Exam 3: Lecture 24 - CV Support Drugs & Basic CPR Flashcards
___ is a major anesthetic complication
Hypotension
-Reported in 20-30% of dogs and cats having elective procedures, but probably occurs more often
Where do you want to keep the MAP and SAP?
-Keep MAP > 60-70 mmHg
-SAP > 80-90 mmHg
What are common causes of CV depression during anesthesia?
- Drugs
- Equipment malfunction/misuse
- Shock/sepsis
- Hypovolemia
- Mechanical ventilation
- Surgical procedure
- Pre-existing CV disease
- Metabolic disease
What is the key with CV depression during anesthesia?
-Key is to treat the underlying cause of hypotension
What does MAP encompass?
-Heart rate
-Stroke volume
-Systemic vascular resistance
CO =
HR x SV
What is cardiac output (CO)?
Volume heart is pumping out in L/min
Map = (about)
CO x SV
What big picture thing so we care about with CV support?
-Oxygen delivery to the tissues
What are the mechanisms to managing hypotension?
-Adjustment to current anesthetic management
-Fluids
-Anticholinergics
-Vasopressors
-Positive inotropes
What are cardiovascular support drugs?
-Positive inotropes
-Vasopressors
The cardiovascular support drugs (positive inotropes & vasopressors) act as ____ and what does that mean?
-Act as sympathomimetics
-Means mimic the sympathetic side of the nervous system (increasing contractility or squeezing of peripheral vasculature)
What are sympathomimetics?
-Includes endogenous catecholamines (ex: epinephrine, NE, dopamine), synthetic catecholamines (dobutamine), and synthetic non-catecholamines (phenylephrine)
Relative selectivity of sympathomimetics for various adrenergic receptors depends on
-The chemical structure of the drug
-They act on a- adrenergic, b-adrenergic, or dopaminergic receptors directly or indirectly & these receptors are coupled to G protein
-The density of a & b-adrenergic receptors in tissue determines the response of the drug
What to you need to understand in order to understand what the CV support drugs do?
-Understand the receptors they work on and what organ systems they have their effect on
Where are alpha-1 receptors located and what is their action?
-Located: vascular smooth m.
-Action: increase vascular smooth m. contraction
Where are alpha-2 receptors located and what is their action?
-Located: CNS
-Action: Decrease sympathetic outflow
Where are beta-1 receptors located and what is their action?
-Located: Cardiac cells
-Action: Increase heart rate, increase contractility, increase renin release
Where are beta-2 receptors located and what is their action?
-Located: Vascular & bronchiolar smooth m.
-Action: Vasodilation, bronchodiation
Where are D-1 receptors located and what is their action?
-Located: Renal, splanchnic, coronary, cerebral
-Action: Relaxes renal vasculature smooth m.
What does Dobutamine act on & cause?
-Mostly beta-1
-positive inotropic effects leading to dose-dependent increase in myocardial contractility, SV, & CO
How is Dobutamine typically administered for hypotension?
-Typical CRI dose used for treatment of hypotension in small animals
What is important about CRI’s?
-Cannot just pull it out of the bottle & use it!
What is Dopamine and how does it work?
-Endogenous catecholamine that is precursor to norepinephrine
-Acts directly & indirectly on both alpha and beta-1 receptors
-Also as dopaminergic (D1, D2) effects
-Increases CO; modest increase in HR, BP, & SVR
What are the indications for using Dopamine?
-Treatment of acute heart failure, severe hypotension or shock
What effects are seen with lower doses of Dopamine?
-At lower doses, D1 & D2 effects include dilation of renal, mesenteric, coronary, and intercerebral vascular beds
What effects are seen with higher doses of Dopamine?
-At higher doses, there is an increase systemic peripheral resistance due to mainly alpha 1 receptor effects
Dopamine should begin to work within
5 minutes
What is Ephedrine and how is it used?
-Mixed inotropic-pressor agonist at a1, a2, b1 and b2 receptors
-Commonly used for management of hypotension during general anesthesia in horses b/c can be given as bolus instead of CRI (due to longer duration of action compared to other CV support drugs)
What species is Ephedrine typically used in?
-Horses
How does Norepinephrine work?
Agonist at the a1, a2, b1 receptors
-Equal in potency to epinephrine for stimulation of b1, but little effect on b2
-Potent a-agonist that produces intense arterial & venous vasoconstriction in all vascular beds
-Tends to decrease CO & may cause metabolic acidosis
What can happen with Norepinephrine?
-Necrosis if extravasation occurs
How is Norepinephrine typically administered?
-Mainly used as CRI for treatment of refractory hypotension due to vasodilation from inhalant anesthesia or sepsis b/c effects are mostly on a1 receptor at the clinically used dose rate
How does Epinephrine work?
Has both vasopressor & inotropic effects by directly stimulating a1, b1, and b2 receptors & is most potent activator of a-adrenergic receptors
-a1: intense vasoconstriction (of periphery; skin, mucosa etc.)
-b1 effects: increase SAP, HR, CO
-b2 effects: modest decrease in DAP due to vasodilation in skeletal m., bronchodilatio
What is the net effect of Epinephrine?
