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INTRODUCTION
In critically ill patients with hypoperfusion, intravascular volume expansion (VE) is a cornerstone of hemodynamic therapy. Early resuscitation protocols including fluid therapy can be life-saving early in the course of sepsis.[1,2] However, VE may induce peripheral and pulmonary edema, and worsen microvascular perfusion and oxygen delivery in patients with right or left ventricular dysfunction.[3] In a preload unresponsive patient, large VE can exacerbate pulmonary edema, cause respiratory failure, prolong mechanical ventilation time, and contribute to the development of intra-abdominal hypertension.[4] Passive leg raising (PLR) was supposed to transfer venous blood from the legs toward the intrathoracic compartment, increasing the intrathoracic blood volume and the cardiac preload. The aim of the present study was to determine if SVI measurement could be used in conjunction with PLR to predict the hemodynamic response to VE.
METHODS
Patients
This study prospectively assessed consecutive patients admitted in the ICU (33 beds) of the First Affiliated Hospital, Zhejiang University School of Medicine and the ICU (26 beds) of Ningbo Medical Treatment Center Lihuili Hospital from May 2010 to December 2011. Thirty-two mechanically ventilated patients, defined septic chock[5] with acute circulatory failure, were eligible to participate in the study with written informed consent. Hemodynamic indices including SVI were monitored with the technique of pulse indicator continuous cardiac output (PiCCO) (Pulsion Medical Systems AG, Munich, Germany). Acute circulatory failure was defined as the presence of at least one clinical sign of inadequate tissue perfusion as follows: systolic blood pressure<90 mmHg (or a decrease of >40 mmHg in previously hypertensive patients) or the need for vasopressors (dopamine>5 μg/kg per minute or norepinephrine>0.1 μg/kg per minute) to maintain a systolic blood pressure>90 mmHg; urine output of <0.5 mL/kg per hour for at least 1 hour; tachycardia (heart rate>100/min); and mottled skin.[6] Non-sinus rhythm or arrhythmia ones and parturients were excluded.
Mechanical ventilation variables
The patients were sedated (Ramsay score 4) and ventilated in mode of volume control. The tidal volume was 10 mL/kg and the level of positive end-expiratory pressure was 5 cmH2O (1 cmH2O=0.098 kPa).
Measurements
A 4F thermistor-tipped arterial catheter (Pulsiocath thermodilution catheter; Pulsion Medical Systems, Munich, Germany) was inserted in the femoral artery, which connected to the PiCCO (Pulsion Medical Systems, Munich,...