Initiation Of Chemoprophylaxis Research Articles

Inability to predict subprophylactic anti-factor Xa levels in trauma patients receiving early low-molecular-weight heparin.

Standard low-molecular-weight heparin dosing may be suboptimal for venous thromboembolism prophylaxis. We aimed to identify independent predictors of subprophylactic Xa (subXa) levels in trauma patients treated under a novel early chemoprophylaxis algorithm. A retrospective analysis of trauma patients from July 2016 to June 2017 who received enoxaparin 40 mg twice daily and had peak Xa levels drawn was performed. Patients were divided into cohorts based on having a subXa (<0.2 IU/mL) or prophylactic (≥0.2 IU/mL) Xa level. In all, 124 patients were included, of which 38 (31%) had subXa levels, and 17 (14%) had Xa levels greater than 0.4 IU/mL. Of the subXa cohort, 35 (92%) had their dosage increased, and the repeat Xa testing that was done in 32 revealed that only 75% reached prophylactic levels. The median time to the initiation of chemoprophylaxis was 21.9 hours (interquartile range [IQR], 11.45-35.07 hours). Patients who were defined as having lower risk of having a complication as a result of bleeding had a shorter time to starting prophylaxis than those at higher risk (18.39 hours [IQR 5.76-26.51 hours] vs. 29.5 hours [IQR 16.23-63.07 hours], p < 0.01).There was no difference in demographics, weight, body mass index, creatinine, creatinine clearance, injury severity score, type of injury, weight-based dose, time to chemoprophylaxis, or bleeding complications between the cohorts. No independent predictors of subXa level were identified on multivariable logistic regression. A significant number of trauma patients fail to achieve prophylactic Xa levels. Intrinsic factors may prevent adequate prophylaxis even with earlier administration and higher dosing of low-molecular-weight heparin. Therapeutic, level IV.

The timing of venous thromboembolic events after spine surgery: a single-center experience with 6869 consecutive patients.

OBJECTIVE Venous thromboembolic events (VTEs), including both deep venous thrombosis (DVT) and pulmonary embolism, are a major cause of morbidity and mortality after spine surgery. Prophylactic anticoagulation, or chemoprophylaxis, can prevent VTE. However, the timing of VTEs after spine surgery and the effect of chemoprophylaxis on VTE timing remain underinvestigated. METHODS The records of 6869 consecutive spine surgeries were retrospectively examined. Data on patient demographics, surgical variables, hospital course, and timing of VTEs were collected. Patients who received chemoprophylaxis were compared with those who did not. Appropriate regression models were used to examine selection for chemoprophylaxis and the timing of VTEs. RESULTS Age (OR 1.037, 95% CI 1.023-1.051; p < 0.001), longer surgery (OR 1.003, 95% CI 1.002-1.004; p < 0.001), history of DVT (OR 1.697, 95% CI 1.038-2.776; p = 0.035), and fusion surgery (OR 1.917, 95% CI 1.356-2.709; p < 0.001) predicted selection for chemoprophylaxis. Chemoprophylaxis patients experienced more VTEs (3.62% vs 2.03% of patients, respectively; p < 0.001), and also required longer hospital stays (5.0 days vs 1.0 days; HR 0.5107; p < 0.0001) and had a greater time to the occurrence of VTE (median 6.8 days vs 3.6 days; HR 0.6847; p = 0.0003). The cumulative incidence of VTEs correlated with the postoperative day in both groups (Spearman r = 0.9746, 95% CI 0.9457-0.9883, and p < 0.0001 for the chemoprophylaxis group; Spearman r = 0.9061, 95% CI 0.8065-0.9557, and p < 0.0001 for the nonchemoprophylaxis group), and the cumulative incidence of VTEs was higher in the nonchemoprophylaxis group throughout the 30-day postoperative period. Cumulative VTE incidence and postoperative day were linearly correlated in the first 2 postoperative weeks (R = 0.9396 and p < 0.0001 for the chemoprophylaxis group; R = 0.8190 and p = 0.0003 for the nonchemoprophylaxis group) and the remainder of the 30-day postoperative period (R = 0.9535 and p < 0.0001 for the chemoprophylaxis group; R = 0.6562 and p = 0.0058 for the nonchemoprophylaxis group), but the linear relationships differ between these 2 postoperative periods (p < 0.0001 for both groups). CONCLUSIONS Anticoagulation reduces the cumulative incidence of VTE after spine surgery. The cumulative incidence of VTEs rises linearly in the first 2 postoperative weeks and then plateaus. Surgeons should consider early initiation of chemoprophylaxis for patients undergoing spine surgery.

