Anesthesia Monitoring Flashcards
What is the first stage of Anesthesia?
Awake
inducement, excitement, miosis, voluntary struggling
What is the second stage of anesthesia?
Delirium
obtunded reflexes, mydriasis, still excited, involuntary struggling
What are the 3 planes for the third stage of anesthesia?
- Light
- Medium
- Deep (early overdose)
What is the fourth stage of anesthesia?
Overdose
Very deep anesthesia; respiration ceases, CV function depresses and death ensues immediately
Autonomic changes, physical and clinical signs are all a(n) ____ method for assesseing anesthesia depth.
Subjective
E
ECG activity is a(n) ____ method for assessing anesthesia depth.
an objective
What is a reliable way to assess anesthesia depth in carnivores?
Eye positioning
- Central for light and deep, rotated for adequate anesthesia
What reflex should all species maintain while under general anesthesia?
Corneal reflex
What is a cardinal sign of light anesthesia in horses? What can also stimulate it?
Nystagmus
- hypoxia and hypercapnia can also induce nystagmus
hypercapnia = increased CO2
When is the palpebral reflex present/not present in dogs/cats, horses, and camelids?
What is the Bispectral Index?
Exerts an objective value to indicate anesthesia depth via EEG-derived parameters ranging from 0-100
What CNS and PNS signs are sued to assess anesthesia depth?
Ocular reflexes/positioning + muscle tone
Why must cardiovascular function be assessed under anesthesia?
- minimize organ damage
- decrease morbidity and mortality
- monitor for the #1 complication: hypotension
Where can pulse be palpated for assessing circulation during anesthesia?
What do injected mucous membranes indicate?
Vasodilation
Septicemia
Sepsis: causing endothelial cells to relase excess nitric oxide (NO), which is a vasodilator
What do Systolic vs MAP vs Diastolic BP indicate?
Systolic: cardiac contractility (90-140mmHg)
MAP: tissue perfusion (60-90mmHg)
Diastolic: peripheral vascular resistance (50-60mmHg)
Common causes for low systolic BP readings?
Common causes for high systolic BP readings?
Common causes for low or high MAP BP readings?
Low: low systolic, diastolic or both
High: high systolic, diastolic or both
Common causes for low diastolic BP readings?
Common causes for high diastolic BP readings?
A patient has a low MAP; what other signs of decreased tissue perfusion will be seen?
Pale mm
CRT > 2s
What are the two major components of MAP?
CO and SVR
BP = CO x SVR
What triggers a ventricular arrhythmia in an anesthetized patient?
Impaired blood flow: compromised CO, BP or tissue perfusion
What drug classes can be used to treat bradycardia under anesthesia?
- Anticholinergics (atropine, glycopyrrolate)
- Sympathomimetics (epinephrine)
What drug classes can be used to treat tachycardia under anesthesia?
- Sodium channel blocker (e.g., lidocaine), +/- beta blocker (-olol)
Two phases of Dexmedotomidine
Phase 1: short-lived hypertension + bradycardia
Phase 2: reflex hypotension + bradycardia
don’t use anticholienrgic until phase 2
Systemic Arterial Pressure (SAP):
Pre-hypertensive, hypertensive/moderate risk of TOD, and severe hypertensive/TOD mmHg values.
Factors of situational hypertension
Most likely to occur during anesthesia: pain, incr. in sympathetic tone, light plane of anesthesia
Prevention: adequate analgesia protocol
Secondary versus idiopathic hypertension?
MAP and SAP hypotension readings
MAP: < 60mmHg
(large animal = < 70mmHg)
SAP: < 80mmHg
A patient develops hypotension; there is adequate anesthetic depth, and you cannot decrease the anesthetic requirement. What other ways can you increase blood pressure?
- Balance anesthesia: administration of combo of drugs to create the anesthetic state.
- Multi-modal analgesia
Frank-Starling Law regarding contractility?
A greater preload (EDV) results in increased SV
e.g., bolus, maintenance
At what % blood loss should you begin a blood transfusion
> 30% blood loss
When is administering an anticholinergic to increase HR and MAP contraindicated?
if an alpha-2 agonist (dexmedetomidine, xylazine) was given b/c of their hypertensive effect
Define Tachyphylaxis
when a drug loses clinical effect in the body after giving consecutive doses
Why is Ephedrine only given as single-dose boluses and never as a CRI
Ephedrine is a central nervous system (CNS) stimulant that is often used to prevent low blood pressure during anesthesia. It is a sympathomimetic.
Because tachyphylaxis will develop after prolonged and repeated doses (b/c drug depletes endogenous norepinephrine stores)
SPO2 versus PaO2
SPO2 = measures saturation % of oxygenated Hg in arterial blood
PaO2 = measures partial pressure of arterial oxygen - most accurate!
PaO2 hypoxemia value
PaO2 < 60mmHg
hypoxemia -> hypoxia -> cyanosis
What does Respirometry measure
Minute Ventilation = Vt x RR
Why is PaCO2 measured? What are its values in hypercapnia versus hypocapnia?
- PaCO2: to assess and monitor ventilation efficiency (via blood gas analyzer)
- WNL = 35-45mmHg
- Hypercapnia = > 45mmHg (hypoventilation -> respiratory insuffiency)
- Hypocapnia = < 35mmHg (hyperventilation)
What is permissive hypercapnia
slight elevation above normal PaCO2, which can be beneficial for anesthetized patients. < 56 mmHg
ETCO2 reflects the PaCO2 where?
in the alveoli
On a capnograph, when the wave hits close to zero, is this inhalation or exhalation, and why?
Inhalation – little-to-zero CO2 is normally inhaled
When a hypoventilating patient’s tidal volume is compromised (e.g., anesthesia) and respiratory rate increases, will hyperventilation occur?
NO- the increased RR is bc the body is trying to compensate for the compromised Vt –> patient’s minute ventilation (MV) stays the same // hypoventilation
MV determines the elimination of CO2
PaO2 is ~how much of FiO2?
PaO2 ~5xFiO2
SaO2 vs SPO2
SaO2 is the oxygen saturation of arterial blood, while SpO2 is the oxygen saturation as detected by the pulse oximeter
When pulse oximeter reads 90% SpO2, what is the PaO2?
PaO2 = 60mmHg = hypoxemia!
