Extraterrestrial hemorrhage control: Terrestrial developments in technique, technology, and philosophy with applicability to traumatic hemorrhage control in long-duration spaceflight

Managing Hemostasis in Space

Human space travel requires exposure to weightlessness, ionizing radiation, isolation, and austerity. A recent report of internal jugular vein thrombosis in astronauts in low Earth orbit confirms that these exposures also affect vascular biology to influence diseases of thrombosis and hemostasis. This brief review summarizes the known influences of space travel on inflammation, blood coagulation, and the cardiovascular system and conceptualizes how they might combine to affect thrombosis and hemostasis. In the event of a major thrombotic or bleeding emergency, it is anticipated that the unique physiological influences of the space environment and logistical limitations of providing medical care in space would require a response that is unique from our current experience. We also look towards the future to discuss lessons learned from our current experiences on Earth and in space.

Intravenous Fluid Resuscitation Capabilities in Simulated Reduced Gravity

BACKGROUND: Critical care for exploration space missions may require intravenous (IV) fluid resuscitation therapy. Resource constraints may limit availability of standard, Earth-based infusion technologies. The effect of variable acceleration on infusion flow rates using simple fluid resuscitation supplies was investigated.METHODS: Infusions of water or blood analog (40% glycerol) from a 1 L IV bag were performed using pressure bag augmentation at 0, 150, or 300 mmHg. The solution bag rested on an adjustable mount, configured to different heights to simulate relevant gravitational accelerations (1 G, Martian G, lunar G, and 0 G). The bag emptied through an IV line with a 14- or 20-gauge angiocath into a 3-mmHg venous pressure reservoir. Flow rates were measured using an in-line flow probe. Three determinations were made for each test condition.RESULTS: Temporal flow rate data for all test conditions displayed one-phase exponential decay. At 300 mmHg pressurization, maximum infusion rates ranged from 92-222 mL ⋅ min-1 for water and from 21-49 mL ⋅ min-1 for blood analog. All reduced gravity conditions had significantly longer infusion times in comparison to 1 G for both test solutions.DISCUSSION: Reduced acceleration significantly altered flow rates and infusion times for fluid resuscitation. Fluid resuscitation protocols specify a desired volume to infuse for a target time (e.g., 20-30 mL ⋅ min-1 for a 75-kg adult). This data demonstrates that this protocol parameter can be achieved with infusion pressure bag augmentation alone and provides information for the refinement of fluid resuscitation protocols for exploration space missions.Pantalos GM, Heidel JS, Jain IM, Warner SE, Barefoot TL, Baker RO, Hailey M. Intravenous fluid resuscitation capabilities in simulated reduced gravity. Aerosp Med Hum Perform. 2023; 94(8):596-603.

External Hemorrhage Control Techniques for Human Space Exploration: Lessons from the Battlefield

The past few decades of military experience have brought major advances in the prehospital care of patients with trauma. A focus on early hemorrhage control with aggressive use of tourniquets and hemostatic gauze is now generally accepted. This narrative literature review aims to discuss external hemorrhage control and the applicability of military concepts in space exploration. In space, environmental hazards, spacesuit removal, and limited crew training could cause significant time delays in providing initial trauma care. Cardiovascular and hematological adaptations to the microgravity environment are likely to reduce the ability to compensate, and resources for advanced resuscitation are limited. Any unscheduled emergency evacuation requires a patient to don a spacesuit, involves exposure to high G-forces upon re-entry into Earth's atmosphere, and costs a significant amount of time until a definitive care facility is reached. As a result, early hemorrhage control in space is critical. Safe implementation of hemostatic dressings and tourniquets seems feasible, but adequate training will be essential, and tourniquets are preferably converted to other methods of hemostasis in case of a prolonged medical evacuation. Other emerging approaches such as early tranexamic acid administration and more advanced techniques have shown promising results as well. For future exploration missions to the Moon and Mars, when evacuation is not possible, we look into what training or assistance tools would be helpful in managing the bleed at the point of injury.

