Derek J. Roberts

Intra-abdominal hypertension and the abdominal compartment syndrome: updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome

PurposeTo update the World Society of the Abdominal Compartment Syndrome (WSACS) consensus definitions and management statements relating to intra-abdominal hypertension (IAH) and the abdominal compartment syndrome (ACS).MethodsWe conducted systematic or structured reviews to identify relevant studies relating to IAH or ACS. Updated consensus definitions and management statements were then derived using a modified Delphi method and the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) guidelines, respectively. Quality of evidence was graded from high (A) to very low (D) and management statements from strong RECOMMENDATIONS (desirable effects clearly outweigh potential undesirable ones) to weaker SUGGESTIONS (potential risks and benefits of the intervention are less clear).ResultsIn addition to reviewing the consensus definitions proposed in 2006, the WSACS defined the open abdomen, lateralization of the abdominal musculature, polycompartment syndrome, and abdominal compliance, and proposed an open abdomen classification system. RECOMMENDATIONS included intra-abdominal pressure (IAP) measurement, avoidance of sustained IAH, protocolized IAP monitoring and management, decompressive laparotomy for overt ACS, and negative pressure wound therapy and efforts to achieve same-hospital-stay fascial closure among patients with an open abdomen. SUGGESTIONS included use of medical therapies and percutaneous catheter drainage for treatment of IAH/ACS, considering the association between body position and IAP, attempts to avoid a positive fluid balance after initial patient resuscitation, use of enhanced ratios of plasma to red blood cells and prophylactic open abdominal strategies, and avoidance of routine early biologic mesh use among patients with open abdominal wounds. NO RECOMMENDATIONS were possible regarding monitoring of abdominal perfusion pressure or the use of diuretics, renal replacement therapies, albumin, or acute component-parts separation.ConclusionAlthough IAH and ACS are common and frequently associated with poor outcomes, the overall quality of evidence available to guide development of RECOMMENDATIONS was generally low. Appropriately designed intervention trials are urgently needed for patients with IAH and ACS.

Fluid overload, de-resuscitation, and outcomes in critically ill or injured patients: a systematic review with suggestions for clinical practice

BACKGROUND Sepsis is associated with generalised endothelial injury and capillary leak and has traditionally been treated with large volume fluid resuscitation. Some patients with sepsis will accumulate bodily fluids. The aim of this study was to systematically review the association between a positive fluid balance/fluid overload and outcomes in critically ill adults, and to determine whether interventions aimed at reducing fluid balance may be linked with improved outcomes. METHODS We searched MEDLINE, PubMed, EMBASE, Web of Science, The Cochrane Database, clinical trials registries, and bibliographies of included articles. Two authors independently reviewed citations and selected studies examining the association between fluid balance and outcomes or where the intervention was any strategy or protocol that attempted to obtain a negative or neutral cumulative fluid balance after the third day of intensive care compared to usual care. The primary outcomes of interest were the incidence of IAH and mortality. RESULTS Among all identified citations, one individual patient meta-analysis, 11 randomised controlled clinical trials, seven interventional studies, 24 observational studies, and four case series met the inclusion criteria. Altogether, 19,902 critically ill patients were studied. The cumulative fluid balance after one week of ICU stay was 4.4 L more positive in non-survivors compared to survivors. A restrictive fluid management strategy resulted in a less positive cumulative fluid balance of 5.6 L compared to controls after one week of ICU stay. A restrictive fluid management was associated with a lower mortality compared to patients treated with a more liberal fluid management strategy (24.7% vs 33.2%; OR, 0.42; 95% CI 0.32-0.55; P < 0.0001). Patients with intra-abdominal hypertension (IAH) had a more positive cumulative fluid balance of 3.4 L after one week of ICU stay. Interventions to decrease fluid balance resulted in a decrease in intra-abdominal pressure (IAP): an average total body fluid removal of 4.9 L resulted in a drop in IAP from 19.3 ± 9.1 mm Hg to 11.5 ± 3.9 mm Hg. CONCLUSIONS A positive cumulative fluid balance is associated with IAH and worse outcomes. Interventions to limit the development of a positive cumulative fluid balance are associated with improved outcomes. In patients not transgressing spontaneously from the Ebb to Flow phases of shock, late conservative fluid management and late goal directed fluid removal (de-resuscitation) should be considered.

