Ross - Exam 1 Flashcards
How should oral medication be administered?
Syringe - add mixer/binder to powder and directly inject into side of mouth
How should oral medication NOT be administered?
Mixed in feed
What size needle is appropriate for IV injections? Why?
18G, 1.5”
Minimizes likelihood of inadvertent intra-carotid injection
Which syringe type is generally avoided?
Luer LOCK
Where should the jugular be accessed? Why
Mid to upper neck
Omohyoideus muscle separates jugular form carotid
What are the three main complications associated with jugular injection?
Clostridium infection (contaminated needle) Inadvertent intra-carotid injection Laryngeal hemiplasia (perivascular injection)
What size needles are appropriate for intramuscular injections?
18/19/20 G 1.5” (no less than 21G)
What is the maximum amount that can be injected per IM site?
15-20cc
What are the three acceptable sites for IM injections?
What are the landmarks / considerations associated with each?
Neck
-ventral to ligamentum nuchae
-dorsal to lateral processes of cervical vertebrae
-cranial to leading edge of shoulder
Semi-tendinosus/membranosus
-one hand’s width below tuber ischia
-one hand’s width above start of gastroc tendon
-outside thigh
Pectorals
-do not place too high d/t risk of septic mediastinitis if abscess developed cranially
What is endotoxin?
The heat-stable LPS component of gram negative bacterial cell walls
How is endotoxin generated?
Primarily during death of gram negative bacterial, as well as during the rapid multiplication phase
What is responsible for most of the deleterious effects of endotoxin?
The Lipid A structure
Describe the role of LPS-binding protein (LBP) in endotoxemia.
Endotoxin gains circulation and binds LBPs, which are acute phase proteins produced by hepatocytes. LBPs act as shuttle proteins bringing LPS from aggregates to responding cells, including intravascular macrophages (IVMs)
Which pro-inflammatory mediators are produced in endotoxemia’s MyD88 pathway activation?
TNF alpha, IL-1, IL-6
Describe the features associated with the hyperdynamic state of endotoxemia.
Overall vasoconstrictive stage Pulses - strong Temp - fever MM - injected, bright red CRT - normal Periphery - warm
Describe the features associated with the hypodynamic state of endotoxemia.
Overall vasodilatory stage
Pulses - weak, thready
Temp - normo to hypothermic
MM - congested (blue to purple), toxic line
CRT - prolonged
Periphery - cold (centrally localizing blood volume)
What is the theoretical expected leukogram in endotoxemic patients? What does the actual leukogram look like?
Theoretically: decreased tWBC, decreased neutrophils, lymphocytes WNL
Practically: tWBC and neutrophils WNL, lymphopenia
The difference is due to the cumulative effects of stress + endotoxemia.
Which component of the CBC is most telling in endotoxemic cases? What are the differentials for that parameter?
Lymphopenia
DDx: stress (not actually endotox!) or viral disease
What 2 tests can directly measure circulating endotoxin?
- Limulous amoebocyte lysate assay (research)
2. Etox Dx (horse-side test)
What are the 4 goals of treatment in endotoxemia cases?
- Removal of the cause
- Circulatory support
- Neutralization of circulating endotoxin
- Inhibition of synthesis and effects of endotoxin-induced mediators
What is involved in ‘removing the cause’ of endotoxemia?
Antimicrobials (TMS, gentamicin, amikacin)
Surgical removal of compromised and/or necrotic bowel
What is involved in ‘circulatory support’ for endotoxemia?
Goal: expansion of intravascular volume Hypertonic saline (7.2%) Hetastarch for protein loss
What is involved in ‘neutralization of circulating endotoxin’?
- Endoserum IV (currently out of favor)
2. Polymixin B IV (best choice)
What is involved in ‘inhibiting synthesis and effects of endotoxin-induced mediators?
- Flunixin meglumine - NSAID
- Pentoxyfylline (currently out of favor)
- DMSO - reduces edema
- Lidocaine - inhibits inflammatory mediators, improves GI motility
- Heparin - increases effect of ATIII (provided sufficient levels)
What complications are seen with endotoxemia? (4)
- Ileus and olic
- Laminitis
- Renal failure
- Thrombosis and DIC (associated with hypercoagulable state)
What are the 3 main pathologic components of DIC?
- Initiated by pathologic expression of intravascular tissue factor (TF)
- Induction of production of thrombin and consumption of coagulation inhibitors (AT III and protein C)
- Development of a hypercoagulable state
What 3 chemical parameters are indicative of DIC in the horse?
Which parameter is expected, but not seen in the horse?
Increased clotting times (PT)
Thrombocytopenia
Increased FDPs (3+)
*Hypofibrinogenemia expected, but not usually detected d/t methodology (‘normal’ low value is 0), and increased fibrinogen from inflammation associated with previous illness
How is DIC treated?
Heparin +/- ATIII as needed
What signalment is associated with laminitis?
> 1 year old
QH common - large frame, small feet
What primary conditions are associated with laminitis? (4)
- Sepsis
- Pars intermedia pituitary dysfunction
- Equine metabolic syndrome + insulin resistance
- Exogenous steroid administration
What are the two types of displacement seen in laminitis?
