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Biomedical subjects

M C Proctor

Publications and source records attributed to M C Proctor.

At least 19 recordsLinked to original sources
PubMed2001

Recurrent thromboembolism in patients with vena cava filters.

BACKGROUND: Patients with venous thromboembolic disease are treated with anticoagulation or vena cava filter placement to prevent pulmonary embolism. A recent report suggested that filter placement may increase the risk of recurrent deep venous thrombosis (DVT) and prompted a review of our experience. METHODS: Prospectively collected data on 2109 consecutive patients receiving filters were evaluated for recurrent thromboembolism, vena cava occlusion, or venous stasis ulceration. Outcomes were stratified and analyzed according to the use of anticoagulants at the time of insertion and at follow-up. Incidence rates were also compared with reports in the literature. RESULTS: Of 1191 patients with DVT at filter placement, complete follow-up data at a mean of 9 years were available for 465. Recurrent DVT was found in 12% of the 241 patients who were given anticoagulants and 15% of the 224 who were not (P >.05). We also failed to find a significant association between the use of anticoagulation and the incidence of pulmonary embolism (2%), stasis ulceration (2%), and vena cava occlusion (0.0). CONCLUSIONS: Recurrent DVT in patients with existing thromboembolic disease is not an unexpected event, which, in our experience, is not associated with anticoagulant or filter use. Anticoagulation should be used when possible to treat existing DVT to reduce thrombus progression and potentially to reduce subsequent complications but does not seem to reduce the rate of recurrent DVT. Rates of recurrent thromboembolism were consistently less than the 20% to 50% reported in the literature.

Adolescent↗
PubMed2000

The risk assessment profile score identifies trauma patients at risk for deep vein thrombosis.

BACKGROUND: The identification of trauma patients at risk for the development of deep venous thrombosis (DVT) at the time of admission remains difficult. The purpose of this study is to validate the risk assessment profile (RAP) score to stratify patients for DVT prophylaxis. METHODS: All patients admitted from November 1998 thru May 1999 were evaluated for enrollment. We prospectively assigned patients as low risk or high risk for DVT using the RAP score. High-risk patients received both pharmacologic and mechanical prophylaxis. Low-risk patients received none. Surveillance duplex Doppler scans were performed each week of hospitalization or if symptoms developed. Hospital charges for prophylaxis were used to determine the savings in the low-risk group. Statistical differences between the risk groups for each factor of the RAP and development of DVT were determined by the chi-squared test, with significance at a probability value of less than .05. RESULTS: There were 102 high-risk (64%) and 58 low-risk (36%) individuals studied. Eleven of the high-risk group (10.8%) experienced the development of DVT (asymptomatic, 64%). None of the low-risk group was diagnosed with DVT. Five of the 16 RAP factors were statistically significant for DVT. Eliminating prophylaxis and Doppler scans in low-risk patients resulted in a total savings of $18,908 in hospital charges. CONCLUSIONS: The RAP score correctly identified trauma patients at increased risk for the development of DVT. Despite prophylaxis, the high-risk group warrants surveillance scans. Withholding prophylaxis in low-risk patients can reduce hospital charges without risk.

Adult↗
PubMed2000

Prophylactic vena caval filters in trauma: the rest of the story.

