Size Matters: The Influence of Patient Size on Antibiotics Exposure Profiles in Critically Ill Patients on Continuous Renal Replacement Therapy

(1) Purpose of this study: To determine whether patient weight influences the probability of target attainment (PTA) over 72 h of initial therapy with beta-lactam (cefepime, ceftazidime, piperacillin/tazobactam) and carbapenem (imipenem, ertapenem, meropenem) antibiotics in the critical care setting. This is the first paper to address the question of whether patient size affects antibiotic PTA in the ICU. (2) Methods: We performed a post hoc analysis of Monte Carlo simulations conducted in virtual critically ill patients receiving antibiotics and continuous renal replacement therapy. The PTA was calculated for each antibiotic on the following pharmacodynamic (PD) targets: (a) were above the target organism’s minimum inhibitory concentration (≥%fT≥1×MIC), (b) were above four times the MIC (≥%fT≥4×MIC), and (c) were always above the MIC (≥100%fT≥MIC) for the first 72 h of antibiotic therapy. The PTA was analyzed in patient weight quartiles [Q1 (lightest)-Q4 (heaviest)]. Optimal doses were defined as the lowest dose achieving ≥90% PTA. (3) Results: The PTA for fT≥1×MIC led to similarly high rates regardless of weight quartiles. Yet, patient weight influenced the PTA for higher PD targets (100%fT≥MIC and fT≥4×MIC) with commonly used beta-lactams and carbapenems. Reaching the optimal PTA was more difficult with a PD target of 100%fT≥MIC compared to fT≥4×MIC. (4) Conclusions: The Monte Carlo simulations showed patients in lower weight quartiles tended to achieve higher antibiotic pharmacodynamic target attainment compared to heavier patients.

Transplastron Enterocentesis to Manage Buoyancy Disorder in an Adult Loggerhead Sea Turtle (Caretta caretta)

Buoyancy disorder in sea turtles is a common condition that contributes to increased morbidity and mortality in the wild and because of this, is often encountered in rehabilitation facilities. The pathological gas accumulation that is a sequelae of this disorder can create challenges in treatment of this disease, especially when concurrent systemic disease is present. These challenges increase with patient size, as anatomy and location of pathology makes gas evacuation more difficult utilizing conventional methods when medical therapy alone is unsuccessful. This report discusses a novel technique utilizing ultrasonic-guided transplastron enterocentesis of the proximal gastrointestinal tract in an adult loggerhead sea turtle ( Caretta caretta ) with suspected intestinal obstruction. The sea turtle presented with positive buoyancy and routine workup revealed gas accumulation in the gastrointestinal tract, as well as concurrent pneumonia. Medical therapy alone did not diminish the positive buoyancy or gastrointestinal distension. Ultrasonic-guided transplastron enterocentesis was performed via the connective tissue lateral to the 3rd inframarginal scute while the turtle was positioned with its left side raised, allowing any gas-filled intestine to be positioned laterally. Approximately 10.3 L of gas were evacuated from the proximal gastrointestinal lumen and within 15 mins, the turtle was neutrally buoyant. It continued to exhibit normal surfacing, diving, and resting behavior. The turtle was released 111 days after enterocentesis in order to allow treatment of the concurrent pneumonia. The technique discussed in this report has implications for improving treatment of buoyancy disorder in large adult sea turtles and increasing likelihood of release.

Estimating Specific Patient Organ Dose for Chest CT Examinations with Monte Carlo Method

