Benefits of deep-vein thrombosis prophylaxis in the nonsurgical patient: The MEDENOX trial

Venous thromboembolism (VTE) is a common complication of hospitalized patients, imposing a major clinical and economic burden. Three of four cases of fatal pulmonary embolism occur in nonsurgical settings, but thromboprophylaxis is far less common in medical than in surgical patients. This is mainly attributable to the heterogeneity of nonsurgical populations and lack of high-quality evidence to support specific thromboprophylactic measures. The recent Prophylaxis of Venous Thromboembolism in MEDical Patients With ENOXaparin (MEDENOX) trial addressed this deficiency by assessing the need for and the benefit:risk ratio of thromboprophylaxis in a well-defined group of medical patients immobilized with severe illness. The MEDENOX study showed that these patients are at significant risk of VTE. Enoxaparin, 40 mg once daily for 6 to 14 days, reduced the risk of VTE by 63% without increasing adverse events. It is anticipated that data from the MEDENOX study will be incorporated into future consensus guidelines on the prevention of VTE. Further studies are required to assess the benefit:risk ratio of therapy in other clearly-defined medical groups.

Economic evaluation of enoxaparin as postdischarge prophylaxis for deep vein thrombosis (DVT) in elective hip surgery

OBJECTIVES

Clinical trials indicate enoxaparin thromboprophylaxis (Clexane) can be effective and safe when used in an outpatient setting and that extending the length of thromboprophylaxis with enoxaparin to the postdischarge period may be more effective than inpatient thromboprophylaxis alone. This may increase the cost of thromboprophylaxis. The objective of the study was to estimate the expected cost-effectiveness of using enoxaparin for hospital admission only vs. enoxaparin for hospital admission and for 21 days postdischarge.

METHODS

Decision analysis was used to combine probability, resource use and unit cost data, using the framework of cost-effectiveness analysis. The model used a societal perspective to estimate the expected costs of treatment and outcomes to patients undergoing orthopedic surgery for elective hip replacement. Incremental cost-effectiveness ratios were calculated to provide estimates of the cost per life gained, cost per year life year gained and cost per quality-adjusted life year gained with extended use of enoxaparin thromboprophylaxis.

RESULTS

There was an expected cost per quality-adjusted life year gained of pounds 5732 associated with extended enoxaparin thromboprophylaxis. The results were sensitive to the percentage of patients who could administer enoxaparin injections at home, the rate of DVT associated with standard enoxaparin thromboprophylaxis and the rate of PE associated with standard and extended enoxaparin thromboprophylaxis.

CONCLUSIONS

The analyses indicated that in most cases extended enoxaparin thromboprophylaxis resulted in increased costs for health care services. In all cases, extended thromboprophylaxis with enoxaparin was associated with improved survival and life-years gained.

Pulmonary artery catheterization and mortality in critically ill patients

Pulmonary artery catheters are widely used in intensive care, but evidence to support their widespread use in sparse. Some published data suggest that greater mortality is associated with use of these catheters. The largest study to date looked at > 5500 patients in several centres in America and found a greater 30 day mortality in those patients receiving a pulmonary artery catheter. We tested the hypothesis that, on our intensive care unit, mortality was greater for those patients receiving a pulmonary artery catheter. Using a propensity score to account for severity of illness, the odds ratio for mortality in those patients receiving a pulmonary artery catheter was 1.08 (95% confidence interval 0.87-1.33). We believe that continued use of the pulmonary artery catheter is safe; a large randomized controlled trial examining outcome is unlikely to provide an adequate answer.

