Evaluation of myocardial metabolism with microdialysis during bypass surgery with cold blood- or Calafiore cardioplegia

European Journal of Cardio-thoracic Surgery 30 (2006) 597—603 www.elsevier.com/locate/ejcts Evaluation of myocardial metabolism with microdialysis during bypass surgery with cold blood- or Calafiore cardioplegia Jochen Pöling a,d,*, Wolfgang Rees a,d, Vittorio Mantovani e, Stephan Klaus c, Ludger Bahlmann c, Virgilius Ziaukas a, Norbert Hübner b, Henning Warnecke a,d Department of Cardiac Surgery, Schüchtermann-Klinik Bad Rothenfelde, Ulmenallee 11, 49214 Bad Rothenfelde, Germany b Department of Anesthesiology, Schüchtermann-Klinik Bad Rothenfelde, Germany c Department of Anesthesiology, Medical University of Lübeck, Germany d Institut für klinische und molekulare Herz-Kreislaufforschung der Universität Witten-Herdecke, Dortmund, Germany e Department of Cardiac Surgery, University of Insubria-Varese, Germany Received 25 December 2005; received in revised form 7 June 2006; accepted 26 June 2006; Available online 8 August 2006 Abstract Background: For the first time, microdialysis was used to investigate in vivo and online the myocardial metabolism during and after cardiac surgery in patients treated with two different methods of myocardial protection. Methods: Thirty patients underwent standard CABG with one of two different methods of myocardial protection. The patients were randomised to receive either cold blood (COLD group) or warm modified Calafiore cardioplegia (WARM group). Microdialysis probes were implanted into the myocardium of left ventricular apical region of the heart. Cardioplegia was given antegrade only. Microdialysis measurements were performed at time intervals before, during and 24 h after cardiopulmonary bypass and analysed for glucose, lactate, pyruvate and glycerol. Results: Myocardial lactate concentrations were significantly higher in the WARM group compared with that of the COLD group, while serum lactate was comparable. Glycerol was significantly higher at the end of the clamping time in the WARM group. At the same time the glucose—lactate ratio as a marker of nutritional disorder had significantly lower levels in the WARM group. The cumulative CK-MB release over 24 h was significantly higher in those hearts protected with warm blood. Conclusions: The oxidative stress measured was significantly higher in patients undergoing CABG using modified Calafiore cardioplegia, whereas the cold cardioplegia minimised the effects of aortic clamping. The results indicate that cold cardioplegia offers superior protection of the heart, in terms of more rapid normalisation of myocardial metabolism. In elective myocardial revascularisation, intermittent antegrade warm blood cardioplegia is a comparable safe method of myocardial protection. However, in patients referring to a long clamping time, advantages of cold cardioplegia for myocardial revascularisation may be magnified. # 2006 Elsevier B.V. All rights reserved. Keywords: Cardiovascular surgery; Cardioplegia; Energy metabolism; Glycolysis; Ischaemia 1. Introduction Despite of improvements in surgical and myocardial protection techniques, postoperative ventricular dysfunction after cardiac surgery is clinically not uncommon and well observed experimentally [1,2]. Insufficient cardioplegia results in anaerobic metabolism during cardiac arrest with subsequent heart failure. However, a more detailed knowledge is required about myocardial regulation processes in concentration of nutrients and information about interstitial fluid shifts due to perfusion of cardioplegic solutions. Numerous investigations on the effect of different cardioplegic solutions were published, but up to now, monitoring of * Corresponding author. Address: Department of Cardiac Surgery, Schüchtermann-Klinik Bad Rothenfelde, Ulmenallee 11, 49214 Bad Rothenfelde, Germany. Tel.: +49 5424 64130070. E-mail address: (J. Pöling). 1010-7940/$ — see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.ejcts.2006.06.031 the postischaemic human myocardium is focussed only on global myocardial function, systemic haemodynamics and on indirect criteria to assess oxidative stress in the clinical setting [3,4]. Reason for this lack of information was the inability to monitor in vivo cell metabolism in the human myocardium. Currently used animal models and histologic examinations only reflect partial complexity of myocardial metabolism and are not able to describe dynamics of this process [5]. Therefore, results of these investigations can only be considered as superficial and leave essential questions unanswered. The microdialysis technique is a new and feasible technique for online and in vivo measuring of drug concentrations, markers of cell injury and metabolites in the interstitial fluid of nearly every organ and also in the beating heart. Interstitial fluid component changes reflect intracellular disorder. Habicht et al. [6] introduced this technique to human cardiac surgery, inserting a microdialysis a 598 J. Pöling et al. / European Journal of Cardio-thoracic Surgery 30 (2006) 597—603 2. Material and methods Thirty patients gave their informed consent to participate in the study, which was approved by the local ethics committee. They were randomly allocated to one of two groups: group 1 (COLD, n = 15) received intermittent antegrade cold cardioplegia and group 2 (WARM, n = 15) received intermittent antegrade warm blood cardioplegia. 2.1. Anaesthesia Anaesthesia was induced with etomidate (0.3— 0.5 mg g 1) and sufentanyl (0.5—1 g kg 1) and maintained with continuous infusions of propofol (5—8 mg kg 1 h 1) and sufentanyl (0.5—1 g kg 1 h 1). Muscle relaxation was achieved by pancuroniumbromide (0.1 mg kg 1). All patients were equipped with a radial arterial line, a central venous catheter and a standard pulmonary artery catheter. Fluid management was adjusted to achieve and maintain a central venous pressure (CVP) between 8 and 12 mmHg. Volume replacement was performed with cristalloids only. 2.2. Operative technique After median sternotomy and pericardotomy, the myocardial microdialysis probe was inserted into the anterior wall of the left ventricle, followed by the preparation of the LIMA. Routine cardiopulmonary bypass was performed in normothermia. Standard graft anastomosing technique was used in all cases. The volume and temperature of the cardioplegia solution and the rate of infusion were recorded. Cardiopulmonary bypass time, cross-clamp time, need for inotropic support, number of trials necessary to separate the patient from the extracorporeal circuit, and the number of electric shocks required to achieve ventricular defibrillation were registered. Epinephrine was infused, if the heart was clinically hypocontractile, if cardiac index was below 2.0 l m2 despite of adequate filling or if the systolic blood pressures was lower than 60 mmHg despite an adequate preload. 2.3. Microdialysis procedure Microdialysis imitates natural blood capillary function. Before preparation of the LIMA, a thin (double lumen (...truncated)