Exam 1 Flashcards
What are the five components of general anesthesia
- Unconsciousness
- Muscle Relaxation and immobility
- Amnesia- can’t remember anything
- Attenuation of autonomic reflexes- keeps sympathetic NS from being activated
- Analgesia- relieving pain before it even happens
What are the risk factors for general anesthesia
old age, high ASA status, urgent/emergent procedure, procedure preformed at night, very small size, endotracheal intubation in cats (don’t over inflate cuff), pulse ox not used
What are the risk factors and risk of general anesthesia
Anesthetic drugs have the smallest therapeutic index of any drugs we use, dogs have a 0.17% chance of dying under anesthesia, cats have 0.24%, horses if healthy have a 1% if unhealthy have a 2% chance, and rabbits have a 0.73% chance of death if healthy and if sick a 7.37% chance of death
Patients can die from overdoses, cardiovascular or respiratory complications, or other reasons like anaphylaxis or aspiration
Describe the American Association of Anesthesiologist (ASA) classification
ASA 1- normal healthy patient, elective procedure
ASA 2- patient with mild systemic disease (like dental disease)
ASA 3- Patient with severe systemic disease (diabetes or cushings)
ASA 4- Patients with severe systemic disease that is a constant threat to life (ex. HCM or pneumothorax)
ASA 5- moribund patients not expected to survive one day with or without operation
What are the components of a patient pre-anesthetic assessment
Identification of the animal
Signalment- age, breed, species, sex
Body weight in kilograms
History
physical exam
What are the minimum components of pre-anesthetic testing
Everyone should get a PCV/TS
If indicated minimum database (CBC, Chem, UA)- geriatric (achieved >70% of life expectancy) are always indicated
When should you do further diagnostics prior to anesthesia
If geriatric (minimum database) or if something found on physical (abnormal auscultation on respiratory or cardio, if needs parasite testing, if anything is concerning in history, etc.)
What are the appropriate fasting times for patients undergoing anesthesia
Healthy dogs and cats- 6 hours
Ruminants- 24 hours
Pigs- 12 hours
Horses- maybe 12 hours
Neonates and tiny creatures (<2kg)- 1-2 hours (hypoglycemia concern)
How do you prep a patient for anesthesia
Fast for appropriate about of time
Resolve and deficits or abnormalities- dehydration, electrolyte abnormalities, heart failure, anemia, respiratory distress
Supportive care- temp support, pre-oxygenate, place monitors to get first readings
Informed consent from owner
What does the circulation of blood depend on
A functional heart (pump)
Normal vasculature (pipe)
Adequate blood volume (fluid)
What is the function of the cardiopulmonary system
to maintain a constant internal environment for all cells
How do anesthetics usually impact the mechanical activity of the heart
by altering the electrical potential across membranes (affect Na, K, Ca, and Cl)
What is meant by excitability of cardiac cells
the intrinsic property they have to generate an action potential
What are the steps of an action potential for non-pacemaker cell
Phase 0- Rapid inward Na flux- depolarization
Phase 1- Transient outward K flux- initial repolarization
Phase 2- Large, slow inward Ca flux trigger Ca release and cell contraciton
Phase 3- Outward K flux- repolarization
Phase 4- resting
What are the steps of an action potential for a pacemaker cell
Phase 0- slow inward Na and Ca flux- slow depolarization
Phase 1- none
Phase 2- Large, slow inward Ca flux trigger Ca release and cell contraciton
Phase 3- Outward K flux- repolarization
Phase 4- slow inward Na flux- slow depolarization
What are all the pacemaker cells and which one usually sets the heart rate
SA and AV nodes, bundle of His, R and L branches, and Purkinje fibers
SA node usually sets heart rate because it has the most rapid rate of phase 4 (usually)
How does calcium cause a muscle contraction
it binds to troponin C which enables the actin to interact with the myosin and cause a muscle contraction
What makes up the distribution of total blood flow
Vessel rich group (brain, kidneys, heart, etc)- 75% of blood distribution
Muscle group
Fat group
vessel poor group
How do anesthetics interact with cardiovascular function and how can you minimize the effect
most of them depress CV function by causing hypotension, bradycardia, and decreased contractility
minimize by careful dosing and balanced anesthesia and ensuring adequate delivery of oxygen
What makes up your inspiratory capacity? How about the functional reserve capacity of your lungs
Inspiratory is your inspiratory reserve volume and your tidal volume
Functional reserve capacity is the expiratory reserve volume and residual volume
What makes up your vital capacity