OBJECTIVE: The purpose of this study was to describe outcomes for patients with trauma who had vena caval filters placed in the absence of venous thromboembolic disease (group P) and compare them with outcomes for patients with trauma who had filters placed after either deep venous thrombosis or pulmonary embolism (group T). DESIGN: The study is a case series of consecutive patients who received vena caval filters after traumatic injury. Data were collected prospectively at the time of filter placement from reports of diagnostic studies obtained for clinical indications and during the annual follow-up examinations. Event rate findings are based on objective tests. Data were obtained from the Michigan Vena Cava Filter Registry. RESULTS: Filters were placed in 385 patients with trauma; 249 of these filters were prophylactic (group P). Event rates were similar in the two groups. New pulmonary embolism was diagnosed in 1.5% of the patients in group P and 2% of the patients in group T. Caval occlusion rates were 3.5% for group P and 2.3% for group T. In all, 15.6% of the patients in group P had deep venous thrombosis or pulmonary embolism after placement. The frequencies of lower extremity swelling and use of support hose were higher in group T than in group P (43% vs 25% and 25% vs 3.5%, respectively; P <.005). Outcomes were comparable in the two groups with respect to mechanical stability of the filter. CONCLUSIONS: The prophylactic indication for vena caval filter placement in patients with trauma is associated with a low incidence of adverse outcomes while providing protection from fatal pulmonary embolism. The current challenge is to limit the number of unnecessary placements through improved methods of risk stratification.

Adolescent↗
PubMed2000

The percutaneous greenfield filter: outcomes and practice patterns.

OBJECTIVE: The percutaneous steel Greenfield filter (PSGF) is similar in appearance to the titanium Greenfield filter (TGF) but differs in the length and orientation of the attachment hooks and in the over-the-wire delivery system. Because these differences improve ease of insertion and attachment, they may affect patient outcomes and physician practices. The purpose of this study was to evaluate the performance of the PSGF relative to the TGF and to determine whether there had been a change in physician practices. METHODS: The Michigan Filter Registry contains data for a prospective cohort of 2188 patients with Greenfield filters. Procedural and long-term outcomes for patients with a PSGF were abstracted. These events were compared with rates for Registry patients who had a TGF. Trends for indication for placement, delivery route, and filter location were also compared with published series. RESULTS: Since 1995, 600 PSGFs have been placed in 599 patients. A 1-year mortality rate of 42% left 349 patients available for annual follow-up, and studies were completed for 231 (66%). Periprocedural events occurred in 2.5% of cases with associated morbidity in 1.5%. The rate of new pulmonary embolism was 2.6%, and vena caval patency was 98.3%. The combined rate of new venous thromboembolic events was 12.5%. Left-sided femoral vein placements increased to 20%, and the major indication for filter placement has become prophylaxis (46%). CONCLUSIONS: The PSGF is similar to the TGF with respect to patient outcomes, and it provides decreased rates of asymmetry along with excellent fixation. The flexible carrier system has allowed more frequent access through the left femoral vein. The ease of use and favorable patient outcomes have resulted in more frequent placement for prophylactic indications.

Adult↗
PubMed2000

Rapid recovery of photosystems on rewetting desiccation-tolerant mosses: chlorophyll fluorescence and inhibitor experiments.

In the mosses Racomitrium lanuginosum, Anomodon viticulosus and Rhytidiadelphus loreus, after a few days air dry, F:(v)/F:(m) reached, within the first minute of remoistening in the dark, two-thirds or more of the value attained after 40 min. A fast initial phase of recovery was completed within 10-20 min after which further change was slow. Initial recovery of Phi(PSII) in the light was somewhat slower, but was generally substantially complete within a similar time. Remoistening with 0.3 mM cycloheximide (CHX) or 3 mM dithiothreitol (DTT) made little difference to this short-term (40 min) recovery of either F:(v)/F:(m) or Phi(PSII); 3 mM chloramphenicol (CMP) had little effect on recovery of F:(v)/F:(m), but resulted in substantial (though not total) depression of Phi(PSII) and (14)CO(2) uptake. Effects of the protein-synthesis inhibitors and DTT were much more clearly apparent in longer-term experiments (>20 h) but only in the light. In the dark, the three inhibitors had at most only slight effects over periods of 60-100 h. In the light, CMP-treated samples of all three species showed a progressive decline of dark-adapted F:(v)/F:(m), falling to zero within 1-5 d (possibly due to blocking of the turnover of the D1 protein of PSII) and accelerated by DTT. CHX-treated samples showed a similar but slower decline. In the shade-adapted and relatively desiccation-sensitive Rhytidiadelphus loreus, slow recovery of F:(v)/F:(m) continued in the dark even in the presence of CMP and CHX for much of the 142 h of the experiment. The results indicate that in desiccation-tolerant bryophytes recovery of photosynthesis after periods of a few days air dry requires only limited chloroplast protein synthesis and is substantially independent of protein synthesis in the cytoplasm.

