Arterial concentration of O2. Total number of O2 molecules in arterial blood
Hypoxemia can be a result of (5)
1. hypoventilation
2. ventilation-perfusion mismatch
3. diffusion impairment
4. decreased O2 content of inspired air
5. intrapulmonary shunt
What disease can cause a reduction of global O2 deliver (4)
1. sepsis
2. sirs
3. anemia
4. acid-base imbalances
SaO2
oxygen saturation as measured by blood analysis
Arterial O2 dependent on
concentration of hemoglobin and degree of SaO2 of hemoglobin present
How is majority of arterial O2 delivered to tissue
bound to hemogobin
How is a small fraction of O2 delivered to tissue
Dissolved in plasma
O2 supplementation is indicated when
PaO2 ____
SaO2 ____
PaO2 < 70 mm Hg
SaO2 < 93% on room air
Why should O2 be humidified
Avoids drying and irritation of nasal mucosa and airways
Non-humidified O2 longer than several hours can cause (4)
1. drying of nasal mucosa
2. respiratory epithelial degeneration
3. impaired mucociliary clearance
4. increased risk of infection
What should O2 be bubbled through
Sterile H2O or saline
Non-invasive means of O2 delivery (2)
1. flow-by
2. face mask
How far should flow-by O2 be held from pt
2 cm
O2 flow-rate of 2-3 L/min produces and FiO2 of what with flow-by O2
25% - 40%
Tight fitting face mask creates an FiO2 of _____ at 8-12 L/min
50% - 60%
Risk with tight fitting face mask
Rebreathing of carbon dioxide. Should be periodically ventilated
What flow rate should be used with a loose fitting face mask
2-5 L/min
Invasive O2 supplementation methods (3)
1. nasal prongs
2. nasal or nasopharyngeal catheters
3. hyperbaric O2
How to measure nasal catheter
nose to level of lateral canthus of eye
How to measure nasopharyngeal catheter
Nose to ramus of mandible
Desired flow rate for nasal catheters and resulting FiO2
50-150 ml/kg/min
FiO2 30% - 70%
At what nasal flow rate do patients often experience discomfort?
>100 ml/kg/min
Hyperbaric O2
administers 100% O2 under supra-atmospheric pressure (>750 mm Hg)
Dissolved O2 can readily diffuse into damaged tissues without adequate circulation
How does hyperbaric O2 increase O2 in pts
Increases % of dissolved O2 in pt bloodstream by 10% - 20%
What injuries/conditions can hyperbaric chambers assist with? (7)
1. severe soft tissue lesions
2. burns
3. shearing injuries
4. infection
5. osteomyelitis
6. ruptured tympanum
7. pneumothorax
When does O2 toxicity occur
O2 >60% for longer than 24-72 hrs
Shock definition
inadequate cellular energy production
What is shock most commonly secondary to
Poor tissue perfusion
decrease O2 deliver compared to O2 consumption
DO2
O2 delivery
VO2
O2 consumption
3 leading causes of shock
decrease in DO2 secondary to:
1. hypovolemia - loss of IV volume
2. distributive - maldistribution of vascular volume
3. cardiogenic - failure of cardiac pump
4 major types of shock
1. obstructive
2. distributive
4. cardiogenic
5. hypovolemic
Hypovolemic shock
Decrease in circulating blood volume
common causes of hypovolemic shock (3)
1. hemorrhage
2. severe dehydration
3. trauma
Cardiogenic shock
decrease in forward flow from heart
common causes of cardiogenic shock (4)
1. CHF
2. arrhythmias
3. tamponade - pressure on heart from pericardial effusion
4. drug overdose
Distributive shock
decrease or increase in systemic vascular resistance or maldistribution of blood
common causes of distributive shock (3)
1. anaphylaxis
2. sepsis
3. neurogenic
Obstructive shock
caused by physical obstruction in blood flow
Common causes of obstructive shock (3)
1. GDV
2. pulmonary embolism - saddle thrombus
3. HW dz
What activates renin-angiotensin-aldosterone system
Decreased renal blood flow
What does the renin-angiotensin-aldosterone system do in brief terms
Reaction designed to regulate BP.