Timing and risks of chemoprophylaxis after spinal surgery: a single-center experience with 6869 consecutive patients.

OBJECTIVE Venous thromboembolism (VTE) after spinal surgery is a major cause of morbidity, but chemoprophylactic anticoagulation can prevent it. However, there is variability in the timing and use of chemoprophylactic anticoagulation after spine surgery, particularly given surgeons' concerns for spinal epidural hematomas. The goal of this study was to provide insight into the safety, efficacy, and timing of anticoagulation therapy after spinal surgery. METHODS The authors retrospectively examined records from 6869 consecutive spinal surgeries performed in their departments at Northwestern University. Data on patient demographics, surgery, hospital course, timing of chemoprophylaxis, and complications, including deep venous thrombosis (DVT), pulmonary embolism (PE), and spinal epidural hematomas requiring evacuation, were collected. Data from the patients who received chemoprophylaxis (n = 1904) were compared with those of patients who did not (n = 4965). The timing of chemoprophylaxis, the rate of VTEs, and the incidence of spinal epidural hematomas were analyzed. RESULTS The chemoprophylaxis group had more risk factors, including greater age (59.70 vs 51.86 years, respectively; p < 0.001), longer surgery (278.59 vs 145.66 minutes, respectively; p < 0.001), higher estimated blood loss (995 vs 448 ml, respectively; p < 0.001), more comorbid diagnoses (2.69 vs 1.89, respectively; p < 0.001), history of VTE (5.8% vs 2.1%, respectively; p < 0.001), and a higher number were undergoing fusion surgery (46.1% vs 24.7%, respectively; p < 0.001). The prevalence of VTE was higher in the chemoprophylaxis group (3.62% vs 2.03%, respectively; p < 0.001). The median time to VTE occurrence was shorter in the nonchemoprophylaxis group (3.6 vs 6.8 days, respectively; p = 0.0003, log-rank test; hazard ratio 0.685 [0.505-0.926]), and the peak prevalence of VTE occurred in the first 3 postoperative days in the nonchemoprophylaxis group. The average time of initiation of chemoprophylaxis was 1.46 days after surgery. The rates of epidural hematoma were 0.20% (n = 4) in the chemoprophylaxis group and 0.18% (n = 9) in the nonchemoprophylaxis group (p = 0.622). CONCLUSIONS The risks of spinal epidural hematoma among patients who receive chemoprophylaxis and those who do not are low and equivalent. Administering anticoagulation therapy from 1 day before to 3 days after surgery is safe for patients at high risk for VTE.

Characteristics and Mortality of Pneumocystis Pneumonia in Patients With Cushing's Syndrome: A Plea for Timely Initiation of Chemoprophylaxis.

In patients with Cushing’s syndrome, development of Pneumocystis pneumonia (PCP) is associated with extreme cortisol production levels. In this setting, immune reconstitution after abrogation of cortisol excess appears to induce development of symptomatic PCP. The high mortality rate warrants timely initiation of chemoprophylaxis or even preemptive treatment of PCP.

