The systemic factor: the comparative roles of cardiopulmonary bypass and off-pump surgery in the genesis of patient injury during and following cardiac surgery

Oxidative Stress in Patients before and after On-Pump and Off-Pump Coronary Artery Bypass Grafting: Relationship with Syntax Score

Objective

Coronary artery bypass grafting (CABG) represents the significant source of increased oxidative stress (OS). We aimed to follow the OS status parameters (i.e., ischemia-modified albumin (IMA), malondialdehyde (MDA), superoxide anion, prooxidant-antioxidant balance (PAB), total oxidant status (TOS), total antioxidant status (TAS), and superoxide-dismutase (SOD)) change through the predefined study times in two different surgical procedures, i.e., cardiopulmonary bypass (CPB) and off-pump coronary artery bypass grafting (OPCAB). Additionally, we aimed to investigate those OS status parameters in specific study times according to SYNTAX score (SS), an established angiographic score for evaluating the extensity and severity of coronary artery disease. Patients and Methods. A total of 107 patients that were planned to undergo CABG were included (i.e., 47 patients in OPCAB and 60 patients in CPB group). Blood samples were taken at 6 time intervals: before surgery (t1), immediately after intervention (t2), 6 h (t3), 24 h (t4), 48 h (t5), and 96 h after termination of the operation (t6).

Results

IMA levels were higher in CPB than that in OPCAB baseline and rose in CPB group in t2 point. TOS decreased in both study groups, compared to baseline values, but without statistical significance. Superoxide anion and PAB significantly increased in t3-t6 study times, in both groups. MDA significantly increased only in CPB group in t5 and t6 interval. MDA was significantly higher in CPB group compared to OPCAB in t6 study point. CPB patients had significantly lower TAS compared to OPCAB patients at the beginning and in t2 and t3 study points. They also had significantly lower SOD activities compared to OPCAB, baseline, and in several study points. Moreover, TAS, SOD, and TAS/TOS ratio were significantly lower, whereas PAB and TOS/TAS were significantly higher in patients with high SS compared to corresponding groups. SOD activity, IMA, and TAS level were the best predictors of high SS.

Conclusion

CPB patients were in more severe ischemia baseline than OPCAB group and IMA rose in CPB patients immediately after the surgery end, but not later. Also, the antioxidant status was significantly lower, whereas the prooxidant status was significantly higher in patients with high SS compared to corresponding groups. SOD activity, IMA, and TAS level were the best predictors of CAD (as determined with SS), showing that SOD and IMA had very good discriminatory capability towards higher SS status.

Hsa-miR-494-3p attenuates gene HtrA3 transcription to increase inflammatory response in hypoxia/reoxygenation HK2 Cells

The occurrence of cardiac surgery-associated acute kidney injury (CSA-AKI) increases hospital stay and mortality. MicroRNAs has a crucial role in AKI. This objective of the current study is to explore the function of hsa-miR-494-3p in inflammatory response in human kidney tubular epithelial (HK2) cells with hypoxia/reoxygenation. According to KDIGO standard, patients after cardiac surgery with cardiopulmonary bypass were divided into two groups: AKI (n = 10) and non-AKI patients (n = 8). HK2 were raised in the normal and hypoxia/reoxygenation circumstances and mainly treated by overexpression ofmiR-494-3p and HtrA3. The relationship between miR-494-3p and HtrA3 was determined by dual-luciferase reporter assay. Our result showed that Hsa-miR-494-3p was elevated in the serum of patients with CSA-AKI, and also induced in hypoxic reoxygenated HK2 cells. Hsa-miR-494-3p also increased a hypoxia-reoxygenation induced inflammatory response in HK2 cells. Moreover, as a target gene of miR-494-3p, overexpression of HtrA3 downregulated the hypoxia-reoxygenation induced inflammatory response in HK2 cells. Overexpression of hsa-miR-494-3p-induced inflammatory response was inhibited by overexpression of HtrA3. Collectively, we identified that hsa-miR-494-3p, a miRNA induced in both circulation of AKI patients and hypoxia-reoxygenation-treated HK2 cells, enhanced renal inflammation by targeting HtrA3, which may suggest a possible role as a new therapeutic target for CSA-AKI.

The Pathophysiology of Cardiac Surgery-Associated Acute Kidney Injury (CSA-AKI)

Cardiac surgery associated acute kidney injury (CSA-AKI) is a significant clinical problem. Its pathogenesis is complex and multifactorial. It likely involved at least six major injury pathways: exogenous and endogenous toxins, metabolic factors, ischemia and reperfusion, neurohormonal activation, inflammation and oxidative stress. These mechanisms of injury are likely to be active at different times with different intensity and probably act synergistically. Because of such complexity and the small number of randomised controlled investigations in this field only limited recommendations can be made. Nonetheless, it appears important to avoid nephrotoxic drugs and desirable to avoid hyperglycemia in the peri-operative period. The duration of cardiopulmonary bypass should be limited whenever possible. Off-pump surgery, when indicated, may decrease the risk of AKI. Invasive hemodynamic monitoring focussed on attention to maintaining euvolemia, an adequate cardiac output and an adequate arterial blood pressure is desirable. Echocardiography may be useful in minimizing atheroembolic complications. The administration of N-acetylcysteine to protect the kidney from oxidative stress is not recommended. There is marked lack of randomised controlled trials in this field.

