Man…This (Ultra)Sounds Good!

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Ultrasound has, in many ways, become the stethoscope of the 21st century – its ease of use, repeatability and low cost have made it a standard of care for a variety of medical conditions.

This week’s article demonstrates the value of ultrasound when used as a tool for fluid resuscitation guidance in patients with septic shock.

The article, titled “Ultrasound-guided fluid resuscitation versus usual care guided fluid resuscitation in patients with septic shock: a systematic review and meta-analysis”, by Chen et al, analyzed and summarized data from randomized controlled trials evaluating the utility of ultrasound-guided fluid resuscitation in patients with septic shock.

The authors included 12 randomized controlled trials (RCTs) with a total of 947 participants (473 treated with ultrasound-guided fluid resuscitation) in their analysis. All of the included RCTs enrolled adult patients with a definitive diagnosis of septic shock who received initial fluid resuscitation in the emergency department (ED) or the intensive care unit (ICU). The intervention groups of the studies received fluid resuscitation guided by ultrasound measurements/estimates of intravascular fluid status, fluid responsiveness and hemodynamic parameters, while the control groups received fluid resuscitation as recommended by the Surviving Sepsis Campaign (SSC) guidelines.

Mortality during the study period was set as the primary outcome, while secondary outcomes included total fluid volume received in the first 24 hours, dose or duration of application of vasoactive drugs, length of hospital stay and ICU stay.

Following statistical analysis of the data from the included studies (analyzed using a fixed-effects model), ultrasound-guided fluid resuscitation was associated with a statistically significant, 22% reduction in mortality [risk ratio (RR) 0.78; 95% confidence interval (CI): 0.65–0.94; p = 0.007]. Heterogeneity between the studies was relatively low (I2 = 29%). A sensitivity analysis (sequential removal of individual studies from the meta-analysis in order to see if the summarized results will change or lose statistical significance) was performed, with the results remaining consistent and significant.

Total fluid volume received during the first 24 hours was expressed as a mean difference (MD), with an MD of 0 signifying no reduction in fluid volume received, negative values (e.g. MD -1) signifying reduction in volume received with ultrasound-guided resuscitation and positive values (e.g. MD +1) signifying reduction in volume received with usual care. The MD for total fluid volume received during the first 24 hours was −1.02 (95% CI −1.28 to −0.75, p < 0.001), demonstrating a significant reduction of volume received when using ultrasound-guided fluid resuscitation. Following sensitivity analysis, the results remained consistent and significant.

There was no statistically significant difference in the length of hospital or ICU stay between the groups. However, when a subgroup analysis dividing patients into subgroups based on whether fluid resuscitation was guided by inferior vena cava (IVC) measurements or echocardiography was conducted, patients in the IVC measurement subgroup had a significantly shorter hospital and ICU stay, compared to the usual care group.

Other secondary outcomes demonstrated a high degree of heterogeneity and were based on 2-3 studies total, making credible statistical analysis difficult.

Regarding the ultrasound measurements and windows used to guide fluid resuscitation, 8 studies used a combination of IVC diameter and IVC collapsibility index to evaluate fluid responsiveness, 5 used echocardiographic parameters [including heart chamber measurements, left ventricle ejection fraction (LVEF), left ventricle outflow tract velocity time integral (LVOT VTI) and tricuspid annular plane systolic excursion (TAPSE)], while 2 used the number of B lines on lung ultrasound and 2 used the passive leg raise.

 

Summarily, this meta-analysis, which included 12 RCTs comparing ultrasound-guided fluid resuscitation to usual care in septic shock patients demonstrated a statistically significant reduction in both mortality during the study period and total fluid volume received during the first 24 hours of care, with the results remaining consistent and significant following a sensitivity analysis.

However, the studies used different ultrasound-guided measurements, therefore the question of the optimal ultrasound measurement for guiding fluid resuscitation remains open. Following subgroup analysis, secondary outcomes like hospital and ICU length of stay were significantly improved when IVC-based measurements were used, with no such improvements noted with echocardiographic measurements.

That’s it for this week, stay safe and keep using your ultrasound machine.

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