Upregulates SNS, causes NA and H2O retention via production of aldosterone and antidiuretic hormone
What is compensated shock
Increased IV volume, so initial signs of shock subtle
Initial signs of compensated shock (5)
1. Mild-mod depression
2. tachycardia with normal or >CRT
3. cool extremities
4. tachypnea
5. normal BP
Signs of decompensated shock (4)
1. pale mm
2. poor pulse quality
3. depressed mentation
4. decrease in BP
end result of untreated shock
decreased organ perfusion and organ failure, death
Signs of initial hyperdynamic phase of shock (4)
1. tachycardia
2. fever
3. bounding pulses
4. hyperemic mm secondary to cytokines (nitricoxide mediated peripheral vasodilation
What else is hyperdynamic shock called
vasodilatory shock
shock organs in dogs
GI tract
Shock in dogs often leads to what due to it's effects on the GI tract? (4)
1. ileus
2. diarrhea
3. hematochezia
4. melena
Hyperdynamic phase of shock is common in cats, true or false?
false, it's rare
what organ is vulnerable to damage with shock and sepsis in cats?
Lungs, signs of respiratory dysfunction common
Essential monitoring with shock (3)
1. EKG
2. BP
3. Pulse ox
What are often sign of successful return of cardiovascular stability in shock? (2)
Gradual reduction of tachycardia and normalization of BP
Best form of monitoring shock pt?
Thorough physical exam
Goal of shock treatment
Optimizing O2 delivery and tissue perfusion
Clinical signs of well-perfused pt (7)
1. CVP between 0-5 cm H2O
2. urine production of at least 1 ml/kg/hr
3. MAP between 70-120 mm Hg
4. normal body temp
5. normal HR/rhythm
6. normal RR
7. moist pink mm with CRT <2 sec
Why is monitoring lactate beneficial in shock pt?
Indices of system O2 transport and mixed venous O2 saturation
Hyperlactemia and acidemia are reflective of what?
Reflective of severity of cellular hypoxia
Normal lactate
<2.5 mmol/L
Severely elevated lactate
> 7 mmol/L
Lactate in neonatal and pediatric patients
may have higher levels
puppies 4 days old 1.07-6.59 mmol/L
10-28 days 0.80 - 4.6 mmol/L
Lactate samples with IDEXX analyzer (3)
1. serum should not be used
2. separate plasma within 5 mins
3. restraint and prolonged occlusion can increase
What is a good prediction of outcome with lactate?
change in lactate concentrations/responsiveness to therapy
PCWP
Pulmonary Capillary Wedge Pressure
indirect estimate of left atrial pressure (LAP)
R-sided cardiac catheter (PAC) allows for measurement of (4)
1. central venous and pulmonary artery pressure
2. mixed venous blood gases (PvO2, SvOs)
3. pulmonary capillary wedge pressure (PCWP)
4. CO
What other parameters of circulation and respiratory function can be derived from parameters supplied by PAC catheter? (9)
1. stroke volume
2. end-diastolic function
3. systemic vascular resistance index
4. pulmonary vascular resistance index
5. arterial O2 content
7. DO2 index
8. VO2 index
9. O2 extraction ration
CO and Do2 should be optimized until PCWP approaches what?
10-12 mmHg
High PCWP levels and what does it promote?
>15-20 mm HG
Promotes pulmonary edema and further impairs DO2
SvO2
mixed venous O2 saturation (superior and inferior vena cava)
ScvO2
Central venous O2 saturation
SvO2 and ScvO2
Refers to O2 content of blood that returns to heart after meeting tissue needs. Requires PAC or central venous catheter
If Vo2 constant, SvO2 determined by (3)
1. CO
2. hemoglobin concentration
3. SaO2
SvO2 decreased if (2)
1. Do2 decreased (low CO, hypoxia, anemia)
2. Vo2 increased (fever, sz)
SvO2 increased if (2)
1. hyperdynamic stages of sepsis
2. cytotoxic tissue hypoxia (cyanide poisoning)
Mainstay of therapy for shock
rapid administration of fluids to restore circulating volume and tissue perfusion (except cardiogenic)
Shock fluid dose
Up to 1 blood volume
k9 90 ml/kg
fel 50 ml/kg
IV fluids rapidly distribute to _____________ fluid compartment
extracellular
How quickly do fluids rapidly distribute to fluid compartment?
