. The co-primary clinical outcomes are duration of inotropic support, intubation time, and postoperative hospital stay. Secondary outcomes are in-hospital mortality and morbidity, blood loss and transfusion requirements, pre- and post-operative echocardiographic findings, routine blood gas and blood test results, renal function, cerebral function, regional oxygen saturation of blood in the cerebral cortex, assessment of genomic expression changes in cardiac tissue biopsies, and neuropsychological development.

Results

A total of 141 patients have been successfully randomized over 2 years and 10 months and are now being followed-up for 1 year. Results will be published in 2015.

Conclusions

We believe this to be the first large pragmatic study comparing clinical outcomes during normothermic versus hypothermic bypass in complex open heart surgery in children. It is expected that this work will provide important information to improve strategies of cardiopulmonary bypass perfusion and therefore decrease the inevitable organ damage that occurs during nonphysiological body perfusion.

Trial Registration

ISRCTN Registry: ISRCTN93129502, http://www.isrctn.com/ISRCTN93129502 (Archived by WebCitation at http://www.webcitation.org/6Yf5VSyyG).

Clinical implication of perioperative inflammatory cytokine alteration

Cytokines are key modulators of inflammatory responses, and play an important role in the defense and repair mechanisms following trauma. After traumatic injury, an immuno-inflammatory response is initiated immediately, and cytokines rapidly appear and function as a regulator of immunity. In pathologic conditions, imbalanced cytokines may provide systemic inflammatory responses or immunosuppression. Expression of perioperative cytokines vary by different intensities of surgical trauma and types of anesthesia and anesthetic agents. Inflammatory cytokines play important roles in postoperative organ dysfunction including central nervous system, cardiovascular, lung, liver, and kidney injury. Inhibition of cytokines could protect against traumatic injury in some circumstances, therefore cytokine inhibitors or antagonists might have the potential for reducing postoperative tissue/organ dysfunction. Cytokines are also involved in wound healing and post-traumatic pain. Application of cytokines for the improvement of surgical wound healing has been reported. Anesthesia-related immune response adjustment might reduce perioperative morbidity because it reduces proinflammatory cytokine expression; however, the overall effects of anesthetics on postoperative immune-inflammatory responses needs to be further investigated.

Toll-like receptor and its roles in myocardial ischemic/reperfusion injury

The innate immune system, mediated via toll-like receptors (TLRs), represents the first line of defensive mechanisms that protects hosts from invading microbial pathogens. TLRs are a family of pattern recognition receptors (PRRs), and are pathologically activated by a set of pathogen-associated microbial patterns (PAMPs) and damage-associated molecular patterns (DAMPs). TLRs deliver signals via a specific intracellular signaling pathway involving distinctive adaptor proteins and protein kinases, and ultimately initiate transcriptional factors resulting in inflammatory responses. TLR4 is a paramount type of TLRs, located in the heart, and plays an important role in mediating myocardial ischemic reperfusion (I/R) injury. Loss-of-function experiments and animal models using genetic techniques have found that the MyD88-independent and the MyD88-dependent pathways together participate in the pathological process of myocardial I/R injury. Some other distinctive signaling pathways, such as the PI3K/AKt and AMPK/ERK pathways, interacting with the TLR4 signaling pathway, were also found to be causes of myocardial I/R injury. These different pathways activate a series of downstream transcriptional factors, produced a great quantity of inflammatory cytokines, such as IL, TNF, and initiate inflammatory response. This results in cardiac injury and dysfunction, such as myocardial stunning, no reflow phenomenon, reperfusion arrhythmias and lethal reperfusion injury, and other related complication such as ventricular remodeling. In the future, blockades aimed at blocking the signaling pathway could benefit developments in pharmacology.

Hypothermia in bleeding trauma: a friend or a foe?

The induction of hypothermia for cellular protection is well established in several clinical settings. Its role in trauma patients, however, is controversial. This review discusses the benefits and complications of induced hypothermia--emphasizing the current state of knowledge and potential applications in bleeding patients. Extensive pre-clinical data suggest that in advanced stages of shock, rapid cooling can protect cells during ischemia and reperfusion, decrease organ damage, and improve survival. Yet hypothermia is a double edged sword; unless carefully managed, its induction can be associated with a number of complications. Appropriate patient selection requires a thorough understanding of the pre-clinical literature. Clinicians must also appreciate the enormous influence that temperature modulation exerts on various cellular mechanisms. This manuscript aims to provide a balanced view of the published literature on this topic. While many of the advantageous molecular and physiological effects of induced hypothermia have been outlined in animal models, rigorous clinical investigations are needed to translate these promising findings into clinical practice.

The Release of Systemic Inflammatory Mediators Is Independent of Cardiopulmonary Bypass Temperature

OBJECTIVE

The aim of this study was to investigate the effect of systemic CPB temperature on the production of the key mediators of the systemic inflammatory response to coronary artery bypass graft (CABG) surgery.

DESIGN

Randomized clinical study.

SETTING

University hospital.

PARTICIPANTS

Thirty patients undergoing first-time CABG surgery.

INTERVENTIONS

The patients were randomized to hypothermic (32 degrees C, n = 15) or normothermic (36 degrees C, n = 15) CPB.

MEASUREMENTS AND MAIN RESULTS

Plasma interleukin (IL)-6, IL-8, IL-10, C-reactive protein (CRP), cortisol, and neutrophils were measured the day before operation, at closure of the sternum, and 4, 16, and 44 hours later. The cytokine, CRP, cortisol, and neutrophil responses were independent of temperature during CPB with peak concentrations of IL-10 at closure of the sternum followed by IL-6, IL-8, cortisol, neutrophils, and finally CRP. A correlation between maximal plasma concentrations of IL-10 and cortisol was seen in both groups after surgery (p = 0.02). Drainage after surgery was lower after normothermic CPB (p=0.02), with no difference in the requirement for blood transfusion. All patients were discharged from the intensive care unit within 24 hours after surgery.

CONCLUSIONS

The release of systemic inflammatory mediators after cardiac surgery was independent of mild hypothermia (32 degrees C) versus normothermia (36 degrees C) during CPB.

Direct evidence of endothelial injury during cardiopulmonary bypass by demonstration of circulating endothelial cells

Endothelial activation is considered a key process in the development of a whole body inflammatory response secondary to cardiopulmonary bypass (CPB). Increased levels of a multitude of soluble mediators have been described as being released during and after cardiac surgery. Circulating endothelial cells have recently been established as a novel marker of endothelial damage in a variety of vascular disorders. Blood samples from 20 patients undergoing elective coronary artery bypass surgery were obtained preoperatively and 1, 6, 12, 24, and 48 h after termination of CPB. Control samples were obtained from ten healthy volunteers. Circulating endothelial cells (CEC) were isolated with immunomagnetic anti-CD146-coated Dynabeads, and counted in a Nageotte chamber. Low numbers of CEC were observed in healthy control volunteers (12 +/- 6 cells/mL; median: 9 cells/mL). CEC numbers were already significantly elevated in all patients before CPB, and there was a further significant increase after weaning from CPB (maximum increase at 6 h after CPB: 73 +/- 30 cells/mL; range: 30-153 cells/mL, p < 0.001). The number of CEC provides further and direct evidence that CPB is associated with a pronounced endothelial injury and/or damage. CEC appear to be most useful markers for vascular endothelial activation because they are specific, stable, and circulating components of injured vessel wall.