Risk factors for intra-abdominal hypertension and abdominal compartment syndrome among adult intensive care unit patients: a systematic review and meta-analysis

IntroductionAlthough intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are associated with substantial morbidity and mortality among critically ill adults, it remains unknown if prevention or treatment of these conditions improves patient outcomes. We sought to identify evidence-based risk factors for IAH and ACS in order to guide identification of the source population for future IAH/ACS treatment trials and to stratify patients into risk groups based on prognosis.MethodsWe searched electronic bibliographic databases (MEDLINE, EMBASE, PubMed, and the Cochrane Database from 1950 until January 21, 2013) and reference lists of included articles for observational studies reporting risk factors for IAH or ACS among adult ICU patients. Identified risk factors were summarized using formal narrative synthesis techniques alongside a random effects meta-analysis.ResultsAmong 1,224 citations identified, 14 studies enrolling 2,500 patients were included. The 38 identified risk factors for IAH and 24 for ACS could be clustered into three themes and eight subthemes. Large volume crystalloid resuscitation, the respiratory status of the patient, and shock/hypotension were common risk factors for IAH and ACS that transcended across presenting patient populations. Risk factors with pooled evidence supporting an increased risk for IAH among mixed ICU patients included obesity (four studies; odds ratio (OR) 5.10; 95% confidence interval (CI), 1.92 to 13.58), sepsis (two studies; OR 2.38; 95% CI, 1.34 to 4.23), abdominal surgery (four studies; OR 1.93; 95% CI, 1.30 to 2.85), ileus (two studies; OR 2.05; 95% CI, 1.40 to 2.98), and large volume fluid resuscitation (two studies; OR 2.17; 95% CI, 1.30 to 3.63). Among trauma and surgical patients, large volume crystalloid resuscitation and markers of shock/hypotension and metabolic derangement/organ failure were risk factors for IAH and ACS while increased disease severity scores and elevated creatinine were risk factors for ACS in severe acute pancreatitis patients.ConclusionsAlthough several IAH/ACS risk factors transcend across presenting patient diagnoses, some appear specific to the population under study. As our findings were somewhat limited by included study methodology, the risk factors reported in this study should be considered candidate risk factors until confirmed by a large prospective multi-centre observational study.

Negative-pressure wound therapy for critically ill adults with open abdominal wounds: A systematic review

BACKGROUND Open abdominal management with negative-pressure wound therapy (NPWT) is increasingly used for critically ill trauma and surgery patients. We sought to determine the comparative efficacy and safety of NPWT versus alternate temporary abdominal closure (TAC) techniques in critically ill adults with open abdominal wounds. METHODS We conducted a systematic review of published and unpublished comparative studies. We searched MEDLINE, PubMed, EMBASE, Scopus, Web of Science, the Cochrane Database, the Center for Reviews and Dissemination, clinical trials registries, and bibliographies of included articles. Two authors independently abstracted data on study design, methodological quality, patient characteristics, and outcomes. RESULTS Among 2,715 citations identified, 2 randomized controlled trials and 9 cohort studies (3 prospective/6 retrospective) met inclusion criteria. Methodological quality of included prospective studies was moderate. One randomized controlled trial observed an improved fascial closure rate (relative risk [RR], 2.4; 95% confidence interval [CI], 1.0–5.3) and length of hospital stay after addition of retention sutured sequential fascial closure to the Kinetic Concepts Inc. (KCI) vacuum-assisted closure (VAC). Another reported a trend toward enhanced fascial closure using the KCI VAC versus Barker’s vacuum pack (RR, 2.6; 95% CI, 0.95–7.1). A prospective cohort study observed improved mortality (RR, 0.48; 95% CI, 0.25–0.92) and fascial closure (RR, 1.5; 95% CI, 1.1–2.0) for patients who received the ABThera versus Barker’s vacuum pack. Another noted a reduced arterial lactate, intra-abdominal pressure, and hospital stay for those fitted with the KCI VAC versus Bogotá bag. Most included retrospective studies exhibited low methodological quality and reported no mortality or fascial closure benefit for NPWT. CONCLUSION Limited prospective comparative data suggests that NPWT versus alternate TAC techniques may be linked with improved outcomes. However, the clinical heterogeneity and quality of available studies preclude definitive conclusions regarding the preferential use of NPWT over alternate TAC techniques. LEVEL OF EVIDENCE Systematic review, level III.

Sedation for critically ill adults with severe traumatic brain injury: a systematic review of randomized controlled trials.