75% distributes to extracellular compartment after 30 mins
How should resuscitation be done with active hemorrhage?
Hypotensive resuscitation
hypotensive resuscitation
resuscitate slowly to MAP of 60 mm Hg to avoid worsening bleeding
Fluids with coexisting head trauma
0.9% NaCl - highest concentration of Na, least likely to contribute to cerebral edema
Excessive fluid administration signs (2)
1. pulmonary edema
2. peripheral edema
edema with excessive fluid administration caused by any combination of (3)
1. increased hydrostatic pressure
2. hypoalbuminemia
3. increase in vascular endothelial permeability
hydrostatic pressure
the pressure of the blood against the vessel wall. It is the opposing force to oncotic pressure
Additional fluid options for shock resuscitation (4)
1. synthetic colloid solutions
2. hypertonic saline
3. blood products
4. hemoglobin-based 02 carrying solutions (HBOC)
Synthetic colloids
Hyperoncotic
pull fluid into intravascular space
cause increase in blood volume greater than infused volume and help retain it in intravascular space
When are synthetic colloids used (2)
1. acute hypoproteinemia (TP <3.5 g/dL)
2. decreased colloid oncotic pressure
hyperoncotic
osmotic pressure exerted by colloids in solution
Dog dose synthetic colloids
10-20 ml/kg
cat dose synthetic colloids
prevalence of heart dz, use more conservatively
5-10 ml/kg
Why are synthetic colloids avoided
evidence in humans for contribution to acute renal injury, especially in critically ill and septic pt
no evidence in dogs and cats
Human albumin
natural hyperoncotic and hyperosmotic colloid solution
hypertonic saline
7%-7.5%
after administration, transient (<30 min) osmotic shift of H2O from extravascular to intravascular compartment
How is hypertonic saline administered
In small volumes over 10 mins
3-5 ml/kg
other actions of hypertonic saline (5)
1. decreased endothelial swelling
2. modulates inflammation
3. increased cardiac contractility
4. causes mild peripheral vasoconstriction
5. decreases intracranial pressure
How quickly are effects of hypertonic saline seen?
decreased HR and improved pulses within 1-2 mins
Why should hypertonic saline always be combined with other fluids? (2)
1. osmotic diuresis
2. rapid Na distribution
How long will plts survive in fresh whole blood
24 hrs
What is Do2 dependent on (2)
1. CO
2. systemic vascular resistance
Common vasopressors (3)
1. catecholamines
2. + inotropic agents
3. phenylephrine
Catecholamine drugs (3)
1. epi
2. norepi
3. dopamine
+ inotropic agents do what?
Increase force of ventricular contraction
Increase strength of cardia muscle contraction by increasing quantity of intracellular Ca for binding by muscle proteins and/or increasing sensitivity of increased contractile proteins to Ca
phenylephrine is what?
a sympathomimetic drug
Activates adrenergic receptors by increasing mediators of sympathoadrenal system levels (norepi and epi)
Adjunctive pressor agents (3)
1. vasopressin
2. corticosteroids
3. glucagon
cardiogenic shock
systolic or diastolic cardiac dysfunction
What hemodynamic abnormalities does cardiogenic shock result in? (6)
1. increase HR
2. decreased stroke volume
3. decreased CO
4. decreased BP
5. increased peripheral vascular resistance
6. increase in right atria, pulmonary arterial, and pulmonary capillary wedge pressures
What can help differentiate between causes of dyspnea in the cat?
hypothermia secondary to decreased perfusion (CHF)
what may excessive overhydration cause in shock? (2)
1. dilutional coagulopathy
2. pulmonary edema
What type of catheters have potential for increased damage to vessel walls?