Venous thromboembolic disease management of the nonsurgical moderate- and high-risk patient

Venous thromboembolism (VTE) is at least as common among medical as in surgical patients, and fatal pulmonary embolism (PE) occurs most commonly in medical patients. As in surgical patients, risk factors and high- and low-risk groups have been identified, but no useful risk assessment models (RAMs) have yet been developed for medical patients. The incidence of VTE varies widely, but a history of previous VTE, age greater than 40 years, obesity, and prolonged immobilization are all associated with an increase In risk. Stroke, spinal cord injury, and cancer patients are at particular risk of VTE. Low-dose unfractionated heparin (UFH), low-molecular-weight heparins (LMWHs), antiplatelet agents, and warfarin reduce the incidence of VTE. Current standards of thromboprophylaxis vary with indication. However, utilization is frequently low, even in high-risk patients. Effective prophylaxis must be tailored to the individual patient, taking into account both the history of the patient and the disease.

A comparison of enoxaparin with placebo for the prevention of venous thromboembolism in acutely ill medical patients. Prophylaxis in Medical Patients with Enoxaparin Study Group

BACKGROUND

The efficacy and safety of thromboprophylaxis in patients with acute medical illnesses who may be at risk for venous thromboembolism have not been determined in adequately designed trials.

METHODS

In a double-blind study, we randomly assigned 1102 hospitalized patients older than 40 years to receive 40 mg of enoxaparin, 20 mg of enoxaparin, or placebo subcutaneously once daily for 6 to 14 days. Most patients were not in an intensive care unit. The primary outcome was venous thromboembolism between days 1 and 14, defined as deep-vein thrombosis detected by bilateral venography (or duplex ultrasonography) between days 6 and 14 (or earlier if clinically indicated) or documented pulmonary embolism. The duration of follow-up was three months.

RESULTS

The primary outcome could be assessed in 866 patients. The incidence of venous thromboembolism was significantly lower in the group that received 40 mg of enoxaparin (5.5 percent [16 of 291 patients]) than in the group that received placebo (14.9 percent [43 of 288 patients]) (relative risk, 0.37; 97.6 percent confidence interval, 0.22 to 0.63; P< 0.001). The benefit observed with 40 mg of enoxaparin was maintained at three months. There was no significant difference in the incidence of venous thromboembolism between the group that received 20 mg of enoxaparin (43 of 287 patients [15.0 percent]) and the placebo group. The incidence of adverse effects did not differ significantly between the placebo group and either enoxaparin group. By day 110, 50 patients had died in the placebo group (13.9 percent), 51 had died in the 20-mg group (14.7 percent), and 41 had died in the 40-mg group (11.4 percent); the differences were not significant.

CONCLUSIONS

Prophylactic treatment with 40 mg of enoxaparin subcutaneously per day safely and effectively reduces the risk of venous thromboembolism in patients with acute medical illnesses.

Applying risk assessment models in orthopaedic surgery: effective risk stratification

Deep vein thrombosis (DVT) and pulmonary embolism remain important causes of morbidity and mortality. Without prophylaxis, at least 60% of patients undergoing orthopaedic or trauma surgery develop DVT, and the rate may still be as high as 20-45% even with the best prophylaxis available. The rate of thrombosis may be reduced by wider use of established prophylactic measures and targeting more intense prophylaxis to very-high-risk patients. Novel agents such as pentasaccharides and recombinant hirudins may provide more effective prophylaxis in very-high-risk settings, but their optimal use requires accurate assessment of thromboembolic risk. Risk levels are influenced both by the clinical setting and patient factors, such as obesity and malignancy. There is now growing interest in the influence of molecular risk factors, including acquired thrombophilias and congenital coagulation disorders. Activated protein C resistance and hyperhomocysteinaemia have been recently identified as potential risk factors. Further investigations are needed to clarify the individual contribution of different clinical and molecular factors to overall thromboembolic risk, and the effects of interactions between them. Screening for clotting disorders and other additional risk factors may assist identification of very-high-risk patients and allow appropriate targeting of intensive prophylactic therapy.