-Increase in pulse pressure & minimal change in MAP
-Preferential distribution of CO to skeletal m. & decreased SCR
-Renal blood flow decreases, but coronary blood flow increases
-Secretion of renin due to b stimulation in the kidneys
How is Epinephrine given?
-Typically reserved for use as a bolus during CPR
-Can be given as a CRI as a last resort for treatment of severe hypotension due to endotoxemia
What is Phenylephrine and how does it work?
-Increases peripheral vascular resistance by agonist effects on the a1 receptors & can be used in patients w/ severe vasodilation (e.g. due to septic shock)
When should Phenylephrine be avoided?
-Generally recommended to avoid the use of phenylephrine to pregnant patients as it decreases blood flow to the uterus & therefore impairs oxygen delivery to the fetus
How does Vasopressin work?
Works through stimulation of V1 receptor located on vascular smooth m.
-Unique feature of V1 receptors is ability to remain responsive during periods of acidosis (unlike a1 receptors)
-Has no inotropi or chronotropic effects
What patients is Vasopressin indicated in?
-For vasodilatory hypotension due to sepsis, prolonged hemorrhagic shock, or cardiac arrest
How is Vasopressin given?
During CPR, vasopressin boluses can be substituted for epinephrine
-Can do CRI dose for vasodilatory shock due to sepsis ranges from 0.5-2.0 mU/kg/min in dogs
How do you get a CRI to use?
-Have to make it yourself
What are the (basic) steps for making a CRI?
-Has to be diluted
-Know what drugs it is compatible with
-Come up with dose and can either have a way to deliver them, or can have them free drip
-Don’t mix up too far in advance for a case b/c only good for 24 hours once mixed
____ are 5x more likely to survive to hospital discharge after CPR than ____
Cats than dogs
Anesthetic related CPA events are almost ____ more likely to be discharged compared to other groups
15x
What are the RECOVER guidelines?
-Reassessment Campaign on Veterinary Resuscitation
Goals:
-Review of literature
-Develop consensus on CPR guidelines
-Provide education & training for veterinary medical care team
What is the “chain of survival” when talking about CPR?
-Prevention/early recognition
-Basic life support (BLS)
-Advanced life support (ALS)
-Post Resuscitation Care (aka post cardiac arrest care)
What are the signs of cardiopulmonary arrest?
-Not responsive
-Not breathing
-No pulse detected
What are the 3 components of BLS?
(BLS = Basic Life Support)
1. Shake & shout (i.e. provide stimulation)
2. If not breathing/responsive, immediately start chest compressions @ 100-120 per min. & depth of 1/3 to 1/2 chest width. Do not stop to check pulse for 2 minutes!
3. Establish airway & ventilate at 10 bpm (i.e. give breath every 6 seconds)
T/F there is a CPR app
TRUE! There is a recover CPR app
What does the RECOVER CPR app provide?
-Free to download & use
-Serves as metronome to guide compression & ventilation timing
-Keeps track of 2-minute cycles
-Records all drugs given
-A PDF record can be sent afterwards
What is the position of the patient for chest compressions?
-Lateral recumbency
What is the position of the compressor for chest compressions?
-Stand behind the patient (along the spine)
What is the hand position for the compressor for chest compressions?
-Hand over hand, interlaced fingers
What is the compressor stance for chest compressions?
-Shoulders over elbows/hands, lock elbows, bend at the waist
What are some ways we can make chest compressions easier for the compressor?
-Use a stool if needed
-Can put patient on the floor
-Or you can get on the table
What are the patient chest types?
A. Large, round chest
B. Large, keel chest
C. Wide-chest (e.g. Bulldogs)
D. Cats & small dog breeds
How do chest compressions change when you have a wide-chested dog like a Bulldog?
-Dorsal recumbency
-Compress to 25% depth
How does the hand position change when you have a cat or small dog breed?
-Circumferential
-One-handed palm
-One-handed thumb-to-fingers
What airways & ventilation can we use during CPR?
-Ideally intubated w/ appropriately sized ET tube w/ cuff inflated & tube secured in place
-Alternatively, use tight-fitting mask & self-inflating bag to deliver breaths
-Use of 100% O2 reasonable
-If not able to intubate, can go mouth-to-snout (if no concern for infectious disease or narcotic exposure) using ratio of 30 compressions to 2 ventilation technique
What is an example of a manual resuscitator we can use during CPR?
-Ambu bag
What should we do during the 2-minute cycle of compressions & ventilation (first 2 most important)
- Hook up ECG leads
- Place capnograph (ETCO2) at the end of the ETT
- Gain IV access
-IO would be 2nd choice
-Some drugs can go IT if no other access available (inter-trachially) - Administer reversal agents if indicated
-NO cardiac sticks!
How should the “pause and check” phase of CPR be completed?
-Take no more than 10 seconds to stop compressions long enough to feel for femoral pulse & team assesses hooked up ECG
-If a pulse -> ROSC
-If no pulse: evaluate ECG to determine if shockable or non-shockable rhythm, evaluate ETCO2 (if <18 mmHg, evaluate quality of compressions)
