First US guidance published on cannabis use in surgery patients

All patients undergoing a procedure requiring anaesthesia should be screened for cannabis use, according to new guidance published in the US.

The first guidelines on cannabis use in relation to surgery have been issued by the American Society of Regional Anesthesia and Pain Medicine (ASRA Pain Medicine), prompted by concerns that cannabis can potentially interact with anaesthesia. 

About 10% of Americans use cannabis monthly, and it is the most commonly used psychotropic substance after alcohol, according to the US Substance Abuse and Mental Health Services Administration.

However, studies have shown that it can potentially interact with anaesthesia and lead to complications. The guidelines also note that regular use may worsen pain and nausea after surgery and increase the need for opioids.

They recommend anaesthesiologists screen all patients for cannabis use, including asking about the type of cannabis product used, how it was used, (for example smoked, ingested), amount used, how recently it was used and frequency of use.

The guidance is based on an extensive literature review and experiences from the organisation’s Perioperative Use of Cannabis and Cannabinoids Guidelines Committee, which is composed of 13 experts, including anesthesiologists, chronic pain physicians and a patient advocate.

The committee addressed nine questions and made 21 recommendations using a modified Delphi consensus method with more than 75% agreement required for recommendation.­ All 21 recommendations achieved full consensus.

This is the first US-based guideline on perioperative (before, during and after surgery) management of cannabis, according to lead researcher Shalini Shah, MD, vice chair of anaesthesiology at the University of California at Irvine School of Medicine.

The guidelines cover preoperative, intraoperative and immediate postoperative care considerations. They are not intended to replace clinical judgement but rather promote improved patient communication and possibly improved outcomes.

The American Society of Anesthesiologists reviewed the guidelines and is in agreement with their recommendations and affirms their value for anaesthesiologists and surgeons. 

Samer Narouze, MD, PhD, senior author and ASRA Pain Medicine president commented: “Before surgery, anaesthesiologists should ask patients if they use cannabis — whether medicinally or recreationally — and be prepared to possibly change the anaesthesia plan or delay the procedure in certain situations.

“They also need to counsel patients about the possible risks and effects of cannabis. For example, even though some people use cannabis therapeutically to help relieve pain, studies have shown regular users may have more pain and nausea after surgery, not less, and may need more medications, including opioids, to manage the discomfort.”

He added: “We hope the guidelines will serve as a roadmap to help better care for patients who use cannabis and need surgery.”

What the guidelines say

Recommendations receiving an support with the highest level of evidence, include:

1. Screening all patients before surgery
2. Postponing elective surgery in patients who have altered mental status or impaired decision-making capacity at the time of surgery
3. Counselling frequent, heavy users on the potentially negative effects of cannabis use on postoperative pain control
4. Counselling pregnant patients on the risks of cannabis use to the unborn child.

No recommendations could be made for or against:

• the reduction of cannabis administered by other routes (non-smoking) before surgery due to current lack of evidence.
• the routine tapering of cannabis and cannabinoids before, during or after surgery.
• the use of intraoperative electroencephalogram (EEG), a test that measures brain waves, monitoring in patients who have taken cannabinoids.
• adjusting opioid prescriptions after surgery in surgical patients who use cannabinoids.

According to ASRA Pain Medicine, there is also insufficient evidence to guide ventilation settings during surgery in patients who have recently smoked cannabis.

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