Objectives:To summarize randomized controlled trials on the effects of sedative agents on neurologic outcome, mortality, intracranial pressure, cerebral perfusion pressure, and adverse drug events in critically ill adults with severe traumatic brain injury. Data Sources:PubMed, MEDLINE, EMBASE, the Cochrane Database, Google Scholar, two clinical trials registries, personal files, and reference lists of included articles. Study Selection:Randomized controlled trials of propofol, ketamine, etomidate, and agents from the opioid, benzodiazepine, &agr;-2 agonist, and antipsychotic drug classes for management of adult intensive care unit patients with severe traumatic brain injury. Data Extraction:In duplicate and independently, two investigators extracted data and evaluated methodologic quality and results. Data Synthesis:Among 1,892 citations, 13 randomized controlled trials enrolling 380 patients met inclusion criteria. Long-term sedation (≥24 hrs) was addressed in six studies, whereas a bolus dose, short infusion, or doubling of plasma drug concentration was investigated in remaining trials. Most trials did not describe baseline traumatic brain injury prognostic factors or important cointerventions. Eight trials possibly or definitely concealed allocation and six were blinded. Insufficient data exist regarding the effects of sedative agents on neurologic outcome or mortality. Although their effects are likely transient, bolus doses of opioids may increase intracranial pressure and decrease cerebral perfusion pressure. In one study, a long-term infusion of propofol vs. morphine was associated with a reduced requirement for intracranial pressure-lowering cointerventions and a lower intracranial pressure on the third day. Trials of propofol vs. midazolam and ketamine vs. sufentanil found no difference between agents in intracranial pressure and cerebral perfusion pressure. Conclusions:This systematic review found no convincing evidence that one sedative agent is more efficacious than another for improvement of patient-centered outcomes, intracranial pressure, or cerebral perfusion pressure in critically ill adults with severe traumatic brain injury. High bolus doses of opioids, however, have potentially deleterious effects on intracranial pressure and cerebral perfusion pressure. Adequately powered, high-quality, randomized controlled trials are urgently warranted.

Optimal glycemic control in neurocritical care patients: a systematic review and meta-analysis

IntroductionHyper- and hypoglycemia are strongly associated with adverse outcomes in critical care. Neurologically injured patients are a unique subgroup, where optimal glycemic targets may differ, such that the findings of clinical trials involving heterogeneous critically ill patients may not apply.MethodsWe performed a systematic review and meta-analysis of randomized controlled trials (RCTs) comparing intensive insulin therapy with conventional glycemic control among patients with traumatic brain injury, ischemic or hemorrhagic stroke, anoxic encephalopathy, central nervous system infections or spinal cord injury.ResultsSixteen RCTs, involving 1248 neurocritical care patients, were included. Glycemic targets with intensive insulin ranged from 70-140 mg/dl (3.9-7.8 mmol/L), while conventional protocols aimed to keep glucose levels below 144-300 mg/dl (8.0-16.7 mmol/L). Tight glycemic control had no impact on mortality (RR 0.99; 95% CI 0.83-1.17; p = 0.88), but did result in fewer unfavorable neurological outcomes (RR 0.91; 95% CI 0.84-1.00; p = 0.04). However, improved outcomes were only observed when glucose levels in the conventional glycemic control group were permitted to be relatively high [threshold for insulin administration > 200 mg/dl (> 11.1 mmol/L)], but not with more intermediate glycemic targets [threshold for insulin administration 140-180 mg/dl (7.8-10.0 mmol/L)]. Hypoglycemia was far more common with intensive therapy (RR 3.10; 95% CI 1.54-6.23; p = 0.002), but there was a large degree of heterogeneity in the results of individual trials (Q = 47.9; p<0.0001; I2 = 75%). Mortality was non-significantly higher with intensive insulin in studies where the proportion of patients developing hypoglycemia was large (> 33%) (RR 1.17; 95% CI 0.79-1.75; p = 0.44).ConclusionsIntensive insulin therapy significantly increases the risk of hypoglycemia and does not influence mortality among neurocritical care patients. Very loose glucose control is associated with worse neurological recovery and should be avoided. These results suggest that intermediate glycemic goals may be most appropriate.