Off-Pump Revascularization for Significant Left Ventricular Dysfunction

Left ventricular dysfunction is a predictor of perioperative morbidity and mortality in on-pump coronary artery bypass grafting. Obligatory global myocardial ischemia and injury induced during crossclamping as well as adverse systemic effects of cardiopulmonary bypass may induce a disproportionately greater overall physiologic insult in patients with poor ventricular function. All patients undergoing nonemergency off-pump coronary artery bypass by a single surgeon during an 18-month period were retrospectively analyzed. Two groups with preoperative ejection fraction classified as poor (10%–35%; n = 31) or normal (55%–80%; n = 60) were compared. The mean ejection fractions were 26% ± 1% and 63% ± 1% respectively, p < 0.000001. In those with significant left ventricular dysfunction, there were 2.8 ± 0.1 grafts per patient, time to extubation was 8.4 ± 1.2 hours, and discharge was after 4.9 ± 0.6 days. These results were statistically equivalent to those in the group with normal left ventricular function. There was no intraaortic balloon pump insertion or mortality in either group. This technique provides an effective means of safely revascularizing patients with significant left ventricular dysfunction, and it may provide a valuable alternative approach in patients with ischemic cardiomyopathy.

Urine catalytic iron and neutrophil gelatinase-associated lipocalin as companion early markers of acute kidney injury after cardiac surgery: a prospective pilot study

BACKGROUND

Open heart surgery with cardiopulmonary bypass is recognized as a common cause of acute kidney injury (AKI). The conventional biomarker creatinine is not sensitive enough to detect AKI until a significant decline in renal filtration has occurred. Urine neutrophil gelatinase-associated lipocalin (NGAL), part of an acute response to the release of tissue iron from cells, is an early biomarker and a predictor of AKI in a variety of clinical settings. We sought to evaluate the relationship between urine catalytic iron (unbound iron) and NGAL over the course of AKI due to cardiac surgery.

METHODS

FOURTEEN PATIENTS WHO UNDERWENT OPEN HEART SURGERY HAD THE FOLLOWING MEASURED: serum creatinine (0, 12, 24, 48 and 72 h postoperatively), urine NGAL and urine catalytic iron (0, 8, 24 and 48 h postoperatively). Urine NGAL and urine catalytic iron were quantified by immunoassay and bleomycin-detectable iron assay, respectively. AKI was defined by the Acute Kidney Injury Network (AKIN) criteria.

RESULTS

Urine catalytic iron increased significantly (p < 0.05) within 8 h and peaked at 24 h postoperatively in patients who developed AKI (n = 8, baseline 101.96 ± 177.48, peak 226.35 ± 238.23 nmol/l, p = 0.006), but not in non-AKI patients (n = 6, baseline 131.08 ± 116.21, peak 163.99 ± 109.62 nmol/l, p = 0.380). Urine NGAL levels also peaked at 24 h with significant increase observed only in AKI patients: AKI - baseline 34.88 ± 26.47, peak 65.50 ± 27.03 ng/ml, p = 0.043; non-AKI - baseline 59.33 ± 31.72, peak 71.00 ± 31.76 ng/ml, p = 0.100. The correlation between baseline levels of urine catalytic iron and NGAL and peak levels of urine catalytic iron and NGAL was r = 0.86, p < 0.0001.

CONCLUSION

Urine catalytic iron appears to rise and fall in concert with NGAL in patients undergoing cardiac surgery and may be indicative of early AKI. Future research into the role that catalytic iron plays in acute organ injury syndromes and its potential diagnostic and therapeutic implications is warranted.

Analysis of inflammatory response and utility of N-terminal pro brain-type natriuretic peptide in cardiac surgery with extracorporeal circulation

OBJECTIVES

Cardiac surgery with cardiopulmonary bypass (CPB) elicits an inflammatory response. During and after cardiac surgery, we examined the pattern of cytokine release of interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-alpha, to investigate inflammatory response. We analyzed N-terminal pro brain-type natriuretic peptide (NT-proBNP) as a marker of ventricular function.

METHODS

Consecutive patients (n = 58) undergoing elective cardiac surgery with extra-corporeal circulation were recruited into the study. Blood samples for analysis of the biochemical markers were taken at seven time points for cytokines and TNF, and three for Nt-proBNP.

