(From the Irish Medical Times)
Erica Mills looks at the circumstances under which thromboembolic events might arise, their effects and how to prevent them
The occurrence of thromboembolic events after knee or hip surgery can have serious and fatal consequences. Blockages occurring from blood clots may be found to cause many complications, for example, stroke, heart attack, pulmonary embolisms and deep vein thrombosis (DVT) and, according to Nelzen et al (Journal of Vascular Surgery 14, 1991), contribute to the occurrence of leg ulcers.
Common occurrence
Thromboembolisms are a common occurrence and especially so after surgery. The ENDORSE study, a multinational study published in The Lancet in February 2008, found that 52 per cent of hospitalised patients worldwide were at risk from venous thromboembolism (VTE) in the acute hospital setting; 64 per cent of those were surgical patients.
Furthermore, the study found that of the 297 assessable Irish surgical patients studied, 59 per cent (175 patients) were found to be at risk of VTE, of which 81 per cent (142 patients) were receiving some form of preventative treatment for VTE, although only 64 per cent of these (112 patients) were treated in line with the American College of Chest Physicians (ACCP) evidence based consensus guidelines.
The importance of risk assessment for VTE in patients undergoing hip and knee replacements and surgery on knee fractures is borne out in this study, as these surgeries collectively comprised 12 per cent of the overall surgery patients studied worldwide.
Index of suspicion
Dr Brendan O’Cochlain, cardiology consultant at the Galway Clinic, agreed that doctors treating surgical patients should be very aware of the possibility of venous thromboembolic events after knee and hip surgeries. “There needs to be an increased index of suspicion,” he said, as the consequences of untreated blood clots “can be very serious”.
The possibility of VTE in patients after knee or hip surgeries is quite high, he said, especially when treating elderly patients. (In fact, a study published in the Archives of Internal Medicine in November 2004 found that the likelihood of VTE occurring in an elderly patient is 10 to 20 times that of a younger patient.)
“A younger patient will be able to move around. The elderly, however, are at a risk of venous stasis as they may not be as mobile as a younger person. If you think of an elderly patient, they may be stiff and can perhaps not walk well or may spend a lot of time lying down or may be bedbound,” said Dr O’Cochlain.
In the case of immobilised patients, leg exercises and leg elevation can encourage the flow of blood and help to prevent occurrences of VTE. If a patient receives no exercise, venous stasis can occur. Venous stasis occurs when a person is forced to remain immobile for long periods of time and is a contributing factor in the occurrence of deep vein thrombosis (DVT). The slowed flow of blood attributable to venous stasis makes these patients already susceptible to blood clots, especially in the calves. Doctors need to be aware of this risk, said Dr O’Cochlain, and the complications they can cause after surgery.
“The main thing,” he continued, “is to make sure that the patient is mobilising. This should be done in combination with placing them on a drug like warfarin for six months to a year.” Dr O’Cochlain is in favour of placing all elderly patients on warfarin after knee or hip surgeries, although he said this opinion is something of a controversial one and is not shared by all cardiologists.
Preventive measures
He believes preventive measures should be taken to avoid a blood clot in these cases, as he estimates that a blood clot will form in 30 per cent of cases.
VTE is not usually difficult or expensive to treat in most cases, according to Dr O’Cochlain, and patients can usually be given a low molecular weight heparin (LMWH). Low molecular weight heparins function as an anti-coagulant and can be administered as an outpatient treatment which requires the patient to be monitored but not hospitalised. LMWH may also be used in conjunction with warfarin to encourage further thinning of the blood and dissolution of the clot.
The use of anti-embolism stockings may also be used to discourage the formation of blood clots after surgery. The stockings, which are also known as compression stockings, speed up the circulation, thus discouraging the formation of blood clots. They are especially useful when treating patients who are bedbound and can be used in conjunction with leg exercises and leg elevation.
As a preventive treatment, they are especially useful and have a high prevention rate, according to a study published in the Journal of Orthopaedic Nursing in February last year.
Anti-embolism stockings
The study found that patients who used anti-embolism stockings reduced their risk of venous thromboembolic events, particularly deep vein thrombosis, by over 60 per cent and reduced the risks by up to 82 per cent when used in combination with a mechanical or pharmacological preventive treatment.