Rotational
Vertical (sinking)
What clinical findings are associated with laminitis?
- Palpation of digital pulses (symmetrical lateral/medial, with both front or all 4 feet affected)
- Elevated hoof temperature
- Swelling/edema of coronary band, depression may be palpated (indication of sinking)
- Pain at toe (detected by hoof testers)
How is laminitis staged?
No CS –> developmental
CS acute
CS >72 hours, no collapse –> subacute
CS + mechanical collapse –> chronic
How is laminitis managed?
Cryotherapy - ice baths up to 48 hours
Digital support - soft bedding, styrofoam insulation, rolled gauze over frog
What percentage of BW is normal blood volume?
8%
When would overhydration be utilized? (3)
- Liquefaction of respiratory secretions
- Intestinal impactions
- Renal dz
What parameters indicate MILD (5%) dehydration?
1-3 sec skin tent
mm moist to slightly tacky
CRT normal
HR normal (
What parameters indicate MODERATE (8%) dehydration?
3-5 sec skin tent mm tacky CRT 2-3 sec HR 40-60bpm *decreased arterial BP
What parameters indicate SEVERE (10-12%) dehydration?
>5 sec skin tent mm dry CRT >4 sec HR >60bpm *reduced jugular fill
What parameters indicate LIFE THREATENING (12-15%) dehydration?
HR >100bpm
Obvious sunken eyes and shock
*Death imminent at 15%
When is oral fluid administration contraindicated?
Reflux, gastric distension, ileus
What is the maximum flow capacity of a STAT IV set?
28 L/hr
What are the flow capacities of the following catheters?
14G
12G
10G
14G –> 13 L/hr
12G –> 25 L/hr
10G –> 35 L/hr
What materials are used in long term / short term catheters?
How long can short term catheters be left in?
Long term: polyurethane (least thrombogenic) / silicone
Short term: teflon / polyethylene
-maximum 72 hours
What fluid is given as an alkalinizing solution?
LRS
What fluid is given as an acidifying solution?
Normal saline (0.9%)
What fluid is akin to giving free water?
D5W (5% dextrose)
What fluids are given in cases of hypoproteinemia?
Dextran 70, Hetastarch
What fluid is given for immediate expansion of plasma volume?
How much is given?
What are the contraindications for its use?
Hypertonic saline (7.2%, 2400mOsm) 4-8L only, expansion of 10x the volume infused Contraindicated in: 1. uncontrolled hemorrhage 2. hyperNa 3. hypoK
What solution might be given to prolong the effects of hypertonic saline?
6% dextran 70
What are the general guidelines for fluid therapy?
D: % dehydration x BW (kg) = L of fluid (give in first hour)
O: L vomiting/diarrhea/reflux
M: 60 mL/KG/day or 30 mL/LB/day
(give 2x maintenance for overhydration)
What is the maximum shock dose of fluids that can be given?
60-90 ml/kg/hr
What is the maximum K+ IV administration?
What is the general guideline for supplementation?
No more than 0.5 mEq/kg/hr
Guideline 10-20 mEq/L for maintenance fluids
What are the guidelines for treating Na+ disturbances?
Acute disturbance (
What is the most common acid/base disturbance in the horse?
How is it treated?
Metaoblic acidosis
- Alkalinizing solution (LRS)
- Bicarb ONLY if HCO3
How is PCO2 related to pH?
For every 10 mmHg increase (from 40) in PCO2
there is a corresponding 0.05 decrease (from 7.4) in pH
What are the three pathways of muscular energy generation?
- Phosphocreatinine
- initial seconds of exercise only - Anaerobic glycolysis
- rapid production of small amounts of ATP
- occurs in cytoplasm - Aerobic
- occurs in mitochondria
- utilizes CHO and FFA
What is the pattern of muscle fiber recruitment?
I –> IIA –> IIAX –> IIX
What is the best assessment of performance in the horse?
VO2max (measure of O2 consumption)
=HR x SV x (a-v)O2
What heart sounds are heard in the horse and what do they correspond with?
S1 (lub) - closure of AV valves (mitral/tricuspid)
S2 (dub) - closure of semilunar valves (aortic/pulmonic)
S3 (ahh) - end of rapid filling phase
S4 (ba) - atrial contraction
Where is the PMI for each cardiac valve?
Mitral (left AV) - left 5th ICS, midway elbow to shoulder
Aortic (L semilunar) - left 4th ICS, below shoulder
Pulmonic (R semilunar) - left 3rd ICS, cranioventral to aortic PMI
Tricuspid (right AV) - right 3-4 ICS, midway elbow to shoulder
What is the most frequent manifestation of high vagal tone (physiologic) in the horse?
Second-degree AV block (Mobitz I)
-gradual increase in PR interval before beat is dropped
What is the most common pathologic arrhythmia?
What predisposes horses to this arrhythmia?
