Mesenteric dysfunction after cardiopulmonary bypass: role of complement C5a

Postoperative intra-abdominal hypertension predicts worse hospital outcomes in children after cardiac surgery: a pilot study†

OBJECTIVES

Our goal was to determine the incidence and characteristics of postoperative intra-abdominal hypertension (IAH) in paediatric patients undergoing open-heart surgery.

METHODS

This single-centre study included consecutive children (aged <16 years) who underwent open-heart surgery between July 2020 and February 2021. Patients who entered the study were followed until in-hospital death or hospital discharge. The study consisted of 2 parts. Part I was a prospective observational cohort study that was designed to discover the association between exposures and IAH. Postoperative intra-abdominal pressure was measured immediately after admission to the intensive care unit and every 6 h thereafter. Part II was a cross-sectional study to compare the hospital-related adverse outcomes between the IAH and the no-IAH cohorts.

RESULTS

Postoperatively, 24.7% (38/154) of the patients exhibited IAH, whereas 3.9% (6/154) developed abdominal compartment syndrome. The majority (29/38, 76.3%) of IAH cases occurred within the first 24 h in the intensive care unit. Multivariable analysis showed that the Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery score [odds ratio (OR) = 1.86, 95% confidence interval (CI) 1.23-2.83, P = 0.004], right-sided heart lesion (OR = 5.60, 95% CI 2.34-13.43, P < 0.001), redo sternotomy (OR = 4.35, 95% CI 1.64-11.57, P = 0.003), high baseline intra-abdominal pressure (OR = 1.43, 95% CI 1.11-1.83, P = 0.005), prolonged cardiopulmonary bypass duration (OR = 1.01, 95% CI 1.00-1.01, P = 0.005) and deep hypothermic circulatory arrest (OR = 5.14, 95% CI 1.15-22.98, P = 0.032) were independent predictors of IAH occurrence. IAH was associated with greater inotropic support (P < 0.001), more gastrointestinal complications (P = 0.001), sepsis (P = 0.003), multiple organ dysfunction syndrome (P < 0.001) and prolonged intensive care unit stay (z = -4.916, P < 0.001) and hospitalization (z = -4.710, P < 0.001). The occurrence of a composite outcome (P = 0.009) was significantly increased in patients with IAH.

CONCLUSIONS

IAH is common in children undergoing cardiac surgery and is associated with worse hospital outcomes. Several factors may be associated with the development of IAH, including basic cardiac physiology and perioperative factors.

TRIAL INFORMATION

This study was registered in the Chinese Clinical Trial Registry (Trial number: ChiCTR2000034322)URL site: https://www.chictr.org.cn/hvshowproject.html?id=41363&v=1.4.

Short-Term Outcomes and Risk Factors of In-Hospital Mortality in Patients Suffering Acute Mesenteric Ischemia after Cardiac Surgery: Role of Opioids and Lactic Acid

Acute mesenteric ischemia (AMI) is associated with poor clinical results after cardiac surgery. The aim of this study was to analyse the influence of AMI on short-term outcomes and all relevant risk factors of in-hospital mortality after cardiac surgery. Moreover, we aimed to investigate the role of opioids and lactic acid in the detection and prevention of AMI. Between August 2011 and September 2015, 176 consecutive patients with gastrointestinal complications after undergoing open-heart surgery were identified and included in this study. All patients were divided into two groups: AMI group (n = 39) and non-AMI group (n = 137). In terms of comorbidities, the groups were fairly equal and showed no significant differences. Dialysis was significantly higher (p < 0.001) in patients that suffered from AMI. Moreover, gastro-intestinal symptoms such as muscular defense (p = 0.004) and the laparotomy rate (p < 0.001) were significantly higher in the AMI group. Likewise, in-hospital mortality (p < 0.001) was significantly higher in patients with detected AMI. Univariate (p < 0.001) and multivariate analysis (p = 0.025) of both groups revealed that lactic acid value >2 mmol/L and present treatment with opioids are independent combined predictors of mesenteric ischemia in patients after undergoing cardiac surgery. Moreover, multivariate analysis showed peripheral vascular disease (p = 0.004), dialysis (p = 0.010), and septic shock (p = 0.003) as relevant predictors of in-hospital mortality. Prolonged analgetic treatment with opioids and sudden increase of lactic acid levels are independent combined predictors of mesenteric ischemia in patients after undergoing cardiac surgery. Furthermore, peripheral vascular disease, dialysis, and septic shock are relevant predictors for in-hospital mortality.

Predictors and outcomes of gastrointestinal complications after cardiac surgery: A systematic review and meta-analysis

Background

In this systematic review, we aimed to examine the risk factors and surgical outcomes of gastrointestinal complications using the meta-analysis techniques.

Methods

Studies involving patients with and without gastrointestinal complications after cardiac surgery were electronically searched using the PubMed database, Cochrane Library and Scopus database, between January 2000 and May 2022. Some studies on gastrointestinal complications examined only single gastrointestinal complication (only intestinal ischemia, only gastrointestinal bleeding or only liver failure). Studies evaluating at least three different gastrointestinal complications were included in the meta-analysis to reduce the heterogeneity. Cohort series that did not compare outcomes of patients with and without gastrointestinal complications, studies conducted in a country"s health system databases, review articles, small case series (<10 patients) were excluded from the meta-analysis.

Results

Twenty-five studies (8 prospective and 17 retrospective) with 116,105 patients were included in the meta-analysis. The pooled incidence of gastrointestinal complications was 2.51%. Patients with gastrointestinal complications were older (mean difference [MD]=4.88 [95% confidence interval [CI]: 2.85-6.92]; p<0.001) and had longer cardiopulmonary bypass times (MD=17.7 [95% CI: 4.81-30.5]; p=0.007). In-hospital mortality occurred in 423 of 1,640 (25.8%) patients with gastrointestinal complications. In-hospital mortality was 11.8 times higher in patients with gastrointestinal complications (odds ratio [OR]=11.8 [95% CI: 9.5-14.8]; p<0.001).

Conclusion

The development of gastrointestinal complications after cardiac surgery is more commonly seen in patients with comorbidities. In-hospital mortality after cardiac surgery is 11.8 times higher in patients with gastrointestinal complications than in patients without.

