Cannabis Use in Older Surgical Patients: What Anesthesiologists Need to Know

A 2024 narrative review in Drugs & Aging synthesizes evidence on the rising prevalence of cannabis use among adults over 65, examining respiratory, cardiovascular, neuropsychiatric, and pharmacological risks that may complicate anesthesia and perioperative management in this vulnerable population.

Why This Matters

Cannabis use among adults over 65 has surged in parallel with legislative liberalization across North America and Europe, yet perioperative guidelines have not kept pace. Older surgical patients already face elevated baseline risks from age-related organ decline, polypharmacy, and frailty. The pharmacology of cannabis, which spans respiratory, cardiovascular, and central nervous system effects, intersects with nearly every dimension of anesthetic risk. Understanding this intersection is no longer optional for clinicians managing an aging surgical population in which cannabis exposure is increasingly common.

Clinical Summary

Cannabis use among older adults has risen dramatically, with estimates suggesting a 250% increase in under a decade among those over 65. This shift means anesthesiologists and surgeons now routinely encounter patients whose cannabis histories may affect perioperative physiology in clinically meaningful ways. A 2024 narrative review published in Drugs & Aging by anesthesiology-focused authors provides the first integrated synthesis addressing how cannabis pharmacology interacts with age-related physiological vulnerability in the perioperative setting. The mechanistic rationale is grounded in the endocannabinoid system’s widespread distribution: CB1 receptors in the brain, heart, and lungs, and CB2 receptors in immune and peripheral tissues. THC and CBD act on these receptors and also modulate hepatic CYP450 enzymes, creating a pharmacological footprint that touches anesthetic depth, hemodynamic stability, airway reactivity, and drug metabolism simultaneously.

The review’s key findings draw from retrospective cohort studies, case series, and population-level database analyses. Chronic inhalational cannabis use was associated with 145% increased odds of COPD in one multicenter study of 5,291 patients (median age 65), along with FEV1 decline and elevated carboxyhemoglobin. Acute cardiovascular effects include dose-dependent tachycardia (20 to 100% increase), sympathetic activation, and systolic blood pressure elevation, with paradoxical bradycardia and hypotension at higher doses. Multiple retrospective studies linked cannabis use to increased anesthetic and opioid requirements. However, the authors acknowledge that the evidence base is predominantly retrospective with significant confounding, that effect sizes vary substantially across studies, and that cannabis type, route, dose, and frequency likely modulate risk in ways current data cannot disentangle. They call for prospective, controlled studies and standardized screening protocols before firm clinical recommendations can be made.

Dr. Caplan’s Take

This review does something genuinely useful: it gathers the scattered threads of cannabis-perioperative evidence into one place and frames them around the specific vulnerabilities of older patients. That alone is valuable, because most clinicians are still working from anecdotes or extrapolating from younger populations. The honest challenge, though, is that almost everything cited here comes from retrospective data with substantial confounding. When a patient over 65 tells me they use cannabis regularly and asks whether it matters for their upcoming procedure, I owe them a truthful answer: it probably does matter, but we cannot yet say exactly how much or precisely how to adjust.

In practice, I treat cannabis use history the way I treat any pharmacologically active exposure: I ask about it specifically, document type, route, frequency, and last use, and I communicate that information to the anesthesia team. For patients using inhaled cannabis chronically, I pay particular attention to pulmonary function and discuss cessation or at least a period of abstinence before elective procedures. I do not make dramatic protocol changes based on cannabis status alone, but I factor it into a broader risk assessment, especially when cardiovascular or psychiatric comorbidities are already present.

Clinical Perspective

This review sits at an early but important point in the research arc for geriatric perioperative cannabis pharmacology. It confirms directionally what many anesthesiologists have suspected: that cannabis use complicates anesthetic management through multiple organ-system pathways. It also confirms that the evidence base is nowhere near robust enough to generate graded clinical guidelines. The associations between chronic cannabis use and increased anesthetic requirements, COPD risk, cardiovascular instability, and postoperative delirium are biologically plausible and supported by consistent retrospective signal, but they remain associations. No randomized or even well-controlled prospective data exist for this specific population. Clinicians should communicate risk transparently without overstating certainty.

