Bioimpedance Spectroscopy for Assessment of Volume Status in Patients before and after General Anaesthesia

Abstract

BackgroundTechnically assisted assessment of volume status before surgery may be useful to direct intraoperative fluid administration. We therefore tested a recently developed whole-body bioimpedance spectroscopy device to determine pre- to postoperative fluid distribution.MethodsUsing a three-compartment physiologic tissue model, the body composition monitor (BCM, Fresenius Medical Care, Germany) measures total body fluid volume, extracellular volume, intracellular volume and fluid overload as surplus or deficit of ‘normal’ extracellular volume. BCM-measurements were performed before and after standardized general anaesthesia for gynaecological procedures (laparotomies, laparoscopies and vaginal surgeries). BCM results were blinded to the attending anaesthesiologist and data analysed using the 2-sided, paired Student’s t-test and multiple linear regression.ResultsIn 71 females aged 45±15 years with body weight 67±13 kg and duration of anaesthesia 154±68 min, pre- to postoperative fluid overload increased from −0.7±1.1 L to 0.1±1.0 L, corresponding to −5.1±7.5% and 0.8±6.7% of normal extracellular volume, respectively (both p<0.001), after patients had received 1.9±0.9 L intravenous crystalloid fluid. Perioperative urinary excretion was 0.4±0.3 L. The increase in extracellular volume was paralleled by an increase in total body fluid volume, while intracellular volume increased only slightly and without reaching statistical significance (p = 0.15). Net perioperative fluid balance (administered fluid volume minus urinary excretion) was significantly associated with change in extracellular volume (r2 = 0.65), but was not associated with change in intracellular volume (r2 = 0.01).ConclusionsRoutine intraoperative fluid administration results in a significant, and clinically meaningful increase in the extracellular compartment. BCM-measurements yielded plausible results and may become useful to guide intraoperative fluid therapy in future studies.

The effect of crystalloid infusion on body water content and intra-abdominal pressure in patients undergoing orthopedic surgery under spinal anesthesia

“…Liberal crystalloid infusion also increased ECW by more than restrictive infusion. An increase in ECW following intraoperative fluid infusion has also been observed by Ernstbrunner et al 5 They observed a strong correlation between the net perioperative fluid balance and a change in ECW in patients undergoing elective gynecological surgery under general anesthesia. This increase in ECW corresponded to TBW, but the authors proposed net perioperative fluid balance and postoperative capillary leak index as significant individual predictors for changes in ECW.…”

“…30 Other authors have proposed BIA as a sensitive and easy method for measuring perioperative fluid administration in patients undergoing elective surgery. 5 We have also documented the usefulness of BIA in perioperative clinical practice, though we placed the electrodes on the body side opposite to the surgery. Surgery-related tissue edema and wound hematoma may have significantly disturbed the final results of BIA measurement.…”

“…3,4 Several studies have documented significant benefits resulting from BIA-controlled fluid balance. 3,5,6 Unfortunately, only 1 study has analysed the effect of perioperative fluid therapy on body water distribution in patients undergoing various elective gynecological procedures under general anesthesia. 6 In addition, the effect of crystalloid therapy has not been documented in conscious spinal-anesthetized patients.…”

The Use of Technology for Estimating Body Composition

“…In addition, the noninvasive nature of bioimpedance makes it particularly well suited for measuring longitudinal changes. Notably, BIS techniques have recently shown promise in assessing body composition and mortality risk in people on dialysis 81 and in managing fluid status in dialysis 88 – 93 as well as surgery 92 and critically illness 91 …”

Bio-electrical impedance analysis for perioperative fluid evaluation in open major abdominal surgery

“…The cut-off BIA values used for defining normal-, over-and dehydrated patients were as for patients undergoing chronic dialysis. These values have also been used by other authors with regard to perioperative patient assessment [39]. The mean postoperative TBW and ECW increased significantly, and so did the ECW/ICW ratio from preoperative 0.85 to postoperative 0.93.…”