RODENTICIDE INTOXICATION
Case Study Week 8
Sarra Borne
VETE 405
Sarra Borne UID 000493586
VETE 405: Pharmacology and Pharmacy
Assignment: Case Study Week 8: Rodenticide Intoxication in a Dog
October 16, 2013
Mr. Gallagher brings in his dog Linus, a 3-year-old neutered Smooth Rat Terrier.
Linus has a nose bleed that won’t stop. Linus’ nose started bleeding during breakfast
which was four hours ago. Linus is up to date on his vaccinations and was acting
normally yesterday, but is tired and not himself today. Linus is an indoor/outdoor dog,
so it is unknown if his recent urination and defecation are normal.
Examination of Linus reveals his vital signs are temperature is 101.8 oF, pulse
145 bpm, and a respiratory rate of 50 bpm. Linus’ mucous membranes are pale pink
with a CRT of 2 seconds. Linus appears somewhat depressed although his neurologic
examination is normal.
Hydration, movement and abdominal palpation all appear
normal. Linus’ heart and lungs auscultate normally. Linus has moderate epistaxis and
has blood on his face, front legs and chest that appears to be from his nose. Linus
coughs during the examination and expectorates small spots of blood onto the table.
On questioning Mr. Gallagher reveals that there is rat poison kept in the garage,
and area that Linus does not usually go into. He is unsure if any has been eaten and
needs to consult with his wife.
Technician evaluations would include evaluation of mucous membrane color and
capillary refill time, obtaining a current weight, recording vital signs, and recording
pertinent history.
A complete blood count, activated clotting time (ACT), prothrombin time (PT) and
activated partial thromboplastin time (PTT) are ordered. Blood is collected from the
lateral saphenous vein using a 22g needle. The cephalic veins are saved for potential
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Sarra Borne UID 000493586
VETE 405: Pharmacology and Pharmacy
Assignment: Case Study Week 8: Rodenticide Intoxication in a Dog
October 16, 2013
intravenous catheterization.
The jugular vein is contraindicated in a suspected
rodenticide poisoning. If clotting factors are impaired it is important to use a vein on an
extremity where a pressure bandage can be applied.
The ACT or activated clotting time test is performed by adding a fresh whole
blood sample to a blood tube that contains diatomaceous earth. The tube is incubated
at 98.6o F for 3 minutes, then a clean venipuncture is performed on an unthrombosed
vessel. The first few drops of blood are discarded to eliminate tissue thromboplastin,
then approximately 2 ml is added to the ACT tube. A stopwatch is started as soon as
the blood first enters the tube. The tube is inverted several times to mix the
diatomaceous earth and the blood and the tube is returned to the incubator. After 30
seconds, the ACT tube is gently examined for clot formation.
repeated every 10 seconds until a clot is formed.
This procedure is
The ACT time is the time from
collection of blood in the tube until initial clot formation. In the dog, the normal is 60 to
110 seconds. Linus’ ACT is 230 which is outside the normal range. This indicates an
abnormality in the intrinsic and common pathway of the clotting pathway. It evaluates
the same pathways as the PTT. (Battaglia, 2001)
The PT and PTT are collected into a blue topped collection tube containing
sodium citrate. This tube should be placed on a blood rocker for 5 minutes to allow the
sodium citrate to properly mix with the blood cells. Linus’s PT is 17.2 seconds (normal
range 7 -10 seconds), and his PTT is 57 seconds (normal range 14 -20 seconds). Both
Linus’ PT and PTT are elevated. The PT measures extrinsic and common clotting
pathway activity, whereas the PTT measures the intrinsic and common clotting pathway
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Sarra Borne UID 000493586
VETE 405: Pharmacology and Pharmacy
Assignment: Case Study Week 8: Rodenticide Intoxication in a Dog
October 16, 2013
activity. Prolongation of PT and PTT is seen when clotting factors are depleted below
30% of normal. (Battaglia, 2001)
Mr. Gallagher has consulted with his wife and determined that a box of rat poison
has indeed been ripped up and moved from its usual storage area. He reports that the
active ingredient in the rodenticide is bromadiolone. Based on the laboratory findings
and clinical signs, the veterinarian is confident that Linus has indeed ingested
bromadiolone which is a vitamin K antagonist. Vitamin K antagonist rodenticides bind
the vitamin K factor, which inhibits the synthesis of prothrombin (factor II) as well as
factors VII, XI and X. (Battaglia, 2001)
The depletion of these factors slow all
coagulation pathways, which include the contact activation pathway (or intrinsic), the
tissue factor pathway (or extrinsic) and the common clotting pathway.