Organ damage evaluation in a temperature-controlled circulatory arrest rat model

BACKGROUND

Deep hypothermic circulatory arrest (DHCA) is commonly used in adult aortic surgery and pediatric complex congenital heart disease, and is associated with pathophysiological changes and postoperative complications. Here, a temperature-controlled circulatory arrest model in rats was established to study the suitable temperature of circulatory arrest by investigating the damage to body organs under different temperatures.

METHODS

Thirty Sprague‒Dawley rats were randomly divided into 5 equal groups for DHCA experiments: I (15-20 °C), II (20-25 °C), III (25-30 °C), IV (normothermic cardiopulmonary bypass), and V (sham operation group). Blood gas analysis, homodynamic parameters, and intervals of cardiac recovery were measured at different time points in all groups. Morphological changes in intestinal tissue were observed under light and electron microscopes. Oxidative stress was measured by MPO activity, MDA, and SOD content. Tissue damage was confirmed by serum detection of ALT, AST, BUN, Cr, and LDH. To examine the inflammatory response, cytokines, including IL-1, IL-4, IL-10, IFN-γ, and TNF-α, were detected.

RESULTS

The extracorporeal circulation technique caused damage to the body; the degree of the damage caused by the circulatory arrest technique may be related to circulating temperature, with the least amount of damage occurring at 20-25 °C compared to 15-20 °C and 25-30 °C. Ischemia and hypoxia can cause intestinal tissue damage, which manifests primarily as a loss of the intestinal mucosal barrier. Ischemic intestinal damage caused by DHCA was not associated with inflammation.

CONCLUSION

The study provides new insights into the pathophysiologic mechanisms of DHCA.

Risk Factors Associated with In-Hospital Mortality for Patients with Acute Abdomen After Cardiac Surgery

OBJECTIVES

Management of acute abdomen (AA) differs due to the heterogeneity of underlying pathophysiology. Complications of AA and its overall outcome after cardiac surgery are known to be associated with poor results. The aim of this retrospective analysis was to evaluate risk factors for AA in patients undergoing cardiac surgery.

METHODS

Between December 2011 and December 2014, a total of 131 patients with AA after cardiac surgery were identified and retrospectively analyzed using our institutional database. Statistical analysis of risk factors concerning in-hospital mortality of mentioned patient cohort was performed using IBM SPSS Statistics.

RESULTS

Overall in-hospital mortality was 54.2% (71/131). Analyzing in-hospital non-survivors (NS) versus in-hospital survivors (S) peripheral artery disease (28.2% vs. 11.7%; p = 0.03), the need for assist device therapy (33.8% vs. 16.7%; p = 0.03) and the requirement of hemodialysis (67.6% vs. 23.3%; p < 0.01) were significantly higher in NS. Furthermore, lactic acid values at onset of symptoms were shown to be significantly higher in NS (5.7 ± 5.7 mmol/L vs. 2.8 ± 2.9 mmol/L; p < 0.01). Assured diagnosis of mesenterial ischemia was strongly associated with worse outcome (odds ratio 10.800, 95% confidence interval 2.003-58.224; p = 0.006).

CONCLUSION

In conclusion, in critically ill patients after performed cardiac surgery peripheral vascular disease, need for supportive hemodynamic assist device systems and occurrence of renal failure are risk factors associated with worsen outcome. Additionally, rise of lactic acid could potentially be associated with onset of intestinal malperfusion and should be taken into account in therapeutic decisions preventing fatal mesenterial ischemia.

Gastrointestinal complications following cardiac surgery

Gastrointestinal complications after cardiac surgery may be uncommon but they carry high mortality rates. Incidences range from 0.5% to 5.5%, while mortality rates of such complications vary from 0.3% to 87%. They range from small gastrointestinal bleeds, ileus, and pancreatitis to life-threatening complications such as liver failure and ischemic bowel. Due to the vague and often absence of specific signs and symptoms, diagnosis of a gastrointestinal complication is often late. This article aims to review and summarize the literature concerning gastrointestinal complications after cardiac surgery. We discuss the causes, risk factors, diagnosis, preventative measures, and management of these complications. In general, risk factor identification, preventive measures, early diagnosis, and swift management are the keys to reducing the occurrence of gastrointestinal complications and their associated morbidity and mortality.

The Roles of Complement Factor C5a and CINC-1 in Glucose Transport, Ultrafiltration, and Neutrophil Recruitment during Peritoneal Dialysis

Background

In a recent experimental study, we showed that low molecular weight heparin improved ultrafiltration and blocked complement activation and coagulation in a single peritoneal dialysis (PD) dwell.

Objective

The aim of the present study was to evaluate the possible contribution of the complement factor C5a and the potential interactions between C5a, the coagulation system, and cytokines of the interleukin (IL)-8 family (cytokine-induced neutrophil chemoattractant; CINC-1).

Methods

Nonuremic rats were exposed through an indwelling catheter to a single dose of 20 mL glucose- (2.5%) based filter-sterilized PD fluid, with or without the addition of anti-rat C5 antibody. The dwell fluid was analyzed 2 and 4 hours later concerning activation of the coagulation cascades, neutrophil recruitment, ultrafiltration volume; CINC-1, glucose, urea, and histamine concentrations; and ex vivo intraperitoneal chemotactic activity.

Results

The numbers of neutrophils and levels of thrombin–antithrombin complex (TAT) and CINC-1 increased significantly during the PD dwell. C5 blockade significantly reduced the levels of TAT and increased the ultrafiltration volumes at 2 hours. Glucose concentrations were significantly positively correlated to ultrafiltration volumes.

Conclusions

Blockade of C5 leads to an increase in ultra-filtration, probably by a mechanism that involves a reduction in glucose transport. This effect may form a basis for improving PD efficiency in situations where high glucose transport limits ultrafiltration. Mechanisms connected to complement activation during PD may involve coagulation. Further studies of the intraperitoneal cascade systems under conditions of PD are indicated.

Incidence of postoperative atrial fibrillation in transdermal β-blocker patch users is lower than that in oral β-blocker users after cardiac and/or thoracic aortic surgery

OBJECTIVE

Postoperative atrial fibrillation (POAF) after open heart surgery is associated with a high risk of mortality and morbidity. Although oral β-blockers are usually recommended to prevent POAF, the efficacy of a transdermal β-blocker patch in preventing POAF is unclear. We compared the incidence of POAF between users of oral and transdermal bisoprolol.

