脊椎手術での腹臥位体位変換における心拍出量変化

Effect of Changing to the Prone Position on Cardiac Output During Spinal Surgery

　低侵襲動脈圧心拍出量測定を用いて腹臥位への体位変換が血行動態へ及ぼす影響について調査した．対象は全身麻酔下に腹臥位で脊椎手術を施行した71例(男性47例，女性24例)である．麻酔導入後，腹臥位直前および体位変換後の心拍出係数(CI)，一回心拍出係数(SVI)，一回心拍出量呼吸性変動(SVV)を測定した．腹臥位直後から心機能を反映するCI，SVIは有意に低下し，血管内容量を反映するSVVは変化しなかった．術後，仰臥位に変換後はCI，SVIが有意に増加した．本研究により，腹臥位は心機能低下の危険性があり，血管内容量へは影響しないことが判明した．

　We assessed the effect of changing to the prone position on cardiac output in 71 patients (47 male, 24 female) who underwent spinal surgery under general anesthesia by the same method.　After induction of anesthesia, the patient's CI (cardiac index), SVI (stroke volume index), and SVV (stroke volume variation) were measured with an arterial-pressures-based-cardiac output monitor before and after changing to the prone position.　After the change to the prone position both CI and SVI, which reflect cardiac function, decreased, but SVV, which reflects intravascular volume, remained unchanged.　In addition, after changing back from the prone position to the supine position, both CI and SVV increased, and SVV remained unchanged.　We concluded that the prone position is a risk factor for decreased cardiac function.