There is also substantial evidence that regular cannabis users develop tolerance to some of the impairing effects of cannabis, particularly in the domain of cognitive function. This may explain why the majority of respondents in the present survey disagreed that their use of medical cannabis impairs their driving, and why frequency of use was strongly related to DUIC behaviours. As more jurisdictions legalise medical cannabis and devise strategies for managing DUIC, there is an urgent need for research to establish whether patients who are using medical cannabis at doses required to alleviate symptoms, rather than produce intoxication, are vulnerable to the same impairment seen in healthy volunteers who use cannabis occasionally. The lack of knowledge around what these doses may be is a considerable barrier to developing effective cannabis and driving policy that could be addressed with future research. There are several limitations to the present study that are worth mentioning. The use of convenience sampling allowed us to reach a large population of individuals who were using both legal and illegally sourced medical cannabis for a range of conditions, but is also likely to have introduced a selection bias toward individuals with positive experiences using medical cannabis who favour the relaxation of laws relating to DUIC and to cannabis use more generally. Likewise, responses may have influenced by social desirability bias, with some individuals potentially reporting more socially acceptable rather than true DUIC behaviours, such as longer waiting times before driving and underreporting of negative effects on cannabis use on driving. The reliance on self-report data is also an issue due to potential concerns around validity of responses. We also recognize that most respondents in this survey were using illegally sourced medical cannabis without the recommendation of a healthcare professional.
While this is in part due to the restrictions on patient access to legal medical cannabis that were in place at the time when this survey was live, some respondents did indicate that a significant portion of their total cannabis use was not medical. These data may therefore have limited applicability to other patient populations. Finally, it is important to reiterate that the term ‘medical cannabis’ was used here to refer to any cannabis-based product being used to treat the symptoms of a self-identified health condition. The United Nations estimates that approximately 200 million individuals used cannabis in 2016, an increase of 16% over the past decade.This number is expected to grow as countries around the globe establish legal frameworks for both recreational and medical use. With this shift, it follows that perioperative clinicians are likely to encounter cannabis grow system consumers with increasing frequency.Indeed, previous studies have demonstrated a potential for cannabis to affect numerous organ systems, including the gastrointestinal, respiratory, cardiovascular, haematological, and central nervous systems.Unfortunately, the rapidly changing legal landscape surrounding cannabis has outpaced rigorous scientific research. Evidence related to the management of patients using cannabis in the perioperative period is scarce. In this paper, we present recommendations for the perioperative care of cannabis-consuming patients. This guidance is the result of reviewing available medical literature and of the consensus of a panel of international experts obtained using a modified Delphi technique. The modified Delphi technique used was based on the RAND/UCLA Appropriateness Method developed by the RAND Corporation, and also on the modified Delphi method used by Goel and colleagues and Fitch and colleagues to create consensus guidelines for the perioperative management of buprenorphine.Cannabis contains hundreds of organic compounds, such as terpenes, flavonoids, and cannabinoids . Tetrahydrocannabinol and CBD are the most studied cannabinoid constituents of cannabis.
The physiological effects of these compounds are complex and attributed mostly to their influence on the endocannabinoid system.In the endocannabinoid system, the endogenous ligands anandamide and 2-arachidonoylglycerol have been the most closely studied. Both are closely related to arachidonic acid and are synthesised from AA-containing phospholipids in cellular membranes. Endocannabinoid synthesis occurs in response to overstimulation in postsynaptic neurones as a result of an intracellular calcium rise.Endocannabinoids are released from postsynaptic neurones and lead to presynaptic downregulation of excitatory signals.There has been a tremendous amount of research into the mechanism of action of exogenous THC and CBD on the human nervous system. THC is a cannabinoid receptor Type 1 and a cannabinoid receptor Type 2 partial agonist. CBD is not an agonist at either CB1 or CB2; rather, it is a negative allosteric modulator of the cannabinoid receptor and has been shown to reduce the adverse effects of THC in human studies.The precise mechanism of CBD has not been elucidated. CBD may increase endocannabinoid signalling, and has been found to increase serotonin receptor 1A activity, enhance adenosine signalling, and activate transient receptor potential cation channel Subfamily V Member 1 receptors that detect thermal and nociceptive stimuli.The CB1 receptor is found in virtually all CNS tissues, and is potentially a target of pharmacological intervention in pain pathways.As the understanding of the endocannabinoid system grows, so does its potential for developing into a reliable means of treating patients. To date, evidence suggests that cannabis products have potential use in the treatment of chronic pain, chemotherapy-induced nausea and vomiting, spasticity associated with multiple sclerosis, obstructive sleep apnoea, and fibromyalgia.Research into other cannabisrelated pharmacotherapy treatments for cancer pain, osteoarthritis, and opioid weaning is ongoing. Current evidence regarding these applications is inconclusive.It can be difficult to quantify the pharmacologically active compounds in natural cannabis that are consumed at each dosing interval. The WHO describes a typical cannabis cigarette as containing approximately 500e750 mg of cannabis.
