Comparison of predicted and real propofol and remifentanil concentrations in plasma and brain tissue during target‐controlled infusion: a prospective observational study

Opioid use in treated and untreated obstructive sleep apnoea: remifentanil pharmacokinetics and pharmacodynamics in adult volunteers

BACKGROUND

Patients with obstructive sleep apnoea (OSA) are considered more sensitive to opioids and at increased risk of opioid-induced respiratory depression. Nonetheless, whether OSA treatment (continuous positive airway pressure, CPAP; or bilevel positive airway pressure, BIPAP) modifies this risk remains unknown. Greater opioid sensitivity can arise from altered pharmacokinetics or pharmacodynamics. This preplanned analysis of a previous cohort study of remifentanil clinical effects in OSA tested the null hypothesis that the pharmacokinetics, pharmacodynamics, or both of remifentanil, a representative μ-opioid agonist, are not altered in adults with treated or untreated OSA.

METHODS

A single-centre, prospective, open-label, cohort study administered a stepped-dose, target-controlled remifentanil infusion (target effect-site concentrations 0.5, 1, 2, 3, 4 ng ml-1) to awake adult volunteers (median age 52 yr, range 23-70) without OSA (n=20), with untreated OSA (n=33), or with treated OSA (n=21). Type III (in-home) polysomnography verified OSA. Remifentanil plasma concentrations, end-expired CO2, thermal heat tolerance, and pupil diameter (miosis) were assessed. Population pharmacokinetic (clearance, volume of distribution) and pharmacodynamic (miosis, thermal heat tolerance, end-expired CO2) models were developed.

RESULTS

Remifentanil clearance (median) was 147, 143, and 155 L h-1 (P=0.472), and volume of distribution was 19.6, 15.5, and 17.7 L (P=0.473) for subjects without OSA, untreated OSA, or treated OSA, respectively. Total body weight was an influential covariate on both remifentanil clearance and central volume of distribution. There were no statistically or clinically significant differences between the three groups in miosis EC50 or Emax, or the slopes of thermal heat tolerance or end-expired CO2vs remifentanil concentration. At a plasma remifentanil concentration of 4 ng ml-1, in participants without OSA, with untreated OSA, or with treated OSA, respectively, model-estimated pupil area (12%, 13%, and 17% of baseline, P=0.086), thermal heat tolerance (50°C, 51°C, and 51°C, P=0.218), and end-expired CO2 (6.3 kPa, 6.4 kPa, and 6.7 kPa, P=0.257) were not statistically different between groups.

CONCLUSIONS

OSA (untreated or treated) did not influence remifentanil pharmacokinetics or pharmacodynamics (miosis, analgesia, respiratory depression). Results support the null hypothesis that neither pharmacokinetics nor pharmacodynamics of remifentanil, a representative μ-opioid, are altered in adults with treated or untreated OSA. These findings provide a mechanistic explanation for the lack of influence of OSA or OSA treatment on the clinical miotic, sedative, analgesic, or respiratory depressant response to remifentanil in awake adults. The conventional notion that OSA alters sensitivity to the effects of opioids in awake adults is not supported by our findings, such that opioid dosing might not need adjustment for pharmacokinetic or pharmacodynamic considerations.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT02898792, https://clinicaltrials.gov/ct2/show/NCT02898792. First Posted: September 13, 2016.

ICU patient-on-a-chip emulating orchestration of mast cells and cerebral organoids in neuroinflammation

Propofol and midazolam are the current standard of care for prolonged sedation in Intensive Care Units (ICUs). However, the effects and mechanism of these sedatives in brain tissue are unclear. Herein, the development of an ICU patient-on-a-chip platform to elucidate those effects is reported. The humanized neural tissue compartment combines mast cells differentiated from human induced pluripotent stem cells (hiPSCs) with cerebral organoids in a three-dimensional (3D) matrix, which is covered with a membrane populated with human cerebral microvascular endothelial cells (hCMEC/D3) that separates the tissue chamber from the vascular lumen, where sedatives were infused for four days to evaluate neurotoxicity and cell-mediated immune responses. Subsequent to propofol administration, gene expressions of CD40 and TNF-α in mast cells, AIF1 in microglia and GFAP/S100B/OLIG2/MBP in macroglia were elevated, as well as NOS2, CD80, CD40, CD68, IL6 and TNF-α mediated proinflammation is noted in cerebral organoids, which resulted in higher expressions of GJB1, GABA-A and NMDAR1 in the tissue construct of the platform. Besides, midazolam administration stimulated expression of CD40 and CD203c+ reactivated mast cell proliferation and compromised BBB permeability and decreased TEER values with higher barrier disruption, whereas increased populations of CD11b+ microglia, higher expressions of GFAP/DLG4/GJB1 and GABA-A-/NMDAR1- identities, as well as glutamate related neurotoxicity and IL1B, IFNG, IFNA1, IL6 genes mediated proinflammation, resulting in increased apoptotic zones are observed in cerebral organoids. These results suggest that different sedatives cause variations in cell type activation that modulate different pathways related to neuroinflammation and neurotoxicity in the ICU patient-on-chip platform.