METHODS

We investigated 108 patients who underwent cardiac and/or thoracic aortic surgery between April 2016 and February 2018. We compared perioperative clinical and hemodynamic variables between 49 patients treated with a transdermal bisoprolol patch and 59 patients treated with an oral bisoprolol fumarate.

RESULTS

POAF occurred in 24% of patients in the transdermal and in 46% of patients in the oral bisoprolol groups (p = 0.027). No intergroup difference was observed in in-hospital mortality, perioperative blood pressures and heart rates, and other morbidities. Multivariable logistic regression analysis revealed that the use of transdermal bisoprolol was independently associated with a lower rate of POAF (odds ratio 0.21, 95% confidence interval 0.05-0.84, p = 0.027).

CONCLUSIONS

A transdermal bisoprolol patch is an effective and safe β-blocker drug delivery system. The incidence of POAF in this group was lower than that in users of oral bisoprolol.

Comparison of intestinal ischemia after on-pump versus off-pump coronary artery bypass grafting surgery

Background/aim

Acute mesenteric ischemia (AMI), one of the gastrointestinal system complications, which occurs following cardiac surgery, is challenged in the literature with a diminished incidence of AMI by heart surgery without cardiopulmonary bypass (CPB) or with pulsatile CPB. This study aims to compare the incidence and mortality rate of mesenteric ischemia in a series of consecutive patients undergoing coronary artery bypass grafting (CABG) through on-pump and off-pump techniques.

Materials and methods

This study included patients who underwent CABG between 1 January 2010 and 31 June 2016. All patients were divided into two groups: Group 1 comprised 6396 CABG patients operated on with the off-pump technique. Group 2 included 1210 patients who received CABG with the on-pump technique. Preoperative data were collected on the studied variables. Postoperative data included the development of intestinal ischemia and in-hospital mortality.

Results

Of 7606 consecutive CABG patients, a total of 31 (0.4%) developed intestinal ischemia. The incidence of postoperative mesenteric ischemia was 0.28% in Group 1 and 1.07% in Group 2 (P = 0.000). The survival rates after AMI were 61.1% in Group 1 (off-pump) and 7.7% in Group 2 (on-pump) (P = 0.003). Time from the first occurrence of nonspecific GI complaints to laparotomy was similar in the off-pump and on-pump groups and had no effect on mortality.Conclusions: With regard to the incidence of mesenteric ischemia and survival after laparotomy, off-pump CABG patients revealed significant improvement compared with those operated on with the on-pump technique.

Establishment of Predictive Models for Nonocclusive Mesenteric Ischemia Comparing 8,296 Control with 452 Study Patients

OBJECTIVE

The aim of this study was to develop clinical preoperative, intraoperative, and postoperative scores for early identification of patients who are at risk of nonocclusive mesenteric ischemia (NOMI).

DESIGN

A retrospective analysis.

SETTING

Single center.

PARTICIPANTS

From January 2008 to December 2014, all patients from the Department of Thoracic and Cardiovascular Surgery were included on the basis of the hospital database.

INTERVENTIONS

All mesenteric angiographically identified NOMI patients were compared with non-NOMI patients.

MEASUREMENTS AND MAIN RESULTS

The study population of 8,748 patients was randomized into a cohort for developing the scores (non-NOMI 4,214 and NOMI 235) and a cohort for control (non-NOMI 4,082 and NOMI 217). Risk factors were identified using forward and backward Wald test and were included in the predictive scores for the occurrence of NOMI. C statistic showed that the scores had a high discrimination for the prediction of NOMI preoperatively (C statistic 0.79; p < 0.001), intraoperatively (C statistic 0.68; p < 0.001), and postoperatively (C statistic 0.85; p < 0.001). A combination of the preoperative, intraoperative, and postoperative risk scores demonstrated the highest discrimination (C statistic 0.87; p < 0.001). The combined score included the following risk factors: renal insufficiency (preoperative); use of cardiopulmonary bypass and intra-aortic balloon pump support (intraoperative); and reexploration for bleeding, renal replacement therapy, and packed red blood cells ≥ 4 units (postoperative). The results were similar in the control group.

CONCLUSIONS

These scores could be useful to identify patients at risk for NOMI and promote a rapid diagnosis and therapy.

CD177-mediated nanoparticle targeting of human and mouse neutrophils

Neutrophils are the most abundant white blood cells, with a vital role in innate immune defense against bacterial and fungal pathogens. Although mostly associated with pathological processes directly related to immune defense, they can also play a detrimental role in inflammatory conditions and have been found to have a pro-metastatic role in the spread of cancer cells. Here, we explore ways to temporarily suppress these detrimental activities. We first examined the possibility of using siRNA and antisense oligonucleotides (ASOs) for transient knockdown of the human and mouse C5a receptor, an important chemoattractant receptor involved in neutrophil-mediated injury that is associated with myocardial infarction, sepsis, and neurodegenerative diseases. We found that siRNAs and ASOs transfected into cultured cell lines can eliminate 70–90% of C5a receptor mRNA and protein within 72 h of administration, a clinically relevant time frame after a cardiovascular event. Targeted drug delivery to specific cells or tissues of interest in a mammalian host, however, remains a major challenge. Here, using phage display technology, we have identified peptides that bind specifically to CD177, a neutrophil-specific surface molecule. We have attached these peptides to fluorescent, lipid-based nanoparticles and confirmed targeting and delivery to cultured cells ectopically presenting either human or mouse CD177. In addition, we have shown peptide-nanoparticle binding specifically to neutrophils in human and mouse blood. We anticipate that these or related tagged nanoparticles may be therapeutically useful for delivery of siRNAs or ASOs to neutrophils for transient knockdown of pro-inflammatory proteins such as the C5a receptor.

Microvascular dysfunction in patients with diabetes after cardioplegic arrest and cardiopulmonary bypass

PURPOSE OF REVIEW

The purpose of the current review is to describe the changes of microvascular function in patients with diabetes after cardioplegic arrest and cardiopulmonary bypass (CPB) and cardiac surgery.

RECENT FINDINGS

Cardiac surgery, especially that involving cardioplegia and CPB, is associated with significant changes in vascular reactivity of coronary/peripheral microcirculation, vascular permeability, gene/protein expression, and programmed cell death, as well as with increased morbidity and mortality after surgical procedures. In particular, these changes are more profound in patients with poorly controlled diabetes.

