Early preload adaptation in septic shock? A transesophageal echocardiographic study

Background: An accepted concept in septic shock is that preload adaptation by acute left ventricular dilatation, when occurring spontaneously or with the aid of volume loading, permits maintenance of an adequate cardiac outpu t, leading to final recovery. From a physiologic point of view, this concep t appears debatable because a normal pericardium exerts a restraining actio n on a normal heart. Methods: During a 26-month period, the authors investigated, by transesopha geal echocardiography, 40 patients hospitalized in their unit for an episod e of septic shock. Transesophageal echocardiography was performed in the fi st hours after admission, proceeded by correction of any hypovolemia, and s tabilization of arterial pressure by vasoactive agent infusion if necessary . Left ventricular dimensions were obtained in long- and short-axis views, permitting calculation of left ventricular ejection fraction (long axis) an d fractional area contraction (short axis). Stroke index was simultaneously measured by the Doppler technique. Results: Stroke index was strongly correlated with both echocardiographic l eft ventricle ejection fraction (r = 0.75; P < 0.0001) and left ventricle f ractional area contraction (r = 0.76; P < 0.0001), whereas it was independe nt of echocardiographic left ventricle diastolic dimensions. Conclusions: The transesophageal echocardiography study was unable to confi rm the reality of the concept of early preload adaptation by left ventricul ar dilatation in septic shock. Conversely, because left ventricular volume always remained in a normal range after correcting hypovolemia, systolic fu nction was the unique determinant of stroke index in septic shock.