Partial results from Linus’ CBC are as follows
RBC 4.8 x 106/ul
WBC 9.2 x 106/ul
PCV 27%
HGB 11.2 g/dl
Reticulocytes 8 seen out of 1000 RBC
Platelets 243 x 103/ul
The veterinarian requests that the platelet count be verified. In this case a blood
smear is examined. Then platelets are estimated by counting the average number of
platelets seen per 100x oil immersion field in the monolayer. (Cornell University, n.d)
Ten fields are counted and the results are averaged, then the following formula is
applied. Estimated platelet count/ul = average count in 10 fields x 15,000. If 1000
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Sarra Borne UID 000493586
VETE 405: Pharmacology and Pharmacy
Assignment: Case Study Week 8: Rodenticide Intoxication in a Dog
October 16, 2013
platelets are counted over 10 fields the estimated platelet count is 1500K or
1,500,000/ul.
(Estimated platelet count/ul = 1000 /10 fields = 100 x 15,000 =
1,500,000/ul)
Linus has become more depressed and is still experiencing epistaxis. A whole
blood transfusion and vitamin K therapy are recommended to Mr. Gallagher who
consents. The veterinarian’s personal dog, Beast, is often used as a blood donor as he
has a known history, is up to date on vaccinations and is in excellent health. True
canine universal donors have blood type DEA 4 (C) and test negative for the other
known canine red blood cell antigens, including DEA 1.1 (A1), DEA 1.2 (A2), DEA 3 (B),
DEA 5 (D) and DEA 7 (Tr). (Hemopet, 2013)
Linus should be cross-matched to Beast to predict any serum incompatibility. He
should also be blood typed, either in clinic or at a reference laboratory to determine his
blood type in case he needs any future transfusions. Cross-matching is a two part
process.
The major cross-match assesses whether there are antibodies in Linus’
plasma that might cause a hemolytic reaction to Beast’s RBC’s. The minor cross-match
detects any antibodies in Beast’s plasma that might react to Linus’ RBC’s. In both parts
of the cross-match incompatibility is signaled by agglutination of RBC’s.
There are commercially available kits that can be used for cross-matching, or it
can be done manually using test tubes or slides.
The manual cross-match requires clotted blood from both donor and recipient.
The serum is transferred to labeled tubes and the clot is re-suspended in saline
to make an approximate 3% solution. These are each washed three times and
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Sarra Borne UID 000493586
VETE 405: Pharmacology and Pharmacy
Assignment: Case Study Week 8: Rodenticide Intoxication in a Dog
October 16, 2013
centrifuged until the supernatant is clear and colorless. After the final washing,
again suspend each washed tube of RBC’s in saline. The major cross-match
mixes two drops of recipient’s serum and 2 drops of donor’s red cell suspension.
The minor cross-match mixes 2 drops of donor’s serum and 2 drops of recipient’s
red cell suspension. The tubes are incubated for 30 minutes, centrifuged for 2
minutes and examined for hemolysis.
Significant hemolysis in either tube
indicates incompatibility. If there is no hemolysis, the supernatant should be
microscopically examined for agglutination.
