The effect of delta 9-tetrahydrocannabinol, cannabidiol, and cannabinol on the anaesthesia induced by various anaesthetic agents in mice

[Does medicinal cannabis or cannabis consumption have an influence on the perioperative anesthesiological management?]

The greatly increasing use of medicinal cannabis products as well as the upcoming legalization of cannabis not only require a general re-evaluation of how these substances might be classified as illegal drugs, but also enforce a critical view on the possible consequences that cannabis consumption might have on the anesthesiological strategies applied for surgical procedures. Although high-quality clinical studies are still lacking, several clinical studies meanwhile indicate that an active preoperative cannabis consumption seems to be associated with relevant pathophysiological aspects. Patients who regularly consume high doses of cannabis show an increased risk of cardiovascular and respiratory complications as well as the postoperative nausea and vomitting (PONV) associated with anesthesia. This also applies to relatively young patients. Moreover, the requirements for general anesthetics and analgesics seem to be increased in the context of cannabis consumption, e.g., these patients may require additional efforts when it comes to monitoring the depth of anesthesia and providing a personalized multimodal postoperative pain therapy. It therefore appears to be meaningful to carefully assess and document the extent and duration of the preoperative cannabis consumption during the preoperative assessment. Furthermore, the possibility to perform a preoperative dose reduction of cannabis products in cases with high doses should at least be considered. As the consumption of cannabis is not only increasing in Germany but also worldwide, important future insights will offer a guide towards a safe handling of cannabis in perioperative medicine in the coming years.

Considerations for Cannabinoids in Perioperative Care by Anesthesiologists

Increased usage of recreational and medically indicated cannabinoid compounds has been an undeniable reality for anesthesiologists in recent years. These compounds’ complicated pharmacology, composition, and biological effects result in challenging issues for anesthesiologists during different phases of perioperative care. Here, we review the existing formulation of cannabinoids and their biological activity to put them into the context of the anesthesia plan execution. Perioperative considerations should include a way to gauge the patient’s intake of cannabinoids, the ability to gain consent properly, and vigilance to the increased risk of pulmonary and airway problems. Intraoperative management in individuals with cannabinoid use is complicated by the effects cannabinoids have on general anesthetics and depth of anesthesia monitoring while simultaneously increasing the potential occurrence of intraoperative hemodynamic instability. Postoperative planning should involve higher vigilance to the risk of postoperative strokes and acute coronary syndromes. However, most of the data are not up to date, rending definite conclusions on the importance of perioperative cannabinoid intake on anesthesia management difficult.

The Impact of Cannabidiol on the Induction of Isoflurane Anesthesia and Recovery in Wistar Rats

Background: Beside others, neuroinhibitory and sedative effects of CBD were documented. Aim and Methods: The aim of the study was to assess the dose-related effects of CBD premedication on the course of isoflurane anesthesia. Wistar rats were pretreated with different doses of CBD 1 h before isoflurane anesthesia. In the pretreatment, animals were given CBD at doses of 100, 20, 10, or 2 mg kg^-1. Before the fifth (control) anesthesia, the animals were given only mid-chain triglyceride oil, which served as a solvent in the CBD formulation. The induction time was determined, and on awakening, the time to appearance of the flexion reflex and the recovery from anesthesia were determined. Results: Statistical analysis showed a significantly shorter induction time if animals were pretreated with 20 mg kg^-1 CBD. In addition, pretreatment with 100 mg kg^-1 CBD resulted in a prolonged induction time, while on awakening, delayed appearance of reflexes and prolonged recovery from anesthesia compared to pretreatment with 20 mg kg^-1 CBD were observed. Conclusions: The results indicate that the influence of CBD on the course of isoflurane anesthesia depends on the dose and can reduce the induction time. Although this study was performed in laboratory rats, in clinical practice, these data should be considered when CBD-treated patients undergo isoflurane anesthesia.

The effect of oral Δ-9-tetrahydrocannabinol on the minimal alveolar concentration of sevoflurane: A randomised, controlled, observer-blinded experimental study

BACKGROUND

Cannabis has increasingly been used for medical and recreational purposes. The main pharmacological compound in cannabis is tetrahydrocannabinol (THC), which has sedative, anxiolytic and analgesic effects. In some animal models, THC has also been shown to reduce the minimum alveolar concentration (MAC) of halothane and cyclopropane, but its effect on sevoflurane, currently the most commonly used inhalational anaesthetic agent, has not been investigated.

