Extracorporeal organ support following trauma: the dawn of a new era in combat casualty critical care

Hemofiltration system for the post traumatic treatment of hyperkalemia in austere conditions

BACKGROUND

Hyperkalemia, the buildup of serum potassium to levels >6 mEq L-1, has been a recognized complication of combat injuries such as acute kidney injury since World War II. Currently, renal replacement therapy (RRT) serves as the standard of care for hyperkalemic patients who fail to respond to medical management. However, RRT is difficult to administer in combat settings, and the time between evacuation and RRT is critical in preventing post-traumatic hyperkalemia. Therefore, the need for portable, easily operable hemofiltration technology is pressing to improve the survival of hyperkalemic patients in austere settings.

METHODS

In this manuscript, we present extra-corporeal direct contact and hemodialysis filtration systems for treating severe hyperkalemia and tested the efficacy, biocompatibility, and performance of a zeolite-based renal RRT. We tested the uptake capacity of an adsorbent zeolite optimized for the selective binding and removal of potassium in various mediums, including dialysate, bovine serum, and whole bovine sodium heparinized blood.

RESULTS AND CONCLUSIONS

Our results show that we can restore physiological normokalemic levels within just 2 h of testing and maintain these levels for 6 h. Furthermore, calcium and sodium levels were maintained within normal physiological ranges, confirming the selectivity of our sorbent material for potassium binding.

Indications and Outcomes for Adult Extracorporeal Membrane Oxygenation at a Military Referral Facility

INTRODUCTION

Extracorporeal life support, including extracorporeal membrane oxygenation (ECMO), is a potentially life-saving adjunct to therapy in patients experiencing pulmonary and/or cardiac failure. The U.S. DoD has only one ECMO center, in San Antonio, Texas. In this study, we aimed to analyze outcomes at this center in order to determine whether they are on par with those reported elsewhere in the literature.

MATERIALS AND METHODS

In this observational study, we analyzed data from patients treated with ECMO at the only DoD ECMO center between September 2012 and April 2020. The primary outcome was survival to discharge, and secondary outcomes were discharge disposition and incidence of complications.

RESULTS

One hundred and forty-three patients were studied, with a 70.6% rate of survival to discharge. Of the patients who survived, 32.7% were discharged home; 32.7% were discharged to a rehabilitation facility; and 33.7% were transferred to another hospital, 29.4% of whom were transferred to lung transplant centers. One patient left against medical advice. Incidence of ECMO-related complications were as follows: 64 patients (44.7%) experienced hemorrhagic complications, 80 (55.9%) had renal complications, 61 (42.6%) experienced cardiac complications, 39 (27.3%) had pulmonary complications, and 5 patients (3.5%) experienced limb ischemia. We found that these outcomes were comparable to those reported in the literature.

CONCLUSIONS

Extracorporeal membrane oxygenation can be an efficacious adjunct in management of critically ill patients who require pulmonary and/or cardiac support. This single-center observational study demonstrated that the DoD's only ECMO center has outcomes comparable with the reported data in Extracorporeal Life Support Organization's registry.

Multilayer Scaling of a Biomimetic Microfluidic Oxygenator

Extracorporeal membrane oxygenation (ECMO) has been advancing rapidly due to a combination of rising rates of acute and chronic lung diseases as well as significant improvements in the safety and efficacy of this therapeutic modality. However, the complexity of the ECMO blood circuit, and challenges with regard to clotting and bleeding, remain as barriers to further expansion of the technology. Recent advances in microfluidic fabrication techniques, devices, and systems present an opportunity to develop new solutions stemming from the ability to precisely maintain critical dimensions such as gas transfer membrane thickness and blood channel geometries, and to control levels of fluid shear within narrow ranges throughout the cartridge. Here, we present a physiologically inspired multilayer microfluidic oxygenator device that mimics physiologic blood flow patterns not only within individual layers but throughout a stacked device. Multiple layers of this microchannel device are integrated with a three-dimensional physiologically inspired distribution manifold that ensures smooth flow throughout the entire stacked device, including the critical entry and exit regions. We then demonstrate blood flows up to 200 ml/min in a multilayer device, with oxygen transfer rates capable of saturating venous blood, the highest of any microfluidic oxygenator, and a maximum blood flow rate of 480 ml/min in an eight-layer device, higher than any yet reported in a microfluidic device. Hemocompatibility and large animal studies utilizing these prototype devices are planned. Supplemental Visual Abstract, http://links.lww.com/ASAIO/A769.