Venous thromboembolism prophylaxis in neurosurgical trauma patients

BackgroundVenous thromboembolisms (VTEs) occur more frequently in patients with traumatic brain injuries (TBIs) and spinal cord injuries, yet the use of chemoprophylaxis is controversial. The purpose of this study was to investigate the relationship between the timing of chemical VTE prophylaxis initiation and the development of VTE events in these patients. MethodsProspective data were collected and retrospectively reviewed on 1425 patients sustaining TBIs or spinal injuries from 2010 to 2014. Patients were reviewed with respect to age, gender, injury severity score, Glasgow coma score, and mechanism of injury as well as timing of initiation of chemical VTE prophylaxis and presence or absence of VTE. ResultsPatients who developed a VTE had a significantly longer time to initiation of chemical VTE prophylaxis (6.7 ± 4.9 d versus 4.7 ± 4.9 d, P < 0.001) compared with those that did not develop a VTE. Also, for each 1 d increase in time to prophylaxis initiation, the odds of developing a VTE increased significantly (odds ratio = 1.055, P < 0.001). The combination subarachnoid hemorrhage/subdural hemorrhage group was started on VTE prophylaxis significantly later (8.3 ± 6.1 d versus 6.7 ± 3.9 d, P < 0.01) than the overall TBI group and had a higher incidence of VTE (14.4 versus 10.4%, P = NS). In contrast, patients sustaining isolated spinal injuries received chemical VTE prophylaxis significantly earlier (3.4 ± 4.2 d versus 6.7 ± 3.9 d, P < 0.001) and had a significant decrease in their VTE rate (4.4 versus 10.4%, P < 0.0001) compared with the overall TBI group. ConclusionsPatients with VTEs had a significant delay in time to initiation of chemoprophylaxis compared with patients without VTEs. Patients sustaining a TBI had a 2-fold delay in initiation of chemoprophylaxis and an associated 2-fold increase in VTE events compared with patients who sustained spinal injuries. Of those patients who developed a TBI, patients who sustained a combination subarachnoid hemorrhage and/or subdural hemorrhage had a significant delay in initiation of chemoprophylaxis with a higher rate of VTE events.

P.090 A systematic review of the risks and benefits of venous thromboembolism prophylaxis in traumatic brain injury

Background: Patients suffering from traumatic brain injury (TBI) are at increased risk of venous thromboembolism (VTE). However, initiation of chemoprophylaxis (VTEp) may cause further intracranial hemorrhage. We reviewed the literature to determine the post-injury time interval at which VTEp can be administered without risk of TBI evolution and hematoma expansion. Methods: MEDLINE and EMBASE databases were searched. Inclusion criteria were: studies investigating timing and safety of VTEp in TBI patients not previously on oral anticoagulation. Two investigators extracted data and graded the papers based on levels of evidence. Results: A total of 408 studies were screened. Forty-five studies were reviewed in-entirety and 21 were included in the systematic review. There were 2 prospective randomized trials and 19 comparative studies. Eighteen total studies demonstrated that VTEp post injury in patients with stable head computed tomography scan does not lead to TBI progression. Fourteen studies demonstrated that VTEp administration specifically 24–72 hours post injury is safe in patients with stable injury. Four studies suggested that administering VTEp within 24 hours of injury in patients with stable TBI does not lead to progressive ICH. Conclusions: Literature suggests that administering VTEp 48 hours post-injury may be safe for patients with low-hemorrhagic risk TBIs and stable injury on repeat imaging.

Deep vein thrombosis screening and risk factors in a high-risk trauma population

BackgroundTrauma patients requiring acute inpatient rehabilitation are significantly injured, with increased risk for deep vein thrombosis (DVT). We evaluated routine screening for occult DVT in such patients, and analyzed DVT risk factors. Materials and methodsData from level I trauma center patients discharged to a single acute rehabilitation center (ARC) from 2007–2011 were retrospectively reviewed. Routine lower extremity duplex was performed on ARC admission. Follow-up data were collected for patients with occult DVT (ARC DVT). DVT predictors were evaluated using logistic regression. ResultsOf 622 patients, 534 (86%) had screening duplex; 26 (4.8%) had an ARC DVT. A majority of 442 patients (71%) received enoxaparin prophylaxis in hospital, for a median 64% of hospital days. Of ARC DVT patients, 17 received full anticoagulation and 16 received vena cava filters. Thirty-seven patients had DVT diagnosed in the hospital (hospital DVT) before discharge to ARC. Hospital DVT and ARC DVT groups were comparable except shorter median hospital length of stay and lower head abbreviated injury scale in ARC DVT patients. On multivariate analysis, increased intensive care unit length of stay, age >65 y, a lower percentage of hospital days receiving chemoprophylaxis, and delayed initiation of chemoprophylaxis were significantly predictive of DVT after adjustment for sex, mechanism, injury severity score, and admission systolic blood pressure. Presence of pelvic fractures and ages 50–65 y also posed an increased risk. ConclusionsThe incidence of occult DVT on ARC admission is low in trauma patients. Several risk factors for DVT in the trauma ARC population were identified. Nonselective screening of all trauma patients on admission to ARC is not supported by this analysis.

