Comparative Study of Cardiac Output Measurement by Regional Impedance Cardiography and Thermodilution Method in Patients Undergoing off Pump Coronary Artery Bypass Graft Surgery

Background:An ideal CO monitor should be noninvasive, cost effective, reproducible, reliable during various physiological states. Limited literature is available regarding the noninvasive CO monitoring in open chest surgeries. Aim: The aim of this study was to compare the CO measurement by Regional Impedance Cardiography (RIC) and Thermodilution (TD) method in patients undergoing off pump coronary artery bypass graft surgery (OPCAB). Settings and Design: We conducted a prospective observational comparative study of CO measurement by the noninvasive RIC method using the NICaSHemodynamicNavigator systemand the gold standardTDmethod using pulmonary artery catheterin patients undergoingOPCAB.Atotal of 150 data pair from the two CO monitoring techniques were taken from 15 patients between 40-70 years at various predefined time intervals of the surgery. Patients and Methods: We have tried to find out the accuracy, precision and cost effectiveness of the newer RIC technique. Mean CO, bias and precision were compared for each pair i.e.TD-CO and RIC-CO as recommended by Bland and Altman.The Sensitivity and specificity of cutoff value to predict change in TD-CO was used to create a Receiver operating characteristic or ROC curve. Results: Mean TD-CO values were around 4.52 ± 1.09 L/min, while mean RIC- CO values were around 4.77± 1.84 L/min. The difference in CO change was found to be statistically not significant (p value 0.667). The bias was small (-0.25). The Bland Altman plot revealed a mean difference of -0.25 litres.The RIC method had a sensitivity of 55.56 % and specificity of 33.33 % in predicting 15% change in CO of TD method and the total diagnostic accuracy was 46.67%. Conclusion: A fair correlation was found between the two techniques. The RIC method may be considered as a promising noninvasive, potentially low cost alternative to the TD technique of hemodynamic measurement.

Comparison of transthoracic electrical bioimpedance cardiac output measurement with thermodilution method in post coronary artery bypass graft patients.

Transthoracic electrical bioimpedance (TEB) has been proposed as a non-invasive, continuous, and cost-effective method of cardiac output (CO) measurement. In this prospective, non-randomized, clinical study, we measured CO with NICOMON (Larsen and Toubro Ltd., Mysore, India) and compared it with thermodilution (TD) method in patients after off-pump coronary artery bypass (OPCAB) graft surgery. We also evaluated the effect of ventilation (mechanical and spontaneous) on the measurement of CO by the two methods. Forty-six post-OPCAB patients were studied at five predefined time points during controlled ventilation and at five time points when breathing spontaneously. A total of 230 data pairs of CO were obtained. During controlled ventilation, TD CO values ranged from 2.29 to 6.74 L/min (mean 4.45 ± 0.85 L/min), while TEB CO values ranged from 1.70 to 6.90 L/min (mean 4.43 ± 0.94 L/min). The average correlation (r) was 0.548 (P = 0.0002), accompanied by a bias of 0.015 L/min and precision of 0.859 L/min. In spontaneously breathing patients, TD CO values ranged from 2.66 to 6.92 L/min (mean 4.66 ± 0.76 L/min), while TEB CO values ranged from 3.08 to 6.90 L/min (mean 4.72 ± 0.82 L/min). Their average correlation was relatively poor (r = 0.469, P= 0.002), accompanied by a bias of −0.059 L/min and precision of 0.818 L/min. The overall percent errors between TD CO and TEB CO were 19.3% (during controlled ventilation) and 17.4% (during spontaneous breathing), respectively. To conclude, a fair correlation was found between TD CO and TEB CO measurements among post-OPCAB patients during controlled ventilation. However, the correlation was weak in spontaneously breathing patients.

