Flashcards in Shock1; articles cards 26-41 Deck (41)
Calculate volume needed for blood transfusion?
weight(kg)xDesired PCV−Recipient PCV
Then multiply that number ×70(cat)or90(dog)*
Note: A rough estimate is 2.2 ml of blood/kg of body weight increases the recipient's PCV by 1%.
FAST (Focused Assessment With Sonography for Trauma) Protocol to Detect Free Abdominal Fluid in Dogs
Uses two ultrasonographic views (transverse and longitudinal) for what four regions of the abdomen?
Also included is the conclusion made by Lisciandro jvecc 2009
2Midline position over the bladder
3Right flank in right and left lateral recumbency, caudal to ribs
4Left flank in left and right lateral recumbency, caudal to ribs
Lisciandro 09: Initial and serial AFAST (A=abdominal) with applied AFS (abdominal fluid scoring) allowed rapid, semiquantitative measure of free abdominal fluid in traumatized patients, was clinically associated with severity of injury, and reliably guided clinical management. Where possible, AFAST and AFS should be applied to the management of blunt trauma cases.
Shock dose for animal with severe pulmonary, cardiac, or renal dz?
one-quarter to one-half the calculated shock dose is administered over 15 to 30 minutes, and the patient is carefully reassessed for changes in vital signs.
Oxygen delivery equation? DO2 = ...
DO2 = CO x CaO2
results from inability of heart to propel blood through circulation; can be interference with diastolic filling or with the ability to pump (systolic failure). Also can be extracardiac like compression of heart or great vessels by some other pathology (sometimes referred to as obstructive shock as its own category)
inadequate circulating volume causing decreased preload, thus reduced CO
impairment of the mechanisms regulating vascular tone, with maldistribution of the vascular volume and massive systemic vasodilation. Decreased systemic vascular resistance causes "relative" hypovolemia and reduction in venous return. (ie sepsis, SIRS, anaphylactic reactions, or neurogenic shock caused by severe damage to CNS with loss of autonomic stimulation on vessels.
inadequate arterial oxygen content of cellular oxygen utilization. Most common causes are anemia (reduced hemoglobin concentration--anemic hypoxia), and hypoxemia associated with respiratory failure
Equation for cardiac output....CO = ...?
CO = SV x HR
3 factors that determine stroke volume (SV)?
preload, afterload, and contractility
Load imposed on a resting muscle to stretch it to a new length. Preload = End Diastolic Volume; An increase in End Diastolic Volume augments the strength of cardiac contractions (Frank-Starling mechanism). Factors that influence preload: splenic contraction, retention of Na and H2O, and increased thirst
The force that opposes muscle contraction, and in cardiac muscle, it is equivalent to the ventricular wall tension developed during systole. Afterload= "pressure in the left ventricle required to eject blood into systemic circulation"
Afterload is influence mainly by ___ ____ ____.
systemic vascular resistance. Low BP is the major determinant of decreased afterload.
the force and velocity of cardiac muscle contraction
Arterial Oxygen Content (CaO2) Equation?
CaO2 = Hb x SaO2 x 1.34 + PaO2 x 0.003*
Thus, oxygen content depends mainly on Hb concentration and oxygen saturation of Hb in arterial blood (SaO2; measured as %).
(*oxygen solubility coefficient)
SaO2 is the percentage of available hemoglobin that is bound to ____?
Hb affinity for oxygen increases as oxygen saturation of Hb increases. Thus the oxygen-hemoglobin dissociation curve, which relates Hb saturation of O2 to the partial pressure of O2 (PaO2), is a _______curve.
What are the 4 factors that influence Hb affinity for O2?
pH, temperature, 2,3-DPG (diphosphoglycerate), and CO2 that can cause a shift in the dissociation curve (ie - making O2 more or less readily released in tissues.
For a normal O2 tension of ___ to ___ mm Hg, the Hb saturation is 100%.
90-100 mm Hg
Describe whether an increase or decrease in each of the factors below causes the O2 disassociation curve to shift to the LEFT (ie. delivery of LESS Oxygen).
Shift to the LEFT
(ie. delivery of LESS Oxygen).
2,3 DPG: Decrease
(Note that pH is the only factor that causes a LEFT shift when it is INCREASED)
According to the American College of Surgeons hemorrhage classification system (Box 6-2), loss of ___________ % of circulating blood volume is able to trigger shock, and loss of more than ___________ % of circulating blood volume, if left untreated, induces irreversible shock.