The inhaled dose of CBD or D9 -THC in a cannabis cigarette could be approximated using estimates like this and the percentage of D9 -THC or CBD concentration in that cannabis product . The inhaled dose is the amount of D9 -THC available in the entire cannabis cigarette. The actual amount of D9 -THC delivered to the patient varies greatly and is dependent on multiple variables, such as smoking technique and inspiratory effort.The clinical effects of cannabis vary with the quantity of cannabis consumed and the chronicity of its use.The clinical effects of cannabis involve many organ systems, including the CNS, cardiovascular system, and respiratory system.In the CNS, cannabis has been associated with difficulty achieving adequate depth of anaesthesia and increased cerebral blood flow, and a failure of appropriate cerebral vasodilation occurring with stressful events, such as hypercapnia and hypoxia.Cardiovascular concerns include beta adrenergic-mediated tachycardiad with acute use possibly associated with a greater incidence of myocardial ischaemia in at-risk individuals.Orthostatic hypotension and bradycardia have been associated with heavy acute and chronic cannabis use. In the respiratory system, smoked cannabis has been associated with increased airway reactivity.Other perioperative cannabis-related concerns described in the literature and relevant to perioperative care include postoperative shivering, drug interaction , reduced postoperative sleep quality, trim trays and greater postoperative pain.The Diagnostic and Statistical Manual of Mental Disorders, 5th Edition criteria for the diagnosis of CWS include the abrupt cessation of prolonged or heavy cannabis use accompanied by three or more symptoms of the following: irritability or anger, anxiety, insomnia, decreased appetite, restlessness, altered mood, and a physical symptom causing significant discomfort . The symptoms of CWS occur 24e72 h after cannabis cessation peaking in the first week and lasting 1e2 weeks. ‘Heavy cannabis use’ is not defined in the diagnostic criteria of the DSM V.Regular cannabis use is associated with a down regulation and desensitisation of cortical and subcortical CB1 receptors, which begin to reverse after 48 h of abstinence before returning to normal in approximately 4 weeks.Cannabis users with opioid dependence are less likely to experience CWS, and naltrexone administration has been observed to reduce the self-administration of cannabis and related positive subjective effects in active cannabis users.CWS could potentially contribute to morbidity in the postoperative period. Vigilance for CWS symptoms should be included in relevant perioperative care plans. This is especially true if a patient’s daily cannabis intake is not replaced or continued in the postoperative period. Suspected CWS should provoke referral to a psychiatry service. Tools available for assessing CWS include the Cannabis Withdrawal Scale.
Admission for elective surgery may also provide an opportune time for cannabis education, and patients could be involved in self-monitoring for CWS.There was no consensus amongst the expert panel as to whether nabilone and nabiximols are an appropriate substitution for inhaled cannabis, cannabis oils, and cannabis edibles when weaning from cannabis in the preoperative period in patients not diagnosed with CWS. It is most appropriate to consider nabilone or nabiximols substitution for a patient’s previously administered inhaled cannabis or cannabis oil if they are having CWS symptoms in the postoperative period. Nabilone or nabiximols supplementation/substitution is also not appropriate for patients consuming a cannabis product with an unknown CBD or THC content less than two to three times per day. It is appropriate to consider nabilone substitution for patients with CWS symptoms in the postoperative period if preoperatively they were consuming more than 1.5 g day 1 of high-THC smoked cannabis or more than 20 mg day 1 of THC oil. Patients with suspected CWS should be referred to psychiatry or addiction medicine care providers. These clinicians can help initiate or guide the treatment of CWS with nabilone or nabiximols in perioperative patients, and explore other treatment options for CWS.The heterogeneity of cannabis formulations and products makes concise perioperative recommendations challenging. This is compounded by uncertainty surrounding the significance of cannabis dosing and dosing equivalency between cannabis products. Varied product legality and the frequent off-label use of cannabis products also contribute to gaps in research and knowledge regarding cannabis. A paucity of RCTs examining patients consuming cannabis in the perioperative period necessitates more research to guide care providers. Our panel did not develop quality metrics to evaluate the implementation of the recommendations presented here. Further work is needed to track perioperative outcomes of cannabis users presenting for surgery. Ultimately, as new and existing cannabis preparations are used and the evidence regarding them grows, these guidelines will require review and regular updating.KL is a co-principal investigator of an observational study of medical cannabis funded by Shoppers Drug Mart . AR is currently employed as Chief Medical Officer for PureForm Global, in which she owns stocks.
L-AR has been a member of the Scientific Advisory Board for Nycomed and the Omeros Corporation . He has also conducted studies supported by grants from Ferring Pharmaceuticals . BLF has received funding and research-related donations from Canopy, Aurora, Pfifizer, Bioprojet, BrainsWay, Aphria, ACS, Alkermes, and GW Pharmaceuticals. His research is supported by a clinician scientist award from the Department of Family and Community Medicine of the University of Toronto. HS is an affifiliated member of the Michael G. DeGroote Centre for Medicinal Cannabis Research and is involved in several studies regarding post-surgical cannabis consumption, with one study being funded by the Canadian Institutes of Health Research. SY has received honoraria payment from Canopy Health for her lectures and work on a clinical study advisory board. NJL has received Merck Sharp & Dohme income for noncannabis-related speaking engagements and Vifor Pharmasponsored non-cannabis-related training. PF-S has held consultancy and educational meetings with Spectrum Therapeutics, Grunenthal, and Kyowa Kirin in addition to authoring cannabis-related reviews and the peripheral m-opioid receptor antagonist guidelines. He has also done consultancies for Kingdom Therapeutics and CBD Science. RT is a member of the Tilray, Canopy Growth, Allergan, Lundbeck, and Indivior advisory boards; has received unrestricted education grants from Canopy Growth, Otsuka, Pfifizer, Purdue , Shire, Jansen, Sunovion, Lundbeck, and Allergan; and has received speaking honoraria regarding opioids, pain medicine, or addiction from Indivior, Pfifizer, Otsuka, Allergan, and Lundbeck. SH has received personal fees associated with Medoc Limited and Rafa Limited, and has been involved in research supported by Disarm Therapeutics. HC was a previous advisor for Scientus Pharma , and has been involved with advisory boards for Canopy Growth , AbbVie Corp. , and Medical Cannabis by Shoppers Drug Mart . The other authors declared no conflicts of interest regarding the creation of the recommendations.The novel coronavirus, SARS-Cov-2 or COVID-19, is responsible for a pandemic on a scale not experienced since the 1918-20 H1N1 influenza pandemic.