Deleterious effect of hypothermia in myocardial protection against cold ischemia: a comparative study in isolated rat hearts.

BACKGROUND: There is a growing need to improve heart preservation benefit the performance of cardiac operations, decrease morbidity, and more important, increase the donor pool. Therefore, the objective of this study was to evaluate the cardioprotective effects of Krebs-Henseleit buffer (KHB), Bretschneider-HTK (HTK), St. Thomas No. 1 (STH-1), and Celsior (CEL) solutions infused at 10°C and 20°C. METHODS: Hearts isolated from male albino Wistar rats and prepared according to Langendorff were randomly divided equally into 8 groups according to the temperature of infusion (10°C or 20°C) and cardioprotective solutions (KHB, HTK, STH-1, and CEL). After stabilization with KHB at 37°C, baseline values were collected (control) for heart rate (HR), left ventricle systolic pressure (LVSP), coronary flow (CF), maximum rate of rise of left ventricular pressure during ventricular contraction (+dP/dt) and maximum rate of fall of left ventricular pressure during left ventricular relaxation (-dP/dt). The hearts were then perfused with cardioprotective solutions for 5 minutes and kept for 2 hours in static ischemia at 20°C. Data evaluation used analysis of variance (ANOVA) in all together randomized 2-way ANOVA and Tukey's test for multiple comparisons. The level of significance chosen was P < .05. RESULTS: We observed that all 4 solutions were able to recover HR, independent of temperature. Interestingly, STH-1 solution at 20°C showed HR above baseline throughout the experiment. An evaluation of the corresponding hemodynamic values (LVSP, +dP/dt, and -dP/dt) indicated that treatment with CEL solution was superior at both temperatures compared with the other solutions, and had better performance at 20°C. When analyzing performance on CF maintenance, we observed that it was temperature dependent. However, when applying both HTK and CEL, at 10°C and 20°C respectively, indicated better protection against development of tissue edema. Multiple comparisons between treatments and hemodynamic variable outcomes showed that using CEL solution resulted in significant improvement compared with the other solutions at both temperatures. CONCLUSION: The solutions investigated were not able to fully suppress the deleterious effects of ischemia and reperfusion of the heart. However, these results allow us to conclude that temperature and the cardioprotective solution are interdependent as far as myocardial protection. Although CEL solution is the best for in myocardial protection, more studies are needed to understand the interaction between temperature and perfusion solution used. This will lead to development of better and more efficient cardioprotective methods.

Comparative analysis of the performance of various crystalloid cardioplegic solutions on myocardial protection after prolonged cold ischemia.

INTRODUCTION: The quality and effectiveness of myocardial protection are fundamental problems to expand the use of and consequently good outcomes of donated hearts for transplantation. OBJECTIVE: The purpose of this investigation was to compare the cardioprotective effects of Krebs-Henseleit, Bretschneider-HTK, St Thomas, and Celsior solutions using a modified nonrecirculating Langendorff column model of isolated perfused rat heart during prolonged cold storage. MATERIALS AND METHODS: After removal 36 rat hearts underwent isolated perfusion into a Langendorff apparatus using Krebs-Henseleit solution for a 15-minute period of recovery; we excluded organs that did not maintain an aortic pressure above 100 m Hg. Subsequently, we equally distributed the hearts into four groups according to the cardioprotection solution; group 1, Krebs-Henseleit (control); group II, Bretschneider-HTK; group III, St Thomas; and group IV, Celsior. Each heart received the specific cardioplegic solution at 10°C for 2-hour storage at 20°C, before a 15 minutes perfusion with Krebs-Henseleit solution for recovery and stabilization. After 60 additional minutes of perfusion, every 5 minutes we determined heart rate (HR), coronary flow (CF), left ventricular systolic pressure (LVSP), and positive and negative peak of the first derivative of left ventricular pressure (+dP/dt and -dP/dt, respectively). RESULTS: Comparative analysis by Turkey's test showed the following performances among the groups at 60 minutes of reperfusion: HR: II = IV > III > I; CF: II = IV > I = III; LVSP: IV > I = II = III; +dP/dt: IV > I = II = III; and -dP/dt: IV = II > I = II. CONCLUSION: Cardioprotective solutions generally used in clinical practice are not able to avoid hemodynamic alterations in hearts exposed to prolonged ischemia. Celsior solution showed better performance than Bretschneider-HTK, St Thomas, and Krebs-Henseleit.