Determination of remifentanil in neonatal dried blood spots by liquid chromatography-tandem mass spectrometry

Remifentanil is an ultra-short-acting synthetic opioid-class analgesic which might be increasingly used "off-label" as pain management during labour. Side effects in parturients during labour, and in the infant at birth are of particular concern, especially respiratory depression which is concentration-dependent, and can occur at levels as low as 3-5 ng mL-1. The safety of such use, particularly in newborns due to remifentanil placental transfer, has not been fully demonstrated yet, partly due to the lack of a suitable non-invasive analytical method. The aim of our work was to develop a sensitive method to monitor the levels of remifentanil in neonates by a non-invasive sampling of umbi lical cord blood to support efficacy and safety trials. The presented LC-MS method is sensitive enough to reliably quantify remifentanil in just 20 µL of blood at only 0.3 ng mL-1. The dried blood spot sample preparation included solvent extraction with subsequent solid-phase extraction. The method was validated in terms of accuracy, precision, recovery, matrix effect, and stability, and was successfully applied to a small pilot study. The estimated arterial blood concentrations at the time of delivery ranged from 0.2 to 0.3, and up to 0.9 ng mL-1 in neonatal, and maternal samples, respectively.

Development of extended pharmacokinetic models for propofol based on measured blood and brain concentrations

Propofol's pharmacokinetics have been extensively studied using human blood samples and applied to target-controlled infusion systems; however, information on its concentration in the brain remains scarce. Therefore, this study aimed to simultaneously measure propofol plasma and brain concentrations in patients who underwent awake craniotomy and establish new pharmacokinetic model. Fifty-seven patients with brain tumors or brain lesions who underwent awake craniotomy were sequentially assigned to model-building and validating groups. Plasma and brain (lobectomy or uncapping margins) samples were collected at five time-points. The concentration of propofol was measured using high-performance liquid chromatography. Population pharmacokinetic analysis was conducted through a nonlinear mixed-effects modeling program using a first-order conditional estimation method with interactions. Propofol's brain concentrations were higher than its plasma concentrations. The measured brain concentrations were higher than the effect site concentrations using the previous models. Extended models were constructed based on measured concentrations by incorporating the brain/plasma partition coefficient (Kp value). Extended models showed good predictive accuracy for brain concentrations in the validating group. The Kp value functioned as a factor explaining retention in the brain. Our new pharmacokinetic models and Kp value can predict propofol's brain and plasma concentrations, contributing to safer and more stable anesthesia.

Direct visualization of general anesthetic propofol on neurons by stimulated Raman scattering microscopy

The consensus for the precise mechanism of action of general anesthetics is through allosteric interactions with GABA receptors in neurons. However, it has been speculated that these anesthetics may also interact with the plasma membrane on some level. Owing to the small size of anesthetics, direct visualization of these interactions is difficult to achieve. We demonstrate the ability to directly visualize a deuterated analog of propofol in living cells using stimulated Raman scattering (SRS) microscopy. Our findings support the theory that propofol is highly concentrated and interacts primarily through non-specific binding to the plasma membrane of neurons. Additionally, we show that SRS microscopy can be used to monitor the dynamics of propofol binding using real-time, live-cell imaging. The strategy used to visualize propofol can be applied to other small molecule drugs that have been previously invisible to traditional imaging techniques

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Multi-modal SRS developed for real-time biological imaging of small molecule substances

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Propofol primarily concentrates at the cell membrane of neurons

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Anesthesia dynamics can be monitored in real-time with SRS

Efficacy and safety of remimazolam besylate versus propofol during hysteroscopy: single-centre randomized controlled trial

Background

Remimazolam besylate is a newer benzodiazepine with characteristics of quick onset of effects, short maintenance and recovery times without accumulation in tissues. This trial was conducted to confirm the efficacy and safety of remimazolam besylate versus propofol during hysteroscopy.

Methods

Patients undergoing hysteroscopy were randomly assigned to either the remimazolam (Group R) or the propofol group (Group P). Group R was administered an induction dose of 0.2 mg/kg and a maintenance dosage of 1.0 mg/kg/h. In Group P, propofol was started at 1.5–2.0 mg/kg and then maintained at 3.0–6.0 mg/kg/h. After remimazolam besylate or propofol induction, remifentanil was infused using a target-controlled infusion system with a target concentration of 1.5 ng/ml and titrated during the procedure. The incidence rates of injection pain, low oxygen saturation (SpO₂) and adverse effects in both groups were compared.

Results

Eighty-two patients were included in this study. The incidence of adverse events in Group R (3.7%) was significantly lower than that in Group P (36.6%) (p < 0.001). The incidence of injection pain in Group P (80.5%) was much higher than that in Group R (2.4%) (p < 0.001). The incidence of other adverse events, such as low SpO₂, bradycardia, and hypotension in Group R was lower than that in Group P (p < 0.05).

Conclusions

Remimazolam besylate proves to be a safer alternative for anesthesia during hysteroscopy. Moreover, adverse events caused by propofol, such as low SpO₂ and injection pain, are largely avoided.

Trial registration

This study was approved by the Clinical Research Ethics Committee of Mengcheng County No. 1 People’s Hospital (2020MYL20003) and registered at http://www.chictr.org.cn (15/09/2020, ChiCTR-2000038252). The study protocol followed the CONSORT guidelines. The study protocol was performed in the relevant guidelines.