Perceptions of general surgery residents at military treatment facilities: Excellent training with crisis of confidence.

BACKGROUND: The declining operative volume at Military Treatment Facilities (MTFs) has resulted in Program Directors finding alternate civilian sites for resident rotations. The continued shift away from MTFs for surgical training is likely to have unintended negative consequences. METHODS: An anonymous survey was generated and sent to the program directors of military general surgery training programs for distribution to their residents. RESULTS: A total of 42 residents responded (response rate 21%) with adequate representation from all PGY years. Ninety-five percent of residents believed that their programs provided the training needed to be a competent general surgeon. However, when asked about career choices, only 30.9% reported being likely/extremely likely to remain in the military beyond their initial service obligation, while 54.7% reported that it was unlikely/extremely unlikely and 19% reported uncertainty. Eighty-eight percent reported that decreasing MTF surgical volume directly influenced their decision to stay in the military, and half of respondents regretted joining the military. When asked to assess their confidence in the military to provide opportunities for skill sustainment as a staff surgeon, 90.4% were not confident or were neutral. CONCLUSION: Although military surgical residents have a generally positive perception of their surgical training, they also lack confidence in their future military surgical careers. Our findings suggest that declining MTF surgical volume will likely negatively impact long-term retention of military surgeons and may negatively impact force generation for Operational Commander. LEVEL OF EVIDENCE: Prognostic and Epidemiological, Level IV.

Machine Learning Differentiates Extracorporeal Membrane Oxygenation Mortality Risk Profiles Among Trauma Patients.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) is resource intensive with high mortality. Identifying trauma patients most likely to derive a survival benefit remains elusive despite current ECMO guidelines. Our objective was to identify unique patient risk profiles using the largest database of trauma patients available. METHODS: ECMO patients ≥16 years were identified using Trauma Quality Improvement Program data (2010-2019). Machine learning K-median clustering (ML) utilized 101 variables including injury severity, demographics, comorbidities, and hospital stay information to generate unique patient risk profiles. Mortality and patient and center characteristics were evaluated across profiles. RESULTS: A total of 1037 patients were included with 33% overall mortality, mean age 32 years, and median ISS = 26. The ML identified 3 unique patient risk profile groups. Although mortality rates were equivalent across the 3 groups, groups were distinguished by (Group 1) young (median 25 years), severely injured (ISS = 34) patients with thoracic and head injuries (99%) via blunt mechanism (93%), and a high prevalence of ARDS (77%); (Group 2) relatively young (median 30 years) and moderately injured (ISS = 22) patients with exposure-related injuries (11%); and (Group 3) older (median 46 years) patients with a high proportion of comorbidities (69%) and extremity injuries (100%). There were no differences based on center ECMO volume, teaching status, or ACS-Level across all 3 groups. CONCLUSION: Machine learning compliments traditional analyses by identifying unique mortality risk profiles for trauma patients receiving ECMO. These details can further inform treatment guidelines, clinical decision making, and institutional criteria for ECMO usage.

To the point: Utility of laparoscopy for operative management of stabbing abdominal trauma.

BACKGROUND: Algorithms for managing penetrating abdominal trauma are conflicting or vague regarding the role of laparoscopy. We hypothesized that laparoscopy is underutilized among hemodynamically stable patients with abdominal stab wounds. METHODS: Trauma Quality Improvement Program data (2016-2019) were used to identify stable (SBP ≥110 and GCS ≥13) patients ≥16yrs with stab wounds and an abdominal procedure within 24hr of admission. Patients with a non-abdominal AIS ≥3 or missing outcome information were excluded. Patients were analyzed based on index procedure approach: open, therapeutic laparoscopy (LAP), or LAP-conversion to open (LCO). Center, clinical characteristics and outcomes were compared according to surgical approach and abdominal AIS using non-parametric analysis. RESULTS: 5984 patients met inclusion criteria with 7 â€‹% and 8 â€‹% receiving therapeutic LAP and LCO, respectively. The conversion rate for patients initially treated with LAP was 54 â€‹%. Compared to conversion or open, therapeutic LAP patients had better outcomes including shorter ICU and hospital stays and less infection complications, but were younger and less injured. Assessing by abdominal AIS eliminated ISS differences, meanwhile LAP patients still had shorter hospital stays. At time of admission, 45 â€‹% of open patients met criteria for initial LAP opportunity as indicated by comparable clinical presentation as therapeutic laparoscopy patients. CONCLUSIONS: In hemodynamically stable patients, laparoscopy remains infrequently utilized despite its increasing inclusion in current guidelines. Additional opportunity exists for therapeutic laparoscopy in trauma, which appears to be a viable alternative to open surgery for select injuries from abdominal stab wounds. LEVEL OF EVIDENCE: Prognostic and Epidemiological; Level IV.