RESULTS

All markers increased significantly after CPB. IL-6 and IL-8 levels were higher in men. IL-8 was related to a need for inotropic support. IL-6 was related to the time of CPB (P = 0.004), aortic clamping (P = 0.013), length of stay in intensive care unit (ICU) (P = 0.004) and mechanical ventilation for more than 12 h (P = 0.006). The levels of NT-proBNP were higher in cases of ventricular dysfunction (P = 0.003) and functional class III/IV (P = 0.001). The postoperative values were related to age (P < 0.05), creatinine values (P < 0.001), mechanical ventilation time (P < 0.001) and stay in the ICU (P = 0.001).

CONCLUSION

Our data indicate a relationship between cytokine levels and sex, time of CPB and aortic clamping, The increase of cytokines correlates with a need for inotropic support, mechanical ventilation and length of stay in ICU. We confirmed the predictive role, and its utility in the risk stratification of the NT-proBNP, and its importance in early diagnosis of postoperative ventricular dysfunction.

Rationale, design and methodology for a Prospective Randomized Study of graft patency in Off-pump and On-pump MultI-vessel coronary artery bypasS Surgery (PROMISS) using multidetector computed tomography

Background

Off-pump coronary artery bypass grafting has been accused of possibly compromising graft patency. Sixteen slice computed tomography has shown good diagnostic accuracy in the assessment of coronary bypass graft patency when compared with conventional coronary artery angiography and is less invasive. The study hypothesis is that coronary artery bypass grafting (CABG) performed without cardiopulmonary bypass (Off-Pump) has equivalent early graft patency as if performed with cardiopulmonary bypass (On-Pump) and may have reduced complication rate.

Methods/Design

The Prospective Randomized Comparison of Off-Pump and On-Pump MultI-vessel Coronary Artery BypasS Surgery (PROMISS) is a controlled, single blinded, single centre clinical trial, comparing early graft patency using 16-slice computed tomography in patients with multi-vessel coronary artery disease operated either without or with extracorporeal circulation. Inclusion criteria are multivessel disease with an indication for first time, isolated, non emergent coronary artery bypass grafting with a minimum of three distal anastomoses. Secondary end points are peri-operative mortality, combined morbidity, length of stay, neuro-cognitive testing at 6 weeks and adverse events, stress test and quality of life at 6 months and one year. The sample size of one hundred and fifty patients was calculated in order to enable the detection of a 5% difference in graft patency, with 80% power, considering a minimum of 3 distal anastomoses per patient. Enrolment started in April 2005 and ended July 2007 with study closure in July 2008.

Conclusion

The PROMISS trial aims to shed new light on the effect of Off-Pump as compared to On-Pump coronary artery bypass surgery on graft patency, assessed by multidetector computed tomography, in unselected patients with multivessel coronary artery disease.

Trial Registration

Current Controlled Trials ISRCTN58800729

Patterns of Postoperative Systemic Vascular Resistance in a Randomized Trial of Conventional On-Pump Versus Off-Pump Coronary Artery Bypass Graft Surgery

BACKGROUND

Off-pump coronary artery bypass grafting (OPCAB) is associated with a less intense systemic inflammatory response according to biochemical markers. We studied systemic vascular resistance (SVR) as a physiologic response to systemic inflammatory response to determine any differences between OPCAB and on-pump coronary artery bypass grafting (ONCAB) in a prospective randomized trial.

METHODS

One hundred consecutive patients were randomized to OPCAB or ONCAB, 50 in each group. Antifibrinolytics and steroids were not used. All protocols were identical except for cardiopulmonary bypass. Temperature, SVR index, cardiac index, and blood pressure were measured continuously for the first 24 hours postoperatively. All patients were reviewed at 30 days.

RESULTS

There was no 30-day mortality, no stroke, and no acute renal failure. Mean temperature peaked at 37.5 degrees C at 12 hours (p = 0.700 between groups). Mean SVR index fell to 1,900 dyne x cm(-5) x m(-2) at 12 to 18 hours; 42% of OPCAB and 32% of ONCAB patients developed very low SVR index (<1,500 dyne x cm(-5) x m(-2)). The incidence of high SVR (>2,500 dyne x cm(-5) x m(-2)) fell from 20% to 2% by 12 to 18 hours. The extent and pattern of SVR index responses were similar in both groups (p = 0.840). Mean cardiac index peaked at 3.0 L x min(-1) x m(-2), 12 to 18 hours postoperatively (p = 0.815 between groups); 84% of OPCAB and 90% of ONCAB had cardiac index greater than 2.2 L x min(-1) x m(-2) at all times. Only 10% of patients required vasopressors. Blood pressure responses were also similar (p = 0.314).

CONCLUSIONS

The incidence of low SVR, and patterns of SVR changes were similar in ONCAB and OPCAB, and were clinically unimportant as few patients required vasopressor support. Cardiac outputs and clinical outcomes were excellent in both groups.

Early administration of clopidogrel is safe after off-pump coronary artery bypass surgery

BACKGROUND

Patients who undergo off-pump coronary artery bypass graft surgery (OPCAB) may be hypercoagulable with an increased risk of graft thrombosis due to the lack of platelet dysfunction that accompanies "on-pump" surgery. Clopidogrel may be indicated in these patients to prevent recurrent ischemic events. The purpose of this observational study was to determine the safety of early clopidogrel administration after OPCAB.