Human Health during Space Travel: State-of-the-Art Review

The field of human space travel is in the midst of a dramatic revolution. Upcoming missions are looking to push the boundaries of space travel, with plans to travel for longer distances and durations than ever before. Both the National Aeronautics and Space Administration (NASA) and several commercial space companies (e.g., Blue Origin, SpaceX, Virgin Galactic) have already started the process of preparing for long-distance, long-duration space exploration and currently plan to explore inner solar planets (e.g., Mars) by the 2030s. With the emergence of space tourism, space travel has materialized as a potential new, exciting frontier of business, hospitality, medicine, and technology in the coming years. However, current evidence regarding human health in space is very limited, particularly pertaining to short-term and long-term space travel. This review synthesizes developments across the continuum of space health including prior studies and unpublished data from NASA related to each individual organ system, and medical screening prior to space travel. We categorized the extraterrestrial environment into exogenous (e.g., space radiation and microgravity) and endogenous processes (e.g., alteration of humans' natural circadian rhythm and mental health due to confinement, isolation, immobilization, and lack of social interaction) and their various effects on human health. The aim of this review is to explore the potential health challenges associated with space travel and how they may be overcome in order to enable new paradigms for space health, as well as the use of emerging Artificial Intelligence based (AI) technology to propel future space health research.

Facing Trauma and Surgical Emergency in Space: Hemorrhagic Shock

Although the risk of trauma in space is low, unpredictable events can occur that may require surgical treatment. Hemorrhage can be a life-threatening condition while traveling to another planet and after landing on it. These exploration missions call for a different approach than rapid return to Earth, which is the policy currently adopted on the International Space Station (ISS) in low Earth orbit (LEO). Consequences are difficult to predict, given the still scarce knowledge of human physiology in such environments. Blood loss in space can deplete the affected astronaut’s physiological reserves and all stored crew supplies. In this review, we will describe different aspects of hemorrhage in space, and by comparison with terrestrial conditions, the possible solutions to be adopted, and the current state of the art.

Do we have the guts to go? The abdominal compartment, intra-abdominal hypertension, the human microbiome and exploration class space missions

Humans are destined to explore space, yet critical illness and injury may be catastrophically limiting for extraterrestrial travel. Humans are superorganisms living in symbiosis with their microbiomes, whose genetic diversity dwarfs that of humans. Symbiosis is critical and imbalances are associated with disease, occurring within hours of serious illness and injury. There are many characteristics of space flight that negatively influence the microbiome, especially deep space itself, with its increased radiation and absence of gravity. Prolonged weightlessness causes many physiologic changes that are detrimental; some resemble aging and will adversely affect the ability to tolerate critical illness or injury and subsequent treatment. Critical illness-induced intra-abdominal hypertension (IAH) may induce malperfusion of both the viscera and microbiome, with potentially catastrophic effects. Evidence from animal models confirms profound IAH effects on the gut, namely ischemia and disruption of barrier function, mechanistically linking IAH to resultant organ dysfunction. Therefore, a pathologic dysbiome, space-induced immune dysfunction and a diminished cardiorespiratory reserve with exacerbated susceptibility to IAH, imply that a space-deconditioned astronaut will be vulnerable to IAH-induced gut malperfusion. This sets the stage for severe gut ischemia and massive biomediator generation in an astronaut with reduced cardiorespiratory/immunological capacity. Fortunately, experiments in weightless analogue environments suggest that IAH may be ameliorated by conformational abdominal wall changes and a resetting of thoracoabdominal mechanics. Thus, review of the interactions of physiologic changes with prolonged weightlessness and IAH is required to identify appropriate questions for planning exploration class space surgical care.

