Venous thromboembolism in spine surgery

Venous thromboembolism is a life-threatening adverse event in spine patients and presents difficult decisions for the surgeon and patient. Prophylactic protocols have been established to prevent the occurrence of venous thromboembolism and its sequelae, including venous occlusion, edema, postthrombotic syndrome, and death. Despite the known benefits of prophylaxis, some surgeons choose not to use it because of concerns over increased bleeding complications and possible iatrogenic neurologic injury. Although mechanical prophylaxis remains an important element in venous thromboembolism prevention, low-molecular-weight heparin is better than other pharmacologic therapies in decreasing the incidence of major events.     

Editorial

ABSTRACT

To determine the incidence of symptomatic thromboembolism in patients with chronic spinal cord injury, a retrospective review of patients followed in a Veteran's Affairs Spinal Cord Injury Unit was conducted. Followed for a mean of 13.7 years after injury, 287 patients were reviewed. Forty events were identified, an incidence of 10 percent. Thirty-three (83 percent) occurred in the first 6 months following injury. The remainder occurred at 1, 1.5, 7, 9, 10, 12, and 14 years after injury, an incidence of 0.17 percent per year.

The incidence of clinically significant thromboembolism in spinal cord injury decreases dramatically after the first 6 months to a level similar to that in the general population (0.18 percent). Possible explanations for this include: 1) immobilization by itself may not be a risk factor for thromboembolism; 2) physiologic adaptations in the chronic state may protect against thromboembolism; and, 3) thromboembolism occurs, but remains subclinical in most patients.     

The St. Jude experience

This paper covers our experience with the use of the St. Jude prosthetic heart valve from November 1979 through August 1983 in 91 patients operated on for aortic and mitral valve replacement. Nonfatal complications included hemorrhagic sequela due to anticoagulation, with an annual rate of 1 percent (1.4 percent per 100 patient years), thromboembolism with an annual rate of 0.8 percent (0.87 percent per 100 patient years), sternal infection 1 percent, operative cardiovascular accident 1 percent, and pericardial tamponade 1 percent.Operative mortality was 1 percent, early mortality (within 30 days) was 3 percent, and late mortality was 3 percent, with a total overall mortality of 7 percent. Excluding two patients who died from noncardiac causes, the overall mortality was 5 percent. The mortality rate per year was 2 percent. The survival rate 3.8 years postoperatively was 89 percent for mitral valve replacement patients and 93 percent for aortic valve replacement patients, for an overall 38 year survival rate of 92 percent. All patients were anticoagulated with warfarin. There were no instances of valve failure, replacement, or serious hemolysis. Eighty-three percent were active or working with a New York heart functional class I.In our experience, the complication rate with the St. Jude valve is as low or lower than that for any other mechanical prosthetic cardiac valve available in the world today.     

Are older patients with mechanical heart valves at increased risk?

Background. Controversy exists regarding the use of mechanical valves in older patients. Many authorities believe that the use of anticoagulants in the elderly is associated with an increased risk of warfarin-related complications. Therefore, we compared the results with mechanical valves in older patients to a cohort of younger patients.

Methods. Aortic (AVR) or mitral valve replacement (MVR) with a mechanical valve was performed in 1,245 consecutive patients who were followed prospectively. They were grouped by age (group 1, ≤ 65 years; group 2, > 65 years). The study groups consisted of AVR (group 1, 459 patients; group 2, 323 patients) MVR (group 1, 313 patients; group 2, 150 patients).

Results. The average age for the groups was: AVR (group 1, 51 years; group 2, 70 years; p = 0.03) and MVR (group 1, 53 years; group 2, 70 years; p = 0.03). For AVR the incidence of thromboembolism was 0.050 (group 1) and 0.038 (group 2) (p = 0.37) and the actuarial freedom from thromboembolism was 83.0% ± 3.0% and 86.5% ± 1.0%, respectively (p = 0.13). The incidence of bleeding after AVR was 0.021 for group 1 and 0.028 for group 2 (p = 0.49). For MVR the incidence of thromboembolism was 0.059 for group 1 and 0.051 for group 2 (p = 0.75) and the actuarial freedom from thromboembolism was 78.8% ± 3.0% and 75.4% ± 8.7%, respectively (p = 0.71). The incidence of bleeding after MVR was 0.020 for group 1 and 0.027 for group 2 (p = 0.62).

