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LETTER TO THE EDITOR

Dynamic Variables of Fluid Responsiveness may be Related to the Type of Volume Challenge Performed

Department of Anaesthesiology and Intensive Care Medicine; University Hospital Schleswig-Holstein; Campus Kiel, Germany; renner{at}anaesthesie.uni-kiel.de

To the Editor:

Charron et al. (1) addressed the impact of tidal volume on pulse pressure variation (% P_p) and on the aortic velocity–time integral (%VTI_Ao). The authors used a small volume of hydroxyethyl starch (100 mL over 60 s) as a volume challenge, although there was no change of left ventricular end diastolic area index (LVEDA_i). The authors refer to a study that applied an "equivalent fluid challenge" of 500 mL over 5–10 min (2). We question whether a rapid infusion of 100 mL hydroxyethyl starch 6% over 60 s is equivalent to 500 mL applied over 5–10 min.

Hemodynamic variables were collected during three 15-min time intervals while the depth of tidal volume (V_T) was varied. It has been shown previously that after an infusion of 20 mL/kg hydroxyethylstarch 6% over 15 min, <50% of the volume initially infused remains in the intravascular space (3). This suggests that following the first period of data collection, a large proportion of the initially applied volume disappeared. This is supported by lack of change in LVEDA_i, suggesting an insufficient volume challenge.

The absence of significant changes in %VTI_Ao with changes tidal volume is counterintuitive. A close relationship exists between VTI_Ao as a surrogate parameter of stroke volume and V_T (4). It is surprising that authors used VTI_Ao as their index, given the technical limitations, rather than using thermodilution, the clinically accepted gold standard (5).

REFERENCES

1. Charron C, Fessenmeyer C, Cosson C, et al. The influence of tidal volume on the dynamic variables of fluid responsiveness in critically ill patients. Anesth Analg 2006;102:1511–7.[Abstract/Free Full Text]
2. Axler O, Tousignant C, Thompson CR, et al. Small hemodynamic effect of typical rapid volume infusions in critically ill patients. Crit Care Med 1997;25:965–70.[Web of Science][Medline]
3. Rehm M, Haller M, Orth V, et al. Changes in blood volume and hematocrit during acute preoperative volume loading with 5% albumin or 6% hetastarch solutions in patients before radical hysterectomy. Anesthesiology 2001;95:849–56.[Web of Science][Medline]
4. Slama M, Masson H, Teboul JL, et al. Respiratory variations of aortic VTI: a new index of hypovolemia and fluid responsiveness. Am J Physiol Heart Circ Physiol 2002;283:H1729–33.[Abstract/Free Full Text]
5. Medin DL, Brown DT, Wesley R, et al. Validation of continuous thermodilution cardiac output in critically ill patients with analysis of systematic errors. J Crit Care 1998;13:184–9.[Web of Science][Medline]

This article has been cited by other articles:

				C. Charron, C. Fessenmeyer, C. Cosson, J.-L. Hebert, D. Benhamou, J. X. Mazoit, and A. Edouard Dynamic Variables of Fluid Responsiveness may be Related to the Type of Volume Challenge Performed Anesth. Analg., June 1, 2007; 104(6): 1603 - 1603. [Full Text] [PDF]

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