SUMMARY

Because alterations in vasomotor regulation are critical aspects of mortality and morbidity of cardioplegia/CPB, a better understanding of diabetic regulation of microvascular function may lead to improved postoperative outcomes of patients with diabetes after cardioplegia/CPB and cardiac surgery.

Advents in the Diagnosis and Management of Ischemic Colitis

BACKGROUND

Ischemic colitis (IC) is a common type of ischemic insult, resulting from decreased arterial blood flow to the colon. This disease can be caused from either atherosclerotic occlusive vascular disease or non-occlusive disease. The aim of this study is to present the diagnostic methodology and management of this severe disease based on current literature.

METHODS

A literature search has been done including articles referring to modern diagnosis and management of IC.

RESULTS

IC is usually a transient disease, but it can also cause gangrene of the colon, requiring emergency surgical exploration. Diagnosis is troublesome and is based on imaging examinations, mainly computerized tomography, which in association with colonoscopy can delineate the distribution pattern and severity of disease.

CONCLUSION

The majority of patients with mild disease have usually complete clinical recovery within a short period. The severe forms of the disease carry high morbidity and mortality rates and prompt surgical intervention is the only way to improve the associated severe prognosis.

Risk factor analysis for nonocclusive mesenteric ischemia following cardiac surgery: A case-control study

Although rare, postcardiac surgery nonocclusive mesenteric ischemia (NOMI) is a life-threatening condition. Identifying the risk factors for NOMI during immediate postoperative period may help early detection and intervention, which leads to improved clinical outcomes. The objective of this study was to identify the clinical features and risk factors of NOMI for prognosis identification after cardiac surgery, focusing on immediate postoperative parameters.Among 9445 patients who underwent cardiac surgery over a span of 9 years, 40 NOMI cases (0.4%) requiring surgical interventions were reviewed. Suspected NOMI was diagnosed by sigmoidoscopy or computed tomography. To identify the risk factors, a control group (case: control = 1:3 ratio) was randomly selected and compared using logistic regression models.NOMI was diagnosed after a mean of 8.1 ± 9.6 days following cardiac surgery. Age (odds ratio: 1.16, 95% confidence interval: 1.08-1.25, P < .001), total vasoactive-inotropic score (VIS), and the maximal lactate level at postoperative day 0 (1.003, [1.001-1.005], P = .012), (1.23, [1.04-1.44], P = .011) were shown as risk factors. NOMI cases showed persistent hyperlactatemia without washout during the first 48 hours (P = .04). Thirty-four cases underwent exploratory laparotomy within a median of 10 (2-356) hours after the diagnosis, but only 17 patients (42.5%) survived. Compared with survivors, nonsurvivors showed higher total VIS at diagnosis, higher lactate levels during the first 24 hours postoperatively, and more frequently required extensive bowel resection (P < .05).Old age, postoperative high-dose vasoactive-inotropic use, and persistent high lactate level during the first 24 hours postsurgery were identified as risk factors for NOMI. Lactic acidosis and necrotic-bowel extent at surgical exploration were associated with poor survival.

Ischemic Colitis after Cardiac Surgery: Can We Foresee the Threat?

Introduction

Ischemic colitis (IC) remains a great threat after cardiac surgery with use of extracorporeal circulation. We aimed to identify predictive risk factors and influence of early catecholamine therapy for this disease.

Methods

We prospectively collected and analyzed data of 224 patients, who underwent laparotomy due to IC after initial cardiac surgery with use of extracorporeal circulation during 2002 and 2014. For further comparability 58 patients were identified, who underwent bypass surgery, aortic valve replacement or combination of both. Age ±5 years, sex, BMI ± 5, left ventricular function, peripheral arterial disease, diabetes and urgency status were used for match-pair analysis (1:1) to compare outcome and detect predictive risk factors. Highest catecholamine doses during 1 POD were compared for possible predictive potential.

Results

Patients’ baseline characteristics showed no significant differences. In-hospital mortality of the IC group with a mean age of 71 years (14% female) was significantly higher than the control group with a mean age of 70 (14% female) (67% vs. 16%, p<0.001). Despite significantly longer bypass time in the IC group (133 ± 68 vs. 101 ± 42, p = 0.003), cross-clamp time remained comparable (64 ± 33 vs. 56 ± 25 p = 0.150). The majority of the IC group suffered low-output syndrome (71% vs. 14%, p<0.001) leading to significant higher lactate values within first 24h after operation (55 ± 46 mg/dl vs. 31 ± 30 mg/dl, p = 0.002). Logistic regression revealed elevated lactate values to be significant predictor for colectomy during the postoperative course (HR 1.008, CI 95% 1.003–1.014, p = 0.003). However, Receiver Operating Characteristic Curve calculates a cut-off value for lactate of 22.5 mg/dl (sensitivity 73% and specificity 57%). Furthermore, multivariate analysis showed low-output syndrome (HR 4.301, CI 95% 2.108–8.776, p<0.001) and vasopressin therapy (HR 1.108, CI 95% 1.012–1.213, p = 0.027) significantly influencing necessity of laparotomy.

Conclusion

Patients who undergo laparotomy for IC after initial cardiac surgery have a substantial in-hospital mortality risk. Early postoperative catecholamine levels do not influence the development of an IC except vasopressin. Elevated lactate remains merely a vague predictive risk factor.

Gastrointestinal complications following cardiac surgery with cardiopulmonary bypass

Gastrointestinal complications following cardiac surgery with cardiopulmonary bypass include paralytic ileus, stress ulcer, acute ischemic colitis, gastrointestinal bleeding, acute cholecystitis, acute pancreatitis, acute hepatic failure and so on. Due to the lack of diagnostic tests with high specificity and sensitivity, the early diagnosis of these complications is difficult, which leads to a higher mortality rate. Therefore, accurately identifying the risk factors is important for early diagnosis and treatment. The purpose of this paper is to review the pathogenesis, risk factors, diagnosis and treatment of gastrointestinal complications after cardiac surgery with cardiopulmonary bypass.

Gastrointestinal complications after cardiac surgery: 10-year experience of a single Australian centre

BACKGROUND

Gastrointestinal (GI) complications after cardiac surgery are uncommon, but are associated with high morbidity and mortality as well as significant hospital resource utilization.

