Interrupted Procedure Research Articles

Impact of Intermittent Intraoperative Neuromonitoring (IONM) on the Learning Curve for Total Thyroidectomy by Residents in General Surgery.

Recurrent laryngeal nerve (RNL) identification constitutes the standard in thyroidectomy. Intraoperative nerve monitoring (IONM) has been introduced as a complementary tool for RLN functionality evaluation. The aim of this study is to establish how routine use of IONM can affect the learning curve (LC) in thyroidectomy. Patients undergoing total thyroidectomy performed by surgery residents in their learning curve course in 2 academic hospitals, were divided into 2 groups: Group A, including 150 thyroidectomies performed without IONM by 3 different residents, and Group B, including 150 procedures with routine use of intermittent IONM, by other 3 different residents. LC was measured by comparing operative time (OT), its stabilization during the development of the LC, perioperative complication rate. As previously demonstrated, the LC was achieved after 30 procedures, in both groups, with no differences due to the use of IONM. Similarly, there were no significant differences among the 2 groups, and between subgroups independently matched, for both OT and complications, even when comparing RLN palsy. Direct nerve visualization and IONM assessment rates were comparable in all groups, and no bilateral RLN palsy (transient or permanent) were reported. No case of interrupted procedure to unilateral lobectomy, due to evidence of RLN injury, was reported. The study demonstrates that the use of IONM thyroid surgery, despite requiring a specific training with experienced surgeons, does not particularly affect the learning curve of residents approaching this kind of surgery, and for this reason its routine use should be encouraged even for trainees.

Script-Fading Procedures for the Acquisition of Wh-Question Skills in Children with Autism Spectrum Disorder

This study examined the effects of script and script-fading procedures for wh-question skills in two children with autism spectrum disorder. It also examined the effectiveness of a behavioral chain interruption procedure, as an establishing operation (EO) manipulation strategy to increase the reinforcement value of the information obtained via questions. The behavioral chain used in the intervention was a setting in which the participants played their preferred games with a therapist. Consequently, the two participants showed acquisition of five question behaviors, including four wh-questions. They also showed maintenance of the question-asking behaviors in the follow-up phase after the intervention. In addition, one of the two participants showed generalization of question-asking behaviors in which he prepared for his studies without any intervention. The results are discussed in terms of the combined effects of the script and script-fading, and behavior chain interruption procedures, as well as the use of persistent prompts to facilitate generalization and maintenance.

Analysis of influence of a novel inductive fault current limiter on the circuit breaker in 500 kV power system

A contribution to the engineering application of a proposed 500-kV fault current limiter (FCL) is presented. A new type of FCL composed of a highly coupled split reactor (HCSR) and fast switches is proposed. When the circuit breaker (CB) in series with the FCL in the 500-kV power system interrupts the limited fault current, the rate of rise of the recovery voltage (RRRV) reaches a value much higher than the rated value. Based on a simplified equivalent single-phase circuit, the influence of the new FCL on the interruption procedure of the CB is simulated and discussed. The simulation results show that the high RRRV is caused by high-frequency resonant oscillations between the HCSR and its parasite capacitance. Analysis indicates that when the reactance of the FCL is close to the short circuit reactance of the system, the RRRV will reach the highest value. To solve this issue, we proposed installing a shunt capacitor with the FCL. Simulation results showed that the RRRV under all fault modes could be restrained to below the rated value by introducing a certain shunt capacitor.

Stroke increases the expression of ACE2, the SARS-CoV-2 binding receptor, in murine lungs

