Influence of temperature on the positive inotropic effect of levosimendan, dobutamine and milrinone.

BACKGROUND AND OBJECTIVE: Patients in cardiac surgery and critically ill patients often demonstrate either hypothermia or fever. In addition, owing to heart failure, they frequently require inotropic support. The relative effectiveness of modern inotropic agents at various temperatures has not yet been evaluated. Therefore, we investigated the influence of levosimendan, dobutamine and milrinone on the contractile response of myocardial trabeculae at various temperatures. METHODS: A total of 120 guinea pig ventricular trabeculae were placed in oxygenated 4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid (HEPES) buffer, stimulated at a frequency of 1.3 Hz and randomly assigned to a temperature of 31 degrees C, 34 degrees C, 37 degrees C or 40 degrees C. Concentrations of all substances were increased stepwise from 10(-9) to 10(-5) mol l(-1) (milrinone up to 10(-4) mol l(-1)). Maximum developed force, time to peak tension, Tsystolic(50%) and Tdiastolic(50%) were continuously recorded. RESULTS: All agents showed a dose-dependent positive inotropic effect (P < 0.0001 for all). Levosimendan acted at every temperature as a positive inotrope (P = 0.0643). Dobutamine-related inotropy showed a clear trend towards temperature dependence, although statistical evaluation did not prove this (P = 0.0624). Milrinone-related inotropy was abolished at 31 degrees C and 34 degrees C, and temperature dependence was significant (P < 0.0001). Hypothermia induced a positive inotropic effect. CONCLUSION: Our results suggest no modulation of levosimendan-induced inotropy under the experimental temperatures tested. This observation is possibly due to its Ca2+-sensitizing mechanism, which might not be influenced by temperature-related changes in intracellular Ca2+ levels. In contrast, the inotropic effect of cyclic AMP-coupled dobutamine and milrinone is suppressed under hypothermia-related interaction with intracellular Ca2+ homeostasis. Hence, levosimendan might prove to be the preferred inotropic drug in hypothermic patients.

Normothermic beating heart surgery with assistance of miniaturized bypass systems: the effects on intraoperative hemodynamics and inflammatory response.

The use of miniaturized cardiopulmonary bypass (CPB) circuits and avoidance of cardioplegic arrest are attempts to reduce the inflammatory response to cardiac surgery. We studied the effects of beating heart surgery (BHS) with assistance of simplified bypass systems (SBS) on global hemodynamics, myocardial function and the inflammatory response to CPB. We hypothesized that the use of SBS was associated with less hemodynamic instability after CPB resulting from attenuation of the inflammatory response when compared with surgery performed with a conventional CPB (cCPB) circuit. Forty-five patients undergoing coronary artery bypass grafting were prospectively studied. Fifteen patients were randomized to the use of a cCPB circuit, cold crystalloid cardioplegia, and moderate hypothermia. Two groups of 15 patients underwent BHS during normothermia with assistance of two different SBS consisting of only blood pump and oxygenator. Hemodynamic variables were assessed with transpulmonary thermodilution and transesophageal echocardiography. Plasma levels of proinflammatory and antiinflammatory mediators were measured perioperatively. After CPB, variables of global hemodynamics and systolic ventricular function did not differ among groups. Left ventricular diastolic function was impaired after CPB equally in all groups (P < 0.01 versus pre-CPB). At the end of surgery, there was more need for vasopressor (norepinephrine) support in both SBS groups than in the cCPB group (P < 0.01). After CPB, the release of interleukin (IL)-6 did not differ significantly among groups, whereas plasma levels of IL-10 were higher in the cCPB group (P < 0.01 versus SBS). The extent of myocardial necrosis (Troponin T) was comparable in all groups. We conclude that in our study, miniaturizing bypass systems and avoidance of cardioplegic arrest were not effective in improving hemodynamic performance and in attenuating the proinflammatory immune response after CPB.

Current mid-term outcome with an integrated surgical strategy for correction of d-transposition of the great arteries with ventricular septal defect and left ventricular outflow tract obstruction.

