Prevalence and Clinical Import of Thoracic Injury Identified by Chest Computed Tomography but Not Chest Radiography in Blunt Trauma: Multicenter Prospective Cohort Study.

STUDY OBJECTIVE: Chest computed tomography (CT) diagnoses more injuries than chest radiography, so-called occult injuries. Wide availability of chest CT has driven substantial increase in emergency department use, although the incidence and clinical significance of chest CT findings have not been fully described. We determine the frequency, severity, and clinical import of occult injury, as determined by changes in management. These data will better inform clinical decisions, need for chest CT, and odds of intervention. METHODS: Our sample included prospective data (2009 to 2013) on 5,912 patients at 10 Level I trauma center EDs with both chest radiography and chest CT at physician discretion. These patients were 40.6% of 14,553 enrolled in the parent study who had either chest radiography or chest CT. Occult injuries were pneumothorax, hemothorax, sternal or greater than 2 rib fractures, pulmonary contusion, thoracic spine or scapula fracture, and diaphragm or great vessel injury found on chest CT but not on preceding chest radiography. A priori, we categorized thoracic injuries as major (having invasive procedures), minor (observation or inpatient pain control >24 hours), or of no clinical significance. Primary outcome was prevalence and proportion of occult injury with major interventions of chest tube, mechanical ventilation, or surgery. Secondary outcome was minor interventions of admission rate or observation hours because of occult injury. RESULTS: Two thousand forty-eight patients (34.6%) had chest injury on chest radiography or chest CT, whereas 1,454 of these patients (71.0%, 24.6% of all patients) had occult injury. Of these, in 954 patients (46.6% of injured, 16.1% of total), chest CT found injuries not observed on immediately preceding chest radiography. In 500 more patients (24.4% of injured patients, 8.5% of all patients), chest radiography found some injury, but chest CT found occult injury. Chest radiography found all injuries in only 29.0% of injured patients. Two hundred and two patients with occult injury (of 1,454, 13.9%) had major interventions, 343 of 1,454 (23.6%) had minor interventions, and 909 (62.5%) had no intervention. Patients with occult injury included 514 with pulmonary contusions (of 682 total, 75.4% occult), 405 with pneumothorax (of 597 total, 67.8% occult), 184 with hemothorax (of 230 total, 80.0% occult), those with greater than 2 rib fractures (n=672/1,120, 60.0% occult) or sternal fracture (n=269/281, 95.7% occult), 12 with great vessel injury (of 18 total, 66.7% occult), 5 with diaphragm injury (of 6, 83.3% occult), and 537 with multiple occult injuries. Interventions for patients with occult injury included mechanical ventilation for 31 of 514 patients with pulmonary contusion (6.0%), chest tube for 118 of 405 patients with pneumothorax (29.1%), and 75 of 184 patients with hemothorax (40.8%). Inpatient pain control or observation greater than 24 hours was conducted for 183 of 672 patients with rib fractures (27.2%) and 79 of 269 with sternal fractures (29.4%). Three of 12 (25%) patients with occult great vessel injuries had surgery. Repeated imaging was conducted for 50.6% of patients with occult injury (88.1% chest radiography, 11.9% chest CT, 7.5% both). For patients with occult injury, 90.9% (1,321/1,454) were admitted, with 9.1% observed in the ED for median 6.9 hours. Forty-four percent of observed patients were then admitted (4.0% of patients with occult injury). CONCLUSION: In a more seriously injured subset of patients with blunt trauma who had both chest radiography and chest CT, occult injuries were found by chest CT in 71% of those with thoracic injuries and one fourth of all those with blunt chest trauma. More than one third of occult injury had intervention (37.5%). Chest tubes composed 76.2% of occult injury major interventions, with observation or inpatient pain control greater than 24 hours in 32.4% of occult fractures. Only 1 in 20 patients with occult injury was discharged home from the ED. For these patients with blunt trauma, chest CT is useful to identify otherwise occult injuries.

Yield and clinical predictors of thoracic spine injury from chest computed tomography for blunt trauma.