BackgroundThe newly emerged severe acute respiratory syndrome coronavirus (SARS-CoV-2) has caused a worldwide pandemic of human respiratory disease. Angiotensin-converting enzyme (ACE) 2 is the key receptor on lung epithelial cells to facilitate initial binding and infection of SARS-CoV-2. The binding to ACE2 is mediated via the spike glycoprotein present on the viral surface. Recent clinical data have demonstrated that patients with previous episodes of brain injuries are a high-risk group for SARS-CoV-2 infection. An explanation for this finding is currently lacking. Sterile tissue injuries including stroke induce the release of several inflammatory mediators that might modulate the expression levels of signaling proteins in distant organs. Whether systemic inflammation following brain injury can specifically modulate ACE2 expression in different vital tissues has not been investigated. MethodsFor the induction of brain stroke, mice were subjected to a surgical procedure for transient interruption of blood flow in the middle cerebral artery for 45 min and sacrificed after 1 and 3 days for analysis of brain, lung, heart, and kidney tissues. Gene expression and protein levels of ACE2, ACE, IL-6 and IL1β were measured by quantitative PCR and Western blot, respectively. The level of soluble ACE2 in plasma and bronchial alveolar lavage (BAL) was measured using an immunoassay. Immune cell populations in lymphoid organs were analyzed by flow cytometry. Post-stroke pneumonia in mice was examined by bacterial cultures from lung homogenates and whole blood. ResultsStrikingly, 1 day after surgery, we observed a substantial increase in the protein levels of ACE2 in the lungs of stroke mice compared to sham-operated mice. However, the protein levels of ACE2 were found unchanged in the heart, kidney, and brain of these animals. In addition, we found increased transcriptional levels of alveolar ACE2 after stroke. The increased expression of ACE2 was significantly associated with the severity of behavioral deficits after stroke. The higher protein levels of alveolar ACE2 persisted until 3 days of stroke. Interestingly, we found reduced levels of soluble ACE2 in plasma but not in BAL in stroke-operated mice compared to sham mice. Furthermore, stroke-induced parenchymal and systemic inflammation was evident with the increased expression of IL-6 and IL-1β. Reduced numbers of T-lymphocytes were present in the blood and spleen as an indicator of sterile tissue injury-induced immunosuppression. ConclusionsWe demonstrate specific augmented alveolar ACE2 levels and inflammation in murine lungs after experimental stroke. These pre-clinical findings suggest that patients with brain injuries may have increased binding affinity to SARS-CoV-2 in their lungs which might explain why stroke is a risk factor for higher susceptibility to develop COVID-19.

Prototype Current-Limiting Hybrid DC Circuit Breaker Incorporating a Fuse and a Semiconductor Device

Owing to the increased demand for DC interruption, a prototype current-limiting hybrid DC circuit breaker incorporating a fuse and a semiconductor device was developed, based on a completely novel design concept. Recently, hybrid DC breakers have been attracting attention because of their low conduction loss and high-speed current interruption capability. The superiority of this hybrid DC circuit breaker lies in the simultaneous use of the high-speed current-limiting performance of the fuse and the highly reliable current-interruption performance of the semiconductor device. Furthermore, the hybrid DC circuit breaker performs the current interruption without any mechanical contact, thus preventing any delay in operation induced by the mechanical contact. The feasibility of the proposed concept was demonstrated by the successful application of the circuit breaker in a 1 kA fault current interruption procedure. Hence, the current-limiting hybrid DC circuit breaker is suitable for low voltage and medium voltage DC system protection. As the fuses and semiconductor modules progress, the hybrid DC circuit breaker may also adapt to HVDC systems.

Research on the breaking branch for a hybrid DC circuit breaker in±500 kV voltage‐sourced converter high‐voltage direct current grid

In order to construct the voltage-sourced converter high-voltage direct current grids, the high capacity direct current circuit breakers (DCCBs) are in demand. The hybrid DCCB has been the mainstream proposal, where the high-voltage solid-state switch (HVSS) is the key component for breaking the final fault current. Investigating the current commutation between the breaking branch and energy-absorbing branch, a hybrid DCCB with repositioned current commutation module (CCM) and redesigned HVSS is proposed in this study. By analysing the equivalent circuit of the CCM and HVSS, the detailed transient stages during current interruption procedure have been revealed, and the comparisons of different topologies for HVSS are made in-depth. The repositioned CCM can greatly decrease the transient voltage stress for HVSS and CCM whilst the improved HVSS including metal oxide varistor can maintain better interruption performances. Then the actual prototypes are developed to verify the effectiveness of the improved hybrid DCCB topology. In the end, a 500 kV DCCB is realised based on the proposed HVSS, which can ensure the reliability and convenience of the hybrid DCCB.

A systematic review of the effectiveness of behavioural treatments for pica in youths.