Conclusions. Mechanical valves perform well in selected older patients with no increased risk of bleeding or thromboembolism.     

Two mechanical devices for prophylaxis of thromboembolism after total knee arthroplasty. A prospective, randomised study

The optimal characteristics of pneumatic compression for mechanical prophylaxis of thromboembolism after total knee arthroplasty (TKA) are not known. Our study compared two methods of calf compression, with the hypothesis that the device which provided a larger increase in peak venous velocity would produce a lower rate of thromboembolism. We performed a prospective, randomised study on 423 patients (472 knees). Duplex ultrasonography was carried out by experienced technicians who were blinded to the device used. Overall, 206 patients (232 knees) used a rapid inflation, asymmetrical compression (RIAC) device and 217 (240 knees) a sequential circumferential compression device (SCD). The rate of venous thromboembolism was 6.9% with the RIAC device compared with 15% for the SCD device (p = 0.007). The incidence of thrombi with unilateral primary TKA was 8.4% for the RIAC compared with 16.8% for the SCD device (p = 0.03). In 47 patients with a bilateral TKA, the incidence of thrombi was 4% for the RIAC compared with 22.7% for the SCD device (p = 0.05 per knee). There was a low rate of mortality and pulmonary embolism when using mechanical prophylaxis for thromboembolism after TKA. Our findings show that the use of rapid inflation, asymmetrical calf compression gave a significantly lower rate of thromboembolism.     

Prevention of deep vein thrombosis and pulmonary embolus

Venous thromboembolism is common in the perioperative period and in hospitalized medical patients. Difficulties with diagnosis and the risks of treatment make prevention a clinical imperative. To minimize morbidity and mortality, all hospital patients should be assessed for the risk of thromboembolism and bleeding, in order to receive the appropriate prophylaxis. A range of mechanical and pharmacological interventions have been shown to significantly reduce the incidence of venous thromboembolism. Anaesthetic interventions can also modify risk. Newer oral anticoagulants have been developed for use after major orthopaedic surgery.     

Is routine chemical thromboprophylaxis after total hip replacement really necessary in a Japanese population?

Prophylaxis against venous thromboembolism after elective total hip replacement is routinely recommended. Our preference has been to use mechanical prophylaxis without anticoagulant drugs. A randomised controlled trial was performed to evaluate whether the incidence of post-operative venous thromboembolism was reduced by using pharmacological anticoagulation with either fondaparinux or enoxaparin in addition to our prophylactic mechanical regimen. A total of 255 Japanese patients who underwent primary unilateral cementless total hip replacement were randomly assigned to one of three postoperative regimens, namely injection of placebo (saline), fondaparinux or enoxaparin. There were 85 patients in each group. All also received the same mechanical prophylaxis during and after the operation, regardless of their assigned group. The primary measurement of efficacy was the presence of a venous thromboembolic event by day 11, defined as deep-vein thrombosis detected by ultrasonography, documented symptomatic deep-vein thrombosis or documented symptomatic pulmonary embolism. The duration of follow-up was 12 weeks. The rate of venous thromboembolism was 7.2% with the placebo, 7.1% with fondaparinux and 6.0% with enoxaparin (p = 0.95 for the comparison of all three groups). Our study confirmed the effectiveness and safety of mechanical thromboprophylaxis without the use of anticoagulant drugs after total hip replacement in Japanese patients.     

Pulmonary Embolism Prophylaxis in More Than 30,000 Total Knee Arthroplasty Patients: Is There a Best Choice?

