Physiology Flashcards
list the formulas for cardiac output
CO (cardiac output) = HR (heart rate) x SV (stroke volume) CO = blood pressure/peripheral vascular resistance
effects of loss of vascular tone and blood pressure on cardiac output
Distributive shock: Decrease in vascular tone leads to decreased blood pressure which initially increases cardiac output but because the venous return will be decreased (due to low blood pressure), the preload and therefore cardiac output will decrease leading to decreased perfusion
describe the clinical signs of uncompensated shock
Also called hypodynamic shock. If >15% blood is lost, compensatory mechanisms fail to maintain arterial blood pressure and perfusion of vital organs. Ischemic to brain and myocardium develops. To try to maintain blood pressure, tachycardia, tachypnea, poor peripheral pulses and cool extremities are present. Mild anxiety and sweating may be apparent due to sympathetic activity. Urine output and central venous pressure drop. As further blood is lost, vasoconstriction further reduces blood flow to tissues and ischaemia occurs. Lactate and CO2 build up leading to acidosis and cellular dysfunction.
what marks the onset of hydrodynamic shock
This is usually caused by severe blood loss (>15%).
in order to restore intravascualar volume what is the crystalloid replacement volume that must be administered
Fluid needed = percent blood volume (Liters/kg bodyweight x 100) x bodyweight Usually 7-9% bodyweight 35-45 L in a 500kg horse
What is maintenance fluid rate for a foal?
70-80ml/kg
List the 4 types of shock
Hypovolemic
Cardiogenic
Distributive
Obstructive
What is the magic percentage of blood loss, above which, shock becomes gradually uncompensated/clinical signs appear?
15%
List the clinical signs with 15-30% blood loss. And what class of shock is this?
Class II
Tachycardia
Tachypnea
Bounding pulses
Agitation
Pupil dilation
Sweating
Normal BP but perfusion deficits
Elevated lactate and anion gap metabolic acidosis
Which electrolytes do isotonic crystalloids contain?
Sodium
Chloride
Calcium
Potassium
Magnesium
What percentage of isotonic fluids given IV, diffuse into the intracellular/interstitial space?
80%
List the pro inflammatory and anti-inflammatory cytokines
Pro inflammatory:
TNF:
From neutrophils, NK cells
Coagulation, fibinolysis, complement activation, APR, neutrophil chemotaxis
Pyrogenic activities, augment cytokines production
IL-1:
From endothelial cells, fibroblasts, keratinocytes, lymphocytes
Coagulation, fibinolysis, complement activation, APR, neutrophil chemotaxis
Pyrogenic activities, augment cytokine production
IL-6:
From fibroblasts, keratinocytes, lymphocytes
Coagulation, fibinolysis, complement activation, APR, neutrophil chemotaxis
IL-8:
From endothelial cells
INF-y:
From NK cells
Anti-inflammatory:
IL-4
IL-10
IL-11
IL-13
TGF-B
TxA2, PGE, PGF2a, PGI2, Bradykinin, NO, angiotensin, endothelin, leukotrienes - state which are vasoconstrictors and which are vasodilators
Vasoconstrictors:
Angiotensin
Endothelia
TxA2
Leukotrienes
PGF2a
Vasodilators
Bradykinin
NO
PGI2
PGE2
What are the three components of endotoxin
O-antigenic region:
Outer polysaccharide
Monosaccharide core region
Lipid A
Toxic moiety
What is the gold standard for measuring endotoxin and what other methods are available
Limulus amebocyte lysate (LAL):
Gold standard for measuring endotoxin
Neutropenia with toxic neutrophil morphology(basophilic cytoplasm, vacuolization, Dohle bodies) and left shift:
Neutropenia can occur within 1 hr
Hyperglycemia
Hypovolemia:
Relative polycythemia
Hyperproteinemia
Azotemia
Metabolic acidosis
Increased anion gap
Lactic acidosis
Specific organ admage:
Azotemia
Increased creatine phosphokinase
Liver enzyme
Cardiac troponin
What are the options for treating endotoxemia
Diminish source:Treat underlying disease
Remove intestine
Tissue lavage
Caution with ABs, bactericidal actions, esp. B-lactams, may increase release of endotoxin
Smectite PO:
If cause GI
4 ounces orally BID
Absorbs bacteria and bacterial toxins
Bind and neutralize endotoxin:Anti-endotoxin antibiodies:
Endoserum (Hyperimmune sterum from horses vaccinated with Salmonella typhimurium)
Dilute 1:10/1:20 in LRS, administer IV over 1-2 hrs reduces hypersensitivity
Hyperimmune anti-core plasma to E.coli J5 (foals). 20-14ml/kg
Expensive, require freezer/refrigeration/thawing
Polymixin B:
Cationic antibiotic
Bactericidal at higher doses (nephrotoxic and neurotoxic)
Interacts with lipid A
Care in azotemic patients
1000-6000 IU/kg BID-TID
Fluid therapy
Anti-inflammatories:Flunixin:
Prevents endotoxin-induced prostanoid synthesis and associated clinical signs
0.25mg/kg IV q8hrs:
Low dose reduces potential side effects and effective inhibition of prostanoid synthesis without masking clinical signs
1.1mg/kg IV can be used
Ketoprofen - not evaluated
Phenylbutazone - not evaluated
Firocoxib - not evaluated
Inhibition of other mediators:
DMSO IV 0.1-1mg/kg diluted to 10% in isotonic fluid
Pentoxyfilline
Lidocaine
As percentages of bodyweight, what % of the body is made up of:
a) blood
b) ECF
c) ICF
d) TBW
a) blood 8%
b) ECF 20%
c) ICF 40%
d) TBW 60%
What makes up ECF
Interstitial fluid, plasma, lymph, transcellular fluids, synovial, pleural abdominal, CSF (can contribute to volume deficits in disease)
What is colloid oncotic pressure
Colloid oncotic pressure = osmotic pressure generated by proteins (albumin)
What is Starling’s law?
What is the normal pH
7.35-7.45
What 2 main mechanisms can be employed to correct pH
Alveolar ventilation modified within hours
Renal adaptation (increased HCO3 reabsorption; net acid secretion) 2-5 days to take maximal effect
Define the 4 primary acid-base disorders
Metabolic acidosis:
Decreased HCO3
Causes:
Lactic acid (poor perfusion)
HOC3 losses from diarrhea
Metabolic alkalosis:
Increased HCO3
Associated with disproportionate loss of chloride
Respiratory acidosis:
PCO2 increased
Alveolar hypoventilation
Respiratory alkalosis:
PCO2 decreased
What is the equation for anion gap
What is the difference between acidosis and academia
Acidosis/alkalosis = processes
Acidemia/alkalemia = pH of ECF
What is the difference between osmolarity and osmolality
Osmolality:
Concentraiton of osmotically active particles in solution per kg of solvent (mOsm/kg)
275-312 mOsm/kg (lower values in foals)
Osmolarity:
Number of particles of solute per liter of solvent (mOsm/L)