Sedation for Critically Ill or Injured Adults in the Intensive Care Unit

As most critically ill or injured patients will require some degree of sedation, the goal of this paper was to comprehensively review the literature associated with use of sedative agents in the intensive care unit (ICU). The first and selected latter portions of this article present a narrative overview of the shifting paradigm in ICU sedation practices, indications for uninterrupted or prolonged ICU sedation, and the pharmacology of sedative agents. In the second portion, we conducted a structured, although not entirely systematic, review of the available evidence associated with use of alternative sedative agents in critically ill or injured adults. Data sources for this review were derived by searching OVID MEDLINE and PubMed from their first available date until May 2012 for relevant randomized controlled trials (RCTs), systematic reviews and/or meta-analyses and economic evaluations.Advances in the technology of mechanical ventilation have permitted clinicians to limit the use of sedation among the critically ill through daily sedative interruptions or other means. These practices have been reported to result in improved mortality, a decreased length of ICU and hospital stay and a lower risk of drug-associated delirium. However, in some cases, prolonged or uninterrupted sedation may still be indicated, such as when patients develop intracranial hypertension following traumatic brain injury. The pharmacokinetics of sedative agents have clinical importance and may be altered by critical illness or injury, co-morbid conditions and/or drug-drug interactions. Although use of validated sedation scales to monitor depth of sedation is likely to reduce adverse events, they have no utility for patients receiving neuromuscular receptor blocking agents. Depth of sedation monitoring devices such as the Bispectral Index (BIS©) also have limitations.Among existing RCTs, no sedative agent has been reported to improve the risk of mortality among the critically ill or injured. Moreover, although propofol may be associated with a shorter time to tracheal extubation and recovery from sedation than midazolam, the risk of hypertriglyceridaemia and hypotension is higher with propofol. Despite dexmedetomidine being linked with a lower risk of drug-associated delirium than alternative sedative agents, this drug increases risk of bradycardia and hypotension. Among adults with severe traumatic brain injury, there are insufficient data to suggest that any single sedative agent decreases the risk of subsequent poor neurological outcomes or mortality. The lack of examination of confounders, including the type of healthcare system in which the investigation was conducted, is a major limitation of existing pharmacoeconomic analyses, which likely limits generalizability of their results.

A critical overview of the influence of inflammation and infection on P-glycoprotein expression and activity in the brain

Background: P-glycoprotein is a blood–brain barrier efflux transporter that limits drug accumulation in the brain. Objective: To review recent in vivo and in vitro investigations that examined the influence of inflammation, infection and related clinical neuroinflammatory disorders on P-glycoprotein expression and activity in the brain. Methods: Critical overview of English-language studies. Results/conclusions: Inflammation and infection produce dynamic changes in P-glycoprotein expression and activity in the blood–brain barrier. In vitro, blood–brain barrier P-glycoprotein activity is downregulated after short-term exposure to inflammatory mediators whereas its activity is upregulated following more prolonged exposure. In vivo studies in both humans and animals have linked CNS inflammation, peripheral inflammation and related clinical neuroinflammatory disorders with alterations in the expression and activity of blood–brain barrier P-glycoprotein. The direction and degree of change in P-glycoprotein activity depends on the in vivo or in vitro model examined, the cell type examined (e.g., endothelial or glial), the inflammatory mediator utilized, the anatomic site in which the inflammatory response was first generated, the time points chosen for observation and the substrates analyzed. Alterations in P-glycoprotein activity affect drug activity in the CNS and seem clinically important.

Accuracy of Peripheral Thermometers for Estimating Temperature: A Systematic Review and Meta-analysis