Continuous venovenous high-flux dialysis in multiorgan failure: a 5-year single-center experience

The objective of this study was to determine the outcome of acute renal failure (ARF) treated by continuous venovenous high-flux dialysis in patients with ventilator-dependent respiratory failure treated in a single center and to examine the importance of primary diagnosis in determining survival. We retrospectively reviewed 408 consecutively treated patients in the multidisciplinary intensive care unit (ICU) of a large teaching hospital. All ventilated patients requiring dialysis support over a 5-year period (January 1, 1991 to December 31, 1995) were included in the study. Patient age, APACHE II score, primary diagnosis, inotrope requirement, and survival to discharge from the ICU, from the hospital, and at 6 months were recorded for 408 consecutively treated patients. The mean age was 54 years, the median APACHE II score was 29, and the ICUs, hospital, and 6-month survival rates were 48%, 38%, and 36%, respectively. Inotropic support was required in 75%. Liver disease was the primary diagnosis in 35%. Logistic regression analysis indicated that increasing age and APACHE II, use of inotropes, and presence of liver disease were all associated with increased mortality. Eight percent of survivors (3% of the total population) required long-term renal replacement therapy. In conclusion, in our experience, continuous venovenous high-flux dialysis can be universally adopted in the ICU management of ARF associated with multiorgan failure. Patient survival is related to primary diagnosis, and a knowledge of case mix is essential in considering outcome of ARF in any reported series.

Risk factors for bleeding in major abdominal surgery using heparin thromboprophylaxis

BACKGROUND

Patients undergoing major abdominal surgery are at risk of both bleeding and thrombotic complications and usually receive heparin thromboprophylaxis.

PATIENTS AND METHODS

Risk factors for perioperative bleeding were examined in 3,809 patients in a double-blind, randomized trial investigating heparin thromboprophylaxis. The risk factors were modeled by logistic regression, and a risk score was calculated using the significant factors in the model.

RESULTS

Bleeding was associated with the following factors in the model, given as adjusted odds ratios (ORa [95% confidence interval]): male sex (ORa 1.68 [1.21 to 2.34] P = 0.003), malignancy (ORa 1.69 [1.21 to 2.34] P = 0.008), gynecological surgery (ORa 1.62 [1.12 to 2.35] P = 0.011), and complex surgery (ORa 2.7 [2.02 to 3.62] P < 0.001). The risk of excessive bleeding for 0, 1, 2, and 3 risk factors was 2%, 6%, 11%, and 21%, respectively.

CONCLUSIONS

The recognition of patients with these risk factors associated with perioperative bleeding should result in increased vigilance and may lead to modification of surgical and medical therapy.

Nitric oxide: description of a pipeline delivery system

We describe a pipeline system suitable for the delivery of nitric oxide gas to an 18-bed intensive care unit. The pipeline was developed and installed according to the current UK regulations HTM 2022, which relates to the supply of piped medical gases. Where HTM 2022 did not specify the appropriate standard, we consulted widely to achieve a safe solution. We continue to monitor all aspects of the performance of the pipeline to ensure safe operating practices and recommend changes to the standards.

Efficacy and safety of a low-molecular-weight heparin and standard unfractionated heparin for prophylaxis of postoperative venous thromboembolism: European multicenter trial

A randomized, double-blind multicenter trial was performed to compare the safety and efficacy of a new low-molecular-weight heparin (LMWH) (LU 47311, Clivarine) and standard unfractionated heparin for the prophylaxis of postoperative venous thromboembolism. Altogether 1351 patients scheduled to undergo abdominal surgery were included. Main outcome measures included the incidence of thromboembolic events (deep vein thrombosis, pulmonary embolism, or both) and bleeding complications, including wound hematoma. A total of 655 patients received 1750 anti-Xa IU of LMWH plus a placebo injection daily; 677 patients received 5000 IU of unfractionated heparin (UFH) twice a day. Both drugs were found to be equally effective, as 4.7% of patients in the LMWH group and 4.3% in the UFH group developed postoperative thromboembolic complications. However, the incidence of bleeding complications was significantly reduced in the LMWH group: 55 (8.3%) patients in the LMWH group and 80 (11.8%) in the UFH group developed bleeding complications, a relative risk (RR) of 0.70 (95% CI 0.51-0.97;p = 0.03); wound hematoma occurred in 29 (4.4%) of the LMWH group compared with 55 (7.7%) in those in the UFH group for an RR of 0.57 (95% CI 0.37-0.88;p = 0.01). This study confirmed that a very low dose of 1750 anti-Xa IU daily of this new LMWH is as effective as 10,000 IU of UFH for preventing postoperative deep vein thrombosis. At this dose its administration is associated with a significant reduction in the risk of bleeding including wound hematoma.

