Intraoperative regional myocardial acidosis predicts the need for inotropic support in cardiac surgery

Calcium administration In patients undergoing CardiAc suRgery under cardiopulmonary bypasS (ICARUS trial): Rationale and design of a randomized controlled trial

Introduction

Weaning from cardiopulmonary bypass (CPB) is a critical step of any cardiac surgical procedure and often requires pharmacologic intervention. Calcium ions are pivotal elements for the excitation-contraction coupling process of cardiac myocytes. Thus, calcium administration might be helpful during weaning from CPB.

Methods

We describe a multicenter, placebo-controlled, double blind randomized clinical trial to assess the effect of calcium chloride on the need for inotropic support among adult patients during weaning from CPB. The experimental group (409 patients) will receive 15 mg/kg of calcium chloride. The control group (409 patients) will receive an equivalent volume of 0.9% sodium chloride. Both drugs will be administered intravenously as a bolus at the beginning of weaning from CPB.

Results

The primary outcome will be the need for inotropic support between termination of CPB and completion of surgery. Secondary outcomes will be: duration of inotropic support, vasoactive-inotropic score 30 min after transfer to intensive care unit and on postoperative day 1, plasma alpha-amylase on postoperative day 1, plasma Ca²⁺ concentration immediately before and 10–15 min after calcium chloride administration, non-fatal myocardial infarction, blood loss on postoperative day 1, need for transfusion of red blood cells, signs of myocardial ischemia on electrocardiogram after arrival to intensive care unit, all-cause mortality at 30 days or during hospital stay if this is longer than 30 days.

Discussion

This trial is designed to assess whether intravenous calcium chloride administration could reduce the need for inotropic support after cardiopulmonary bypass weaning among adults undergoing cardiac surgery.

Coronary Sinus Lactate as Marker of Myocardial Ischemia in Cardiac Surgery: Correlation with Morbidity and Mortality after Cardiac Surgery / Lactatul din sinusul coronarian - marker al ischemiei miocardice în chirurgia cardiacă: corelaţii cu morbiditatea şi mortalitatea postoperatorie

Introduction. Perioperative myocardial injuries are one of the most frequent causes of morbidity and mortality after cardiac surgery, the most common etiology being the poor myocardial protection during aortic crossclamp. During aortic crossclamp progressive accumulation of lactate and intracellular acidosis are well-known phenomena, and are associated with alteration of myocardial contractile function. Our objective was to study the coronary sinus lactate levels as a predictor of postoperative hemodynamic outcome in open-heart surgical patients.

Material and methods. We performed a prospective clinical trial, including 142 adult patients with elective cardiac surgery. Anterograde cardioplegia was administered in 82 patients, retrograde cardioplegia in 60 (in 30 patients it was administrated intermittently and in 30 continuously). Blood was collected simultaneously from the aortic cardioplegic line (inflow) and from coronary sinus or the aortic root (outflow) before aortic crossclamp, after crossclamp at every 10 minutes and after crossclamp removal at 0 and 10 minutes. All patients were operated on cardiopulmonary bypass with cardiac arrest, using warm-blood cardioplegia for cardioprotection.

Results. Lactate levels showed increasing values during aortic crossclamp, and a rapid decline after crossclamp removal. The incidence of low cardiac output was significantly higher in patients with lactate levels that exceeded 4 mmol/L. In patients who died in the postoperative period, lactate level was even higher (5 mmol/L), with only a modest recovery after crossclamp removal.

Conclusion. Monitoring lactate level in coronary sinus blood is a reliable method and has a good prognostic value regarding postoperative morbidity and mortality in open heart surgery

Intraoperative Hemodynamic Instability During and After Separation From Cardiopulmonary Bypass

Every year, more than 1 million patients worldwide undergo cardiac surgery. Because of the aging of the population, cardiac surgery will increasingly be offered to patients at a higher risk of complications. The consequence is a reduced physiological reserve and hence an increased risk of mortality. These issues will have a significant impact on future health care costs because the population undergoing cardiac surgery will be older and more likely to develop postoperative complications. One of the most dreaded complications in cardiac surgery is difficult separation from cardiopulmonary bypass (CPB). When separation from CPB is associated with right-ventricular failure, the mortality rate will range from 44% to 86%. Therefore, the diagnosis and the preoperative prediction of difficult separation from CPB will be crucial to improve the selection and care of patients and to prevent complications for this high-risk patient population.