Evolution of the United States Military Extracorporeal Membrane Oxygenation Transport Team

INTRODUCTION

The use of extracorporeal membrane oxygenation (ECMO) for the care of critically ill adult patients has increased over the past decade. It has been utilized in more austere locations, to include combat wounded. The U.S. military established the Acute Lung Rescue Team in 2005 to transport and care for patients unable to be managed by standard medical evacuation resources. In 2012, the U.S. military expanded upon this capacity, establishing an ECMO program at Brooke Army Medical Center. To maintain currency, the program treats both military and civilian patients.

MATERIALS AND METHODS

We conducted a single-center retrospective review of all patients transported by the sole U.S. military ECMO program from September 2012 to December 2019. We analyzed basic demographic data, ECMO indication, transport distance range, survival to decannulation and discharge, and programmatic growth.

RESULTS

The U.S. military ECMO team conducted 110 ECMO transports. Of these, 88 patients (80%) were transported to our facility and 81 (73.6%) were cannulated for ECMO by our team prior to transport. The primary indication for ECMO was respiratory failure (76%). The range of transport distance was 6.5 to 8,451 miles (median air transport distance = 1,328 miles, median ground transport distance = 16 miles). In patients who were cannulated remotely, survival to decannulation was 76% and survival to discharge was 73.3%.

CONCLUSIONS

Utilization of the U.S. military ECMO team has increased exponentially since January 2017. With an increased tempo of transport operations and distance of critical care transport, survival to decannulation and discharge rates exceed national benchmarks as described in ELSO published data. The ability to cannulate patients in remote locations and provide critical care transport to a military medical treatment facility has allowed the U.S. military to maintain readiness of a critical medical asset.

A Novel Perfusion System for Damage Control of Hyperkalemia in Swine

INTRODUCTION

The standard of care for refractory hyperkalemia is renal replacement therapy (RRT). However, traditional RRT requires specialized equipment, trained personnel, and large amounts of dialysate. It is therefore poorly suited for austere environments. We hypothesized that a simplified hemoperfusion system could control serum potassium concentration in a swine model of acute hyperkalemia.

METHODS

Ten pigs were anesthetized and instrumented. A dialysis catheter was inserted. After bilateral nephrectomy, animals received intravenous potassium chloride and were randomized to the control or treatment group. In both groups, blood was pumped through an extracorporeal circuit (EC) with an in-line hemodialyzer. In the treatment arm, ultrafiltrate from the hemodialyzer was diverted through cartridges containing novel potassium binding beads and returned to the EC. Blood samples were obtained every 30 min for 6 h.

RESULTS

Serum potassium concentration was significantly lower in the treatment than in the control group over time (P = 0.02). There was no difference in serum total calcium concentration for group or time (P = 0.13 and 0.44, respectively) or platelet count between groups or over time (P = 0.28 and 1, respectively). No significant EC thrombosis occurred. Two of five animals in the control group and none in the treatment group developed arrhythmias. All animals survived until end of experiment.

CONCLUSIONS

A simplified hemoperfusion system removed potassium in a porcine model. In austere settings, this system could be used to temporize patients with hyperkalemia until evacuation to a facility with traditional RRT.

Extracorporeal Filtration of Potassium in a Swine Model of Bilateral Hindlimb Ischemia-Reperfusion Injury With Severe Acute Hyperkalemia

Introduction

Options for the treatment of hyperkalemia in the pre-hospital setting are limited, particularly in the context of natural disaster or during combat operations. Contemporary interventions require extensive resources and technical expertise. Here we examined the potential for a simple, field deployable bridge-dialysis as a countermeasure for acute hyperkalemia induced by prolonged ischemia-reperfusion.