METHODS

We analysed a prospectively collected database containing all adult cardiac surgery procedures performed from July 2001 to March 2011 at Monash Medical Centre and Jessie McPherson Private Hospital. Patients with post-operative GI complications were compared to patients without GI complications who were operated in the same period.

RESULTS

The incidence of GI complications was 1.1% (61 out of 5382 patients) with an overall 30-day mortality of 33% (versus 3% in the non-GI complication group). The most common complications were GI bleeding, gastroenteritis and bowel ischaemia. Patients who had GI complications were significantly older, had higher incidence of renal impairment, chronic lung disease and anticoagulation therapy and were more likely to be in cardiogenic shock. Emergency procedures, combined coronary artery bypass grafting and valve surgery and aortic dissection cases were more common in the GI complication group. The GI complication group also had higher incidence of return to theatre, renal failure, stroke, septicaemia and multi-organ failure.

CONCLUSIONS

GI complications after cardiac surgery remain an uncommon but dreadful complication associated with high mortality. Our findings should prompt a high degree of clinical vigilance in order to make an early diagnosis especially in high risk patients. Further studies aiming to identify independent predictors for GI complications after cardiac surgery are warranted.

The complement system in ischemia-reperfusion injuries

Tissue injury and inflammation following ischemia and reperfusion of various organs have been recognized for many years. Many reviews have been written over the last several decades outlining the role of complement in ischemia/reperfusion injury. This short review provides a current state of the art knowledge on the complement pathways activated, complement components involved and a review of the clinical biologics/inhibitors used in the clinical setting of ischemia/reperfusion. This is not a complete review of the complement system in ischemia and reperfusion injury but will give the reader an updated view point of the field, potential clinical use of complement inhibitors, and the future studies needed to advance the field.

Increased cerebral blood flow velocities assessed by transcranial Doppler examination is associated with complement activation after cardiopulmonary bypass

The role of complement activation on the cerebral vasculature after cardiopulmonary bypass (CPB) is unclear. The goal of the study was to assess whether heparin-coated CPB reduces complement activation, and influences cerebral blood flow velocities (CBFV). Twenty-four patients undergoing coronary surgery were randomly allocated to non-coated (NC-group) or heparin-coated (HC-group) CPB. Complement activation was assessed by measuring sC5b-9. Transcranial Doppler (TCD) was performed on middle cerebral arteries before and after CPB. Systolic (SV), diastolic (DV) and mean (MV) CBFV were measured. Significant increase of sC5b-9 (p=0.003) was observed in the NC-group and CBFV increased after CPB (SV by 27%, p=0.05; DV by 40%, p=0.06; MV by 33%, p=0.04) whereas no changes were detected in the HC-group. TCD values were higher in the NC-group than in the HC-group (SV, p=0.04; DV, p=0.03; MV, p=0.03) although cardiac index, systemic vascular resistance, haematocrit and pCO2 were similar. Postoperative SV, DV and MV were significantly correlated with sC5b-9 (r=0.583, p=0.009; r=0.581, p=0.009; r=0.598, p=0.007, respectively). Increased CBFV after CPB are correlated to the level of complement activation and may be controlled by heparin-coated circuits.

Differential effects on the mesenteric microcirculatory response to vasopressin and phenylephrine after cardiopulmonary bypass

OBJECTIVE

Mesenteric ischemia is a rare but potentially devastating complication of cardiac surgery with cardiopulmonary bypass. We hypothesized that alterations in mitogen-activated protein kinase pathways contribute to mesenteric microcirculatory dysfunction resulting from cardiopulmonary bypass.

METHODS

Pigs underwent cardiopulmonary bypass (n = 6) for 90 minutes and postbypass reperfusion for 180 minutes. Sham operations (n = 6) were performed on controls. Mesenteric tissue was harvested before bypass and after postbypass reperfusion. Microvascular contraction to phenylephrine and vasopressin was examined by videomicroscopy. Contractile responses with inhibition of the extracellular regulated kinase 1/2 (ERK1/2) pathway by PD98059 (30 micromol/L) and p38 kinase inhibition by SB203580 (1 micromol/L) also were determined. Activated forms of ERK1/2 and p38 kinase were measured by Western blot. ERK1/2 and p38 activity were localized in mesenteric tissue by immunohistochemistry.

RESULTS

Contractile responses to phenylephrine were increased at 180 minutes after cardiopulmonary bypass (+49.7% +/- 5.5%, P < .01), whereas contraction to vasopressin was unchanged. ERK1/2 pathway inhibition reduced contractile responses to phenylephrine at baseline and 180 minutes after bypass (both P < .01) but had no effect on contraction to vasopressin. p38 Kinase inhibition decreased the contractile responses to vasopressin at baseline and 180 minutes after bypass (both P < .01) but did not alter the contractile response to phenylephrine. Activated ERK1/2 levels were increased by more than 40% at 180 minutes after bypass (P < .01). Protein levels of activated p38 kinase were not changed. The increased ERK1/2 activity was associated with mesenteric arterioles by immunohistochemistry.

CONCLUSIONS

A differential pattern of mesenteric vasomotor regulation exists after cardiopulmonary bypass that may contribute to the risk of mesenteric ischemia after cardiac surgery.

Gastrointestinal dysfunction following cardiac surgery

Cardiac surgery is associated with a low incidence of GI complications, but with a disproportionate mortality. A number of risk factors have become established which identify patients at risk. CPB is associated with profound reductions in mucosal blood flow. Mesenteric perfusion is altered by primary endothelial dysfunction, which may further be exacerbated by the use of vasoconstrictors during CPB; inflammatory mediators can 'prime' the mesenteric vasculature. Cardiac surgery with or without CPB is associated with increased tissue oxygen demands, particularly by the splanchnic bed. The disparity in general and regional oxygen supply and demand results in the development of mucosal hypoxia and this cannot be attributed to CPB alone. This injury is measurable by reductions in both absorptive and barrier functions of the gut. Protection may be conferred by modulating the perfusion protocol during bypass and pharmacological interventions which modify the inflammatory response to surgery.

