Vascular access thrombosis prophylaxis

Vascular access thrombosis in the hemodialysis patient leads to significant cost and morbidity. Fistula patency supersedes graft patency, therefore obtaining a mature functioning fistula in patients approaching end-stage renal disease (ESRD) by early patient education and referral needs to be practiced. Current methods to maintain vascular access patency rely on early detection and radiologic or surgical prevention of thrombosis. Study of thrombosis biology has elucidated other potential targets for the prophylaxis of vascular access thrombosis. The goal of this review is to examine the current available methods for vascular access thrombosis prophylaxis.     

Bleeding complications with enoxaparin for deep venous thrombosis prophylaxis.

The safest and most efficacious method of deep venous thrombosis prophylaxis remains controversial. With the use of enoxaparin, a low-molecular-weight heparin, becoming ubiquitous in many institutions, we specifically examined bleeding complications related to its use. A case-control study was conducted on consecutive patients receiving enoxaparin prophylaxis after primary or revision total knee or total hip arthroplasty or hip hemiarthroplasty. Matched controls receiving no pharmacologic anticoagulation were identified. Patient and operative characteristics, hematologic values, and timing of enoxaparin dosing were analyzed as related to major and minor bleeding complications. A total of 152 procedures with enoxaparin and an equal number of control cases were included for a total of 304 patients. The enoxaparin group had a 23.7% total complication rate compared to 16.5% for the control group (P = .11). The power of the test was .35 and indicated that approximately 970 patients would need to be reviewed to have at least an 80% chance of finding a statistically significant difference. Major complications occurred in 5 patients (3.3%) in the enoxaparin group and 2 (1.3%) in the control group (P = .25, power = .21). Minor complications in the enoxaparin group were slightly higher but not significant at 20.4% versus 15.1% in the control group (P = .23). There were significantly fewer minor complications in the enoxaparin group after primary single-joint procedures (16.50%) than all other procedures (32.4%). Patients receiving the first dose of enoxaparin 10 hours or more postoperatively had significantly fewer complications (P = .05). The postoperative hematocrit drop was significantly greater for the enoxaparin group for all procedures (P = .003) as well as for primary single procedures (P = .0005). The postoperative transfusion requirement was significantly greater after primary single procedures (P = .02) in the enoxaparin group. One patient with an epidural catheter and receiving enoxaparin postoperatively developed an epidural hematoma. Although there were not significantly more complications with enoxaparin, there was evidence of significantly increased postoperative bleeding. The low-power analysis reveals that a large number of patients (970-1,700) are required to show a statistically significant difference in bleeding complications between the 2 groups. To minimize complications, a short period to allow initial hemiostasis postoperatively is recommended, as is preferential use of enoxaparin for primary single-joint replacements. Enoxaparin used in conjunction with an indwelling epidural catheter is not recommended.     

Intraoperative single-dose heparin prophylaxis against deep-vein thrombosis

This randomized prospective study examines the efficacy of intravenously administered heparin as prophylaxis against deep-vein thrombosis, detected isotopically with iodine 125, in 37 patients scheduled to undergo major abdominal procedures. Twenty patients were given 5000 units of sodium heparin on opening the abdominal cavity, while 17 patients who did not receive heparin acted as controls. The effect of heparin was reversed at the end of the operative procedure by protamine. Three control patients had deep-vein thrombosis postoperatively but only one heparin-treated patient did. Complications in the treated group included excessive blood loss intraoperatively in one patient and an incisional hernia postoperatively in another. Although the results are not statistically significant, this study suggests that a single dose of heparin given intravenously during operation is a safe and effective means of prophylaxis against deep-vein thrombosis in patients who undergo general surgical procedures. Studies are now being carried out to determine the optimal dose of heparin, time of administration and duration of anticoagulation.     

Deep vein thrombosis prophylaxis protocol--needs active enforcement

Each hospital department tends to have its own DVT prophylaxis protocol generally based on the recommendations of the THRIFT consensus group. This is developed to help the junior medical staff to prescribe the appropriate prophylaxis according to risk assessment. However, adherence to the protocol tends to be haphazard unless actively enforced. This study is aimed at determining whether active enforcement of the protocol improves the uptake of prophylaxis.     

Recent advances in prophylaxis against deep vein thrombosis

The major development in DVT prophylaxis in recent years has been the introduction of low molecular weight heparins. Their main improvement compared with unfractionated heparin is in the convenience of a once daily dosage, but they have not yet convincingly been shown to be more effective or safer.22 23 A-V impulse boots may have an impact on knee and hip surgery but still face problems with patient acceptability. Probably the best way to ensure that more DVT are prevented is by clinicians maintaining a high level of awareness of the risk, and developing, and adhering to, local guidelines.      

Duration of thrombosis prophylaxis in orthopaedic surgery.