Prophylaxis for pulmonary embolism (PE) prevention in total knee arthroplasty remains controversial. A joint registry evaluated venous thromboembolism prophylaxis and anesthesia impact on the incidence of PE, fatal PE, and death. Patients received mechanical prophylaxis alone or chemical with or without mechanical prophylaxis. The overall PE incidence was 0.45%; fatal PE, 0.01%; and death, 0.31%. The only significant difference in any outcome was the incidence of PE between Coumadin and mechanical prophylaxis alone. Variables associated with a higher incidence of PE were age, an American Society of Anesthesiologists score of 3 or higher, and the use of general anesthesia. Based on the findings, general anesthesia can be discouraged, and only Coumadin fared better than mechanical prophylaxis alone, whereas other forms of chemical prophylaxis revealed no significant differences.     

Manual calf massage and passive ankle motion reduce the incidence of deep vein thromboembolism after total hip arthroplasty

Background

Venous thromboembolism is one of the general complications following total hip arthroplasty, wherein various preventive treatments have been recommended. Several studies reported that venous thromboembolism incidence after total hip arthroplasty was similar in patients who were administered prophylaxis with a conventional mechanical procedure alone, and those who were administered pharmacological anticoagulation therapy. Therefore, the optimum methods of prophylaxis are still controversial. The purpose of this study was to investigate whether manual calf massage and passive ankle motion could lower the risk for venous thromboembolism after total hip arthroplasty.

Five-year clinical evalution of the St. Jude medical valve prosthesis in 136 patients

One hundred and thirty-six patients (June 1979, through May 1984) underwent mitral, aortic or double valve replacement and apico-aortic bypass with the St. Jude Medical (SJM) prosthesis, at Ryukyu University Hospital, Okinawa. Operative mortality for the entire group was 4.4 per cent. Late mortality from 1979–1984 was 6.1 per cent. There were no deaths related to mechanical failure. Warfarin anticoagulation was recommended for all patients. The incidence of thromboembolism was 0.76/100 patient years. Post operative catheterization studies in 21 patients one year after operation showed a satisfactory recovery of cardiac function. The SJM valve seems to be the satisfactory artificial valve in present use.     

Professional standards review organizations and their implications for physicians. II. Thromboembolism on mitral valve prosthesis

Although improvements in surgical technique, prosthetic design, and anticoagulant therapy have decreased the initial high incidence of thrombosis, thromboembolism, and excessive overgrowth causing valve dysfunction, these complications of prosthetic valve replacement continue to be potential hazards. Some investigators have further reduced the incidence of thromboembolism by covering exposed metal surfaces with fabric to anchor the extensions of pannus formation over the metal/fabric interface. This has been accomplished at the expense of reduction in flow area.For the past 3 years we have directed our efforts at minimizing the extent of tissue deposit on fixation rings by coating the Teflon fabric with a polyurethane film.^* Previous clinical use of polyurethane-filmed Teflon trileaflet valves between 1959 and 1962, and recent experimental evidence, indicated that the filming technique materially reduces or prevents tissue deposition on Teflon fabric. Since January, 1972, all fabric fixation rings have been filmed with polyurethane; during this period of observation there has been no incidence of thrombosis, thromboembolism, or valve dysfunction from excessive tissue overgrowth. The use of polyurethane filming may prove to be a valuable adjunct in avoiding or reducing potential hazards in prosthetic replacement surgery in the future.     

Selection of prosthetic heart valves for adult patients by age

The use of bioprosthetic heart valves has dramatically increased over the last decade. In 2004, the ratio was 52% for mechanical and 48% for bioprosthetic valves in a survey by the Japanese Association for Thoracic Surgery. This increase in the use of bioprosthetic valves is related to evidence demonstrating the durability of such valves over the last 20 years. The guidelines of the Japanese Circulation Society recommend selection of prosthetic heart valves by considering the patient's age. In patients who received a mechanical valve in previous cardiac surgery, selection of another mechanical valve is inevitable. The age of 65 years is when patients are separated into groups receiving either mechanical (<64 years) or bioprosthetic (> or =65 years) valves. However, the evidence that a bioprosthetic valve is better for patients in their 60s is somewhat questionable, particularly in Japanese with a long life expectancy. Anticoagulation with warfarin in patients with mechanical valves leads to a higher incidence of hemorrhagic complications compared with bioprosthetic valves, although the incidence of thromboembolism is the same. Thus patients with contraindications to warfarin or a low risk of thromboembolism who are more than 65 years old are reasonable candidates for a bioprosthetic valve. It is also recommended that women of childbearing age receive bioprosthetic valves after being informed of the possibility and risks of reoperation. In addition to the information in the guidelines and physicians' preference for valve selection, factors such as the patient's lifestyle, wishes, cardiac function, other complications, and longevity must always be considered when selecting a valve prosthesis.     

