Mini-fluid challenge predicts fluid responsiveness during spontaneous breathing under spinal anaesthesia: An observational study.

Abstract

The ability to predict fluid responsiveness in spontaneously breathing patients under spinal anaesthesia is desirable. The objective of this study was to test whether variations in stroke volume (SV) in response to a fixed mini-fluid challenge (ΔSV100) measured by thoracic impedance cardiography (ICG) can predict fluid responsiveness in spontaneously breathing patients under spinal anaesthesia. A prospective observational study. Anaesthesiology department in a university hospital. Seventy-three patients monitored by ICG during surgery under spinal anaesthesia. Patients received a 100 ml fluid challenge followed by volume expansion with 500 ml of crystalloid. Haemodynamic variables and bioimpedance indices [blood pressure, SV, cardiac output (CO)] were measured before and after fluid challenge and before and after volume expansion. Responders were defined as those with >15% increase in SV after volume expansion. SV increased by at least 15% in 27 (37%) of the 73 patients. ΔSV100 predicted fluid responsiveness with an area under the receiver operating characteristic (AUC) curve of 0.93 [95% confidence interval (95% CI) 0.8 to 0.97, P < 0.001]. The cut-off was 7% and a grey zone ranging between 3 and 8% was observed in up to 14% of patients. SV baseline was a poor predictor of fluid responsiveness [AUC of 0.69 (95% CI 0.57 to 0.79, P = 0.002)]. ΔSV100 greater than 7% accurately predicted fluid responsiveness during surgery with a grey zone ranging between 3 and 8%.