Evaluation of commercially available point-of-care ultrasound for automated optic nerve sheath measurement.

BACKGROUND: Measurement of the optic nerve sheath diameter (ONSD) via ultrasonography has been proposed as a non-invasive metric of intracranial pressure that may be employed during in-field patient triage. However, first responders are not typically trained to conduct sonographic exams and/or do not have access to an expensive ultrasound device. Therefore, for successful deployment of ONSD measurement in-field, we believe that first responders must have access to low-cost, portable ultrasound and be assisted by artificial intelligence (AI) systems that can automatically interpret the optic nerve sheath ultrasound scan. We examine the suitability of five commercially available, low-cost, portable ultrasound devices that can be combined with future artificial intelligence algorithms to reduce the training required for and cost of in-field optic nerve sheath diameter measurement. This paper is focused on the quality of the images generated by these low-cost probes. We report results of a clinician preference survey and compare with a lab analysis of three quantitative image quality metrics across devices. We also examine the suitability of the devices in a hypothetical far-forward deployment using operators unskilled in ultrasound, with the assumption of a future onboard AI video interpreter. RESULTS: We find statistically significant differences in clinician ranking of the devices in the following categories: "Image Quality", "Ease of Acquisition", "Software", and "Overall ONSD". We show differences in signal-to-noise ratio, generalized contrast-to-noise ratio, point-spread function across the devices. These differences in image quality result in a statistically significant difference in manual ONSD measurement. Finally, we show that sufficiently wide transducers can capture the optic nerve sheath during blind (no visible B-mode) scans performed by operators unskilled in sonography. CONCLUSIONS: Ultrasound of the optic nerve sheath has the potential to be a convenient, non-invasive, point-of-injury or triage measure for elevated intracranial pressure in cases of traumatic brain injury. When transducer width is sufficient, briefly trained operators may obtain video sequences of the optic nerve sheath without guidance. This data suggest that unskilled operators are able to achieve the images needed for AI interpretation. However, we also show that image quality differences between ultrasound probes may influence manual ONSD measurements.

Achieving Mastery of General Surgery Operative Skill in the Army Healthcare System.

INTRODUCTION: Operative case volumes for military surgeons are reported to be significantly lower than civilian counterparts. Among the concern that this raises is an inability of military surgeons to achieve mastery of their craft. MATERIAL AND METHODS: Annual surgical case reports were obtained from seven Army military treatment facilities (MTF) for 2012-2016. Operative case volume and cumulative operative time were calculated for active duty general surgeons and for individual MTFs. Subgroup analyses were also performed based upon rank. Results were extrapolated to calculate the amount of time it would take to reach a cumulative of 10,000 hours of operative time (the a priori definition for achieving mastery). RESULTS: One hundred and two active duty general surgeons operated at the seven MTFs during the study period and met the inclusion criteria. The average surgeon performed 108 ± 68 cases/year. The average surgeon operated 122 ± 82 hours/year. At this rate, it would take over 80 years to reach mastery of surgery. When stratified based upon rank, Majors averaged 113 ± 75 hours/year, Lieutenant Colonels averaged 170 ± 100 hours/year, and Colonels averaged 136 ± 101 hours/year (p < 0.05). When stratified based upon individual MTF, surgeons at the busiest facility averaged 187 ± 103 hours/year and those at the least busy facility averaged 85 ± 56 hours/year (p < 0.05). CONCLUSIONS: Obtaining mastery of general surgery is a nearly impossible proposition given the current care models at Army MTFs. Alternative staffing and patient care models should be developed if Army surgeons are to be masters at their craft.

Special Operations Force Risk Reduction: Integration of Expeditionary Surgical and Resuscitation Teams.

Hemorrhage in the presurgical setting has been the most significant cause of death on the battlefield. Damage control surgery (DCS) near the point of injury (POI) is not a new concept, but having conventional medical teams supporting Special Operations Forces (SOF) beyond robust military medical infrastructure is unique for the US military. The Expeditionary Resuscitative Surgical Team (ERST) was formed by the US Army Medical Command as a pilot team to fulfill a request for forces to provide DCS and personnel recovery near POI.

Clinical practice guideline adherence during Operation Inherent Resolve.