Mixed reality surgical mentoring of combat casualty care related procedures in a perfused cadaver model: Initial results of a randomized feasibility study.

BACKGROUND: Most telemedicine modalities have limited ability to enhance procedural and operative care. We developed a novel system to provide synchronous bidirectional expert mixed reality-enabled virtual procedural mentoring. In this feasibility study, we evaluated mixed reality mentoring of combat casualty care related procedures in a re-perfused cadaver model. METHODS: Novices received real-time holographic mentoring from experts using augmented reality via Hololens (Microsoft Inc, Redmond, WA). The experts maintained real-time awareness of the novice's operative environment using virtual reality via HTC-Vive (HTC Corp, Xindian District, Taiwan). Additional cameras (both environments) and novel software created the immersive, shared, 3-dimensional mixed reality environment in which the novice and expert collaborated. The novices were prospectively randomized to either mixed reality or audio-only mentoring. Blinded experts independently evaluated novice procedural videos using a 5-point Likert scale-based questionnaire. Nonparametric variables were evaluated using the Wilcoxon rank-sum test and comparisons using the χ2 analysis; significance was defined at P < .05. RESULTS: Surgeon and nonsurgeon novices (14) performed 69 combat casualty care-related procedures (38 mixed reality, 31 audio), including various vascular exposures, 4-compartment lower leg fasciotomy, and emergency neurosurgical procedures; 85% were performed correctly with no difference in either group. Upon video review, mixed reality-mentored novices showed no difference in procedural flow and forward planning (3.67 vs 3.28, P = .21) or the likelihood of performing individual procedural steps correctly (4.12 vs 3.59, P = .06). CONCLUSION: In this initial feasibility study, our novel mixed reality-based mentoring system successfully facilitated the performance of a wide variety of combat casualty care relevant procedures using a high fidelity re-perfused cadaver model. The small sample size and limited variety of novice types likely impacted the ability of holographically mentored novices to demonstrate improvement over the audio-only control group. Despite this, using virtual, augmented, and mixed reality technologies for procedural mentoring demonstrated promise, and further study is needed.

Is cerebral perfusion maintained during full and partial resuscitative endovascular balloon occlusion of the aorta in hemorrhagic shock conditions?

BACKGROUND: Partial resuscitative endovascular balloon occlusion of the aorta (pREBOA) is a technology that occludes aortic flow and allows for controlled deflation and restoration of varying distal perfusion. Carotid flow rates (CFRs) during partial deflation are unknown. Our aim was to measure CFR with the different pREBOA balloon volumes and correlate those to the proximal mean arterial pressure (PMAP) and a handheld pressure monitoring device (COMPASS; Mirador Biomedical, Seattle, WA). METHODS: Ten swine underwent a hemorrhagic injury model with carotid and iliac arterial pressures monitored via arterial lines. Carotid and aortic flow rates were monitored with Doppler flow probes. A COMPASS was placed to monitor proximal pressure. The pREBOA was inflated for 15 minutes then partially deflated for an aortic flow rate of 0.7 L/min for 45 minutes. It was then completely deflated. Proximal mean arterial pressures and CFR were measured, and correlation was evaluated. Correlation between CRF and COMPASS measurements was evaluated. RESULTS: Carotid flow rate increased 240% with full inflation. Carotid flow rate was maintained at 100% to 150% of baseline across a wide range of partial deflation. After full deflation, CFR transiently decreased to 45% to 95% of baseline. There was strong positive correlation (r > 0.85) between CFR and PMAP after full inflation, and positive correlation with partial inflation (r > 0.7). Carotid flow rate had strong correlation with the COMPASS with full REBOA (r > 0.85) and positive correlation with pREBOA (r > 0.65). CONCLUSION: Carotid flow rate is increased in a hemorrhagic model during full and partial inflation of the pREBOA and correlates well with PMAP. Carotid perfusion appears maintained across a wide range of pREBOA deflation and could be readily monitored with a handheld portable COMPASS device instead of a standard arterial line setup.

Real-time bedside management and titration of partial resuscitative endovascular balloon occlusion of the aorta without an arterial line: Good for pressure, not for flow!

