Monitoring the anesthetized patient Flashcards
What is anesthesia (4 factors)?
- Lack of awareness of all aspects of environment
- Reversible, neurological depression; unconsciousness
- Lack of sensation; analgesia
- Amnesia
- Muscle relaxation
Anesthesia is the overlap of what 2 things?
Overlap of analgesia and unconsciousness
T/F: Anesthetics are inherently good analgesics
FALSE–anesthetics are not inherently good analgesics
What are the signs (indirect) of neurologic depression?
- Physical signs, somewhat subjective
- Physiologica parameters of the autonomic system
- Quality of pulse
- To avoid “too deep”
How do we know if the patient is adequately anesthetized?
- Adequate neurological depression
- Can we monitor the CNS?
- EEG
- Bi-spectral analysis (BIS)
What is the bispectral analysis? What is it based on and what do low values represent?
- Processed EEG that monitors cortical activity
- Based on an algorithm, the EEG is quantitated to a scale from 0-100
- The lower the number, the more depressed
- Better titration of anesthetics
T/F: Bispectral analysis is a practical monitoring modality in vet med
FALSE–usefulness is uncertain–depends on drugs used; it is not yet a practical monitoring modality in veterinary medicine
What are the physical signs to assess depth of anesthesia?
- Presence/absence of purposeful movement in response to stimuli
- Potency of inhalants based on this fact (MAC [50% subjects] to prevent movement)
- Muscle relaxation
- Eyeball rotation*
- Jaw tone*
- Abdominal mm tone
- Reflexes
- Palpebral*
- Corneal
- Anal
- Pupillary light (not helpful)
- Autonomic signs
- Changes in cardiovascular, respiratory parameters
What are the different stages based on ether anesthesia? What should you avoid (gas anesthetic)? Which is the ideal surgical plane (gas anesthetic)?
- Avoid excitement (stage II–delerium)
- Ideal surgical plane in stage III plane 2
T/F: There is no clear demarcation between stages or planes of ether anesthesia
TRUE
How is movement used to determine adequate/inadequate anesthesia?
- Purposeful movement to a noxious stimulus is a reliable sign of inadequate anesthesia (too light) for that particular stimulus
- Ex: lack of movement to a toe pinch does not mean they won’t move in response to a surgical stimulus
- Useful to test soon after induction or during mask inductions
How are reflexes used to determine adequate/inadequate anesthesia?
- Gag or swallow reflexes, moving tongue are reliable signs that they are too light
- Don’t even try to intubate
- Palpebral reflex–suggests a too light plane of anesthesia for surgery (except horse)–may/may not be adequate anesthesia
- Corneal reflex–should always be present (don’t elicit often)
- Pupillary light reflex–not a reliable sign of adequate depth–can be present at a surgical plane
How is jaw tone used to measure anesthetic depth?
- Reliable sign of relaxation and depth (dog/cat/bird) although subjective
- Test beginning of anesthesia to have ‘baseline’
- Should be easy to move with 2 fingers
- Test intermittently during anesthesia
How is eye position used to determine anesthetic depth?
- Extra-ocular mm relax at different stages
- Generally, we like to see the eyeball rolled ventrally (see some sclera); probably has no palpebral reflex
- A central eyeball may suggest too deep
- The 2 eyes may differ–look at BOTH
- Look at the palpebral fissure
- Lack of palpebral fissure (closed eyelid) reliable sign of light anesthesia; may/may not have palpebral reflex
- Wide palpebral fissure suggests deeper plane
What eye signs in large animals are used to determine anesthetic depth?
- Horse/ruminant tend to roll eyes forward
- Tearing is a sign of light anesthesia–common to see in horse
- Swine–eye signs (nor jaw tone) are not very helpful
I can’t remember if we have to memorize this, but here’s the chart for all the reflexes during various planes of anesthesia