Early postoperative anticoagulation after mechanical valve replacement: a systematic review

The optimal approach to early postoperative anticoagulation after mechanical valve implantation remains controversial. This review article examines the pathogenesis of thrombus formation and the different strategies for early postoperative anticoagulation. The most commonly reported anticoagulation regimens had the after estimates of early postoperative thromboembolism and hemorrhage: oral anticoagulation alone (0.9%, 3.3%); oral anticoagulation with intravenous unfractionated heparin (1.1%, 7.2%); and oral anticoagulation with low molecular weight heparin (0.6%, 4.8%). Although intravenous heparin may be associated with a higher incidence of hemorrhage, a randomized trial is needed to provide the best evidence regarding early postoperative anticoagulation after mechanical valve implantation. Nearly four decades have passed since the first mechanical prosthetic valves were implanted. Frequent thromboembolic complications with the first mechanical valves led to recommendations of universal anticoagulation for these patients. Since then, several design changes and modifications have been made to improve the longevity, hemodynamics, and thrombogenicity of newer generation mechanical valves. With improved blood flow, less stasis, and less thrombogenic materials, lower rates of thromboembolism have been reported. Despite these advances however, thromboembolism and anticoagulant-related bleeding continue to account for 75% of all complications after mechanical valve replacement. Occurring most commonly within six months after implantation, these complications can adversely affect mortality and quality of life. Furthermore, the threat of their occurrence creates a psychological burden for each patient with a mechanical valve. The need for life-long anticoagulation in patients with mechanical valves is not in dispute, and the perioperative management of anticoagulation during non-cardiac surgery has been reviewed extensively. However, the approach to early postoperative anticoagulation after mechanical valve implantation is still a matter of debate. The optimal intensity and timing of anticoagulation to prevent early thromboembolism after valve replacement surgery without postoperative bleeding complications is unknown. Hence, many anticoagulation protocols have been proposed, but a lack of consensus remains. The objectives of this study were (1) to reexamine the pathogenesis of thrombus formation and the need for anticoagulation; (2) to critically review the literature on early postoperative anticoagulation strategies; and (3) provide an estimate of the incidence of bleeding and thromboembolism for each approach to early postoperative anticoagulation.     

Current use of thromboembolism prophylaxis for laparoscopic cholecystectomy patients in Sweden

Background The need for thromboembolism (TE) prophylaxis during laparoscopic surgery is not well established. The aim of this study was to investigate current TE prophylaxis in patients undergoing laparoscopic cholecystectomy (LC) in Sweden.Methods Mail questionnaire to all Surgical Departments in Sweden about the current use of thromboembolism prophylaxis in patients undergoing laparoscopic cholecystectomy.Results The response rate was 78 of 80 departments of surgery (98%). Seventy reported performing LC. Thirty-six percent used thromboembolism prophylaxis in all patients, 17% in most, 9% in half their patients and 39% only rarely. The current use of thromboembolism prophylaxis ranged from low-molecular-weight heparin for 7 days + stockings in all patients to no prophylaxis at all in the majority of patients.Conclusions The use of thromboembolism prophylaxis in LC patients is highly variable, even in the small and homogenous country of Sweden. Further studies concerning the risk of TE complications after laparoscopic surgery are warranted.     