The inspiratory and expiratory reverse volumes and tidal volume (excludes residual volume)
What makes up your upper airway and what is this considered
nasal passages, larynx, trachea, bronchi, bronchiole- it is the anatomic dead space
Inspiration has what kind of pressure and expiration has what
inspiration has slight negative intrathoracic pressure and expiration has slight positive pressure
Explain the two ends of the range of V/Q matching
V/Q= infinity means there is great ventilation but no perfusion
V/Q= 0 means there is no ventilation but good perfusion
What determines oxygens delivery to tissues
cardiac output and blood oxygen content (CaCO2) aka affinity of Hb for O2
What components make up CaO2 (blood oxygen content)
the oxygen bound to hemoglobin and the oxygen dissolved in plasma
Explain the benefits of hand monitoring and machine monitoring
Hand monitoring can be more subjective whereas something like a machine can give you exact numbers or show you exact problems (like an arrhythmia on an ECG)
Hand measuring with a doppler is actually more accurate than oscillometric
What is used to assess anesthetic depth
jaw tone (loose), eye position (central if light or deep, ventromedial if adequate), palpebral/corneal reflexes (absent if deep), rectal tone (absent if deep)
What are examples of subjective cardiovascular monitoring
Mucous membranes, capillary refill time, cardiac auscultation, pulse palpation
Describe the parts of the ECG
P wave- atrial depolarization
QRS- ventricular depolarization and contraction
T- repolarization of ventricle
Where do the ECG leads usually go on small animals
White- right forelimb
Black- left forelimb
Red- left hindlimb
Explain a sinus arrhythmia
The heart rate increases in inspiration and decreases in expiration- normal in dogs and horses
What is a 1st, 2nd, and 3rd degree AV block
1st- there is a prolonged P-R interval
2nd- occasional dropped QRS
3rd- no relationship between P and QRS- sinus node and ventricle not speaking, ventricle beats without a p wave
What does atrial fibrillation look like
F waves, high ventricular rate, irregular rhythm, no set p waves and random QRS
What does a ventricular premature complex (VPC) look like
wide and bizarre QRS with no p wave
What is systolic blood pressure
the peak pressure reached by arterial pulses
What does Pulse Ox measure
The percent of hemoglobin saturated with oxygen
What is the driving force for loading oxygen onto hemoglobin
The partial pressure of oxygen (PaO2)
What is hypoxemia in terms of PaO2
When PaO2 is less than 60mmHg, after this saturation rapidly falls
How does pulse oximetry work
it uses alternating red and infrared light to analyze pulsatile fluid (aka the blood in the arteries) to see how much the hemoglobin is saturated with oxygen
What are examples of subjective and objective monitoring for ventilation
Subjective- respiratory rate and depth
Objective- Capnography and blood gas analysis
Capnography is an indirect measurement of what
the patients cardiac output and metabolic rate
a decrease in CO2 means there is a decrease in cardiac output
Inadequate ventilation is represented as what on capnography
A high ETCO2 (hypercapnia), represents hypoventilation
Excessive ventilation is represented as what on capnography
A low ETCO2 (hypocapnia), represents hyperventilation
What is normal ETCO2 ventilation range
35-45mmHg
What corresponds to the end expiration on a capnogram
the beta angle
What is Phase I, II, III, and IV on an capnogram
I= inspiratory base line
II= expiratory upstroke
III= expiratory plateau
IV= Inspiratory downstroke
How does an increase in PaCo2 affect pH, and what causes it
it decreases pH, causes respiratory acidosis, caused by hypoventilation and hypoxemia
How do you manage respiratory acidosis during anesthesia
breath for the patient more effectively
What are the five causes of hypoxemia
alveolar hypoventilation, decreased inspired oxygen concentration, ventilation/perfusion mismatch, shunt, diffusion impairment
What are the 5 basic functions of anesthesia circuits
- Provide a source of oxygen
- Provide a means to support ventilation
- provide a means of delivering inhalant anesthetics
- provide a means to remove exhaled CO2
- Provide a means to remove inhalant anesthetics from work environment
How do you calculate how much volume (L) of O2 is in a oxygen cylinder
(Pressure on the gauge/1900)x660 (L-total voume)
At what pressure should you replace an oxygen tank
under 200 psig
T/F it is fine to leave an unchained oxygen tank sitting upright for a few minutes while you grab your anesthesia set up
False, you should never leave an oxygen tank in a position where it could be knocked over, even for a few seconds. If you much, leave the cylinder laying down on its side temporarily
What has a higher oxygen pressure a ceiling pipeline regulator or a cylinder regulator and why is this important?