OBJECTIVES: The optimal surgical treatment strategy for transposition of the great arteries (TGA) associated with ventricular septal defect (VSD) and left ventricular outflow tract obstruction (LVOTO) leading to the best long-term outcome has not been established yet. The wide range of anatomical variability has led to the development of different surgical treatment options. In a retrospective single-centre review, we aimed to report the long-term outcome in patients who underwent biventricular repair. METHODS: Between 1992 and 2015, 49 patients underwent biventricular repair for TGA with VSD and LVOTO. On the basis of anatomical substrate, the type of repair was chosen. According to the type of repair, the patients were divided into two groups. Group A (n = 30 patients) includes all patients who underwent intraventricular rerouting (Rastelli, n = 22; réparation à l'étage ventriculaire, n = 8); Group B patients (n = 14) had repair on an arterial level (arterial switch operation + VSD closure + LVOTO resection, n = 10; Bex-Nikaidoh, n = 4). RESULTS: The follow-up was completed in 90% with a median follow-up of 12.3 years (17.1-17.7 years). There was no difference in survival (Group A: 97% at 5, 10 and 15 years; Group B: 92% at 5, 10 and 15 years) and functional outcome between the groups. All patients were in New York Heart Association class I, having sinus rhythm and normal left ventricular (LV) function. Neurological and educational development was adequate for age in all but one who suffered from attention-deficit hyperactivity disorder. Group A exhibited significantly less freedom from right ventricular outflow tract (RVOT) reoperations/reintervention (79, 48 and 21% at 5, 10 and 15 years) (P = 0.008) due to RVOT dysfunction and endocarditis. Event-free LVOTO survival in Group A at 5, 10 and 15 years amounted to 96, 91 and 91% and was similar to Group B with event-free LVOTO survival at 5, 10 and 15 years of 100, 88 and 88%, respectively. CONCLUSIONS: LV function is well preserved irrespective of the type of procedure. Patients who had undergone intraventricular rerouting (Group A) suffered from recurrent RVOT interventions due to RVOT dysfunction and endocarditis. The neurological outcome and the educational level were adequate for age in both groups. Executing the appropriate type of surgery for the individual patient's anatomy provides excellent functional and event-free outcome.

Xenon does not impair the responsiveness of cardiac muscle bundles to positive inotropic and chronotropic stimulation.

BACKGROUND: Most volatile anesthetics exhibit a direct myocardial depressant effect. This side effect often limits their applicability in patients with impaired cardiac function. Xenon is a new gaseous anesthetic that did not show any adverse cardiovascular effects in clinical and experimental studies. The authors tested the hypothesis that xenon does not affect myocardial contractility or the positive inotropic effect of isoproterenol, calcium, and increase in pacing rate in isolated guinea pig ventricular muscle bundles. METHODS: Thin ventricular muscle bundles from guinea pig hearts with a mean diameter of 0.4-0.45 mm were prepared under stereomicroscopic control. Force of contraction and contraction times were studied in muscles superfused with medium equilibrated with either 65% xenon and 35% oxygen (xenon group), 1.2% isoflurane in oxygen (isoflurane group), or 65% nitrogen and 35% oxygen (control group). In addition, the positive inotropic effects of calcium, isoproterenol (10(-10)-3 x 10(-8) M) and increasing frequency (0.5-2 Hz) were studied during xenon and isoflurane exposure. RESULTS: In contrast to isoflurane, xenon did not alter myocardial force of contraction or contraction times. The positive inotropic effect of isoproterenol, calcium, and increasing pacing frequencies did not differ between the muscles exposed to xenon and the control group. Isoflurane elicited the expected negative inotropic effect (30% reduction of force of contraction) but did not impair the response to inotropic stimuli. CONCLUSIONS: Xenon does not alter myocardial contractility and the response to inotropic stimuli such as calcium, isoproterenol, or increase in pacing frequency in isolated guinea pig ventricular muscle bundles.