Anesthetics Flashcards
1
Q
Nitrous oxide
A
- inhaled general anesthetic
- low blood solubility –> fast on/off set
- potent analgesic: 20%
- weak anesthetic due to low lipid solubility
- few negative features: no cardiac arrhythmias, seizures or hepatic/renal toxicity
- rarely ever used alone, not safe to do so
2
Q
Halothane
A
- inhaled general anesthetic
- prototype halogenated hydrocarbon
- high lipid solubility = potent anesthetic
- weak analgesic, use with nitrous oxide or other potent analgesic
concerns:
- relaxes smooth muscle so not good for delivery of baby
- malignant hyperthermia (therapy: dantrolene)
- hepatic necrosis
Effects during stage 3 surgical anesthesia:
- CV - hypotensive, neg inotroph, depresses baroreceptor with gradual sympathetic activation, bradycardia, can induce re-entrant cardiac rhythms, increased cardiac sensitivity to epinephrine-induced cardiac arrhythmias
- increased response to skeletal muscle relaxants - reduces need for muscle relaxant. this is a problem for neurologic patients (myasthenia gravis)
Post surgical effects:
- recovery is slow so Stage II delirium may occur
- hepatotoxicity due to metabolites (bromide)/preservatives
- post-op shivering/heat loss
- -> Halothane has been replaced by newer halogenated hydrocarbons
3
Q
Dantrolene
A
therapy for malignant hyperthermia, a rare congenital condition. First the facial muscles become rigid, then the muscles throughout the body become rigid, activated skeletal muscle increases hyperthermia –> tissues become damaged
4
Q
Enflurane
A
- inhaled general anesthetic
- more stable than halothane
- less neg inotropic effect on the heart
- lower incidence of severe cardiac arrhythmias
- greater decline of skeletal muscle tone
- no malignant hyperthermia or hepatic necrosis
Post surgical effects:
- at doses greater than MAC, EEG signs of seizures, avoid in epileptics
- metabolized to free F- but not sufficient to cause renal toxicity
5
Q
Isoflurane
A
- inhaled general anesthetic
- less soluble in blood than halothane and enflurane which means faster on/offset
- less neg inotropic action, dilates coronary arteries, less sensitization of the heart to epinephrine-induced arrhythmias
- not a convulsant
- enhances relaxation of skeletal muscle
Concerns:
- irritating to respiratory tract - IV induction overcomes this
- hypotension during stage III surgical anesthesia
- respiratory depression and decreased ventilatory response to hypoxia or hypercarbia often necessitates assisted ventilation
6
Q
Desflurane
A
- inhaled general anesthetic
- blood solubility similar to nitrous oxide, therefore fast on/offset
- very potent - MAC: 6
- no serious cardiac arrhythmias
- no malignant hyperthermia
- 0.02% metabolized means fewer toxic metabolites to cause renal or hepatotoxicity
- no seizure like effects
- sensitizes skeletal muscle to relaxants
- pungent odor and is irritating to the respiratory tract, induce with IV
- circulatory effects resemble isoflurane
7
Q
Sevoflurane
A
- inhaled general anesthetic
- low blood solubility –> rapid on/offset
- potent: MAC 2%
- less irritating to the respiratory tract
Problems:
- 3% of a dose is metabolized but while plasma F increases, there are no reports of kidney or liver toxicity
- was degraded in carbon dioxide absorbers (inhalation apparatus) to olefin which is nephrotoxic. nowadays, new inhalation apparatuses are used that won’t cause this.
8
Q
Thiopental
A
- IV general anesthetic
- Barbiturate aka derivative of barbituric acid
- placed in alkaline solution, must be injected slowly
- short duration after single dose
- potent anesthetic but poor analgesic
- mechanism: potentiate the inhibitory effects of GABA
Effects during stage 3 surgical anesthesia:
- little serious effect on the heart or vasculature in the absence of hypercarbia or hypoxia
- reduces cerebral blood flow and intracranial pressure, good for neurosurgery
Recovery/Toxicity:
- post-op shivering, pain
- contraindicated in variegate or acute intermittent porphyria, otherwise will experience irreversible demyelination/nerve damage
- post surgical muscle pain when combined with depolarizing blocker like succinylcholine
- liver metabolism, cross tolerance with ethanol
- ion trapping for overdose – alkalinize the blood or urine
9
Q
Benzodiazepines
A
- IV general anesthetic
- Diazepam, Lorazepam, Midazolam
- antidote = flumazenil
- causes sedation, reduction of anxiety, and amnesia
- used alone when analgesia is not required
- not analgesic
- severe CV and resp depression when combined with opioids
- used to control seizures brought on by local anesthetic techniques
- mechanism: potentiate the inhibitory effects of GABA
10
Q
Flumazenil
A
antidote for benzodiazepines (diazepam, lorazepam, midazolam)
11
Q
Propofol
A
- IV general anesthetic
- more rapid in action than barbiturates
- not an analgesic, may be antiemetic
- metabolized in the liver and extra hepatic pathways; half life is less than thiopental so cleared faster
- more neg inotropic effect on the heart than thiopental
- allergic reaction associated with vehicle
- expensive
- mechanism: potentiate the inhibitory effects of GABA
12
Q
Picrotoxin aka PTX
A
- neurotoxin
- agonist to GABA receptor
13
Q
Etomidate
A
- IV general anesthetic
- sedative/hypnotic, not analgesic
- high safety index
- widely used in emergency settings for Rapid Sequence Induction of anesthesia: give etomidate and muscle relaxant like succinylcholine or rocuronium to relax the oropharynx, larynx, and diaphragm (for rapid incubation of patients)
- minimal CV and resp depression
- very short duration of action
- causes nausea and vomiting if pt did not fast (which is often the case if used in emergency situations)
- pain on injection of glycol formulation
- myoclonus (rigidity of skeletal muscle)
- suppresses corticosteroid synthesis
14
Q
Ketamine
A
- IV general anesthetic
- drug of abuse
- causes dissociative anesthesia, sedation, immobility, amnesia, and analgesia
- mechanism of action: inhibits the NMDA type glutamate receptor
- may increase muscle tone
- good for trauma surgery since BP and resp are well maintained and heart rhythm is stable
- can be used to treat chronic pain (reflex sympathetic dystrophy - pain, swelling, vasomotor dysfunction of an extremity)
15
Q
Droperidol + Fentanyl
Brand name: Innovar
A
Neuroleptic/Opioid combo
Neuroleptic (Droperidol) = tranquilizing, adrenergic blocker having antiemetic and anticonvulsant effects
Opioid (Fentanyl) = short acting meperidine derivative 50-100 times more potent than morphine
Can be used alone or together
Problems:
- abuse potential
- Droperidol lasts longer than the fentanyl, may need booster to get analgesic effect of the opioid, which can lead to overdose with Droperidol
- can use for chest wall spasms. treatable with succinylcholine
- respiratory depression can be severe - must avoid in asthmatic, myasthenia or PD patients