The ceiling is higher at 50-55 psig (the cylinder regulator is 45 psig), this is because the gas will come from the source with the higher pressure and you want the ceiling to be able to override the cylinder as your main source of O2
How do you read the two different flow meter floats/balls
the float you read from the top of the bobbin and the ball you read at the middle of the ball
You accidentally filled an isoflurane vaporizer with sevoflurane and the vaporizer is set to 1.5%. If isoflurane pressure is 240 mmHg and sevoflurane is 160 mmhg, what concentration of sevoflurane will you have and what sort of anesthetic depth will the patient experience
240/160= 1.5 so for every 1 unit of iso you have 1.5 units of sevo
so 1.5%/1.5= 1% concentration (instead of 1.5%) so the patient will be lighter
What is the oxygen flush valve used for and when can you not use it
to rapidly decrease the inhalant concentration in the breathing circuit, the wake up button!
Don’t use in non-rebreathing circuits!! Can cause barotrauma
Compare and contrast the two types of breathing circuits
Rebreathing- a circle, takes longer for inhalant to get to patients but is cheaper and more environmentally friendly (uses less gas), the patients rebreathe the expired gas and the CO2 is chemically removed, there is less heat and moisture loss, larger volume to buffer from barotrauma, more resistance to breathing, requires absorbent to be changed, more places for gas to leak, pediatric circuit for patients 3-10 kgs and adult for patients >10kg
Non-rebreathing- works much faster but is more expensive, less resistance, removes expired gas from patients and uses high gas flow rates to remove CO2, increased loss of heat and moisture, increase risk of barotrauma, used for patients <3-5kg
What is the flow rate for a rebreathing circuit and a non-rebreathing
rebreathing 10-20 ml/kg/min
nonrebreathing 100-200ml/kg/min
How should you adjust your gas flow in anesthesia
at first you should have a higher flow because of the wash-in period (aka the time-constant- how long it takes to reach the % of inhalant in the system that the vaporizer is set to)
for maintenance there will be a lower flow
What is the time constant in anesthesia determined by and how many time constants does it take to result in a 95% change in the system
time constant (min)= volume/flow rate
it takes 3 time constants to change the system
What size bag should be used on the anesthesia circuit
5-6x the patient’s tidal volume= Vt
Vt= 10-20 ml/kg (lung volume) x respiratory rate
What are the components of supportive care while under anesthesia
Thermal support, padding and positioning, eye protection, management of oral secretions and regurgitation
What are the four mechanisms of heat loss and how is each one reduced
Radiation (most important)- Heat that is generated in the body is given off to the atmosphere- blankets and warmer surgical suite
Conduction- movement of heat away from the body to a surface it is in contact with- padding between the animal and the table
Convection- a fluid (air or water) flowing by the skin carries away heat “wind chill”- warm scrub/lavage fluids, no fans in operating room
Evaporation- evaporation of liquid promotes heat loss from the skin surface- only scrub areas that need to be scrubbed, keep patient as dry as possible, heat and moisture exchange devices on airway circuit
What are the adverse effects of hypothermia
prolonged recovery, increased infection rates, decreased anesthetic requirements (easier to overdose), discomfort, increased blood viscosity, arrhythmias and cardiac arrest
How do you protect a patient from musculoskeletal damage
Use ample padding, avoid extreme flexion or extension of the legs (place joints in a natural position if possible)
in large animals pull dependent (one that is down) limb cranially to avoid radial nerve damage
How do you protect a patient from corneal damage
eye lube, closing eyelids if possible, and taping the eyes shut
How do you protect a patient from regurgitation and aspiration
Inflate cuff appropriately, recheck tube placement and cuff frequently, keep head tipped down, have supplies for suctioning
Examine oral cavity and pharynx prior to extubation
Ruminants- continue to produce saliva so pharynx should be elevated to saliva goes forward and out of the mouth and oral cavity should be suctioned periodically if possible
Can give antacids to make reflux less acidic or meds like metoclopromide or cisapride to decrease incidence or if regurgitation occurs in an animal try to lavage the esophagus
What is the ASA guidelines recommended fluid rate for dogs and cats under anesthesia
Healthy dogs- 5ml/kg/hr
Healthy cats- 3 ml/kg/hr
adjust rate based on needs
What are the 3 types of fluids used under anesthesia and what are they used for
Replacement solutions (isotonic)- used to manage and replace ongoing losses
