Toward a More Robust Prediction of Pulmonary Embolism in Trauma Patients: A Risk Assessment Model Based on 38,000 Patients

The silent killer: Previously undetected pulmonary emboli that result in death after discharge

INTRODUCTION

Pulmonary embolism (PE) is a recognized cause of death in hospitalized trauma patients, yet less is known about PE after discharge.

PATIENTS & METHODS

All post-discharge, autopsy-demonstrated, fatal PE resulting from trauma within a large US county over six years were analyzed. Counts, percentages, mean values, SD, and IQR were calculated for all variables.

RESULTS

1848 trauma deaths were reviewed, of which 85% had an autopsy. Eighty-five patients died from PE after discharge from their initial injury. 53% were initially treated at non-trauma centers, and 9% did not seek medical assistance. 75% were injured by falling, and most injuries occurred in the lower extremities. 86% had an ISS <16, but 87% needed assistance or were bed-bound after injury, despite 75% having no mobility limitations before the injury. 53% died within one month of injury, and 91% within the first year. Before death, only 11% were prescribed chemical thromboprophylaxis or an antiplatelet agent, and only 8% were diagnosed with venous thromboembolism before death.

CONCLUSIONS

Fatal PE after discharge typically occurred following activity-limiting lower extremity injuries with an ISS<16.

Venous Thromboembolism in Trauma: The Role of Anticoagulation and Inferior Vena Cava Filters

Venous thromboembolism (VTE) is a significant contributor to morbidity and mortality among patients with severe trauma. Historically, prophylactic inferior vena cava filters (IVCFs) were used in high-risk trauma patients with suspected risk factors for VTE, including prolonged immobilization, and concurrent contraindication to anticoagulation. Mounting data regarding the efficacy of IVCF in this cohort, as well as concerns regarding morbidity of an in situ IVCF, have challenged this practice paradigm. In this review, we discuss the comanagement of VTE and trauma, including anticoagulation and the use of IVCF.

Association of the Risk of a Venous Thromboembolic Event in Emergency vs Elective General Surgery

Importance

Trauma patients have an increased risk of venous thromboembolism (VTE), partly because of greater inflammation. However, it is unknown if this association is present in patients who undergo emergency general surgery (EGS).

Objectives

To investigate whether emergency case status is independently associated with VTE compared with elective case status and to test the hypothesis that emergency cases would have a higher risk of VTE.

Design, Setting, and Participants

This retrospective cohort study used the American College of Surgeons National Surgical Quality Improvement Program database from January 1, 2005, to December 31, 2016, for all cholecystectomies, ventral hernia repairs (VHRs), and partial colectomies (PCs) to obtain a sample of commonly encountered emergency procedures that have elective counterparts. Emergency surgeries were then compared with elective surgeries. The dates of analysis were January 1 to 31, 2019.

Main Outcomes and Measures

The primary outcome was VTE at 30 days. A multivariable analysis controlling for age, sex, body mass index, bleeding disorder, disseminated cancer, laparoscopy approach, and surgery type was performed.

Results

There were 604 537 adults undergoing surgical procedures over 12 years (mean [SD] age, 55.3 [16.6] years; 61.4% women), including 285 847 cholecystectomies, 158 500 VHRs, and 160 190 PCs. The rate of VTE within 30 days was 1.9% for EGS and 0.8% for elective surgery, a statistically significant difference. Overall, 4607 patients (0.8%) had deep vein thrombosis, and 2648 patients (0.4%) had pulmonary embolism. A total of 6624 VTEs (1.1%) occurred in the cohort. As expected, when VTE risk was examined by surgery type, the risk increased with invasiveness (0.5% for cholecystectomy, 0.8% for VHR, and 2.4% for PC; P < .001). On multivariable analysis, EGS was independently associated with VTE (odds ratio [OR], 1.70; 95% CI, 1.61-1.79). Also associated with VTE were open surgery (OR, 3.38; 95% CI, 3.15-3.63) and PC (OR, 1.86; 95% CI, 1.73-1.99).