BACKGROUND: Partial resuscitative endovascular balloon occlusion of the aorta (pREBOA) attempts to minimize ischemia/reperfusion injury while controlling hemorrhage. There are little data on optimal methods to evaluate and titrate partial flow, which typically requires invasive arterial line monitoring. We sought to examine the use of a miniaturized handheld digital pressure device (COMPASS; Mirador Biomedical, Seattle, WA) for pREBOA placement and titration of flow. METHODS: Ten swine underwent standardized hemorrhagic shock. Carotid and iliac pressures were monitored with both arterial line and COMPASS devices, and flow was monitored by aortic and superior mesenteric artery flow probes. Partial resuscitative endovascular balloon occlusion of the aorta was inflated to control hemorrhage for 15 minutes before being deflated to try targeting aortic flow of 0.7 L/min (using only the COMPASS device) by an operator blinded to the arterial line pressures and aortic flow. Correlations between COMPASS and proximal/distal arterial line were evaluated, as well as actual aortic flow. RESULTS: There was strong correlation between the distal mean arterial pressure (MAP) and the distal COMPASS MAP (r = 0.979, p < 0.01), as well as between the proximal arterial line and the proximal COMPASS on the pREBOA (r = 0.989, p < 0.01). There was a significant but weaker correlation between the distal compass MAP reading and aortic flow (r = 0.47, p < 0.0001), although it was not clinically significant and predicted flow was not achieved in a majority of the procedures. Of 10 pigs, survival times ranged from 10 to 120 minutes, with a mean survival of 50 minutes, and 1 pig surviving to 120 minutes. CONCLUSION: Highly reliable pressure monitoring is achieved proximally and distally without arterial lines using the COMPASS device on the pREBOA. Despite accurate readings, distal MAPs were a poor indicator of aortic flow, and titration based upon distal MAPs did not provide reliable results. Further investigation will be required to find a suitable proxy for targeting specific aortic flow levels using pREBOA.

Blood transfusion: In the air tonight?

BACKGROUND: The use of prehospital blood transfusion (PBT) in air medical transport has become more widespread. However, the effect of PBT remains unknown. The aim of this study was to examine the impact of PBT on 24-hour and overall in-hospital mortality. METHODS: This is a retrospective cohort study of all trauma patients carried by air medical transport from the scene to a Level I trauma center from 2007 to 2013. We excluded patients who died on the helipad or in the emergency department. Primary outcomes measured were 24-hour and overall in-hospital mortality. Multivariable logistic regressions using all available patient data or the propensity score (for receiving PBT)-matched patient data were performed to study the effect of PBT on these outcomes. RESULTS: Of the 5,581 patients included in the study, 231 (4%) received PBT. Multivariable regression analyses did not show evidence of PBT effect on 24-hour in-hospital mortality (odds ratio [OR], 1.22; 95% confidence interval [CI], 0.61-2.44) and on overall in-hospital mortality (OR, 1.20; 95% CI, 0.55-1.79). In addition, using 1:1 propensity score-matched data, the analysis did not show evidence of PBT effect on 24-hour in-hospital mortality (OR, 1.04; 95% CI, 0.54-1.98) and on overall in-hospital mortality (OR, 1.05; 95% CI, 0.56-1.96). Factors associated with increased 24-hour mortality were advanced age, penetrating injury, increased blood transfusion requirement in the first 24 hours, and decreased Glasgow Coma Scale (GCS) score (p < 0.05). These factors were also associated with overall mortality, in addition to increased Injury Severity Score (ISS) (p < 0.05). CONCLUSION: This is the largest study to date of trauma patients who received PBT and were transported from the scene by air medical transport. Our results show no effect of PBT on 24-hour and overall in-hospital mortality. Previous studies also suggest no benefit of PBT, which is counterintuitive to damage-control resuscitation. Prospective data on PBT are needed to assess risk, cost, and benefit. LEVEL OF EVIDENCE: Therapeutic study, level III.

Vagal nerve stimulation decreases blood-brain barrier disruption after traumatic brain injury.