Induction of interleukin-19 and interleukin-22 after cardiac surgery with cardiopulmonary bypass

BACKGROUND

Interleukin (IL)-19, IL-20, and IL-22, three novel cytokines in the IL-10 family, have recently been discovered. The biological functions and clinical implications of these cytokines are not clear. We aimed to analyze if serum levels of these cytokines were altered in inflammatory responses of postoperative cardiopulmonary bypass (CPB) and investigate the molecular mechanism involved in cytokine induction.

METHODS

Twenty-five patients undergoing elective aortic-coronary bypass grafting with CPB were enrolled in this study. Blood samples withdrawn at (T1) before anesthesia, (T2) CPB start, (T3) CPB end, (T4) 4 hours post-CPB, (T5) 8 hours post-CPB, (T6) 12 hours post-CPB, (T7) 24 hours post-CPB, and (T8) 48 hours post-CPB were assayed for IL-6, IL-10, IL-19, IL-20, IL-22, and tumor necrotic factor-alpha (TNF-alpha). Transcripts of IL-19, IL-20, and IL-22 from monocytes were analyzed. In vitro, levels of IL-19, IL-20, and IL-22 production in monocytes incubated with IL-6 and TNF-alpha were determined.

RESULTS

The serum levels of IL-19 and IL-22 significantly increased at T3, peaked at T5, and remained increased at T8 (p<0.001). Induction of IL-19 and IL-22 was concomitant with the change in IL-10, IL-6, and TNF-alpha levels. Interleukin-19, IL-20, and IL-22 transcripts in monocytes from patients increased after CPB. In vitro experiments showed that IL-6 and TNF-alpha upregulated IL-19 protein expression in monocytes.

CONCLUSIONS

Serum IL-19 and IL-22 were induced in cardiac surgery with CPB and concomitant with induction of IL-6 and TNF-alpha. The IL-19 and these proinflammatory cytokines may interactively contribute to systemic inflammatory responses after CPB.

Hemodynamic effects of cardiotomy suction blood

OBJECTIVE

Cardiac surgery induces a systemic inflammatory activation, which in severe cases is associated with peripheral vasodilation and hypotension. Cardiotomy suction blood contains high levels of inflammatory mediators, but the effect of cardiotomy suction blood on the vasculture is unknown. We investigated the effect of cardiotomy suction blood on systemic vascular resistance in vivo and whether cell-saver processing of suction blood affects the vascular response.

METHODS

Twenty-five patients undergoing coronary surgery (mean age, 68 +/- 2 years; 80% men) were included in a prospective randomized study. The patients were randomized to retransfusion of cell-saver processed (n = 13) or cell-saver unprocessed (n = 12) suction blood during full cardiopulmonary bypass. Mean arterial blood pressure was continuously registered during retransfusion, and systemic vascular resistance was calculated. Plasma concentrations of tumor necrosis factor alpha, interleukin 6, and complement factor C3a were measured in suction blood.

RESULTS

Retransfusion of cardiotomy suction blood induced a transient reduction in systemic vascular resistance in all patients. The peak reduction was significantly less pronounced in the group receiving cell-saver processed blood (-12% +/- 2% vs -28% +/- 3%, P = .001). There was a significant correlation between tumor necrosis factor alpha concentration in retransfused cardiotomy suction blood and peak reduction of systemic vascular resistance (r = 0.60, P = .002).

CONCLUSIONS

The results suggest cardiotomy suction blood is vasoactive and might influence vascular resistance and blood pressure during cardiac surgery. The observed vasodilation is proportional to the inflammatory activation of suction blood and can be reduced by processing suction blood with a cell-saving device before retransfusion.

Effect of Blood Temperature on the Efficacy of Systemic Leucodepletion during Cardiopulmonary Bypass: A Prospective Randomized Clinical Study

The authors examined the effect of blood temperature within the cardiopulmonary bypass (CPB) circuit on the efficacy of an arterial line filter. Eighty patients undergoing elective, primary coronary artery bypass grafting under CPB were prospectively randomized in two equal groups. Blood temperature was kept at 35 degrees C in the first group and reduced to 28 degrees C in the second group. Twenty patients in each group had an arterial line LG6 filter attached onto CPB circuit. The other 20 patients in each group (controls) had a non-leukocyte-depleting filter. Blood samples (10 ml) were taken before CPB, at 5 minutes on CPB, at 30 minutes on CPB, 5 minutes after aortic clamp removal, and 6 hours postoperatively. Leucocytes were counted under light microscopy. Activated leucocytes were identified using nitroblue tetrazolium staining. Patients undergoing leucodepletion had significantly lower total and activated leukocyte counts than control patients in both groups (p < 0.05). Patients having a leukocyte-depleting filter at a CPB temperature of 35 degrees C had significantly lower total leukocyte counts (p < 0.05) than those having a leukocyte-depleting filter at a CPB temperature of 28 degrees C (p < 0.05). However, there were not statistically significant differences in the activated leukocyte counts between the two leucodepleted groups (p > 0.05). This study shows that warm blood temperature within the CPB circuit has a positive effect on the overall leucodepleting efficacy of the LG6 filter. Activated leucocytes, however, seem to be depleted at similar rates irrespective of the blood temperature in the CPB circuit.

Methylthioninium chloride: pharmacology and clinical applications with special emphasis on nitric oxide mediated vasodilatory shock during cardiopulmonary bypass

Vasodilatory shock after cardiopulmonary bypass is a common complication requiring treatment with high doses of inotropes and prolonged stays in the intensive care unit. The vasodilatory shock is initiated by an inflammatory response to the extracorporeal circuit. The inflammatory response results in endothelial synthesis and release of nitric oxide resembling the clinical features observed in vasodilatory shock caused by septicaemia. During vasodilatory shock, the inhibition of nitric oxide synthase and the nitric oxide/cyclic guanylyl monophosphate pathway is an attractive adjunct to therapy with traditional inotropes. Methylthioninium chloride inhibits nitric oxide/cyclic guanylyl monophosphate mediated vasodilation and can successfully be used as a supplement in the treatment of vasodilatory shock associated with cardiopulmonary bypass. The application of methylthioninium chloride in septicaemia has not produced comparable positive clinical results.

