Our goal was to study the feasibility of predicting fluid responsiveness by transcutaneous partial pressure of oxygen (PtcO2) in the critically ill patients.

The clinical determination of the intravascular volume can be extremely difficult in critically ill patients. Although hemodynamic maximization was proposed, this approach was associated with a risk of fluid overload and excessive inotropic support. Therefore, fluid optimization was seen as a significant step forward and has been shown to decrease complications. Significant effort has been devoted to defining and developing simple means for predicting fluid responsiveness, i.e. whether the patient will benefit from fluid administration. Passive leg raising (PLR), a bedside performed test, could be used to accurately predict fluid responsiveness in most conditions.

However, most parameters that provide information about fluid responsiveness during volume expansion and PLR are invasive and time-consuming. A completely noninvasive and atraumatic parameter to predict fluid responsiveness might be need urgently. Transcutaneous partial pressure of oxygen (PtcO2), a measure to detect tissue ischemia or inadequate perfusion, might reflect the change in cardiac output, thus predict fluid responsiveness. The purpose of this study was to study the feasibility of predicting fluid responsiveness by transcutaneous partial pressure of oxygen in the critically ill patients.

Inclusion Criteria:

• clinical signs of inadequate tissue perfusion defined as systolic blood pressure < 90 mm Hg or a decrease > 40 mmHg in previously hypertensive patients or the need for vasopressive drugs (dopamine > 5 ug/kg/min or norepinephrine); urine output < 0.5 ml/kg/hr for 2 hrs; tachycardia; presence of skin mottling.

Exclusion Criteria:

• pregnancy, age of less than 18 years, contraindication to passive leg raising test, cardiac arrhythmias, cardiogenic pulmonary edema, the presence of abdominal compartment syndrome and refusal to participate in the study

Patients for whom the attending physician decided to perform a fluid challenge or presence of at least one clinical sign of inadequate tissue perfusion in the absence of contraindication for fluid infusion for less than 24 hours were eligible to participate in the study.