BACKGROUND: The Joint Trauma System (JTS) clinical practice guidelines (CPGs) contributed to the decrease in battlefield mortality over the past 15 years. However, it is unknown to what degree the guidelines are being followed in current military operations. METHODS: A retrospective review was performed of all patients treated at three separate US Army Role II facilities during the first 10 months of Operation Inherent Resolve in Iraq. Charts were reviewed for patient demographics, clinical care, and outcomes. Charts were also reviewed for compliance with JTS CPGs and Tactical Combat Casualty Care recommendations. RESULTS: A total of 114 trauma patients were treated during the time period. The mean age was 26.9 ± 10.1 years, 90% were males, and 96% were host nation patients. The most common mechanisms of injury were blast (49%) and gunshot (42%). Records were compliant with documenting a complete set of vitals in 58% and a pain score in 50% of patients. Recommendations for treatment of hypothermia were followed for 97% of patients. Tranexamic acid was given outside guidelines for 6% of patients, and for 40%, it was not determined if the guidelines were followed. Recommendations for initial resuscitative fluid were followed for 41% of patients. Recommendations for antibiotic prophylaxis were followed for 40% of intra-abdominal and 73% of soft tissue injuries. Recommendations for tetanus prophylaxis were followed for 90% of patients. Deep vein thrombosis prophylaxis was given to 32% of patients and contraindicated in 27%. The recommended transfusion ratio was followed for 56% of massive transfusion patients. Recommendations for calcium administration were followed for 40% of patients. When composite scores were created for individual surgeons, there was significant variability between surgeons with regard to adherence to guidelines. CONCLUSIONS: There is significant deviation in the adherence to the CPGs. LEVEL OF EVIDENCE: Epidemiologic study, level IV.

Hydrogen sulfide improves resuscitation via non-hibernatory mechanisms in a porcine shock model.

BACKGROUND: Hydrogen sulfide (H2S) has been demonstrated to induce a "suspended animation-like" state in rodent models by reversible inhibition of cellular respiration and marked metabolic suppression and has been proposed as a potential pharmacologic adjunct to resuscitation from shock states. There are few data currently available about the mechanisms and efficacy of H2S in larger animals or humans. We examined H2S as a pharmacologic adjunct to resuscitation in a porcine model of severe traumatic shock. METHODS: Twenty-one adult swine were assigned to three study arms: sham, H2S, and saline vehicle controls (SC). All pigs underwent laparotomy and instrumentation, and the two study arms then underwent a 35% controlled hemorrhage followed by 50 min of truncal ischemia via aortic cross-clamp. H2S (5 mg/kg) or saline was administered immediately before reperfusion, followed by 6 h of resuscitation. Resuscitation requirements, laboratory parameters, end-organ histology, and inflammatory product gene expression (by reverse transcription-polymerase chain reaction) were measured and compared between groups. RESULTS: All animals survived to the 6-h postresuscitation time point. Both treatment arms demonstrated severe shock characterized by fluid and vasopressor requirements, metabolic acidosis, and hypotension compared with sham animals. Animals treated with H2S demonstrated significantly lower resuscitative requirements (total epinephrine 727 versus 3052 µg; P < 0.05), decreased fluid requirements, and lower serum lactate levels (7 versus 10 mmol/L) versus SC. Cardiac output was slightly decreased with H2S treatment but all other hemodynamic and metabolic parameters were equivalent between H2S and C groups. Serum liver and kidney biomarkers were unchanged, but administration of H2S was associated with a significant improvement in histopathologic liver and kidney injury scores compared with SC (both P < 0.05). Both study groups demonstrated significantly increased gene expression of hypoxia-inducible factor 1α and nitric oxide synthase (endogenous nitric oxide synthase, inducible nitric oxide synthase [iNOS]2, iNOS3) relative to sham animals. However, H2S was associated with increased expression of hypoxia-inducible factor 1α and decreased iNOS2 levels compared with SC. CONCLUSIONS: Administration of H2S in a large-animal model of severe traumatic shock resulted in a significant decrease in resuscitative requirements, decreased metabolic acidosis, and less end-organ histologic injury compared with standard resuscitation. H2S did not induce profound metabolic suppression as seen in rodents, and appears to have alternative mechanisms of action in large animals.

Acute coagulopathy in a porcine venous hemorrhage and ischemia reperfusion model.