Pica is the persistent consumption of non-nutritive, nonfood substances and is associated with adverse health complications. However, there is limited research on interventions for pica in youth. The objective of this study is to systematically review the empirical evidence for the effectiveness of behavioural interventions for pica in children and adolescents and to generate treatment recommendations. A systematic search yielded 823 articles extracted from five databases: CINALH, Family and Society Studies Worldwide, Medline, PsycINFO, and Web of Science. Two reviewers completed initial sorting based on article titles and abstracts. Five reviewers completed sorting based on full article review. Thirty articles were included and double coded for demographic information, co-morbid conditions, and intervention characteristics. These studies were case studies involving behavioural treatments for pica. Seventeen behavioural interventions were categorized into four treatment approaches: reinforcement-based, response interruption, "other" interventions, and punishment-based procedures. Interventions that resulted in near-zero rates of pica were deemed effective. Findings showed support for contingent reinforcement, discrimination training as part of a combination treatment, physical restraint, time out, and contingent aversive stimulus. No evidence supported the effectiveness of response interruption procedures, including response blocking and visual facial screen. Other coded procedures did not appear effective. We recommend that the least restrictive procedures are implemented first, including a combination treatment with contingent reinforcement and discrimination training. As needed, more restrictive procedures can be added to the treatment package. This review will facilitate future empirical work and assist clinicians with treatment options for pica in youth. High-quality trials are needed.

Effective reduction in vocal stereotypy across natural settings through response interruption and redirection and the potential for maintained effects1

Q (1) What are the effects of 5-min response interruption and redirection (RIRD) procedure on vocal stereotypy across settings?(2) What are the immediate and subsequent effects of RIRD on vocal ste...

Disclosing and Locating Concurrency Bugs of Interrupt-Driven IoT Programs

The Internet of Things (IoT) is envisioned as a distributed network formed by many end devices, e.g., the motes of wireless sensor network (WSN). These important IoT end devices enable ubiquitous sensing of environments and provide reliable services for mission-critical applications. However, programs running on WSN devices are typically interrupt-driven and prone to interrupt-induced concurrency bugs, which are primarily caused by erroneous interleavings among interrupt procedure instances (IPIs) (namely, executions of interrupt processing logic). In this paper, we use a set of dynamic bug patterns to characterize the concurrency bugs due to buggy access-interleavings among IPIs to shared resources, including shared memory locations and shared communication channels. By matching the above bug patterns, a dynamic analysis approach called disclosing and locating concurrency bugs of interrupt-driven IoT programs based on dynamic bug patterns (Daemon) is proposed to automatically detect and locate concurrency bugs in WSN programs. A GUI tool of Daemon is developed. As the empirical studies exhibit, the tool can discover concurrency bugs effectively and locate the buggy source lines visually.

Analyzing and Disentangling Interleaved Interrupt-Driven IoT Programs

In the Internet of Things (IoT) community, wireless sensor network (WSN) is a key technique to enable ubiquitous sensing of environments and provide reliable services to applications. WSN programs, typically interrupt-driven, implement the functionalities via the collaboration of interrupt procedure instances (IPIs, namely executions of interrupt processing logic). However, due to the complicated concurrency model of WSN programs, the IPIs are interleaved intricately and the program behaviors are hard to predicate from the source codes. Thus, to improve the software quality of WSN programs, it is significant to disentangle the interleaved executions and develop various IPI-based program analysis techniques, including offline and online ones. As the common foundation of those techniques, a generic efficient and real-time algorithm to identify IPIs is urgently desired. However, the existing instance-identification approach cannot satisfy the desires. In this paper, we first formally define the concept of IPI. Next, we propose a generic IPI-identification algorithm, and prove its correctness, real-time, and efficiency. We also conduct comparison experiments to illustrate that our algorithm is more efficient than the existing one in terms of both time and space. As the theoretical analyses and empirical studies exhibit, our algorithm provides the groundwork for IPI-based analyses of WSN programs in IoT environment.

Reducing Public Masturbation in Individuals With ASD: An Assessment of Response Interruption Procedures.

Individuals with autism may engage in sexual behavior at inappropriate times and/or in inappropriate places. The current study investigated the effects of response interruption and redirection (RIRD) and response interruption (RI) on public masturbation (PM) of children and adolescents with autism. Initial assessments showed that PM was maintained by automatic reinforcement. During the treatment evaluation phase, we compared RIRD and RI to determine whether either procedure was successful in decreasing the duration of PM. In the RIRD condition, contingent on the occurrence of any PM the participant completed physical activities involving both hands (e.g., moving chairs, touching toes). In the RI condition, the therapist interrupted all instances of PM using physical and verbal prompts (e.g., saying in a neutral tone, "Stop that" and moving hands away from genitals). Both procedures were effective in decreasing the duration of PM but RI required fewer resources and less time. Clinical implications and suggestions for future research are reviewed.