Effect of water storage on resin-dentin bond strengths formed by different bonding approaches.

OBJECTIVES: The purpose of this study was to evaluate the influence of water storage on resin-dentin bond strengths [microTBS] using different adhesive bonding approaches. MATERIALS AND METHODS: Flat superficial dentin surfaces of 24 extracted human third molars were exposed and polished to create a standardized smear layer. The teeth were randomly distributed into four different groups: Three-step etch-and-rinse (Adper Scotchbond Multi-Purpose, 3M ESPE-SBMP), two-step etch-and-rinse (Adper Single Bond 2, 3 M ESPE-SB); two-step self-etch (AdheSE, Ivoclar/Vivadent-AD); and self-etch 1 step (Adper Prompt L-Pop, 3M ESPE-LP). Following the adhesive application (n = 6), resin composite was incrementally applied (Filtek Supreme XT-3 M ESPE) in order to obtain bonded sticks, with a cross-sectioned area of 0.81 mm2. The bonded sticks were randomly divided and assigned to be tested after one day [OD] (n 30) or six months [6 M] of water storage [6 M] (n = 30). RESULTS: Two-way ANOVA and Tukey's test showed that none of the adhesives showed degradation after 6 M. SB achieved the highest microTBS both in the [OD] (49.13 MPa) and [6M] (40.27 MPa). Despite the highest values in both time evaluations, the microTBS of SB significantly reduced after 6M. LP showed the lowest microTBS in both periods of evaluation (18.35 and 18.34 MPa). CONCLUSIONS: Although a significant degradation was only observed for SB, this was the adhesive that showed the highest microTBS after 6 M of water storage.

Volatile cardioplegia: fast normothermic cardiac arrest induction and recovery with halothane in isolated rat hearts.

To study the effect of halothane as a cardioplegic agent, ten Wistar rats were anesthetized by ether inhalation and their hearts were perfused in a Langendorff system with Krebs-Henseleit solution (36 degrees C; 90 cm H2O pressure). After a 15-min period for stabilization the control values for heart rate, force(T), dT/dt and coronary flow were recorded and a halothane-enriched solution (same temperature and pressure) was perfused until cardiac arrest was obtained. The same Krebs-Henseleit solution was reperfused again and the parameters studied were recorded after 1, 3, 5, 10, 20 and 30 min. Cardiac arrest occurred in all hearts during the first two min of perfusion with halothane-bubbled solution. One minute after reperfusion without halothane, the following parameters reported in terms of control values were obtained: 90.5% of control heart rate(266.9 +/- 43.4 to 231.5 +/- 71.0 bpm), 20.2% of the force (1.83 +/- 0.28 to 0.37 +/- 0.25 g), 19.8% of dT/dt (46.0 +/- 7.0 to 9.3 +/- 6.0 g/s) and 90.8% of coronary flow (9.9 +/- 1.5 to 9.4 +/- 1.5 ml/min). After 3 min of perfusion they changed to 99.0% heart rate (261.0 +/- 48.2), 98.9% force (1.81 +/- 0.33), 98.6 dT/dt (45.0 +/- 8.2) and 94.8% coronary flow (9.3 +/- 1.4). At 5 min 100.8% (267.0 +/- 40.6) heart rate, 105.0% (1.92 +/- 0.29) force and 104.4% (48.2 +/- 7.2) dT/dt were recorded and maintained without significant differences (P > 0.01) until the end of the experiment. These data demonstrate that volatile cardioplegia with halothane is an effective technique for fast induction of and prompt recovery from normothermic cardiac arrest of the rat heart.