Point-of-care resuscitation research: From extreme to mainstream: Trauma Association of Canada Fraser Gurd Lecture 2019

The Gurd Family surgical legacy was deeply intertwined with National service in both World Wars. My own personal research mission has attempted to emulate such service, by enhancing the tools and techniques available to facilitate point-of-care diagnosis and resuscitation in extreme and adverse environments. Our efforts involving point-of-care diagnosis/resuscitation and the telementored guidance of those remotely responding to catastrophic injury have included collaborations with National Aeronautics and Space Administration (NASA) the Canadian Space Agency, the Canadian Forces, its democratic allies, and non-governmental surgical organizations. Research has been conducted in resuscitative suites and operating theaters, research laboratories, parabolic flight aircraft, on humanitarian surgical missions, and from ski-hills and firehalls. The initial phases of these efforts involved inaugural studies in resuscitative sonography including defining the Extended Focused Assessment with Sonography for Trauma (EFAST) examination. Although the original work was commissioned for Space Medicine, generalization to mainstream practice further justifies space medicine research. Iterative steps in advancing telementored resuscitation have subsequently involved the maturation of space-mandated telementored ultrasound support (TMUS), exploration of TMUS in terrestrial clinical practice, and the creation of increasingly mobile (hand-held) TMUS solutions. Subsequently it was recognized that teleultrasound is simply one informatic dimension of remote telemedicine, and current efforts are focused in a Program known as TeleMentored Ultrasound Supported Medical Interactions (TMUSMI) of remote responders required to intervene with catastrophic trauma. While this research program has yielded many techniques and findings that have benefited mainstream terrestrial practice, these investigations are currently ongoing, and we hope to demonstrate that TMUSMI may benefit all Canadians especially those in remote areas, as well as potentially every global inhabitant without immediate access to care. Further, we propose that to fully utilize these techniques, a new specialty, that of the remote medical mentor will be required, a new specialty that will require the creation and scientific validation of its principles and techniques.

Surgery in space

Background

There has been renewed public interest in manned space exploration owing to novel initiatives by private and governmental bodies. Long-term goals include manned missions to, and potential colonization of, nearby planets. Travel distances and mission length required for these would render Earth-based treatment and telemedical solutions unfeasible. These issues present an anticipatory challenge to planners, and novel or adaptive medical technologies must therefore be devised to diagnose and treat the range of medical issues that future space travellers will encounter.

Methods

The aim was to conduct a search of the literature pertaining to human physiology, pathology, trauma and surgery in space.

Results

Known physiological alterations include fluid redistribution, cardiovascular changes, bone and muscle atrophy, and effects of ionizing radiation. Potential pathological mechanisms identified include trauma, cancer and common surgical conditions, such as appendicitis.

Conclusion

Potential surgical treatment modalities must consist of self-sufficient and adaptive technology, especially in the face of uncertain pathophysiological mechanisms and logistical concerns.

Damage control surgery in weightlessness: A comparative study of simulated torso hemorrhage control comparing terrestrial and weightless conditions

BACKGROUND

Torso bleeding remains the most preventable cause of post-traumatic death worldwide. Remote damage control resuscitation (RDCR) endeavours to rescue the most catastrophically injured, but has not focused on prehospital surgical torso hemorrhage control (HC). We examined the logistics and metrics of intraperitoneal packing in weightlessness in Parabolic flight (0g) compared to terrestrial gravity (1g) as an extreme example of surgical RDCR.

METHODS

A surgical simulator was customized with high-fidelity intraperitoneal anatomy, a "blood" pump and flowmeter. A standardized HC task was to explore the simulator, identify "bleeding" from a previously unknown liver injury perfused at 80 mm Hg, and pack to gain hemostasis. Ten surgeons performed RDCR laparotomies onboard a research aircraft, first in 1g followed by 0g. The standardized laparotomy was sectioned into 20-second segments to conduct and facilitate parabolic flight comparisons, with "blood" pumped only during these time segments. A maximum of 12 segments permitted for each laparotomy.

RESULTS

All 10 surgeons successfully performed HC in both 1g and 0g. There was no difference in blood loss between 1g and 0g (p = 0.161) or during observation following HC (p = 0.944). Compared to 1g, identification of bleeding in 0g incurred less "blood" loss (p = 0.032). Overall surgeons rated their personal performance and relative difficulty of surgery in 0g as "harder" (median Likert, 2/5). However, conducting all phases of HC were rated equivalent between 1g and 0g (median Likert, 3/5), except for instrument control (rated slightly harder, 2.75/5).

