Evaluating Propofol Concentration in Blood From Exhaled Gas Using a Breathing-Related Partition Coefficient. (April 2020)

• Record Type: Journal Article
• Authors: Dong, Hao; Zhang, Fengjiang; Chen, Jing; Yu, Qiwen; Zhong, Yinbo; Liu, Jun; Yan, Min; Chen, Xing
• Is Part Of: Anesthesia & analgesia. Volume 130:Number 4(2020)
• Publication Date: 2020-04
• Subjects: Anesthesiology -- Periodicals; Anesthesia; Anesthesiology; Analgesia; Analgesics; Anesthesiology -- Periodicals; 617.9605
• DOI: 10.1213/ANE.0000000000004225
• Languages: English
• ISSNs: 0003-2999

Abstract

Abstract : BACKGROUND: The anesthetic side effects of propofol still occur in clinical practice because no reliable monitoring techniques are available. In this regard, continuous monitoring of propofol in breath is a promising method, yet it remains infeasible because there is large variation in the blood/exhaled gas partial pressure ratio (RBE ) in humans. Further evaluations of the influences of breathing-related factors on RBE would mitigate this variation. METHODS: Correlations were analyzed between breathing-related factors (tidal volume [TV], breath frequency [BF], and minute ventilation [VM ]) and RBE in 46 patients. Furthermore, a subset of 10 patients underwent pulmonary function tests (PFTs), and the parameters of the PFTs were then compared with the RBE . We employed a 1-phase exponential decay model to characterize the influence of VM on RBE . We also proposed a modified RBE (RBEM ) that was not affected by the different breathing patterns of the patients. The blood concentration of propofol was predicted from breath monitoring using RBEM and RBE . RESULTS: We found a significant negative correlation ( R = −0.572; P < .001) between VM and RBE (N = 46). No significant correlation was shown between PFTs and RBE in the subset (N = 10). RBEM demonstrated a standard Gaussian distribution (mean, 1.000; standard deviation [SD], 0.308). Moreover, the predicted propofol concentrations based on breath monitoring matched well with the measured blood concentrations. The 90% prediction band was limited to within ±1 μg·mL −1 . CONCLUSIONS: The prediction of propofol concentration in blood was more accurate using RBEM than when using RBE and could provide reference information for anesthesiologists. Moreover, the present study provided a general approach for assessing the influence of relevant physiological factors and will inform noninvasive and accurate breath assessment of volatile drugs or metabolites in blood.