Methods

Twenty female swine were randomized into two experimental groups undergoing a 2-hour bilateral hindlimb ischemia-reperfusion injury. Subsequent to injury, hemoperfusion was performed in the presence (Column) and absence (Sham Control) of a high-affinity potassium-binding column (CytoSorbents, Monmouth Junction, NJ, USA). Serial blood gas and chemistries were sampled. Primary endpoint was changed in serum potassium concentrations post-injury and filtration.

Results

Serum potassium was significantly elevated following ischemia-reperfusion injury in both groups (149% (12) and 150% (22), p < 0.05 vs respective baseline values). There were no differences observed between groups in respect to physiologic parameters; mean arterial pressure, heart rate, systemic vascular resistance, cardiac output, or central venous oxygenation. Filtration resulted in a significant relative decrease in potassium compared with controls after the first hour as determined by repeated measures two-way ANOVA (p < 0.0001) which continued through end of the study. Significant thrombocytopenia was observed in animals undergoing filtration with a mean reduction in platelets measured at T = 480 minutes (168 × 103μL, p < 0.0001 vs baseline).

Conclusions

We demonstrate that serum potassium can be filtered via hemoperfusion utilizing a simple extracorporeal potassium-binding platform, though evolution of this technology will be required to achieve meaningful reduction of potassium in clinically significant hyperkalemia after trauma.

AAST Critical Care Committee clinical consensus: ECMO, nutrition

The American Association for the Surgery of Trauma Critical Care Committee has developed clinical consensus guides to help with practical answers based on the best evidence available. These are focused in areas in which the levels of evidence may not be that strong and are based on a combination of expert consensus and research. Overall, quality of the research is mixed, with many studies suffering from small numbers and issues with bias. The first two of these focus on the use of extracorporeal membrane oxygenation in trauma patients and nutrition for the critically ill surgical/trauma patient.

Electron Microscopy as a Tool for Assessment of Anticoagulation Strategies During Extracorporeal Life Support: The Proof Is on the Membrane

Extracorporeal life support (ECLS) is fast becoming more common place for use in adult patients failing mechanical ventilation. Management of coagulation and thrombosis has long been a major complication in the use of ECLS therapies. Scanning electron microscopy (SEM) of membrane oxygenators (MOs) after use in ECLS circuits can offer novel insight into any thrombotic material deposition on the MO. In this pilot study, we analyzed five explanted MOs immediately after use in a sheep model of different acute respiratory distress syndrome (ARDS). We describe our methods of MO dissection, sample preparation, image capture, and results. Of the five MOs analyzed, those that received continuous heparin infusion showed very little thrombosis formation or other clot material, whereas those that were used with only initial heparin bolus showed readily apparent thrombotic material.

Incidence, risk factors, and mortality associated with acute respiratory distress syndrome in combat casualty care

BACKGROUND

The overall incidence and mortality of acute respiratory distress syndrome (ARDS) in civilian trauma settings have decreased over the past four decades; however, the epidemiology and impact of ARDS on modern combat casualty care are unknown. We sought to determine the incidence, risk factors, resource utilization, and mortality associated with ARDS in current combat casualty care.

METHODS

This was a retrospective review of mechanically ventilated US combat casualties within the Department of Defense Trauma Registry (formerly the Joint Theater Trauma Registry) during Operation Iraqi Freedom/Enduring Freedom (October 2001 to August 2008) for ARDS development, resource utilization, and mortality.