METHODS

Thirty-day follow-up of 364 consecutive OPCAB patients (January to June, 2002) was determined from a computerized database. One hundred ninety-three patients received clopidogrel 4 hours postoperatively if chest tube output was less than 100 cc/h for 4 hours, then daily for 4 weeks. Aspirin was administered preoperatively and postoperatively to all patients. Telephone follow-up was made 6 to 12 months after OPCAB.

RESULTS

None of the patients who received clopidogrel in the early postoperative period required reoperation for mediastinal hemorrhage. Mean chest tube drainage at 24 hours was 1,024 +/- 563 mL in patients who received clopidogrel and 942 +/- 501 mL in patients who did not receive clopidogrel. The total number of blood units transfused and the number of patients receiving blood transfusions were similar between groups. In-hospital mortality was 1.6% in patients who received clopidogrel and 3.5% in patients who did not receive clopidogrel. No group differences in mortality or adverse cardiac events were observed at 6 months. Gastrointestinal bleeding occurred in 2.2% clopidogrel patients versus 0.7% of patients who did not receive clopidogrel.

CONCLUSIONS

When administered according to our postoperative protocol, OPCAB patients can safely receive clopidogrel in the early postoperative period without increased risk for mediastinal hemorrhage.

Microbiologically documented nosocomial infections after coronary artery bypass surgery without cardiopulmonary bypass

OBJECTIVE

This study was undertaken to evaluate the frequency, characteristics, and risk factors of microbiologically documented nosocomial infections after off-pump coronary artery bypass grafting.

METHODS

A prospective cohort study was performed at Henry Dunant Hospital, Athens, Greece. It included all adult patients who underwent coronary artery bypass grafting with no valve surgery and without the use of cardiopulmonary bypass during a period of 3 years. Case patients were those with development of microbiologically documented nosocomial infections. Various variables were examined as possible risk factors for nosocomial infections.

RESULTS

Twenty-one of 782 studied patients (2.7%) acquired 26 microbiologically documented nosocomial infections after off-pump coronary artery bypass grafting. Eight of 782 studied patients had pneumonia (1.02%), 7 of 782 (0.90%) had bacteremia, 4 of 782 (0.51%) had superficial wound infection at the sternotomy site, 4 of 782 (0.51%) had urinary tract infection, 2 of 782 (0.26%) had mediastinitis, and 1 of 782 (0.13%) had pressure sore infection. Twenty-one infections were monomicrobial, whereas 5 were polymicrobial. All polymicrobial infections were wound infections. There was a statistically significant difference in mortality between patients with and without nosocomial infection (23.8% vs 1.2%, P < .001). Clinical response of the infection to the treatment administered was observed in 21 of 26 episodes (80.8%) in 21 patients. A backward stepwise multivariable logistic regression model showed that independent risk factors (P < .05) associated with development of microbiologically documented nosocomial infection were arterial hypertension, previous vascular surgery, urgent operation, postoperative atrial fibrillation, number of inotropes used during and after operation, transfusion of fresh-frozen plasma during the intensive care unit stay, and intensive care unit stay until development of infection.

CONCLUSION

Nosocomial infection after off-pump coronary artery bypass grafting is an uncommon but potentially life-threatening complication. The identification of independent risk factors, including arterial hypertension, associated with development of postoperative infection may help in the development of clinical strategies for the prevention, early diagnosis, and treatment of these infections.

Brain injury and neuropsychological outcome after coronary artery surgery are affected by complement activation

BACKGROUND

The impact of the postoperative inflammatory response on the central nervous system after cardiac surgery is uncertain. The goal of the study was to evaluate the role of complement activation on cellular brain injury in patients undergoing coronary artery bypass grafting. In addition, neuropsychological functioning was assessed.

METHODS

We randomly assigned 30 patients to undergo surgery using either standard noncoated or heparin-coated extracorporeal circuits. Closed cardiopulmonary bypass and controlled suctions of pericardial shed blood were standardized in both groups. Complement activation and cellular brain injury were assessed by measuring sC5b-9 and protein s100beta. Neuropsychometric tests were performed at least 2 weeks before operation and at discharge. They served to calculate z scores of cognitive domains and changes in neuropsychological functioning.

RESULTS

Peak value of sC5b-9 at the end of cardiopulmonary bypass in the noncoated group was significantly higher than in the heparin-coated group (p = 0.005). Changes in the heparin-coated group were not significant. Glial injury started after initiation of surgery and peaked at the end of cardiopulmonary bypass with significantly higher concentration of s100beta in the noncoated than in the heparin-coated group (p = 0.008). Values of s100beta and of sC5b-9 were significantly correlated (p = 0.03). Although no statistically significant between group difference was detected, z scores of attention and flexibility or executive functions were lowered postoperatively within the noncoated group (p = 0.033 and p = 0.028), whereas z scores were unchanged within the heparin-coated group.