Mild hypothermia for acute liver failure: a review of mechanisms of action

Brain edema with intracranial hypertension is a major complication in patients with acute liver failure. Current therapies for this complication include a variety of pharmacologic and interventional measures, some of which are frequently associated with adverse effects or contraindications. Even though these measures usually allow the control of intracranial hypertension for a certain period of time, recurrence is common. New therapies are therefore needed. Increasing clinical and experimental evidence suggests that induction of mild hypothermia (32 degrees C-35 degrees C) may be a therapeutic alternative. Similar to traumatic brain injury or brain stroke, induction of mild hypothermia seems highly effective to reduce intracranial pressure in patients with acute liver failure. Several mechanisms by which mild hypothermia may prevent brain edema and intracranial hypertension in this condition have been disclosed and may include beneficial effects on ammonia metabolism, as well as on the disturbances of brain osmolarity, cerebrovascular hemodynamics, brain glucose metabolism, inflammation, and others. Improvement of systemic hemodynamics and amelioration of liver injury may be other benefits of the systemic induction of mild hypothermia, but the impact of potential adverse events, such as infection, should also be taken into account. At a time when mild hypothermia is increasingly used in several specialized centers, performance of a randomized controlled trial seems critical to confirm the benefits of mild hypothermia in acute liver failure and to provide adequate guidelines for its use.

Early hormonal therapy stabilizes hemodynamics during donor procurement

BACKGROUND

Hemodynamic instability has been implicated in the loss of otherwise transplantable organs. We examined the hypothesis that administration of hormonal therapy early during donor management would stabilize hemodynamics and increase the number of organs procured.

METHODS

We retrospectively analyzed 133 consecutive donor records from a single organ procurement organization. Controls (C) received no early hormonal therapy. A steroid group (S) received methylprednisolone only and a combination hormonal therapy group (CH) received thyroxine, methylprednisolone, dextrose, and insulin at the start of donor management (t(0h)). Adrenergic support was adjusted to maintain mean arterial blood pressure (MAP) at > or =60 mm Hg. Doses of adrenergic agents were assessed at t(0h), 4 hours (t(4h)), and just prior to procurement (t(proc)).

RESULTS

Baseline characteristics were similar in all groups. Dosages of adrenergic agents decreased over time in all groups. A significant decrease in adrenergic requirements was seen in the CH group compared with the C group at t(4h) and t(proc). A trend toward decreased adrenergic requirements was noted in S compared with C at t(4h) and t(proc). Slightly more total organs were procured from S and CH compared with C.

CONCLUSIONS

Significantly less adrenergic support was required with early use of CH. A similar (although nonsignificant) reduction was seen with S. The benefit(s) of CH vs corticosteroids alone remains uncertain and requires further study.

Hemocompatibility of PMEA Coated Oxygenators Used for Extracorporeal Circulation Procedures

An inflammatory response to cardiopulmonary bypass (CPB) caused by bioincompatibility of extracorporeal circuits is one of the major clinical issues in cardiac surgery. Recently a new coating material, poly-2-methoxyethylacrylate (PMEA), was developed to improve the biocompatibility of blood contacting surfaces. In a simulated cardiopulmonary bypass model, using fresh human whole blood, 15 membrane oxygenators (Capiox SX18, Terumo Corp., Tokyo, Japan) were compared. Five of them had the PMEA coating, five had a heparin-coated surface, and five had no surface treatment. Blood samples were taken at several time-points during a 90 minute circulation period. Changes in coagulation, complement, and blood cell alteration factors were measured by ELISA methods, plasma bradykinin levels were measured by radioimmunoassay, and expression of genes encoding cytokines TNF-alpha, interleukin-1beta, interleukin-6, and interleukin-8 was determined by semiquantitative real time RT-PCR. Platelet adhesion was significantly reduced in both the PMEA and the heparin coated circuits. Release of platelet activation marker beta-thromboglobulin was significantly higher in the uncoated control group (p < 0.01). After 5 minutes of blood circulation bradykinin levels significantly increased in all three groups (p < 0.01); however, the group with the PMEA coated oxygenators showed the lowest values. Expression of genes encoding proinflammatory cytokines in monocytes was increased in all groups, with the lowest being in the PMEA coated group. PMEA coated CPB surfaces in an in vitro experimental model showed an improved thrombogenicity, reduced bradykinin release, less platelet activation and less proinflammatory cytokines gene expression in comparison with a noncoated group. The authors assume that PMEA coating may ameliorate some of intra- and postperfusion syndromes, particularly hypotension, unspecific inflammation, hyperfibrinolysis, and blood loss.

Pathophysiologic changes and effects of hypothermia on outcome in elective surgery and trauma patients

Generally, hypothermia is defined as a core temperature <35 degrees C. In elective surgery, induced hypothermia has beneficial effects. It is recommended to diminish complications attributable to ischemia reperfusion injury. Experimental studies have shown that hypothermia during hemorrhagic shock has beneficial effects on outcome. In contrast, clinical experience with hypothermia in trauma patients has shown accidental hypothermia to be a cause of posttraumatic complications. The different etiology of hypothermia might be one reason for this disparity because induced therapeutic hypothermia, with induction of poikilothermia and shivering prevention, is quite different from accidental hypothermia, which results in physiological stress. Other studies have shown evidence that this contradictory effect is related to the plasma concentration of high-energy phosphates (e.g., adenosine triphosphate [ATP]). Induced hypothermia preserves ATP storage, whereas accidental hypothermia causes depletion. Hypothermia also has an impact on the immunologic response after trauma and elective surgery by decreasing the inflammatory response. This might have a beneficial effect on outcome. Nevertheless, posttraumatic infectious complications may be higher because of an immunosuppressive profile. Further studies are needed to investigate the impact of induced hypothermia on outcome in trauma patients.

Cytokine gene expression in monocytes of patients undergoing cardiopulmonary bypass surgery evaluated by real-time PCR

Cardiopulmonary bypass (CPB) surgery induces systemic release of proinflammatory cytokines causing unspecific inflammatory reactions. This study deals with the development of a sensitive technique for detecting changes at the mRNA level in monocytes of patients undergoing CPB surgery, by using real-time PCR. Blood samples from patients undergoing elective coronary artery bypass grafting were obtained at six different time points. RNA was extracted from isolated monocytes and cDNA was synthesized by reverse transcriptase. CPB surgery induced gene expression of IL-1beta, IL-6, IL-8, and TNF-alpha, followed by a decrease below the preoperative expression values 6 h post CPB. High significant increases in gene expression for IL-8 at the end of surgery (p = 0.001) were detected. Real-time PCR is a powerful tool for getting simultaneously numerous sensitive, accurate, and reliable results from small amounts of biological material. This method avoids time-consuming and hazardous post-PCR manipulations and decreases the potential risk of PCR contamination.

