May 2007

 

GLAUCOMA

 

Should blood-thinners be stopped before glaucoma surgery?

 


by Tony Realini, M.D.
   

A new study clarifies the risks of hemorrhagic complications in patients using anticoagulation or antiplatelet therapy

In an era when everyone over 40 years old seems to be on daily aspirin therapy, glaucoma surgeons commonly face the clinical conundrum. Should anticoagulation or antiplatelet therapy be discontinued before glaucoma surgery? Cataract surgeons typically say no, but modern cataract surgery is performed under topical anesthesia and through an incision in avascular tissue—the cornea.

Glaucoma surgery, on the other hand, is typically done under peribulbar or retrobulbar anesthesia, which involves blindly passing a long and sharp needle into the anterior or posterior aspect of the orbit. Also, glaucoma surgery involves incisions in the conjunctiva, the sclera, and typically the iris as well.

Given that glaucoma surgery involves cutting through several vascularized structures, is it wise to have patients hold their blood-thinners pre-op?

The study design

Simon K. Law, M.D., and colleagues at the Jules Stein Eye Institute at UCLA, Los Angeles, have conducted a study to answer that question. Dr. Law presented the findings of their research study at the recent meeting of the American Glaucoma Society in San Francisco, California.

“Our goal was to determine the incidence of and the risk factors for hemorrhagic complications in patients on anticoagulant therapy or antiplatelet aggregation therapy who were undergoing glaucoma surgery,” explained Dr. Law.

Anticoagulant therapy (ACT) included the use of drugs such as warfarin or heparin, while anti-platelet aggregation therapy (APT) consisted of therapy with drugs such as aspirin or Plavix (clopidogrel bisulfate, Sanofi Aventis, Bridgewater, N.J.).

To conduct the study, the researchers reviewed nearly 1300 patient charts to find 347 patients who were on either ACT or APT prior to glaucoma surgery. A matched control group consisted of 347 patients undergoing glaucoma surgery who were not using ACT or APT.

“Patients were matched for age, glaucoma subtype, and type of glaucoma surgery,” said Dr. Law. Patients undergoing trabeculectomy or combined phacotrabeculectomy were included, and only one eye per patient was included in the analysis.

The medical records of the 694 subjects were reviewed to identify cases of hemorrhagic complications such as peribulbar or retrobulbar hemorrhage, anterior segment hemorrhage (hyphema requiring surgical intervention or a blood clot occluding the sclerostomy), or posterior segment hemorrhage (such as vitreous or choroidal hemorrhage).

Results

Not surprisingly, the investigators found that using ACT or APT perioperatively increased the risk of hemorrhagic complications during glaucoma surgery.

“Patients on ACT or APT had a higher rate of hemorrhagic complications than controls,” said Dr. Law. “The incidence of hemorrhagic complications in patients using ACT or APT preoperatively was 10.1%, compared to only 3.7% in the control group." This difference was statistically significant (P=0.002).

There were also differences between patients using ACT versus APT. “Eleven of the 48 patients on preoperative ACT (22.9%) and 24 of the 299 patients on preoperative APT (8%) experienced hemorrhagic complications.” This was also statistically significant (P=0.002).

Interestingly, stopping therapy before surgery benefited patients on ACT but not APT.

“Patients whose ACT was continued during the glaucoma surgery had a 31.8% rate of hemorrhagic complications,” said Dr. Law. In contrast, there was no difference in the rates of hemorrhagic complications among patients on APT therapy and who did and did not continue therapy through surgery.

Risk factors identified as a result of the study

The research group identified several risk factors that predicted the occurrence of hemorrhagic complications. Among these were a pre-op diagnosis of cardiac arrhythmia, as well as higher preoperative intraocular pressure (IOP).

“Elevated IOP is a known risk factor for complications such as choroidal hemorrhage," said Dr. Law. "And we suspect arrhythmia is significant because it was the most common reason for our patients to be on ACT.”

Does discontinuing ACT/APT increase the risk for a perioperative thromboembolic event? It appears not, as only three such events occurred: one in a patient who stopped therapy, one in a patient who continued therapy, and one in a control patient.

While Dr. Law’s group has not formally analyzed their data to determine whether glaucoma surgery outcomes were affected by these hemorrhagic complications, “It is my impression, having looked through the data, that there is a detrimental effect of intraoperative bleeding on the ultimate success of the glaucoma procedure.”

Long-term impact on glaucoma surgery outcomes

These findings have important implications for glaucoma surgeons. Most importantly, their study underscores the importance of taking a complete medical history preoperatively to determine if patients scheduled for glaucoma surgery are using anticoagulating or anti-platelet aggregating medications. It is equally important to query patients on their use of vitamins and other supplements, as some commonly-used nutraceuticals (such as vitamin E) are potent blood thinners and may not be included in patients’ self-reported medication lists.

Dr. Law concluded by emphasizing the importance of communicating with the patient's primary medical doctor preoperatively if there are concerns about ACT or APT.

“Most of the primary medical doctors have no idea what's involved in glaucoma surgery,” he said. They may be more familiar with modern cataract surgery, and believe that the risk of bleeding is extremely low. “Talking with them preoperatively is critical in determining who can and cannot discontinue ACT/APT before surgery."

Editors’ note: Dr. Law reported no financial interests related to his comments.

Contact Information

Law: law@jcei.ucla.edu

Should blood-thinners be stopped before glaucoma surgery? Should blood-thinners be stopped before glaucoma surgery?
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