BACKGROUND: Traumatic brain injury (TBI) may alter sympathetic tone causing autonomic abnormalities and organ dysfunction. Vagal nerve stimulation (VNS) has been shown to decrease inflammation and distant organ injury after TBI. It is unknown whether VNS may reduce blood-brain barrier (BBB) dysfunction after TBI.We hypothesize that VNS prevents TBI-induced breakdown of the BBB, subsequent brain edema, and neuronal injury. METHODS: A weight-drop model was used to create severe TBI in balb/c mice. Animals were divided into three groups: TBI-TBI only; TBI or VNS--animals that were treated with 10 minutes of VNS immediately before TBI; and sham--animals with opening of the skull but no TBI and VNS treatment. Brain vascular permeability to injected (Mr 70,000) FITC-dextran was measured by radiated fluorescence 6 hours after injury. Injured tissue sections were stained for perivascular aquaporin 4 (AQP-4), an important protein causing BBB--mediated brain edema. Fluorescence was quantified under laser scanning by confocal microscopy. RESULTS: Six hours after TBI, cerebral vascular permeability was increased fourfold compared with sham (mean [SD], 6.6(E+08) [5.5(E+07)] arbitrary fluorescence units [afu] vs. 1.5(E+08) [2.9(E+07)] afu; p G 0.001). VNS prevented the increase in permeability when compared with TBI alone (mean [SD], 3.5 (E+08) [8.3(E+07)] afu vs. 6.6(E+08) [5.5(E+07)] afu; p G 0.05). Perivascular expression of AQP-4 was increased twofold in TBI animals compared with sham (mean [SD], 0.96 [0.12] afu vs. 1.79 [0.37] afu; p G 0.05). Similarly, VNS decreased post-TBI expression of AQP-4 to levels similar to sham (mean [SD], 1.15 [0.12] afu; p G 0.05). CONCLUSION: VNS attenuates cerebral vascular permeability and decreases the up-regulation of AQP-4 after TBI. Future studies are needed to assess the mechanisms by which VNS maintains the BBB.

Ghrelin prevents disruption of the blood-brain barrier after traumatic brain injury.

Significant effort has been focused on reducing neuronal damage from post-traumatic brain injury (TBI) inflammation and blood-brain barrier (BBB)-mediated edema. The orexigenic hormone ghrelin decreases inflammation in sepsis models, and has recently been shown to be neuroprotective following subarachnoid hemorrhage. We hypothesized that ghrelin modulates cerebral vascular permeability and mediates BBB breakdown following TBI. Using a weight-drop model, TBI was created in three groups of mice: sham, TBI, and TBI/ghrelin. The BBB was investigated by examining its permeability to FITC-dextran and through quantification of perivascualar aquaporin-4 (AQP-4). Finally, we immunoblotted for serum S100B as a marker of brain injury. Compared to sham, TBI caused significant histologic neuronal degeneration, increases in vascular permeability, perivascular expression of AQP-4, and serum levels of S100B. Treatment with ghrelin mitigated these effects; after TBI, ghrelin-treated mice had vascular permeability and perivascular AQP-4 and S100B levels that were similar to sham. Our data suggest that ghrelin prevents BBB disruption after TBI. This is evident by a decrease in vascular permeability that is linked to a decrease in AQP-4. This decrease in vascular permeability may diminish post-TBI brain tissue damage was evident by decreased S100B.

Efferent vagal nerve stimulation attenuates acute lung injury following burn: The importance of the gut-lung axis.

BACKGROUND: The purpose of this study was to assess acute lung injury when protection to the gut mucosal barrier offered by vagus nerve stimulation is eliminated by an abdominal vagotomy. METHODS: Male balb/c mice were subjected to 30% total body surface area steam burn with and without electrical stimulation to the right cervical vagus nerve. A cohort of animals were subjected to abdominal vagotomy. Lung histology, myeloperoxidase and ICAM-1 immune staining, myeloperoxidase enzymatic assay, and tissue KC levels were analyzed 24 hours after burn. Additionally, lung IkB-α, NF-kB immunoblots, and NF-kB-DNA binding measured by photon emission analysis using NF-kB-luc transgenic mice were performed. RESULTS: Six hours post burn, phosphorylation of both NF-kB p65 and IkB-α were observed. Increased photon emission signal was seen in the lungs of NF-kB-luc transgenic animals. Vagal nerve stimulation blunted NF-kB activation similar to sham animals whereas abdominal vagotomy eliminated the anti-inflammatory effect. After burn, MPO positive cells and ICAM-1 expression in the lung endothelium was increased, and lung histology demonstrated significant injury at 24 hours. Vagal nerve stimulation markedly decreased neutrophil infiltration as demonstrated by MPO immune staining and enzyme activity. Vagal stimulation also markedly attenuated acute lung injury at 24 hours. The protective effects of vagal nerve stimulation were reversed by performing an abdominal vagotomy. CONCLUSION: Vagal nerve stimulation is an effective strategy to protect against acute lung injury following burn. Moreover, the protective effects of vagal nerve stimulation in the prevention of acute lung injury are eliminated by performing an abdominal vagotomy. These results establish the importance of the gut-lung axis after burn in the genesis of acute lung injury.