Low incidence of symptomatic thromboembolic events after total ankle arthroplasty without routine use of chemoprophylaxis.

There is little evidence regarding the incidence of symptomatic venous thromboembolism (VTE) following total ankle arthroplasty (TAA) to allow formulation of treatment recommendations. The purpose of this study was to determine the incidence of symptomatic VTE events after TAA without use of chemoprophylaxis and to identify risk factors contributing to the occurrence of VTEs. We conducted a retrospective chart review of 637 patients (664 ankles) who received a TAA between May 2007 and January 2014 and had a minimum follow-up of 3 months. Chemoprophylaxis was prescribed only in the setting of a history of VTE or active coagulopathy. Patients were continued on chemoprophylactic agents if they were taking these medications preoperatively. A VTE event was defined when clinical signs and symptoms of deep venous thrombosis (DVT) were confirmed with use of Doppler ultrasonography or pulmonary embolism was confirmed with the use of a computed tomography scan. Routine screening for VTE was not performed. The overall incidence of clinically detected VTE events was 0.60% (4/664), with 0.45% (3 patients) developing a DVT and 0.15% (1 patient) developing a nonfatal pulmonary embolism. Moreover, we identified a subset of 434 patients without identifiable preoperative risk factors who were not taking chemoprophylaxis preoperatively and were not prescribed chemoprophylaxis postoperatively. Two of these patients developed a DVT postoperatively (0.46%). Given the low incidence of clinically detected VTE, no significant correlation could be identified between the occurrence of VTE events and risk factors. Our results suggest that clinically detectable VTE after TAA is uncommon. Patients without identifiable risk factors do not appear to require chemoprophylaxis following TAA. We recommend continuation of antiplatelet or anticoagulation therapy in patients who are taking these medications preoperatively and the initiation of chemoprophylaxis postoperatively in patients with known risk factors for VTE. Level IV, case series.

Risk of pulmonary embolism in trauma patients: Not all created equal

Patients with traumatic brain injury (TBI) are assumed to be at an increased risk for pulmonary embolism (PE). Delay in the initiation of chemoprophylaxis and prophylactic placement of inferior vena cava filters have been advocated by some because of concerns for increased intracranial hemorrhage in the presence of prophylactic anticoagulation. We hypothesized that patients with isolated TBI would not be at increased risk for the development of PE compared with the general trauma population. Patients from the National Trauma Data Bank from the year 2008 were analyzed. Patient demographics, Injury Severity Score, and the prevalence of deep-vein thrombosis and PE were extracted. Studied injuries were assigned to six categories: thorax, abdominal solid organs, pelvic fracture, lower extremity fracture, spine fracture, and TBI. Of a total of 627,775 injured patients, 2,182 (0.35%) had a documented PE. The prevalence of PE in patients with isolated TBI, lower extremity, pelvic fracture, liver and/or spleen, thorax, spine, multiple injuries, and none of the studied injuries were 0.25%, 0.36%, 0.35%, 0.37%, 0.52%, 0.37%, 1.1%, and 0.12%, respectively. Using an age-, sex- and race-adjusted multivariable logistic regression model and controlling for interaction between inferior vena cava filters and injury types, we found that isolated TBI was not associated with PE. Isolated TBI does not appear to be associated with an increased incidence of PE compared with other injuries. Patients with isolated TBI may not require early aggressive prophylaxis as is the standard for other high-risk groups.

Progressive HIV infection in the presence of a raised CD4+ count: HIV/HTLV-1 co-infection

There are a number of pathophysiological causes for a normal or raised CD4 count in the context of progressive HIV infection. These include various co-infections, previous splenectomy, and lymphoproliferative disorders. Such circumstances can both confound HIV diagnosis and delay initiation of chemoprophylaxis and highly active antiretroviral therapy (HAART). We describe the case of a patient co-infected with HIV and human T-cell lymphotropic virus type 1 (HTLV-1) who, prior to HAART initiation, was found to have progressive immune deficiency associated with a raised CD4 count.