Agglutination also indicates
incompatibility. (Pratt, 1997, p. 83)
To collect blood from the donor you need clippers to shave the area, alcohol and
chlorhexidine scrub to surgically prepare the venipuncture site, sterile gloves, a blood
collection bag containing anticoagulant (usually CPD), several sterile hemostats,
collection tubing and an assistant. Fresh whole blood is ideal for Linus since it contains
erythrocytes, leukocytes, platelets, coagulation factors, and plasma proteins.
All of
these are components that Linus is losing by continuing to bleed. If Linus needed an
adjunct transfusion with fresh frozen plasma (FFP) to boost his coagulation factors and
plasma proteins further, it would need to be properly thawed before transfusion. This is
done in a warm water bath that is 98.6oF (37oC).
Baseline measurements of the patient’s attitude, rectal temperature, pulse rate
and quality, respiratory rate, mucous membrane color, capillary refill time, and blood
pressure should be obtained before the transfusion is started.
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Sarra Borne UID 000493586
VETE 405: Pharmacology and Pharmacy
Assignment: Case Study Week 8: Rodenticide Intoxication in a Dog
October 16, 2013
The transfusion should be started at approximately 0.25ml/kg for the first 30
minutes, after which the rate can be increased if no reactions are seen. Vital
signs should be recorded every 15 minutes for the first 45 minutes of the
transfusion, and then every 30 minutes until the transfusion is finished.
The
patient should be closely monitored for at least 60 minutes after the transfusion is
finished.
Blood transfusions should be completed within 4 hours to prevent
functional loss or bacterial growth. (Proulx & Waddell, 2012)
The veterinarian prescribes 5 mg/kg of vitamin K SC split into 3 injection sites.
I’ve decided that Linus weighs 15 lb based on the AKC website (his weight is not
mentioned in the article) so he would receive 34 mg total. Vitamin K comes in a 10
mg/ml solution. Linus would receive 1.1 ml in two sites, and 1.2 ml in the third using a
25 g needle. (Plumb, 2011)
Prior to discharge Linus is placed on oral vitamin K twice daily with a fatty meal
for three week. At a recheck four days later Linus is brighter with no signs of bleeding.
His follow up blood work is improved:
ACT 85 seconds
PT 8.5 seconds
PTT 27 seconds
After reviewing the blood work Mr. Gallagher prepares to leave. He asks if Linus needs
to continue taking the pills, since Linus is doing well and really hates taking the pills.
Mr. Gallagher needs a reminder that bromadiolone is a second generation rodenticide,
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Sarra Borne UID 000493586
VETE 405: Pharmacology and Pharmacy
Assignment: Case Study Week 8: Rodenticide Intoxication in a Dog
October 16, 2013
and can depress clotting factors for three to four weeks, so Linus needs to get his
medication as prescribed for the length of time prescribed.
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Sarra Borne UID 000493586
VETE 405: Pharmacology and Pharmacy
Assignment: Case Study Week 8: Rodenticide Intoxication in a Dog
October 16, 2013
References
Battaglia, A. M. (2001). Small animal emergency and critical care: A manual for the
veterinary technician. Philadelphia, PA: W.B. Saunders.
Cornell University (n.d.). Platelet count. Retrieved from
https://ahdc.vet.cornell.edu/clinpath/modules/hemogram/plt_ct.htm
Hemopet (2013). The hemopet blood bank. Retrieved from hemopet.org/bloodbank.html
Hines, R. (2013). Normal feline & canine blood chemistry values. Retrieved from
http://www.2ndchance.info/normaldogandcatbloodvalues.htm
Plumb, D. C. (2011). Phytonadione (vitamin K1). In Plumb's veterinary drug handbook
(7th ed., pp. 824-826). Ames, Iowa: Wiley-Blackwell.
Pratt, P. W. (1997). Laboratory procedures for veterinary technicians (3rd ed.). St.
Louis, Mo: Mosby.
Proulx, A., & WADDELL, L. S. (2012, March). Blood transfusion basics. Retrieved from
http://www.cliniciansbrief.com/column/taxonomy/term/23406/blood-transfusionbasics
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