CONCLUSION

Performing laparotomies with packing of a simulated torso hemorrhage in a high-fidelity surgical simulator was feasible onboard a research aircraft in both normal and weightless conditions. Despite being subjectively "harder," most phases of operative intervention were rated equivalently, with no statistical difference in "blood" loss in weightlessness. Direct operative control of torso hemorrhage is theoretically possible in extreme environments if logistics are provided.

Noninvasive pulse transit time measurement for arterial stiffness monitoring in microgravity

The use of a noninvasive hemodynamic monitor to estimate arterial stiffness, by measurement of pulse transit time (PTT), was demonstrated in microgravity. The monitor's utility for space applications was shown by establishing the correlation between ground-based and microgravity-based measurements. The system consists of a scale-based ballistocardiogram (BCG) and a toe-mounted photoplethysmogram (PPG). PTT was measured from the BCG I-wave to the intersecting tangents of the first trough and maximum first derivative of the PPG waveforms of each subject. The system was tested on a recent series of parabolic flights in which the PTT of nine subjects was measured on the ground and in microgravity. An average of 60.2 ms PTT increase from ground to microgravity environments was shown, and was consistent across all test subjects (standard deviation = 32.9 ms). This increase in PTT could be explained by a number of factors associated with microgravity and reported in previous research, including elimination of hydrostatic pressure, reduction of intrathoracic pressure, and reduction of mean arterial pressure induced by vasodilation.

Standing ballistocardiography measurements in microgravity

The performance and practicality of a scale-based ballistocardiogram (BCG) system for hemodynamic monitoring of astronauts on extended space missions was demonstrated. The system consists of a modified electronic weighing scale fitted with foot bindings to mechanically couple the subject to the scale. This system was tested on a recent series of parabolic flights in which scale-based and accelerometry-based free-floating BCG of 10 subjects was measured in microgravity. The signal-to-noise ratio (SNR) of the scale-based BCG was, on average, a factor of 2.1 (6.3 dB) higher than the free-floating method, suggesting that the tethered scale approach might be more robust in terms of signal quality. Additionally, this approach enables practical BCG-based hemodynamic monitoring in fractional-g environments, and on small space vehicles such as NASA's upcoming Orion capsule. The scale-based results in microgravity were also compared to ground measurements (1 g), where there was an average 38.7 ms RJ interval reduction from ground to microgravity environments that is consistent across 9 of 10 subjects. This phenomenon is likely due to the transient increase in venous return, and consequent decrease in pre-ejection period, experienced during the microgravity time intervals.

The marriage of surgical simulation and telementoring for damage-control surgical training of operational first responders: A pilot study

BACKGROUND

Hemorrhage is the leading cause of preventable posttraumatic death. Many such deaths may be potentially salvageable with remote damage-control surgical interventions. As recent innovations in information technology enable remote specialist support to point-of-care providers, advanced interventions, such as remote damage-control surgery, may be possible in remote settings.

METHODS

An anatomically realistic perfused surgical training mannequin with intrinsic fluid loss measurements (the "Cut Suit") was used to study perihepatic packing with massive liver hemorrhage. The primary outcome was loss of simulated blood (water) during six stages, namely, incision, retraction, direction, identification, packing, and postpacking. Six fully credentialed surgeons performed the same task as 12 military medical technicians who were randomized to remotely telementored (RTM) (n = 7) or unmentored (UTM) (n=5) real-time guidance by a trauma surgeon.

RESULTS

There were no significant differences in fluid loss between the surgeons and the UTM group or between the UTM and RTM groups. However, when comparing the RTM group with the surgeons, there was significantly more total fluid loss (p = 0.001) and greater loss during the identification (p = 0.002), retraction (p = 0.035), direction (p = 0.014), and packing(p = 0.022) stages. There were no significant differences in fluid loss after packing between the groups despite differences in the number of sponges used; RTM group used more sponges than the surgeons and significantly more than the UTM group (p = 0.048). However, mentoring significantly increased self-assessed nonsurgeon procedural confidence (p = 0.004).