Long-term results of mechanical valves in aortic position and biological valves in mitral and tricuspid positions

The long-term results of patients undergoing aortic valve replacement (AVR) with a mechanical valve (AM), mitral valve replacement with a biological valve (MB), and tricuspid valve replacement (TVR) with a biological valve (TB) operated upon from 1977 to 1988 were retrospectively analysed. A total of 899 patients received 1117 valves (381 AM, 633 TB, 103 TB) with a follow-up 3778 patient-years and 4582 valve-years. A significant incidence of thromboembolism, hemorrhage, and endocarditis was not found among AVR, MVR, TVR, or multiple valve replacement. We found a significantly decreased incidence of survival rate in multiple valve replacement compared with AVR or MVR, and a significantly increased incidence of reoperation in MB compared with AM and TB. We use AM and TB in any adult patients as a first choice. However, we prefer a mechanical valve in the mitral position except in patients over 65 years old, who have a short life expectancy, in whom anticoagulation is thought to be difficult, and who desire a biological valve.     

Incidence of complications with operative choledochoscopy

A 5 year retrospective study of the use of cholangioscopy in 153 difficult biliary cases including stones, strictures, tumors, and anomalies has been reported. In the 88 patients (58 percent) who underwent both operative cholangiography and cholangioscopy, the cholangioscope revealed 11 lesions (13 percent) missed by cholangiography. In this series, eight retained stones (5.2 percent) were detected on postoperative T-tube cholangiography; of this group, two patients had previous biliary surgery, two had an associated neoplasm, and four had incomplete cholangioscopy for various reasons. Postoperative complications included transient bile drainage (8 percent), pancreatitis (8 percent), persistent jaundice (7 percent), cholangitis (5 percent), and abscess (5 percent). Comparison of an operative cholangiography-only group with a cholangioscopy-only group revealed no significant difference in the incidence of postoperative complications. Cholangioscopy did not increase postoperative complications in this study. It frequently detected lesions missed by cholangiography and helped define the nature of the lesions. The incidence of retained stones may be reduced by use of the cholangioscope in difficult biliary cases. Its routine use in common bile duct exploration is recommended.     

Post-operative thromboembolism in neurosurgery

Summary This study compares the safety and effectiveness of two methods for the prophylaxis of post-operative thromboembolism in neurosurgical patients: A: low-dose heparin (5,000 IU×2 s.c.) started preoperatively and continued daily for one week post-operatively, and B: per-operative electrical calf muscle stimulation with groups of impulses plus post-operative dextran infusions every other day for one week.Neurosurgical patients aged 40 years or more with normal laboratory coagulation values and operated under general anaesthesia were included. The 125:I-fibrinogen uptake test (FUT) was used for screening and phlebography for verification of deep venous thrombosis (DVT). 122 patients entered the study and 104 completed the prophylactic protocol, 58 in group A and 46 in group B. The two groups were comparable according to pre-operative data and distribution of diagnoses.89 patients completed screening for post-operative DVT. We found an overall incidence of 5/49 (10 percent) DVT in group A and 5/40 (13 percent) in group B, compared to a frequency of 32–50 percent for controls without prophylaxis reported in the literature^{6, 16, 18}. In spite of prophylaxis our patients with intracranial neoplasms and intracranial vascular disease showed a relatively higher incidence of DVT, 4/23 (17 percent) and 4/14 (29 percent) respectively, compared to patients with spinal diagnoses 2/25 (8 percent). In combination with cranial diagnoses paretic lower limbs meant an apparent risk factor, 4/7 (57 percent). However, paretic limbs appearing in cases with spinal disorders did not predetermine an unsuccessful prophylaxis, 2/14 (14 percent).Blood loss, transfusion requirements and post-operative complications did not differ significantly between the two prophylactic groups.It is concluded that both methods reduce the incidence of post-operative DVT in neurosurgical practice and that they can be used with safety. However, the basic mechanisms behind thromboembolism following parenchymatous brain lesions ought to be studied further to enable a better understanding of the thromboembolic complications and further improvement of the prophylaxis.     