Conclusions and Relevance

In this cohort study, emergency surgery and increased invasiveness appeared to be independently associated with VTE compared with elective surgery. Further study on methods to improve VTE chemoprophylaxis is highly recommended for emergency and more extensive operations to reduce the risk of potentially lethal VTE.

Increasing BMI is associated with higher mortality, worsening outcomes and highly specific injury patterns following trauma: A multi-institutional analysis of 191,274 patients

BACKGROUND

As the prevalence of obesity has increased, trauma centers are faced with managing this expanding demographics' unique care requirements. Research on the effects of body mass index (BMI) in trauma patients remains conflicting. This study aims to evaluate the impact of BMI on patterns of injury and patient outcomes following trauma.

METHODS

Patients from 87 hospitals' trauma registries were selected. Those missing height, weight, disposition, or who died in the emergency department were excluded. The BMI categories were calculated from admission height and weight and verified against the electronic medical records. Patients were grouped by the National Institutes of Health-defined obesity class and compared by rate of mortality and in-hospital complications. Logistic regression was used to estimate associations, adjusting for age, gender, race, Injury Severity Score, and number of comorbidities.

RESULTS

There were 191,274 patients, 53% male; mean age was 60.4 years, mean Glasgow Coma Scale score 14.4, mean Injury Severity Score of 8.8, and 40.4% normal weight. Increased BMI was associated with an injury pattern of increased rates of extremity fractures (humerus, femur, tibia/fibula) and decreased rates of hip fractures and head injuries. Compared with the normal weight group, patients were more likely to die if they were Underweight (adjusted odds ratio [AOR], 1.18; 95% confidence interval [CI], 1.01-1.38), obese class II (AOR, 1.24; 95% CI, 1.07-1.45), or obese class III (AOR, 1.55; 95% CI, 1.29-1.87). Obese class III was associated with higher odds of a National Trauma Data Standard complication (AOR, 1.20; 95% CI, 1.11-1.30).

CONCLUSION

In this large multicenter study, increasing BMI and lower than normal BMI were strongly associated with higher mortality. Increasing BMI was also associated with longer length of stay, increased complications, and unique injury patterns. These untoward outcomes, coupled with a distinct injury pattern, warrant care guidelines specific to trauma patients with higher BMI, as well as those with BMI lower than normal.

LEVEL OF EVIDENCE

Epidemiological, Level III.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

LEVEL OF EVIDENCE

Therapeutic, level IV.

Significant Reduction of Pulmonary Embolism in Orthopaedic Trauma Patients

OBJECTIVES

To report results of a protocol to lessen incidence of pulmonary embolism (PE) among orthopaedic trauma patients.

DESIGN

Retrospective review.

SETTING

Level 1 trauma center.

PATIENT/PARTICIPANTS

Orthopaedic trauma inpatients were included in the study.

INTERVENTION

On arrival, an orthopaedic trauma patient's PE risk is calculated using a previously developed tool. If possible, patients at high risk are given their first dose of enoxaparin before leaving the emergency room. If other injuries preclude enoxaparin, then chemoprophylaxis is held for 24 hours. Twenty-four hours after arrival, the patient's ability to receive enoxaparin is reassessed. If possible, enoxaparin is started, with dosing twice a day. If enoxaparin is still contraindicated, a removable inferior vena cava filter is placed. Adequacy of enoxaparin dosing is tested using anti-factor Xa assay, drawn 4 hours after the third dose of enoxaparin. If the anti-factor Xa result is less than 0.2 IU/mL, a removable inferior vena cava filter is placed. If the result is 0.2-0.5 IU/mL, enoxaparin dosing is continued. If greater than 0.5 IU/mL, the dose of enoxaparin is reduced.

OUTCOME MEASURE

The main outcome measure was rate of PE.