CONCLUSION

Perihepatic packing of an exsanguinating liver hemorrhage model was readily performed by military medical technicians after a focused briefing. While real-time telementoring did not improve fluid loss, it significantly increased nonsurgeon procedural confidence, which may augment the feasibility of the concept by allowing them to undertake psychologically daunting procedures.

Preliminary results from standing ballistocardiography measurements in microgravity

We report on the feasibility of standing ballistocardiogram (BCG) measurements recorded in a microgravity environment. A clinically-tested BCG monitoring scale was adapted for parabolic flight for the microgravity measurements. Upon completion of this flight campaign, the BCG scale was shown to make measurements in micro-g and one-g environments--which is a first demonstration for a standing BCG system. This screening experiment demonstrated proof-of-concept attributes of the hardware design necessary for future characterization studies with multiple subjects. This scale-based BCG system is proposed as a practical device for hemodynamic monitoring for astronauts in Earth, Lunar, Martian, orbital, and interplanetary environments.

Prophylactic surgery prior to extended-duration space flight: is the benefit worth the risk?

This article explores the potential benefits and defined risks associated with prophylactic surgical procedures for astronauts before extended-duration space flight. This includes, but is not limited to, appendectomy and cholecystesctomy. Furthermore, discussion of treatment during space flight, potential impact of an acute illness on a defined mission and the ethical issues surrounding this concept are debated in detail.

2010 Trauma Association of Canada presidential address: why the Trauma Association of Canada should care about space medicine

The Trauma Association of Canada is now 27 years old, having been officially founded in 1983, at the meetings of the Royal College as a maturation of the trauma committee of the Canadian Association of General Surgeons. The first page of the official minutes also stressed the need to welcome other disciplines into the fold. Personally, it has taken me years of involvement, as well as the Presidency, to truly appreciate the depth of our Founding Members commitment. These individuals set lofty mission goals for the organization, namely: to strive to improve the quality of care provided to the injured patient, including prehospital management and transport, acute care hospitalization, and reintegration into society; to support, conduct, and apply basic science and clinical and outcome research related to trauma; to encourage effective and efficient use of healthcare resources in the delivery of trauma care; and to foster professional and community education in the field of injury prevention and in the care of the injured patient. As daunting as these responsibilities are, I am suggesting one more: to overcome the great penalty of geography that challenges our nation and penalizes many of our citizens by aspiring to optimize these four goals, for all Canadians, irrespective of where they live--our potential fifth mission. Furthermore, I believe that lessons from space medicine may offer some strategies to accomplish this goal.

Intra-abdominal pressure effects on porcine thoracic compliance in weightlessness: implications for physiologic tolerance of laparoscopic surgery in space

OBJECTIVE

Laparoscopic surgery (LS) is envisioned as an option for spaceflight, but requires intra-abdominal hypertension (IAH) to create the surgical domain. Prolonged weightlessness induces physiologic deconditioning that questions the ability of ill or injured astronauts to tolerate IAH. On earth, IAH results in marked ventilatory embarrassment. As there has been no previous study of physiologic changes related to LS in weightlessness, we studied anesthetized pigs in parabolic flight.

DESIGN

Parabolic flight research laboratory.

SUBJECTS

Five anesthetized Yorkshire pigs.

INTERVENTIONS

Subjects were transported from an animal care facility and secured aboard an aircraft capable of generating hypergravity and weightlessness. Mechanical ventilation was performed using pressure control and positive end-expiratory pressure at 15 and 2 cm H2O, respectively; rate 12 breaths/min. Three abdominal conditions were used during LS: insufflation to produce IAH, abdominal wall retraction (AWR), and no abdominal wall manipulation (baseline). During each parabola breath by breath-tidal volumes (Vt) were recorded by a transport ventilator (HT-50 Newport Medical).