Progressive HIV infection in the presence of a raised CD4+ count: HIV/HTLV-1 co-infection

There are a number of pathophysiological causes for a normal or raised CD4 count in the context of progressive HIV infection. These include various co-infections, previous splenectomy, and lymphoproliferative disorders. Such circumstances can both confound HIV diagnosis and delay initiation of chemoprophylaxis and highly active antiretroviral therapy (HAART). We describe the case of a patient co-infected with HIV and human T-cell lymphotropic virus type 1 (HTLV-1) who, prior to HAART initiation, was found to have progressive immune deficiency associated with a raised CD4 count.

Active Case Finding and Prevention of Tuberculosis Among a Cohort of Contacts Exposed to Infectious Tuberculosis Cases in New York City

Tuberculosis contact investigation identifies individuals who may be recently infected with tuberculosis and are thus at increased risk for disease. Contacts with latent tuberculosis infection (LTBI) are offered chemoprophylaxis to prevent active disease; however, the effectiveness of this intervention is unclear as treatment completion is generally low. A retrospective cohort study of 30 561 contacts identified during investigation of 5182 cases of tuberculosis diagnosed in New York City, 1997-2003, was performed. We searched the NYC tuberculosis registry to identify contacts developing active tuberculosis within 4 years of follow-up. We estimated the following: number of contacts undergoing evaluation (ie, tuberculin skin test and/or chest radiograph) per prevalent case diagnosed; number of contacts with LTBI that need to be treated with standard chemoprophylaxis to prevent 1 active case. Of 30 561 contacts, 27 293 (89%) were evaluated and 268 prevalent cases were diagnosed (102 contacts evaluated per prevalent case diagnosed, 95% confidence interval [CI], 90-115). LTBI was diagnosed in 7597 contacts, including 6001 (79%) who initiated chemoprophylaxis, 3642 (61%) who later completed treatment, and 2359 (39%) who did not complete treatment. During 4 years of follow-up, active tuberculosis was diagnosed in 46 contacts with LTBI, including 22 of 6001 (0.4%) who initiated chemoprophylaxis and 24 of 1596 (1.5%) who did not initiate treatment. The absolute risk reduction afforded by chemoprophylaxis initiation was 1.1% (95% CI, .6%-1.9%), leading to an estimated 88 contacts treated to prevent 1 tuberculosis case (95% CI, 53-164). Contact investigation facilitates active case finding and tuberculosis prevention, even when completion rates of chemoprophylaxis are suboptimal.

Opportunities for chemoprophylaxis in children with culture-confirmed tuberculosis.

Chemoprophylaxis is an effective strategy to prevent progression of tuberculosis (TB) in vulnerable children who have had contact with an infectious source of TB. However, many operational gaps prevent implementation of routine chemoprophylaxis in high-burden settings. The TB exposure status and disease spectrum in children diagnosed with culture-confirmed TB are described and missed opportunities for chemoprophylaxis are highlighted. All children <13 years of age diagnosed with culture-confirmed TB at a tertiary referral hospital between March 2003 and February 2007 were included. Clinical data were collected from retrospective review of files. TB was classified as pulmonary and extra-pulmonary; disseminated TB included miliary disease and TB meningitis. During the study period, 614 children (327, 53·3% boys, median age 32 months) were diagnosed with culture-confirmed TB. Contact with an infectious adult source case was documented in 333 (54·2%), 237 (71·2%) of whom were <5 years of age, and 24 (7·2%) were HIV-infected and ≥5 years of age. Of those eligible for chemoprophylaxis, missed opportunities were identified in 156/221 (70·6%) children; 127 (81·4%) were <3 years of age, 39 (25%) had disseminated TB and 8 (5·1%) died. The TB source case was the mother or father in 74/156 (47·4%) children. Opportunities for initiation of chemoprophylaxis in vulnerable children following TB exposure are often missed. Awareness should be increased among health-care workers and in the community at large regarding the importance of chemoprophylaxis in young and HIV-infected children. Health system strengthening is required to improve delivery of chemoprophylaxis to vulnerable children in close contact with newly diagnosed infectious TB cases.