Cholecystic Venous Anatomy: A Cadaveric Study with Implications for Portal Venous Interruption Procedure

The techniques of portal vein embolization (PVE) or ligation (PVL) have the goals of combining an induced atrophy of metastatic segments with the rapid relative compensatory hypertrophy of the postresection future liver remnant (FLR). Our study examines the anatomy of right-left hepatic lobar venous connections in the adult cadaver using corrosion cast analysis in an effort to define some of the inherent anatomical reasons why both PVL and PVE may be technically unsuccessful. Corrosion cast models of 215 cadaveric liver specimens were evaluated for hepatopetal venous blood flow, with a particular emphasis on cholecystic venous drainage patterns, including 57 cases prepared after lobar portal venous ligation. In 88.8 per cent of corrosion casts, there was a segmental venous communication between the gallbladder and all segments of the liver, except segment II. There was cystic vein drainage directly into a main lobar branch or directly into the portal vein itself in 11.2 per cent of cases. In all 57 cases, after portal lobar venous division, in situ cystic veins allowed persistent venous communication between lobes. Our cadaveric corrosion cast study has suggested that there is extensive intrahepatic cholecystic venous drainage to many segments of the liver. Perfusion from the gallbladder may potentially contribute to a limited response to procedures which interrupt the portal venous flow and could affect their capacity to induce an adequate FLR which would permit a wider hepatectomy.

Correlation of optical properties and interface morphology in type-II semiconductor heterostructures

(Ga,In)As/GaAs/Ga(As,Sb) and (Ga,In)As/GaAs/Ga(N,As) type-II double quantum well heterostructures have been grown by metal-organic vapor phase epitaxy. A growth interruption procedure was used to intentionally modify the morphology of the internal interfaces. The heterostructures were investigated using continuous wave and time-resolved photoluminescence as well as optical pump–optical probe spectroscopy. We find a correlation between the interface morphology and optical and kinetic properties. A growth interruption of about 120 s yielded substantially smoother interfaces both on vertical as well as lateral length scales. On the other hand a considerably enhanced type-II recombination time as well as a longer electron tunneling time are observed. We attribute this to a reduced interface localization in case of smoother interfaces.

An Approach to Identifying the Conditions Under Which Response Interruption Will Reduce Automatically Reinforced Problem Behavior

Response interruption is a common intervention for problem behavior maintained by automatic reinforcement, but this intervention is challenging for caregivers to implement with consistent fidelity. In the current study, we challenged the integrity of response interruption across two participants by examining carry over into conditions in which the procedure was not implemented, by removing the presence of an interventionist, and by introducing delays to implementation. The results indicated that these challenges severely compromised treatment efficacy. Conditions under which response interruption procedures are likely to be effective and possible strategies to increase the effectiveness of response interruption are discussed.

Lack of Difference In Co-Morbidities Associated with Deep Venous Thrombosis In Patients Undergoing Total Knee Replacement

