The holistic effects of medical cannabis compared to opioids on pain experience in Finnish patients with chronic pain

BACKGROUND

Medical cannabis (MC) is increasingly used for chronic pain, but it is unclear how it aids in pain management. Previous literature suggests that MC could holistically alter the pain experience instead of only targeting pain intensity. However, this hypothesis has not been previously systematically tested.

METHOD

A retrospective internet survey was used in a sample of Finnish chronic pain patients (40 MC users and 161 opioid users). The patients evaluated statements describing positive and negative phenomenological effects of the medicine. The two groups were propensity score matched to control for possible confounding factors.

RESULTS

Exploratory factor analysis revealed three experience factors: Negative Side Effects, Positive Holistic Effects, and Positive Emotional Effects. The MC group (matched n = 39) received higher scores than the opioid group (matched n = 39) in Positive Emotional Effects with large effect size (Rank-Biserial Correlation RBC = .71, p < .001), and in Holistic Positive Effects with medium effect size (RBC = .47, p < .001), with no difference in Negative Side Effects (p = .13). MC and opioids were perceived as equally efficacious in reducing pain intensity. Ratings of individual statements were exploratively examined in a post hoc analysis.

CONCLUSION

MC and opioids were perceived to be equally efficacious in reducing pain intensity, but MC additionally positively affected broader pain-related factors such as emotion, functionality, and overall sense of wellbeing. This supports the hypothesis that MC alleviates pain through holistically altering the pain experience.

Subjective experiences during dexmedetomidine- or propofol-induced unresponsiveness and non-rapid eye movement sleep in healthy male subjects

BACKGROUND

Anaesthetic-induced unresponsiveness and non-rapid eye movement (NREM) sleep share common neural pathways and neurophysiological features. We hypothesised that these states bear resemblance also at the experiential level.

METHODS

We compared, in a within-subject design, the prevalence and content of experiences in reports obtained after anaesthetic-induced unresponsiveness and NREM sleep. Healthy males (N=39) received dexmedetomidine (n=20) or propofol (n=19) in stepwise doses to induce unresponsiveness. Those rousable were interviewed and left unstimulated, and the procedure was repeated. Finally, the anaesthetic dose was increased 50%, and the participants were interviewed after recovery. The same participants (N=37) were also later interviewed after NREM sleep awakenings.

RESULTS

Most subjects were rousable, with no difference between anaesthetic agents (P=0.480). Lower drug plasma concentrations were associated with being rousable for both dexmedetomidine (P=0.007) and propofol (P=0.002) but not with recall of experiences in either drug group (dexmedetomidine: P=0.543; propofol: P=0.460). Of the 76 and 73 interviews performed after anaesthetic-induced unresponsiveness and NREM sleep, 69.7% and 64.4% included experiences, respectively. Recall did not differ between anaesthetic-induced unresponsiveness and NREM sleep (P=0.581), or between dexmedetomidine and propofol in any of the three awakening rounds (P>0.05). Disconnected dream-like experiences (62.3% vs 51.1%; P=0.418) and memory incorporation of the research setting (88.7% vs 78.7%; P=0.204) were equally often present in anaesthesia and sleep interviews, respectively, whereas awareness, signifying connected consciousness, was rarely reported in either state.

CONCLUSIONS

Anaesthetic-induced unresponsiveness and NREM sleep are characterised by disconnected conscious experiences with corresponding recall frequencies and content.

CLINICAL TRIAL REGISTRATION

Clinical trial registration. This study was part of a larger study registered at ClinicalTrials.gov (NCT01889004).

Decreased Thalamic Activity Is a Correlate for Disconnectedness During Anesthesia with Propofol, Dexmedetomidine and Sevoflurane but not S-Ketamine

