Monitoring Variations in Stroke Volume Enables Precise Evaluation of Fluid Resuscitation in Patients with Septic Shock on Pressure Support Ventilation

Research Article

Austin J Emergency & Crit Care Med. 2015;2(1): 1012.

Monitoring Variations in Stroke Volume Enables Precise Evaluation of Fluid Resuscitation in Patients with Septic Shock on Pressure Support Ventilation

Hagiwara A*, Kimira A, Sasaki R, Kobayashi K and Sato T

Department of Emergency Medicine and Critical Care, National Center for Global Health and Medicine, Japan

*Corresponding author: Akiyoshi Hagiwara, Department of Emergency Medicine and Critical Care, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku-ku, Tokyo 162-8655, Japan

Received: December 12, 2014; Accepted: February 04,, 2015 Published: February 06, 2015


Purpose: To determine whether stroke volume variation (SVV) is a useful indicator of fluid resuscitation in patients with septic shock on pressure support ventilation.

Subjects: We assessed 37 patients with septic shock who were fitted with FloTrac sensors (Edwards Lifesciences Ltd., Tokyo, Japan), hospitalized between October 2011 and August 2013 and managed using pressure support ventilation.

Methods: This is a prospective, observational, pilot study. Lactate (Lac), IVC diameter, IVC variation (ΔIVC), stroke volume index (SVI), and SVV (mean value at one hour) during initial fluid resuscitation were measured and the SVV value was continuously monitored. These parameters were measured again when the SVV curve decreased and flattened (stable SVV). Fluctuations in SVV during initial fluid resuscitation and stability were analyzed using fast Fourier transformation.

Result: The mean values of Lac, IVC diameters, and SVV during initial fluid therapy vs. stable SVV were 6.0 vs. 1.8 mmol/L, 11 vs. 19 mm, and 18.6 vs. 8.8%, respectively (p < 0.001). Fluctuations in SVV curves calculated by fast Fourier transformation resulted in a Lorentzian spectrum. The amplitude of all curves peaked at a frequency of 0 and became significantly lower when SVV was stable than during fluid therapy (1.3% vs. 3.7%; p < 0.001).

Conclusion: Continuous monitoring of SVV trends enables precise evaluation of fluid resuscitation in patients with septic shock on pressure support ventilation.

Keywords: Stroke volume variation; SVV; Stroke volume index; SVI; Septic shock; Fluid resuscitation; Lactate


Fluid resuscitation for severe sepsis can be based on either dynamic or static variables. Stroke volume variation (SVV) is considered a dynamic variable despite being ungraded for recommendation [1].

Continuous analysis of the arterial pulse contour from the arterial line of peripheral arteries, including the radial artery, has recently enabled measurements of cardiac stroke volume (SV) [2]. The SVV can be calculated using the formula: [(SVmax-SVmin)/SVmean × 100] (1), where SVmax is the maximum variation in stroke volume during the respiratory cycle, SVmin is the minimum variation in SV, and SVmean is (SVmax + SVmin)/2. The SVV has been described as a functional preload parameter that can indicate fluid responsiveness after a fluid challenge [2]. Patients on the steep or flat portions of the Frank-Starling curve will have high or low SVV, respectively. This implies that a greater SVV will result in a greater increase in SV and a decrease in SVV after a fluid challenge. Namely, the main advantage of using SVV to predict fluid responsiveness is that it dynamically predicts the status of individual patients from Frank-Starling curves [3]. The sensitivity and specificity of SVV is higher and its ability to determine fluid responsiveness is better than that of traditional indicators of volume status, namely, heart rate, mean arterial pressure, central venous pressure, pulmonary artery diastolic pressure, and pulmonary capillary arterial pressure [4-6]. When a 15% increase in stroke volume index (SVI) or cardiac index is defined as fluid responsiveness with an SVV cutoff of 11.6 ± 1.9%, the sensitivity and specificity are 0.82 (0.75-0.98) and 0.86 (0.77-0.92) respectively [6]. However, the effectiveness of SVV is limited to patients who are 100% mechanically ventilated (controlled ventilation) with tidal volumes of > 8 mL/kg and fixed respiratory rates.

