Anesthetic Depth and Monitoring Flashcards
What is the use of EEG?
- gives information about cortical, but not subcortical activities
- correlates with anesthetic depth, but does not predict arousal
What is BIS?
- bispectral index monitor
- provides number between 0 and 100
- easier to interpret than EEG
Describe Stage 1 of anesthesia
- voluntary movement
- from drug administration to loss of consciousness
- excitement and struggle may occur
- epinephrine release, tachycardia, irregular breathing, coughing
- pupillary dilation
- ataxia, recumbency
Describe Stage 2 of anesthesia
- involuntary movement
- from loss of consciousness until onset of regular breathing
- state of delirium, struggling and exaggerated reaction to stimuli
- epinephrine release, tachycardia, irregular breathing
- pupillary dilation, strong palpebral reflex
- strong jaw tone, intubation not possible
Describe Stage 3 of anesthesia
- general anesthesia
- from onset of regular breathing until cessation of effective breathing
- no movement in response to stimuli
- progressive muscle relaxation, loss or reflexes, and respiratory depression
- 3 planes
Describe Plane 1 of Stage 3 of anesthesia
- light anesthesia
- weakening palpebral and corneal reflexes
- no swallowing reflex
- pupils constricted
- no involuntary movement
Describe Plane 2 of Stage 3 of anesthesia
- medium anesthesia
- progressive intercostal paralysis
- stable respiration and pulse
- loss of laryngeal reflexes
- weak palpebral, strong corneal reflexes
Describe Plane 3 of Stage 3 of anesthesia
- deep anesthesia
- diaphragmatic breathing
- pupils dilate, eyes central
- no palpebral/corneal reflexes
Describe Stage 4 of anesthesia
- overdose
- respiratory failure
- cardiac arrest
- death
What depth of anesthesia is indicated by rotated eyes?
Central eye + dilated pupil?
rotated: stage 3, plane 2
central: both too light or too deep
What depth of anesthesia is indicated by spontaneous eye movement?
too light anesthesia
arousal may be imminent
What depth of anesthesia is indicated by spontaneous blinking?
too light anesthesia
slow blinking may be seen in horses
What depth of anesthesia is indicated by lacrimation?
light but appropriate depth
What is occurring during the P wave of an ECG?
atrial depolarization: contraction
What is occurring during the QRS complex of an ECG?
ventricular depolarization
What is occurring during the T wave of an ECG?
ventricular repolarization
Describe the mammalian type A conduction system
- purkinje fibers excite the endocardium only
- excitation spreads via muscle fibers
- generates base-to-apex current flow
- humans and small animals
Describe the mammalian type B conduction system
- purkinje fibers penetrate the myocardium
- most of the myocardium is excited simultaneously
- generates apex-to-base current flow
- negative R wave
- horses, ruminants, pigs
What is the set up of B-type leads?
white: right jugular furrow or withers (RA)
black: cardiac apex region (LA)
red: anywhere else (LL)
Which is the highest point of the BP curve?
Which is the lowest point?
systolic pressure is the highest point
diastolic pressure is the lowest point
What is the equation for BP?
BP = (HR x SV) x SVR
HR x SV = CO
SV - stroke volume
SVR - systemic vascular resistance
Where do you position the transducer to measure blood pressure?
at the level of the base of the heart
- point of shoulder in sternal recumbency
- point of sternum in lateral recumbency
What values of PaO2 and SaO2 indicate hypoxemia?
PaO2 < 60 mmHg
SaO2 < 90%
What affects the results of a pulse ox reading?
- tissue thickness
- hypoperfusion (vasoconstriction)
- anemia
- pigmentation
- movement
- presence of abnormal Hb species
