What to Know About Deep Vein Thrombosis Prophylaxis

With no official guidelines specific to otolaryngology on perioperative precautions to prevent deep vein thrombosis (DVT), otolaryngologists may not have all the information they need about risks facing their surgical patients.

“Nearly every other surgical sub-specialty has their own guidelines, but we don’t, so we are sometimes forced to make it up on the fly,” said Charissa Kahue, MD, head and neck and micro-vascular surgery fellow at the University of Kansas
Medical Center.

After the otolaryngology department at her hospital recently had three postop patients in one week develop pulmonary emboli—a highly unusual situation—Dr. Kahue examined the literature, created a presentation for her colleagues, and drafted a protocol for head and neck cancer patients.

“It was an unfortunate series of events to have had so many that close together,” she said, adding that this number might normally occur in six months or a year.

Physicians reviewing each case concluded that everything had been carried out according to hospital and American Academy of Chest Physicians guidelines for non-orthopedic surgery (the umbrella that covers otolaryngology). But upon further examination, Dr. Kahue noted that there were additional specific cancer guidelines from the American Society of Clinical Oncology, and that, within otolaryngology, practices for venous thromboembolism (VTE) prophylaxis were highly variable.

CHEST Guidelines and Caprini Scores

In 2012, the American College of Chest Physicians issued guidelines for VTE in non-orthopedic surgical patients, concluding that “optimal thromboprophylaxis in non-orthopedic surgical patients will consider the risks of VTE and bleeding complications as well as the values and preferences of individual patients.”

The guidelines described alternatives for stratifying VTE risk in general and abdominal-pelvic surgical patients, based on risk factors, with similar recommendations for other non-orthopedic surgical populations. 

Risk factors used in the guidelines (CHEST. 2012;141(2):e419S–e496S) are based on Caprini scores, which physicians can use to assess an individual patient’s risk for developing DVT based on a variety of conditions.

“The Caprini score was developed for general surgery, but it has been applied pretty widely outside,” said John Cramer, MD, assistant professor of otolaryngology at Wayne State University in Detroit. “It’s been validated in ENT as well.” Dr. Cramer added that otolaryngologists with an interest in DVT and pulmonary embolism (PE) prophylaxis are using either the Caprini score or some other risk-based system to assess patients.

Otolaryngology-Specific Guidelines

According to a 2016 survey published in Head and Neck, practices in venous thromboembolism prophylaxis vary widely among otolaryngologists. The survey, which comprised 26 questions emailed to 4,376 otolaryngologists, had a response rate of 15.4%.  Eighty-three percent of respondents said they used intraoperative prophylaxis with intermittent pneumatic compression (91.8%), compression stockings (35.9%), or low-molecular-weight heparin (LMWH; 12.3%). Eighty-five percent used postoperative prophylaxis with early ambulation (87.8%), intermittent pneumatic compression (85.4%), compression stockings (43.3%), or low-molecular-weight heparin (42.4%). The majority of the otolaryngologists surveyed (86%) reported that, from 2012-2013, their institutions had variable practice guidelines and 32% did not routinely follow them. The reasons for non-compliance included a perceived low VTE risk and concern for bleeding. Eighty-eight percent of respondents said it would be helpful if the American Academy of Otolaryngology–Head and Neck Surgery released thromboprophylaxis guidelines (Head Neck. 2016;38:E341–E345).

Dr. Cramer said a lack of data may be the reason guidelines specific to ear, nose, and throat surgery don’t yet exist for VTE prevention. “I think the evidence basis has taken longer to emerge than other surgical fields, and there wasn’t enough data when they made the CHEST guidelines, which are probably the most authoritative,” Dr. Cramer said. He added that surprisingly little has been published in otolaryngology and that most of it is on retrospective, single-institution experiences with no randomized trials. “I think the retrospective experience has been accumulating and getting to be somewhat significant,” he said, “so at least we can make some comparisons to more established fields.”

Risk of DVT in Otolaryngology Procedures

According to Dr. Cramer’s 2017 study, “Risk of Venous Thromboembolism Among Otolaryngology Patients vs. General Surgery and Plastic Surgery Patients” (JAMA Otolaryngol Head Neck Surg. 2018;144:9-17), most patients undergoing otolaryngology procedures are at low risk of VTE.  This indicates guidelines for a low-risk population could be adapted to otolaryngology, while patients undergoing high-risk otolaryngology procedures should be considered for more aggressive VTE prophylaxis.

I think a lot of DVT and VTE risk is all about patients ambulating. —John Cramer, MD

Dr. Cramer said otolaryngology is generally a low-risk field for VTE because otolaryngology patients ambulate more. “I think a lot of DVT and VTE risk is all about patients ambulating,” he said.

While otolaryngology may be an order of magnitude less for DVT and VTE as compared with general surgery, neurosurgery, or other fields, Dr. Cramer said the risk is still potentially significant for some subpopulations.