Atrial Fibrillation
- large atrial mass
- underlying vagal tone - asynchrony in atrial repolarization
What signalment and presentation is typical with atrial fibrillation?
Race horse Exercise intolerance (quitting at 3/4 post)
What are the two forms of atrial fibrillation?
- Paroxysmal: occurs during race and disappears with deceleration of HR
- Sustained
How is atrial fibrillation diagnosed?
- Auscultation of irregularly irregular rhythm
- Variable pulse strength
- ECG: f waves
- NORMAL echo
How is atrial fibrillation treated?
*Ensure normal K status
HR 60: digoxin –> quinidine
72 hrs: oral (preferred)
What etiologies are associated with ventricular tachycardia?
*Shocky animals
Myocarditis
Lytes/metabolic disturbances
Sepsis, endotox
How is ventricular tachycardia diagnosed?
ECG: QRS wide and bizzarre with >4 VPCs
How is ventricular tachycardia treated?
When is treatment indicated?
Indicated when arrhythmia seen at rest, or rate >120bpm
Lidocaine administered in small boluses
Which is the most common congenital cardiac defect in the foal?
Ventricular septal defect
What presentation is associated with mitral insufficiency?
Exercise intolerance
Weight loss
Respiratory distress
What are the etiologies associated with mitral insufficiency?
Degenerative /inflammatory changes of the valve
Bacterial endocarditis
How is mitral insufficiency diagnosed?
Auscultation of systolic murmur (left 5th ICS)
What presentation and signalment is associated with aortic insufficiency?
Generally asymptomatic
Older horses
How is aortic insufficiency diagnosed?
Auscultation of diastolic murmur (left 4th ICS)
What factors are pronostic for aortic insufficiency?
Size of aortic root (>8cm)
Presence of concurrent left AV valve insufficiency
What signalment is associated with vegetative endocarditis?
Describe the pathophysiology of valvular endocarditis.
High blood flow
Structural endothelial damage
Subclinical infection (pulmonary abscess)
Bacteria adhere to endothelial surface
Local release of thromboplastin activates coagulation
How is vegetative endocarditis diagnosed?
- CBC: hyperprotein, neutrophilia, anemia
- Blood culture
- ECG: arrhythmias secondary
- Echo: direct visualization of lesion
How is vegetative endocarditis treated?
Abx (K-pen IV, gentamicin)
-4-6 weeks minimum
Antiinflammatories (flunixin meglumine)
Asparin to decrease PLT aggregation
What follow-up procedures should be performed when treating vegetative endocarditis?
Serial ECG
Blood culture 60d after abx cessation (if patient was initially +)
What etiologies are associated with CHF?
Myocarditis
Ionophore toxicity
Endocarditis
Pericarditis
What clinical signs are associated with CHF?
Ventral edema
Poor pulses
Weakness/listlessness
Syncope
How is CHF treated?
Digoxin (+ inotrope)
Furosemide (diuretic)
Enalapril (ACEi)
What are the two classifications of pericarditis?
Effusive (idiopathic)
Constrictive (fibrinous)
How is pericarditis diagnosed?
ECG
How is pericarditis treated?
Effusive: pericardiocentesis / drainage
Constrictive: pericardiocentesis with lavage / pericardectomy
How is RBC regeneration assessed in the horse?
- BM aspirate
2. RDW (>19)
Which parameters are elevated in anemia of chronic disease (functional iron deficiency)?
What about true iron deficiency?
Functional
Serum ferritin + Marrow iron stores increased
True
TIBC increased
How is iron deficiency anemia treated?
True: iron cacodylate (parenteral)
Functional:
Treat inciting cause / underlying chronic dz
How is anemia associated with EPO treated?
Corticosteroids +/- transfusions
What are the two types of equine piroplasmosis/babesiosis?
Babesia caballi
- less severe
- extravascular hemolysis
Theleria/Babesia equi
- more severe
- intravascular hemolysis
- hemoglobinemia
- hemoglobinuria
How is babesiosis diagnosed?
Giemsa-stained blood smears
How is babesiosis treated?
Imidocarb diproprionate
- eliminates carrier state
- do not use in donkeys
What is the pathophysiology of equine infectious anemia?
Biting fly vectors
Lentivirus
Infects macrophages
Anemia is immune-mediated (no RBC infection)
What is the presentation of EIA?
Episodic disease
-recurrent fever, depression, icterus, weight loss
Extravascular hemolysis
Thrombocytopenia
How is EIA diagnosed?
Coggins test (>45 days of infection) ELISA (false positives)
What are the isolation requirements for EIA?
Minimum 200 yards from closest horse
What etiologies are associated with IMHA?
Idiopathic
Lymphosarcoma
Infectious: EIA, Clostridia, etc.
Drugs: penicillin, sulfas, phenylbutazones
What is the effect of blood loss on clin path parameters?
- Bleeding in first 4-6 hours: decreased TP
- PCV decrease not appreciated until 12-24 hours (48 hours to bottom out)
- 3-4 days post-hemorrhage: increased PCV
How is blood loss treated?
Volume replacement with crystalloids
10 L blood –> 40L crystalloids