MESENTERIC VASCULAR DYSFUNCTION AFTER CARDIOPULMONARY BYPASS WITH CARDIAC ARREST IS AGGRAVATED BY COEXISTENT HEART FAILURE

Although patients suffering from heart failure (HF) have an increased incidence of nonocclusive mesenteric ischemia after opened heart surgery, the impact of cardiopulmonary bypass with cardiac arrest (CPB) on mesenteric vascular circulation in such situation remains unexplored. Therefore, the present study investigates the effects of CPB on mesenteric vascular reactivity, regional metabolism, and oxidative stress in an experimental model of HF. Volume-overload HF was induced in six dogs by bilateral femoral arteriovenous fistula. Six sham-operated dogs were used as controls. Eight weeks later, the short-term effects of 90 min of CPB were assessed in vivo during acute experiments. The significant increase in left ventricular end-diastolic volume in HF animals did not influence the vasodilator response of the superior mesenteric artery to acetylcholine (ACH) and nitroprusside (SNP) under baseline conditions. However, reduced mesenteric oxygen delivery, increased oxygen extraction, and lactate release were found during CPB in the HF group. In addition, an increased free radical production was assessed in the HF group during (89 +/- 23 x 10 relative light units [RLU]) and after CPB (93 +/- 15 x 10 RLU) compared with controls (45 +/- 15 and 49 +/- 7 x 10 RLU, respectively). Finally, 90 min of CPB led to a more pronounced decrease of ACH- (-22% +/- 5% vs. -42% +/- 9%, P < 0.05) and SNP- (-14% +/- 4% vs. -50% +/- 7%, P < 0.002) induced mesenteric vasodilations in the HF group compared with controls. We conclude that coexistent HF significantly enhances the pathological effects of CPB on the mesenteric vascular circulation by additionally altering endothelial and smooth muscle vascular function consequent to augmented oxidative stress.

Poly(ADP-ribose) polymerase inhibitor PJ-34 reduces mesenteric vascular injury induced by experimental cardiopulmonary bypass with cardiac arrest

The aim of this study was to investigate effects of poly(ADP-ribose) polymerase (PARP) inhibition on mesenteric vascular function and metabolism in an experimental model of cardiopulmonary bypass (CPB) with cardiac arrest. Twelve anesthetized dogs underwent 90-min hypothermic CPB. After 60 min of cardiac arrest, reperfusion was started for 40 min following application of either saline vehicle (control, n = 6) or a potent PARP inhibitor, PJ-34 (10 mg/kg iv bolus and 0.5 mg.kg(-1).min(-1) infusion for 20 min, n = 6). PJ-34 led to better recovery of cardiac output (2.2 +/- 0.1 vs. 1.8 +/- 0.2 l/min in control) and mesenteric blood flow (175 +/- 38 vs. 83 +/- 4 ml/min, P < 0.05 vs. control) after reperfusion. The impaired vasodilator response of the superior mesenteric artery to acetylcholine, assessed in the control group after CPB (-32.8 +/- 3.3 vs. -57.6 +/- 6.6% at baseline, P < 0.05), was improved by PJ-34 (-50.3 +/- 3.6 vs. -54.3 +/- 4.1% at baseline, P < 0.05 vs. control). Although plasma nitrate/nitrite concentrations were not significantly different between groups, mesenteric nitric oxide synthase activity was increased in the PJ-34 group (P < 0.05). Moreover, the treated group showed a marked attenuation of mesenteric venous plasma myeloperoxidase levels after CPB compared with the control group (75 +/- 1 vs. 135 +/- 9 ng/ml, P < 0.05). Pharmacological PARP inhibition protects against development of post-CPB mesenteric vascular dysfunction by improving hemodynamics, restoring nitric oxide production, and reducing neutrophil adhesion.

Abdominal organ injury after cardiac surgery

Gastrointestinal complications occur in about 2.5% of patients undergoing cardiac surgery, are associated with a high mortality (about 33%), and account for nearly 15% (and perhaps increasing) of all postoperative deaths. The various complications and risk factors are reviewed. Splanchnic ischemia prior to, during, and especially postoperatively appears to be an important cause of these complications. In addition, splanchnic ischemia is hypothesized to be one cause of the systemic inflammatory response syndrome and multiorgan failure that may follow cardiac surgery. The physiology of splanchic perfusion and the effects of cardiac surgery, including cardiopulmonary bypass, on it are reviewed. Finally, possible methods to minimize splanchnic ischemia and reduce the incidence of abdominal complications are discussed.

Mesenteric injury after cardiopulmonary bypass: Role of poly(adenosine 5′-diphosphate-ribose) polymerase*

OBJECTIVES

To investigate the effects of the ultrapotent poly(adenosine 5'-diphosphate-ribose) polymerase (PARP) inhibitor INO-1001 on cardiac and mesenteric function during reperfusion in an experimental model of cardiopulmonary bypass with cardioplegic arrest.

DESIGN

Prospective, randomized, and blinded experimental study.

SETTING

Research laboratory.

SUBJECTS

: Twelve anesthetized dogs underwent cardiopulmonary bypass with hypothermic cardioplegic cardiac arrest.

INTERVENTIONS

After 60 mins of hypothermic cardiac arrest, either PARP inhibitor INO-1001 (1 mg/kg, n = 6) or vehicle (control, n = 6) was administered during reperfusion.

MEASUREMENTS AND MAIN RESULTS

Left ventricular hemodynamic variables were measured by combined pressure-volume-conductance catheters. Coronary and mesenteric blood flow and vasodilatory responses to acetylcholine and sodium nitroprusside as well as mesenteric lactate and creatinine phosphokinase release were also determined. The administration of INO-1001 led to a significantly improved recovery of left ventricular systolic function (p < .05) after 60 mins of reperfusion. Coronary and mesenteric blood flow were also significantly higher in the INO-1001 group (p < .05). Although the vasodilatory response to sodium nitroprusside was similar in both groups before and after cardiopulmonary bypass and similar in response to acetylcholine before cardiopulmonary bypass, PARP-inhibited dogs had lower mesenteric vascular resistance after cardiopulmonary bypass (p < .05). Mesenteric lactate and creatinine phosphokinase release was significantly lower in the PARP inhibitor treated group (p < .05).

CONCLUSION

PARP inhibition with INO-1001 improves the recovery of myocardial function and prevents mesenteric vascular dysfunction and tissue injury after cardiopulmonary bypass with hypothermic cardiac arrest.

Changes in mesenteric vascular reactivity and inflammatory response after cardiopulmonary bypass in a rat model

BACKGROUND

Mesenteric ischemia and acidosis leading to intestinal ischemia has been observed during cardiopulmonary bypass (CPB) despite normal flow in the mesenteric vessels. The aim of this study was to assess mesenteric endothelium-dependent reactivity and vasoconstrictor responses of small mesenteric arteries in a rat model of CPB without aortic cross-clamping.