BACKGROUND: Injury-related coagulopathy is a complex process. We analyzed coagulation in a swine model of shock using rotational thromboelastometry (ROTEM). METHODS: Forty-eight swine underwent laparotomy, 35% hemorrhage, supraceliac aortic cross-clamp, then reperfusion and resuscitation. ROTEM measurements and standard labs were taken at baseline and 6 hours into resuscitation. RESULTS: Clot formation time (98 vs 53 seconds, P = .001) and international normalized ratio (1.67 vs 1.01, P < .001) were prolonged after resuscitation. Maximum clot firmness (61 vs 72 mm, P < .001) and fibrinogen levels (94 vs 165, P < .001) declined significantly during resuscitation. Despite decreased fibrinogen levels, there was no significant increase in fibrinolysis as measured by maximum lysis (3.9% vs 3.8%, P = .99). CONCLUSIONS: ROTEM demonstrated the development of an acute coagulopathy. The most significant impacts on coagulopathy were seen with clot initiation and fibrin polymerization. Clot strength decreased over time, although there was little impact on clot breakdown because of fibrinolysis.

Flutamide fails to reduce resuscitation requirements in a porcine ischemia-reperfusion model.

BACKGROUND: Hemorrhagic shock and subsequent resuscitation can lead to ischemia-reperfusion injury, followed by multiorgan failure and death. Flutamide, a vasoactive nonsteroidal antiandrogen compound, is thought to improve tissue and organ perfusion. We tested whether administration of flutamide-cyclodextrin (FLU-CYD) alters physiologic parameters or resuscitation requirements in a porcine model of severe acidosis and shock secondary to combined hemorrhage + ischemia-reperfusion injury. METHODS AND MATERIALS: Fifteen male pigs underwent a 35% blood-volume hemorrhage. Ischemia was induced by cross-clamping the supraceliac aorta for 50 min followed by reperfusion and resuscitation. FLU-CYD complex was administered during aortic clamping. Fluid resuscitation and epinephrine were titrated by protocol to maintain mean arterial pressure ≥40 mm Hg for 6 h. Sequential laboratory results were obtained and serum levels of FLU and 2-hydroxy-flutamide (FLUOH) were measured by mass spectrometry. RESULTS: Mean requirements for injured control swine were 14.6 (± 1.21 standard error of the mean [SEM]) L crystalloid saline and 0.59 (± 0.29 SEM) g epinephrine, compared with 16.30 (± 1.33 SEM) L and 0.54 (± 0.16 SEM) g, respectively, in the FLU-CYD group (both P > 0.05). There were no significant differences in central hemodynamics between control and experimental groups. No significant differences for pH, bicarbonate, fibrinogen, or international normalized ratio were evident. FLU-CYD resuscitation was associated with a significant increase in lactate levels compared with controls (10.1 versus 5.7 mmol/L, P < 0.05). Histologic injury was significantly increased in the livers of FLU-CYD compared with sham (P = 0.022). High serum levels of FLU and the active metabolite FLUOH were measurable throughout the resuscitation period. CONCLUSIONS: Flutamide failed to show any benefit to resuscitation in a model of severe injury and was associated with increased acidosis, hemodilution, and liver injury compared with standard crystalloid resuscitation.

Physiology and cardiovascular effect of severe tension pneumothorax in a porcine model.

BACKGROUND: Pneumothoraces are relatively common among trauma patients and can rapidly progress to tension physiology and death if not identified and treated. We sought to develop a reliable and reproducible large animal model of tension pneumothorax and to examine the cardiovascular effects during progression from simple pneumothorax to tension pneumothorax. MATERIALS AND METHODS: Ten swine were intubated, sedated, and placed on mechanical ventilation. After a midline celiotomy, a 10-mm balloon-tipped laparoscopic trocar was placed through the diaphragm, and a 28F chest tube was placed in the standard position and clamped. Thoracic insufflation was performed in 5-mm increments, and continuous cardiovascular measurements were obtained. RESULTS: Mean insufflation pressures of 10 mm Hg were associated with a 67% decrease in cardiac output (6.6 L/min versus 2.2 l/min; P = 0.04). An additional increase in the insufflation pressure (mean 15 mm Hg) was associated with an 82% decrease in cardiac output from baseline (6.8 versus 1.2 L/min; P < 0.01). Increasing insufflation pressures were associated with a corresponding increase in central venous pressure (from 7.6 mm Hg to 15.2 mm Hg; P < 0.01) and a simultaneous decrease in the pulmonary artery diastolic pressure (from 15 mm Hg to 12 mm Hg; P = 0.06), with the central venous pressure and pulmonary artery diastolic pressure approaching equalization immediately before the development of major hemodynamic decline. Pulseless electrical activity arrest was induced at an average of 20 mm Hg. Tension physiology was immediately reversible with adequate decompression, allowing for multiple repeated trials. CONCLUSIONS: A reliable and highly reproducible model was created for severe tension pneumothorax in a large animal. Major cardiovascular instability proceeding to pulseless electrical activity arrest with stepwise insufflation was noted. This model could be highly useful for studying new diagnostic and treatment modalities for tension pneumothorax.

