Final Exam - Emergent Colic Patient Flashcards
when working up a colicking horse, every case begins with what?
signalment
history/risk factors
physical exam
what is the most commonly used sedative in equine patients for colic? how can this drug alter physical exam findings? what does this mean for your exam?
xylazine (rompun) - alpha 2 agonist
tachypnea & antipyresis in febrile horses - need to get your PE parameters before hand!!!
what should you be able to palpate on a normal, healthy horse with a rectal exam?
structures cranial to the root of the mesentery are out of reach (level of the L1 vertebra)
bladder
female reproductive tract in the mare
inguinal canals and Urethra of the stallion
caudal border of the spleen
nephrosplenic ligament
caudal pole of the left kidney
mesenteric root
ventral cecal tenia (no tension should be palpable)
cecal base (should be empty in the normal horse)
small colon containing fecal balls
pelvic flexure
what do you think of a colic horse that has hyperemic mucus membranes & a toxic line?
endotoxemia is going on
what is the pathophysiology of endotoxemia in the horse?
gram negative bacteria (most common in the gi tract) - may be inhaled, respiratory infection, iatrogenic administration, or there is damage to the gi mucosa that allows for translocation of bacteria
normal defenses against LPS - enterocyte endothelium, mucus layer, tissue macrophages, & kupffer cells
endotoxin in the blood - LPS is shuttled to the receptor cell & signal is translocated to the host immune cell nucleus
nuclear transcription factors produce inflammatory cytokines IL-1 & TNF-a which are responsible for the clinical signs of endotoxemia
T/F: endotoxemia often leads to neutropenia
true
why do we see a toxic line in horses with endotoxemia?
all of these mechanisms from endotoxemia lead to altered vascular permeability (why we see blood pooling in the periphery, toxic line) & other associated clinical signs of hypercoagulability & inflammation (fever, tachycardia, & neutropenia)
what is the hallmark of endotoxemia/endotoxemic shock in the horse?
laminitis
why does laminitis occur in horses with endotoxemia?
it is a secondary disease process
systemic illness in horses - inflammatory mediators affect the basement membrane, which affects the lamina of the hoof, so there is separation of the sensitive dermal lamina from the insensitive primary epidermal lamina
what are 4 differentials for colitis in an adult horse?
- potomac horse fever - neorickettsia risticii
- antibiotic associated colitis - clostridium difficile
- salmonellosis
- cyathostomiasis
how would you rule out salmonellosis in a colic horse with colitis?
salmonella fecal culture - takes about 48 hours for results
how would you rule out cyathostomiasis in a colic horse with colitis?
fecal egg count
consider seasonality - would be odd to see massive excystation in the heat of summer
hypobiosis - may remain encysted as hypobiotic L3 for months to years in very cold or very hot climates
what are the only 2 FDA approved therapies for treating encysted cyathostomes in horses?
fenbendazole - interferes with intracellular structure of the worms & their energy metabolism, double dose them for 5 days at 10 mg/kg PO
moxidectin - binds chloride channels in the worms causing paralysis/death, single dose at 400 ug/kg PO
what is a normal USG in an adult horse?
> 1.025
T/F: urine concentration is directly related to the health of the renal system
true
what is hypersthenuria?
concentrated urine
what is it called when a horse has a USG of 1.008-1.012? what does it indicate?
isosthenuria - primary renal dysfunction
what is it called when a horse has a USG < 1.010? what does it indicate?
hyposthenuria - dilute urine
how would you rule out potomac horse fever in a colic horse with colitis?
look for PLE with clinical signs & blood work
their response to treatment
PCR on blood or feces with results in about 48 hours
how would you rule out antibiotic-associated colitis in a colic horse?
toxin A/B PCR on blood or feces with results taking a few days
look for PLE with clinical signs & blood work
why should you consider anorexia if a colicking horse has hyperbilirubinemia?
anorexia will cause fasting hyperbilirubinemia - so may see increased total bilirubin without liver disease (indirect bilirubin only) & all other liver enzymes would be within normal limits
how do clostridium species cause problems in horses?