Screening for Chronic Hepatitis B in Patients Undergoing Chemotherapy for Lymphoma or Colon Cancer

Purpose: Approximately 350 to 400 million people are hepatitis B surface antigen (HBsAg) carriers. HBsAg carriers who receive cytotoxic or immunosuppressive therapy are at significant risk of hepatitis B (HBV) reactivation. Spontaneous reactivation may occur in up to 22% of HBV-infected patients with previously negative HBeAg status. Cytotoxic therapy has been shown in prospective studies to confer a threefold greater risk of viral reactivation. Patients undergoing chemotherapy are often not screened for HBV infection, and prophylactic antiviral therapy is markedly underused. The use of steroids with chemotherapy for patients with hematologic malignancies poses the greatest risk of reactivation, up to 67%. For solid tumors such as breast cancer, a slightly lower risk of 40% exists. There does not appear to be extensive data reporting the reactivation risk of HBV for chemotherapy in colon cancer. Methods: This was a retrospective chart review of patients at Scott & White Healthcare Hospital who have undergone chemotherapy for lymphoma or colon cancer. For each patient, liver function tests (LFTs) were trended for the duration of the chemotherapy. We reviewed the charts to determine if patients were screened for HBV prior to chemotherapy induction. If patients were HbsAg-positive, we further reviewed the chart for initiation of chemoprophylaxis. HBV screening rate and 95% Confidence Interval (CI) were estimated for entire cohort, both normal and abnormal LFT groups. HBV screening rates between the 2 groups were compared using Chi-square test. SAS version 9.2 (SAS Institute INC, Cary, NC) was used for statistical analysis. Results: Approximately 800 lymphoma and 500 colon cancer cases were found and preliminary analysis was performed on 242 patients. See table 1 for descriptive statistics. Two patients were excluded as they did not have any LFTs. Of the 240 patients, 110 had normal LFTs and 130 abnormal LFTs. See table 2 for comparison of HBV screening results between the normal and abnormal LFT groups. Screening rates between the two groups were significantly different (p-value=0.0244). A total of 17 patients received HBV screening (screening rate 7.02% with 95% CI of (4.15-11.01%). One of the excluded patients received screening.Table 1Table 2Conclusion: As our preliminary analysis has shown, screening rates in our study were low. Despite guidelines, chemoprophylaxis of HbsAg carriers is low prior to cancer chemotherapy. Our data analysis is ongoing and will be complete at the time of publication.

Surgeon Practices Regarding Postoperative Thromboembolic Prophylaxis After High-Risk Spinal Surgery