30-40% triggers shock; 40% - irreversible shock
Catecholamine-resistant vasodilatory shock is characterized by refractory hypotension despite intravascular fluid resuscitation and catecholamine administration. Catecholamine-resistant vasodilation is caused by derangements of normal vasodilatory and vasoconstrictor mechanisms, and occurs despite increased levels of norepinephrine, endothelin, and angiotensin II. Author Silverstein (jvecc 2012) found that in dogs with vasodilatory shock that were nonresponsive to dopamine that this drug was effective at increasing blood pressure.
Silverstein found that exogenous
AVP can act as a potent vasoconstrictor in dogs with refractory vasodilatory shock.
AVP = Arginine Vasopressin, aka antidiuretic hormone.
What is AVP aka ADH? Made? Stored?
When is it normally released?
AVP is a potent vasoconstrictor peptide, synthesized in the hypothalamus and stored in the posterior pituitary. Normally, it is released into the circulation in response to an increase in the serum osmolality (sensed in the brain) or a reduction in plasma volume (sensed by baroreceptors in the left atrium, aortic arch, and carotid sinus)
MOA of AVP (arginine vasopressin)
The cellular effects of AVP are mediated by interactions
of the hormone with 2 principal types of receptors:
V1 and V2. V1 receptors, previously known
as V1a receptors, are predominantly located in the gastrointestinal tract and vascular smooth muscle, and
these receptors primarily mediate the vasoconstrictive
response to the hormone. In addition, when present in
high concentrations, AVP causes the HR-arterial pressure
baroreflex curve to shift leftwards by interacting
with V1 receptors in the brain. In contrast, V2 receptors
are primarily found in the principal cells of the
renal cortical and medullary collecting ducts, and these
receptors primarily mediate the antidiuretic effects of
the hormone. AVP also blunts the accelerated synthesis
of nitric oxide following LPS and IL-1b stimulation
in sepsis, and also reduces the vasodilatory effects of
nitric oxide, thereby preventing the nitric oxide-mediated
vasodilation that occurs in sepsis
What are the primary causes of inappropriate vasodilation?
Elevated levels of nitric oxide and activation of the smooth muscle ATP-sensitive potassium (KATP) channels
and calcium-regulated potassium channels (KCa2þ ) are the primary causes of the inappropriate vasodilation, but the lack of reflex vasoconstriction is not as
clearly understood. Other potential contributors to vasoplegia include fatal injuries to the vascular endothelial
cells from prolonged hypotension, inadequate oxygen extraction from the tissues, and an increase in the activity of vasodilatory prostaglandins.
In Silverstein's case series of 5 dogs with refractory vasodilatory hypotension that responded to AVP, what was the dose range that she used?
Starting dose: 0.5 mU/kg/min; Their doses were titrated up to maximum doses of 1 and 5 mU/kg/min, however the dog that
was given 5 mU/kg/min of AVP had shown an a positive response to 1.25 mU/kg/min until an acute episode of vomiting and aspiration occurred, after which the dog experienced respiratory arrest and needed the higher dose
Author Shih, jvecc 2010, evaluated the accuracy and precision of oscillometric noninvasive BP as a predictor of invasive direct BP in healthy, anesthetized, hypotensive and normotensive dogs. Prospective study, 8 dogs. Art lines used to measure direct BP. To make them hypotensive, dogs were maintained on iso while withdrawing ~ 40% of the animal’s blood volume until aMAP was stable at approximately 40mmHg. What was their conclusion?
The oscillimetric device was not reliably predictive of intra-arterial BP during hypotension associated with hemorrhage
Author Shih, jvecc 2010: Was the non-invasive BP more frequently falsely higher or lower than direct BP? Was this difference more substantial during hypotension or normotension?
NIBP more frequently read higher than direct BP.
NIBP device greatly overestimated BP measurements, particularily when hypotension was present. Some readings during hypotension (~18.7 %) had a bias of > 30%
Shih, jvecc 2010: The data generated in this study suggests that if a patient has an nSAP reading of 70mmHg, then 95% of simultaneously
collected dorsal pedal intra-arterial measurements would range from ___mm Hg to ___mm Hg.
40 to 110mmHg.