CONCLUSIONS

Inhibition of complement activation by heparin-coated cardiopulmonary bypass reduced brain cell injury and was associated with preserved neuropsychological functioning after coronary artery bypass grafting.

Effects of atorvastatin on systemic inflammatory response after coronary bypass surgery

OBJECTIVES

Systemic inflammatory response occurs frequently after coronary artery bypass surgery, and it is strongly correlated with the risk of postoperative morbidity and mortality. Recent studies demonstrate that treatment with statin is associated with a significant and marked decrease in inflammation-associated variables such as the C-reactive protein, cytokines, and adhesion molecules. Therefore, we investigated the effects of preoperative atorvastatin treatment on systemic inflammatory response and perioperative morbidity after cardiopulmonary bypass.

DESIGN

Double-blinded, placebo-controlled, randomized study.

SETTING

University hospital.

PATIENTS

Forty patients were randomized to treatment with atorvastatin (20 mg/day, group A, n=20) or placebo (group B, n=20) 3 wks before surgery.

INTERVENTIONS

Three-week treatment by atorvastatin 20 mg/day.

MEASUREMENT AND MAIN RESULTS

Postoperative serum levels of both interleukin-6 and interleukin-8 increased significantly over baseline, but the peak levels observed 4 hrs postoperatively were significantly lower in the atorvastatin group. In the same fashion, CD11b expression on neutrophils was significantly lower in the statin group at 4 and 24 hrs postoperatively. Finally, neutrophil-endothelial adhesion was significantly reduced in the statin patients compared with controls. The operation time, blood loss, need for inotropic support, intubation time, and length of intensive care unit or hospital stay did not differ significantly between the two groups. The systemic inflammatory response syndrome score on postoperative days 1 and 2 was comparable in both groups.

CONCLUSIONS

Pretreatment with atorvastatin significantly reduces cytokine release and neutrophil adhesion to the venous endothelium in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass.

[Inflammatory response and haematological disorders in cardiac surgery: toward a more physiological cardiopulmonary bypass]

The systemic inflammatory response in cardiac surgery is closely related to the haemostasis disturbances. It is responsible of a significant morbidity and mortality that was previously suspected to be caused by cardiopulmonary bypass alone. However, it is time now to clearly identify the factors that are material-dependent from that material-independent. From this point of view, off-pump surgery allowed for better comprehension of the multiple sources of the inflammatory response. Numerous pathways are activated, involving complement, platelets, neutrophiles and monocytes. The tissue pathway of the coagulation system, through tissue factor, is of major importance and has to be surgically considered in order to reduce the whole body inflammatory response postoperatively. The quality of the extracorporeal perfusion through its consequences on organ perfusion, particularly in the splanchnic area, also participates to this pathophysiological process. Beyond the progress of technology provided by the industry, particularly the minimally extracorporeal circulation derived from off-pump surgery evolution, the surgical approach is of major importance in the control of the systemic inflammatory response and must not be ignored yet.

Preoperative Statin Therapy and Troponin T Predict Early Complications of Coronary Artery Surgery

BACKGROUND

Pretreatment with statins reduces early ischemic events after percutaneous coronary interventions, primarily in patients with a high level of inflammation markers. We sought to examine the association between preoperative statin therapy, systemic inflammation, and myocardial ischemia with the occurrence of early cardiac complications after coronary artery bypass grafting surgery.

METHODS

One hundred forty-one consecutive patients who underwent coronary artery bypass grafting surgery from two university tertiary hospitals were stratified according to their preoperative status of statin therapy (87 treated and 54 nontreated). Preoperative blood samples were collected for measurement of lipid parameters, C-reactive protein, interleukin-6, and troponin T. The evaluated primary endpoint was a composite of death and myocardial infarction at 30 days.

RESULTS

Patients undergoing preoperative statin therapy showed a reduced incidence of death (2.3% versus 13.0%, p = 0.012), myocardial infarction (5.7% versus 18.5%, p = 0.017), and primary combined endpoint (8.0% versus 22.2%, p = 0.017). In the multivariate model, preoperative troponin T greater than 0.01 ng/mL (odds ratio 6.85, p = 0.001) and nonstatin therapy (odds ratio 4.2, p = 0.01) predicted a higher risk of primary endpoint. Statins showed a significant interaction with troponin T status and benefited primarily those patients with positive troponin T. Among 19 patients with troponin T greater than 0.01 ng/mL, the primary endpoint occurred in all 6 nonstatin-treated patients, but it occurred in only 1 of 13 statin-treated patients (p < 0.001). Neither C-reactive protein nor interleukin-6 predicted early complications, nor did they interact with statin therapy (p = not significant).

CONCLUSIONS

Preoperative statin therapy reduces early complications and offers additional protection in patients with positive troponin T status, regardless of inflammatory markers.

