Background: Mean arterial pressure above 65 mmHg is recommended for critically ill hypotensive patients\r\nwhereas they do not benefit from supranormal cardiac output values. In this study we investigated if the increase\r\nof mean arterial pressure after volume expansion could be predicted by cardiovascular and renal variables. This is a\r\nrelevant topic because unnecessary positive fluid balance increases mortality, organ dysfunction and Intensive Care\r\nUnit length of stay.\r\nMethods: Thirty-six hypotensive patients (mean arterial pressure < 65 mmH) received a fluid challenge with\r\nhydroxyethyl starch. Patients were excluded if they had active bleeding and/or required changes in vasoactive\r\nagents infusion rate in the previous 30 minutes. Responders were defined by the increase of mean arterial pressure\r\nvalue to over 65 mmHg or by more than 20% with respect to the value recorded before fluid challenge.\r\nMeasurements were performed before and at one hour after the end of fluid challenge.\r\nResults: Twenty-two patients (61%) increased arterial pressure after volume expansion. Baseline heart rate, arterial\r\npressure, central venous pressure, central venous saturation, central venous to arterial PCO2 difference, lactate,\r\nurinary output, fractional excretion of sodium and urinary sodium/potassium ratio were similar between responder\r\nand non-responder. Only 7 out of 36 patients had valuable dynamic indices and then we excluded them from\r\nanalysis. When the variables were tested as predictors of responders, they showed values of areas under the ROC\r\ncurve ranging between 0.502 and 0.604. Logistic regression did not reveal any association between variables and\r\nresponder definition.\r\nConclusions: Fluid challenge did not improve arterial pressure in about one third of hypotensive critically ill\r\npatients. Cardiovascular and renal variables did not enable us to predict the individual response to volume\r\nadministration.
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