Anesthesia Flashcards
What two drugs cause an increase in amplitude of cortical responses?
Etomidate and Ketamine
(In IONM practice, better to have these drugs infused over time rather than bolused. If infusion is not an option, best to set baselines prior to bolus of either drug given)
Isoflurane MAC value?
1.2% MAC
Sevoflurane MAC value?
2 % MAC
medium solubility, takes longer than Desflurane to wear off
Desflurane MAC value?
6% MAC
rapid onset, faster SSEP changes compared to than other gases
low solubility, easiest to penetrate cells, fastest to work
Nitrous Oxide (N20) MAC value?
105% (used together with another gas causes a compound effect)
causes most profound depression of cortical responses
What are the two rare gases not commonly used in general anesthesia?
Enflurane (proconvulsant-causes seizure spikes in EEG) and Halothane
Anesthesia
Loss of consciousness, lack of response to stimuli
Amnesia
Loss of memory/prevention of recall
Analgesia
Block noxious stimuli (pain) activation of nervous system
Anxiolytic
Reduces Anxiety
Narcotics (Opioids)
Sufentanil Fentanyl Alfentanil Remifentanil (short acting, must be infused) Morphine
Used to control perioperative pain (analgesia) and anxiety
Barbiturates
Thiopental
Phenobarbital
Amytal
Used for rapid induction in the beginning of case or after wake-up test or to provide brain protection during potential ischemia
Rapid onset/offset
Bolus may cause burst suppression pattern in EEG, depression of cortical SSEP and tcMEP responses
Propofol
AKA Diprivan
Commonly used to achieve unconsciousness
Bolus of Propofol (or heavy maintenance infusion) may cause burst suppression pattern in EEG, depression of cortical SSEP and tcMEP responses
Benzodiazepines
Midazolam (Versed)
Diazepam (Valium)
Lorazepam (Ativan)
Commonly given in preop for anxiety (anxiolytic)
Minimal changes in SSEPs at common dosages
What Does MAC stand for in reference to inhalational agents?
Minimum Alveolar Concentration, minimum concentration of an inhaled anesthetic that will prevent a noxious response (movement) to a surgical stimulus (e.g. skin incision) in 50% of operative patients
What is an Agonist?
A drug that binds to a receptor inside a cell or on its surface and causes the same action as the substance that normally binds to the receptor
ex. Succinylcholine (depolarizing neuromuscular blockade)
What is an Antagonist?
An antagonist does the opposite of an agonist. It binds to receptors, and stops the receptor from producing a desired response
ex. Rocuronium (non-depolarizing neuromuscular blockade)
Stages of General Anesthesia
- Pre-medication: Anxiolytic agents given prior to arrival in OR
- Induction: Large boluses of drug given to induce unconsciousness (usually propofol)
- Maintenance: Steady-state infusion to maintain unconsciousness and pain control
- Emergence: Return to consciousness after procedure is completed
- Post- Anesthesia Care: Full recovery from anesthetic agents
Two Commonly Used NMB Reversal Agents
Neostigmine: Takes 5-10 minutes to achieve TOF 4/4, must have at least 1 twitch before administering for best results.
Sugammadex: Takes 1-3 minutes to achieve TOF 4/4, can be given to patients with TOF 0/4.
Depolarizing Muscle Relaxants
Succinylcholine
Short Acting: 3-5 minutes
Used for induction
Non-Depolarizing Muscle Relaxants
Atracurium
Vecuronium
Rocuronium
Pancuronium
All intermediate acting, lasting 40-60 minutes
Hypotension & Effects on IONM
Spinal cord perfusion is unaffected by drops in blood pressure until MAP (mean arterial pressure) reaches 60mmHg - you may see changes in evoked potentials at this level and lower. Amplitude affected more than latency.
Temperature & Effects on IONM
In general, lower temperature = increased latency, higher temperature = decreased latency.
Evoked potentials may not show any changes until temperature drops below 30 C