BACKGROUND: We have given seven to 14 days thrombosis prophylaxis after orthopaedic surgery. Recently, six weeks prophylaxis has been recommended. We wished to evaluate the implications of prolonging prophylaxis. METHODS: We made a very thorough search of the hospital register of diagnoses and the registers of the departments of radiology and nuclear medicine and determined the number of detected thromboembolic complications during a five and a half-year period. RESULTS: We identified 91 cases (0.50%) with thromboembolism during the first six weeks after 18.368 orthopaedic operations: 1.4% after 836 total hip arthroplasties and 1.0% after 1.845 hip fractures. In these two groups 19 thromboembolic complications were registered after the second postoperative week. If it had been possible to prevent all of them by prolonging prophylaxis to six weeks, each avoided thromboembolism would have cost around US $ 23.700 in additional drug costs alone. One hip fracture patient died from probable thrombo-embolism during the second and one during the fourth postoperative week. No hip arthroplasty patients died from a probable thromboembolic complication during the third to sixth postoperative week. CONCLUSIONS: We conclude that the frequency of clinically detectable thrombo-embolism and fatal pulmonary embolus is so low during the third to sixth postoperative weeks that prophylaxis beyond two weeks is unwarranted.     

Preoperative hemodilution as prophylaxis of deep vein thrombosis

In a clinical study the effectiveness of aggregation limiters (Dextran and acetyl-salicylic acid) and preoperational normovolaemic haemodilution as prophylaxis for deep vein thrombosis (D.V.T.) was assessed on the basis of experimental work in 404 surgical patients. Our patients were monitored by means of the fibrinogen test and ascending phlebography. Our results show that haemodilution is a very effective preventive for D.V.T. Therefore, moderate normovolaemic haemodilution can be applied as an effective prophylactic measure for postoperative deep vein thrombosis.     

Heterotopic ossification with total hip endoprostheses in various models of thrombosis prophylaxis

The influence of thrombosis prophylaxis on the occurrence of heterotopic ossification after implantation of total hip endoprostheses was analyzed in a series of randomized studies. When low-dose heparin or dextran 40 was administered, the rate of ossification was comparatively high (30.1% and 65.1%). When a combination of acetylsalicylic acid and an antirheumatic (oxyphenbutazone) or low-dose heparin with an antirheumatic (indomethacin) was administered, the ossification rate became significantly lower (6.2% and 16.7%). No severe ossification (Arcq degree III) was observed in the groups given an antirheumatic in addition to thrombosis prophylaxis.     

Protocol violation in deep vein thrombosis prophylaxis.

This study aimed to determine how closely deep vein thrombosis (DVT) prophylactic policies are adhered to in routine general surgical practice, to identify reasons for policy violations and to assess the effects of policy modification. Eight adult patients, sixty of whom had undergone an operation, under the care of six general surgeons, each with their own written DVT protocol, were studied on one weekday. Thirty patients (50%) did not receive DVT prophylaxis according to the policy of the relevant consultant. Most violations occurred for unacceptable reasons, mainly starting low-dose subcutaneous heparin or using thromboembolic stockings postoperatively. However, 43% of protocol violations occurred for acceptable clinical reasons. Following the initial study, a uniform departmental DVT prophylaxis policy was introduced. Nursing and medical staff were thoroughly appraised of the new policy. In a repeat study of 75 patients 1 year later, there were 15 protocol violations among 58 patients who had undergone an operation (27%). However, there were no violations for acceptable reasons. The number of unacceptable protocol violations in the two studies was similar (24/60 and 17/56). The number of patients at moderate or high DVT risk who received no preoperative prophylaxis was the same in both studies (8/48 in both audits). DVT protocol violations are common in routine general surgical practice. Policy modification and unification results in fewer violations, but made little impact on the level of thromboprophylactic care.     

Experiences with loco-regional fibrinolytic therapy of deep venous thrombosis with defined drainage management

From 1989 to September 1997 1184 patients with deep vein thrombosis were treated. 606 (51.2%) received a specific therapy with loco-regional lysis. The application of two cycles of 20 mg Alteplase within 8 hours prevailed in combination with 1000 IE heparin per hour. In absence or lack of therapeutical effect further cycles of 20 or 40 mg of Alteplase were given. In the time free from lysis the patients received 30,000 IE heparin/24 hours depending on the individual aPTT (1.5-2.5 times prolonged). We developed a special drainage-management using perforans-veins during the loco-regional lysis. Complete lysis resulted in nearly half of the cases and in another third there was a lysis of more than 50%. Complications were observed in 5.8% of the patients, 4% due to heparinization. Importantly no life-threatening bleeding like gastrointestinal or cerebral bleeding or pulmonary embolism occurred. According to our data we conclude that the loco-regional lytic effect tends to be better than using systemical lysis, the risks are minimized and patient monitoring and treatment is much simpler.     

Perioperative heparin prophylaxis of deep venous thrombosis in patients with peripheral vascular disease

Perioperative low dose heparin was administered to 24 patients who were compared with 19 control patients undergoing peripheral vascular surgical procedures. This prophylactic measure was ineffective in reducing the incidence of subclinical, post-operative deep venous thrombosis, as indicated by iodine-125 fibrinogen scanning. The data suggest that patients undergoing vascular surgery will not benefit from the routine application of this prophylactic regimen.