Inflammation and Trauma

• Physical trauma is any physical injury resulting from external forces acting on the body.
• Trauma is often divided into blunt and penetrating injuries, though this ignores other causes like barotrauma and burns.
• Major trauma, which can cause lasting disability or death, accounts for an estimated 10% of worldwide deaths.
• Trauma is considered a disease with predictable patterns and modifiable outcomes, rather than a random accident.
• Trauma disproportionately affects young people, leading to a higher loss of disability-adjusted life years (DALYs).
• Males are more prone to trauma due to higher engagement in risky activities.
• Low socioeconomic and low- to middle-income countries (LMICs) experience higher rates of trauma, death, and disability.
• The economic burden of trauma accounts for up to 15% of the gross domestic product in LMICs.
• Trauma is a public health issue requiring prevention at primary, secondary, and tertiary levels.
• Survival from major trauma is time-sensitive, with the "golden hour" referring to the period after the event when medical treatment maximizes survival.

Immediate and Early Deaths

• Immediate deaths at the injury scene usually result from severe physiological issues. These include obstructed airways, brain lacerations, or massive hemorrhage.
• Early deaths occur due to uncontrolled moderate hemorrhage, while later deaths often result from organ failure and sepsis.

Post-Trauma Care

• Improvements in out-of-hospital care have improved morbidity and mortality after trauma.
• Early deaths from hemorrhage can be reduced using prehospital interventions like pressure bandages, tourniquets, intravenous drugs (tranexamic acid), topical hemostatic agents, and surgical interventions.
• Later deaths due to trauma-induced coagulopathy have been studied, suggesting prehospital management changes like temperature maintenance and reduced fluid administration.
• Out-of-hospital trauma deaths are more common in younger patients, while older patients tend to die in hospitals.
• Transport accidents, penetrating injuries, hanging and drowning injuries are more likely to lead to death outside of hospitals, while falls from low heights are more likely to lead to death in hospitals.

Injury Severity Score (ISS)

• Major trauma, or polytrauma, is defined as an Injury Severity Score (ISS) greater than 15.
• The ISS measures traumatic injury severity, assigning scores from 1 (minor) to 6 (unsurvivable) based on injured body regions.
• The three most severely injured region scores are squared and summed to create a total ISS, ranging from 1 to 75 (75 automatically assigned for any region scored 6).
• Mild severity is indicated by a score less than 9, moderate 9-15, severe injury 16-24, and profound injury over 25.
• The ISS correlates with morbidity, mortality, and length of hospital stay.
• A moderate pelvic fracture with blood loss of 20% or less scores 4, translating to an ISS of 16, signifying a major trauma patient.

Impact of Trauma on the Body

• Physical trauma initiates immunological and metabolic responses to restore homeostasis.
• Disruption of cell walls (micro barriers) and the skin's integrity (macro barrier) activates the innate immunity as an early defense.
• It triggers the clotting cascade to limit damage and promote healing, but can lead to complications and fatal outcomes.
• Timely out-of-hospital care plays a major role in improving major trauma outcomes.
• Homeostasis, the body's ability to self-regulate, is commonly impacted by hypovolaemia in trauma patients, making haemostasis the key focus.

Phases of Haemostasis

• Haemostasis includes vascular, platelet, and coagulation phases.
• These phases are interlinked and compound each other, resulting in significant health deterioration.
• In the Vascular Phase, smooth muscle in the vessel wall contracts when a blood vessel is damaged causing vascular spasm. Vascular spasm lasts about 30 minutes from the point-of-injury.
• Platelets are repelled by the endothelium until the vessel is damaged and collagen fibers are exposed.
• During blood-clotting, platelets release adenosine diphosphate (ADP), thromboxane and serotonin, which causes vascular spasms.
• Vascular spasms attract more platelets to the injury site.
• A platelet plug, a 'pile' of platelets, is formed by the aggregate as well as previously adhered platelets.
• The Coagulation Phase includes activation of clotting factors referred to as the coagulation cascade, which leads to haemostasis and rapid healing.
• Coagulation can happen via the intrinsic or extrinsic pathway, which activates the common pathway to creates fibrin mesh.
• The intrinsic pathway is initated when protease reactions within the blood encounter the damaged blood vessel lining . It takes between three and six minutes.
• The extrinsic pathway involves transmembrane receptor tissue factor, resulting in the activation of factor X.