Abnormalities in body temperature (that is, fever and hypothermia) are common (14). Such abnormalities are components of diagnostic criteria for certain disorders (58), influence clinical management decisions (9, 10), and are associated with increased mortality in certain patient populations (11, 12). For most adult and pediatric populations, fever is defined as a body temperature of 38.0C or higher (1315); this definition can vary according to certain patient characteristics (for example, acute brain injury [16, 17]), institutional preference (18), and different methods of assessing body temperature (Appendix Table 1). Hypothermia is also variably defined but generally accepted to occur when body temperature is less than 36.0C (19). Appendix Table 1. Temperature Measurement Sites and Methods Accurate assessment of temperature is important. Thermometers that measure temperature from an intravascular site are considered the gold standard (20). Guidelines in adults recommend measuring temperature from one of several central options (for example, the rectum) (21), whereas guidelines in children suggest measuring from a peripheral site (for example, the axilla) (22, 23, 24). Neither recommendation is based on systematic syntheses of available evidence pertaining to thermometer accuracy (15, 25, 26). Many small studies have examined the accuracy of peripheral thermometers and report generally discordant results. Systematic reviews that examined the accuracy of peripheral thermometers in adults were either focused on selectively chosen populations or did not use established meta-analytic methods (27, 28). Meta-analyses examining infrared ear and axillary thermometry compared with a rectal reference standard in children found wide limits of agreement (LOA) (25, 26). Given these drawbacks and the potential for advancements in thermometer technology (25, 26), the accuracy of peripheral thermometers is not well-defined. We therefore did a systematic review and meta-analysis to determine whether peripheral thermometers have clinically acceptable accuracy compared with central thermometers in adults and children and whether the type of peripheral thermometer is an important determinant of accuracy. Methods The primary objective was to determine the LOA in temperature between peripheral and central thermometers (29). The secondary objective was to determine the diagnostic accuracy (sensitivity, specificity, and positive and negative likelihood ratios) of peripheral thermometers for detecting fever or hypothermia. Methods for article inclusion and data analysis were prespecified in a protocol (not registered) and consistent with major systematic review reporting guidelines (3032). Data Sources and Searches We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and CINAHL Plus for studies that compared the accuracy of peripheral thermometers with a central reference standard from inception to September 2014; we subsequently updated our search to 20 July 2015. In the MEDLINE and Cochrane Central Register of Controlled Trials searches, we used a combination of exploded Medical Subject Heading terms and text words that included synonyms for thermometer and validated filters for clinical trials (33), cohort studies (34), and diagnostic accuracy studies (Appendix Table 2) (35). The search strategy included similar combinations of terms and filters within the other databases and did not have any language restrictions. Additional citations were located using the related articles feature in PubMed and by hand-searching bibliographies of included studies, previously published reviews (15, 2528, 3640), and relevant societal guidelines (2124). Finally, 2 international clinical trial registries were searched to identify potentially relevant unpublished studies (41, 42). Appendix Table 2. MEDLINE Search Strategy* Selection Criteria Before reviewing all citations, 2 reviewers calibrated the citation screening form by reviewing 25 randomly selected citations. All titles and abstracts were then independently reviewed in duplicate. The full text of selected citations was then reviewed (in duplicate) against the inclusion and exclusion criteria. We used the following inclusion criteria: prospective study design (randomized clinical trial, controlled clinical trial, cohort study, or diagnostic accuracy study) of adults (aged 18 years) or children (aged <18 years) managed in acute care or ambulatory facilities; peripheral index thermometers included tympanic membrane, temporal artery, axillary (electronic, mercury, or chemical dot), or oral (electronic or mercury) thermometers (21, 23, 25, 26); central reference thermometers included pulmonary artery catheters or urinary bladder, esophageal, or rectal thermometers (21, 23, 25, 26); paired temperature measurements between index and reference thermometers were obtained within 5 minutes of one another; and mean difference and associated variance (SD or 95% CI) were reported for each indexreference comparison. The rectal thermometer was included as a central reference device because it is commonly viewed as invasive (22, 23, 26), frequently used in pediatric studies as the reference standard (25, 26), and listed in guidelines as being one of the most accurate thermometers (21). Exclusion criteria were as follows: casecontrol study, animal study, study population included healthy volunteers without medical concerns evaluated in nonclinical environments, or data presented in graphical format only. Noncontact infrared thermometers were excluded because they are not currently reported as a commonly used device for measuring temperature in clinical environments (18). Articles were excluded if they did not explicitly indicate that the mean difference estimates were derived using methods appropriate for repeated measures data (29). NonEnglish-language studies were translated and evaluated for inclusion. Agreement between authors at each stage of citation review was quantified using statistics. Data Extraction and Quality Assessment Data were abstracted independently and in duplicate, including the mean difference (and variance) in temperature between the index and reference thermometers and the data required to calculate the sensitivity and specificity for detecting fever and hypothermia (that is, the number of true-positive, false-positive, true-negative, and false-negative results). Data extraction that related to study quality included domains of the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies-2) tool (43), whether the index thermometer was calibrated, and whether users received training in proper index thermometer use. Corresponding authors of selected articles were contacted for missing information as required. Data Synthesis and Analysis The primary meta-analysis determined the 95% LOA between peripheral and central thermometers; this was calculated as the pooled estimate of the mean difference in temperature measurements (peripheral minus central) 2 times the pooled estimate of the SD of the difference (29, 44). The prespecified and clinically acceptable 95% LOA were0.5C (4547). Data were pooled using a random-effects model (48), reported as the pooled mean difference (95% CI), and converted to 95% LOA. Study weights were adjusted for several indexreference comparisons. When a study used the same population to examine the accuracy of multiple index thermometers, the total study population was divided by the number of different index comparisons for pooled analyses (26); for studies that compared a given index thermometer with several reference thermometers, we restricted analyses to comparisons with the pulmonary artery catheter. The validity of pooling data across the 4 reference thermometers was examined by determining the pooled 95% LOA between each nonvascular thermometer (bladder, esophageal, or rectal) and the pulmonary artery catheter (gold standard) (21). The secondary meta-analysis determined the diagnostic accuracy of peripheral thermometers for detecting fever or hypothermia using the analytic approach outlined by the Cochrane Diagnostic Test Accuracy Working Group (32). Individual study estimates of sensitivity and specificity were determined from 22 contingency tables and used to develop the summary receiver-operating characteristic curve. Pooled estimates of sensitivity, specificity, and positive and negative likelihood ratios were then determined via bivariate random-effects models (49, 50). Interstudy heterogeneity was evaluated using the Cochran Q test and the I 2 statistic, wherein a P value less than 0.05 and an I 2 statistic greater than 25% reflected statistical evidence of interstudy heterogeneity (51). Sources of heterogeneity were examined by stratified analyses and metaregression (51). Prespecified subgroups included those pertaining to the study participants (adult vs. pediatric and medical vs. surgical), study method (high vs. low risk of bias), thermometers (index measurement site, index method of operation, index thermometer brand, user training, thermometer calibration, and type of reference standard), and temperature (fever and hypothermia). Publication bias was assessed by inspecting funnel plots and doing the Begg (primary meta-analysis) and Deek (secondary meta-analysis) funnel plot asymmetry tests (P< 0.1 was considered evidence of publication bias) (52, 53). Analyses were done in Stata, version 13.1 (Stata Corp) (54, 55). Role of the Funding Source This study received no funding. Results Study Selection and Description From 2563 citations, 75 were included in the systematic review (= 0.8 for both stages of citation review) (Appendix Figure 1). The most common reasons for exclusion after full-text review were the lack of simultaneous index and reference thermometer measurements (36%) and data pertaining to the mean difference between index and reference thermometers (34%). Sixty-nine articles were included in the primary meta

