Fluid Responsiveness in the Postoperative Period: a Prospective Study in Non–critically Ill Patients


Background:The incidence Fluid Responsiveness (FR) in non-critically ill surgical patients and the proportion of patients in whom Stroke Volume (SV) significantly increases after a bolus of intravenous fluids (Volume Expansion, VE) are unknown after surgery. Although being Fluid Responder (FRer) does not necessarily imply being hypovolemic, it remains to be determined whether postoperative FR is associated with complications. The aims of this prospective study are to determine 1) the incidence of FR in non-critically ill surgical patients after major surgeries, 2) if postoperative FR predicts and is associated with complications, 3) the proportion of patients in whom SV significantly increases after VE.
Methods:Ethic approval:14-452-SDR; clinicaltrial.org registration:NCT02418663. Adult patients undergoing major thoracic or abdominal surgery, not requiring intensive care unit admission, and treated with a surgery-specific Enhanced Recovery Program were enrolled. FR was assessed soon after surgery, and daily for the first 72 h. SV was measured with the ccNexfin® before and 1 min after a fluid challenge (FC) with 250 ml of Lactated Ringer’s in 5 min. FR was also assessed “on call” when VE was clinically deemed. A patient was considered fluid responder (FRer) if SV increased ≥ 15% either 1 min after the FC or 1 min after VE, at least 1 time within 72 h. Treating physicians were blind to all SV measurements. 
Results:FR after a FC was present in 32 over 88 patients (36.4%). Complications occurred in 46.9% of FRer and in 39.3% of non-FRer (Relative Risk, RRcrude= 1.19, 95% Confidence Interval, CI=0.73 to 1.95, p-value=0.488; RRadjusted= 1.04, 95%CI=0.58 to 1.90, p-value=0.692). After controlling for confounders (age, type of surgery, blood loss, intraoperative volume of intravenous fluids, postoperative negative fluid balance) FR was not an independent predictor of complications (Odds Ratio, ORcrude =2.02 95%CI=0.82 to 4.97, p-value=0.124; ORadjusted=0.61 95%CI=0.22 to 1.72, p-value=0.352). VE was clinically required in 7 patients (7.9%). Of these, only 1 patient (14.3%) was FRer.
Conclusions:These preliminary results suggest that 36.4% of non-critically ill surgical patients are FRer after surgery. After controlling for confounders FR does not predict and is not associated with complications. Finally, fluid boluses administered based on clinical signs of hypovolemia rarely determine a significant increase of SV and might be potentially harmful.

Fluid responsiveness in the postoperative period: a prospective study in non critically-ill patients