Study protocol: Cerebral characterization of sensory gating in disconnected dreaming states during propofol anesthesia using fMRI

Background

Disconnected consciousness describes a state in which subjective experience (i.e., consciousness) becomes isolated from the external world. It appears frequently during sleep or sedation, when subjective experiences remain vivid but are unaffected by external stimuli. Traditional methods of differentiating connected and disconnected consciousness, such as relying on behavioral responsiveness or on post-anesthesia reports, have demonstrated limited accuracy: unresponsiveness has been shown to not necessarily equate to unconsciousness and amnesic effects of anesthesia and sleep can impair explicit recollection of events occurred during sleep/sedation. Due to these methodological challenges, our understanding of the neural mechanisms underlying sensory disconnection remains limited.

Methods

To overcome these methodological challenges, we employ a distinctive strategy by combining a serial awakening paradigm with auditory stimulation during mild propofol sedation. While under sedation, participants are systematically exposed to auditory stimuli and questioned about their subjective experience (to assess consciousness) and their awareness of the sounds (to evaluate connectedness/disconnectedness from the environment). The data collected through interviews are used to categorize participants into connected and disconnected consciousness states. This method circumvents the requirement for responsiveness in assessing consciousness and mitigates amnesic effects of anesthesia as participants are questioned while still under sedation. Functional MRI data are concurrently collected to investigate cerebral activity patterns during connected and disconnected states, to elucidate sensory disconnection neural gating mechanisms. We examine whether this gating mechanism resides at the thalamic level or results from disruptions in information propagation to higher cortices. Furthermore, we explore the potential role of slow-wave activity (SWA) in inducing disconnected consciousness by quantifying high-frequency BOLD oscillations, a known correlate of slow-wave activity.

Discussion

This study represents a notable advancement in the investigation of sensory disconnection. The serial awakening paradigm effectively mitigates amnesic effects by collecting reports immediately after regaining responsiveness, while still under sedation. Ultimately, this research holds the potential to understand how sensory gating is achieved at the neural level. These biomarkers might be relevant for the development of sensitive anesthesia monitoring to avoid intraoperative connected consciousness and for the assessment of patients suffering from pathologically reduced consciousness.

Clinical trial registration

European Union Drug Regulating Authorities Clinical Trials Database (EudraCT), identifier 2020-003524-17.

To ascertain the plasma concentration of propofol to achieve bispectral index-guided sedation using a target-controlled infusion in patients undergoing elective surgeries under neuraxial anaesthesia

Background and Aims

Sedation improves patient satisfaction, comfort and acceptance of regional anaesthesia. Propofol using bispectral index (BIS)/target-controlled infusion (TCI) system can be an optimal method of sedation, as it combines objective measurement of sedation using BIS along with maintenance of a steady plasma concentration of propofol with the TCI device. The aim of this study was to ascertain the dose and safety of propofol using BIS/TCI system for sedation in patients undergoing surgeries under neuraxial anaesthesia.

Methods

One hundred and seven adult patients, undergoing elective surgical procedures under spinal or combined spinal epidural anaesthesia, were recruited. Propofol infusion was started with TCI at an initial target plasma concentration (Cpt) of 1.2 μg/mL, and after equilibration between Cpt and effect site concentration (Ce), propofol was then adjusted in increments and/or decrements of 0.2 μg/mL in order to maintain a BIS value between 60 and 80. The average time to reach BIS = 80 after starting infusion was 7.32 ± 3.13 minutes. The objective was to calculate mean Cpt value maintaining BIS between 60 and 80 and to observe recovery time and complications.

Results

Mean Cpt value was 1.13 ± 0.17 mg/mL with 95% confidence interval (1.10-1.16 μg/mL). In 85% of patients, a BIS value of 60-80 was maintained at Cpt ≤ 1.2 μg/mL. No patient had severe complications requiring stoppage of infusion.

Conclusion

Propofol sedation using BIS/TCI system can provide safe and convenient sedation during neuraxial anaesthesia at very low plasma concentration, Cpt ≤ 1.2 μg/mL in majority of patients. There were no periprocedural complications, and recovery was rapid.