Patients with thromboembolic events are quite treatable when their symptoms are caught early, said Dr O’Cochlain. The difficulty in treating patients with thromboembolic events after surgery, he said, is that the symptoms of a blood clot may not be noticed and are frequently “overlooked”. One of the main problems with venous thromboembolic events is that the clots may take a long time to form or patients may take some time to present symptoms. Symptoms may also vary immensely from patient to patient.
A swollen calf
There are many symptoms to watch for in patients who may be presenting with venous thromboembolic events, said Dr O’Cochlain. One of the most typical examples of a venous thromboembolic event is one which occurs in the leg, particularly in the calf. “One of the major signs to look out for would be a patient complaining of a swollen calf. When there is a blood clot, it [the calf] will usually be hot and sore,” he explained.
The presence of a blood clot in the leg may indicate thrombophlebitis or deep venous thrombosis.
Superficial thrombophlebitis affects the veins on the surface of the skin. It is not usually serious and is easily treatable. It is not always a result of surgery, but it is important to be aware that superficial thrombophlebitis may have similar symptoms to the symptoms of DVT. Both may present as redness and inflammation in the leg. DVT occurs in the deeper veins of the leg and the clot formed can be problematic, Dr O’Cochlain said, as it may travel to the lungs, causing pulmonary embolism. “If a patient comes to see you and they are acutely short of breath, they may have a pulmonary embolism.”
Haemoptysis
Other signs which may indicate the presence of a pulmonary embolism include haemoptysis (coughing up blood or blood-tinged sputum), chest pains or difficulty breathing. Unfortunately, thromboembolic events may be difficult to diagnose as the symptoms are not always straightforward.
The length of time a blood clot may take to become problematic is also a hindrance, Dr O’Cochlain said, and the patient’s GP should always remain aware of the possibility of these forming in a post hip or knee surgery patient.
“There is a heightened risk of thromboembolic events after any surgery,” he said. “With blood clots, the symptoms can be all kinds of things. Often, the case is that a typical case may have atypical symptoms. A patient could be complaining of something like back pain as this is where the clot has travelled.”
Dr O’Cochlain recommends that all doctors should maintain an increased level of suspicion to help them diagnose blood clots. These include noting any orthopaedic surgery performed on the patient, watching for rapid heartbeat, shortness of breath and haemotypsis.
If a doctor suspects that a patient has a problematic blood clot, there are many ways he can confirm the diagnosis. These include performing a CT scan with dye or ultrasound to find the clot.
It also may soon be possible to confirm thromboembolic events using a urine test, according to a study last year in the Journal of the American Medical Association. The study centred on the finding of proteins in the urine, especially albumin.
The presence of albumin (microalbuminuria) in the past has been used as a risk indicator for heart attack and stroke, but this study suggests that it may also be a risk indicator for venous thromboembolism.
Blood clots
Researchers studied almost 8,600 people and found that 129 had venous thromboembolisms during the eight-year study. This translates to an average incidence of 0.14 per cent per year. Of these 129 people, it was found that the occurrence of blood clots was almost 40 per cent higher in patients who tested positively for slightly higher amounts of albumin in their urine and it was more than twice as high in those with very large amounts of albumin in their urine.
While this report does not advocate wide-scale screening for albumin as an indicator of venous thromboembolic events, the report suggests that it may be beneficial to doctors to test for the protein if they suspect that a patient might have a blood clot related condition.
“If someone comes into my clinic who I suspect might have venous thrombosis or embolism, possibly with a family history, I might add a test for microalbuminuria. If there is shortness of breath showing that there might be a pulmonary embolism, I can use a test for microalbuminuria in diagnosis,” said Dr Ron T. Gansevoort in the report.
Clinically obese
There are other factors which may elevate the risk of venous thromboembolic events after hip and knee surgery. In addition to the risks posed by venous stasis, there are other factors which may contribute to the formation of blood clots. Patients who are clinically obese, who take the contraceptive pill or who smoke are at greater risk of experiencing problems from blood clots after surgery.
ERICA MILLS 