Endotoxaemia in the horse (Pathophysiology (Innate immune response to LPS…
Endotoxaemia in the horse
"Presence of LPS in the blood", often used to describe an overbearing pro-inflammatory reaction to the presence of LPS.
Commonly associated with translocation of Gram(-) GIT bacteria due to intestinal compromise (e.g. ischaemia, inflammation, necrosis), GIT dysbiosis (colitis), peritonitis, endometritis and pneumonia/pleuropneumonia.
Many possible causes, but abdominal/GIT disease is commonly implicated.
May result in the systemic inflammatory response syndrome (SIRS - refer to flowchart).
Innate immune response to LPS results in activation of macrophages and release of pro-inflammatory cytokines. This response is normally controlled via concurrent release of anti-inflammatory cytokines.
Excessive release of pro-inflammatory cytokines (IL-1, TNFa) by macrophages results in SIRS.
SIRS results in endothelial damage, neutrophil-mediated tissue damage, uncontrolled activation of coagulation. fibrinolytic and complement cascades.
Ultimately results in CVS instability, impaired haemostasis, organ failure, distributive shock, and potentially death.
Distributive (vasodilatory) shock is refractory hypotension resulting from cardiac dysfunction, vasoplegia/endothelial damage and fluid extravasation.
MODS is a potential sequelae of the SIRS syndrome.
Initial risk of thrombosis (results in infarction)
Later risk of consumptive coagulopathy
Neutrophil-mediated damage of lamellae, leading to separation from the hoof wall
Increased founder distance, altered hoof wall thickness, reduced sole depth, +/- gas (due to hoof wall separation)
Resuscitation using isotonic, polyionic crystalloids (Hartmann's, LRS) at 10-20 mL/kg/hr (severe shock may require higher rates). Maintenance rates (2-4 mL/kg/hr) + ongoing losses once stabilised.
If functioning GIT, provide oral electrolytes
Broad-spectrum antimicrobials (Pen/Gent)
NSAIDs (flunixin) - flunixin has both an analgesic and "anti-endotoxin" effect
Distal limb cryotherapy
Only proven method to prevent laminitis with systemic inflammatory states
Fresh frozen plasma + anticoagulant
Replaces coagulation factors, provides colloidal support and prevents microthrombosis)
Sepsis: SIRS induced by infection
Septicaemia: pathogenic microorganisms and their toxins in blood
SIRS: overbearing pro-inflammatory reaction that has multiple causes. Recognised by core temp abnormality, HR abnormality, tachypnoea and WBC dernagements
Endotoxaemia: presence of LPS in blood
Depression, injected MMs, prolonged CRT (hypotension), colic signs (abdominal pain, tachycardia, ileus), core temperature derangement, cool extremities, +/-haemorrhage (internal/external), icterus, anorexia, laminitis.
Variable. Leukopaenia (neutropaenia +/- toxic change), haemoconcentration, azotaemia, elevated liver enzymes, thrombocytopaenia, hypoproteinaemia (may be masked by haemoconcentration), metabolic acidosis, coagulopathy.