Common & Inflammatory Pathways

• Fibrin binds the platelets to stabilize the plug.
• After the plug, the inflammatory response (inflammation) happens when body tissues are injured by trauma.
• Damaged cells release histamine, prostaglandins and bradykinins, which results in leaky blood vessels and fluid loss to tissues.
• Inflammation results in oedema, redness and pain.
• These chemicals reduce blood pressure, but attract white blood cells and plasma proteins to destroy bacteria and engulf damaged cells.
• The triad of death, or lethal triad, includes coagulopathy, hypothermia and metabolic acidosis. This triad has a 90% death rate in severe trauma.

Additional Trauma info

• Haemorrhage, either internal or external reduces blood volume, which reduces core body temperature and hypoperfusion.
• Hypoperfusion causes tissues to be hypoxic, using anaerobic respiration to produce lactic acid, and leads to acidosis.
• Acidosis with hypothermia slows the coagulation cascade, creating coagulopathy.
• Coagulopathy prevents haemostasis, which causes further bleeding which further impairs myocardial performance.
• Management of major trauma involves stopping the bleed, keeping the patient warm and maintaining blood pressure, and avoiding blood dilution with fluids.
• The normal core body temperature is 35.6–37.8°C, with an average rectal temperature around 37.0°C.
• Hypothermia is a core temperature of less than 35.0°C, with two-thirds of patients major trauma patients experiencing hypothermia.
• Hypothermia leads to overall higher mortality, higher hospital stay duration and higher infusion rates.
• Reduced body temperature triggers heat-generating to mechanisms to return body to normal limits.
• People with reduced body temperature triggers the hypothalamus causes to body to shiver, which requires increased cellular respiration to meet energy demand.
• Blood regulates body temperature, absorbing heat from skeletal muscle and distributing it to other tissues.
• Low body temperature restricts flow to to vital organs.
• Heat decreases due to hypoperfusion or hypovolemia, as seen in trauma patients, which causes a rapid drop in body temperature.
• Hypothermia can cause a shift in the oxygen disassociation curve, affecting tissues, cardiac output and coagulation.
• A temperture of 36.6°C is directly connected to clotting factors.
• Hypothermia delays enzymes during coagulation, prolonging coagulation time, and reducing a hospital admission survival rate to 0% if less than 32°C.
• There are risk factors for hypothermia influences by paramedic care. Seriousness of the injury, recent intubation, wet clothing, environmental temperature and administering cold fluids.
• Management includes removing the patient from cold or wet environments, providing blankets, heat, warm fluids, and gentle handling to reduce cardiac dysrhythmias.
• Coagulopathy is a blood clotting problem common in 25% of trauma patients.
• It happens from haemorrhage, haemodilution, clotting factors, hypothermia and acidotic conditions, and can result in disseminated intravascular coagulation (DIC).
• DIC causes small blood clots in blood vessels, obstructing blood flow to vital organs, and creating a deficiency of clotting factors needed for haemostasis leading to more bleeding.
• Management includes preventing hypothermia, preventing further bleeding and restoring blood volume.
• Avoid large volumes of crystalloids like saline, as they can lead to coagulopathy and dislodge clots. For transport, coagulation factor concentrates are needed, as well as vitamin K. The body uses aerobic respiration, which converts adenosine triphosphate (ATP).

Metabolic Acidosis

• Hypovolaemia reduces oxygen delievery and the body is unable to keep up with oxygen demand. Tissues start to respire anaerobically, creating lactic acid, which leads to metabolic acidosis
• Clotting factors active during haemostasis are affected by pH. Normal body pH is 7.35 - 7.45.
• If the pH is outside of this range, it denatures clotting enzymes, disrupting coagulation. Thrombin generation alters when the pH is below 7.3, and acidosis slows down intrinsic and extrinsic coagulation pathways.
• Acidosis lowers myocardial contractility and cardiac output, causes vasodilation, hypotension, reduces blood flow to organs, and can lead to ventricular dysrhythmias.
• Management includes management of hypoxia and hyperperfusion. High-flow oxygen and rapid fluid administration must be essential, but tranexamic acid and prothrombin have been shown to reverse severe acidosis.
• Rapid transport to an emergency department with major trauma management capabilities is essential to reduce morbidity and mortality.