Volatile cardioplegia: fast normothermic cardiac arrest induction and recovery with halothane in isolated rat hearts

To study the effect of halothane as a cardioplegic agent, ten Wistar rats were anesthetized by ether inhalation and their hearts were perfused in a Langgendorff system with Krebs-Henseleit solution (36 graus Celsius; 90 cm H2O pressure). After a 15-min period for stabilization the control values for heart rate, force (T), dT/dt and coronary flow were recorded and a halothane-enriched solution (same temperature and pressure) was perfused until cardiac arrest was obtained. The same Krebs-Henseleit solution was reperfused again and the parameters studied were recorded after 1,3,5,10,20 and 30 min. Cardiac arrest occurred in all hearts during the first two min of perfusion with halothanebubbled solution. One minute after reperfusion without halothane, the following parameters reported in terms of control values were obtained: 90.5 percent of control heart rate (266.9 + 43.4 to 231.5 + 71.0 bpm), 20.2 percent of the force (1.83 + 0.28 to 0.37 + 0.25 g), 19.8 percent of dT/dt (46.0 + 7.0 to 9.3 + 6.0 g/s) and 90.8 percent of coronary flow (9.9 + 1.5 to 9.4 + 1.5 ml/min). After 3 min of perfusion they changed to 99.0 percent heart rate (261.0 + 48.2), 98.9 percent force (1.81 + 0.33), 98.6 dT/dt (45.0 + 8.2) and 94.8 percent coronary flow (9.3 + 1.4). At 5 min 100.8 percent (267.0 + 40.6) heart rate, 105.0 percent (1.92 + 0.29) force and 104.4 percent (48.2 + 7.2) dT/dt were recorded and maintained without significant differences (P>0.01) until the end of the experiment. These data demonstrate that volatile cardioplegia with halothane is an effective technique for fast induction of and prompt recovery from normothermic cardiac arrest of the rat heart.

[Effect of diazepam on myocardial contraction and on the response to dopamine. Study in isolated rat hearts]. / Efeito do diazepam na contratilidade miocárdica e na resposta à dopamina. Estudo em corações isolados de ratos.

PURPOSE: The myocardial contractility variations and the cardiac rate were studied in isolated hearts of rats with injection of diazepam, dopamine and the association of both. METHODS: In all animals, after anesthesia, the hearts were removed and perfused with Krebs-Henseleit solution enriched by 95% O2 under a constant pressure of 90 cm H2O, until complete stabilization, for control value recordings. The following groups were studied: I) ten hearts: after stabilization the control values were recorded and dopamine (3 micrograms/ml) injected; IIA and IIB): also ten hearts were used and submitted to 50 micrograms and 100 micrograms of diazepam injections respectively. III) ten hearts studied with 50 micrograms of diazepam and 3 micrograms/ml of dopamine injection in a sequential form. RESULTS: Myocardial contractility arose in group I, from 37 g.seg-1 (control mean-value) to 70 and 53 g.seg-1 (1st and 3rd min); p < 0.001. In the groups IIA and IIB the dT/dt fell considerably in relation to the control: 35 g.seg-1 to 24 and 30 g.seg-1 (1st and 3rd min)--group IIA; p < 0.001 -32 g.seg-1 to 22 and 25 g.seg-1 (1st and 3rd min)--group IIB; p < 0.001. In the group III, a partial inhibition of the inotropic effects of dopamine by the injection of diazepam was observed. Heart rate follows fully the dT/dt variations in the groups IIA, IIB and III. CONCLUSION: Diazepam presents inotropic and chronotropic negative effects with the 50 micrograms as well as with 100 micrograms injection and the chronotropic and inotropic effect of dopamine (3 micrograms) injection was partially inhibited by the previous injection (50 micrograms) of diazepam.

Reversäo pelo flumazenil do efeito cardiodepressor induzido pelo diazepam / Reversal by flumazenil of the cardiodepressant effect induced by diazepam

Foram estudados em sete ratos de raça wistar os efeitos do antagonista dos receptores GR (centrais). Flumazenil (8-fluoro-1,6-dihidro-5-metil-5-fenil-2h-1,4-benzodiazepina-3-carboxilato de etila) nas concentrações de dez mcg/ml, na depressÒo miocßrdica induzida pelo Diazepam (7-cloro-1,3-dihidro-1-metil-5-fenil-2h-1,4-benzodiazepin-1-ona) em doses de 100 mcg/ml em coraçöes isolados de ratos. Nestes experimentos foi utilizado o mÚtodo de LANGENDORFF e tÚcnica de GOTTLIEB e MAGNUS, modificada por PITCHON, utilizando como perfusato a soluçÒo de Krebs-Henseleit. Podemos constatar que nesta experimentaçÒo, o Flumazenil foi capaz de antagonizar os efeitos cardioinibidores do Diazepam. Estas açöes nos levam a sugerir a presença de receptores Gabarelacionados nos coraçöes isolados estudados.

