9: Monitoring Flashcards
When monitoring, what 3 things together maintain tissue/organ perfusion with oxygenated blood?
Circulation, Ventilation, Oxygenation
What does the word “monitor” mean?
To warn
Physiology/homeostasis is altered by _____.
drugs
What is the purpose of a monitor?
To warn anesthetist of changes in depth or status of patient to facilitate an early response
When does monitoring begin and end?
Begins at pre-op, ends at recovery
Peri-op mortality usually occurs within _____.
1st 3 hours
An individualized anesthesia plan provides basis for what 3 things?
- Drug selection
- Monitoring & support
- Anticipated complications (& plan of action to address them)
T/F: The anesthesia record is a legal document.
True
The anesthesia record prompts to _____, _____, & _____ patient status.
observe, evaluate, record
When can irreversible CNS and cellular changes occur?
Within 3-5 min of cessation of blood flow
What is the best/most expensive monitoring equipment?
YOU!!!
What should you, the anesthetist, know about your equipment?
Limitations, reasons for erroneous readings, how to troubleshoot
What things can we observe to determine anesthetic depth?
Eye position, reflexes, MAC, end tidal inhalant gas, EtCO2
What things can we observe to monitor circulation?
PE, ECG, BP (indirect, direct)
What things can we observe to determine ventilation?
Clinical evaluation, esophageal stethoscope, capnography, blood gas analysis
What things can we observe to determine oxygenation?
Clinical evaluation, pulse ox, blood gas analysis
What specific things do we look at in our patient to determine anesthetic depth?
Eye position, reflexes, muscle relaxation, movement, end tidal [] of anesthetic gases
In what spp is eye position a reliable indicator of anesthetic depth?
Dogs, cats, cattle
Eyes roll _____ at the surgical plane.
ventrally
Eyes are _____ at light/deep planes.
centered
Eyes are centered at all planes with _____ anesthetics.
dissociative
What eye position do horses keep under anesthesia? How can you tell if they are too light?
Medial position;
Nystagmus/tearing = too light
Why is eye position unreliable in goats, sheep, and camelids?
The globe does not rotate
What is one main reflex that can be used to check anesthetic depth?
palpebral
How is the palpebral reflex associated with depth in small animals and how is it determined?
Absent at surgical plane;
Tap medial canthus
How is the palpebral reflex associated with depth in horses and how is it determined?
Present at surgical plane;
Gently brush cilia, slow closure of eyelids
How is the palpebral reflex associated with depth in ruminants/swine?
Absent at surgical plane
What reflexes other than palpebral can be used to evaluate anesthetic depth?
Withdrawal (toe pinch), corneal (ALWAYS present)
When should a corneal reflex NOT be checked?
When a patient is believed to be alive
What is the relationship between jaw tone and anesthetic depth?
It will vary with depth, is subjective, and is not reliable with dissociative anesthetics
What is MAC?
(Minimum Alveolar Concentration)
[] of inhalant in the lungs needed to prevent movement (motor response) in 50% of animals in response to a noxious or surgical (pain) stimulus
MAC is used to compare the _____ or _____ of inhalant anesthetics.
strengths, potency
What is the MAC for iso in dogs? Cats? Horses?
Dogs = 1.28%
Cats = 1.63%
Horses = 1.3%
What is the MAC for sevo in dogs? Cats?
Dogs = 2.3%
Cats = 2.6%
95% of patients are adequately anesthetized at ____ MAC.
1.5x
What things can decrease MAC?
Pre-med, intra-op analgesia
MAC reflects _____, not _____.
population, individual
What is End tidal-inhalant?
[] of inhalant gas expired at the end of expiration
What does Et-inhalant reflect?
[] of gas in brain
Et-inhalant % is _____ than the vaporizer setting.
more precise
What is normal repiration controlled primarily by?
Blood levels of CO2 (PaCO2)
EtCO2 monitors exhaled CO2 _____.
noninvasively
EtCO2 is an indirect measure of _____.
arterial Co2 (PaCO2)
What is the value difference between EtCO2 and PaCO2?
EtCO2 is 3-5 mmHg < PaCO2
What is the normal awake value for EtCO2?
~40
What is the normal EtCO2 value in anesthetized patients?
<55-57 mmHg
Adequate _____ is the key to patient survival.
