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LAS VEGAS -- Higher altitudes were tied to a stunningly higher 30-day risk for pulmonary embolism (PE) after total shoulder arthroplasty (TSA), a large retrospective review indicated.

With some 14,000 patients treated in high- and low-altitude cities analyzed, 19 of the high-altitude patients suffered PE within 30 days versus none of those treated near sea level (OR 39.5, P<0.0001), according to Dhanur Damodar, MD, an orthopedic surgery resident at the University of Miami, and colleagues.

That enormously increased risk shrank considerably over the succeeding 2 months, with 28 PEs seen in the high-altitude patients at 90 days compared with 14 in the low-altitude group (OR 2.0, P=0.0315), Damodar reported at the annual meeting of the American Academy of Orthopaedic Surgeons here.

Altitudes as low as 4,000 feet were associated with PE risk. In the U.S., that includes Denver and other sizeable cities in the west such as Reno, Nevada; Flagstaff, Arizona; and Albuquerque, New Mexico.

The findings follow previous studies pointing to an altitude effect on thromboembolic risk after knee and rotor cuff surgeries.

Shoulder arthroplasty procedures "do not usually receive routine post-operative deep vein thrombosis (DVT) prophylaxis, unlike after total hip arthroplasty and total knee arthroplasty," Damodar told 名媛直播 in an interview.

As a result, Damodar said, "it may be feasible to start patients on routine post-operative DVT prophylaxis at high-altitude centers. However there needs to be further randomized, controlled, prospective research done before such a large-scale change in practice can be recommended."

For the new study, Damodar and colleagues analyzed a Medicare database for the years 2005-2014. They compared 6,948 patients who underwent TSAs at altitudes over 4,000 feet to 7,016 who underwent the procedure at altitudes under 100 feet.

The researchers also examined incidents of DVT. No patients in either group suffered DVT at 30 days, and there was no statistically significant difference in DVT counts between groups at 90 days.

Damodar cautioned that while the increased risk of PE at 30 days is "significant and quite high," it's not clear whether the patients recovered from their procedures at high or low altitude. Other factors could also have thrown off the results, he said.

However, other studies have also linked high-altitude orthopedic surgery to higher subsequent risks of venous thromboembolism

Damodar was co-author of another study presented here that examined risk in more than 60,000 patients who underwent 1- and 2-level posterior lumbar fusion procedures from 2004-2015. Those who had surgery above 4,000 feet were more likely to suffer PE by 90 days versus those at under 100 feet (154 vs 112, OR 1.4, P=0.010). There was no statistically significant difference in DVT.

A 2017 study with the same altitude parameters in patients at 30 and 90 days following knee arthroplasty. Another 2017 study, by the same group and with the same altitude parameters, reported higher risks of both DVT and PE .

However, an emergency medicine specialist at the University of Colorado School of Medicine was skeptical about the findings.

Ben Honigman, MD, professor emeritus at the school, told 名媛直播 there's no evidence that significant physiologic changes occur at elevations as low as 4,000 feet.

Studies into thromboembolic events at altitude have tended to focus on altitudes of 7,000-9,000 feet, and even those have not shown "clear evidence" of increased risk, he said.

Honigman said he hasn't noticed any excess risk of thromboembolic events at altitude. However, he said, "we know that altitude travel can change INR [International Normalized Ratio] for people on warfarin. It usually decreases when going to altitude. So we give advice to be careful about that."