Postoperative Hyperthermia Following Off-Pump Versus On-Pump Coronary Artery Bypass Surgery

OBJECTIVE

Hyperthermia is common in the first 24 hours following coronary artery bypass graft surgery (CABG) with cardiopulmonary bypass (CPB). An inflammatory response to CPB is often implicated in the pathophysiology of this fever. Unlike CABG with CPB, the temperature pattern after off-pump CABG (OPCAB), where CPB is avoided, has not yet been described. The purpose of this study was to describe the postoperative temperature pattern following OPCAB and to compare it with that following on-pump cardiac surgery.

DESIGN

Retrospective, observational study.

SETTING

Tertiary care university hospital.

PARTICIPANTS

Consenting patients undergoing CABG or OPCAB procedures.

INTERVENTIONS

Observational.

MEASUREMENTS AND MAIN RESULTS

Of the CABG patients, 89% had temperature elevations above 38 degrees C, versus 44% of the OPCAB patients (P = 0.04). Peak body temperature was higher in the on-pump patients (CABG 38.5 degrees C +/- 0.4 degrees C versus OPCAB 37.9 degrees C +/- 0.5 degrees C; P = 0.002), as was the area under the curve for temperatures greater than 38 degrees C (CABG 1.6 +/- 1.7 degrees C/hr versus OPCAB 0.4 +/- 1.2 degrees C/hr; P = 0.02).

CONCLUSIONS

Off-pump CABG surgery patients experience less hyperthermia compared with on-pump CABG patients. The reasons for a lower incidence and severity of hyperthermia after OPCAB surgery are not known, but may be related to a reduced inflammatory response.

Off-pump coronary artery bypass grafting does not reduce lymphocyte activation

OBJECTIVE

In this study, we test the hypothesis that off-pump coronary bypass surgery might result in less lymphocyte activation than on-pump coronary surgery. We also study the behavior of lymphocyte activation markers during and after surgery.

BACKGROUND

Coronary artery bypass surgery is known to be associated with changes of inflammatory mediators, immune function, and early phase lymphocyte activation, which could cause postoperative lymphopenia and lymphocyte unresponsiveness.

METHODS

We studied lymphocyte activation response in 28 patients randomized to off-pump (n = 13) or on-pump (n = 15) coronary artery bypass surgery. Expression of CD25, CD26, CD69, and DR on T (CD3+) and B (CD19+) lymphocytes on peripheral blood was assessed through flow cytometry.

RESULTS

The response of T lymphocytes and their activation markers, as well as B lymphocytes and their activation markers, was similar after on- and off-pump surgery. Overall, T lymphocytes decreased to the lowest level 9 h after surgery and tended to increase later. For B lymphocytes, there was early reduction with increase on the 1st postoperative day. There was early activation of CD69+ and late activation of CD25+ on T lymphocytes. For B lymphocytes, there was early activation of CD69+ and late activation of DR+.

CONCLUSIONS

(1) Compared to on-pump cardiopulmonary bypass, off-pump surgery does not reduce lymphocyte activation. (2) Coronary bypass surgery causes the early activation of lymphocytes, as evidenced by the increased expression of lymphocyte activation markers.

Side Effects of Cardiopulmonary Bypass:. What Is the Reality?

Despite many years of clinical and experimental research, the contribution of cardiopulmonary bypass (CPB) and cardioplegic arrest to morbidity and mortality following cardiac surgery remains unclear. This is due, in part, to lack of suitable control group against which bypass and cardioplegic arrest can be compared. The recent success of beating heart coronary artery bypass grafting has, however, for the first time, provided an opportunity to compare the same operation, in similar patient groups, with, or without CPB and cardioplegic arrest. CPB is associated with an acute phase reaction of protease cascades, leucocyte, and platelet activation that result in tissue injury. This is largely manifest as subclinical organ dysfunction that produces a clinical effect in those patients that generate an excessive inflammatory response or in those with limited functional reserve. The contribution of myocardial ischemia/reperfusion, secondary to aortic cross-clamping, and cardioplegic arrest, to the systemic inflammatory response and wider organ dysfunction is unknown, and requires further evaluation in clinical trials.

Supernatant from stored red blood cell primes inflammatory cells: influence of prestorage white cell reduction

BACKGROUND

The contribution of RBC transfusion to adverse patient outcomes is controversial. There is conflicting clinical data and limited biologic data that provide an underpinning biologic rationale for any adverse impacts from RBC transfusion. This study used in-vitro measures of PMN stimulation to determine the ability of supernatant from RBCs to stimulate allogeneic WBCs and to determine the influence of residual donor WBCs and storage time on the proinflammatory potential of RBCs.

STUDY DESIGN AND METHODS

Three types of RBCs were assessed: standard non-WBC-reduced RBCs (S-RBCs), buffy coat-poor RBCs (BCP-RBCs), and prestorage WBC-filtered RBC (LF-RBCs). Supernatant was collected weekly up to Day 42 of storage. PMN priming by supernatant from RBCs was determined by three methods: induction of CD11b expression on PMNs, induction of IL-8 release from PMNs, and the chemotactic effect of supernatant on PMNs.

