Adenosine, lidocaine, and Mg2+ (ALM) resuscitation fluid protects against experimental traumatic brain injury

Safety evaluation of adenosine, lidocaine and magnesium (ALM) intranasal therapy toward human nasal epithelial cells in vitro

Adenosine, lidocaine and Mg2+ (ALM) solution is an emerging therapy that reduces secondary injury after intravenous administration in experimental models of traumatic brain injury (TBI). Intranasal delivery of ALM may offer an alternative route for rapid, point-of-care management of TBI. As a preliminary safety screen, we evaluated whether ALM exerts cytotoxic or inflammatory effects on primary human nasal epithelial cells (pHNEC) in vitro. Submerged monolayers and air-liquid interface cultures of pHNEC were exposed to media only, normal saline only, therapeutic ALM or supratherapeutic ALM for 15 or 60 min. Safety was measured through viability, cytotoxicity, apoptosis, cellular and mitochondrial stress, and inflammatory mediator secretion assays. No differences were found in viability or cytotoxicity in cultures exposed to saline or ALM for up to 60 min, with no evidence of apoptosis after exposure to supratherapeutic ALM concentrations. Despite comparable inflammatory cytokine secretion profiles and mitochondrial activity, cellular stress responses were significantly lower in cultures exposed to ALM than saline. In summary, data show ALM therapy has neither adverse toxic nor inflammatory effects on human nasal epithelial cells, setting the stage for in vivo toxicity studies and possible clinical translation of intranasal ALM therapy for TBI treatment.

Lung Protection After Severe Thermal Burns With Adenosine, Lidocaine, and Magnesium (ALM) Resuscitation and Importance of Shams in a Rat Model

The management of severe burns remains a complex challenge. Adenosine, lidocaine, and magnesium (ALM) resuscitation therapy has been shown to protect against hemorrhagic shock and traumatic injury. The aim of the present study was to investigate the early protective effects of small-volume ALM fluid resuscitation in a rat model of 30% total body surface area (TBSA) thermal injury. Male Sprague-Dawley rats (320-340 g; n = 25) were randomly assigned to: 1) Sham (surgical instrumentation and saline infusion, without burn, n = 5), 2) Saline resuscitation group (n = 10), or 3) ALM resuscitation group (n = 10). Treatments were initiated 15-min after burn trauma, including 0.7 mL/kg 3% NaCl ± ALM bolus and 0.25-0.5 mL/kg/h 0.9% NaCl ± ALM drip, with animals monitored to 8.25-hr post-burn. Hemodynamics, cardiac function, blood chemistry, hematology, endothelial injury markers and histopathology were assessed. Survival was 100% for Shams and 90% for both ALM and Saline groups. Shams underwent significant physiological, immune and hematological changes over time as a result of surgical traums. ALM significantly reduced malondialdehyde levels in the lungs compared to Saline (P = .023), and showed minimal alveolar destruction and inflammatory cell infiltration (P < .001). ALM also improved cardiac function and oxygen delivery (21%, P = .418 vs Saline), reduced gut injury (P < .001 vs Saline), and increased plasma adiponectin (P < .001 vs baseline). Circulating levels of the acute phase protein alpha 1-acid glycoprotein (AGP) increased 1.6-times (P < .001), which may have impacted ALM's therapeutic efficacy. We conclude that small-volume ALM therapy significantly reduced lung oxidative stress and preserved alveolar integrity following severe burn trauma. Further studies are required to assess higher ALM doses with longer monitoring periods.

Adenosine, lidocaine and Mg2+ update: teaching old drugs new tricks

If a trauma (or infection) exceeds the body's evolutionary design limits, a stress response is activated to quickly restore homeostasis. However, when the injury severity score is high, death is often imminent. The goal of this review is to provide an update on the effect of small-volume adenosine, lidocaine and Mg2+ (ALM) therapy on increasing survival and blunting secondary injury after non-compressible hemorrhagic shock and other trauma and infective/endotoxemic states. Two standout features of ALM therapy are: (1) resuscitation occurs at permissive hypotensive blood pressures (MAPs 50-60 mmHg), and (2) the drug confers neuroprotection at these low pressures. The therapy appears to reset the body's baroreflex to produce a high-flow, hypotensive, vasodilatory state with maintained tissue O2 delivery. Whole body ALM protection appears to be afforded by NO synthesis-dependent pathways and shifting central nervous system (CNS) control from sympathetic to parasympathetic dominance, resulting in improved cardiovascular function, reduced immune activation and inflammation, correction of coagulopathy, restoration of endothelial glycocalyx, and reduced energy demand and mitochondrial oxidative stress. Recently, independent studies have shown ALM may also be useful for stroke, muscle trauma, and as an adjunct to Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA). Ongoing studies have further shown ALM may have utility for burn polytrauma, damage control surgery and orthopedic surgery. Lastly, we discuss the clinical applications of ALM fluid therapy for prehospital and military far-forward use for non-compressible hemorrhage and traumatic brain injury (TBI).