Survey study. To assess a sample of spine surgeons' current practices of thromboembolic prophylaxis after high-risk surgery for tumors and trauma. Although chemoprophylaxis for thromboembolic events is not routinely used after elective spinal surgery, it is more widely recommended in high-risk patients after spine surgery for trauma or tumors. In these high-risk cases, surgeons must decide what method(s) of prophylaxis to use and when it can be safely initiated. Unfortunately, there are limited data evaluating the efficacy or safety of different prophylaxis protocols after high-risk spinal surgery; as a result there are no accepted treatment guidelines concerning this issue. To the authors' knowledge, no previous study examining practices of thromboembolic prophylaxis after high-risk spinal surgery has been published. One hundred ninety-three orthopaedic and neurosurgical spine surgeons with established clinical interest and volume in spine trauma and/or spine tumor surgery were invited by email to complete an on-line questionnaire. Ten questions focused on varying issues that included the perceived risk of deep venous thrombosis (DVT), pulmonary embolism (PE), postoperative epidural hematoma, preferred chemoprophylactic agents, the safe time point for initiation of chemoprophylaxis, and use of inferior vena cava (IVC) filters. Ninety-four surgeons completed the questionnaire, which represented a 49% response rate. Regarding a safe time point to start chemoprophylaxis, the most common response was 48 hours after surgery (21 of 94, 22%). However, individual responses varied widely: 15% chose 24 hours, 13% chose 72 hours, 12% chose less than 24 hours, and 10% chose 96 hours. Some indicated they would start chemoprophylaxis before surgery, whereas others responded they would never use it. Sixty-three percent (59 of 94) stated that they based this decision on personal experience over evidence-based review of the literature. A majority of surgeons selected low-molecular-weight heparin as their agent of choice (54 of 94, 58%). Respondents most commonly (44 of 93, 47%) felt that the risk of clinically relevant postoperative epidural hematoma was between 1% and 5%; 29% (27 of 93) felt the risk was less than 1%; and 17% (16 of 93) felt it was as high as 5% to 10%. Those who felt the risk of epidural hematoma to be lower than 5% tended to initiate chemoprophylaxis earlier than those who estimated the risk to be higher than 5%. Thirty-seven percent (34 of 93) felt the perceived risk for a DVT was 1% to 5%; 25% (23 of 94) felt it was 5% to 10%; and 16% (15 of 93) felt it was less than 1%. Those who estimated the risk of DVT to be higher tended to initiate therapy earlier than groups that estimated the risk to be lower. Although the decision to use an IVC filter varied considerably, there was a clear trend towards having the filter placed before surgery (60 of 78, 77%). These data are the first to demonstrate the wide variability of surgeons' practices regarding thromboembolic prophylaxis in high-risk spine surgery patients. This variability is likely a symptom of the glaring paucity of scientific evidence concerning the risk for symptomatic epidural hematoma, DVT, and PE and the efficacy and safety of specific chemoprophylactic protocols after spine surgery. This study highlights the need for more rigorous prospective evaluation of thromboembolic risk after spinal surgery and, subsequently, the efficacy and safety of currently available thromboembolic prophylaxis protocols.

Editorial Commentary:Initiating Influenza Chemoprophylaxis with the First Influenza Case: A New Institutional Standard?

In this issue of Clinical Infectious Diseases, Rubin et al. [ 1 ] discuss postexposure chemoprophylaxis against influenza A in long-term care facilities (LTCFs). They report that amantadine chemoprophylaxis initiated ^5 days after the beginning of an influenza outbreak reduces outbreak duration, incidence of influenza symptoms, and case-fatality rate. Their findings make sense: the earlier the diagnosis, the quicker the introduction of barriers to transmission (such as speedier chemoprophylaxis initiation), the lower the number of new vectors, and the lower the impact and extent of an influenza outbreak. These

Active tuberculosis after isoniazid chemoprophylaxis of Southeast Asian refugees.

The outcome of isoniazid chemoprophylaxis for tuberculosis was assessed in refugees from Southeast Asia. From July 1979 through June 1982, 2,795 tuberculin-positive refugees were prescribed isoniazid chemoprophylaxis at the time of their resettlement in King County, Washington. Through December 1983, 19 cases of active tuberculosis had arisen in those refugees. The annual incidence varied between 2.04 and 2.86 cases per 1,000 receiving treatment during the 4 yr after initiation of chemoprophylaxis (cumulative incidence, 9.66 per 1,000). Seven of the cases of tuberculosis occurring after isoniazid chemoprophylaxis were pulmonary, 1 was pulmonary and extrapulmonary (lymphatic), and 11 were extrapulmonary alone (lymphatic, 6 cases; pleural, 4 cases; soft tissue, 1 case). Fifteen of the 19 cases were culture positive, among which 8 M. tuberculosis isolates were susceptible to isoniazid and 7 were resistant. A case-control analysis showed that poor compliance, defined as taking isoniazid for 3 months or less, was associated with a sixfold increase in risk for subsequent isoniazid-susceptible tuberculosis but with no increased risk for subsequent isoniazid-resistant disease. Thus, active tuberculosis continued to occur with a low but relatively constant incidence after prescription of isoniazid chemoprophylaxis to Southeast Asian refugees. In this setting, poor compliance with chemoprophylaxis predisposed to isoniazid-susceptible, but not to isoniazid-resistant tuberculosis. There is a need to improve the approach to prevention of tuberculosis in Southeast Asian refugees.