수동적 체위변화가 혈중 Catecholamine 농도 및 심장혈관계에 미치는 영향

Abstract

Many investigators have studied the effect of gravity on cardiovascular homeostasis during orthostasis and antiorthostasis by conventional approaches such as measurements of the heart rate, arterial blood pressure, central venous pressure, cardiac function parameters including stroke volume of the heart, vascular blood flow, peripheral vascular resistance and respiratory rate. Furthermore recently it has been interested to evaluate the hormonal changes in catecholamines, renin-angiotensin-aldosterone and antidiuretic hormone as the indicator of the regulatory mechanisms of both cardiovascular and renal function to postural changes. Catecholamines(norepinephrine and epinephrine) are transmitters of the sympathetic nerve ending and the plasma concentration of catecholamines represents the total activity of the sympathetic nerves in the body. This study was performed to measure the concentration of plasma catecholamines and the parameters of cardiovascular function in an upright and a head-down position. The aim of this study was to evaluate the effect of catecholamines in conjunction with various cardiovascular responses in the passive tilt. Eleven anesthetized dogs of 8-12kg were examined by passive tilting from the supine position to 77˚ upright (orthostasis), and from supine position to -90˚ head-down (antiorthostasis), for 10 minutes on each tilt. The concentration of plasma catecholamines was measured by a modified radioenzymatic method of Peuler and Johnson at every nine to ten minute period when orthostasis and antiorthostasis were accomplished after each tilt. Minute blood flow of the common carotid artery, external jugular vein, femoral artery and pressure, heart rate and respiratory rate were also measured. The measurements obtained from the upright and head-down tilt were compared with those from the supine position. The results obtained are as follows: In orthostasis, the concentration of plasma norepinephrine and epinephrine was increased from 140±11.5 and 131±12.7 pg/ml in the supine position to 150±12.6 and 120±10.3 pg/ml respectively, however the changes were statistically insignificant. The blood flow of the artery through both head and lower leg was significantly (p<0.01) decreased. Systolic and diastolic blood pressure were significantly(p<0.05) decreased and pulse pressure was also decreased. The heart tate was markedly (p<0.05) increased. The respiratory rate was not changed except for the initial small decrease. In antiorthostasis, the plasma norepinephrine was significantly (p<0.05) increased to 167±15.2pg/ml and the epinephrine was slightly increased in comparison with the supine position. The blood flow through head, arterial blood pressure and pulse pressure were not significantly changed, but the blood flow through the lower leg was significantly (p<0.05) decreased. The heart rate was increased and the respiratory rate showed an initial small increase. In conclusion, it seems that the adaptation of dogs to short term orthostasis after an abrupt passive tilt is maintained through cardiovascular homeostatic mechanism such as baroreceptor and cardiopulmonary receptor reflexes.