METHODS

After femoral cannulation a partial 90 minutes CPB was performed with hemodynamics and blood gas parameters monitoring. Blood samples and segments of small mesenteric arteries were obtained in rats sacrificed 2.5 hours (CPBH2.5) or 6 hours (CPBH6) after femoral cannulation. Sham surgery (sham H2.5, sham H6) was performed with femoral cannulation only. Segments of small mesenteric arteries were placed in a myograph in order to assess the contractile response to phenylephrine (with or without NO synthase inhibitor) or the endothelium-dependent relaxation to acetylcholine. Systemic inflammation was evaluated by measuring plasma concentrations of TNFalpha. Pulmonary and intestinal infiltration of activated leukocytes was assessed by immunohistochemistry.

RESULTS

CPB induced increased contractile response to phenylephrine which persisted after blockade of NO synthesis as well as transient impairment of endothelium-dependent relaxations. CPB also led to early and marked release of TNFalpha.

CONCLUSIONS

CPB was responsible for mesenteric endothelial dysfunction and direct increase in the contractile response to alpha1-adrenergic agonist with increased systemic inflammatory response. This phenomenon might contribute to an increase in the risk of mesenteric ischemic events during cardiac surgery especially when vasopressor agents are used.

Does off-pump CABG reduce gastrointestinal complications?

BACKGROUND

The aim of this study was to compare gastrointestinal complications and associated risk factors among patients undergoing cardiac surgery using off- and on-pump revascularization techniques.

METHODS

A total of 1146 adult patients who underwent coronary artery surgery during a 6-year period were evaluated retrospectively. Group 1 consisted of 546 patients operated using off-pump techniques and group 2 consisted of 600 cases operated with cardiopulmonary bypass. Patients were compared and evaluated for gastrointestinal complications and possible associated risk factors using univariate and multivariate logistic regression analysis.

RESULTS

Overall mortality was 1.6% in group 1 and 2.2% in group 2 (p = 0.523). Mortality due to gastrointestinal complications was 38.5% and 35.7% respectively in group 1 and group 2. The mean EuroSCORE value was 5.1 +/- 2.8 in group 1 and 3.8 +/- 2.4 in group 2 (p < 0.001). The most common gastrointestinal complication in the off-pump group was gastrointestinal bleeding. The leading complication in group 2 was intestinal ischemia.

CONCLUSIONS

The incidence rates of gastrointestinal complications were similar in the on- and off-pump coronary artery bypass groups, the type of gastrointestinal complications, however, was different. Mortality rate due to these complications was also similar and remained high, regardless of the type of surgery. Cardiopulmonary bypass did not emerge as a risk factor for gastrointestinal complications, but prolonged cardiopulmonary bypass (longer than 98 minutes) resulted in a high incidence of such complications. Old age and advanced arteriosclerosis emerged as risk factors in both groups resulting in gastrointestinal complications suggesting the ischemic nature of the injury.

C5a causes limited, polymorphonuclear cell-independent, mesenteric ischemia/reperfusion-induced injury

C5 is critical in the development of local mucosal damage and inflammation as well as in the development of remote organ injury after mesenteric ischemia/reperfusion (IR). To define the role of C5a in tissue injury, we treated wild-type mice with a cyclic hexapeptide C5a receptor antagonist (C5aRa) and administered recombinant C5a to C5 deficient (C5(-/-)) mice subjected to mesenteric IR. We demonstrate that at 2-h postreperfusion, C5a administered to C5-/- mice during IR induces limited intestinal mucosal injury but failed to cause remote lung injury despite the fact that it upregulated adhesion molecule expression. C5aRa treatment of C5+/+ mice undergoing IR limited local injury and prevented distant organ injury. We conclude that although C5a can trigger certain components of the IR induced injury, other mediators such as C5b-9 and local factors are needed for the complete expression of IR tissue damage.

Cardiopulmonary bypass reduces peripheral microvascular contractile function by inhibition of mitogen-activated protein kinase activity

BACKGROUND

Mitogen-activated protein kinases (MAPK) have been implicated in pathophysiologic responses to cardiopulmonary bypass (CPB). MAPK are deactivated by phosphatases, such as MAPK phosphatase-1 (MKP-1). We hypothesized that MAPK mediate peripheral microvascular contractile dysfunction caused by CPB in humans.

METHODS

Skeletal muscle was harvested before and after CPB. Protein levels of MKP-1 and activated extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 were measured. MKP-1 gene expression was measured. Peripheral microvessel responses to vasopressors were studied by videomicroscopy. Contractile function also was measured after MAPK inhibition with PD98059 (ERK1/2) and SB203580 (p38). ERK1/2, p38, and MKP-1 were localized by immunohistochemistry and in situ hybridization.

RESULTS

ERK1/2 and p38 activity was decreased in peripheral tissue after CPB. MKP-1 was increased after CPB. Contractile responses of peripheral arterioles to phenylephrine and vasopressin were decreased after CPB. Microvessel reactivity also was reduced after treatment with PD98059 and SB203580. ERK1/2, p38, and MKP-1 localized to peripheral arterioles in tissue sections.

CONCLUSIONS

CPB reduces ERK1/2 and p38 activity in peripheral tissue, potentially by MKP-1. Contractile responses of peripheral arterioles to phenylephrine and vasopressin are dependent on ERK1/2 and p38 and are decreased after CPB. These results suggest that alterations in MAPK pathways in part regulate peripheral microvascular dysfunction after CPB in humans.

L-arginine protects the mesenteric vascular circulation against cardiopulmonary bypass-induced vascular dysfunction

BACKGROUND

The aim of our study was to determine whether addition of the nitric oxide donor l-arginine at reperfusion may prevent the cardiopulmonary bypass (CPB)-induced vascular alterations in the intestine.

METHODS

Twelve dogs underwent 90-minute hypothermic CPB. After 60 minutes, the cardiac arrest-treated group (n = 6) received 40 mg/kg intravenous bolus l-arginine, followed by 3 mg/kg/min infusion for 20 minutes. Hemodynamic parameters, blood gases, lactate, and glucose were monitored. Reactive hyperemia (RH) in response to superior mesenteric artery ischemia and vasorelaxation to systemically administered vasoactive drugs (acetylcholine [ACH] and sodium nitroprusside) were assessed before and after CPB and defined as percent change of vascular resistance.