Purpose: The purpose of this study was to preliminarily estimate patient-specific organ doses in chest CT examinations for Chinese adults, and to investigate the effect of patient size on organ doses. Methods: By considering the body-size and body-build effects on the organ doses and taking the mid-chest water equivalent diameter (WED) as a body-size indicator, the chest scan images of 18 Chinese adults were acquired on a multi-detector CT to generate the regional voxel models. For each patient, the lungs, heart, and breasts (glandular breast tissues for both breasts) were segmented, and other organs were semi-automated segmented based on their HU values. The CT scanner and patient models simulated by MCNPX 2.4.0 software (Los Alamos National LaboratoryLos Alamos, USA) were used to calculate lung, breast, and heart doses. CTDIvol values were used to normalize simulated organ doses, and the exponential estimation model between the normalized organ dose and WED was investigated. Results: Among the 18 patients in this study, the simulated doses of lung, heart, and breast were 18.15 ± 2.69 mGy, 18.68 ± 2.87 mGy, and 16.11 ± 3.08 mGy, respectively. Larger patients received higher organ doses than smaller ones due to the higher tube current used. The ratios of lung, heart, and breast doses to the CTDIvol were 1.48 ± 0.22, 1.54 ± 0.20, and 1.41 ± 0.13, respectively. The normalized organ doses of all the three organs decreased with the increase in WED, and the normalized doses decreased more obviously in the lung and the heart than that in the breasts. Conclusions: The output of CT scanner under ATCM is positively related to the attenuation of patients, larger-size patients receive higher organ doses. The organ dose normalized by CTDIvol was negatively correlated with patient size. The organ doses could be estimated by using the indicated CTDIvol combined with the estimated WED.

The effective and water-equivalent diameters as geometrical size functions for estimating CT dose in the thoracic, abdominal, and pelvic regions

Purpose: The aim of this work was to establish the relationships of patient size in terms of effective diameter (Deff) and water-equivalent diameter (Dw) with lateral (LAT) and anterior-posterior (AP) dimensions in order to predict the specific patient dose for thoracic, abdominal, and pelvic computed tomography (CT) examinations. Methods: A total of 47 thoracic images, 79 abdominal images, and 50 pelvic images were analyzed in this study. The patient’s images were retrospectively collected from Dr. Kariadi and Kensaras Hospitals, Semarang, Indonesia. The slices measured were taken from the middle of the scan range. The calculations of patient sizes (LAT, AP, Deff, and Dw) were automatically performed by IndoseCT 20b software. Deff and Dw were plotted as functions of LAT, AP, and AP+LAT. In addition, Dw was plotted as a function of Deff. Results: Strong correlations of Deff and Dw with LAT, AP, and AP+LAT were found. Stronger correlations were found in the Deff curves (R2 > 0.9) than in the Dw curves (R2 > 0.8). It was found that the average Deff was higher than the average Dw in the thoracic region, the average values were similar in the abdominal and pelvic regions. Conclusion: The current study extended the study of the relationships between Deff and Dw and the basic geometric diameter LAT, AP, and AP+LAT beyond those previously reported by AAPM. We evaluated the relationships for three regions, i.e. thoracic, abdominal, and pelvic regions. Based on our findings, it was possible to estimate Deff and Dw from only the LAT or AP dimension.

The Use of Robotics Coupled With Navigation for Pediatric Congenital Spine Deformity

Background: Spinal instrumentation in children with congenital spine deformity poses challenges to the surgeon, given the small patient size and the anomalous anatomy often encountered. Purpose: We aimed to investigate the accuracy of screw placement when robotics coupled with real-time navigation was used for surgical treatment of pediatric congenital spine deformity at 1 institution. Methods: We conducted a retrospective search of our institution’s database for all patients younger than 18 years of age with congenital spine deformity who were treated with the robotics surgical platform coupled with navigation between June 2019 and December 2020. We recorded data on demographics, location and type of anomaly, procedure performed, and intraoperative variables related to robotics and navigation. We reviewed the images of patients who had intraoperative 3-dimensional imaging or postoperative computed tomographic scans to determine the accuracy of screw placement using the Gertzbein-Robbins scale. Results: In 14 patients identified, a total of 95 screws were attempted, with 94 successfully placed using robotics coupled with navigation. There were no noted screw-related complications (neurologic or visceral) and no return to the operating room for screw malposition. Conclusion: Patients with congenital spine deformity present potentially unique challenges due to variant anatomy. This retrospective series suggests that robotics coupled with navigation for congenital spine deformity correction in the pediatric population may aid in accurate screw placement and reduce complication rates. More rigorous study is warranted.