Bacterial Lipopolysaccharide-Stimulated Release of Tumor Necrosis Factor-α from the Isolated Rat Heart: The Effect of Aprotinin and Forskolin

Aprotinin has been reported to reduce plasma levels of inflammatory cytokines associated with cardiopulmonary bypass (CPB). Because CPB is also associated with elevated levels of bacterial lipopolysaccharide (LPS) and LPS stimulates release of inflammatory cytokines from the heart we tested the hypothesis that aprotinin would inhibit cardiac release of tumor necrosis factor-α (TNF) provoked by LPS. Isolated rat hearts were perfused Langendorf style. After 30 minutes of equilibration LPS (100 ng/mL) was infused for 60 minutes. Timed samples of coronary effluent were collected at 0, 30, 60, 90, 120, and 150 minutes after the initiation of LPS for the measurement of coronary flow and the determination of TNF and cyclic AMP. Other hearts were perfused with buffer containing aprotinin [137 kallikrein-inhibiting units (KIU)/mL or 250 KIU/mL] and then infused with LPS. An additional group received forskolin (10 μM) and LPS. In hearts perfused as controls with buffer alone no TNF was detected in the coronary effluent. In hearts perfused with LPS TNF was reliably detected in the coronary effluent at 60 minutes (606 ± 450 pg/min) and increased with time to a level of 1792 ± 650 pg/min at 150 minutes. The addition of aprotinin had no significant effect on LPS-stimulated TNF release. For instance in hearts perfused with 137 KIU/mL aprotinin LPS-stimulated release at 150 minutes was 2141 ± 732 pg/min and in hearts perfused with 250 KIU/mL LPS-stimulated TNF release was 2049 ± 789 pg/min. Forskolin administration was associated with release of cyclic AMP from the heart and completely inhibited LPS-stimulated TNF release. We conclude that LPS stimulated release of TNF from the heart. Adding aprotinin to the perfusion buffer in either high or low concentrations did not attenuate LPS-stimulated cytokine release. Elevating myocardial cyclic AMP with forskolin completely attenuated LPS-stimulated TNF release.

Hypothermia augments polymorphonuclear leukocyte degranulation and interleukin-8 production from human umbilical vein endothelial cells and increases lipopolysaccharide-induced polymorphonuclear leukocyte-endothelial cell interaction when followed by normothermia

OBJECTIVE

To determine if hypothermia followed by normothermia (rewarmed to 37 degrees C) changes the inflammatory response of polymorphonuclear leukocytes (PMNs) and human umbilical vein endothelial cells (HUVEC).

DESIGN

Prospective, controlled, in vitro study.

SETTING

University laboratory.

PARTICIPANTS

PMNs from 4 healthy volunteers and HUVEC.

MEASUREMENTS AND MAIN RESULTS

PMNs and HUVEC were incubated for 3 hours at 20 degrees C, 30 degrees C, or 37 degrees C followed by 37 degrees C again. PMN degranulation, cytokine production from HUVEC, and PMN-HUVEC interaction were compared among the 3 experimental temperatures. Interleukin (IL)-8-induced PMN degranulation measured by myeloperoxidase concentrations was significantly higher in the 20 degrees C and 30 degrees C groups than the 37 degrees C groups. Bacterial lipopolysaccharide (LPS)-induced IL-8 production from HUVEC, measured by enzyme-linked immunosorbent assay, was significantly higher in the 20 degrees C group than the other 2 groups; however, tumor necrosis factor-alpha was not detectable in any of the groups. LPS-induced cell injury measured by cellular (51)Cr release was significantly higher in the 20 degrees C and 30 degrees C groups than in the 37 degrees C groups. This injury was significantly inhibited by IL-8 antibody.

CONCLUSION

Hypothermic (20 degrees C and 30 degrees C) incubation followed by rewarming augmented IL-8-induced PMN degranulation and LPS-induced IL-8 production from HUVEC and LPS-induced PMN-endothelial interaction. IL-8 plays an important role in this increased injury. This increased inflammatory response may support the positive outcomes of normothermic CPB.

Moderate hypothermia during cardiopulmonary bypass increases intramyocardial synthesis of heat shock protein 72

OBJECTIVES

This study was undertaken to test the hypothesis that the myocardial protective effect of moderate hypothermia during cardiopulmonary bypass involves upward regulation of heat shock protein 72.

METHODS

Sixteen young pigs were randomly assigned to a temperature regimen during standardized cardiopulmonary bypass of normothermia or moderate hypothermia (temperatures 37 degrees C and 28 degrees C, respectively, n = 8 per group). Myocardial probes were sequentially sampled from the right ventricle before and during bypass and 6 hours after bypass. Messenger RNA encoding for heat shock protein 72 was assessed by competitive reverse transcriptase-polymerase chain reaction, and heat shock protein 72 synthesis was assessed by Western blot and immunohistochemical methods. Induction of apoptosis was assessed by gene expression of apoptosis-regulating proteins (Bcl-xL, Bak, and Fas) according to competitive reverse transcriptase polymerase chain reaction. Apoptotic cells were identified with an in situ apoptosis-detection kit (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling) in combination with morphologic criteria. Necrotic cells were detected by standard histologic methods.

RESULTS

Moderate hypothermia rather than normothermia was associated with earlier and higher gene expression and synthesis of heat shock protein 72 in the myocardium during and after cardiac surgery. In the hypothermia group both heat shock protein 72 and the messenger RNA encoding it were detected as soon as 30 minutes after initiation of bypass and before aortic clamping, whereas in the normothermia group they were not detected before aortic clamping. Immunohistochemical methods showed localization of heat shock protein 72 in the cardiomyocytes, endothelial cells, and macrophages. Although the percentage of necrotic cells in the myocardium was lower in the hypothermic group, the induction of apoptosis regulatory proteins and the percentage of apoptotic cells did not differ between the groups.

CONCLUSIONS

These results suggest that the myocardial protective effect of moderate hypothermia during cardiopulmonary bypass involves upward regulation of heat shock protein 72 and inhibition of necrosis but not of apoptosis.

Cardiac surgery with deep hypothermic circulatory arrest produces less systemic inflammatory response than low-flow cardiopulmonary bypass in newborns

OBJECTIVE

We sought to compare low-flow cardiopulmonary bypass with deep hypothermic circulatory arrest in respect to the influence on the systemic inflammatory response.

METHODS

Twenty-three infants weighing less than 10 kg and scheduled for repair of congenital malformations were enrolled in a randomized, controlled study. Eleven patients underwent cardiac surgery with deep hypothermic circulatory arrest (the DHCA group). Low-flow cardiopulmonary bypass was used in another 12 patients (the LF group). Interleukin 6 and 8 and anaphylatoxin C3a levels were measured 6 times perioperatively. Also, perioperative weight gain and a radiologic soft-tissue index were compared.

RESULTS

All patients had an uneventful clinical course. Duration of deep hypothermic circulatory arrest was 40 +/- 4 minutes; the bypass time was significantly shorter in the DHCA group (85 +/- 8 vs 130 +/- 19 minutes). However, the duration of the operation was similar in both groups (245 +/- 30 vs 246 +/- 30 minutes). During cardiopulmonary bypass (rewarming), the concentration of C3a (3751 +/- 388 vs 5761 +/- 1688 ng/mL, mean +/- SEM) was significantly lower in the DHCA group than in the LF group. The interleukin 8 level was significantly lower, and the interleukin 6 level had a tendency to be lower in the DHCA group compared with levels in the LF group. There was less weight gain on the first postoperative day in the DHCA group (65 +/- 61 vs 408 +/- 118 g). The soft-tissue index suggested reduced edema formation in the DHCA group.