AbstractAbstract 2578 Background:Thromboprophylaxis is the top challenge to patient safety practice in hospitals. Postoperative Deep vein thrombosis (DVT) and pulmonary embolism (PE) are the major cardiovascular killers in the surgical setting. In October 2008, Medicare designated DVT and PE occurring after total knee or hip replacement as ‘never events’, and indicated that they will not pay the incremental cost to manage the complication and has made the hospital acquired DVT/PE unacceptable and serious. There are however, limited data on factors contributing to DVT/PE in-patients undergoing total knee or hip replacement. Aim:To ascertain nationwide health care utilization and associated co-morbidities in Total knee replacement (TKR) recipients who do or do not develop DVT/PE. Methods:We used the year 2007, National Inpatient Sample (NIS) to analyze the post operative occurrence of DVT/PE after TKR. We used an analysis similar to AHRQ's Patient Safety Indicator number – 12 (PSI 12) which is Postoperative Pulmonary Embolism or Deep Vein Thrombosis but restricted our analysis only to TKR. We intended to capture cases of postoperative venous thromboses and embolism - specifically, pulmonary embolism and deep venous thrombosis. For our analysis we separated TKR into 2 groups; one without DVT/PE and the other with DVT/PE. We analyzed all surgical discharges age 18 years and older with an ICD-9-CM code for an operating room procedure TKR (ICD-9 8154). From this we excluded those who have principal diagnosis of DVT/PE, as these patients are likely to have had PE/DVT present on admission and not because of TKR and also where a procedure for interruption of vena cava (IVC filter) (ICD-9 387) occurs before or on the same day as the first operating room procedure as these patients likely had DVT/PE even before TKR. We then created a subset from the first group, with discharges ICD-9-CM codes for deep vein thrombosis or pulmonary embolism in any secondary diagnosis field and thus defined the group of patients who developed DVT/PE after TKR. We used the following ICD-9 codes to represent DVT (ICD-9 codes 451.11, 451.19, 451.2, 451.81, 451.9, 453.40, 453.41, 453.42, 453.8, 453.9) and PE (ICD-9 codes 415.1–415.19). IBM SPSS Statistics 18 was used for data mining and analysis. Result:In the year 2007, there were 550,770 discharges with a procedure for TKR. After excluding primary diagnosis of DVT/PE and IVC filter, we had 550228 as our working number. Of these, 5454 discharges had a secondary diagnosis of DVT/PE (Rate - 10 new cases per 1000 TKR procedures). Demographics and health care utilization between those who did or did not develop are described in Table 1. Co-morbidities associated with those who did or did not develop DVT are described in (Table 2).Demographic and Health Care UtilizationTKR with Secondary diagnoses of DVT/PETKR without Secondary diagnoses of DVT/PEMedian Age (years)6967Proportion with Medicare as Primary Payer %61.856.3Median Length of Stay (days)63Median Charges (in thousands of dollars)48,72536,075Mortality (%)1.70.1Patient LocationCentral Metro (%)29.122.7Micropolitan county (%)69RaceWhite (%)84.185.1Black (%)6.76.8IncomeLow (%)19.322.6High (%)30.624.9Table 1Co-morbidities associated with those who did or did not develop DVT/PE following TKRCo morbiditiesTKR with Secondary diagnoses of DVT/PETKR without Secondary diagnoses of DVT/PEAtrial fibrillation (AF)Congestive Heart Failure (CHF)Hypertension60.3%62.2%Hyperlipidemia21.5%21.8%Urinary Tract infection (UTI)7%2.4% Conclusion:DVT & PE are major avoidable complications of Total Knee replacement and are associated with significant mortality and health care costs. These data demonstrate that there may not be any significant differences in age and associated co-morbidities between those who do or do not develop DVT/PE following total knee replacement except for UTI which can be attributed to the difference in length of stay. The absence of serious co-morbidities like AF and CHF in both groups suggest those with serious co-morbidities may not be receiving total knee replacement. That no differences were noticed in associated co-morbidities among those who did or did not develop DVT/PE following TKR provide the rationale for further study of factors contributing to this serious complication of TKR. Such studies may inform future strategies for prevention of post-operative DVT/PE. Disclosure:No relevant conflicts of interest to declare.

Evidence‐Based Practice in the Classroom: Evaluating a Procedure for Reducing Perseverative Requesting in an Adolescent with Autism and Severe Intellectual Disability

Management of inappropriate behaviour is a major priority in special education. Evidence‐based practice dictates that interventions to reduce inappropriate behaviour should be evaluated at the individual level to demonstrate their efficacy in the classroom. This study illustrates the evaluation of an evidence‐based procedure (response interruption) for reducing perseverative requesting in an adolescent boy with autism and severe intellectual disability. The boy used a speech‐generating device to request snacks during baseline and response interruption conditions. During both conditions, the boy had to wait 30 seconds while the snack was being prepared. Requests that occurred during this wait interval were defined as perseverative. Intervention involved blocking perseverative requests and prompting the child to wait. An ABAB design was used to evaluate the effects of the response interruption procedure. The results demonstrated that response interruption effectively reduced perseverative requesting, while maintaining appropriate requesting at other times. The study illustrates how special educators might evaluate evidence‐based practice in the classroom.