RESULTS

From September 1, 2015 to December 31, 2015, our hospital admitted 420 orthopaedic trauma patients. Fifty-one patients were classed as high risk for PE. In September through December 2015, 9 sustained PE, 1 of which was fatal. From September 1, 2016 to December 31, 2016, our hospital admitted 368 orthopaedic trauma patients with comparable age and Injury Severity Score to 2015. Forty patients were at high risk for PE, 1 sustained a nonfatal PE. PE incidence from September to December 2016 was significantly lower than in 2015 (P = 0.02). Overall, 26 patients managed under the new protocol had IVCFs placed, 21 had their filters removed, and 3 died with filters in place. There were no complications during filter placement or removal. One patient had hemorrhage felt to be attributable to enoxaparin.

CONCLUSIONS

Our protocol emphasizes more robust enoxaparin dosing, and more frequent use of IVCF, but only among those at high risk. We lessened the incidence of PE, with a low complication rate.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Measurement error and timing of predictor values for multivariable risk prediction models are poorly reported

OBJECTIVE

Measurement error in predictor variables may threaten the validity of clinical prediction models. We sought to evaluate the possible extent of the problem. A secondary objective was to examine whether predictors are measured at the intended moment of model use.

METHODS

A systematic search of Medline was used to identify a sample of articles reporting the development of a clinical prediction model published in 2015. After screening according to a predefined inclusion criteria, information on predictors, strategies to control for measurement error, and intended moment of model use were extracted. Susceptibility to measurement error for each predictor was classified into low and high risks.

RESULTS

Thirty-three studies were reviewed, including 151 different predictors in the final prediction models. Fifty-one (33.7%) predictors were categorized as high risk of error; however, this was not accounted for in the model development. Only 8 (24.2%) studies explicitly stated the intended moment of model use and when the predictors were measured.

CONCLUSION

Reporting of measurement error and intended moment of model use is poor in prediction model studies. There is a need to identify circumstances where ignoring measurement error in prediction models is consequential and whether accounting for the error will improve the predictions.

Reexamination of a Battlefield Trauma Golden Hour Policy

BACKGROUND

Most combat casualties who die, do so in the prehospital setting. Efforts directed toward alleviating prehospital combat trauma death, known as killed in action (KIA) mortality, have the greatest opportunity for eliminating preventable death.

METHODS

Four thousand five hundred forty-two military casualties injured in Afghanistan from September 11, 2001, to March 31, 2014, were included in this retrospective analysis to evaluate proposed explanations for observed KIA reduction after a mandate by Secretary of Defense Robert M. Gates that transport of injured service members occur within 60 minutes. Using inverse probability weighting to account for selection bias, data were analyzed using multivariable logistic regression and simulation analysis to estimate the effects of (1) gradual improvement, (2) damage control resuscitation, (3) harm from inadequate resources, (4) change in wound pattern, and (5) transport time on KIA mortality.

RESULTS

The effect of gradual improvement measured as a time trend was not significant (adjusted odds ratio [AOR], 0.99; 95% confidence interval [CI], 0.94-1.03; p = 0.58). For casualties with military Injury Severity Score of 25 or higher, the odds of KIA mortality were 83% lower for casualties who needed and received prehospital blood transfusion (AOR, 0.17; 95% CI, 0.06-0.51; p = 0.002); 33% lower for casualties receiving initial treatment by forward surgical teams (AOR, 0.67; 95% CI, 0.58-0.78; p < 0.001); 70%, 74%, and 87% lower for casualties with dominant injuries to head (AOR, 0.30; 95% CI, 0.23-0.38; p < 0.001), abdomen (AOR, 0.26, 95% CI, 0.19-0.36; p < 0.001) and extremities (AOR, 0.13; 95% CI, 0.09-0.17; p < 0.001); 35% lower for casualties categorized with blunt injuries (AOR, 0.65; 95% CI, 0.46-0.92; p = 0.01); and 39% lower for casualties transported within one hour (AOR, 0.61; 95% CI, 0.51-0.74; p < 0.001). Results of simulations in which transport times had not changed after the mandate indicate that KIA mortality would have been 1.4% higher than observed, equating to 135 more KIA deaths (95% CI, 105-164).

CONCLUSION

Reduction in KIA mortality is associated with early treatment capabilities, blunt mechanism, select body locations of injury, and rapid transport.

LEVEL OF EVIDENCE

Therapy, level III.