ALM Therapy Promotes Functional and Histologic Regeneration of Traumatized Peripheral Skeletal Muscle

Skeletal muscle trauma is a common injury with a range of severity. Adenosine, lidocaine and Mg²⁺ (ALM) is a protective solution and improves tissue perfusion and coagulopathy. Male Wistar rats were anesthetized and subjected to standardized skeletal muscle trauma of the left soleus muscle with the protection of the neurovascular structures. Seventy animals were randomly assigned to saline control or ALM. Immediately after trauma, a bolus of ALM solution was applied intravenously, followed by a one-hour infusion. After 1, 4, 7, 14 and 42 days, the biomechanical regenerative capacity was examined using incomplete tetanic force and tetany, and immunohistochemistry was used to examine for proliferation and apoptosis characteristics. Biomechanical force development showed a significant increase following ALM therapy for incomplete tetanic force and tetany on days 4 and 7. In addition, the histological evaluation showed a significant increase in proliferative BrdU-positive cells with ALM therapy on days 1 and 14. Ki67 histology also detected significantly more proliferative cells on days 1, 4, 7, 14 and 42 in ALM-treated animals. Furthermore, a simultaneous decrease in the number of apoptotic cells was observed using the TUNEL method. ALM solution showed significant superiority in biomechanical force development and also a significant positive effect on cell proliferation in traumatized skeletal muscle tissue and reduced apoptosis.

Protecting the injured central nervous system: Do anesthesia or hypothermia ameliorate secondary injury?

Traumatic injury to the central nervous system (CNS) and stroke initiate a cascade of processes that expand the area of tissue loss. The current review considers recent studies demonstrating that the induction of an anesthetic state or cooling the affected tissue (hypothermia) soon after injury can have a therapeutic effect. We first provide an overview of the neurobiological processes that fuel tissue loss after traumatic brain injury (TBI), spinal cord injury (SCI) and stroke. We then examine the rehabilitative effectiveness of therapeutic anesthesia across a variety of drug categories through a systematic review of papers in the PubMed database. We also review the therapeutic benefits hypothermia, another treatment that quells neural activity. We conclude by considering factors related to the safety, efficacy and timing of treatment, as well as the mechanisms of action. Clinical implications are also discussed.

Neuroprotective Effects of a Cardioplegic Combination (Adenosine, Lidocaine, and Magnesium) in an Ischemic Stroke Model

Adenosine, lidocaine, and magnesium (ALM) are clinically available cardioplegic solutions. We examined the effects of low-dose ALM on ischemic stroke in cell and animal models. Cobalt chloride (CoCl₂)-treated SH-SY5Y cells were used as a surrogate model to mimic oxygen-glucose deprivation conditions. The cells were incubated with different dilutions of ALM authentic solution (1.0 mM adenosine, 2.0 mM lidocaine, and5 mM MgSO4 in Earle's balanced salt solution). At a concentration of 2.5%, ALM significantly reduced CoCl₂-induced cell loss. This protective effect persisted even when ALM was administered 1 h after the insult. We used transient middle cerebral artery occlusion to investigate the therapeutic effects of ALM in vivo. Rats were randomly assigned to two groups-the experimental (ALM) and control (saline) groups-and infusion was administered during the ischemia for 1 h. The infarction area was significantly reduced in the ALM group compared with the control group (5.0% ± 2.0% vs. 23.5% ± 5.5%, p = 0.013). Neurological deficits were reduced in the ALM group compared with the control group (modified Longa score: 0 [0-1] vs. 2 [1-2], p = 0.047). This neuroprotective effect was substantiated by a reduction in the levels of various neuronal injury markers in plasma. These results demonstrate the neuroprotective effects of ALM and may provide a new therapeutic strategy for ischemic stroke.