Evidence-Based Practice in the Classroom: Evaluating a Procedure for Reducing Perseverative Requesting in an Adolescent with Autism and Severe Intellectual Disability

Management of inappropriate behaviour is a major priority in special education. Evidence‐based practice dictates that interventions to reduce inappropriate behaviour should be evaluated at the individual level to demonstrate their efficacy in the classroom. This study illustrates the evaluation of an evidence‐based procedure (response interruption) for reducing perseverative requesting in an adolescent boy with autism and severe intellectual disability. The boy used a speech‐generating device to request snacks during baseline and response interruption conditions. During both conditions, the boy had to wait 30 seconds while the snack was being prepared. Requests that occurred during this wait interval were defined as perseverative. Intervention involved blocking perseverative requests and prompting the child to wait. An ABAB design was used to evaluate the effects of the response interruption procedure. The results demonstrated that response interruption effectively reduced perseverative requesting, while maintaining appropriate requesting at other times. The study illustrates how special educators might evaluate evidence‐based practice in the classroom.

21. Dissecting cryoinjury using simulations of an interrupted freezing procedure

21. Dissecting cryoinjury using simulations of an interrupted freezing procedure

Cervical Dural Arteriovenous Fistula Presenting With Brainstem Dysfunction

We present a rare case of cervical dural arteriovenous fistula (C-DAVF) presenting with brainstem dysfunction. We discuss the details of the case and review previous articles on C-DAVF. Our case study illustrates the relation between uncommon neurologic findings and altered hemodynamics resulting from the anatomic features of the neural pathway. Based on a review of 31 cases of C-DAVFs published since 1990 (30 patients, including our own), we sought to determine which surgical treatment for C-DAVF, endovascular surgery, or direct interruption of the draining vein, is more effective. A combination of endovascular techniques and direct interruption procedures was successful in curing the C-DAVF in our patient. The selection between endovascular surgery and surgical interruption in the treatment of C-DAVF is controversial. We sought to identify the characteristics and surgical methods most closely associated with complete cure for C-DAVF. RESULTS.: According to the reports on 31 cases of C-DAVF treated surgically (including our own), 20 DAVFs were managed by open surgery with interruption, 8 were treated by endovascular surgery, and 3 underwent a combined open and endovascular approach. Twenty-one patients showed symptomatic improvement or stabilization without additional treatment during the postsurgical course. Surgical revisions were performed in 3 patients (10.0%) (including the present case), all of whom initially underwent endovascular surgery. None of the cases treated by surgical interruption of the draining vein showed signs of recurrence. Surgical interruption of the draining vein is more effective than endovascular surgery in bringing about an absolute cure for C-DAVF. In exceptional cases, however, endovascular surgery is the preferred treatment. This is particularly so for elderly or medically compromised cases with contraindications against general anesthesia, as well as for moribund cases which, like our own case, present with rapidly deteriorating neurologic status on admission.

Prevention of venous thromboembolism

The aim of prophylaxis in venous thromboembolism is firstly to prevent fatal pulmonary embolism and secondly to reduce the morbidity associated with deep vein thrombosis and the post-phlebitic limb. Particularly high-risk groups are identifiable and include those over 60 years of age undergoing major surgery, patients with malignancy and those undergoing hip operations. Low-dose subcutaneous heparin (5000 U s.c. commenced two hours preoperatively and continued eight to twelve hourly until the patient is fully mobile) is unequivocally effective in preventing deep vein thrombosis in medical and surgical patients and, most importantly, significantly reduces the incidence of fatal postoperative pulmonary embolism and total mortality. Furthermore, in established deep vein thrombosis, low-dose heparin limits proximal clot propagation, which is the prelude to pulmonary embolism. Despite this, surveys have demonstrated an alarming deficiency amongst clinicians in the application of measures to prevent venous thromboembolism. Heparin prophylaxis carries a small risk of increased bleeding complications, mostly evidenced by the frequency of wound haematoma rather than major haemorrhage. Low molecular heparin fragments (e.g. Fragmin, Choay, Enoxaprin) are now emerging as useful alternative agents, having the advantage of once daily administration and yet providing similar efficacy in the prevention of deep vein thrombosis. However, protection against fatal pulmonary embolism has yet to be demonstrated. Mechanical methods of prophylaxis designed to counteract venous stasis, such as graduated elastic compression stockings, are also beneficial in protection against deep vein thrombosis but by themselves do not achieve such consistently good prophylaxis as low-dose heparin. However, clinical trials with combinations of mechanical methods and low-dose heparin indicate that this may be the optimum approach to very high-risk patients. In the presence of established acute deep vein thrombosis, anticoagulant therapy is the mainstay in preventing pulmonary embolism. Vena caval interruption procedures should be reserved for patients in whom anticoagulation is contraindicated or for those who develop recurrent pulmonary embolism despite adequate anticoagulation.