From a pharmacological standpoint, the CYP450 interactions highlighted in the review deserve particular attention in older patients with polypharmacy. THC and CBD inhibit CYP3A4, CYP2C9, and CYP2C19, potentially altering metabolism of benzodiazepines, opioids, anticoagulants, and volatile anesthetics. In patients on warfarin, certain statins, or CYP-metabolized cardiac medications, cannabis co-exposure may shift drug levels unpredictably. The single most actionable recommendation for clinicians right now is to incorporate a structured cannabis use history into every preoperative assessment for patients over 65, documenting product type, THC/CBD content if known, administration route, frequency, and timing of last use, and sharing that information explicitly with the anesthesia team.

Study at a Glance

Study Type

Narrative review (Leading Article)

Population

Adults aged 65 and older undergoing anesthesia with cannabis use history

Intervention

Not applicable (review of cannabis exposure effects)

Comparator

Not applicable (no systematic comparisons performed)

Primary Outcomes

Perioperative respiratory, cardiovascular, neuropsychiatric, and pharmacological risks

Sample Size

Not applicable (largest cited study: over 20 million patients from the National Inpatient Sample)

Journal

Drugs & Aging

Year

2024

DOI or PMID

Not provided in source material

Funding Source

Not reported in available text

What Kind of Evidence Is This

This is an invited narrative review, sometimes termed a “Leading Article,” published in a peer-reviewed pharmacology journal. Narrative reviews occupy a position below systematic reviews and meta-analyses in the evidence hierarchy because they do not employ a documented, reproducible search strategy or formal quality appraisal of included studies. The single most important inference constraint this imposes is that the selection of cited evidence reflects the authors’ judgment rather than a predefined protocol, meaning the potential for selective citation, whether intentional or not, cannot be independently assessed.

How This Fits With the Broader Literature

This review extends a growing body of literature on cannabis and perioperative outcomes by narrowing the lens to older adults, a population largely absent from earlier work that focused on younger or mixed-age cohorts. Large database studies using the National Inpatient Sample have previously identified associations between cannabis use disorder codes and perioperative complications, but these analyses rarely stratified by age or accounted for the distinct pharmacokinetic and physiological profile of older patients. The COPD association highlighted here aligns with findings from Tan and colleagues’ multicenter study, while the increased anesthetic requirement signal is consistent with smaller retrospective reports by Twardowski and others. What this review adds is the explicit framing of these disparate signals through the lens of geriatric physiology, though it does not resolve the fundamental limitation shared by all its source studies: the absence of prospective, controlled data in this population.

Common Misreadings

The most likely overinterpretation is treating the reported associations, such as the 145% increased odds of COPD or the elevated anesthetic requirements, as established causal effects of cannabis use in older surgical patients. These figures derive from retrospective cohort studies with substantial confounding from tobacco co-use, socioeconomic factors, and inconsistent cannabis exposure measurement. The review itself does not perform independent quality appraisal of these studies, so citing its numbers as settled risk estimates would compound the uncertainty. Similarly, readers may infer that the management recommendations represent evidence-graded guidelines; they are better understood as expert-informed suggestions awaiting validation.

Bottom Line

This narrative review establishes that cannabis use among older surgical patients is rising rapidly and intersects with multiple dimensions of perioperative risk, including respiratory, cardiovascular, neuropsychiatric, and pharmacokinetic pathways. It does not establish causal relationships or quantify risk with precision. What it supports right now is a straightforward clinical practice change: systematic, detailed preoperative cannabis screening for every patient over 65, with that information communicated directly to the anesthesia team.

References

1. Narrative review on perioperative anesthetic implications of cannabis use in older adults. Drugs & Aging, 2024. (Full citation details including DOI not provided in source material.)
2. Tan WC, Lo C, Jong A, et al. Cannabis and chronic obstructive lung disease: a population-based study. CMAJ. 2009;180(8):814-820.
3. Twardowski MA, Link MM, Twardowski NM. Effects of cannabis use on sedation requirements for endoscopic procedures. J Am Osteopath Assoc. 2019;119(5):307-311.
4. National Inpatient Sample database analyses examining cannabis use disorder and perioperative outcomes (multiple studies cited within the review; specific citations not individually extractable from available source material).