Larger, rigid catheters
Common materials for catheters (4)
1. Teflon
2. Polypropylene
3. Polyurethane
4. Silicone
Less common IVC placement sites (3)
1. Dorsal common digital veins
2. Auricular veins
3. Lingual veins
What catheter placement sites may reach the heart faster?
IVC placed centrally or in the cephalic region
Movement of IVC within vein potentially causes what? (3)
1. Increased damage to vessel wall
2. Risk of thrombus formation
3. Phlebitis
Complications of surgical cut-down for IVC placement (6)
1. Perforation of vascular wall
2. Hematoma
3. Thrombosis
4. Venous transection
5. Infection
6. Cellulitis
Advantages of central venous catheter over peripheral catheter (4)
1. Longer dwell time
2. Safer administration of hyperosmolar solutions such as TPN
3. Measurement of CVP
4. Blood sampling
Why are certain catheters contraindicated in patients with head trauma or other CNS disturbances?
Jugular vein catheters contraindicated, occlusion for placement may increase intracranial pressure
Seldinger technique
Placing catheter over guide wire
Advantage of polyurethane catheters in central venous placement
They are antithrombic and last longer
What will thrombosis feel like around a catheter site
"Ropey" feel to vessel
Important thing to remember about parenteral nutrition connection
Parenteral nutrition lines should NEVER be disconnected to decrease the risk of infection
Ionized calcium levels should be / not be measured on heparanized samples
Not be
What vein closely approximates oxygenation of arterial blood, and how should sample be collected?
Sublingual veins in anesthetized patients, should be punctured with 25 gauge needle and 5 minutes of pressure should be applied after
Arterial catheter sites (5)
1. Dorsal metatarsal (dorsal pedal)
2. Radial
3. Coccygeal
4. Femoral
5. Auricular
What are the only things that should be injected into an arterial line? (2)
1. Heparanized flush
2. Sterile flush
Ischemic complications are more common in what species, and why?
Cats - they have poorer collateral circulation compared to dogs
Nosocomial infection:
Hospital-acquired
Risks linked to nosocomial infections (3):
1. Increased morbidity and mortality
2. lengthen hospital stays
3. added cost to pt. care
Types of IVC material (4) and preferred materials*:
1. Teflon*
2. Polyurethane*
3. polyvinyl chloride
4. polyethylene
*Per CDC - reduces risk of infection
Increased/Decreased IVC diameter increases risk of thrombi
Increased
What inactivates povidone-iodine
Alcohol
Topical antibiotic ointment Should/Should Not be applied to insertion site for IVC
should not
Thermoregulatory center
Hypothalmus
Why shouldn't topical antibiotic ointment be applied to insertion sites?
Promotes fungal growth
Encourages bacterial resistance
How often should insertion sites be cleaned and with what?
Cleaned with chlorhexidine and allowed to dry every time dressings are changed
Phlebitis
Inflammation of vessel
Signs of Phlebitis (4)
1. Redness around site
2. Heat
3. Swelling
4. Pain on palpation of site or when flushing IVC
Thrombosis
Thrombus formation at tip or along outer length of catheter.
Intravascular coagulation of blood in circulatory system
Signs of thrombosis (5)
1. Pain on palpation or when flushing IVC
2. Vessel feels hard or "ropey"
3. Vessel appears distended without being occluded
4. Edema above or below site
5. Becomes difficult to flush or aspirate
Thrombosis increases risk of what?
Pulmonary embolism
Why may generalized edema be present when administering IVF?
Due to compromise in vascular retention status due to low colloid osmotic pressure
PICC
Peripherally Inserted Central Catheter
Why should multiple attempts not be made to place IO catheter in same site?
Fluid may leak from hole if replacing or attempting multiple placements in same bone.