DO2 = delivery of oxygen to tissues
What does DO2 require?
CV and respiratory systems
What is the DO2 equation?
DO2 = CO x CaO2
(CaO2 = oxygen content of blood)
What is the equation for CaO2?
CaO2 = HbO2 + PaO2
(HbO2 = oxygen bound to Hgb)
How can circulation be assessed pre-op?
CRT
What is normal CRT? What does it mean if this is prolonged?
Normal = <2 seconds
Prolonged –> poor tissue perfusion or dehydration
Why is CRT not very useful during anesthesia?
Drugs and increased PaCO2 cause vasodilation (CRT can decrease);
Dexmedetomidine –> vasoconstriction
How can circulation be clinically evaluated?
Palpation of pulses, auscultation (esophageal stethoscope, doppler), ECG, BP
What aspects of the heart beat should be ausculted?
Presence, absence, strength, rhythm
Where can peripheral pulses be palpated in the dog and cat? Horses?
Dog and cat = femoral, dorsal pedal, lingual
Horses = facial, trans facial, MC/MT, coccygeal
What is a normal HR in dogs? cats? Horses?
Dogs = >60
Cats = >80
Horses = constant whether or not it is under anesthesia
How is pulse pressure (PP) calculated?
SAP (systolic) - DAP (diastolic)
PP does not indicate _____.
MAP
Where does the tip of the esophageal stethoscope go?
@ level of heart
What are advantages to using an esophageal stethoscope?
Inexpensive, can monitor resp rate
What are disadvantages to using an esophageal stethoscope?
Difficult to use in certain cases, can disconnect, need amp or dedicated person
What are 3 limitations to ECG?
- Electrical activity only, no info about mechanical function
- PEA/EMD –> cardiac arrest, normal electrical activity but no pulses
- Should not be used alone
How should the 3 ECG leads be attached (3 ways)?
Limb leads, esophageal leads, base apex
Where do the limb leads of an ECG go?
RA, LA, LL;
Selection of lead II on the ECG
Where are probes of an esophageal ECG placed?
RA and LL on esophageal probe, LA on ear or neck;
Select lead II on ECG
What are 3 advantages to using an esophageal or base-apex lead placement?
- Avoids attachment to hindquarters
- Accessible by anesthetist
- Minimize motion artifact
Where are base apex ECG leads placed?
RA and LL attach to right or left jugular furrow, LA attach to opposite thoracic wall caudal to heart;
Lead I - negative deflection
Lead III - positive deflection
How can BP be taken indirectly?
Doppler (SAP)
Oscillometric (SAP, DAP, MAP)
How can BP be measured directly?
Arterial catheter, transducer & monitor
(SAP, DAP, MAP)
What is an ultrasonic doppler used for?
Measures pulse, blood flow, and SAP using sphygmomanometer & cuff
How is a doppler BP taken?
- Probe and gel placed over peripheral artery - limb or tail
- Cuff placed proximal to probe, inflated until it exceeds SAP (silences doppler signal)
- Cuff gradually deflated until first signal is audible
- BP on sphygmomanometer is SAP
What are advantages to using a doppler?
Cost, SAP
What are disadvantages to using a doppler?
Proficiency of use, not automatic, accuracy dep on cuff, weak signal with vasoconstriction/hypotension
Cuff for BP should be ___% circumference of limb.
~40%
Where can a cuff for oscillometry be placed?
- Limb
- Hind = above or below tarsus
- Fore = above carpus
- Tail base
What are advantages of using oscillometry?
Easy to use, set for automatic measurements
What are disadvantages to using oscillometry?
Technology motion sensitive, decreased accuracy at low BP/high HR or arrhythmia, accuracy dep on cuff size
Too small of a cuff _____ BP.
overestimates
Too large/loose of a cuff _____ BP.
underestimates
What is the gold standard for measuring SAP, DAP, and MAP?
direct measurement
What are advantages to using direct BP measurement?
Accurate, continuous, arterial blood gas sampling, ideal for critical patients
What are disadvatages to using direct BP?
Cost, skill, complications
What are some complications that can arise from using direct BP?
Infection, thrombosis, hematoma, air embolism, exsanguination, drug injection
Where are common sites of arterial catheter placement in dogs and cats? Horses?
Dogs and cats = dorsal pedal, lingual
Horses = facial, ear, MT, trans facial