Diagnostic accuracy of computed tomographic angiography for blunt cerebrovascular injury detection in trauma patients: a systematic review and meta-analysis.

Objective:To compare the diagnostic accuracy of computed tomographic angiography (CTA) with digital subtraction angiography (DSA) for blunt cerebrovascular injury (BCVI) detection in trauma patients. Background:Controversy exists as to whether the diagnostic performance of CTA compares favorably with the reference-standard, DSA. Methods:We searched electronic databases (1950 to May 22, 2012), article bibliographies, conference proceedings (2008–2011), and clinical trial registries for studies comparing the accuracy of CTA with DSA for BCVI detection in trauma patients. Pooled estimates of sensitivity, specificity, and positive and negative likelihood ratios were calculated using bivariate random effects models. Results:Eight studies that examined 5704 carotid or vertebral arteries in 1426 trauma patients met inclusion criteria. The pooled sensitivity and specificity for BCVI detection with CTA versus DSA was 66% (95% CI, 49%–79%; I2 = 80.4%) and 97% (95% CI, 91%–99%; I2 = 94.6%), respectively. Corresponding pooled positive and negative likelihood ratios were 20.0 (95% CI, 6.9–58.4; I2 = 87.7%) and 0.35 (95% CI, 0.22–0.56; I2 = 74.9%), respectively. Although pooled sensitivity varied with the number of available CT slices, the training of interpreting radiologists, and in a pattern suggestive of differences in diagnostic threshold for judging CTA positivity, it remained 80% or less among studies that used scanners with 16 or more slices per rotation and where the CTA was read by neuroradiologists. Conclusions:Existing evidence suggests that the diagnostic performance of CTA varies considerably across studies, likely due to an implicit variation in diagnostic threshold across trauma centers. Moreover, although CTA appears to lack sensitivity to adequately rule out BCVI, it may be useful to rule in BCVI among trauma patients with a high pretest probability of injury.