RESULTS

In the control group, CPB reduced reactive hyperemia (RH) (-26 +/- 15% vs -53 +/- 5%), and the response to ACH (-30 +/- 3% vs -42 +/- 7%). In the treated group, the post-CPB endothelial dysfunction was reversed (-37 +/- 1%, P <.05 vs control group) and RH partially recovered (-34 +/- 4%, P <.05). Administration of l-arginine resulted in a higher mesenteric oxygen delivery, increased nitrite/nitrate production, and lower lactate release from the mesenteric vascular circulation after reperfusion.

CONCLUSIONS

CPB disrupts some of the regulatory functions of the endothelial cell in the mesenterium and these are mostly related to nitric oxide unavailability. Systemic supplementation of l-arginine at reperfusion prevents the CPB-induced mesenteric endothelial dysfunction in association with an increased blood distribution and a reduced metabolic impairment.

Mesenteric complications after hypothermic cardiopulmonary bypass with cardiac arrest: underlying mechanisms

The aim of this study was to determine the pathophysiological mechanisms of postcardiopulmonary bypass (CPB) intestinal dysfunction using an in vivo canine model of extracorporeal circulation. Six dogs underwent a 90 min hypothermic CPB with continuous monitoring of mean arterial blood pressure (MAP) and mesenteric blood flow (MBF). Reactive hyperemia and vasodilator responses of the superior mesenteric artery to acetylcholine and sodium nitroprusside were determined before and after CPB. Mesenteric lactate production, glucose consumption, creatine kinase (CK) release and venous free radicals were determined. CPB induced a significant fall (p < 0.05) in MAP and MBF. After CPB, reactive hyperemia (-26 +/- 15% versus -53 +/- 2%, p < 0.05) and the response to acetylcholine (-42 +/- 9 versus -55 +/- 6%, p < 0.05) were significantly decreased. Reperfusion increased lactate production (0.8 +/- 0.09 mmol/L versus 0.4 +/- 0.18, p < 0.05) and the CK release (446 +/- 98 U/L versus 5 +/- 19 U/L, p < 0.01). Endothelial dysfunction, conversion from aerobic to anaerobic metabolism, and intestinal cell necrosis seem to be responsible for intestinal complications associated with CPB.

Dopexamine attenuates microvascular perfusion injury of the small bowel in pigs induced by extracorporeal circulation

BACKGROUND

Cardio-thoracic surgery with the use of extracorporeal circulation may lead to an impairment of splanchnic perfusion. The aim of this study was to investigate the effect of dopexamine on gastrointestinal microvascular perfusion failure due to extracorporeal circulation.

METHODS

Twenty landrace pigs served as laboratory animals. A loop of the terminal ileum was exteriorized for microscopic observation. In 13 animals a partial left-heart bypass (pLHB), with a non-pulsatile pump flow of approximately 50% of the cardiac output, was established for 2 h. Seven animals received a continuous i.v. infusion of 3 micrograms kg-1 min-1 dopexamine from the beginning of pLHB to the end of the experiment. Seven sham-operated animals served as controls. The microcirculatory network was analysed by means of intra-vital microscopy prior to, during pLHB, and 2 h after bypass.

RESULTS

Despite normal haemodynamics measured by arterial pressure and cardiac output, pLHB led to significant impairment of microvascular perfusion characterized by arteriolar vasoconstriction, reduction of functional capillary density (FCD) to 30% 2 h after weaning off bypass and diminished blood-cell velocities in submucous venules. Dopexamine attenuated this perfusion impairment, preventing arteriolar vasoconstriction. FCD remained normal.

CONCLUSION

Our data demonstrate that treatment with the vasoactive drug dopexamine leads to a significant reduction of the perfusion injury of the small bowel.

Expression of vascular endothelial growth factor and its receptors is increased, but microvascular relaxation is impaired in patients after acute myocardial ischemia

BACKGROUND

Vascular endothelial growth factor, a specific endothelial mitogen, plays an important role in myocardial angiogenesis. Previous work has demonstrated increased expression of vascular endothelial growth factor and its receptors in a rat myocardial infarction model, as well as in a pig model of chronic ischemia. The expression of vascular endothelial growth factor and other growth factors after acute myocardial ischemia in patients has not been examined. In this study we examined the expression of vascular endothelial growth factor and its receptors and the responsiveness of human atrial microvessels to vascular endothelial growth factor before and after acute ischemia.

METHODS

Paired specimens of human atrial tissue were harvested before and after atrial devascularization (ligation) in 16 patients undergoing coronary bypass operations.

RESULTS

The messenger RNA (reverse transcriptase-polymerase chain reaction) level of vascular endothelial growth factor and vascular endothelial growth factor receptor 1 were increased by 22.2% +/- 4.2% and 30.7% +/- 7.6%, respectively (P <.05), in the ischemic specimens as compared with the control specimens. Protein expression (Western blotting) of vascular endothelial growth factor and that of vascular endothelial growth factor receptor 1 also were increased significantly by 71.7% +/- 27.8% and 68.2% +/- 27.6%, respectively (P <.05). However, both RNA and protein expressions of another vascular endothelial growth factor receptor, vascular endothelial growth factor receptor 2, and fibroblast growth factor and fibroblast growth factor receptor 1 were unchanged. Reactivity of precontracted atrial vessels was examined with video microscopy. Vascular endothelial growth factor-induced (33.9% +/- 2.4% vs 18.3% +/- 2.8% in control and ischemic vessels, respectively; P <.05), fibroblast growth factor-induced (31.6% +/- 3.2% vs 15.8% +/- 4.1%, P <.05), and substance P-induced (84.5% +/- 3.7% vs 54.3% +/- 9.0%, P <.05) microvascular relaxations were decreased in ischemic samples and in the presence of N (G)nitro-L -arginine, whereas responses to sodium nitroprusside were unchanged (90.9% +/- 2.2% vs 91.2% +/- 2.0%).

CONCLUSIONS

This study suggests that acute myocardial ischemia in patients results in increased expression of vascular endothelial growth factor but not fibroblast growth factor and that the functional activity of vascular endothelial growth factor receptors and that of other growth factors may be impaired.