MEASUREMENTS AND MAIN RESULTS

Least square means (LS-means) of weight corrected Vt (milliliter per kilogram) by gravity (g) and abdominal condition were determined using a mixed effects model for repeated measures analysis. Increasing gravity (g) consistently reduced Vt (p = 0.0011) as did insufflation (p < 0.0001). In 1g, Vt (LS-mean 13.7, 95% confidence interval [CI]: 12.4-15.0) was relatively unaffected by AWR (LS-mean 12.8, 95% CI: 11.5-14.00), but markedly decreased by IAH (LS-mean 10.00, 95% CI: 8.9-11.1), an effect accentuated in hypergravity (LS-mean 8.1, 95% CI: 6.4-9.8). In weightlessness, Vt reduction during insufflation was near obviated (LS-mean 12.3, 95% CI: 10.6-14.1), and AWR regularly but inconsistently increased the Vt above 1g baseline (LS-mean 13.7, 95% CI: 11.7-15.8).

CONCLUSIONS

Weightlessness protects against thoracic compliance changes that are inherent in IAH during induced pneumoperitoneum in gravity. The technique-related physiologic cost of performing LS in space deconditioned astronauts should be incorporated into design concepts for space surgery systems.

Severe traumatic injury during long duration spaceflight: Light years beyond ATLS

Traumatic injury strikes unexpectedly among the healthiest members of the human population, and has been an inevitable companion of exploration throughout history. In space flight beyond the Earth's orbit, NASA considers trauma to be the highest level of concern regarding the probable incidence versus impact on mission and health. Because of limited resources, medical care will have to focus on the conditions most likely to occur, as well as those with the most significant impact on the crew and mission. Although the relative risk of disabling injuries is significantly higher than traumatic deaths on earth, either issue would have catastrophic implications during space flight. As a result this review focuses on serious life-threatening injuries during space flight as determined by a NASA consensus conference attended by experts in all aspects of injury and space flight.In addition to discussing the impact of various mission profiles on the risk of injury, this manuscript outlines all issues relevant to trauma during space flight. These include the epidemiology of trauma, the pathophysiology of injury during weightlessness, pre-hospital issues, novel technologies, the concept of a space surgeon, appropriate training for a space physician, resuscitation of injured astronauts, hemorrhage control (cavitary and external), surgery in space (open and minimally invasive), postoperative care, vascular access, interventional radiology and pharmacology.Given the risks and isolation inherent in long duration space flight, a well trained surgeon and/or surgical capability will be required onboard any exploration vessel. More specifically, a broadly-trained surgically capable emergency/critical care specialist with innate capabilities to problem-solve and improvise would be desirable. It will be the ultimate remote setting, and hopefully one in which the most advanced of our societies' technologies can be pre-positioned to safeguard precious astronaut lives. Like so many previous space-related technologies, these developments will also greatly improve terrestrial care on earth.

Clinician-performed focused sonography for the resuscitation of trauma

Traumatic death remains pandemic. The majority of preventable deaths occur early and are due to injuries or physiologic derangements in the airway, thoracoabdominal cavities, or brain. Ultrasound is a noninvasive and portable imaging modality that spans a spectrum between the physical examination and diagnostic imaging. It allows trained examiners to immediately confirm important syndromes and answer clinical questions. Newer technologies greatly increase the fidelity, accessibility, ease of use, and informatic manipulation of the results. The early bedside use of focused ultrasound as the initial imaging modality used to detect hemoperitoneum and hemopericardium in the resuscitation of the injured patient has become an accepted standard of care. Widespread dissemination of basic ultrasound skills and technology to facilitate this brings ultrasound to many resuscitative and critical care areas. Although not as widely appreciated, the focused use of ultrasound may also have a role in detecting hemothoraces and pneumothoraces, guiding airway management, and detecting increased intracranial pressure. Intensivists generally utilize a treating philosophy that requires the real-time integration of many divergent sources of information regarding their patients' anatomy and physiology. They are therefore positioned to take advantage of focused resuscitative ultrasound, which offers immediate diagnostic information in the early care of the critically injured.