Intraoperative myocardial acidosis as a risk for hospital readmission after cardiac surgery

BACKGROUND

This study elucidates the relationship between intraoperative myocardial acidosis/ischemia and the risk of unplanned hospital readmissions within 30 days and 6 months after cardiac surgery.

METHODS

Myocardial tissue pH (corrected to 37 degrees C: pH(37C)) was monitored in 221 patients during cardiac surgery. Regional myocardial acidosis was defined in terms of specific pH thresholds.

RESULTS

Fourteen percent and 27% of the patients were readmitted within 30 days and 6 months postoperatively, respectively. The mean number of readmissions was 1.67 +/- 1.24; pH(37C) <6.85 at the end of cardiopulmonary bypass (CPB) was identified as the threshold most significantly associated with readmission. This threshold was associated with a 6-fold increased risk of readmission within 30 days and a 5-fold increased risk within 6 months.

CONCLUSIONS

Persistent regional myocardial acidosis after weaning from CPB independently determines unplanned readmission rates up to 6 months postoperatively. This study underscores the importance of avoiding myocardial tissue acidosis during cardiac surgery.

In vivo detection of myocardial ischemia in pigs using visible light spectroscopy

BACKGROUND

Monitoring tissue oxygenation (StO(2)) by visible light spectroscopy (VLS) can identify tissue ischemia, but its feasibility for detecting myocardial ischemia is not known. We hypothesized that VLS can reliably detect changes in myocardial StO(2) in pigs subjected to acute regional or global myocardial ischemia.

METHODS

In 11 pigs, regional myocardial ischemia was created by ligation of left anterior descending artery (LAD). Myocardial StO(2) was determined from the ischemic and nonischemic left ventricular (LV) regions and compared to coronary venous saturations. Myocardial function was assessed by echocardiography. In six pigs, LV-StO(2) was measured during cardiopulmonary bypass (CPB), after cardioplegic cardiac arrest, and during CPB with inadequate myocardial protection. Additionally, right ventricular (RV)- and LV-StO(2) were assessed during acute RV pressure overload from pulmonary artery (PA) banding.

RESULTS

StO(2) baselines in pigs undergoing LAD occlusion were similar in the ischemic and nonischemic myocardium (70% +/- 8% vs 74% +/- 5%). After LAD ligation, StO(2) rapidly declined (30 s: 59% +/- 8%; 1 min:50 +/- 9; 5 min:42% +/- 4%; P < 0.05) in the ischemic myocardium. Decreases in StO(2) correlated with coronary venous saturations (r = 0.88) and were associated with myocardial dysfunction. In pigs undergoing CPB, LV-StO(2) remained unchanged with initiation of CPB or after cardioplegic cardiac arrest, but LV ischemia was detected by StO(2) after aortic cross-clamp without adequate myocardial protection. Similarly, PA banding resulted in a profound decrease of RV-StO(2) from 69% +/- 6% to 52% +/- 7% (P < 0.05) with recovery after PA release.

CONCLUSIONS

VLS is a reliable method of detecting alterations in myocardial StO(2) and can be a useful monitor for rapid identification of myocardial ischemia.

Image-guided quantification of cardioplegia delivery during cardiac surgery

BACKGROUND

Homogenous distribution of cardioplegia delivered to the myocardium has been identified as an important predictor of post-cardiopulmonary bypass ventricular recovery and function. Presently, a method to determine adequate distribution of cardioplegia in patients during cardiac surgery does not exist. The goal of this study was to evaluate the feasibility of quantifying cardioplegia delivery using a novel, noninvasive optical method. Such a system would permit instantaneous imaging of jeopardized myocardium and allow immediate, intraoperative corrective measures.

METHODS

We have previously developed a portable, intraoperative near-infrared (NIR) fluorescence imaging system for use in large animal cardiac surgery that simultaneously displays color video and NIR fluorescent images of the surgical field. By introducing exogenous, NIR fluorophores, specific cardiac functions can be visualized in real-time.