Effect of prophylactic continuous infusion of isosorbide dinitrate on myocardial protection and hemodynamics in patients undergoing off-pump coronary bypass surgery

BACKGROUND: Multi-vessel off-pump coronary bypass surgery (OPCAB) imposes cumulative myocardial ischemia/reperfusion injury, which may be attenuated by continuous infusion of nitrate. However, nitrate infusion and consequent decrease in preload may be hazardous during heart displacement which causes restrictive filling of the ventricles. Therefore, we evaluated the effect of nitrate infusion on myocardial protection and hemodynamics in patients undergoing OPCAB, in a prospective, randomized and controlled trial. METHODS: Fifty patients with stable angina and left ventricular ejection fraction >40% undergoing elective, isolated, multivessel OPCAB were enrolled. Patients were randomized equally to either continuous infusion of isosorbide dinitrate 0.5microg/kg/min or same amount of normal saline during the surgery. Operative data including hemodynamic variables, intraoperative ST segment changes and postoperative cardiac enzyme release (creatine kinase-MB, troponin T) were compared. RESULTS: Patients characteristic and operative data including ST segment changes and use of vasopressors were similar between the groups except the total amount of infused crystalloid during the surgery which was significantly higher in the nitrate group. Postoperative variables including cardiac enzyme release were also similar between the groups. CONCLUSIONS: Prophylactic continuous infusion of nitrate during OPCAB exerted no additional benefit in terms of myocardial protection. It also, was not associated with accentuated decrease in cardiac output during heart displacement, and the decrease in preload seems to have been nullified by modest increase in fluid therapy.

Effect of Gender on Outcomes of Off-pump Coronary Artery Bypass Surgery / 대한마취과학회지

BACKGROUND: Although female gender is associated with higher prevalence of perioperative morbidity and mortality than male gender in conventional coronary artery bypass surgery (CABG) using cardiopulmonary bypass, the impact of gender as an independent risk factor for morbidity and mortality following off-pump CABG (OPCAB) is controversial. Therefore, we prospectively investigated the impact of gender on intraoperative variables and postoperative outcome and complications in OPCAB. METHODS: One hundred patients (69 males and 31 females) undergoing OPCAB by a single cardiac surgeon during 5 months period were prospectively enrolled. Preoperative patient's characteristics, intraoperative hemodynamics and medications and postoperative outcome and complications were recorded during hospital stay. RESULTS: There were no significant differences in preoperative characteristics including age, NYHA class and incidence of concomitant diseases between the male and female groups, except body surface area which was less in the female group. There were no significant differences in intraoperative hemodynamics and use of cardiotonic drugs between the groups. Frequency and amount of blood transfusion were greater, and length of ventilatory care and stay in intensive care unit were longer in female group. Other postoperative outcomes were similar between the groups. CONCLUSIONS: Gender did not significantly affect postoperative outcome, except use of blood products, length of ventilatory care and stay in intensive care unit in OPCAB. These results may be attributable to comparable preoperative patient's characteristics between the groups.

The Use of Saline Bag for Cardiac Displacement Facilitates the Transgastric Transesophageal Echocardiographic View during Off-pump Coronary Artery Bypass Graft Surgery : A case report / 대한마취과학회지

During off-pump coronary artery bypass graft surgery (OPCAB), vigorous displacement and compression of the heart producing significant hemodynamic change are essential for optimal exposure of graft anastomoses. Intraoperative transesophageal echocardiography (TEE) is useful in determining hemodynamic compromise and prompting medical and mechanical support. However, in addition to the loss of contact between the heart and diaphragm during the displacement, swabs or snears underneath the heart interrupt the TEE signal transmission, resulting in a compromised transgastric (TG) TEE view. Therefore, TEE monitoring during OPCAB is usually limited to the mid-esophageal view. The authors placed a saline bag (a surgical glove filled with saline) underneath the heart to facilitate this anterior displacement of the heart, as well as avoid the signal interruption of the TG echocardiographic window. As a result, the optimal heart position with the minimal changes in LV regional wall motion, LV function and mitral regurgitation were found using the TG and other TEE views. The series of velocity-time integral of aortic valvular flow (VTI-Ao) in TG long axis view, in addition to SvO2, were then monitored as a surrogate marker of the cardiac output during a graft construction of the left circumflex artery. It was concluded that the use of a saline bag may be useful in avoiding compromise of the TG TEE view and determine the hemodynamic change using VTI-Ao during cardiac displacement for OPCAB.