Propofol sedation without endotracheal intubation is safe for endoscopic submucosal dissection in the esophagus and stomach

Background

Endoscopic submucosal dissection (ESD) for early esophageal and stomach cancer is usually performed under general anesthesia. However, propofol sedation without endotracheal intubation has been suggested as a viable alternative.

Objective

The objective of this study was to evaluate the safety of propofol sedation without endotracheal intubation during ESD in the upper gastrointestinal tract.

Methods

We performed a retrospective cohort study of patients who underwent ESD for upper gastrointestinal tumors with propofol-remifentanil analgosedation in a tertiary referral center in the Netherlands between October 2013 and February 2018. Primary endpoints were the rates of intraprocedural endoscopy- and anesthesia-related complications. Secondary endpoints were the postprocedural complication rates within 30 days and endotracheal intubation conversion rates.

Results

Of 88 patients, intraprocedural ESD-related complications occurred in three patients (3.4%). Intraprocedural anesthesia-related complications occurred in two patients (2.3%), one of whom required conversion to endotracheal intubation. Postprocedural ESD-related complications occurred in 14 patients (15.9%), and minor postprocedural complications occurred in two patients (2.3%). Eighty-two (93.2%) patients were discharged within one day after ESD. No patient was readmitted for anesthesia-related complications.

Conclusion

Propofol-based sedation without endotracheal intubation is safe for ESD procedures in the esophagus and stomach with low anesthesia-related complication rates and short hospital stay.

Fine-Grained Parcellation of Brain Connectivity Improves Differentiation of States of Consciousness During Graded Propofol Sedation

Conscious perception relies on interactions between spatially and functionally distinct modules of the brain at various spatiotemporal scales. These interactions are altered by anesthesia, an intervention that leads to fading consciousness. Relatively little is known about brain functional connectivity and its anesthetic modulation at a fine spatial scale. Here, we used functional imaging to examine propofol-induced changes in functional connectivity in brain networks defined at a fine-grained parcellation based on a combination of anatomical and functional features. Fifteen healthy volunteers underwent resting-state functional imaging in wakeful baseline, mild sedation, deep sedation, and recovery of consciousness. Compared with wakeful baseline, propofol produced widespread, dose-dependent functional connectivity changes that scaled with the extent to which consciousness was altered. The dominant changes in connectivity were associated with the frontal lobes. By examining node pairs that demonstrated a trend of functional connectivity change between wakefulness and deep sedation, quadratic discriminant analysis differentiated the states of consciousness in individual participants more accurately at a fine-grained parcellation (e.g., 2000 nodes) than at a coarse-grained parcellation (e.g., 116 anatomical nodes). Our study suggests that defining brain networks at a high granularity may provide a superior imaging-based distinction of the graded effect of anesthesia on consciousness.

Propofol sedation during gastrointestinal endoscopy arouses euphoria in a large subset of patients

Background

Propofol is recommended for sedation in gastrointestinal endoscopy (GE), but preliminary data suggest addictive potentials.

Objective

The objective of this article is to evaluate the frequency of predominantly euphoric reaction after GE and patients' subsequent reminiscences.

Methods

Eighty-two patients undergoing elective GE under propofol sedation were enrolled in a prospective observational study. The grade of anxiety, expectation or relief about the examination's result and affective state in terms of cheerfulness, relaxation, activation, sedation and anxiety were surveyed using a numeric rating scale (1 to 10) immediately before (t1), after GE (t2) and seven days (t3) later. Statistics: hierarchical cluster analysis, heat map, χ2 test and paired t test.

Results

Mean propofol dosage was 264 ± 120 mg. Two clusters of mood changes emerged (t1 vs. t2). One (n = 46, 56.1%) was characterized by an unease reaction pattern with equal values regarding cheerfulness, relaxation and anxiety, while relaxation decreased; the other cluster showed a euphoric reaction pattern (n = 36, 43.9%) with markedly increased cheerfulness, relaxation and decreased anxiety. These effects intensified at recall (t3). Despite similar endoscopy results, euphoric cluster patients rated these more positively.