Establishing the neural mechanisms responsible for the altered global states of consciousness during anesthesia and dissociating these from other drug-related effects remains a challenge in consciousness research. We investigated differences in brain activity between connectedness and disconnectedness by administering various anesthetics at concentrations designed to render 50% of the subjects unresponsive. One hundred and sixty healthy male subjects were randomized to receive either propofol (1.7 μg/ml; n = 40), dexmedetomidine (1.5 ng/ml; n = 40), sevoflurane (0.9% end-tidal; n = 40), S-ketamine (0.75 μg/ml; n = 20) or saline placebo (n = 20) for 60 min using target-controlled infusions or vaporizer with end-tidal monitoring. Disconnectedness was defined as unresponsiveness to verbal commands probed at 2.5 min intervals and unawareness of external events in a post-anesthesia interview. High-resolution positron emission tomography was used to quantify regional cerebral metabolic rates of glucose utilization. Contrasting scans where the subjects were classified as connected and responsive vs disconnected and unresponsive revealed that for all anesthetics, except S-ketamine, the level of thalamic activity differed between these states. A conjunction analysis across the propofol, dexmedetomidine and sevoflurane groups confirmed the thalamus as the primary structure where reduced metabolic activity was related to disconnectedness. Widespread cortical metabolic suppression was observed when these subjects, classified as either connected or disconnected, were compared with the placebo group, suggesting that these findings may represent necessary but alone insufficient mechanisms for the change in the state of consciousness.SIGNIFICANCE STATEMENT:Experimental anesthesia is commonly used in the search for measures of brain function which could distinguish between global states of consciousness. However, most previous studies have not been designed to separate effects related to consciousness from other effects related to drug exposure. We employed a novel study design to disentangle these effects by exposing subjects to pre-defined EC₅₀ doses of four commonly used anesthetics or saline placebo. We demonstrate that state-related effects are remarkably limited compared to the widespread cortical effects related to drug exposure. In particular, decreased thalamic activity was associated with disconnectedness with all used anesthetics except for S-ketamine.

Comparative effects of dexmedetomidine, propofol, sevoflurane, and S-ketamine on regional cerebral glucose metabolism in humans: a positron emission tomography study

INTRODUCTION

The highly selective α₂-agonist dexmedetomidine has become a popular sedative for neurointensive care patients. However, earlier studies have raised concern that dexmedetomidine might reduce cerebral blood flow without a concomitant decrease in metabolism. Here, we compared the effects of dexmedetomidine on the regional cerebral metabolic rate of glucose (CMR_glu) with three commonly used anaesthetic drugs at equi-sedative doses.

METHODS

One hundred and sixty healthy male subjects were randomised to EC₅₀ for verbal command of dexmedetomidine (1.5 ng ml^-1; n=40), propofol (1.7 μg ml^-1; n=40), sevoflurane (0.9% end-tidal; n=40) or S-ketamine (0.75 μg ml^-1; n=20) or placebo (n=20). Anaesthetics were administered using target-controlled infusion or vapouriser with end-tidal monitoring. ¹⁸F-labelled fluorodeoxyglucose was administered 20 min after commencement of anaesthetic administration, and high-resolution positron emission tomography with arterial blood activity samples was used to quantify absolute CMR_glu for whole brain and 15 brain regions.

RESULTS

At the time of [F¹⁸]fluorodeoxyglucose injection, 55% of dexmedetomidine, 45% of propofol, 85% of sevoflurane, 45% of S-ketamine, and 0% of placebo subjects were unresponsive. Whole brain CMR_glu was 63%, 71%, 71%, and 96% of placebo in the dexmedetomidine, propofol, sevoflurane, and S-ketamine groups, respectively (P<0.001 between the groups). The lowest CMR_glu was observed in nearly all brain regions with dexmedetomidine (P<0.05 compared with all other groups). With S-ketamine, CMR_glu did not differ from placebo.

CONCLUSIONS

At equi-sedative doses in humans, potency in reducing CMR_glu was dexmedetomidine>propofol>ketamine=placebo. These findings alleviate concerns for dexmedetomidine-induced vasoconstriction and cerebral ischaemia.

CLINICAL TRIAL REGISTRATION

NCT02624401.

Using Positron Emission Tomography in Revealing the Mystery of General Anesthesia: Study Design Challenges and Opportunities

Functional neuroimaging with positron emission tomography (PET) is one of the cornerstones for studying the central nervous system effects of general anesthetics and anesthesia mechanisms. General anesthesia offers a unique and safe way to directly manipulate consciousness, and can thus be used as a powerful research tool to study the neurobiology of human consciousness. In this chapter, we will address the possibilities of PET imaging in revealing the mysteries of general anesthesia and anesthetic induced unconsciousness and summarize some of the recent advancements in the field. Importantly, we will discuss possible ways to separate brain activity changes associated with the changing level of consciousness from the concentration or dose-dependent direct or indirect drug effects on the brain. We will try to demonstrate how state-of-the-art clinical pharmacology, use of specific anesthetic drugs, and innovative study design solutions could be utilized.