“Even though our patients are at lower risk, our patients in the subpopulation we operate on that have high Caprini scores are definitely at risk for DVT and PE,” Dr. Cramer said. “And for those patients, the number one intervention we can do to prevent death after surgery is appropriate DVT and PE prophylaxis.”

According to Dr. Kahue, evidence shows that the ear, nose, and throat procedures that carry the highest risk are those that involve head and neck cancer, multiple-day hospitalizations after surgery, and significant reconstruction, including free flaps and regional flaps.

The Problem with Sequential Compression Devices

Dr. Kahue said most hospitals require that at the time of general anesthesia induction, all surgical patients have sequential compression devices (SCDs), which  squeeze the ankle, mid-calf, and upper calf. “Even if you’re going home the same day from surgery, they should be placed at the time when someone’s going to sleep,” she said, “and they should be on after surgery.”

For inpatient procedures, many people find the devices annoying and opt out of wearing them after surgery, she said. “I think people don’t understand how important they are “so the compliance rate with SCD use is actually quite low,” she said. Dr. Kahue added that nurses do not enforce compliance, as they are often busy with many other tasks.

But patients who aren’t ambulating should be wearing the devices nearly constantly. “In theory, even if someone is walking around during the day, they really should still have them on when in bed overnight,” she said. “And essentially everyone that is admitted to the hospital should be on prophylactic heparin or low-molecular-weight heparin, like Lovenox, typically for the duration of their hospitalization.”

The Problem with Postop Shots

The number one medication in the hospital that’s not delivered the way it’s ordered in the electronic medical record is DVT prophylaxis, according to Dr. Cramer. Whether patients miss it because they’re off the floor during a scheduled dose or they’re getting a lot of shots per day and start to refuse them, Dr. Cramer said the importance of these shots must be emphasized to patients and hospital staff for patients at high risk for VTE.

For some surgical patients, there may even be a benefit to continuing Lovenox shots at home for two weeks after discharge. But while the recommendation is from primarily high-risk abdominal cancer surgery and there’s no data in otolaryngology to support it, Dr. Cramer said it’s potentially a question for very high-risk otolaryngology patients who have had flaps taken from the lower extremity if their ambulation profile is similar to some orthopedic patients.

“I want to get the right data set, and I want to study it,” he said. “We don’t routinely do it at my institution, but I’ve always been suspicious that our lower extremity free flaps are having a lot of pain and not walking and there could be a subpopulation that’s at a higher risk that could get a more intensive regimen and potentially benefit.”

When to Involve a Hematologist or Cardiologist

Dr. Kahue said she usually asks patients with a history of blood clotting disorders and prior VTE to discuss the appropriate time period to stop and restart antiplatelet and anticoagulation medications with the provider who prescribed them. She said she prefers patients to be off of aspirin or Plavix for five to seven days prior to surgery and resume these medications two to three days after surgery.

“Sometimes the cardiologist or hematologist will want to restart the blood thinners at postop day one and the surgeon prefers to delay restarting,” she said. “That’s another area that needs to be explored, because there’s no good answer. And that’s across all surgical subspecialties.”

In general, she said, an average of five days off anti-coagulation (AC) is what most ear, nose, and throat surgeons request. “Sometimes the cardiologist will give you two to three days and then you accommodate that,” she said.

Colleen Edwards, MD, board-certified hematologist at Mount Sinai Hospital in New York, said strict adherence to VTE prophylaxis is warranted for patients with a history of prior VTE who are having long, complicated surgeries requiring hospitalization for several days, particularly if those surgeries involve cancer. In this case, she said, that would mean Venodyne boots during surgery and prophylactic AC with Lovenox or fondaparinux beginning eight hours postoperatively and daily until the patient is fully ambulatory.

Bridging

According to Dr. Edwards, bridging is not necessary in the vast majority of patients who are on AC prior to the surgery. “There are rare patients who clot within a day or two of stopping AC, but these patients have hematologists who will offer guidance about bridging with IV heparin,” Dr. Edwards said. “Patients with myeloproliferative neoplasms should have their disease well controlled prior to any elective surgery.”

While metabolism, and therefore the half life of direct oral anti-coagulants (DOACs), varies from patient to patient, Dr. Edwards said that she generally holds a DOAC for two days for minor procedures such as a lymph node biopsy, and for four days for major surgeries or surgeries that have very vascular beds, like tonsillectomy. “ENT surgeons must remember that AC is in full effect two hours after a dose of a DOAC,” she said. “There is no lag time, as there is with warfarin. In general, it is safe to restart a DOAC by POD two or three.”

IVC Filters

Dr. Edwards added that there is almost no indication for IVC filters in elective surgery. “If a patient is truly hypercoagulable, they will clot above the filter. The rare exception is the patient who develops a VTE after neurosurgery and there is an absolute contraindication to surgery.” Another exception, she said, would be a patient who had a VTE event and needed urgent surgery before he or she could complete three months of AC. “In these circumstances the filter should be removed as soon as possible,” she said. 

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Renée Bacher is a freelance medical writer based in Louisiana.