[Spectral analysis of the arterial pulse during extracorporeal circulation. Experimental study in dogs]. / Análise espectral do pulso arterial durante a circulação extracorpórea. Estudo experimental em cães.

PURPOSE: Spectral analysis of arterial pulse was performed during cardiopulmonary bypass with both pulsatile and continuous flow in order to evaluate the pulse model best suitable to reproduce physiological circulatory conditions. MATERIAL AND METHODS: Ten adult mongrel dogs were submitted to cardiopulmonary bypass with a roller pump for continuous flow and pulsatile flow pump in parallel. The physiological pressure waves, the roller pump waves and the pulsatile pump flow waves were recorded. During the pulsatile flow we varied the ejection period of the pump in relation to the total cycle by 70%, 60%, 50%, 40% and 30%. RESULTS: The roller pump flow showed a bifid wave followed by single peak wave. During spectral analysis we observed three harmonic components of the same amplitude. The using of the pulsatile pump flow proportioned, by spectral analysis, harmonic components whose amplitudes are inversely proportional for ejection/cycle ratio. CONCLUSION: The fundamental component of the pressure wave during the physiological flow, the pulsatile flow, and that of the roller pump stays the same, if the same blood flow is maintained; the pulse of the flow is inversely proportional to the ejection/cycle ratio; the roller pump produces a flow pattern that cannot be described as laminar; the ejection/cycle ratio of 30% seemed ideal for the performance of pulsatile flow perfusion.

Importância da oxigenação de soluções cardiológicas para proteção miocárdica em cirurgia cardíaca / Importance of the oxygenation of cardioplegic solutions for myocardial protection in cardiac surgery

Foram estudados 50 caes mesticos distribuidos em cinco grupos que diferiam pelo tipo de solucao cardioplegica. Os seguintes resultados foram obtidos: 1) Nenhuma das solucoes cardioplegicas usadas inibiu completamente o metabolismo miocardico; 2) O miocardio submetido a cardioplegia extraiu oxigenio (maximo de 2,90 ml de O2/ 100 g de miocardio/min) das solucoes oxigenadas, com pO2 superior a 500 mm Hg; 3) Solucoes cardioplegicas nao oxigenadas resultaram em extracao minima de oxigenio pelo miocardio (maximo de 0,77 ml de 02/ 100 g de miocardio/min); 4) Ocorreu sinergismo de acao entre o verapamil e o ionte magnesio no bloqueio do metabolismo cardiaco, em nivel nao obtido por qualquer das substancias isoladamente

Vascular anastomosis by argon laser beam.

Twenty-four mongrel dogs, weighing 13 to 24 kg, were used to study the effectiveness of anastomosis by Argon Laser beam. After anesthesia, intubation and controlled ventilation, they were submitted to three types of vascular anastomoses: saphenous vein intercarotid artery bypass; left mammary artery/left anterior descending coronary artery bypass; and veno-venous anastomosis. In all groups, 0.8 to 1.5 watts of Argon Laser power were applied for a total time of 90 to 300 seconds. The lower power was for veno-venous anastomoses and the greater was applied for arterial anastomoses. The mean values of resistance of the laser anastomosis to pressure-induced repture were 730 mm Hg in the immediate postoperative study, but increased to 2,500 mm Hg 30 days after surgery. No signs of occlusion were demonstrated at the anastomotic sites by the angiographic and anatomopathological studies performed.

Disturbios de conducao do ramo direito por fechamento da comunicacao interventricular atraves de atriotomia. / Conduction disorders of right bundle by closing of the intraventricular comunication by atriotomy

Os autores avaliam os disturbios de conducao em 3 pacientes submetidos a correcao cirurgica da comunicacao interventricular (CIV) por via atrial direita. Os pacientes operados de 1978 a 1979 foram analisados eletrocardiograficamente durante 15 meses.Encontraram-se cifras mais baixas de bloqueio completo do ramo direito (BCRD), bloqueio atrioventricular total (BAVT) e hemi-bloqueio anterior esquerdo (HBAE) quando comparado a resultados de outros centros que utilizaram esta ou outra via.Devido a esta vantagem alem de preservar a integridade das fibras musculares do ventriculo direito (VD) atriotomia e uma excelente via de acesso a maioria da CIVs