Hypertonic solutions- expands plasma volume by pulling fluid from interstitial space- rapidly resuscitates patients in shock, relieves intracranial pressure
Colloids- pulls fluids from vasculature to increase circulating volume, helpful in hypoalbuminemic patients, natural (blood products) and synthetic types
Acute vs. chronic pain
actue- the result of traumatic, surgical, or infectious event that begins abruptly and is brief, physiologic
chronic- persists beyond the usual course and beyond the time to heal for months or years, pathologic, ex. osteoarthritis, cancer pain, neuropathic, phantom limb pain
What are the five steps in the pain pathway
Transduction- up first order neuron–> transmission–> modulation (in spinal cord)- up second order neuron–> projection–> perception
Explain modulation
the process by which nociceptive information is augmented or inhibited
Where central sensitization takes place and why rubbing the area after injuring it helps relieve pain (gate control theory- activating A-beta fibers to overcome the activated A-delta fiber stimulus)
explain wind-up
sensitization of second order neurons (in the spinal cord) due to high intensity or prolonged stimulation from first order neurons, secondary (centrally mediated) hyperalgesia and allodynia, Prolonged stimulation of AMPA and kainate receptors eventually activates NMDA receptors–> leads to upregualtion of all these receptors to cause increased neuronal excitability
Can be prevented with preemptive analgesia
what are the types of receptors for transduction of pain
receptors for cold, heat, acid, and mechanical
What are the three primary afferent sensory neurons that transmit to the spinal cord
A-beta fibers- large, myelinated; transmits pressure and innocuous sensation (like poking)
A-delta fibers- small, myelinated; transmits sharp, fast pain (like stabbing)
C fibers- small, unmyelinated; transmits burning, slow pain
what is projection
the conveyance of nociceptive information through the spinal cord to the brain (brain stem–> thalamus –> cortex)
What is perception
the integration of nociceptive information by the brain, the concious, emotional experience of pain
What is the difference between primary and secondary hyperalgesia
primary is at the site of injury causing localized pain
secondary is the site surrounding the injury causing more chronic pain, not as specific and localized
What is the pathophysiology of opioids, best use, and DEA schedule
augment endogenous anti-nociceptive pathways causing profound analgesia, best for C-fiber anti-nociception
Schedule II (ex. fentanyl)
What is the pathophysiology of tramadol and clinical use
It is an atypical mu-opioid agonist and serotonin and norepinephrine reuptake inhibitor
more effective as adjunct to a multimodal approach, better in cats
What is the pathophysiology of alpha-2 agonists
Occupy the alpha-2 receptors along the nociceptive pathway and block action potentials locally
prolong duration of nerve blocks (C-fibers)
analgesia use limited by sedative effect
What is the pathophysiology and side effects of non-steroidal anti-inflammatory agents
Inhibit COX-1 and COX-2, COX-2 selective drugs are better for pain management (COX-1 are used for anti-thrombotic effects)
Side effects- gastrointestinal, hepatic, renal
What is the only approved NSAID for cattle
Flunixin meglumine (banamine)
What is the pathophysiology of ketamine and Tiletamine and the DEA schedule
NMDA antagonists- block receptors at the dorsal horn to prevent wind-up and central sensitization
Bind to opioid receptors to activate them
localized anesthetic effect to block action potentials along nociceptive neurons too
DEA schedule III
What is the pathophysiology of local anesthetic agents
blocks action potentials by blocking the sodium channels, helps prevent wind-up/central sensitization because impulse never reaches dorsal horn
What are the adverse effects of local anesthetic agents and the toxic doses for bupivicaine and lidocaine
CNS toxicity (cats and horses much more sensitive), CVS toxicity, Methemoglobinemia, allergic reactions, chondrotoxicity
Bupivicaine should not exceed 2mg/kg total dose
Lidocaine should not exceed 8mg/kg total dose
What is the pathophysiology of gabapentin
Blocks calcium channels and inhibits NMDA receptors, used for neuropathic pain primarily
What is the pathophysiology of amantadine
NMDA receptor antagonist, may enhance effects of NSAIDS, Gabapentin, and opioids
What is the pathophysiology of amitriptyline
inhibits reuptake of serotonin and norepinephrine and is an NMDA receptor antagonist, good for neuropathic pain but be wary when combining with other drugs effecting serotonin (serotonin syndrome) (ex. tramadol, TCAs, SSRIS, etc)
What is the normal range for blood pressure
Mean small animal- 60-150mmHg
Mean large animal