CONCLUSION

Deep hypothermic circulatory arrest produces less systemic inflammatory response than low-flow cardiopulmonary bypass. In addition, there is an indication of less fluid accumulation postoperatively.

Hyperprocalcitonemia is related to noninfectious postoperative severe systemic inflammatory response syndrome associated with cardiovascular dysfunction after coronary artery bypass graft surgery

OBJECTIVE

To investigate the role of 3 inflammatory parameters as early markers of severe systemic inflammatory response syndrome (SIRS) induced by coronary artery bypass graft surgery.

DESIGN

Prospective study.

SETTING

University hospital.

PARTICIPANTS

Patients (n = 63) undergoing elective coronary artery bypass graft surgery with cardiopulmonary bypass.

MEASUREMENTS AND MAIN RESULTS

The American College of Chest Physicians/Society of Critical Care Medicine classification was used to diagnose SIRS. Organ system failures were used to define severe SIRS. Serum concentrations of the inflammatory parameters (procalcitonin [PCT], C-reactive protein, leukocyte count) were determined before, during, and after surgery. SIRS occurred in 30 (47%) patients after surgery. Seven patients (11%) showed SIRS with greater-than-or-equal1 organ dysfunction (severe SIRS), whereas patients without SIRS had no organ dysfunction. Significantly higher serum levels of PCT were found in patients with severe SIRS from the 6th postoperative hour until the 3rd postoperative day with a peak level of 10.7 plus minus 13.2 ng/mL. No significant difference was detected between serum PCT of patients with SIRS but without any organ dysfunction and patients without SIRS. PCT levels of these patients remained lower than 1.7 ng/mL. Compared with PCT, plasma concentrations of C-reactive protein peaked later on the 2nd postoperative day and were not able to confirm the severity of SIRS. Leukocyte counts were not significantly modified.

CONCLUSIONS

PCT seems to be an appropriate marker to identify the early development of noninfectious postoperative severe SIRS after coronary artery bypass graft surgery with cardiopulmonary bypass.

The effects of aprotinin and steroids on generation of cytokines during coronary artery surgery

OBJECTIVE

To compare the efficacy of aprotinin and methylprednisolone in reducing cardiopulmonary bypass (CPB)-induced cytokine release, to evaluate the effect of myocardial cytokine release on systemic cytokine levels, and to determine the influence of cytokine release on perioperative and postoperative hemodynamics.

DESIGN

Prospective, randomized clinical trial.

SETTING

University teaching hospital and clinics.

PARTICIPANTS

Thirty patients undergoing elective coronary artery bypass graft surgery.

INTERVENTION

Patients were randomly allocated into groups treated with aprotinin (n = 10) or methylprednisolone (n = 10) or into an untreated control group (n = 10). Aprotinin-treated patients received aprotinin as a high-dose regimen (6 x 10(6) KIU), and methylprednisolone-treated patients received methylprednisolone (30 mg/kg intravenously) before CPB.

MEASUREMENTS AND MAIN RESULTS

Patients were analyzed for hemodynamic changes and alveolar-arterial PO2 difference (AaDO2) until the first postoperative day. Plasma levels of proinflammatory cytokines (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta, IL-6, and IL-8) were measured in peripheral arterial blood immediately before the induction of anesthesia, 5 minutes before CPB, 3 minutes after the start of CPB, 2 minutes after the release of the aortic cross-clamp, 1 hour after CPB, 6 hours after CPB, and 24 hours after CPB; and in coronary sinus blood immediately before CPB and 2 minutes after the release of the aortic cross-clamp. The hemodynamic parameters did not differ among the groups throughout the study. After CPB, AaDO2 significantly increased (p < 0.05) in all groups. A significant decrease in AaDO2 was observed in aprotinin-treated patients at 24 hours after CPB compared with the other groups (p < 0.05). TNF-alpha level from peripheral arterial blood significantly increased in control patients 1 hour after CPB (p < 0.01) and did not significantly increase in methylprednisolone-treated patients throughout the study. In all groups, IL-6 levels increased after the release of the aortic cross-clamp and reached peak values 6 hours after CPB. At 6 hours after CPB, the increase in IL-6 levels in methylprednisolone-treated patients was significantly less compared with levels measured in control patients and aprotinin-treated patients (p < 0.001). In control patients, IL-8 levels significantly increased 2 minutes after the release of the aortic cross-clamp (p < 0.05), and peak values were observed 1 hour after CPB (p < 0.01). IL-8 levels in control patients were significantly higher compared with patients treated with aprotinin and patients treated with methylprednisolone 1 hour after CPB (p < 0.05).

CONCLUSION

This study showed that methylprednisolone suppresses TNF-alpha, IL-6, and IL-8 release; however, aprotinin attenuates IL-8 release alone. Methylprednisolone does not produce any additional positive hemodynamic and pulmonary effects. An improved postoperative AaDO2 was observed with the use of aprotinin.

Effects of normothermia versus hypothermia on extravascular lung water and serum cytokines during cardiopulmonary bypass: a randomized, controlled trial

OBJECTIVE

To evaluate the influence of perfusion temperature on the systemic effects of cardiopulmonary bypass (CPB), including extravascular lung water index (EVLWI), and serum cytokines.

DESIGN

Prospective, randomized, controlled study.

SETTING

Cardiothoracic intensive care unit of a university hospital.

PATIENTS

Patients undergoing elective coronary artery bypass grafting.

INTERVENTIONS

Twenty-one patients undergoing elective coronary artery bypass grafting were randomly assigned to receive either normothermic bypass (36 degrees C, n = 8) with intermittent antegrade warm blood cardioplegia (IAWBC), or hypothermic (32 degrees C, n = 13) CPB with cold crystalloid cardioplegia.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure, heart rate, cardiac output, systemic vascular resistance, mean pulmonary arterial pressure, and pulmonary vascular resistance were determined at baseline, i.e., after induction of anesthesia but before sternal opening (T-1), at arrival in the intensive care unit (T0), and 4 hrs (T4), 8 hrs (T8), and 24 hrs (T24) after surgery. EVLWI, intrathoracic blood volume index (ITBVI), and EVLW/ITBV ratio were obtained by using thermal dye dilution utilizing an arterial thermistor-tipped fiberoptic catheter and were recorded at T-1, T0, T4, T8, and T24. Serial blood samples for cytokine measurements were obtained at each hemodynamic measurement time point. Before, during, and after CPB, there were no differences in the conventional hemodynamic measurements between the groups. There were no changes in EVLWI up to T8 in either group. Furthermore, no change in the ratio EVLW/ITBW was observed between the groups at any time, further indicating the absence of a change in pulmonary permeability. Plasma levels of interleukin-6, tumor necrosis factor-alpha, and interleukin-10 increased during and after CPB, independently of the perfusion temperature.