The Effect of Diabetes Mellitus on Vasoconstrictor Requirement and Hemodynamic Parameters in Patients Undergoing Off Pump Coronary Artery Bypass Graft Surgery

BACKGROUND: Autonomic neuropathy is frequently developed in patients with diabetets mellitus (DM) and is associated with increased perioperative hemodynamic instability. This study investigated the effect of DM on vasoconstrictor requirement and hemodynamic parameters in patients undergoing off pump coronary artery bypass graft surgery (OPCAB). METHODS: Seventy four patients undergoing OPCAB were divided into two groups; patients without DM (control, n = 51) and patients with DM (n = 23). Hemodynamic parameters were recorded at 10 min after induction of anesthesia (T1), at 10 min after stabilizer application for anastomosis of the left anterior descending coronary artery (T2), the obtuse marginalis branch (T3) and the right coronary artery (T4) and at 10 min after sternum closure (T5). The amount of norepinephrine requirement during the period of induction of anesthesia and grafting was also recorded. RESULTS: Pulmonary capillary wedge pressure (PCWP) and mean pulmonary arterial pressure at T3, PCWP and central venous pressure at T4 were significantly higher in the DH group. Mixed venous oxygen saturation at T2 and T4 and cardiac output at T3 were also significantly lower in the DH group. Significantly greater amount of norepinephrine was infused during the induction of anesthesia in the DH group. CONCLUSIONS: Patients with coronary artery occlusive disease and concomitant DM required significantly greater amount of vasoconstrictor during the induction of anesthesia to maintain stable mean arterial pressure. In addition, more pronounced hemodynamic instability was observed during the period of grafing in these patients undergoing OPCAB.

Effect of Preoperative Aspirin Use on Postoperative Bleeding and Thromboelastography in Off-Pump Coronary Artery Bypass Operations / 대한마취과학회지

BACKGROUND: Aspirin has been shown to effectively increase survival and reduce morbidity in patients with ischemic heart disease. Continued aspirin use during the preoperative period could increase the postoperative blood loss in patients who have on-pump coronary artery bypass grafting. This study aimed to determine the effect of continued aspirin use before off-pump CABG on intraoperative and postoperative bleeding and coagulation profile in thromboelastography. METHODS: In 43 patients undergoing OPCAB, they were assigned aspirin user (n = 22), who received aspirin until the day of operation or nonaspirin user (n = 21), who discontinued aspirin before 7 days before the surgery. Intraoperative and postoperative bleeding and transfusion requirement were measured. TEG was performed and R, K, alpha angle, maximum amplitude and TEG index was measured at preinduction and at 24 hours after surgery. RESULTS: There were no differences in patient characteristics between aspirin users and nonaspirin users. We found no significant difference between postoperative bleeding and blood product requirements for the two groups. Similarly, we found no significant difference in the coagulation profiles. CONCLUSIONS: The use of aspirin continued preoperatively does not increase intraoperative and postoperative blood loss, and blood product requirement and influence on coagulation profile.

The Effect of Preoperative Propranolol Medication on Dobutamine Infusion in Off-pump Coronary Artery Bypass Graft Surgery / 대한마취과학회지

BACKGROUND: Preoperative beta-adrenergic receptor (beta-AR) antagonist administration is known to improve ventricular function by decreasing the myocardial oxygen demand in coronary artery obstructive disease (CAOD). This study evaluated the effect of preoperative propranolol on response to beta-AR agonist, dobutamine in patients undergoing off-pump coronary artery bypass graft surgery (CABG). METHODS: Twenty six patients undergoing off-pump CABG, and treated with propranolol preoperatively, were enrolled in this study. After anesthesia, the infusion of dobutamine was started at 2microgram/kg/min (D2) for 5 min and then increased to 4microgram/kg/min (D4) and 8microgram/kg/min (D8) in succession. The same protocol was performed twice before and after coronary artery anastomosis (pre-graft and post-graft). Hemodynamic variables were measured just before the infusion of dobutamine (D0, baseline) and after each dobutamine infusion at D2, D4 and D8. RESULTS: No significant change was observed in the cardiac index (CI) during the pre-graft period, but CI increased significantly at D4 and D8 compared with D0 during the post-graft period. Mean arterial pressure (MAP), mean pulmonary artery pressure (MPAP) and systemic vascular resistance index (SVRI) increased at D2, D4 and D8 and heart rate (HR) decreased at D2 and D4 during the pre-graft period. MAP and SVRI did not change and HR and CI increased at D4 and D8 during the post-graft period. The % change of CI from D0 significantly increased at D4 and D8 during the post-graft period than during the pre-graft period but not at D2. MAP, SVRI and MPAP after dobutamine infusion significantly increased during the pre-graft period than during the post-graft period. HR showed a reversed trend. CONCLUSIONS: Dobutamine infusion did not exert any known positive inotropic effect, besides increased MAP, MPAP and SVRI, in patients treated with propranolol preoperatively undergoing off-pump CABG during the pre-graft period. Meanwhile, dobutamine exerted slight inotropic effects during the post-graft period. Cautious use of dobutamine during the pre-graft period is needed in patients treated with propranolol preoperatively.