clostridiums are gram positive spore-forming anaerobic rods that are considered to be a normal part of intestinal flora, but they can overgrow & colonize the colonic mucosa in periods of stress, immunosuppression, & in the face of antimicrobial therapy (because it alters microflora in the gut)
what are some antibiotics that are commonly known to cause colitis in horses?
erythromycin PO, TMS PO, ceftiofur IV, ampicillin PO, lincomycin PO, & neomycin
what is the most common clostridial agent associated with causing antibiotic associated colitis?
clostridium difficle
what is the pathogenesis of c. difficile infections in horses?
c. difficile has toxins A & B
elaboration of the exotoxins cause enterocyte damage & increased intestinal permeability
hemorrhagic diarrhea is common
what is the basis of therapy for clostridium difficile colitis in horses?
metronidazole
fluid therapy
reduce inflammation - from endotoxemia
prevent laminitis
good biosecurity protocols
with history of antibiotic use - discontinue antibiotic immediately & switch to metro instead at 15 mg/kg PO every 8-12 hours
T/F: diarrhea, not matter the etiology, is considered an emergency in adult equine patients
true
what is the acute treatment used for preventing laminitis in an acute colitis case?
cryotherapy - initiated prior to clinical signs for best results
timing is critical
what is this? what is it used for?
cryotherapy
laminitis prophylaxis
what are some examples of anti-endotoxemia therapy used in a horse with acute colitis?
NSAIDs
polymixin B (6000 IU/kg every 8 hours)
equine plasma (20 mg/kg)
how is nutritional support handled for acute colitis horses?
nutritional support is critical & gi tract is dysfunctional
if NPO > 72 hours, TPN is indicated to supply glucose, amino acids, & lipids - this requires a dedicated IV line that has to be replaced daily to reduce the risk of iatrogenic endotoxemia
what cytokines are responsible for causing the clinical signs of endotoxemia? what others are going on?
IL-1 & TNF
nitric oxide, histamine, reactice oxygen species, TF stimulation, complement, & neutrophil activation
why do we see toxic lines occur in endotoxemia?
vascular permeability -> blood pools -> toxic line
endotoxemia is a giant risk factor for what???????
laminitis!!! secondary disease process!!!
do probiotics help prevent the occurrence of antibiotic associated colitis in horses?
nope!
what are some reasons we see clostridium species causing colitis in horses?
normal intestinal flora until they overgrow in response to stress, immunosuppression, & antimicrobial therapy
why may you see hypoalbuminemia in horses? how do you work this up?
decreased production or loss - check for evidence of liver disease
if elevated liver enzymes - suggests hepatic insufficiency
if liver enzymes are normal - lean towards loss for hypoalbuminemia
what is it called when a horse has a USG > 1.025? what does it indicate?
normally concentrated urine - can be hypersthenuria
what would be a supportive history of potomac horse fever (neorickettsia risticii) causing colitis in an adult horse? what diagnostics would you want to diagnose it?
seasonality - transmitted by flies & snails
environment - fresh water on the premises
PCR (48 hours), signs of PLE, & patient response to treatment
what would be a supportive history of antibiotic-associated colitis causing disease in an adult horse? what diagnostics would you want to diagnose it?
clostridium dificile
supportive history of antimicrobial therapy
diagnostics - toxin A/B PCR (blood, feces - results in several days), & look for PLE
what would be a supportive history of salmonellosis causing colitis in an adult horse? what diagnostics would you want to diagnose it?
horses with a travel history - doesn’t have to have diarrhea to shed salmonella in the feces!!!
salmonella fecal culture - takes 48 hours to get results
what would be a supportive history of cyathostomiasis causing colitis in an adult horse? what diagnostics would you want to diagnose it?
deworming history!
fecal egg count, but need to consider seasonality! extreme temperatures will cause hypobiosis of the larvae, so it would be weird to see massive excystation in summer or winter
some populations of horses are resistant to benzimidazole!!!
what are the only approved products for treating encysted cyathostomes?
fenbendazole & moxidectin
why would you not be shocked to see increased bilirubin in a horse that hasn’t been eating? what would help support this theory from clinical pathology findings?
horses get a fasting hyperbilirubinemia when they are anorexic
run some labs! increased total bilirubin without any liver disease (indirect bilirubin only) & all other liver enzymes are within normal limits