Adaptation, Physiological↗
PubMed2000

Current status of pulmonary embolism and venous thrombosis prophylaxis.

Prophylaxis for venous thromboembolism is an area that has received intense study in certain conditions, but less than adequate coverage in other areas. In considering who needs prophylaxis, patients are categorized into levels of risk. Clinical venous thromboembolism can be correlated to these levels of risk. Methods of prophylaxis include pharmacologic, mechanical, and combinations of these. Each category of surgical and medical patient requires specific types of prophylaxis. In certain orthopedic indications, the length of prophylaxis outlasts the inpatient hospital stay and may be as long as 1 month after discharge. Even with the best prophylaxis today, the incidence of deep venous thrombosis (DVT) and pulmonary embolism (PE) is decreased by only approximately 70% to 80%. Further developments should allow for greater declines in the rates of venous thromboembolism, with its subsequent short-term consequence of pulmonary embolism and lower extremity morbidity and long-term consequence of the disabling syndrome of chronic venous insufficiency (CVI).

Adult↗
PubMed2000

Indications for filter placement.

Indications for placement of a vena caval filter reflect the perception of efficacy and safety of these devices. The traditional indications include contraindications to or complications of anticoagulation. Over time, physicians have expanded these indications to include prophylactic placement in patients at high risk of pulmonary embolism. The decision to place a filter should be made only after weighing the risks and benefit in each situation. Long-term outcomes should be carefully evaluated.

Anticoagulants↗
PubMed2000

Filter complications and their management.

Complications from the use of vena caval filters are rare but can occur at placement, during other procedures, or late in follow-up. Placement problems such as bleeding from the insertion site or embolism from thrombus manipulation are largely avoidable. Technical difficulties with introduction, positioning, or misplacement have been minimized by use of flexible carriers and guidewires. However, later insertion of guidewires without fluoroscopy for line changes can lead to problems of entrapment. Filter capture of emboli can result in further thrombus propagation at that site or in filter obstruction. Management of these events requires adequate visualization to determine whether to use lytic therapy or a second filter. Late complications include filter strut fracture in 0.05% of cases and filter penetration, of even rarer functional significance. Pain that can be attributed to the filter has been found only in a single case of pelvic misplacement. The limited consequences of mechanical changes in the filter argue strongly against unnecessary interventions, which frequently result in an increase in morbidity.

Catheterization, Peripheral↗
PubMed1998

Suprarenal filter placement.

PURPOSE: This study was undertaken to determine the clinical outcomes for patients with Greenfield filters placed in the suprarenal (SR) inferior vena cava (IVC). METHODS: We collected data prospectively from annual follow-up evaluations of patients with filters. Patients underwent venous color-flow duplex examinations of the IVC and lower extremities, abdominal radiographs, and physical assessment. The outcomes for those patients with filters in the SR IVC were compared with the outcomes previously reported and with the outcomes for patients with filters in the infrarenal cava. RESULTS: SR placement accounted for 7.6% (148/1932) of all filter placements. Follow-up data were available for 73 placements, or 49%. No cases of renal dysfunction were related to filter placement. The rate of recurrent pulmonary embolism (PE) was 8%, and the rate of long-term caval occlusion was 2.7%. These rates did not differ statistically from the rates for patients with infrarenal filters (P > .05). Male patients tended to be older by 15 years, to have more recurrent PE, and to experience more filter migration (6 vs 2 mm). Failure of SR filters to prevent PE was associated statistically with the primary indication for placement. Recurrent PE was the indication in 5 of 6 patients who sustained PE after SR filter placement (P = .007). Filter limb fracture was seen only with the stainless-steel Greenfield filter. CONCLUSION: Greenfield filters placed above the renal vein provide protection from PE with a minimal risk of occlusion. Twenty-five years of experience with Greenfield filters shows that they are safe and effective both in young female patients of child-bearing potential and in all patients with appropriate indications for SR placement.