RESULTS

Supernatant from S-RBCs induced the expression of CD11b on PMNs, primed PMNs to release IL-8, and was chemotactic for PMNs. The magnitude of this PMN-priming progressively amplified with storage time. In contrast, supernatant from BCP-RBCs or LF-RBCs did not significantly prime PMNs. The PMN-priming effect of supernatant from RBCs correlated more closely with the level of MNCs in the RBCs than PMN content.

CONCLUSION

Supernatant from stored S-RBCs prime unstimulated allogeneic PMNs in vitro. Prestorage buffy-coat WBC reduction was as effective as WBC depletion in abrogating this proinflammatory response elicited by supernatants from RBCs. The clinical consequences, if any, of these findings for transfusion recipients are unknown.

Haemodynamic effects of a milrinone infusion without a bolus in patients undergoing off-pump coronary artery bypass graft surgery

The haemodynamic effects of a continuous infusion of milrinone without an initial bolus dose were evaluated in patients undergoing off-pump coronary artery bypass graft surgery. After internal mammary artery harvest, milrinone 0.5 microg.min(-1).kg(-1) (29 patients) or a normal saline infusion (33 patients) was started and continued until all graft anastomoses were completed. Haemodynamic variables were recorded before application of the tissue stabiliser, at 1, 3, 5 and 10 min after the application of the stabiliser, and after its removal. The administration of a milrinone infusion was associated with a smaller decrease in cardiac output and mixed venous oxygen saturation during all the coronary artery anastomoses, with no severe complications and a decreased dose of norepinephrine infused to maintain systemic arterial pressure.

Off-pump coronary artery bypass surgery: physiology and anaesthetic management †

Increasing interest is being shown in beating heart (off-pump) coronary artery surgery (OPCAB) because, compared with operations performed with cardiopulmonary bypass, OPCAB surgery may be associated with decreased postoperative morbidity and reduced total costs. Its appears to produce better results than conventional surgery in high-risk patient populations, elderly patients, and those with compromised cardiac function or coagulation disorders. Recent improvements in the technique have resulted in the possibility of multiple-vessel grafting in all coronary territories, with a graft patency comparable with conventional surgery. During beating-heart surgery, anaesthetists face two problems: first, the maintenance of haemodynamic stability during heart enucleation necessary for accessing each coronary artery; and second, the management of intraoperative myocardial ischaemia when coronary flow must be interrupted during grafting. The anaesthetic technique is less important than adequate management of these two major constraints. However, experimental and recent clinical data suggest that volatile anaesthetics have a marked cardioprotective effect against ischaemia, and might be specifically indicated. OPCAB surgery requires team work between anaesthetists and surgeons, who must be aware of each other's constraints. Some surgical aspects of the operation are reviewed along with physiological and anaesthetic data.

Analysis of thoracic aortic blood flow during off-pump coronary artery bypass surgery

OBJECTIVES

The non-invasive monitoring of thoracic aortic blood flow (TABF) during off-pump coronary artery bypass (OPCAB) surgery is becoming more commonly used and proved to be invaluable in the early detection of haemodynamic compromise due to heart displacement. The aim of this study was to analyze the changes in the TABF during OPCAB using transoesophageal Doppler and compare them with the changes observed by other monitoring methods as cardiac output, invasive pulmonary and radial pressures and mixed venous oxygen saturation.

METHODS

The measurements obtained from classic haemodynamic monitoring methods including the radial artery line and the pulmonary artery catheter with continuous monitoring of the cardiac output and mixed venous blood oxygen saturation were compared to the measurements of TABF obtained from a transoesophageal Doppler probe in 15 consecutive patients who underwent OPCAB surgery.

RESULTS

The TABF decreased significantly during the construction of coronary anastomoses from 3.42 +/- 0.94 l/min (baseline) to 2.2 +/- 0.8 l/min during the first coronary anastomosis and then to 2.14 +/- 1.12 l/min during the second coronary anastomosis (F=4.29, P=0.008). TABF returned to the baseline values (2.85 +/- 1.19 l/min) at chest closure. The cardiac output measurement showed no significant decrease compared to baseline.

CONCLUSIONS

Low TABF occurred without significant changes in the measurements obtained from classic haemodynamic monitoring methods during OPCAB surgery. This finding could be of vital importance in helping improve the monitoring and consequently the management of patients undergoing OPCAB surgery.

Determinants of Candidemia and Candidemia-Related Death in Cardiothoracic ICU Patients

STUDY OBJECTIVES

To develop and prospectively validate models of independent predictors of candidemia and candidemia-related death in cardiothoracic ICU (CICU) patients.

DESIGN

(1) An initial, prospective, one-center, case-control, independent predictor-model determining study; and (2) a prospective, two-center, model-validation study.