Conclusion

Propofol induces euphoria in nearly half of the patients undergoing elective GE with persisting, even enhanced reminiscence (germanctr.de, trial number DRKS00011202).

The feasibility of office-based propofol sedation for dental care in patients with intellectual disability by sedation practitioners

BACKGROUND

The quality of oral health care for intellectually disabled patients is a significant challenge due to behavioral issues. Intravenous propofol sedation may be useful to relieve the anxiety and fear, and make dental procedures more acceptable. The aim of this study was to evaluate the safety and effectiveness of propofol sedation, by trained nonmedical sedation practitioners, during dental treatments in an office-based setting.

METHODS

Intellectually disabled patients (124) were subjected to restorative dental procedures and moderately sedated using intravenous propofol. Vital signs, cooperation of the patient, and sedation depth were continuously assessed.

RESULTS

Propofol sedation was effective for dental treatment. All procedures resulted in a sufficient level of sedation without moderate or severe complications.

CONCLUSION

Propofol sedation can be safely and effectively performed in an office-based setting by sedation practitioners, who have experience in propofol sedation and are trained in the care of patients with disabilities.

Choice of sedation and its impact on adenoma detection rate in screening colonoscopies

BACKGROUND

Studies have demonstrated that the use of sedation (regardless of type) increases polyp detection rates during colonoscopy. Compared to conscious sedation (CS), propofol sedation (PS) has led to detection of more advanced polyps, yet no apparent difference was found in the overall adenoma detection rate (ADR) in patients undergoing colonoscopy for various reasons. We aimed to assess whether there was a significant difference in the ADR in patients specifically undergoing screening colonoscopies using PS versus CS.

METHODS

This is a retrospective analysis of 699 consecutive patients who underwent inpatient screening colonoscopies at one academic inpatient center. The decision to perform endoscopy using PS versus CS was determined on an individual basis by each provider, taking into account various patient parameters.

RESULTS

No significant difference was noted between ADR or location of detected adenomas between the CS and PS groups. When accounting for each variable, only total endoscopy time of less than 20 min resulted in a statistically significant ADR difference between the two sedation groups (CS: 15.6% vs PS: 21.3%, P = 0.038).

CONCLUSION

ADR in screening colonoscopies is not increased by the use of PS compared to CS. While the use of propofol-based anesthesia is clearly associated with increased patient satisfaction and pain levels, the ADR is not enhanced, and its widespread use in screening colonoscopy sedation should still be investigated.

Propofol sedation versus no sedation in detection of pharyngeal and upper gastrointestinal superficial squamous cell carcinoma using endoscopic narrow band imaging: a multicenter prospective trial

Intravenous propofol can provide a superior quality of sedation compared to standard sedation for upper gastrointestinal endoscopy. However, the utility of propofol sedation for the endoscopic early detection of superficial pharyngeal and esophageal squamous cell carcinoma has not been investigated. In a multicenter, prospective trial, 255 patients with esophageal squamous cell carcinomas (ESCCs) were assigned to receive propofol sedation or no sedation according to their own willingness. The primary aim was to compare the detection rates of superficial cancer in the pharyngeal region and the esophagus between two groups. The secondary aim was to evaluate factors associated with technical adequacy. The detection rate was higher in the propofol sedation vs. no sedation group for H&N region (6.06% vs. 2.40%), but not significantly (P=0.22). However, the small lesion (less than 10 mm in diameter) detection rate was higher in sedation vs. no sedation group for H&N region (88.89% vs. 33.33%; P=0.048). The median time for pharyngeal observation in the sedation group was faster than in the no sedation group (20.6 s vs. 44.3 s; P<0.001). Ninety-five percent of H&N region evaluations were totally complete in sedation compared with sixty percent in the no sedation group (P<0.001). The overall p value indicated that only smoking habit was associated with incomplete pharyngeal observation (P<0.05), and it was more difficult to accomplish a complete pharyngeal observation in patients who smoked more than 10 packs per day. Intravenous propofol sedation compared to no intravenous sedation during conventional upper gastrointestinal endoscopy can facilitate a more complete pharyngeal examination and increase the detection rate of superficial H&N squamous cell carcinoma in high risk patients.