>500kg- >70mmHg
<500kg- >80mmHg
What are relevant interventions for hypotension
Bradycardia- use anticholinergic drug (atropine) or sympathomimetic drugs (ephedrine)
Tachycardia- use a beta blocker
Decreased preload- give fluids
Decreased Systemic vascular resistance- decrease inhalant use or give vasopressor (drugs that work at alpha receptors)
Contractility not appropriate- reduce inhalant, use positive ionotropic agents
Big picture- is heart rate appropriate (treat if bradycardic and hypotensive), is volume status normal, use as little inhalant as possible, then consider ionostope or vasopressor
What are the effects of drugs that target alpha receptors and ones that target and beta receptors
Alpha receptors cause vasoconstriction to increase systemic vascular resistance and preload
Beta receptors increase contractility in the heart and increase heart rate
What drugs are both a beta and alpha agonist and what do they do if they do both
dopamine, norepinephrine, ephedrine, epinephrine
They increase contractility and systemic vascular resistance
What drug is a beta agonist only and is commonly used in large animals
dobutamine
What drug is used often in CPR and anaphylaxis to increase heart rate, contractility, and SVR
epinephrine
What drug is used often in CPR or refractory vasodilatory hypotension to increase SVR
vasopressin
What is the downside of drugs for hypotension (ionotropes and vasopressors)
they are not benign and they make the heart work harder
What drug is the best choice for septic patients increase heart rate, contractility, and SVR
norepinephrine
What are relevant interventions for hypertension
ensure patient isn’t too light under anesthesia or isn’t too painful, if given alpha 2 agonist or vasopressor those can cause it
Cushing reflex in brain- increase in intracranial pressure causes massive catecholamine release, will look like high BP, low HR, and apnea/irregular breathing
Need to increase inhalant or increase pain meds or add adjunctive pain meds, may need to reverse alpha 2 agonist/vasopressor, if Cushing reflex need to hyperventilate and give hypertonic saline and mannitol
What are the five causes of hypoxemia and relevant interventions for each cause
Decreased inspired fraction of oxygen- administer 100% oxygen
alveolar hypoventilation- Provide intermittent positive pressure ventilation
right to left shunt- surgical intervention
diffusion impairment- O2 supplementation or ventilation (depends on severity)
ventilation/perfusion mismatch (most common)- often alveoli collapse so they are perfused but not ventilated- need to give big breath and hold it to pop them open with 100% O2 and move to sternal recumbency if able
What are the signs of hemorrhage/ significant blood loss
Patient is tachycardic and hypotensive, may have abnormal PCV but if acute won’t be abnormal until volume is replaced with fluid
What do you do if there is a loss of blood volume <20% of total blood volume
isotonic replacement solution at 3x the blood lost
What do you do if there is a loss of blood volume >20% of total blood volume
Isotonic replacement solution and blood product if available
consider autotransfusion (surgeon draws it up and you put it right back)
What volume of blood loss can result in life threatening circulatory failure
30-40% of total blood volume
What are the blood volume amounts for a dog, cat, horse, and cow
Dog- 90 ml/kg
Feline- 55ml/kg
Horse- 76ml/kg
BOvine- 55ml/kg
How much blood can a 20 kg dog lose and they will need blood products or not
20kg x 90ml/kg= 1800 ml
1800 x .2= 360ml
the dog can lose up to 360 ml before blood products are needed, anything under that you can give isotonic fluids at 3x the blood volume lost
What is the intervention for VPCs
lidocaine or if that’s ineffective procainamide
What is the intervention for 1st, 2nd, and 3rd degree AV blocks
1st and 2nd degree are often benign/normal, if the bradycardia is unacceptable sometimes treat with anticholinergic
3rd degree requires a pacemaker
what is the intervention for atrial fibrillation
calcium channel blockers or sometimes electrocardoiversion (defibrillate)
What are the key components for the RECOVER guidelines of basic and advanced life support, and monitoring
Basic- recognition, chest compressions, airway management, ventilation
Advanced- monitoring, drugs, defibrillation, fluid therapy
Monitors- ECG, ETCO2, Pulse Ox, Blood gas analysis
What drug may be helpful in vagal arrests
atropine
What does the thoracic pump technique of chest compressions aim to do and what type of animals is it used on
it creates negative pressure in the throrax to move blood, used in medium to large breed dogs
what does the cardiac pump do and what animals is it used on
it creates positive pressure in the ventricles by physically squeezing them
it is used in cats, small dogs, and keel chested dogs