OBJECTIVE

To investigate the effect of THC on the MAC of sevoflurane in rats.

METHODS

Observer-blinded, randomised controlled trial.

SETTING

Centre for Biomedical Research of the Medical University of Vienna, 2019.

INDIVIDUALS

Thirty-eight adult Wistar rats.

INTERVENTIONS

The rats were allocated randomly into one of two groups. Group A received THC 10 mg kg and group B received the corresponding volume of placebo via gastric gavage (administration through a tube placed in the distal oesophagus). The rats were then individually anaesthetised in an airtight sevoflurane-flooded chamber, and the MAC in both groups was determined using Dixon's up-and-down method. Blood samples were drawn to measure serum concentrations of THC.

MAIN OUTCOME MEASURES

The primary outcome was the MAC of sevoflurane in Groups A and B.

RESULTS

The bootstrap estimate of the MAC of sevoflurane was 2.1 (95% confidence interval 1.8 to 2.4) vol% in the THC group and 2.8 (95% confidence interval 2.7 to 2.9) vol% in the placebo group, corresponding to a significant MAC reduction of 26% in response to THC.

CONCLUSION

Gastric administration of THC 10 mg kg significantly reduced the MAC of sevoflurane by 26%.

TRIAL REGISTRATION

Not applicable.

∆9-Tetrahydrocannabinol, a major marijuana component, enhances the anesthetic effect of pentobarbital through the CB1 receptor

Purpose

∆⁹-Tetrahydrocannabinol (∆⁹-THC) and cannabidiol (CBD), major psychoactive constituents of marijuana, induce potentiation of pentobarbital-induced sleep in mice. We have elucidated the mechanism of enhancement of the anesthetic effect of pentobarbital by cannabinoids.

Methods

We carried out pharmacological experiment and cannabinoid₁ (CB₁) receptor binding assay using CB₁ antagonists to clarify whether the CB₁ receptor is involved in the synergism or not. The affinities of cannabinoids for the CB₁ receptor in the mouse brain synaptic membrane were evaluated using a specific CB₁ ligand, [³H]CP55940.

Results

Although the potentiating effect of ∆⁹-THC on pentobarbital-induced sleep was attenuated by co-administration of CB₁ receptor antagonists, such as SR141716A and AM251, at a dose of 2 mg/kg, intravenously (i.v.) to mice, the CBD-enhanced pentobarbital-induced sleep was not inhibited by SR141716A. The inhibitory constant (Ki) values of ∆⁹-THC and CBD were 6.62 and 2010 nM, respectively, showing a high affinity of ∆⁹-THC and a low affinity of CBD for the CB₁ receptor, respectively. A high concentration of pentobarbital (1 mM) did not affect specific [³H]CP55940 binding on the mouse brain synaptic membrane.

Conclusions

These results suggest that binding of ∆⁹-THC to the CB₁ receptor is involved in the synergism with pentobarbital, and that potentiating effect of CBD with pentobarbital may differ from that of ∆⁹-THC. We successfully demonstrated that ∆⁹-THC enhanced the anesthetic effect of pentobarbital through the CB₁ receptor.

Role of cannabis in cardiovascular disorders

The growing popularity of medical and recreational consumption of cannabis, especially among the youth, raises immediate concerns regarding its safety and long-terms effects. The cardiovascular effects of cannabis are not well known. Cannabis consumption has been shown to cause arrhythmia including ventricular tachycardia, and potentially sudden death, and to increase the risk of myocardial infarction (MI). These effects appear to be compounded by cigarette smoking and precipitated by excessive physical activity, especially during the first few hours of consumption. Cannabinoids, or the active compounds of cannabis, have been shown to have heterogeneous effects on central and peripheral circulation. Acute cannabis consumption has been shown to cause an increase in blood pressure, specifically systolic blood pressure (SBP), and orthostatic hypotension. Cannabis use has been reported to increase risk of ischemic stroke, particularly in the healthy young patients. The endocannabinoid system (ECS) is currently considered as a promising therapeutic target in the management of several disease conditions. Synthetic cannabinoids (SCs) are being increasingly investigated for their therapeutic effects; however, the value of their benefits over possible complications remains controversial. Despite the considerable research in this field, the benefits of cannabis and its synthetic derivatives remains questionable even in the face of an increasingly tolerating attitude towards recreational consumption and promotion of the therapeutic complications. More efforts are needed to increase awareness among the public, especially youth, about the cardiovascular risks associated with cannabis use and to disseminate the accumulated knowledge regarding its ill effects.