Female↗
PubMed1998

Assessment of apparent vena caval penetration by the Greenfield filter.

PURPOSE: To examine and elucidate the mechanisms for apparent "penetration" by Greenfield vena caval filters. METHODS: Two filters were placed in the inferior venae cavae (IVC) of four immature sheep and followed with cavography for 1 year. Two animals underwent computed tomography (CT) and laparoscopic examination. At necropsy, the vena cava and adjacent structures of all four animals were examined grossly and histologically. RESULTS: Based upon cavography and CT imaging, all filters appeared to penetrate the vena cava at 12 months. However, at laparoscopy, no hooks or limbs were exposed, and the pericaval tissues remained intact; each hook or limb was within the adventitia or encapsulated in scar tissue. Histology of the tissue at the hook sites revealed remodeling of the intimal surface of the IVC and thinning of the adventitia. CONCLUSIONS: Based upon these data, we hypothesize that the vena cava gradually adapts by medial and adventitial thinning and myointimal remodeling to the radial force exerted by a filter. This process allows increase in the filter base diameter while maintaining the integrity of the cava and protecting adjacent structures.

Animals↗
PubMed1997

An improved process for development and testing of vena caval filters: the percutaneous steel Greenfield filter.

BACKGROUND: The purpose of this study was to develop a reduced profile stainless steel Greenfield filter with an over-the-wire delivery system and to compare its performance with the existing Food and Drug Administration-approved Greenfield filters. In addition, we wanted to standardize a system for evaluating filter prototypes. METHODS: Percutaneous stainless steel filters with various hook configurations were evaluated for efficacy and safety in four in vitro modules designed to reproduce potential liabilities experimentally. Animal studies to assess thrombus capture and resolution, filter stability, migration, and hemodynamics were completed in 4 dogs and 38 sheep. RESULTS: Mathematical modeling suggested that hook angle was the most relevant factor in improving resistance to migration. Prototypes that varied with respect to hook length and angle were evaluated in both the in vitro testing unit and in sheep. The stainless steel filter with two downward directed hooks provided clot capture comparable with the current Greenfield filter, maintenance of flow, and resistance to fatigue and corrosion while providing significant resistance to migration and penetration (p < 0.05). CONCLUSIONS: The percutaneous stainless steel Greenfield filter with the alternating hook design provides a reduced profile device that can be placed over a wire to improve positioning. The use of a standardized testing system reduced both the time and cost of bringing this new device to the market.

Animals↗
PubMed1997

Limb asymmetry in titanium Greenfield filters: clinically significant?

PURPOSE: The purpose of this study was to determine the outcomes for patients with titanium Greenfield vena caval filters (TGFs) and, in particular, to evaluate the effect of filter leg distribution on recurrent pulmonary embolism (PE) and caval occlusion. METHODS: Physical examination, abdominal plain films, and duplex ultrasound examinations of the inferior vena cava and lower extremities were obtained annually and recorded in a Filter Database. RESULTS: Seven hundred eighty-three TGFs have been placed since 1989. Follow-up was available for 373 patients, or 65% of the surviving patients, over 1 to 84 months (mean, 33 months). Asymmetry was identified in 42 placements (5%), and 35 of these patients had at least one follow-up examination. The overall incidence of recurrent PE was 3.2% (12 of 373), whereas the caval patency rate was 97.8% (265 of 271). These outcomes were not significantly different for patients who had asymmetric filters (p = 0.1 and 0.18, respectively). CONCLUSIONS: Filter leg distribution does not appear to be associated with an increased incidence of recurrent PE or caval occlusion. These data support earlier in vitro findings. The long-term results with the TGF are comparable with the results of the original stainless steel Greenfield filter.