The Changes of Right Ventricular Function and Hemodynamic Parameters During Coronary Anastomosis in Beating Heart Surgery / 대한마취과학회지

BACKGROUND: Hemodynamic derangement during the displacement of the beating heart in off-pump coronary artery bypass graft surgery (OPCAB) might be related with right ventricular (RV) dysfunction. This study evaluated the influence of displacing and stabilizing the heart, for the anastomosis of coronary arteries, on hemodynamic alterations and RV function in patients undergoing OPCAB. METHODS: Twenty patients with triple vessel coronary artery disease underwent OPCAB using single pericardial sutures: a tissue stabilizer was included. The hemodynamic variables and right ventricular ejection fraction (RVEF) were obtained using a right-heart ejection fraction thermodilution pulmonary artery catheter after the induction of anesthesia, before and after anastomosis of each coronary artery and after sternal closure. RESULTS: No significant hemodynamic changes were observed during the displacement of the heart or the placement of a stabilizer on all of the coronary arteries, except the obtuse marginal artery (OM) before anastomosis. RVEF, left ventricular stroke work index (LVSWI), stroke volume index and cardiac index (CI) decreased and mean pulmonary artery pressure increased significantly whist positioning the graft to the OM. Right ventricular volumes were not significantly changed, although central venous pressure and pulmonary capillary wedge pressure increased. Changing CI had a close relationship with LVSWI (r2 = 0.537, P <0.05) but not with RVEF (r2 = 0.118). These hemodynamic compromises recovered to baseline values after sternal closure. CONCLUSIONS: The displacement of the beating heart for positioning during anastomosis of the graft to the OM caused significant hemodynamic instability and LV functional changes in addition to RV functional changes seemed to be responsible for hemodynamic derangements.

Anesthetic Management for Off-Pump Coronary Artery Bypass Graft Surgery / 대한마취과학회지

Off-pump coronary artery bypass graft surgery (OPCAB) may be of benefit overall for the patient and surgical techniques for OPCAB have been developed markedly. The development of surgical techniques without severe hemodynamic instability allows surgeons to access to all coronary arteries. Hemodynamic instability due to the displacement and restraining of the heart and transient ischemia during anastomoses are major problems associated with OPCAB. The maintenance of stable hamodynamic and minimization of cardiac dysfunction during anastomosis should be stressed in the anesthesia for OPCAB. The baseline anesthetic methods and monitoring for OPCAB are the same as for conventional coronary artery bypass graft surgery (CABG). The temperature management is a significant problem and appropriate provision is needed for defibrillation and pacing during anastomosis because rhythm problems are not uncommon. Prevention and treatment of hypotension, low cardiac output, and dysrhythmia is a major focus of anesthetic management. Volume loading and Trendelenberg position is helpful maintaining cardiac output and perfusion pressure. If hemodynamic deterioration occurs, quickly progress to potent vasopressors/ inotropic agents. Treatment of myocardial ischemia must be guided by the patient's overall hemodynamic status. Therapies to consider include titrated beta-adrenergic blockers, increasing blood pressure to improve collateral flow, treating the spasm of native coronaries or arterial conduits, reversing Trendelenberg to reduce left ventricular filling and wall stress and shunting. Close observation for surgical field and open communication with surgeon is essential to predict the patients most likely to need above modalities and bearing similarities with anesthesia for CABG in mind will help the anesthesiologist to be more comfortable with anesthesia for OPCAB.