RESULTS

Of 18,329 US Department of Defense Trauma Registry encounters, 4,679 (25.5%) required mechanical ventilation; ARDS was identified in 156 encounters (3.3%). On multivariate logistic regression, ARDS was independently associated with female sex (odds ratio [OR], 2.62; 95% confidence interval [CI], 1.21-5.71; p = 0.02), higher military-specific Injury Severity Score (Mil ISS) (OR, 4.18; 95% CI, 2.61-6.71; p < 0.001 for Mil ISS ≥25 vs. <15), hypotension (admission systolic blood pressure <90 vs. ≥90 mm Hg; OR, 1.76; 95% CI, 1.07-2.88; p = 0.03), and tachycardia (admission heart rate ≥90 vs. <90 beats per minute; OR, 1.53; 95% CI, 1.06-2.22; p = 0.02). Explosion injury was not associated with increased risk of ARDS. Critical care resource utilization was significantly higher in ARDS patients as was all-cause hospital mortality (ARDS vs. no ARDS, 12.8% vs. 5.9%; p = 0.002). After adjustment for age, sex, injury severity, injury mechanism, Mil ISS, hypotension, tachycardia, and admission Glasgow Coma Scale score, ARDS remained an independent risk factor for death (OR, 1.99; 95% CI, 1.12-3.52; p = 0.02).

CONCLUSIONS

In this large cohort of modern combat casualties, ARDS risk factors included female sex, higher injury severity, hypotension, and tachycardia, but not explosion injury. Patients with ARDS also required more medical resources and were at greater risk of death compared with patients without ARDS. Thus, ARDS remains a significant complication in current combat casualty care.

LEVEL OF EVIDENCE

Prognostic/epidemiologic study, level III.

The potential utility of urinary biomarkers for risk prediction in combat casualties: a prospective observational cohort study

Introduction

Traditional risk scoring prediction models for trauma use either anatomically based estimations of injury or presenting vital signs. Markers of organ dysfunction may provide additional prognostic capability to these models. The objective of this study was to evaluate if urinary biomarkers are associated with poor outcomes, including death and the need for renal replacement therapy.

Methods

We conducted a prospective, observational study in United States Military personnel with traumatic injury admitted to the intensive care unit at a combat support hospital in Afghanistan.

Results

Eighty nine patients with urine samples drawn at admission to the intensive care unit were studied. Twelve patients subsequently died or needed renal replacement therapy. Median admission levels of urinary cystatin C (CyC), interleukin 18 (IL-18), L-type fatty acid binding protein (LFABP) and neutrophil gelatinase-associated lipocalin (NGAL) were significantly higher in patients that developed the combined outcome of death or need for renal replacement therapy. Median admission levels of kidney injury molecule-1 were not associated with the combined outcome. The area under the receiver operating characteristic curves for the combined outcome were 0.815, 0.682, 0.842 and 0.820 for CyC, IL-18, LFABP and NGAL, respectively. Multivariable regression adjusted for injury severity score, revealed CyC (OR 1.97, 95 % confidence interval 1.26-3.10, p = 0.003), LFABP (OR 1.92, 95 % confidence interval 1.24-2.99, p = 0.004) and NGAL (OR 1.80, 95 % confidence interval 1.21-2.66, p = 0.004) to be significantly associated with the composite outcome.

Conclusions

Urinary biomarker levels at the time of admission are associated with death or need for renal replacement therapy. Larger multicenter studies will be required to determine how urinary biomarkers can best be used in future prediction models.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0965-y) contains supplementary material, which is available to authorized users.

An extracorporeal blood-cleansing device for sepsis therapy

Here we describe a blood-cleansing device for sepsis therapy inspired by the spleen, which can continuously remove pathogens and toxins from blood without first identifying the infectious agent. Blood flowing from an infected individual is mixed with magnetic nanobeads coated with an engineered human opsonin--mannose-binding lectin (MBL)--that captures a broad range of pathogens and toxins without activating complement factors or coagulation. Magnets pull the opsonin-bound pathogens and toxins from the blood; the cleansed blood is then returned back to the individual. The biospleen efficiently removes multiple Gram-negative and Gram-positive bacteria, fungi and endotoxins from whole human blood flowing through a single biospleen unit at up to 1.25 liters per h in vitro. In rats infected with Staphylococcus aureus or Escherichia coli, the biospleen cleared >90% of bacteria from blood, reduced pathogen and immune cell infiltration in multiple organs and decreased inflammatory cytokine levels. In a model of endotoxemic shock, the biospleen increased survival rates after a 5-h treatment.