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How Should We Prevent Blood Clots Following Arthroscopic Knee Surgery?

Cynthia’s Story and a Limited Discussion of the Literature

Henry I. Bussey, Pharm.D., FCCP

Cynthia, who lives in Florida, contacted ClotCare.org out of a desire to share her story and to let others know how her surgeon changed his practices after her experience.  Following her story is a short over-view on whether arthroscopic surgery warrants anticoagulant prophylaxis and, if so, what form of prophylaxis should be used.

Cynthia’s story (with limited edits) starts here:
I am 61 years old female and was in good health.  In 2016, during my Zumba class I twisted my left knee and both felt and heard a crunch! I had had an ACL (anterior cruciate ligament) repair done on that knee many years before so I figured it was another ACL injury. I lived with the swelling and pain for several months and then finally decided to see an orthopedic doctor who had done my husband’s knee replacement. The xray confirmed a pretty severe tear in my meniscus and the doctor recommended arthroscopic surgery to remove the torn area of the meniscus. The doctor put me on a baby aspirin three times a day. At a week after the surgery I started feeling like I was coming down with the flu and had fatigue, chills and a low grade fever. I did not notice any unusual swelling but I did have foot cramping which felt like my toes were bending backwards. The third day of my “flu” my husband had to leave to visit his folks out of state. I remember him standing by the bed asking if he should stay because I wasn’t feeling well, I told him to go since his dad was ill. My daughter and her husband were living with us at the time so at least I wasn’t by myself. That was Saturday, a little over a week after the surgery. That night my daughter checked in on me and asked if she needed to take me to the ER and I told her no I was fine, though I was feeling worse. At around 2:30 am I rolled over and felt a sharp pain on my right side. When I breathed in I also felt it. I Googled my symptoms and didn’t see anything that suggested a blood clot. The only thing I saw was the possibility of it being shingles! So there I was wide awake thinking I was coming down with shingles. I got up and took myself to the ER not waking my daughter. I thought it was going to be a quick visit just to get a shingles shot, but when I mentioned to the ER physician I just had knee surgery his face turned white and they immediately took blood for a d-dimer test which came back positive. The CT scan showed a very large embolism blocking the whole right lung and a smaller one in the lower left lung. I was hospitalized for six days, and have been back in the hospital six times since then with tachycardia and blood pressure problems. I’m fairly stable now but do not feel quite the same as before, and look and feel much more tired.  Depression is also a battle. I lost my job and my life has forever changed. Doctors are amazed I survived the attack and without any obvious heart damage, but now I feel I will be spending the rest of my life trying to figure out why. To anyone contemplating minor knee surgery, make sure you are on a better clot prevention regimen than baby aspirin. My surgeon changed his protocol based on what happened to me and now uses low molecular weight heparin (such as enoxaparin) or warfarin (brand name Coumadin) and compression stockings for patients getting minor knee surgery.

Comment on Cynthia’s story:  In retrospect, because she had pain and swelling for an extended period of time before going to her doctor, it is possible that she may have developed a blood clot prior to the surgery.  An injury as mild as a sprained ankle can increase the risk of developing a blood clot and the swelling may result from – or increase the risk of having – a blood clot.  After surgery, her foot cramping, fatigue, chills, low grade fever, and a sharp pain upon breathing in are consistent with the signs and symptoms of a deep vein thrombosis (DVT) leading to blood clots in both lungs (bilateral pulmonary emboli or “PE”).  I suspect that she also had an increase in heart rate and breathing rate which are also signs of a PE.  Having a PE is a life-threatening event that should be treated as a medical emergency.  If she had been more aware of the risk and the signs and symptoms of DVT and PE, perhaps she might have sought medical attention earlier and received treatment before the condition progressed as much.  Her subsequent hospital admissions for tachycardia (fast heart rate) and “blood pressure problems” raise concerns about a related possible complication.  With large or multiple PEs, damage to the lungs may result in an increase in the blood pressure in the lungs which, in turn, can overload the right side of the heart and lead to chronic lung and heart conditions.  Hopefully that is not true in Cynthia’s case.

Discussion of DVT and PE prevention in arthroscopic knee surgery:  There is an old country western song that says when you look down into the ole swimmin’ hole, what you see depends on where you stand, how you look, and what you want to see.  Those words apply perfectly to the issue of using anti-clotting drugs to prevent DVT and PE in arthroscopic knee surgery.  Cynthia and her surgeon apparently now are convinced that patients undergoing arthroscopic knee surgery require more aggressive anti-clotting therapy than aspirin.  But the 2012 Chest guidelines recommend no such therapy – not even aspirin – for patients like Cynthia (see http://journal.chestnet.org/article/S0012-3692(12)60126-3/pdf ).  Those who favor anticoagulation focus on the potential for blood clotting events to occur, and the fact that they may be fatal or life-altering, in patients who are usually relatively young and healthy.  Imagine the emotional and psychological impact if Cynthia’s family had found her dead the next morning from a fatal PE.  So what about those who advocate for not using any prophylaxis?  Those individuals will point to the relatively low incidence of DVT & PE with such surgery, the fact that most DVTs are limited and can be treated, and the fact that anticoagulation carries a substantial risk of hemorrhage.  Hemorrhage can be life-threatening and/or it can lead to other complications such as infection and repeat surgery.

