Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway.
Department of Anaesthesiology, Division of Critical Care, Oslo University Hospital, Oslo, Norway.
Acta Anaesthesiol Scand. 2022 May;66(5):598-605. doi: 10.1111/aas.14043. Epub 2022 Feb 19.
Ion mobility spectrometry (IMS) allows for online quantification of exhaled propofol concentrations. We aimed to validate a bedside online IMS device, the Edmon , for predicting plasma concentrations of propofol in normal-weight and obese patients.
Patients with body mass index (BMI) >20 kg/m scheduled for laparoscopic cholecystectomy or bariatric surgery were recruited. Exhaled propofol concentrations (C ), arterial plasma propofol concentrations (C ) and bispectral index (BIS) values were collected during target-controlled infusion (TCI) anaesthesia. Generalised estimation equation (GEE) was applied to all samples and stable-phase samples at different delays for best fit between C and C . BMI was evaluated as covariate. BIS and exhaled propofol correlations were also assessed with GEE.
A total of 29 patients (BMI 20.3-53.7) were included. A maximal R of 0.58 was found during stable concentrations with 5 min delay of C to C ; the intercept a = -0.69 (95% CI -1.7, 0.3) and slope b = 0.87 (95% CI 0.7, 1.1). BMI was found to be a non-significant covariate. The median absolute performance error predicting plasma propofol concentrations was 13.4%. At a C of 5 ppb, the model predicts a C of 3.6 μg/ml (95% CI ±1.4). There was a maximal negative correlation of R = 0.44 at 2-min delay from C to BIS.
Online monitoring of exhaled propofol concentrations is clinically feasible in normal-weight and obese patients. With a 5-min delay, our model outperforms the Marsh plasma TCI model in a post hoc analysis. Modest correlation with plasma concentrations makes the clinical usefulness questionable.
离子迁移谱（IMS）可实现呼出丙泊酚浓度的在线定量。我们旨在验证一种床边在线 IMS 设备 Edmon ，以预测正常体重和肥胖患者的血浆丙泊酚浓度。
招募 BMI>20kg/m2 的接受腹腔镜胆囊切除术或减肥手术的患者。在靶控输注（TCI）麻醉期间收集呼出丙泊酚浓度（C）、动脉血浆丙泊酚浓度（C）和脑电双频指数（BIS）值。使用广义估计方程（GEE）对所有样本和不同延迟的稳定相样本进行拟合，以确定 C 和 C 之间的最佳拟合。评估 BMI 作为协变量。还使用 GEE 评估 BIS 和呼出丙泊酚之间的相关性。
共纳入 29 例患者（BMI 20.3-53.7）。在稳定浓度时，C 与 C 之间延迟 5 分钟时发现最大 R 为 0.58；截距 a=-0.69（95%CI -1.7, 0.3），斜率 b=0.87（95%CI 0.7, 1.1）。BMI 被发现是非显著的协变量。预测血浆丙泊酚浓度的中位数绝对性能误差为 13.4%。在 C 为 5ppb 时，该模型预测 C 为 3.6μg/ml（95%CI ±1.4）。在 C 与 BIS 之间延迟 2 分钟时，相关性最大，R 为 0.44。
在正常体重和肥胖患者中，呼出丙泊酚浓度的在线监测在临床上是可行的。在 5 分钟的延迟后，我们的模型在事后分析中优于 Marsh 血浆 TCI 模型。与血浆浓度的适度相关性使得其临床应用值得怀疑。