CONCLUSION

Normothermic CPB is not associated with additional inflammatory and related systemic adverse effects regarding cytokine production and EVLWI as compared with mild hypothermia. The potential temperature-dependent release of cytokines and subsequent inflammation has not been observed and normothermic CPB may be seen as a safe technique regarding this issue.

IL-8 concentration in coronary sinus blood during early coronary reperfusion after ischemic arrest

OBJECTIVE

Activation of the inflammatory response is an important factor contributing to complications of cardiopulmonary bypass. Increased level of proinflammatory cytokine - IL-8 has been reported during coronary artery bypass grafting (CABG) operations with the use of cardiopulmonary bypass. The aim of this study was to find out whether the heart is the main source of IL-8 during early coronary reperfusion.

METHODS

IL-8 concentration in coronary sinus before clamping and 5, 10, and 15 min after declamping of the aorta as well as in radial artery blood before clamping and 10 min after declamping of the aorta, was assessed in 30 patients undergoing CABG surgery.

RESULTS

We observed increase in IL-8 concentration in coronary sinus blood after declamping of the aorta, however no difference between coronary sinus and arterial blood concentration was noted. The median value of IL-8 concentration in coronary sinus blood was 1.85 pg/ml before ischemia and 15.4, 20.3, and 29.3 pg/ml in 5, 10 and 15 min after aortic declamping, respectively. Our additional finding was that there was a negative correlation between IL-8 level and hemoglobin saturation with oxygen in coronary sinus blood 10 min after coronary reperfusion.

CONCLUSIONS

We conclude that the heart is not the main source of IL-8 in early coronary reperfusion, although coronary reperfusion induces its release.

Treatment of sepsis in cardiac surgery: role of immunoglobulins

Cardiopulmonary bypass (CPB) is associated with an injury that may cause pathophysiological changes such as systemic inflammatory response syndrome, multiple organ dysfunction syndrome, and mediator-induced multiorgan failure. Systemic endotoxinaemia, release of proinflammatory cytokines, and interactions between neutrophils and endothelium have been reported to correlate with a high incidence of organ dysfunction, infection and sepsis following cardiac surgery. This review discusses the dysregulation of the immune response as a major reason for the higher susceptibility to infections following cardiac surgery, various treatment strategies to reduce CPB-induced inflammation, and especially the prophylactic use of immunoglobulins in cardiac surgery.

Long-term mild hypothermia with extracorporeal lung and heart assist improves survival from prolonged cardiac arrest in dogs

BACKGROUND AND PURPOSE

although normothermic extracorporeal lung and heart assist (ECLHA) improves cardiac outcomes, patients can not benefit from hypothermia-mediated brain protection. The present study evaluated the effects of long-term ECLHA with mild to moderate hypothermia (33 degrees C) in a canine model of prolonged cardiac arrest.

METHODS

15 dogs were assigned to either the hypothermic (seven dogs, 33 degrees C) or normothermic group (eight dogs, 37.5 degrees C). All dogs were induced to normothermic ventricular fibrillation (VF) for 15 min, followed by 24 h of ECLHA and 72 h of intensive care. The hypothermia group maintained core (pulmonary artery) temperature at 33 degrees C for 20 h starting from resuscitation, then were rewarmed by 28 h. Outcome evaluations included: (1) mortality; (2) catecholamine dose; (3) time to extubation; (4) necrotic myocardial mass (g); and (5) neurological deficits score (NDS).

RESULTS

in the normothermic group five dogs died of cardiogenic shock and one dog succumbed to poor oxygenation. The two surviving dogs remained comatose (NDS 60.5 +/- 4.9%) with necrotic myocardial mass of 14.5 +/- 3.5 g. In the hypothermic group, one dog died from pulmonary dysfunction, the other six dogs survived. The surviving dogs showed brain damage (29.8 +/- 2.5%), but there was evidence of some brain-protective effect. The mass of necrotic myocardium was 4.2 +/- 1.3 g in the hypothermic group or 3.4 times smaller than in the normothermic group. The survival rate was significantly higher in the hypothermic than in the normothermic group (P < 0.05). The catecholamine requirement was also lower in the hypothermic than in the normothermic dogs (P < 0.05).

CONCLUSIONS

Long-term mild to moderate hypothermia with ECLHA induced immediately after cardiac arrest improved survival as well as cerebral and cardiac outcomes.

Role of nitric oxide in a temperature dependent regulation of systemic vascular resistance in cardiopulmonary bypass

OBJECTIVES

Nitric oxide is the most potent vasodilator among inflammation-mediated vasoactive substances. Tepid cardiopulmonary bypass has been known to maintain low vascular resistance and nitric oxide may also be involved. There has been no previous clinical study elucidating a role of nitric oxide in a temperature dependent regulation of systemic vascular resistance in cardiopulmonary bypass.

METHODS

Thirty-one patients who underwent valvular surgery were randomly divided into two comparable groups; consisting of the hypothermic cardiopulmonary bypass (28 degrees C:14 patients) and the tepid cardiopulmonary bypass group (34 degrees C:17 patients). The serum levels of nitric oxide (NO(2)(-)+NO(3)(-)), prostaglandin E(2), bradykinin, 6-keto PGF1alpha, thromboxane B(2), endothelin-1, systemic vascular resistance index were measured before, 0, 12 and 24 h after cardiopulmonary bypass.

RESULTS

The pattern of change in systemic vascular resistance index and nitric oxide during and after cardiopulmonary bypass were significantly different between the two groups (P=0.0008, P=0.02). The tepid group showed significantly lower levels of systemic vascular resistance index after cardiopulmonary bypass than the hypothermic group (0 h: 2278+/-735 vs. 4387+/-1289, 12 h: 1827+/-817 vs. 2817+/-1146 and 24 h: 1690+/-548 vs. 2761+/-641 dyne s cm(-5) m(2), P=0.0001, P=0.03, P=0. 0006). The nitric oxide levels were significantly higher at 0, 12 and 24 h after cardiopulmonary bypass in the tepid group than those in the hypothermic group (84.7+/-33.3 vs. 46.3+/-18.1, 69.8+/-31.1 vs. 40.1+/-17.5 and 80.1+/-38.5 vs. 39.1+/-15.6 micromol/l, P=0.008, P=0.03, P=0.01). The prostaglandin E(2) levels in the tepid group was significantly higher just after cardiopulmonary bypass than that in the hypothermic group (37.3+/-20.0 vs. 15.8+/-8.6 pg/ml, P=0.02). The bradykinin level in the hypothermic group was significantly higher just after cardiopulmonary bypass than that in the tepid group (2.40+/-0.32 vs. 1.85+/-0.21 log(10) (pg/ml), P=0.005). Only nitric oxide showed a significant negative correlation with the systemic vascular resistance index both during and after cardiopulmonary bypass (r=-0.60, P<0.0001) as compared with prostaglandin E(2) and bradykinin.

CONCLUSIONS

These findings demonstrated that serum nitric oxide levels in tepid cardiopulmonary bypass were significantly higher than those in hypothermic cardiopulmonary bypass. Nitric oxide correlated with systemic vascular resistance. Thus, nitric oxide may play a pivotal role in a temperature dependent regulation of systemic vascular resistance in cardiopulmonary bypass.