Genetic inactivation and prolonged pharmacologic inhibition of monoacylglycerol lipase have opposite effects on anesthetic sensitivity to propofol

Monoacylglycerol lipase (MGL) is a major enzyme involved in degradation of the endocannabinoid 2-arachidonoylglycerol (2-AG). Selective inhibitors of MGL are regarded as promising analgesics and anticancer agents. To gain insight into the possible consequences of their prolonged administration for anesthetic action, the effects of several inhalational and intravenous anesthetics were tested in knockout mice lacking the MGL gene in the loss of righting reflex (LORR) assay. Sensitivity to inhalational and most intravenous anesthetics was not altered in knockout mice. However, compared with wild-type littermates, they showed increased sensitivity to the intravenous anesthetic propofol. Permanently elevated levels of 2-AG after MGL knockout are known to cause desensitization of cannabinoid (CB1) receptors, which have been advocated as possible mediators of propofol anesthesia. Therefore, increased sensitivity to propofol in knockout mice at first suggested that 2-AG may potentiate CB1 receptors despite their hypofunction in these animals. Pharmacologic inhibition of MGL also causes desensitization of CB1 receptors, so sensitivity to propofol was tested further in C57BL/6N mice pretreated chronically with the selective MGL inhibitor JZL 184. Contrary to the results in knockout mice, these animals showed drastically reduced sensitivity to propofol. The reason for increased sensitivity to propofol after MGL knockout remains unclear, but may result from changes occurring in these animals during development. However, our results in C57BL/6N mice pretreated with JZL 184 confirmed the role of CB1 receptors in propofol anesthesia advocated previously, and also suggest that prolonged use of MGL inhibitors may be associated with the development of resistance to propofol.

Poisoning with illicit substances: toxicology for the anaesthetist

The consumption of illicit substances represents a considerable threat to the health and wellbeing of particular sectors of our communities. Hospitalisation is sometimes required for the treatment of the direct toxic effects of the drugs as well as for injuries sustained while under their influence. Although poisoning with 'traditional' substances of abuse such as opioids, cocaine and cannabis still predominate in terms of numbers, the availability and use of new psychoactive substances are on the rise. These latter agents, some of which began life as failed pharmaceutical products, have enjoyed renewed status as recreational stimulants, entactogens or hallucinogens, properties that originally precluded them from legitimate use. These drugs may act by enhancing endogenous release of neurotransmitters, inhibiting their reuptake back into neurons or having direct effects on receptors, and may involve adrenergic, dopaminergic or serotonergic systems. The use of intravenous lipid emulsion for the symptomatic treatment of drug overdose has become a fertile ground for research and may hold promise as a non-specific treatment for poisoning with illicit substances. Dexmedetomidine, an α(2)-receptor agonist with a central sympatholytic effect, may be able to counteract the cardiovascular and central nervous system overstimulation that may accompany stimulant toxicity.

Effect of cannabis on enzyme induction by phenobarbital

Cannabis extracts in olive oil administered s.c. to male adult rats decreases oxidizing microsomal enzymes measured as TPNH disappearance and AHH activity in liver postmitochondrial fraction (93.06% and 25.54% maximum inhibition respectively in chronic treatments). Simultaneous administration of single doses of cannabis extracts (330 mg/kg s.c.) and phenobarbital (100 mg/kg i.p.) causes impairment of total microsomal oxidases (86.83% inhibition) and decreases AHH (31.86% inhibition), thus blocking the enzyme induction by phenobarbital.

Neutralization of the effect of delta 9-tetrahydrocannabinol on barbiturate sleeping time by specific active immunization

Adult mice were actively immunized with delta 9-tetrahydrocannabinol-bovine serum albumin (delta 9-THC-BSA) conjugate. Control animals were immunized with BSA alone. While the administration of pentobarbital and delta 9-THC to control animals resulted in the well known prolongation of the barbiturate sleeping time, in mice immunized with delta 9-THC-BSA conjugate this effect was almost completely neutralized.