Physicians in intensive care units must always consider lungprotective strategies during mechanical ventilation for critically ill patients. These strategies include lower tidal volumes (6 mL/kg) for positive-pressure ventilation. Several studies have attempted to determine effective dynamic parameters that might predict fluid responsiveness in such patients, but the findings require further analysis [7,8]. Perner et al. and Machare-Delgado et al. reported that SVV is unlikely to serve as an indicator of fluid responsiveness in patients under pressure support ventilation [9,10]. Whereas, Lanspa et al. recently reported on a prospective observational pilot study that SVV can predict hemodynamic response to fluid challenge in 14 septic shock patients with spontaneously breathing patients [11].

We considered that evaluating fluid responsiveness with SVV would be limited to one fluid challenge test in patients under pressure support ventilation. The present study aimed to determine whether SVV could serve as an indicator of fluid resuscitation in patients with septic shock under pressure support ventilation who undergo continuous fluid challenges as initial fluid resuscitation.

Materials and Methods


The Ethics Committee at our institution approved this prospective, observational, pilot study and written informed consent was waived because the study design is part of the current standard of care at our intensive care unit (ICU). The study was registered with the University Hospital Medical Information Network Clinical Trials Registry: UMIN-CTR ID UMIN000008339. All authors have any conflict of interest.

We defined septic shock as sepsis-induced hypotension persisting despite adequate fluid resuscitation (minimum of 30 mL/kg of crystalloids). Hypotension induced by sepsis was defined as systolic blood pressure (SBP) < 90 mmHg, mean arterial pressure < 70 mmHg, or a decrease in SBP > 40 mmHg or < 2 SD below normal for age in the absence of other causes of hypotension [12].

The enrollment criteria comprised patients with septic shock aged . 16 years who were hospitalized between October 2011 and August 2013. In addition, patients must have met the definition of the International Sepsis Definitions Conference, been initially treated based on the Surviving Sepsis Campaign 2008 [12], had hemodynamics in the radial artery invasively monitored, and been fitted with Vigileo/FloTrac version 3.01 sensors (Edwards Lifesciences Ltd., Tokyo, Japan) during initial fluid therapy and managed under pressure support ventilation.

The exclusion criteria comprised patients who declined intensive care, those with end stage malignant disease, arrhythmia, or abnormal blood flow due to congenital heart disease, or with a focus of infection that was surgically treated during initial fluid therapy.

Methods and measurements

Patient care was directed by the ICU team and did not involve the present findings.

Fluid and catecholamine administration was based on the Surviving Sepsis Campaign 2008. In addition to routine tests at our institution, we measured the diameter of the retrohepatic inferior vena cava (IVC diameter) and its respiratory variations (ΔIVC), as well as blood lactate values (Lac). The ΔIVC was calculated as (maximum IVC diameter-minimum IVC diameter)/maximum IVC diameter × 100 (%). The IVC was examined in subcostal sagittal sections. A 5-Mhz probe was attached to the echo unit of a Sonosite m-turbo ultrasound diagnostic system (Fujifilm Sonosite Inc., Tokyo, Japan). The origin of the major hepatic vein was initially detected and parameters were measured at the IVC diameter immediately proximal to the junction of the hepatic veins. The IVC was observed during one or more respiratory cycles in M mode and then the maximum and minimum anterior-posterior diameters during one respiratory cycle were measured. After fitting each patient with Vigileo/FloTrac sensors (FloTrac), cardiac output (CO), cardiac index, stroke volume, SVI and SVV were continuously monitored and stored as digital data every 20 seconds. The IVC diameter, ΔIVC, and LAC were measured at least every four hours during initial fluid resuscitation.

SVV was defined as stable when < 15% and the curve flattened without a decrease (Figure 1A and B). The flattened curve was visually assessed on the monitor by the attending physician. The diameters of the IVC, ΔIVC, and Lac, in addition to routine tests, were measured once again.