Low systemic vascular resistance after cardiopulmonary bypass: incidence, etiology, and clinical importance

BACKGROUND

Low systemic vascular resistance during and immediately after cardiac surgery in which cardiopulmonary bypass is utilized is a well-known phenomenon, characterized as vasoplegia, which appears with an incidence ranging between 5% and 15%. The etiology is not completely elucidated and the clinical importance remains speculative.

METHODS

In this prospective clinical trial, we assessed the incidence of postoperative low systemic vascular resistance in 800 consecutive patients undergoing elective coronary artery bypass grafting and/or valve replacement. We have attempted to identify the predictive factors responsible for the presence of low systemic vascular resistance and we have examined the subsequent postoperative outcome of those patients who developed early postoperative vasoplegia. The severity of vasoplegia was divided into three groups according either to the value of systemic resistance and/or the dose of vasoconstrictive agents necessary to correct the hemodynamic.

RESULTS

Six hundred twenty-five patients (78.1%) did not develop vasoplegia, 115 patients (14.4%) developed a mild vasoplegia, and 60 patients (7.5%) suffered from severe vasoplegia. Low systemic vascular resistance did not affect hospital mortality but was the cause for delayed extubation and prolonged stay on the intensive care unit (ICU). Logistic regression analysis identified temperature and duration of cardiopulmonary bypass, total cardioplegic volume infused, reduced left ventricular function, and preoperative treatment with angiotensin-converting enzyme (ACE)-inhibitors, out of 25 parameters, as predictive factors for early postoperative vasoplegia.

CONCLUSION

The occurrence of low systemic vascular resistance following cardiopulmonary bypass is as high as 21.8%. The etiology of this clinical condition is most probably multifactorial. Mortality is not affected by vasoplegia, but there is a trend to higher morbidity and prolonged stay in the ICU.

Anaesthesia with propofol decreases FMLP-induced neutrophil respiratory burst but not phagocytosis compared with isoflurane

Propofol has been reported to produce a dose-dependent inhibition of phagocytosis and superoxide anion production during the respiratory burst (RB) of polymorphonuclear cells (PMNs) in vitro. In this randomized, blinded study, these two parameters were compared during propofol or isoflurane anaesthesia in patients undergoing elective interventional embolization of cerebral arterio-venous malformations. Anaesthesia was performed with continuous intravenous propofol 6-8 mg kg-1 h-1 (n = 15) or isoflurane 0.8-1.0% end tidal (n = 15). Heparinized blood was drawn before, and 2 and 4 h after induction of anaesthesia. The RB in isolated leucocytes was measured with the fluorescent dye rhodamine after ex vivo induction by Escherichia coli or tumour necrosis factor alpha/N-formyl-methionyl-leucylphenylalanine (TNF-alpha/FMLP). Phagocytosis was carried out in whole blood after incubation with fluorescein isothiocyanate (FITC)-labelled, opsonized E. coli and also measured with a flow cytometer. The two groups were similar in terms of biometric data and haemodynamic responsiveness. After 4 h of propofol or isoflurane anesthesia, the mean (SD) phagocytosis of E. coli was 93.2% (7.0%) and 94.3% (9.2%), respectively, of that before anaesthesia. The percentage of PMN with RB activity following TNF-alpha/FMLP stimulation was significantly reduced after 2 h (80.9% (24.2%); P < 0.05) and 4 h (53.7% (27.3); P < 0.05) of anaesthesia with propofol compared with the values before induction. This effect of propofol anaesthesia was significantly different from the effect of isoflurane anaesthesia. In contrast to published in vitro results, 4 h of anaesthesia with propofol did not reduce the phagocytotic capacity of human blood PMN more than isoflurane anaesthesia.

Induction of acute-phase reactive substances during open-heart surgery and efficacy of ulinastatin. Inhibiting cytokines and postoperative organ injury

OBJECTIVE

A systemic inflammatory response after open-heart surgery using cardiopulmonary bypass may be responsible for postoperative organ dysfunction. Ulinastatin, a protease inhibitor, plays an important role in host defense under periods of stress.

METHODS

We studied the efficacy of ulinastatin on changes in acute-phase reactive substances during and after open-heart surgery. Patients undergoing open-heart surgery were divided into an ulinastatin group (Group U) and a control group (Group C). In Group U, we introduced 600,000 units of ulinastatin into a priming solution for cardiopulmonary bypass, 300,000 units into a cardiopulmonary bypass circuit at the removal of aortic cross-clamping, and 300,000 units a day for 5 days following surgery.

RESULTS

Immediately after cardiopulmonary bypass, alpha 1-antitrypsin levels decreased significantly in both groups, and increased significantly on the second day after surgery. Ulinastatin levels decreased after cardiopulmonary bypass in Group C. Significantly high levels of ulinastatin were obtained in Group U. Interleukin-6, interleukin-8, and polymorphonuclear elastase were markedly induced, and high levels of plasma concentration continued for several days after surgery. At all sample points, these concentrations in Group U tended to be lower than those in Group C. A significantly positive correlation was seen between the maximum levels of interleukin-8 and polymorphonuclear elastase, but these cytokine and polymorphonuclear elastase levels did not correlate with parameters such as the duration of anesthesia, surgery, cardiopulmonary bypass, or aortic cross-clamping.

CONCLUSIONS

Our study suggests that high-dose ulinastatin administration to maintain a sufficient concentration of circulating protease inhibitors may suppress overinduction of cytokines and polymorphonuclear elastase in open-heart surgery.

Cytokine release and neutrophil activation are not prevented by heparin-coated circuits and aprotinin administration

BACKGROUND

Cardiopulmonary bypass (CPB) initiates a whole-body inflammatory response where complement and neutrophil activation and cytokine release play an important role. This prospective trial examined the effects of both heparin-coated circuits and aprotinin on the inflammatory processes during CPB, with respect to cytokine release and neutrophil activation.

METHODS

Two hundred patients undergoing cardiac surgery were randomized in four groups of 50 patients each: heparin-coated circuit with aprotinin (HCO-A) or without aprotinin (HCO) administration, and uncoated circuit with aprotinin (C-A) or without aprotinin administration (C). In groups receiving aprotinin, a high-dose regimen was given. In all groups, high initial doses of heparin were used (3 mg/kg intravenously). Tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and IL-8, and myeloperoxidase and elastase levels were measured in plasma samples taken before, during, and after CPB.

RESULTS

In all groups, the TNF-alpha, IL-6, and IL-8 levels reached a maximum after protamine administration. After 24 hours, they remained significantly elevated (IL-6 and IL-8) or returned to baseline values (TNF-alpha). A similar pattern was observed with myeloperoxidase and elastase levels. No significant intergroup differences were observed.

CONCLUSIONS

CPB is associated with cytokine release and neutrophil activation, which are not attenuated by the use of heparin-coated circuits or by the administration of aprotinin. Aprotinin and heparin-coated circuits do not show additive effects.

