Using Electrical Bioimpedance Assessments to Estimate Perioperative Total Body Water and Postoperative Fluid Need

Being able to accurately monitor patient bodily fluid levels during and after surgery is very important, as there are a number of complications that can arise if a patient’s fluid levels become unbalanced, such as swelling within or pressure on various bodily organ systems. There are several different ways that physicians can monitor a patient’s fluid balance during and after surgery, such as measuring the amount of urine output or the use of central venous catheters which measure the pressure in the veins entering the heart. Most of these techniques are invasive since they require tubes to be inserted into the body. A potential alternative would be to use a noninvasive technique such as electrical bioimpedance (BIA).
Bioimpedance assessments work by using small electrical currents that can accurately predict both the water surrounding the outside of cells in the body, as well as the total amount of water in the entire body. Electrical bioimpedance assessments have been used to estimate patient swelling following surgery (edema), to measure the volume of blood the heart is pumping out, as well as to calculate body fat percentages.
The goal of this study is to relate this technology to fluid shifts within the body that occur as a result of surgery, in particular, major intra-abdominal surgeries. By using bioimpedance during and after surgery, the investigators will compare the data collected with that calculated by using traditional measures of body fluid status, such as urine output and intraoperative blood loss. During the study, the bioimpedance monitors will not replace the standard bodily fluid monitors and will not interfere with their readings. Additionally, the electrical current produced by the bioimpedance monitors is too small for patients to feel and will not interfere with medical devices such as pacemakers.

在手术全程及术后精准监测患者体液水平至关重要，若患者体液失衡，则可能引发多种并发症，包括体内组织肿胀或多脏器系统受压。临床医师可通过多种方式监测患者术中及术后的体液平衡，例如检测尿量，或使用中心静脉导管（central venous catheter）测量入心脏静脉压力。此类监测技术大多属于有创操作，需将管路植入患者体内。一种潜在的无创替代方案为生物电阻抗分析法（electrical bioimpedance, BIA）。
生物电阻抗评估通过施加微小电流实现，可精准检测机体细胞外液量与全身总水量。该技术已被用于估算术后患者的水肿（edema）、测量心脏每搏输出量，以及计算体脂百分比。
本研究旨在将该技术与手术（尤其是腹部大手术）引发的机体体液移位相关联。研究人员将在手术全程及术后采用生物电阻抗监测，将采集的数据与传统体液状态检测方法（如尿量、术中失血量）的计算结果进行对比。本研究中，生物电阻抗监测仪不会替代标准体液监测设备，亦不会干扰其读数。此外，该监测仪产生的电流极其微弱，患者无法感知，且不会对心脏起搏器等医疗设备造成干扰。