INTRODUCTION: Cost and radiation risk have prompted intense examination of trauma patient imaging. A proposed decision instrument (DI) for the use of chest computed tomography (CT), (CCT) in blunt trauma patients includes thoracic spine (TS) tenderness, altered mental status (AMS) and distracting painful injury (DPI) as potential predictor variables. TS CT is a separate, costly study whose value is currently ill-defined. The objective of this study is to determine test characteristics of these predictor variables alone, and in combination, to derive a TS injury DI. METHODS: Prospective cohort study of blunt trauma patients age > 14 in a Level I Trauma Center who had either CCT or TS CT. RESULTS: Of 1,798 blunt trauma patients, 1,174 (65.3%) had CCT, and 46 (2.6%) had a TS CT at physician discretion. CCT identified 58 TS injuries in 1,220 patients (4.8%). For 1,032 patients without AMS, 18/35 had TS tenderness, for sensitivity of 51.4%, specificity 84.7%, positive (PPV) and negative predictive values (NPV) of 10.5% and 98.0%. Positive likelihood ratio (+LR) was 3.35, with negative (-LR) 0.57. Among the 58 TS injuries, 23 had AMS for sensitivity of 39.7%, with other test characteristics of 85.8%, 12.2%, 96.6%, with +LR 2.79 and -LR 0.70. Thirty-eight of 58 had DPI, for sensitivity 65.5%, with other test characteristics 65.7%, 8.7%, and 97.4%, with +LR 1.91 and -LR 0.52. Combining 3 predictor variables into a proposed DI found 56/58 injuries for test characteristics of 96.6% (95% CI 88.1-99.6%), 49.1% (46.1-52.0%), 8.6% (6.6-11.1%) and 99.7% (CI 98.7-100%), with +LR 1.90 (1.76-2.04) and -LR 0.07 (0.02-0.28). If validated, the DI would exclude 572/1,220 CCT patients from separate TS CT (46.9%, CI 44.1-49.7%), and 141/511 (27.6%, CI 23.8-31.7%) patients who actually had TS CT in our cohort. Medicare payment at our center for sagittal reconstructions of TS CT is $280 for professional plus technical charges ($3,312 per study). The DI, if validated, would save $39,000-$160,000 in TS imaging payments. CONCLUSION: TS CT is low yield and costly. Patients who are alert, have no TS tenderness and no DPI have a very low likelihood of TS injury (NPV 99.7% 95% CI lower limit 98.7%) with -LR=0.07, 95% CI upper limit 0.28). Avoiding TS CT may save considerable charges and payments.

The "Refrige-a-RAT-or": an accurate, inexpensive, and clinically relevant small animal model of therapeutic hypothermia.

BACKGROUND: Physical and molecular mechanisms for the neuroprotective effect of therapeutic hypothermia are not completely understood, and new therapeutic applications incorporating hypothermia remain to be developed and tested. Clinically relevant animal models of therapeutic hypothermia are not well established or consistent. OBJECTIVES: The objective was to develop and test an inexpensive small animal therapeutic hypothermia system that models those in widespread clinical use and verify that such a system confers neuroprotection in a rat model of global brain ischemia. METHODS: A water-cooled extracorporeal system and attendant anesthesia/sedation protocol were developed and tested. In Stage 1, animals were instrumented for brain, temporalis, and rectal temperature monitoring, and the system was tested for its effect on temperature and hemodynamics. In Stage 2, animals were instrumented for rectal temperature only, subjected to global brain ischemia by two-vessel occlusion and hypotension for 8 minutes, and given either sham therapy (37°C) or hypothermia (32°C) for 4 hours. Viable CA1 neurons were counted at 7 days. RESULTS: The system was well tolerated, provided exquisite control of animal core and brain temperatures, and conferred robust neuroprotection at 7 days. The median and interquartile ranges (IQRs) of viable neurons per 300-µm field were 130 (IQR = 128 to 135) for sham control, 19 (IQR = 15 to 30) for untreated ischemic animals, and 101 (IQR = 94 to 113) for ischemic animals treated with hypothermia (p < 0.05 for comparison between all groups). CONCLUSIONS: Like human protocols, this model incorporates sedation and analgesia, results in robust neuroprotection, is well tolerated, and offers exquisite temperature control. The system is noninvasive and inexpensive and offers a model that is similar to methods used in clinical practice. This system will be of interest to investigators using small animal models to examine neuroprotective mechanisms of hypothermia and translational strategies that combine hypothermia with targeted pharmacotherapy.

The effect of P-glycoprotein on paclitaxel brain and brain tumor distribution in mice.

It may be inferred from the presence of P-glycoprotein (Pgp) in brain capillaries that this drug efflux pump is a factor in limiting the penetration of certain agents into brain tumors. However, by contrast with normal brain capillaries which constitute the blood-brain barrier, brain tumor capillaries are compromised or "leaky," and the extent to which Pgp expression in brain tumor neovasculature retains its capacity to limit drug penetration has not been determined. To address this question, we studied the normal brain and brain tumor distribution of paclitaxel (PAC), a known Pgp substrate, using steady-state PAC dosing regimens in wild-type and Pgp knockout (mdr1a -/- and mdr1b -/-) mice bearing an intracerebral B-16 melanoma. At comparable steady-state PAC plasma concentrations of approximately 5 microg/ml, steady-state PAC brain concentrations in Pgp knockout mice were approximately 3-, 1.8-, and 1.7-fold greater in left brain, right brain, and brain tumor, respectively, than in wild-type mice and statistically different (P < 0.05) in each brain region. Determination of the steady-state brain/plasma concentration ratios or partition coefficients, which take into account any differences in plasma concentrations between each group, indicated a similar pattern as did the absolute brain concentrations. It is concluded that even in the neovasculature of brain tumors, Pgp has the facility to limit drug penetration, although somewhat less so than in normal brain.

Peripheral benzodiazepine receptor ligand-melphalan conjugates for potential selective drug delivery to brain tumors.

To gain insight into the strategy to target PBR ligand-drug conjugates to brain tumors, novel N-imidazopyridinacetyl-melphalan conjugates and the corresponding ethyl esters have been prepared and evaluated for their cytotoxicity in melphalan-sensitive human (SF126, SF188) and rat (RG-2) glioma cell lines. These conjugates exhibited PBR binding affinity with IC(50) values ranging from 57 and 2614 nM. By a computational approach it can be predicted that these conjugates possess significant brain penetration. The stability of the conjugates in 0.05 M phosphate buffer at pH 7.4 and, in some cases, in dilute human serum solution was determined. All the ethyl ester derivatives were stable in 0.05 M phosphate buffer at pH 7.4 and their half-lives exceeded 28 h. Conversely, under the same conditions, the corresponding acids were found to undergo a fast cleavage within a few minutes. HPLC-MS analysis of the mixture from degradation in buffer and physiological medium of the representative cases allowed the identification of their main degradation products. A plausible degradation pathway accounting for the available experimental data is presented.

Pharmacodynamic-mediated effects of the angiogenesis inhibitor SU5416 on the tumor disposition of temozolomide in subcutaneous and intracerebral glioma xenograft models.

The objective of this study was to determine the tumor distribution of temozolomide, an alkylating agent, in the absence and presence of the angiogenesis inhibitor 3-[(2,4-dimethylpyrrol-5-yl)methylidenyl]indolin-2-one (SU5416), a specific vascular endothelial cell growth factor receptor 2 inhibitor. The study was conducted in nude rats bearing either subcutaneous or intracerebral tumors that overexpressed vascular endothelial cell growth factor. For both tumor locations, animals were assigned to either of two treatment groups, SU5416 (25 mg/kg, dissolved in dimethyl sulfoxide) or vehicle control, dimethyl sulfoxide (710 microl/kg) administered i.p. every day for a total of nine doses. Twenty-four hours after the last dose of SU5416 or dimethyl sulfoxide, temozolomide was administrated as a steady-state infusion regimen designed to achieve target plasma concentrations (Cp) of 20 microg/ml. In addition to the measurement of temozolomide Cp, tumor interstitial fluid unbound concentrations of temozolomide were evaluated by microdialysis. In subcutaneous tumors, SU5416 treatment produced a 24% reduction in steady-state temozolomide Ct values (p < 0.05) as well as 21% reductions in tumor/plasma concentration ratios (Ct/Cp; p = 0.11) compared with controls. In intracerebral tumors, steady-state temozolomide Ct and Ct/Cp ratios were significantly increased by 2-fold in the SU5416 treatment group compared with control. The apparent paradoxical effect of SU5416 on the tumor disposition of temozolomide in subcutaneous and intracerebral tumors is discussed in the context of physiological changes (for example, interstitial fluid pressure and microvessel density) and the sampling region in the tumor. It is proposed that the net balance of antiangiogenic drug-mediated pharmacodynamic actions will determine how drug disposition in tumors may be affected.

