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Hepatic microvascular effects of terbutaline in experimental cardiogenic shock in rats
Insights
Terbutaline administration improved hemodynamics and liver microcirculation during experimental cardiogenic shock. This beta-2 agonist reduced peripheral resistance and eased circulatory load in rats with myocardial infarction.
Area of Science:
- Cardiovascular Physiology
- Microcirculation Research
- Pharmacology
Background:
- Myocardial infarction induces cardiogenic shock, characterized by compromised cardiac output and systemic hypotension.
- Liver microcirculation is significantly affected during shock, with observed sinusoidal constriction and reduced erythrocyte flow velocity.
Purpose of the Study:
- To investigate the effects of the beta-2 adrenoceptor agonist terbutaline on liver microcirculation during experimental cardiogenic shock.
- To assess terbutaline's capacity to mitigate hemodynamic derangements and restore microcirculatory function.
Main Methods:
- Experimental myocardial infarction was induced in rats via left ventricular cauterization.
- In vivo television microscopy was employed to quantitatively measure liver sinusoid diameter and erythrocyte flow velocity.
- Hemodynamic parameters and microcirculatory responses to terbutaline (0.15 mg/kg IV) were analyzed.
Main Results:
- Cardiogenic shock led to 80% sinusoid constriction, 20% dilatation, and a 50% reduction in erythrocyte flow velocity.
- Terbutaline partially restored cardiac output and systemic arterial pressure.
- Terbutaline normalized sinusoid diameters but only partially increased erythrocyte flow velocity in the liver.
Conclusions:
- Terbutaline administration improves systemic hemodynamics and liver microcirculation during experimental cardiogenic shock.
- The drug's vasodilatory action on liver sinusoids may decrease peripheral resistance and reduce circulatory workload.
- Terbutaline shows potential as a therapeutic agent for managing cardiogenic shock by improving microcirculatory perfusion.
Abstract:
1. Experimental myocardial infarction was produced in rats by direct electrical cauterization of the myocardium of left ventricle. This produced cardiogenic shock with the accompanying haemodynamic changes of low cardiac output, low mean arterial pressure, raised central venous pressure and an absence of cardiac arrhythmias. 2. The liver microcirculation was observed using in vivo television microscope method. The diameter and erythrocyte flow velocity in the liver sinusoids were measured quantitatively. 3. During experimental cardiogenic shock 80% of the liver sinusoids were constricted; the remaining 20% showed dilatation. In all these liver sinusoids the erythrocyte flow velocity was only 50% of the pre-shock level. 4. Intravenous injection of the selective beta 2-adrenoceptor agonist terbutaline (0.15 mg/kg) restored the systemic arterial pressure to pre-shcok levels and partially raised the cardiac output. In the liver microcirculation terbutaline restored both constricted and dilated liver sinusoids to pre-shock calibres, but only partially raised erythrocyte flow velocity. 5. It is proposed that during experimental cardiogenic shock, terbutaline produces dilatation in the terminal liver microcirculation by opening sphincters of liver sinusoids and restores sinusoid diameters to pre-shock calibres. Therefore, terbutaline has the capacity to decrease peripheral resistance and unload the circulation during cardiogenic shock.