摘要:

Background Testing for the susceptibility of vasodepressor reaction in humans involves the combination of restriction of venous return by passive upright tilting and the administration of isoproterenol.We developed an experimental rat model in which vasodepressor reactions are induced when the inferior vena cava is occluded during an infusion of isoproterenol. The reactions are characterized by the development of paradoxical bradycardia during the period of inferior vena cava occlusion.Methods and Results Inferior vena cava occlusion was performed for 60 seconds, and the maximal changes in RR interval were measured during seven states as follows:(1) when inferior vena cava occlusion was performed under control conditions in 40 rats, the rate accelerated in all 40 rats (Delta RR, -15.6+-1.9 milliseconds in 25 rats, P<.001; Delta RR, -13.3+-1.7 milliseconds in 10 rats, P<.001); (2) when inferior vena cava occlusion was performed in 25 rats during an infusion of isoproterenol, a vasodepressor reaction was observed in all rats as the heart rate slowed (Delta RR, +92.7+-8.3 milliseconds, P<.001); (3) when inferior vena cava occlusion was performed in 10 rats during an infusion of dobutamine, a selective beta1-agonist, a vasodepressor reaction was observed in all rats as the heart rate slowed (Delta RR, +63.3+-10.6 milliseconds, P<.001); (4) when inferior vena cava occlusion was performed in 5 rats during an infusion of salbutamol, a selective beta2-agonist, vasodepressor reaction was not observed as the heart rate accelerated in all rats (Delta RR, -11.4+-2.8 milliseconds, P<.002); (5) the vasodepressor reaction induced by either dobutamine or isoproterenol was inhibited by atenelol, a selective beta1-adrenergic receptor antagonist; (6) the vasodepressor reaction induced by isoproterenol was inhibited by propranolol (lipophilic) and sotalol (nonlipophilic) beta -blockers and there was a dose-dependent attenuation by propranolol of the maximal RR interval slowing during inferior vena cava occlusion; and (7) butoxamine, a selective beta2-adrenergic receptor antagonist, attenuated but did not block the vasodepressor reaction observed during an infusion of isoproterenol.Conclusions Reduced cardiac volume combined with beta1-adrenergic stimulation can stimulate a vasodepressor reaction in rats. beta (2) -Adrenergic receptors play little or no role in the reaction. The vasodepressor reaction can be blocked by selective or nonselective beta1-adrenergic antagonists independent of the drug's ability to penetrate the central nervous system. The application of these findings to humans remains to be elucidated. (Circulation. 1994;89:2401-2411.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background Normal ionic perfusate containing butanedione monoxime (BDM), a reversible myofilament inhibitor, could be better than either a high potassium (KCl) or a low calcium (CaCl2) perfusate for long-term cardiac preservation. This hypothesis was tested in 70 isolated guinea pig hearts.Methods and Results Three groups-time control (8 hours, 37 degrees C), cold control (22 hours, 3.8 degrees C), and cold+BDM (22 hours)--were perfused with typical Krebs-Ringer solution (2.5 mmol/L CaCl2and 4.5 mmol/L KCl). Two other groups were cold perfused for 22 hours either with 2.5 mmol/L CaCl2+20 mmol/L KCl (high) or with 0.5 mmol/L CaCl2(low)+4.5 mmol/L KCl. These changes were maintained from 20 minutes before cold perfusion until 30 minutes after rewarming to 37 degrees C. Coronary vasodilator reserve was tested before cold perfusion and 2 hours after warm reperfusion with adenosine (Ade), acetylcholine (Ach, endothelium dependent), and nitroprusside (NP, endothelium independent). Each treatment decreased left ventricular pressure (LVP) by more than 80% before cold perfusion. During warm reperfusion, LVP was lower in cold control (-72+-5%), high KCl (-76+-4%), and low CaCl2(-80+-4%) groups than in BDM (-38+-3%) or time control (-18+-4%) groups; coronary flow (CF) was lower in high KCl (-67+-4%) and low CaCl2(-54+-7%) groups than in cold control (-37+-6%), BDM (-30+-5%), or time control (+2+-3%) groups; and percent oxygen extraction (controls, 62+-4%) was higher in the high KCl group (83+-6%) than in cold control (72+-3%), BDM (73+-3%), low CaCl2(72+-5%), or time control (63+-3%) groups. CF responses to Ade, Ach, and NP (+103+-7%, +24+-5%, and +34+-5% before cold) were attenuated (+76+-6%, +18+-5%, and +23+-4%) in the time control group (5 hours later), were reduced but present in the BDM group (+10+-5%, -5+-5%, and -5+-5%), and were absent in both low CaCl2and high KCl groups after 2 hours of reperfusion.Conclusions Normal ionic BDM solution better preserves cardiac function and basal CF after prolonged cold perfusion than do cold control, high KCl, and low CaCl2solutions.Vasodilatory capacity is markedly diminished after perfusion with either the high KCl or the low CaCl2solution. (Circulation. 1994;89:2412-2420.)

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID