Antimicrobial Distribution From Local Delivery Depends on Dose

Background

Tissue distribution after local delivery has been quantified over a period of 5 hours on 7-T MRI in a rabbit model using gadolinium-labeled diethylenetriamine pentaacetic acid (Gd-DTPA) as an antimicrobial surrogate; however, it is unknown how the Gd-DTPA load in a local depot will affect the duration of high-concentration Gd-DTPA in local tissues after surgical débridement.

Questions/purposes

We determined whether the Gd-DTPA load in bone cement affected its local tissue distribution over a period of 1 month after local delivery.

Methods

A 1-cm³ soft tissue dead space was created in the quadriceps of seven rabbits and filled with gadolinium-loaded bone cement. At 7, 14, and 33 days, the volume of tissue with a Gd-DTPA concentration of more than 14 μg/mL was calculated from T1-weighted images using 7-T MRI. Differences in volumes of distribution were analyzed with ANOVA.

Results

The volume of tissue with more than 14 μg/mL Gd-DTPA was much larger from higher gadolinium loads on Day 7 (p = 0.02) (2121 mm³ for 10 g and 665 mm³ for 1 g) and smaller with time for the 10-g formulation (2121 mm³ on Day 7 and 1241 mm³ on Day 14).

Conclusions

Volume of distribution and duration of Gd-DTPA after local delivery increased with increasing load in the cement and decreased with time.

Clinical Relevance

For local delivery, high antimicrobial concentrations would be expected in greater volumes of tissue, for longer durations, when higher antimicrobial loads are used.     

Cervical spine computed tomography utilization in pediatric trauma patients

Background

Guidelines for evaluating the cervical spine in pediatric trauma patients recommend cervical spine CT (CSCT) when plain radiographs suggest an injury. Our objective was to compare usage of CSCT between a pediatric trauma center (PTC) and referral general emergency departments (GEDs).

Methods

Patient data from a pediatric trauma registry from 2002 to 2011 were analyzed. Rates of CSI and CSCT of patients presenting to the PTC and GED were compared. Factors associated with use of CSCT were assessed using multivariate logistic regression.

Results

5148 patients were evaluated, 2142 (41.6%) at the PTC and 3006 (58.4%) at the GED. Groups were similar with regard to age, gender, GCS, and triage category. GED patients had a higher median ISS (14 vs. 9, p < 0.05) and more frequent ICU admissions (44.3% vs. 26.1% p < 0.05). CSI rate was 2.1% (107/5148) and remained stable. CSCT use increased from 3.5% to 16.1% over time at the PTC (mean 9.6% 95% CI = 8.3, 10.9) and increased from 6.8% to 42.0% (mean 26.9%, CI = 25.4, 28.4) at the GED. Initial care at a GED remained strongly associated with CSCT.

Conclusions

Despite a stable rate of CSI, rate of CSCT increased significantly over time, especially among patients initially evaluated at a GED.     

CT scan-detected pneumoperitoneum: An unreliable predictor of intra-abdominal injury in blunt trauma

Introduction

Free intra-peritoneal air in blunt trauma is a classic sign associated with hollow viscus injury, traditionally mandating laparotomy. In blunt abdominal trauma, the CT scan has become the diagnostic modality of choice. The increased sensitivity of CT scans may lead to detection of free intra-peritoneal air that is not clinically significant.

Objective

To characterize conditions and findings that allow for the safe observation of blunt trauma patients with free air and to propose a patient management algorithm to decrease rates of non-therapeutic laparotomy.

Design

A retrospective review of 5877 blunt trauma patients who had an abdominal CT scan upon admission to our hospital from 2003 to 2011. A secondary CT review was performed by a single radiologist to further characterize the CT findings in the 74 patients with free air reported on initial scan. Management and hospital course were reviewed in these patients.

Results

Of the 74 patients with intra-abdominal free air, 36 patients with a benign clinical picture were observed and 38 patients underwent urgent exploratory laparotomy. Eleven patients received a non-therapeutic laparotomy. The majority (61%) of patients, 45 of 74, had free air and no significant injury suggesting the presence of benign free air. Patients who had intra-abdominal injury also typically had other clinical or radiologic signs of injury. Findings that were highly predictive of intra-abdominal injury in the setting of free air were free fluid (P < 0.001), radiographic signs of bowel trauma (P < 0.001) as well as clinical and/or radiographic seatbelt sign (P = 0.004).

Conclusions

CT scans may detect free air that is not always clinically significant. Free fluid, seatbelt sign or radiographic signs of bowel trauma in the presence of pneumoperitoneum is highly predictive of injury and these patients should be explored. Based on the results of our study, we created an algorithm to aid in identifying those patients with intra-abdominal free air who may be observed safely.