Low-molecular-weight heparin versus warfarin for prevention of recurrent venous thromboembolism: a randomized trial

A group of 105 consecutive patients with venographically proved major acute deep vein thrombosis (DVT) were randomized in an open prospective study to evaluate the comparative efficacy and safety of a fixed dose of subcutaneous low-molecular-weight heparin (LMWH) and warfarin for the prevention of recurrent venous thromboembolism. Four patients developed venographically proved recurrent DVT during the 3 months of treatment: three in the LMWH group and one in the warfarin group. Nonfatal pulmonary embolism occurred in two patients in the LMWH group and in one in the warfarin group. Five of the 55 patients (10%) in the warfarin group and none of the 50 patients in the LMWH developed bleeding complications (two-tailed Fisher exact test, p = 0.06). A preliminary assessment of the costs indicated that treatment with LMWH was less expensive by Pounds 900 per patient than warfarin. In conclusion, the fixed daily dose of LMWH and the adjusted dose of warfarin therapy were of similar efficacy in preventing recurrence of DVT. However, warfarin therapy, despite strict laboratory control, is associated with more frequent side effects and is expensive. Another study with a higher dose of LMWH is recommended.

The changing pattern of venous thromboembolic disease

A review of 14,667 necropsy reports for every year from 1965 to 1990 and 6,436 diagnostic venograms performed from 1976 to 1990 was undertaken at a single teaching hospital. A progressive reduction in the percentage of necropsies reporting fatal pulmonary embolism from 6.1 to 2.1%, occurred over the 25-year period (chi(2) tests for linear trend with time p < 0.00001). Over the last decade, there has been a significant reduction in the rate of venographically diagnosed postoperative deep vein thrombosis (DVT) from 49.9 to 24.7 per 100,000 population (p < 0.0001) which was in marked contrast to the constant rate of non-postoperative DVT. Our findings suggest that the introduction of thromboprophylactic measures, in addition to changes in hospital practice, may have had a highly significant effect on the pattern of this serious, but potentially avoidable disease.

Patients at risk of venous thromboembolism--clinical results with reviparin

Perioperative thromboembolism can be effectively prevented by low-dose heparin. However, its clinical benefit is limited, due to the risk of bleeding, the need for multiple daily doses, infrequent disorders of platelet function and other potential side effects. Low molecular weight heparin (LMWH) was developed with the aim that the antithrombotic efficacy of heparin could be maintained, while the risk of bleeding and other side effects would be reduced. Prior to recent studies, the anticipated clinical benefit of LMWH remained a controversial issue. We have reviewed the clinical pharmacology and the results of several prospective trials using reviparin a LMWH which has been compared with unfractionated heparin (UFH) and another LMWH. The efficacy and safety of reviparin was examined in the prevention of venous thromboembolism in high risk patients undergoing elective major abdominal and hip surgery. The results of these clinical trials show that reviparin is as effective as UFH in preventing venous thromboembolism whilst having a lower incidence of bleeding complications. Of major significance was the finding that a very low dose of reviparin, namely 1750 anti-Xa IU once daily, was found to be as effective as UFH in preventing deep vein thrombosis whilst having a significantly lower incidence of bleeding complications in patients undergoing major abdominal surgery. Reviparin has also been shown to be effective and safe as enoxaprin in patients undergoing elective hip surgery. Further clinical trials are required to test different dosage regimens as a thromboprophylactic agent in high risk patients. It is possible that reviparin and other LMWHs with similar pharmacological properties may have an important clinical benefit over earlier compounds. However, this needs to be assessed in large scale, double-blind, randomised clinical trials.