Why are bleeding trauma patients still dying? Towards a systems hypothesis of trauma

Over the years, many explanations have been put forward to explain early and late deaths following hemorrhagic trauma. Most include single-event, sequential contributions from sympathetic hyperactivity, endotheliopathy, trauma-induced coagulopathy (TIC), hyperinflammation, immune dysfunction, ATP deficit and multiple organ failure (MOF). We view early and late deaths as a systems failure, not as a series of manifestations that occur over time. The traditional approach appears to be a by-product of last century’s highly reductionist, single-nodal thinking, which also extends to patient management, drug treatment and drug design. Current practices appear to focus more on alleviating symptoms rather than addressing the underlying problem. In this review, we discuss the importance of the system, and focus on the brain’s “privilege” status to control secondary injury processes. Loss of status from blood brain barrier damage may be responsible for poor outcomes. We present a unified Systems Hypothesis Of Trauma (SHOT) which involves: 1) CNS-cardiovascular coupling, 2) Endothelial-glycocalyx health, and 3) Mitochondrial integrity. If central control of cardiovascular coupling is maintained, we hypothesize that the endothelium will be protected, mitochondrial energetics will be maintained, and immune dysregulation, inflammation, TIC and MOF will be minimized. Another overlooked contributor to early and late deaths following hemorrhagic trauma is from the trauma of emergent surgery itself. This adds further stress to central control of secondary injury processes. New point-of-care drug therapies are required to switch the body’s genomic and proteomic programs from an injury phenotype to a survival phenotype. Currently, no drug therapy exists that targets the whole system following major trauma.

Immune dysfunction following severe trauma: A systems failure from the central nervous system to mitochondria

When a traumatic injury exceeds the body's internal tolerances, the innate immune and inflammatory systems are rapidly activated, and if not contained early, increase morbidity and mortality. Early deaths after hospital admission are mostly from central nervous system (CNS) trauma, hemorrhage and circulatory collapse (30%), and later deaths from hyperinflammation, immunosuppression, infection, sepsis, acute respiratory distress, and multiple organ failure (20%). The molecular drivers of secondary injury include damage associated molecular patterns (DAMPs), pathogen associated molecular patterns (PAMPs) and other immune-modifying agents that activate the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic stress response. Despite a number of drugs targeting specific anti-inflammatory and immune pathways showing promise in animal models, the majority have failed to translate. Reasons for failure include difficulty to replicate the heterogeneity of humans, poorly designed trials, inappropriate use of specific pathogen-free (SPF) animals, ignoring sex-specific differences, and the flawed practice of single-nodal targeting. Systems interconnectedness is a major overlooked factor. We argue that if the CNS is protected early after major trauma and control of cardiovascular function is maintained, the endothelial-glycocalyx will be protected, sufficient oxygen will be delivered, mitochondrial energetics will be maintained, inflammation will be resolved and immune dysfunction will be minimized. The current challenge is to develop new systems-based drugs that target the CNS coupling of whole-body function.

Anterior Cruciate Ligament Reconstruction Surgery: Creating a Permissive Healing Phenotype in Military Personnel and Civilians for Faster Recovery

Introduction

Anterior cruciate ligament (ACL) rupture in military personnel and civilians can be a devastating injury. A service member is 10 times more likely to suffer an ACL injury than their civilian counterparts, and despite successful surgical stabilization, 4%-35% will develop arthrofibrosis, over 50% will not return to full active duty, and up to 50% will develop post-traumatic osteoarthritis (PTOA) within 15 years. Equally concerning, woman are 2 to 8 times more likely to experience ACL injuries than men, which represents a major knowledge gap.

Materials and Methods

A comprehensive literature search was performed in December 2021 using structured search terms related to prevalence, risk factors, disease progression, and treatment of ACL injury and reconstruction. The literature search was conducted independently by two researchers using PubMed, Cochrane, and Embase databases, with inclusion of articles with military, civilian, and sex relevance, and exclusion of most papers with a publication date greater than 10 years. The resources used for the review reflect the most current data, knowledge, and recommendations associated with research and clinical findings from reliable international sources.

Results

Currently, there is no effective system-based drug therapy that creates a “permissive environment” to reduce synovial and cartilage stress after ACL injury and reconstruction and prevent secondary complications. We argue that progress in this area has been hampered by researchers and clinicians failing to recognize that (1) an ACL injury is a system’s failure that affects the whole joint, (2) the early molecular events define and perpetuate different injury phenotypes, (3) male and female responses may be different and have a molecular basis, (4) the female phenotype continues to be under-represented in basic and clinical research, and (5) the variable outcomes may be perpetuated by the trauma of surgery itself. The early molecular events after ACL injury are characterized by an overexpression of joint inflammation, immune dysfunction, and trauma-induced synovial stress. We are developing an upstream adenosine, lidocaine, and magnesium therapy to blunt these early molecular events and expedite healing with less arthrofibrosis and early PTOA complications.

