Correlations between preoperative fluid status assessed by bioimpedance analysis and hypotension during anaesthesia induction.

Introduction: Hypovolaemia is presumed to be a common risk factor of postinduction hypotension (PIH), despite worldwide improvement in preoperative volume optimization. Correct assessment of fluid status in patients undergoing general anaesthesia remains a major challenge for anaesthesiologists. Bioimpedance analysis (BIA) is a sensitive method that allows objective assessment of patient fluid status as it can detect subclinical changes. The study's main purpose was to determine the correlation between the preoperative BIA assessed fluid status and PIH.

Material and methods: This was an observational single centre study that included patients undergoing elective surgery. We defined PIH as the blood pressure decrease occurring during the first 10 minutes after induction of anaesthesia and orotracheal intubation before surgical incision. We standardized BIA evaluation, patient pre anaesthetic and preoperative preparation, technique and monitoring of anaesthesia.

Results: Our study included 115 patients. The mean age of the population was 58.1 years and the median values for total and intracellular water were 35.1 L and 19.3 L, respectively. In the univariable and multivariable analysis, only total body and intracellular water were associated with different definitions of PIH. There was no correlation between any of the BIA-derived parameters of fluid status and the duration of PIH.

Conclusions: Our study shows that in elective surgery, bioimpedance could detect subtle, subclinical fluid parameters that are associated with PIH.