Blood Clots, and What?

We in wound care are always concerned with blood clotting because venous clotting (deep vein thrombosis [DVT]) can be associated with chronic venous disease, chronic edema, lymphedema, and venous ulcers. When a person presents to the wound clinic for evaluation with any of the above problems, they are examined for known or unrecognized thrombophlebitis. A new association with blood clotting has been noted, which many in wound care may not realize—the patient using marijuana. Yes, hypercoagulation and blood clotting have been associated with the use of marijuana, especially in trauma patients.^1-4 I am sure others may think this is not a problem in their wound clinic; however, even our clinic has seen heavy marijuana users. The 2020 National Survey on Drug Use reported marijuana use in 17.9% of persons 12 years or older⁵; additionally, marijuana use is increasing at a rate of 15.3% per year in those 65 years or older.⁶ Considering these numbers, we may not know whether our patients honestly disclose their marijuana use.

It has been shown that the chemicals in marijuana have an effect on platelets, resulting in their activation and a propensity to clot.³ Research has shown that there are cannabinoid receptors on the cell membranes of platelets, and the activation of platelets through a receptor-dependent mechanism from delta-9-tetrahydrocannabinol (THC) induces clotting potential.³ There is also work suggesting endothelial damage and increased oxygen demand play a role in the platelet activation and clotting cascade.⁷

Patients who sustained injuries appear to be the most affected with this problem. In a recent study of trauma patients, Stupinski et al² found those who are chronic and/or recent users of marijuana and involved in a traumatic event are more likely to experience increased clotting problems. They reported that the patients who sustained trauma (from all forms of trauma) and tested positive for THC had an incidence of DVT after the trauma of 6.6% compared with 1.8% of those with similar trauma and were negative for THC use. The incidence of pulmonary embolus was also higher—2.2% of the THC-positive patients and 0.2% of the THC-negative patients.² In another study of older trauma patients (>65 years), Asmar et al¹ found those numbers held true. In their study, the THC-positive group had an incidence of 2.2% of DVT compared with 0.6% in the THC-negative group. Pulmonary embolus was also more common in patients who tested positive for THC (1.4%) vs those who were negative for THC (0.4%).¹ These numbers may not seem very impressive, but in the group of persons over 65 years, the most common injury was a fall (54%). In our wound clinic, we see many older patients (>65 years) with injuries and serious skin tears resulting from falls. Many of those patients present with painful and/or swollen extremities that are generally attributed to the fall or other medical conditions. It is necessary that, as clinicians, we also check whether the person has an increased risk of developing thrombophlebitis because of marijuana use, as well as be more proactive in evaluating the problem.

As health care providers, we must conduct a thorough history and physical examination to ensure the appropriate treatment is used for our patients. To be honest, I never imagined I would need to routinely—and repeatedly—ask older patients about their marijuana use.

Terry Treadwell, MD, FACS
Editor-in-Chief, Wounds
woundseditor@hmpglobal.com