Increases risk of compartment syndrome
Compartment Syndrome IO catheter
Fluids extravasate from IO site over long period of time. Pocket is formed in muscle, can cause necrosis
What should be done with feeding tubes before feeding
Should be aspirated and checked for negative pressure
Gas aspirate back may be sign of line being in airway
Hypotension
Reduction in systemic arterial blood pressure
Why does hypotension develop
Results from disruption of normal cardiovascular homeostasis
Only develops secondary to dz that has negatively affected regulation
Systemic arterial blood pressure
Force exerted by blood against any unit area of the vessel wall
MAP
Mean Arterial Blood Pressure
What value plays biggest role in tissue perfusion (Systolic, Diastolic, MAP)
MAP
CO
Cardiac Output
SVR
Systemic Vascular Resistance
MAP is determined by what two functions
CO and SVR
Cardiac Output is function of
SV times HR
SV
Stroke Volume
Stroke Volume is
volume of blood ejected with each contraction of heart
HR
Heart Rate
Determinants of SV (3)
1. Preload
2. Contractility
3. Afterload
Preload
Stretching of ventricle before contraction - function of venous return
Contractility
Force of ventricular contraction
Afterload
Force needed to overcome aortic pressure and achieve L ventricular outflow
SV is directly related to
Preload and Contractility
SV is inversely related to
Afterload
HR is dictated by what
balance between SNS and PNS
SNS
sympathetic nervous system
PNS
Parasympathetic nervous system
Regulation of what is major factor in determining MAP?
Decreased SV = Increased/decreased HR in compensation
Increased
Clinical signs of cardiogenic shock
Consistent with global hypoperfusion
Change in mentation (depression, unresponsiveness, disorientation)
Cold peripheral extremeties
Pale MM
Increased CRT
Increased HR (Unless caused by bradyarrhythmia or pt moribund)
Should tachycardia be treated with antiarrhythmics
Malignant tachycardia due to tachyarrhythmia should be treated to improve CO
Therapy for compensatory tachycardia contraindicated, fix underlying cause
Compensatory respiratory Alkalosis/Acidosis can be seen in response to _________ with cardiogenic shock
alkalosis
lactic acidosis
Reasons why cardiac sounds may be difficult to auscult (3)
1. Pericardial effusion
2. Severe hypovolemia
3. Obesity
What will you auscult with CHF
inspiratory crackles secondary to pulmonary edema
Or lungs my be quiet ventrally due to pleural effusion
Venous blood gas often shows what with cardiogenic shock
Metabolic acidosis
Decreased cellular oxygen may cause anaerobic metabolism and lactic acidosis
Prerenal or renal azotemia may also contribute
Often see compensatory respiratory alkalosis
If there is concurrent pulmonary edema with cardiogenic shock, what may be increased on arterial blood gas
alveolar-arteriolar (A-a) gradient
EKG on cardiogenic shock may show
1. Sinus tachycardia
2. bradyarrhythmias (AV block)
3. tachyarrhythmias (a-fib, v-fib)
CHF CXR will show
1. Enlarge pulmonary veins
2. Alveolar or interstitial pattern in perihilar region (K9s)
3. Infiltrates often patchy or diffuse in felines
4. pleural effusion
Why can pulmonary arterial catheters help with diagnosis of cardiogenic shock
Decreased CO + Increase in preload parameters of central venous pressure, pulmonary arterial pressure, and pulmonary arterial occlusion pressure will be seen
Systolic dysfunction
Decrease in cardiac contractility or decrease in flow through left ventricular outflow tract (mechanical failure)
Common causes of failure of contractility with systolic dysfunction (4)
1. DCM
2. Sepsis
3. Endomyocarditis
4. Myocardial infarction
Most common cause of cardiogenic shock from systolic dysfunction
DCM
Breeds commonly affected by DCM (5)
1. Dobermann
2. Boxer
3. Great Dane
4. Labs
5. American Cocker Spaniel
What is DCM
Progressive decrease in myocardial contractility over months or years.
Activation of renin-angiotensin system and SNS in compensation, renal retention of Na and H2O,