Should normothermia be restored and maintained during resuscitation after trauma and hemorrhage?

BACKGROUND

Although hypothermia often occurs after trauma and has protective effects during ischemia and organ preservation, it remains unknown whether maintenance of hypothermia or restoring the body temperature to normothermia during resuscitation has any deleterious or beneficial effects on heart performance and organ blood flow after trauma-hemorrhage.

METHODS

Male rats underwent laparotomy (i.e., induced trauma) and were exsanguinated to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximum shed volume was returned in the form of Ringer's lactate. Body temperature decreased from approximately 36.5 degrees C to below 32 degrees C. The animals were then resuscitated with four times the volume of maximal bleedout with Ringer's lactate. In one group, body temperature was rewarmed to 37 degrees C during resuscitation. In another group, body temperature was maintained at hypothermia (32 degrees C) for 4 hours after resuscitation. In an additional group, the body temperature was kept at 37 degrees C during hemorrhage as well as during resuscitation. Left ventricle performance parameters such as maximal rate of left ventricular pressure increase and decrease (+/-dP/dt(max)) were measured up to 4 hours. Cardiac output and regional blood flow were determined by radioactive microspheres at 4 hours after the completion of resuscitation.

RESULTS

The maintenance of normothermia during hemor. rhage or prolonged hypothermia after resuscitation depressed the left ventricular performance parameters, cardiac output, and regional blood flow in various organs. Rewarming the body to normothermia during resuscitation, however, significantly increased heart performance, cardiac output (from hypothermia 16.2 +/- 1.4 to 22.3 +/- 1.4 mL/min per 100 g body weight,p < 0.05) and total hepatic blood flow (from hypothermia 117.5 +/- 5.3 to 166.0 +/- 9.3 mL/min per 100 g tissue, p < .05).

CONCLUSION

Our data indicate that restoration of normothermia during resuscitation improves cardiac function and hepatic blood flow compared with hypothermia.

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.

Clinical role of blood heparin level monitoring during open heart surgery

Protamine has been used for neutralizing heparin and its dosage is decided by the initial fixed dose of heparin. Adequate protamine neutralization is very important to reduce complications. To attenuate excess reactions, in particular, whole blood heparin concentration during and after cardiopulmonary bypass was measured using Hepcon, and the efficacy of optimal protamine dose in open heart surgery was evaluated. Twenty patients were randomly divided into two comparable groups, P and C. In the C group, heparin was neutralized with an initial fixed dose of protamine, 1.67 mg protamine per milligram total heparin (n = 8). In the P group, protamine dose was determined for residual heparin concentration (n = 12). In the P group, blood heparin concentrations at 60 minutes after the establishment of cardiopulmonary bypass, just after cardiopulmonary bypass and first protamine administration were 2.35 +/- 0.14, 2.31 +/- 0.17 and 0.13 +/- 0.08 U/ml, respectively. Concentrations reached zero with the second protamine administration. The requirement of transfusion (659 +/- 224 vs. 1559 +/- 323 ml, p = 0.0314), pulmonary vascular resistance index just after the protamine administration (190 +/- 22 vs. 286 +/- 18 dyne.s.cm-5.m2, p = 0.0137) and the IL-8 levels (just after protamine: 26.9 +/- 5.1 vs. 43.5 +/- 5.9 pg/ml, p = 0.0499, 12 hours after cardiopulmonary bypass: 37.1 +/- 12.1 vs. 86.8 +/- 20.0, p = 0.0435) in the P group were significantly lower than those in the C group. These data suggested that heparin level monitoring in whole blood may be useful to determine the optimal dose of protamine resulting in the decrease of a requirement of blood components in open heart surgery and attenuating in transient pulmonary hypertension and excess protamine-induced inflammatory reactions.

The effects of cardiopulmonary bypass temperature on inflammatory response following cardiopulmonary bypass

OBJECTIVES

The inflammatory response to cardiopulmonary bypass is believed to play an important role in end organ dysfunction after open heart surgery and may be more profound after normothermic systemic perfusion. The aim of the present study was to investigate the effects of cardiopulmonary bypass temperature on the production of markers of inflammatory activity after coronary artery surgery.

METHODS

Forty-five low risk patients undergoing elective coronary artery surgery were prospectively randomized into three groups: hypothermia (28 degrees C, n = 15), moderate hypothermia (32 degrees C, n = 15), and normothermia (37 degrees C, n = 15). All patients received cold antegrade crystalloid cardioplegia and topical myocardial cooling with saline at 4 degrees C. Serum samples were collected for the estimation of neutrophil elastase, interleukin 8, C3d, and IgG under ice preoperatively, 5 min after heparinisation, 30 min following start of CPB, at the end of CPB, 5 min after protamine administration, and 4, 12 and 24 h postoperatively.

RESULTS

Patients were similar with regard to preoperative and intraoperative characteristics (age, sex, severity of symptoms, number of grafts performed, aortic cross clamp time, cardiopulmonary bypass time). Neutrophil elastase concentration increased markedly as early as 30 min after the onset of cardiopulmonary bypass and peaked 5 min after protamine administration. Levels were not significantly different between the three groups. A similar finding was apparent for C3d release. Interleukin 8 concentrations also demonstrated a considerable increase related to cardiopulmonary bypass in all groups, but there was a significantly more rapid decline in interleukin 8 concentrations in the normothermic group in the postoperative period. Eluted IgG fraction showed a much earlier peak concentration than the other markers, occurring within 30 min of the start of cardiopulmonary bypass. Levels reached a plateau, before declining soon after the end of bypass and remained higher than preoperative values at 24 h. There was no difference between the three groups. The cumulative release of all markers was calculated from the concentration-time curves, and was not statistically different between groups.

CONCLUSION

Normothermic systemic perfusion was not shown to produce a more profound inflammatory response compared to hypothermic and moderately hypothermic cardiopulmonary bypass.

Lung injury and acute respiratory distress syndrome after cardiopulmonary bypass

Cardiopulmonary bypass is often followed by pulmonary dysfunction as assessed by measuring the alveolar-arterial oxygenation gradient, intrapulmonary shunt, degree of pulmonary edema, pulmonary compliance, and pulmonary vascular resistance. It is also regarded as a risk factor for development of acute respiratory distress syndrome. On the other hand, cardiopulmonary bypass is associated with a whole body inflammatory response, which involves activation of complement, leukocytes, and endothelial cells with secretion of cytokines, proteases, arachidonic acid metabolites, and oxygen free radicals. Leukocyte adhesion to microvascular endothelium, leukocyte extravasation, and tissue damage are the final steps. Although the inflammatory response to cardiopulmonary bypass often remains at subclinical levels, it can also lead to major organ dysfunction and multiple organ failure. This review article summarizes the recent literature on the molecular and cellular mechanisms involved in the phenomenon of pulmonary dysfunction after cardiopulmonary bypass. It also summarizes reports on the prevalence and mortality of acute respiratory distress syndrome after cardiac surgery.