CVT Critical Care Flashcards
What is Virchow’s Triad?
endothelial damage, alterations in blood flow, hypercoagulability
What occurs with arterial thrombosis?
High shear = Large # platelets, held by fibrin strans (Tx: Inhibit further arterial thrombogenesis)
What occurs with venous thrombosis?
Low shear = Fibrin and RBCs (Tx: Anti-coagulants)
What is the MOA of Aspirin?
irreversible acetylation of platelet COX site = decreased TxA2 synthesis ? TxA2 (produced by activated platelets) ? platelet aggregation and stimulates activity of new platelets via increased GPIIb/IIIa expression on platelet membranes
? Permanent effects lasting the lifetime of platelets (7-10days)
What is the MOA of clopidogrel?
? Thienopyridines: ADP receptor antagonists
? Irreversible inhibition of ADP binding to specific ADP receptors (P2Y12) on platelet membranes
? Impairs platelet release reaction and ADP-mediated activation of GPIIb/IIIa
What is the MOA of Fibrinogen receptor antagonists?
? Glycoprotein GPIIb/IIIa Blockers: fibrinogen receptor antagonists
? Abciximab (monoclonal Ab that binds to receptor) and eptifibatide (competitive memetic of fibrinogen)
? Abciximab + aspirin in cats = decreased thrombus formation compared to aspirin alone
? Eptifibatide causes circulatory failure and death in cats = BAD
? Activation of GPIIb/IIIa final common pathway of platelet aggregation (regardless of the initiating stimuli)
? Inhibit fibrin binding to GPIIb/IIIa
What is the goal of an anticoagulant?
Inhibit generation of fibrin
What is the MOA of warfarin?
Coumadin ? Vitamin K antagonist altering synthesis of K-dependent coagulation factors (II, VII, IX, X, protein C and S
? Interferes with hepatic reductase activity = impaired post translational carboxylation
? Delayed anticoagulant activity (4-5 days)
? Inactive clotting factors replacing previous functional counterparts
? Rapid inhibition of protein C and S = transient period of hypercoagulability in humans (not documented in vet med)
How do you measure warfarin tx?
Measure PT and calculate INR (International Normalized Ratio)
Goal: INR = 2-3
Why do you need to administer heparin when starting warfarin?
With rapid inhibition of Protein C and protein S = hypercoagulbility but other vit k dependent coag factors not affected for 4-5 days - thus heparin to prevent hypercoagulability that may be seen
Which 2 factors are most responsive to inhibition by antithrombin?
Iia (thrombin) and Xa
How does heparin bind to antithrombin?
Via high affinity pentasaccharide sequence
What is unfractionated heparin?
Glycoaminoglycan that binds to antithrombin and then bind to inactivate factor Xa and about 1/3 are able to bind to and inactivate thrombin (Iia)
What are the effects of unfractionated heparin and how are they monitored?
Unpredictable effect! Binds to plasma proteins Check PTT (1.5-2.5X baseline PTT)
What is low molecular weight heparin?
Depolymerization of unfractionated heparin = Smaller
100% binds to antithrombin and that binds to and inactivates factor Xa (DOES NOT bind to thrombin)
What are the effects of low molecular weight heparin and how are they monitored?
More predictable
Check with Anti-Xa levels
Name the 5 types of shock.
? Hypovolemic: decreased circulating blood volume
? Hemorrhage, dehydration, trauma
? Can include ?relative hypovolemia? = GDV, tamponade
? Cardiogenic: decreased forward flow
? Congestive heart failure, arrhythmias, tamponade, drug OD
? Distributive: loss of systemic vascular resistance
? Sepsis, obstruction, anaphylaxis
? Metabolic: deranged cellular metabolism
? Hypoglycemia, cyanide, mitochondrial dysfunction, cytopathic hypoxia of sepsis
? Hypoxemic: decreased O2 content in arterial blood
? Anemia, severe pulmonary disease, CO toxicity, methemoglobinemia
What are considered to be the 3 stages of shock?
Compensatory, Early Decompensatory, Late Decompensatory
Why do some cats in shock present with respiratory dysfunction?
The lungs are the shock organ in the cat
What is SvO2?
Mixed venous O2 saturation = Assessmen of global tissue oxygenation
What is ideal to maintain SvO2 (from jug cath)?
About 70%
How do hypertonic solutions work?
? Hypertonic Solutions: 7% NaCl: osmotic shift of water from extracellular to intracellular
? Transient volume expansion (<30 mintes), follow with crystalloids
? 5ml/kg over 5-10 minutes
? ?endothelial swelling, ?cardiac contractility, mild peripheral vasodilation, ?ICP
What are the labile coag factors that are not present in FFP?
Factor V, VIII, vWB (also no platelets)
What is the MOA of epinephrine?
? Potent pressor: mixed a/b activity
? Beta effects are variable between patients, but more potent compared to norepi
? May impair splanchnic blood flow = strong vasoconstriction in regional vasculature
? Inhibits mast cell and basophil degranulation= good for anaphylaxis
What is the MOA of norepinephrine?
? Mixed alpha and beta receptor agonist, preferential alpha effects
? Mild increase in HR/contractility and better pressor effects in those with normal CO
? Sepsis = cardiac insufficiency and vasodilation = diminished cardio effects of norepi
? In combo with dobutamine (potent b) to avoid increasing afterload in the face of diseased myocardium
? in combo with Dopa/Dobutamine may ?urine output and creatinine clearance
? Renal blood flow may improve when arterial BP normalizes
? Hypovolemia = norepi causes deleterious renal vasoconstriction
? Enhanced splanchnic DO2
What pressor can result in seizures in cats?
