Prediction of arterial pressure increase after fluid challenge

Thirty-six hypotensive patients (mean arterial pressure < 65 mmH) received a fluid challenge with hydroxyethyl starch. Patients were excluded if they had active bleeding and/or required changes in vasoactive agents infusion rate in the previous 30 minutes. Responders were defined by the increase of mean arterial pressure value to over 65 mmHg or by more than 20% with respect to the value recorded before fluid challenge. Measurements were performed before and at one hour after the end of fluid challenge.Twenty-two patients (61%) increased arterial pressure after volume expansion. Baseline heart rate, arterial pressure, central venous pressure, central venous saturation, central venous to arterial PCO2 difference, lactate, urinary output, fractional excretion of sodium and urinary sodium/potassium ratio were similar between responder and non-responder. Only 7 out of 36 patients had valuable dynamic indices and then we excluded them from analysis. When the variables were tested as predictors of responders, they showed values of areas under the ROC curve ranging between 0.502 and 0.604. Logistic regression did not reveal any association between variables and responder definition.Fluid challenge did not improve arterial pressure in about one third of hypotensive critically ill patients. Cardiovascular and renal variables did not enable us to predict the individual response to volume administration.ClinicalTrials.gov: NCT00721604.Fluid administration is the first recommended approach to increase arterial blood pressure in critically ill hypotensive patients [1-3]. If early aggressive fluid resuscitation is useful at the beginning of care in injured and septic patients [3,4], there is evidence that unnecessary fluid administration and positive fluid balance increase mortality, organ dysfunction and Intensive Care Unit length of stay when the whole period of care is considered [5-8]. To avoid fluid overload it is important to identify beforehand the patients for whom volume