The role of vague nerve in the hemodynamic changes induced by acute biliary tract pressure increase

In order to explore the mechanism of hemodynamic changes caused by high biliary tract pressure, we established an animal model of high biliary tract pressure, in which the disturbance of hemodynamics developed. The cervical or abdominal vague nerve was then blocked. It was observed that when the biliary tract pressure was increased to 16 kPa and kept for 1 h, the arterial blood pressure and cardiac output decreased immediately and parallelly (P < 0.05). When the cervical or abdominal vague nerve were blocked or the pressure of the biliary tract was decreased to zero, both indices returned to normal immediately (P > 0.05). The change of cardiac output lags a little behind that of arterial blood pressure. It suggests that the signal of biliary tract pressure increase can be sent to the cardiovascular center through vague nerve, and the balance between sympathic and parasympathic nerve was broken, which led to the weakening of cardiac contraction and decrease of cardiac output. Due to the peripheral effects of vague nerve, hemodynamic resistance of vessels decreased, which brought about redistribution of peripheral blood flow. Both were the causes of hemodynamic disturbances. After the blood pressure decreased markedly, it showed a jump to normal state when cervical vague nerve was blocked. And the amplitude of diastolic blood pressure restored more than that of systolic blood pressure. This suggests that the cardiac output and peripheral blood resistance are important factors that cause the decrease of blood pressure.