Heparin prophylaxis and the risk of venous thromboembolism after robotic-assisted laparoscopic prostatectomy

Study Type – Therapy (case series) Level of Evidence 4 What’s known on the subject? and What does the study add? The incidence of deep venous thrombosis (DVT) in major urological surgery has decreased over time with the introduction of pharmacological prophylaxis, early mobilization, and the use of sequential mechanical compression devices. We examined the value of heparin prophylaxis in robotic assisted laparoscopic prostatectomy (RALP), where the risk of DVT is already low. The rate of thromboemolic events within 30 days was 0.6% in this series. Heparin did not influence estimated blood loss, haematrocrit change, or length of stay. The incidence of thromboembolism is low after RALP, which may obviate the use of heparin prophylaxis. However, its use appears to be safe and does not affect surgical outcomes.

OBJECTIVE

? The incidence of venous thromboembolism (VTE) after robotic‐assisted laparoscopic prostatectomy (RALP) in patients receiving perioperative heparin prophylaxis was compared with those who did not receive such prophylaxis.

MATERIALS AND METHODS

? Between July 2007 to February 2010, a total of 307 RALPs were performed at our institution by two surgeons. A total of 187 patients operated on by surgeon 1 received perioperative heparin prophylaxis, whereas 120 patients operated on by surgeon 2 did not receive any. ? All demographic, clinical and pathological data were prospectively recorded, whereas the incidence of venous thromboembolism within 30 days of the operation was retrospectively reviewed. Evaluation for potential VTE was based on clinical symptoms.

RESULTS

? Cohorts were comparable with respect to PSA, clinical stage, preoperative Gleason score, body mass index, smoking status, pathological stage, path Gleason score and margin status. A total of two thromboemoblic events occurred (0.6%) within 30 days of surgery (one in each arm of the study). ? Heparin prophylaxis did not influence estimated blood loss (P= 0.076) or haematocrit change from preoperative levels (P= 0.378). Length of stay was comparable between the two groups (1.4 vs 1.3 days; P= 0.159).

CONCLUSION

? The incidence of thromboembolism is low after RALP, which may obviate the need for heparin prophylaxis. However, its use is safe and does not impact surgical outcomes. Larger series are needed to confirm the results obtained in the present study.     

Considerations in Selection and Management of Patients Undergoing Valve Replacement with Glutaraldehyde-Fixed Porcine Bioprostheses

From November, 1973, through June, 1978, 428 operations in 425 patients were performed for replacement of aortic, mitral, or aortic plus mitral valves, utilizing 277 Hancock and 180 Carpentier-Edwards bioprostheses. Actuarially determined survival at 36 months was similar for all three groups and compared favorably with our experience with the Björk-Shiley prosthesis. Certain patient-related variables influencing late survival were identified by multivariate analysis and included previous operation for congenital heart disease, coronary artery bypass grafting in nonaortic valve replacement, race (black), age at operation, and New York Heart Association Functional Class. A small but definite incidence of thromboembolism occurred in all three groups, again similar to our experience with the Björk-Shiley prosthesis. Multivariate analysis identified four factors influencing risk of thromboembolism: previous cardiac operation, age, double-valve replacement, and rhythm at discharge. Valve degeneration occurred, primarily in children and young adults. Over the medium term, the porcine bioprosthesis compared favorably with mechanical prostheses in terms of survival, function, and thromboembolism. Certain patient-related variables affecting survival may be modified by earlier surgical intervention.     

Prevention of deep vein thrombosis and pulmonary embolism

Venous thromboembolism is a major cause of perioperative morbidity and mortality. Immobilized medical patients are also at risk. Long-term sequelae represent a significant chronic health burden. Hospitalized patients should be assessed for their risk of thromboembolism and bleeding at regular intervals. Risk stratification using recommended models can be used to guide the choice of thromboprophylaxis. Both mechanical and pharmacological interventions reduce the incidence of venous thromboembolism. Extended prophylaxis is now recommended following high-risk orthopaedic and cancer surgeries and a number of newer oral antithrombotic agents are now available for this. Anaesthesia should be tailored to minimize the risk of venous stasis and maximize early postoperative mobilization.