Hemostasis in a noncompressible hemorrhage model: an end-user evaluation of hemostatic agents in a proximal arterial injury.

OBJECTIVE: 1. Evaluate hemostatic bandages by the end user using subjective and objective criteria. 2. Determine if user training and education level impact overall hemostatic outcomes. 3. Our hypothesis was that prior medical training would be directly linked to improved hemostatic outcomes in noncompressible hemorrhage indepen- dent of dressing used. DESIGN: Military personnel were given standardized instruction on hemostatic dressings as part of a tactical combat casualty care course (TC3). Soldiers were randomized to a hemostatic dressing. Proximal arterial (femoral and axillary) injuries were created in extremities of live tissue models (goat or pig). Participants attempted hemostasis through standardized dressing application. Evaluation of hemostasis was performed at 2- and 4-minute intervals by physicians blinded to participants' training level. SETTING: Military personnel that are due to deploy are given "refresher" instruction by their units as well as participating in the TC3 to further hone their medical skills prior to deployment. The TC3 is simulation training designed to simulate combat environments and real-life trauma scenarios. PARTICIPANTS: Military personnel due to deploy, physicians (residents and board certified surgeons), animal care technicians, and veterinarian support. RESULTS: Celox 42 (33%), ChitoGauze 11 (9%), Combat Gauze 45 (35%), and HemCon wafer 28 (22%) bandages were applied in 126 arterial injuries created in 45 animals in a standardized model of hemorrhage. Overall, no significant difference in hemostasis and volume of blood loss was seen between the 4 dressings at 2 or 4 minutes. Combat gauze was the most effective at controlling hemorrhage, achieving 83% hemostasis by 4 minutes. Combat gauze was also rated as the easiest dressing to use by the soldiers (p<0.05). When compared to nonmedical personnel, active duty soldiers with prior medical training improved hemostasis at 4 minutes by 20% (p = 0.05). CONCLUSIONS: There is no significant difference in hemostasis between hemostatic bandages for proximal arterial hemorrhage. Hemostasis significantly improves between 2 and 4 minutes using direct pressure and hemostatic agents. Prior medical training leads to 20% greater efficacy when using hemostatic dressings.

Does needle thoracostomy provide adequate and effective decompression of tension pneumothorax?

BACKGROUND: Tension pneumothorax (tPTX) is a common and potentially fatal event after thoracic trauma. Needle decompression is the currently accepted first-line intervention but has not been well validated. The purpose of this study was to evaluate the effectiveness of a properly placed and patent needle thoracostomy (NT) compared with standard tube thoracostomy (TT) in a swine model of tPTX. METHODS: Six adult swine underwent instrumentation and creation of tPTX using thoracic CO2 insufflation via a balloon trocar. A continued 1 L/min insufflation was maintained to simulate an ongoing air leak. The efficacy and failure rate of NT (14 gauge) compared with TT (34F) was assessed in two separate arms: (1) tPTX with hemodynamic compromise and (2) tPTX until pulseless electrical activity (PEA) obtained. Hemodynamics was assessed at 1 and 5 minutes after each intervention. RESULTS: A reliable and highly reproducible tPTX was created in all animals with a mean insufflation volume of 2441 mL. tPTX resulted in the systolic blood pressure declining 54% from baseline (128-58 mm Hg), cardiac output declining by 77% (7-1.6 L/min), and equalization of central venous pressure and wedge pressures. In the first arm, there were 19 tPTX events treated with NT placement. All NTs were patent on initial placement, but 5 (26%) demonstrated mechanical failure (due to kinking, obstruction, or dislodgment) within 5 minutes of placement, all associated with hemodynamic decline. Among the 14 NTs that remained patent at 5 minutes, 6 (43%) failed to relieve tension physiology for an overall failure rate of 58%. Decompression with TT was successful in relieving tPTX in 100%. In the second arm, there were 21 tPTX with PEA events treated initially with either NT (n = 14) or TT (n = 7). The NT failed to restore perfusion in nine events (64%), whereas TT was successful in 100% of events as a primary intervention and restored perfusion as a rescue intervention in eight of the nine NT failures (88%). CONCLUSION: Thoracic insufflation produced a reliable and easily controlled model of tPTX. NT was associated with high failure rates for relief of tension physiology and for treatment of tPTX-induced PEA and was due to both mechanical failure and inadequate tPTX evacuation. This performance data should be considered in future NT guideline development and equipment design.