Conclusions

ACL injuries continue to be a major concern among military personnel and civilians and represent a significant loss in command readiness and quality of life. The lack of predictability in outcomes after ACL repair or reconstruction underscores the need for new joint protection therapies. The male–female disparity requires urgent investigation.

Postinjury treatments to make early tactical aeromedical evacuation practical for the brain after TBI

BACKGROUND

Traumatic brain injury (TBI) is common in civilians and military personnel. No potential therapeutics have been evaluated to prevent secondary injury induced by the hypobaric hypoxia (HH) environment integral to postinjury aeromedical evacuation (AE). We examined the role of allopurinol, propranolol, adenosine/lidocaine/magnesium (ALM), or amitriptyline administration prior to simulated flight following murine TBI.

METHODS

Mice underwent TBI and were given allopurinol, propranolol, amitriptyline, or ALM prior to simulated AE or normobaric normoxia (NN) control. Heart rate (HR), respiratory rate, and oxygen saturation (Spo2) were recorded throughout simulated AE. Mice were sacrificed at 24 hours, 7 days, or 30 days. Serum and cerebral cytokines were assessed by enzyme-linked immunosorbent assay. Motor function testing was performed with Rotarod ambulation. Immunohistochemistry was conducted to examine phosphorylated tau (p-tau) accumulation in the hippocampus at 30 days.

RESULTS

While all treatments improved oxygen saturation, propranolol, amitriptyline, and allopurinol improved AE-induced tachycardia. At 24 hours, both propranolol and amitriptyline reduced tumor necrosis factor alpha levels while allopurinol and ALM reduced tumor necrosis factor alpha levels only in NN mice. Propranolol, amitriptyline, and ALM demonstrated lower serum monocyte chemoattractant protein-1 7 days after AE. Both amitriptyline and allopurinol improved Rotarod times for AE mice while only allopurinol improved Rotarod times for NN mice. Propranolol was able to reduce p-tau accumulation under both HH and NN conditions while ALM only reduced p-tau in hypobaric hypoxic conditions.

CONCLUSION

Propranolol lowered post-TBI HR with reduced proinflammatory effects, including p-tau reduction. Amitriptyline-induced lower post-TBI HR and improved functional outcomes without affecting inflammatory response. Allopurinol did not affect vital signs but improved late post-TBI systemic inflammation and functional outcomes. Adenosine/lidocaine/magnesium provided no short-term improvements but reduced p-tau accumulation at 30 days in the HH cohort. Allopurinol may be the best of the four treatments to help prevent short-term functional deficits while propranolol may address long-term effects.

LEVEL OF EVIDENCE

Basic science article.

Traumatic Brain Injury-A Review of Intravenous Fluid Therapy

This manuscript will review intravenous fluid therapy in traumatic brain injury. Both human and animal literature will be included. Basic treatment recommendations will also be discussed.

Toward an Electrical Analog of the Cardiovascular System in Hemorrhage

Current quantitative descriptions of the cardiovascular system in hemorrhagic shock focus on pressure based metrics. This approach is often incomplete; overlooking the important role of tissue perfusion. Electrical analogs to the cardiovascular system may offer a more complete description of hemorrhage. Application of fundamental concepts in electrical circuit theory (i.e.; Kirchhoff's Voltage Law and Ohm's Law) to analogs of the cardiovascular system offers a more refined description of this complex process. This manuscript hopes to serve as a starting point for a more mathematically robust, and clinically relevant description of hemorrhagic shock.