Biochemical changes associated with a multidrug-resistant phenotype of a human glioma cell line with temozolomide-acquired resistance.

Temozolomide (TMZ) is a newly approved alkylating agent for the treatment of malignant gliomas. To investigate resistance mechanisms in a multidrug therapeutic approach, a TMZ-resistant human glioma cell line, SF188/TR, was established by stepwise exposure of human SF188 parental cells to TMZ for approximately 6 months. SF188/TR showed 6-fold resistance to TMZ and cross-resistance to a broad spectrum of other anticancer agents that included 3-5-fold resistance to melphalan (MEL), gemcitabine (GEM), paclitaxel (PAC), methotrexate (MTX), and doxorubicin (DOX), and 1.6-2-fold resistance to cisplatin (CDDP) and topotecan (TPT). Alkylguanine alkyltransferase (AGT) activity was increased significantly in the resistant cell line compared with the parental cell line (P<0.05), whereas no significant differences occurred in the cellular uptake of TMZ and PAC between resistant and parental cells. Depletion of AGT by O(6)-benzylguanine significantly increased the cytotoxicity of TMZ in both the sensitive and resistant cell lines, but did not influence the cytotoxicity of the other drugs tested. Treatment with TMZ caused SF188 cells to accumulate in S phase, whereas SF188/TR cells were unaffected. Expression of Bcl-2 family members in SF188/TR cells compared with SF188 cells indicated that the pro-apoptotic proteins (i.e. Bad, Bax, Bcl-X(S)) were reduced 2-4-fold in the resistant cell line, whereas the anti-apoptotic proteins Bcl-2 and Bcl-X(L) were expressed at similar levels in both cell lines. In conclusion, the mechanism of resistance of SF188/TR cells to TMZ involved increased activity of AGT, a primary resistance mechanism, whereas the broad cross-resistance pattern to other anticancer drugs was due to a common secondary resistance mechanism related to alterations in the relative expression of the pro-apoptotic and anti-apoptotic proteins.

Cells designed to deliver anticancer drugs by apoptosis.

We describe a new drug delivery strategy that uses genetically engineered endothelial cells (ECs) to deliver drugs to tumor cells by apoptosis. Immortalized ECs were genetically engineered to express a flk-1:fas fusion protein. When exposed to the flk-1 ligand, vascular endothelial growth factor (VEGF), which is overexpressed by many tumors, these cells underwent extensive apoptosis. These apoptotic ECs, when loaded with drug, promote drug delivery by phagocytosis of drug-loaded apoptotic bodies by the tumor cells and by increased drug transport through the more permeable apoptotic membrane. In the current study, severe combined immunodeficient mice bearing s.c. tumors that expressed high levels of VEGF were treated either intratumorally or i.v. every 4 days for a total of five doses with saline control, free Taxol, and immortalized ECs (imECs) expressing the flk-1:fas fusion protein (imEC/HFF) loaded with Taxol (imEC/HFF-T). Intratumoral treatments also included imEC/HFF and imECs loaded with Taxol (imEC-T). Tumor size was monitored for a minimum of 44 days. Whether administered intratumorally or i.v., imEC/HFF-T cells produced greater inhibition of tumor growth than all other treatments, including Taxol. It was noteworthy that 5 of 16 of the imEC/HFF-T-treated animals were tumor free at the termination of the studies, compared with 2 of 16 animals treated with Taxol. A cell distribution experiment showed that flk-1:fas fusion protein expression ECs as well as parental ECs accumulated in tumor and spleen with the highest level, followed by liver, lung, kidney, and brain. Significant apoptosis of flk-1:fas expression cells was observed in tumor, apparently driven by VEGF secreted from tumor cells. Apoptosis-induced drug delivery offers a new avenue for targeted drug delivery research that uses biological control mechanisms.