RESULTS

In a porcine cardiopulmonary bypass model, we demonstrate that the FDA-approved intravascular fluorophore indocyanine green (ICG) permits real-time assessment of cardioplegia delivery. ICG was injected into an aortic root and/or transatrial coronary sinus catheter during delivery of crystalloid cardioplegia solution. Segmental distribution was immediately noted at the time of injection. In a subset of animals, simulated coronary occlusions resulted in imaging defects consistent with poor cardioplegia delivery and jeopardized myocardium. Videodensitometric analysis was performed on-line to quantify distribution to the right ventricle and left ventricle.

CONCLUSION

We report the development of a novel, noninvasive, intraoperative technique that can easily and safely provide a visual assessment of cardioplegia delivery (antegrade and/or retrograde) and that offers the potential to quantify the relative segmental distribution during cardiac surgical procedures.

Patients with diabetes mellitus undergoing cardiac surgery are at greater risk for developing intraoperative myocardial acidosis

OBJECTIVE

In patients undergoing cardiac surgery, intraoperative myocardial acidosis, which quantifies regional myocardial ischemia, has been shown to increase the risk of adverse postoperative outcomes. In this study, we sought to determine the course of intraoperative myocardial acidosis and its impact on postoperative survival in patients with diabetes mellitus undergoing cardiac surgery.

METHODS

Intraoperative myocardial tissue pH(37C) was continuously measured in the anterior and posterior left ventricular walls in 264 patients undergoing cardiac surgery; 74 (28.0%) of the patients had diabetes (insulin-dependent diabetes: 54%; non-insulin dependent diabetes: 46%). The shortest time required to reach intraoperative myocardial tissue pH < 6.34 during aortic occlusion and > 6.73 during reperfusion were compared in 3 patient groups: insulin-dependent, non-insulin dependent, and nondiabetic. These pH thresholds have been demonstrated to be associated with adverse postoperative long-term survival.

RESULTS

The median times to reach intraoperative myocardial tissue pH(37C) < 6.34 during aortic occlusion were 14, 23, and 36 minutes in the insulin-dependent, non-insulin dependent, and non-diabetic groups, respectively (P = .003). The time taken to reach intraoperative myocardial tissue pH(37C) > 6.73 during reperfusion was similar between the 3 groups. After adjusting for relevant pre- and intraoperative parameters, the risk of developing intraoperative myocardial tissue pH < 6.34 during aortic occlusion was 73% higher in patients with insulin-dependent diabetes mellitus (P = .022) but the same in with patients with non-insulin dependent diabetes mellitus (P = .98) when compared with patients without diabetes. Patients with insulin-dependent diabetes mellitus also had nearly threefold decrease in long-term survival compared with that of patients without diabetes (P = .0007).

CONCLUSIONS

Patients with insulin-dependent diabetes mellitus undergoing cardiac surgery are at a greater risk of developing intraoperative myocardial acidosis/ischemia and of decreased survival postoperatively compared with patients without diabetes.

Coronary bypass grafting using crossclamp fibrillation does not result in reliable reperfusion of the myocardium when the crossclamp is intermittently released: a prospective cohort study

Background

Cross-clamp fibrillation is a well established method of performing coronary grafting, but its clinical effect on the myocardium is unknown. We sought to measure these effects clinically using the Khuri Intramyocardial pH monitor.

Methods

50 episodes of cross-clamping were recorded in 16 patients who underwent CABG with crossclamp-fibrillation. An Intramyocardial pH probe measured the level of acidosis in the anterior and posterior myocardium in real-time. The pH at the start and end of each period of cross-clamping was recorded.

Results

It became very apparent that the pH of some patients recovered quickly while others entirely failed to recover. Thus the patients were split into 2 groups according to whether the pH recovered to above 6.8 after the first crossclamp-release (N = 8 in each group). Initial pH was 7.133 (range 6.974–7.239). After the first period of crossclamping the pH dropped to 6.381 (range 6.034–6.684). The pH in recoverers prior to the second XC application was 6.990(range 6.808–7.222) compared to only 6.455 (range 6.200–6.737) in patient's whose myocardium did not recover (P < 0.0005). This finding was repeated after the second XC release (mean pH 7.005 vs 6.537) and the third (mean pH 6.736 vs 6.376). However prior to separation from bypass the pH was close to the initial pH in both groups (7.062 vs 7.038).

Conclusion

Crossclamp fibrillation does not result in reliable reperfusion of the myocardium between periods of crossclamping.