Female↗
PubMed1997

Pulmonary embolism: diagnosis, incidence and implications.

The purpose of this study was to determine the prevalence of pulmonary embolism at an academic tertiary care center, to identify the methods of diagnosis, and to characterize the outcomes for this population. A retrospective analysis of multiple data sources including records from the Medical Information System, and the Departments of Pathology, Radiology, Nuclear Medicine and Pharmacy were reviewed for all patients with positive reports of pulmonary embolism. These were verified by the medical records and a listing of all positive cases was developed. A total of 320 patients developed pulmonary embolism during the study period and 121 died before discharge. The prevalence was 3.5 cases per 1000 admissions, with a mortality of 1 per 1000 cases. Significant misclassification of patients and errors in rate estimation would have occurred if multiple sources of information were not used. Definitive diagnosis and appropriate treatment with a Greenfield filter was associated with improved early survival. By relying on ICD-9 coding, 80% of fatalities and 13% of patients with positive angiograms would have been missed.

Adult↗
PubMed1997

Clinical results of Greenfield filter use in patients with cancer.

The purpose of this report is to examine the outcomes for patients with an underlying diagnosis of malignancy who have had Greenfield vena caval filters placed for protection from pulmonary embolism, and to identify areas requiring further study. This was a retrospective review of data obtained from the Greenfield filter registry and the University of Michigan Tumor Registry for 166 patients treated at the University of Michigan Medical Center between January 1988 and June 1994. The 84 men and 82 women (mean age 57.8 years) had a mean survival time of 10 (range 1-68) months. This differs significantly from patients in the filter registry who do not have malignancy (P<0.0001). Some 51% experienced recurrence of their malignancy at a mean of 20 months; this timing corresponds to development of new or recurrent thrombembolism and filter placement. Distant metastases were present in 72% of patients at the time of filter placement. In conclusion, as anticipated, filter patients with malignancy have a significantly shorter survival time than those with other concurrent diseases. A temporal association between the progression of the malignancy and the occurrence of thromboembolism is observed in this population and requires further study. Future studies regarding the use of vena caval filters in these patients and the role of diagnostic screening for deep venous thrombosis and occult recurrence of malignancy should focus on efficacy, safety, cost and patient quality of life rather than on survival.

Cause of Death↗
PubMed1997

Posttrauma thromboembolism prophylaxis.

PURPOSE: The need to study methods of thromboembolism prophylaxis in high-risk trauma patients is well established. The purpose of this study was to evaluate the feasibility of a proposed study design, including current methods of prophylaxis, performance of a risk assessment profile scale, and the use of serial color-flow duplex studies in detecting deep venous thrombosis (DVT). METHODS: Patients were enrolled into the study, stratified as to their ability to receive anticoagulation and randomized to low-dose unfractionated heparin, low molecular weight heparin, pneumatic compression devices, or foot pumps with or without vena caval filters. Serial ultrasound scans were performed at designated intervals for 4 weeks. Pulmonary angiograms were obtained for clinical signs or symptoms of pulmonary embolism. RESULTS: Fifty-three patients, 32 male and 21 female patients with a mean age of 44 years, completed the study. The incidence of DVT was 43% (23 of 53 patients) and significantly higher in older patients. There were no pulmonary embolisms. Color-flow duplex proved to be a sensitive method for detecting both proximal and distal thrombi. The risk assessment profile for thromboembolism (RAPT) scale identified a group of patients with a high incidence of DVT. However, the occurrence of DVT was not correlated with the magnitude of the RAPT score. CONCLUSION: The ability to identify a population with a high incidence of thromboembolism by using the RAPT score to detect asymptomatic DVT, and the suggested advantage of low molecular weight heparin, all support the need for an appropriately powered randomized clinical trial.

Adult↗