Dobutamine
What is the MOA of vassopressin?
On vascular smooth m via V1 receptors
What is the best time to use vasopressin?
During the late stages of shock since you have depleted your endogenous stores in hypothalamus = Esp in patients that are vasodilated and not responding to catecholamines = Enhances sensitivity to catecholamines
What is relative adrenal insufficiency?
Adrenal insufficiency of critical illness (decreased glucocortcoid synthesis or peripheral resistance to glucocorticoids) = Leading to refractory hypotension
Name a pure mu agonist.
Fentanyl, hydromorphone, morphine
How is remifentayl metabolized?
BY plasma esterases
Name a partial mu agonist.
Buprenorphone
Name a kappa agonist and mu antagonist.
Butorphanol
What drug can be used to reverse opiods?
Naloxone
Which opiod can result in hyperthermia in cats?
Hydromorphone
Which drug can be used to reverse alpha-2 agonists?
Atipamezole
What is the MOA of ketamine?
NMDA antagonist - Blocks wind up and central sensitization
What is the MOA of tramadol?
Weak mu opioid and noepi/serotonin reupatke inhibitor
What channel can be over expressed in chronically inflammed tissue (esp nervous tissue)?
Na+ channel - May consider lidocaine (Na+ channel blocker)
In critically ill patients what is the problem with over feeding (over RER)?
GI intolerance, hepatic dysfunction, increased CO2 production
What is the equation for calculating RER?
? >25 kg: RER= 70x(BW in kg) 0.75
? 3-25 kg: RER = (30xBW in kg) +70
Which drugs can be given through an endotracheal tube?
naloxone, atropine, vasopressin, lidocaine, epinephrine ? NEVER Na bicarb, norepi, calcium salts, isoproterenol
2x IV dose, diluted in 5-10 mls saline, followed by saline flush
What should be administered if KCL bolused!?
Calcium gluconate
What determines cerebral perfusion?
CPP = MAP - ICP
When is it most concerning for compromised cerebral blood flow?
When autoregulation mechanisms may not be working after traumatic brain injury = more susceptible to ischemia when MAP falls
What is the Cushing’s reflex with increased ICP?
? Systemic hypertension with bradycardia
? Increased ICP = acute drop in CPP = dramatic increase in sympa tone = systemic vasoconstritction and increased CO = significant increase in MAP
Baroreceptors in aorta/carotid sinus trigger reflex bradycardia
What system is used to assess neurologic status after traumatic brain injury?
Modified Glasgow Coma Scale
What happens to ICP during hypoventilation?
? Hypoventilation = hypercapnia can cause significantly increased ICP
What happens to ICP during hyperventilation?
Hypocapnia can cause cerebral vasoconstriction and decrease CBF
Why is a CRI of mannitol not recommended in traumatic brain injury?
? Increases permeability of BBB, when mannitol present for prolonged periods it can cross into cerebral parenchyma and worsen edema
What is the incidence of seizures after traumatic brain injury?
54% post trauma (can be immediate, early, or late)
What has been correlated with outsome in SA with traumatic brain injury?
Modified Glasglow Coma Scale
How is dehydration named in the body?
Based on the fluid that is left in the body
In metabolic acidosis, when the HCO3- drops what do cats do with pCO2?
NO change in pCO2 when HCO3- drops in cats
What is the equation for anion gap?
(Na + K) - (HCO3 + CL)
What is the equation for Aa gradient?
A/a = 150 ? 1.25(pCO2) ? pO2
Normal values usually less than 15
Increased (>25 mmHg)in pulmonary disease (V/Q mismatch, right to left shunt)
What is hetastarch made up of?
Hydroxyethyl starch
What is a potential complication with hetastarch?
Coagulopathies: Affect vWF and Factor VIII
Which hydroxyethyl starch can be used that has a reduced risk of coagulopathy and prolonged half life?
Voluven
What effects may hydroxyethyl starch have on endothelial surface?
HES may also down-regulate endothelial surface adhesion molecules (decreasing inflammation, endothelial injury, and leukocyte migration into the interstitium)
HES may be able to reverse changes in microvascular premeability secondary to free radical damage in reperfusion injury
In general, the use of a colloid will typically allow for what reduction in the amount of crystalloids that are used?
About a 40-60% reduction
What is the COP of whole blood?
About 20 mmHg
What is the COP of frozen plasma?
About 20 mmHg
What is the COP of 25% Human albumin?
About 200 mmHg
What is the COP of hetastarch?
About 30 mmHg
What is the term when large volumes of fluid increase the abdominal pressure?
Adbominal compartment syndrome
Which small dog breed is over-represented for GDV?
Dachshunds
What are 3 prognostic indicators for GDV?
? Lactate>6 mmol/L
? Gastric Resection
? Splenectomy
What is the diagnostic of choice for GDV?
Right lateral rad = ? pylorus is gas-filled and located cranial and dorsal to the fundus
? Compartmentalization line between pylorus and fundus, where their walls contact one another
What is the mortality rate of GDV that are surgically managed?
About 15-18%, but increased if gastric resection, splenectomy, or arrhythmias at presentation
What organism causes about 50-60% of osteomyelitis in fracture cases?
Staphylococcus = Think cefazolin or fluoroquinolone if Gram -
What is the shock triad in cats?
Hypotension - Bradycardia- Hypothermia
At what level is the COP considered to be clincially significant?
Less than 14 mHg
What machine is used to measure colloid osmotic pressure?
Colloid osmometry