Living in a Hostile World: Inflammation, New Drug Development, and Coronavirus

We present a brief history of the immune response and show that Metchnikoff's theory of inflammation and phagocytotic defense was largely ignored in the 20th century. For decades, the immune response was believed to be triggered centrally, until Lafferty and Cunningham proposed the initiating signal came from the tissues. This shift opened the way for Janeway's pattern recognition receptor theory, and Matzinger's danger model. All models failed to appreciate that without inflammation, there can be no immune response. The situation changed in the 1990s when cytokine biology was rapidly advancing, and the immune system's role expanded from host defense, to the maintenance of host health. An inflammatory environment, produced by immune cells themselves, was now recognized as mandatory for their attack, removal and repair functions after an infection or injury. We explore the cellular programs of the immune response, and the role played by cytokines and other mediators to tailor the right response, at the right time. Normally, the immune response is robust, self-limiting and restorative. However, when the antigen load or trauma exceeds the body's internal tolerances, as witnessed in some COVID-19 patients, excessive inflammation can lead to increased sympathetic outflows, cardiac dysfunction, coagulopathy, endothelial and metabolic dysfunction, multiple organ failure and death. Currently, there are few drug therapies to reduce excessive inflammation and immune dysfunction. We have been developing an intravenous (IV) fluid therapy comprising adenosine, lidocaine and Mg2+ (ALM) that confers a survival advantage by preventing excessive inflammation initiated by sepsis, endotoxemia and sterile trauma. The multi-pronged protection appears to be unique and may provide a tool to examine the intersection points in the immune response to infection or injury, and possible ways to prevent secondary tissue damage, such as that reported in patients with COVID-19.

Fluids of the Future

Fluids are a vital tool in the armament of acute care clinicians in both civilian and military resuscitation. We now better understand complications from inappropriate resuscitation with currently available fluids; however, fluid resuscitation undeniably remains a life-saving intervention. Military research has driven the most significant advances in the field of fluid resuscitation and is currently leading the search for the fluids of the future. The veterinary community, much like our civilian human counterparts, should expect the fluid of the future to be the fruit of military research. The fluids of the future not only are expected to improve patient outcomes but also be field expedient. Those fluids should be compatible with military environments or natural disaster environments. For decades, military personnel and disaster responders have faced the peculiar demands of austere environments, prolonged field care, and delayed evacuation. Large scale natural disasters present field limitations often similar to those encountered in the battlefield. The fluids of the future should, therefore, have a long shelf-life, a small footprint, and be resistant to large temperature swings, for instance. Traumatic brain injury and hemorrhagic shock are the leading causes of preventable death for military casualties and a significant burden in civilian populations. The military and civilian health systems are focusing efforts on field-expedient fluids that will be specifically relevant for the management of those conditions. Fluids are expected to be compatible with blood products, increase oxygen-carrying capabilities, promote hemostasis, and be easy to administer in the prehospital setting, to match the broad spectrum of current acute care challenges, such as sepsis and severe systemic inflammation. This article will review historical military and civilian contributions to current resuscitation strategies, describe the expectations for the fluids of the future, and describe select ongoing research efforts with a review of current animal data.

Immunotherapeutic options for inflammation in trauma

BACKGROUND

Surgical management of trauma in the last 20 years has evolved in parallel with the military's experience in the current conflicts. Therapies such as widespread tourniquet use, empiric administration of fresh frozen plasma, and airborne intensive care units had been viewed skeptically but are now common practice. There is an opportunity to expand the envelope of care even further through similarly innovative approaches and varied avenues of research.

RESULTS

As the molecular biology of trauma is elucidated, research methodologies must also be developed to capitalize on innovative approaches to resuscitation. Blood component therapy and control of bleeding remain as the fundamental concepts in trauma care. The inflammo-immune response to injury, however, plays an increasingly recognized role in recovery of organ function. Perhaps the inflammatory cascade of trauma can be manipulated to extend the treatment envelope of at risk trauma patients.In trauma, the additional challenge of delivering effective treatment, often required very early after injury, necessitates the development of treatments to be implemented on the front lines of trauma care that are cost-effective, portable, and environmentally stable. Future conflicts may not offer ready access to high-level surgical care; therefore, resuscitative therapies will be needed for wounded service members because they are evacuated to the surgeon. Manipulation of the inflammatory response to trauma may offer a solution. As our understanding of the immune response continues to develop, the potential for improved outcomes for the wounded expands.

CONCLUSION

A review of basic concepts in immunology is necessary to appreciate any potential impact of immunotherapeutic approaches to trauma and inflammation. An overview of current options will focus on outcome benefits of available therapies and suggest possible areas for future investigation. Quantitative approaches will leverage basic science to identify high-yield strategies to improve care of the injured combatant.

LEVEL OF EVIDENCE

Review, level III.