SETTING

The initial study was performed at the 14-bed CICU of the Onassis Cardiac Surgery Center, Athens, Greece; the model-validation study was performed at the Onassis Cardiac Surgery Center CICU and the 12-bed CICU of Henry Dunant General Hospital, Athens, Greece.

PATIENTS

In the initial study, 4,312 patients admitted to the Onassis Center CICU between March 1997 and October 1999 were considered for enrollment; 30 candidemic and 120 control patients (case/control ratio, 1/4) matched according to potential confounders were ultimately enrolled. In the model-validation study, 2,087 patients admitted to the Onassis and Henry Dunant CICUs between November 1999 and May 2002 were prospectively enrolled.

MEASUREMENTS AND RESULTS

Models of predictors of candidemia and associated death were constructed with stepwise logistic regression and subsequently validated. Independent candidemia predictors were ongoing invasive mechanical ventilation (IMV) > OR =10 days, hospital-acquired bacterial infection and/or bacteremia, cardiopulmonary bypass duration > 120 min, and diabetes mellitus. Model performance was as follows: sensitivity, 53.3%/57.9%; specificity, 100%/100%; positive predictive value (PPV), 100%/100%; negative predictive value (NPV), 88.9%/99.6%; and accuracy, 90.1%/99.6% (initial/model-validation study values, respectively). IMV > or =10 days and hospital-acquired bacterial infection/bacteremia were the two strongest candidemia predictors. APACHE (acute physiology and chronic health evaluation) II score > or =30 at candidemia onset independently predicted candidemia-related death with 80.0%/85.7% sensitivity, 80%/75% specificity, 66.7%/66.7% PPV, 88.9%/88.9% NPV, and 80.0%/78.9% accuracy (initial/model-validation study values, respectively).

CONCLUSIONS

We provided a set of easily determinable independent predictors of the occurrence of candidemia in CICU patients. Our results provide a rationale for implementing preventive measures in the form of independent predictor control, and initiating antifungal prophylaxis in high-risk CICU patients.

Simvastatin attenuates leucocyte-endothelial interactions after coronary revascularisation with cardiopulmonary bypass

OBJECTIVE

To investigate the effects of preoperative simvastatin treatment on leucocyte-endothelial interactions following coronary artery bypass surgery with cardiopulmonary bypass.

DESIGN

Double blind crossover study. Experiments on polymorphonuclear cells (neutrophils) were done at the end of cardiopulmonary bypass and one hour postoperatively. Endothelial P-selectin expression and neutrophil/endothelial adhesion were evaluated under either normoxic or hypoxic conditions.

SETTING

University hospital (tertiary referral centre).

PATIENTS

Three groups of patients undergoing coronary bypass surgery: 20 patients taking simvastatin for cholesterol control, 16 patients not responsive to simvastatin, and 20 controls.

MAIN OUTCOME MEASURES

Expression of neutrophil CD11b and endothelial P-selectin; adhesion of neutrophils to endothelium.

RESULTS

Cardiopulmonary bypass resulted in a significant increase in neutrophil CD11b expression in all groups. Similarly, the exposure of saphenous vein to hypoxia/reoxygenation induced an augmentation of endothelial P-selectin. However, both neutrophil CD11b expression and endothelial P-selectin exocytosis were less in the simvastatin groups than in the controls. Cardiopulmonary bypass and controlled hypoxia/reoxygenation stimulated neutrophil/endothelial adhesion, but the number of adhering cells was less in the simvastatin groups than in the controls, irrespective of the cholesterol concentration. Treatment of endothelial cells with L-NAME completely reversed the effects of simvastatin.

CONCLUSIONS

Pretreatment with simvastatin reduces neutrophil adhesion to the venous endothelium in patients undergoing coronary surgery, irrespective of its efficacy at lowering cholesterol concentration.

Inflammatory response to cardiopulmonary bypass

Inflammation in cardiac surgical patients is produced by complex humoral and cellular interactions with numerous pathways including activation, generation, or expression of thrombin, complement, cytokines, neutrophils, adhesion molecules, mast cells, and multiple inflammatory mediators. Because of the redundancy of the inflammatory cascades, profound amplification occurs to produce multiorgan system dysfunction that can manifest as coagulopathy, respiratory failure, myocardial dysfunction, renal insufficiency, and neurocognitive defects. Coagulation and inflammation are also closely linked through networks of both humoral and cellular components including proteases of the clotting and fibrinolytic cascades, including tissue factor. Vascular endothelial cells also mediate inflammation and the cross talk between coagulation and inflammation. Novel antiinflammatory agents inhibit these processes by several mechanisms such as preventing proteolysis of the protease-activated receptor (aprotinin), inhibiting complement-mediated injury (pexelizumab), or inhibiting contact activation (kallikrein inhibitors). Surgery alone also activates specific hemostatic responses, activation of immune mechanisms, and inflammatory response mediated by the release of various cytokines and chemokines. Novel agents are under investigation to further improve outcomes in cardiac surgical patients.