Risk Factors for Myocardial Injury during Off-Pump Coronary Artery Bypass Grafting

Protective effect of dexmedetomidine in coronary artery bypass grafting surgery

The aim of this study was to observe the impact of dexmedetomidine on postoperative myocardial injury in patients undergoing off-pump coronary artery bypass (OPCAB) grafting. One hundred and sixty-two patients who were undergoing OPCAB surgery were randomly divided into control and dexmedetomidine groups (groups C and Dex, respectively). Following the first vascular anastomosis grafting, the patients in group Dex received a continuous intravenous infusion of 0.2–0.5 μg/kg/h dexmedetomidine, until they were transferred to the Cardiac Surgery intensive care unit (ICU) for 12 h. Patients in group C received physiological saline intraoperatively and an intravenous infusion of 2–4 mg/kg/h isopropylphenol for postoperative sedation. Invasive arterial pressure and heart rate were continuously monitored for 5 min subsequent to entry into the operating theatre (T0), immediately following surgery (T1), 12 h post-surgery (T2), 24 h post-surgery(T3), 48 h post-surgery(T4) and 72 h post-surgery (T5). Blood samples were taken to determine the plasma levels of cardiac troponin I (cTnI) and creatine kinase-MB (CK-MB) at each time point. At 72 h post-surgery, a dynamic electrocardiogram was monitored. The blood pressure, heart rate, levels of cTnI, CK-MB, norepinephrine and cortisol, and postoperative arrhythmic events in the patients in group Dex all decreased compared with those in group C. The duration of mechanical ventilation and ICU residence time were also shorter than those in the control group (P<0.05). Dexmedetomidine reduced post-surgical myocardial injury in patients who had undergone OPCAB surgery.

Cardiac surgery patients present considerable variation in pre-operative hemodynamic variables

BACKGROUND

It is essential to control hemodynamics in cardiac surgery. Patients are often monitored extensively in order to optimize hemodynamic performance. However, pre-operative values are normally unknown. Furthermore, hemodynamic goals may seem arbitrary and the lack of an evidence-based consensus may lead to both under- and over-treatment. The aim of this study was to evaluate the variables most commonly used for hemodynamic guidance in the post-operative period.

METHODS

Ten patients scheduled for elective cardiac surgery were followed with invasive hemodynamic monitoring the night before surgery. All data were recorded automatically and electronically.

RESULTS

We found considerable inter-patient differences and intra-patient variation. The greatest intra-patient variation was found in the cardiac index (CI), ranging from 1.9 to 5.3 l/min/m(2). Four patients had periodic CI <2.4 l/min/m(2). Eight patients showed SpO2 values < or =92, four of them in more than 15% of the observations. Six patients had an SvO2 <70% in more than 40% of the observations and two an SvO2 < 64% in more than 20% of the observations.

CONCLUSIONS

This study is unique because hemodynamic reference data in cardiac surgery patients have not been published previously. The intra-patient variations were unexpectedly high in most hemodynamic variables and demonstrate the difficulties of using hemodynamic parameters as a guidance for treatment and indicate that goal-oriented therapy using currently accepted values may result in over-treatment in some patients.