Adenosine, Lidocaine, and Magnesium Support a High Flow, Hypotensive, Vasodilatory State With Improved Oxygen Delivery and Cerebral Protection in a Pig Model of Noncompressible Hemorrhage

BACKGROUND

Noncompressible hemorrhage is the leading cause of preventable death in military and civilian trauma. Our aim was to examine the effect of adenosine, lidocaine, and magnesium (Mg²⁺; ALM) on cardiovascular and cerebral function in a porcine hepatic hemorrhage model.

MATERIALS AND METHODS

Pigs (59.1 ± 0.34 kg) were anesthetized, instrumented, and randomly assigned into sham (n = 6), saline controls (n = 10) or ALM (n = 10) groups before laparoscopic liver resection. After 30 min, groups received 4 mL/kg 3% NaCl ± ALM bolus (Phase 1) followed 60 min later with 3 mL/kg/h 0.9% NaCl ± ALM drip (4 h; Phase 2), then transfusion. Hemodynamics, carotid artery flow, and intracranial pressure were measured continuously. Microdialysis samples were analyzed for metabolites.

RESULTS

Saline controls had 20% mortality (mean survival time: 307 ± 38 min) with no ALM deaths over 6 h. Bolus administration increased mean arterial pressure (MAP) in both groups, and drip led to further increases to 62 ± 10 mmHg in controls compared with a steady fall to 47 ± 8 mmHg in ALM group at 240 min. The lower MAP was associated with a dramatic fall in systemic vascular resistance and improved oxygen delivery. ALM drip significantly increased cardiac output and stroke volume with lower dP/dt_Min, indicating a less stiff heart. ALM drip also significantly decreased cerebral perfusion pressure, reduced cerebral oxygen consumption (28%), and reduced brain glycerol (60%), lactate (47%), and relative expression of hypoxia-inducible factor (38%) compared with saline controls.

CONCLUSIONS

ALM therapy improved cardiac function and oxygen delivery by lowering systemic vascular resistance after noncompressible hemorrhage. ALM also appeared to protect the brain at hypotensive MAPs with significantly lower cerebral perfusion pressure, lower O₂ consumption, and significantly lower cortical lactate and glycerol levels compared to saline controls.

Absence of cytotoxic and inflammatory effects following in vitro exposure of chondrogenically-differentiated human mesenchymal stem cells to adenosine, lidocaine and Mg2+ solution

Background

ALM solution, a combination of adenosine, lidocaine and Mg²⁺, is an emerging small volume therapy that has been shown to prevent and correct coagulopathy and surgery-related inflammation in preclinical models, though its application in orthopaedic surgery is yet to be demonstrated. The effect of ALM solution on chondrocytes is unknown. The aim of this preliminary study was to investigate the effect of ALM solution on viability and inflammatory responses of chondrogenically-differentiated human bone marrow-derived mesenchymal stem cells (chondro-MSC), in vitro.

Methods

Chondro-MSC were exposed to media only, saline (0.9% NaCl or 1.3% NaCl) only, or saline containing ALM (1 mM adenosine, 3 mM lidocaine, 2.5 mM Mg²⁺) or tranexamic acid (TXA, 100 mg/ml) for 1 or 4 h. Responses to ALM solutions containing higher lidocaine concentrations were also compared. Chondrocyte viability was determined using WST-8 colorimetric assays and inflammatory cytokine (TNF-α, IL-1β, IL-8) and matrix metalloproteinases (MMP-3, MMP-12, MMP-13) concentrations using multiplex bead arrays.

Results

The viability of chondro-MSC was significantly greater after 1 h treatment with ALM compared to saline (96.2 ± 7.9 versus 75.6 ± 7.3%). Extension of exposure times to 4 h had no significant adverse effect on cell viability after treatment with ALM (1 h, 85.4 ± 5.6 v 4 h, 74.0 ± 15.2%). Cytotoxicity was evident following exposure to solutions containing lidocaine concentrations greater than 30 mM. There were no significant differences in viability (80 ± 5.4 v 57.3 ± 16.2%) or secretion of IL-8 (60 ± 20 v 160 ± 50 pg/ml), MMP-3 (0.95 ± 0.6 v 3.4 ± 1.6 ng/ml), and MMP-13 (4.2 ± 2.4 v 9.2 ± 4.3 ng/ml) in chondro-MSC exposed to saline, ALM or TXA.

Conclusions

Short-term, in vitro exposure to clinically-relevant concentrations of ALM solution had no adverse inflammatory or chondrotoxic effects on human chondro-MSC, with responses comparable to saline and TXA. These findings provide support for continued evaluation of ALM solution as a possible therapeutic to improve outcomes following orthopaedic procedures.