As one expert in this area (Dr. Joe Caprini) once said, clinicians make treatment decisions based on data, experience, and emotion; but the most influential of these is emotion.  The above comments illustrate how experience and emotion can factor in to treatment decisions, but what do the data show?

In 2008, what I believe is the largest and best randomized study of DVT and PE prophylaxis in arthroscopic knee surgery was published and is summarized in a ClotCare posting at http://www.clotcare.com/vtekneearthoscopy.aspx  With more than 1,300 low risk, young patients randomized to a low molecular weight heparin (LMWH) for 7 days or graduated compression stockings (GCS) following arthroscopic knee surgery, the incidence of DVT & PE was reduced from 3.2% with GCS to 0.9% with LMWH.  The difference was even greater (5.1% with GCS vs. 1.7% with LMWH) in the approximately 50% of patients who had the meniscectomy (removal of the meniscus).  Major bleeding and clinically relevant bleeding was increased from 0.3% in the GCS group to 0.9% in the LMWH group.  A third arm of the study included LMWH for 14 days but that arm was stopped early because of safety reasons.  The main conclusions from this study was that 7 days of LMWH was beneficial in young, low risk patients and especially in those whose surgery involved meniscectomy.  Many clinicians would argue that the need for LMWH is likely even greater in older patients and/or those with additional clotting risks (such as those with a prior DVT or PE); but those patients were excluded from this study.  In the face of the above data, what is the argument not to use LMWH?  Besides the financial cost of such therapy for all patients, the incidence of the most feared clot (PE) was low and not different (0.3% in each group) while the risk of major and clinically relevant bleeding was increased three fold with LMWH (0.3% vs 0.9%).  Furthermore, the difference in DVT and PE between the two groups was due to symptomatic, distal DVT.  In general, distal (below the knee) DVT carries a low risk of PE and, if symptomatic, then the condition is more likely to be identified and treated.  If we can identify and treat the majority of individuals who develop a symptomatic distal DVT, then it becomes harder to justify exposing all patients to the expense and bleeding risk of LMWH therapy.

More recently (2014), there have been 2 reviews and one meta analysis on the question of DVT & PE prophylaxis in arthroscopic knee surgery (https://www.ncbi.nlm.nih.gov/pubmed/24190733 and https://www.ncbi.nlm.nih.gov/pubmed/24581264).  One review concluded that there is no consensus on how to prevent blood clots in these patients and suggested that each patient needs to be managed on a case by case basis.  The review and meta-analysis focused on proximal (above the knee) DVTs which are known to carry a substantially higher risk of PE than distal DVT.  Key findings from that analysis were (1) that proximal DVT rate is low regardless of whether LMWH is used (4 in 2,184 patients, 0.18%) or not (29 in 1,814 patients, 1.60%), (2) that LMWH reduces the incidence of proximal DVT from 1.60% to 0.18%, and that LMWH reduces the percent of all DVTs that are proximal (29 of 136, 21.3% vs. 4 of 36, 11.1%).  These values are consistent with the study discussed above and at the ClotCare link listed.  So the question is more or less then same – does the limited benefit seen in approximately 2% to 3% of patients justify exposing all patients to the cost and risks of LMWH?  I believe it is fair to say that the decision is a judgement call which reasonably should be influenced by the type of surgery being performed, the age of the patient (since clotting risk increases with age over 50), and other risk factors the patient may have.

But all of the above has been about LMWH… what about aspirin as was used in Cynthia’s case?  Although the Chest guidelines cited above provide a “soft” recommendation for aspirin use in some orthopedic surgeries, the data, in my opinion, are not convincing and many clinicians are reluctant to embrace aspirin for this indication.  But what about in arthroscopic surgery in particular?  I was able to find only one study that had examined this question (see

https://www.ncbi.nlm.nih.gov/pubmed/26630467).  This study described results in 66 such patients who received 325 mg of aspirin daily for 14 days vs. 104 patients who received no prophylaxis.  Patients were examined for clots by ultrasound at 10 to 14 days post operatively.  No DVTs were found in either group.  It is difficult to know what to make of these findings.  It certainly is difficult to conclude that aspirin is beneficial when the outcomes were the same as with no prophylaxis.  Perhaps the study, with 170 patients was too small to identify any DVTs or perhaps some other measures or surgery technique at this single site reduced the DVT risk.  It is also feasible that the ultrasound testing missed finding clots that were there.  Ultrasound is less reliable for clots below the knee and, in fact, in some settings ultrasonographers are taught not to even perform the test below the knee.

So what’s the bottom line?  It seems reasonable to me to consider the risk of the specific surgery being performed, any additional bleeding or clotting risks the patient may have, and have the patient and clinician(s) make an informed, individualized judgement.  In addition, as in Cynthia’s case, it would seem wise to be sure that the patient is aware of not only the risks of DT &PE, but also the signs and symptoms of DVT and PE, and what to do should the signs and/or symptoms develop.  In Cynthia’s cases, she ended up doing the right thing (going to the ER) for the wrong reason (she thought she had shingles, based on her “Google diagnosis”).



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