Impact of Body Size on Stroke Volume Response to Passive Leg Raising in Spontaneously Breathing Children

To test whether indexing stroke volume change (ΔSV%) to body size during the passive leg raising (PLR) test in spontanoeusly breathing children improves accuracy to detect fluid responsiveness (FR).

Observational study.

Two pediatric hospitals.

Children age 2-16 years.

None.

In study phase 1, we measured ΔSV% by echocardiography during PLR in healthy children. A positive PLR test was defined as a mean ΔSV% greater than or equal to 10%. The correlation between ΔSV% with body size parameters was assessed, and optimal body size indexation was generated. In study phase 2, the PLR was performed in acutely ill children before a fluid challenge of 20 mL/kg of normal saline. ΔSV% was measured at 10 and 20 mL/kg and FR was defined as ΔSV% greater than or equal to 10% or greater than or equal to 15% (four possible definitions of FR). The diagnostic performance of the PLR using nonindexed and indexed ΔSV% to identify FR was assessed using the area under the receiver operating characteristic curve (AUC) analyses. We recruited 133 and 87 children in phase 1 and 2, respectively. Mean ΔSV% and the proportion of positive PLR test increased with age tertiles both in healthy children and children receiving a fluid challenge ( p ≤ 0.01). ΔSV% positively correlated with body size. Indexing by height (i.e., [ΔSV%/0.0006] × height 2.493 ) removed the effect of body size. The AUC of the PLR for FR ranged from 0.745 to 0.802, depending on the FR definition applied. The use of height-indexed ΔSV% improved diagnostic performance (AUC range, 0.852-0.894) compared to non-indexed ΔSV%, although the result was significant only when FR was defined as ΔSV% greater than 15% after 20 mL/kg (DeLong test < 0.05).

The response in ΔSV% to a PLR is greatly influenced by body size. Indexing the value by height may improve the diagnostic performance of the PLR in children.