Block 1: Anesthetics- General
Terms
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- MAC awake
-
50% of patients can be awakened
= 1/2 MAC - MAC
- 50% of patients will not move at surgical incision
- ED 95
-
95% of patients will not move at surgical incision
=1.3 x MAC - MAC-BAR
-
50% of patients have blocked autonomic response
= 1.5-2 x MAC - inhalation anesthetics
-
N HIDES
Nitrous oxide
Halothane
Isoflurane
Desflurane
Enflurane
Sevoflurane - IV anesthetics
-
sedatives- (BBEP) barbituates, benzodiazepine, etomidate, propofol,
opiods- -tanyl's
dissociative- ketamine - analgesia only
- Stage of Analgesia
- delirious, excited, amnestic, irregular respirations, struggling, retching, vomiting
- Stage of Excitement
- loss of corneal, swallowing, and eyelid reflexes
- Stage of surgical anesthesia
- cessation of spontaneous respiration
- stage of medullary depression
-
To increase speed of induction dec/inc...
inspired concentration
pulmonary ventilation
pulmonary blood flow
arterio-venous conc. gradient -
inc
inc
dec
dec - Major route of elimination for inhalation anesthetics
- lung
- elimination only important for...
- halothane
- Myer-Overton principle
- interactions with the lipid matrix of the neuronal membrane
- age
- effects the MAC
- concomitant drugs
- effects the MAC
- temp
- effects the MAC
- certain disease states
- effects the MAC
- height
- does not effect the MAC
- sex
- does not effect the MAC
- weight
- does not effect the MAC
- decreases SVR
- isoflurane and desflurane
- myocardial depressant
- halothane and enflurane
- reduce myocardial oxygen consumption
- all
- sensitizes myocardium to catecholamines
- halothane
- may predispose to ventricular arrhythmias
- halothane
- tidal volume
- decreased
- respiratory rate
- increased
- greatest decrease in ventilatory response to PaCO2
- influrane
- ventilatory response to hypoxia
- dec
- metabolic rate of brain
- decreased
- brain blood flow
- increased
- causes seizure activity on EEG
- enflurane
- renal blood flow
- decreased
- hepatic blood flow
- decreased
- possibly hepatotoxic
- halothane
- cause of acute liver toxicity
- halothane related oxidative metabolites
- cause of acute kidney damage
- sevoflurane causing fluoride ion toxicity
- decreased methionine synthase activity
-
prolonged N2O
- may cause megaloblastic anemia and peripheral neuropathies - treatment for malignant hyperthermia
- dantrolene
- most widely used inhaled agent in the world
- halothane
- high solubility
- halothane
- most widely used inhaled agent in moder countries
- isoflurane
- lowest solubility
- sevoflurane
- fastest onset/ on/off changes
- sevoflurane
- fluoride toxicity
- sevoflurane
- MAC > 100%
- N2O
- most common agent for induction of GA
- thiopental (barbituate)
- dose dependent decreases in SV, MAP, CO; and potent respiratory depressent
- thiopental
- myoclonic movements
- etomidate
- amnestic, anti-emetic, Total intravenous anesthesia
- propofol
- sedative mechanism of action
- CNS depression via enhancement of GABAa actions
- act at mu, kappa and delta receptors
- opiods
- best of the IV analgesics
- opiods
- dose dependent respiratory depression and potential chest wall rigidity
- opiods
- 4 most common opiods
-
fentanyl
sufentanil
alfentanil
remifentanil (new and ultra-short action) - opiod antagonist
- naloxone
- anxiolytic/amnestic
- benzodiazepines
- most common IV benzodiazepine
- midazolam
- benzodiazepine antagonist
- flumazenil
- phenylcyclidine derivative which produces dissociative anesthesia- catatonia, amnesia, analgesia
- ketamine
-
CV stimulation, increased cerebral metabolic rate, increased cerebral bood flow
post-op hallucinations and disorientation - ketamine