General & Local Anesthetics Flashcards
What is a drug-induced reversible depression of the CNS resulting in loss of response to and perception of all external stimuli?
General anesthesia
What is a drug-induced state during which px respond normally to verbal commands?
Mnimal sedation (anxiolysis)
What are the stages of anesthesia?
- Stage 1 = Amnesia & Analgesia
- Stage 2 = Delirium/Disinhibition
- Stage 3 = Surgical stage
- Stage 4 = Respiratory paralysis (should not be reached)
How is respiration in the earlier stages of Anesthesia?
errratic or rapid in earlier stages & slow to shallow as it progresses to 3rd
What happens to eyeball movement in the stages of anesthesia?
greatest in stage 2, lesser in stage 3 (1st plane)
What happens to pupillary sizes in the stages of anesthesia?
pupils more dilated as px becomes more sedated
What are the diff anesthetic techniques?
-
Balanced anesthesia:combi of anesthetics & techniques to selectively direct components of anesthesia (inhaled & IV anesthetics)
Total IV Anesthesia:**only IV gen anesthesia
**Monitored Anesthesia care: Local anesthesia + oral/parenteral sedatives/anesthetic agents + monitoring of the px
*IV induction: IV + monitor + rapid acting IV anesthetic for induction
What are the 2 types of inhaled anesthetics?
Volatile = Low vapor pressure, high boiling pt, liquid @RT (halothane, enfluoprane, isoflurane, desflurane, sevoflurane
Gaseous = high vapor pressure, low boiling point, gas @ RT (Nitrous oxide, Xenon)
In the elimination of anesthetics, what is the metabolic hierarchy of the diff inhaled anesthetics?
(Most to least metab)
Halothane > Enflurane > Sevoflurane > Isoflurane > Desflurane > N2O
Is N2O metabolized in humans?
no, but bacteria in our GIT can break them mdown
What is the minimum conc of anesthetic in the alveoli that prevents movement in response to surgical stimulation in 50% of px?
Minimum alveolar concentration (MAC)
What is the measure of anesthetic potency?
lower the MAC, more potent agent
higher the MAC, less potent the agent
What is the ratio of dissolved gas (by volume) in** 2 tissue compartments** at equilibrium?
refers to solubility also
bloodg gas partition coefficient
what is the rel of anesthetic solubility in blood to rate of rise?
the less soluble it is in the blood, the faster the rate of rise of the inhaled anesthetic to alveolar gas -> faster px falls asleep –> INC conc in brain
Which of the anesthetics is not used clinically anymore bcos of its nephrotoxicity effect?
Methoxyflurane
What is the most potent anesthetic?
Halothane (lowest MAC)
What are the diff Blood:gas partition coefficient rel?
- **Higher PC **= Higher solubility = Slower induction = Longer effect
- **Lower PC **= Lower solubility = Faster induction = Shorter effect
What are the effects of anesthetic to the CNS?
- DEC cebral metab rate -> DEC cerebral blood flow
- <1 MAC = no vasodilation
- > or equial to 1.5 = vasodilation
- DEC PaCO2 via hyperventilation -> cerebral vasocontriction
- NO2 = INC Cerebral blood flow
What are the effects of anesthetic to the CVS?
- Myocardial depression -> DEC arterial BP (Halothane & Enflurane)
- Peripheral vasodilation min effect on CO so good for px with cardiac failure (Isoflurane, Desflurane, Sevoflurane)
- N2O: slight myocardial depression & SNS activation -> preserves CO
- Baroreceptor reflex (DEC BP, INC HR): Depressed: Halothane, Enflurane, Sevoflurane
Unaffected: Isoflurane, Desflurane
* DEC myocardial O2 consumption
What are the effects of anesthetics to respiration?
- Bronchodilating
-
Pungency of Isoflurane & Desflurane (irritating)
Respiratory depression: DEC response to CO2, INC apneic threshold - DEC Mucocillary functions: mucus plugging -> atelectasis, pulmonary infection
What are the effects of anesthetics to the kidneys?
- DEC GFR, urine flow
- DEC renal blood flow, INC filtration fraction
- depends on minor or major surgery
- resversible on discontinuation of anesthetic
What are the effects of anesthetics to the liver?
- Concentration-dependendent DEC of portal blood flow
- Hepatic artery flow may INC & preserve total hepatic blood flow
- transient changes in liver enzymes
What are the effects of anesthetics to the uterine smooth muscle?
- concentration-dependent uterine relaxation
- profound uterine relaxation at higher dose of inhaled anesthetic & is necessary if intrauterine manipulations, extraction of retained placenta, bleeding after delivery under GA
What are the sites of anesthetic targets of Inhaled anesthetics?
INC inhibitory synaptic activity - mediated by GABA
DEC excitatory activity - mediated by Glutamate
What are the 3 principle components of anesthetic action?
Immobility = Minimum alveolar concentration
Amnesia = explicit and implicit memories, prevented at 0.2-0.4MAC
Unconsciousness = reversible blockade
What are the types of toxicity that can occur with inhaled anesthetics?
Nephrotoxicity
Hematotoxicity = CarboxyHgb, Megaloblatic anemia
Malignant hyperthermia
Hepatotoxicity = Halothane hepatitis
Mutagenicity, Teratogenecity
What triggeers Malignany hyperthermia?
All inhalational anesthetics except for N2O & Succinylcholine
What are clinical syndromes assoc with Malignany hyperthermia?
INC sympathetic activity
INC CO2 production
Muscle rigidity, fever as high as 43C
INC metabolic state
What are tx for Malignany hyperthermia?
Remove trigger agent
Support vital functions
Lower body temp
What is the DOC for Malignant hyperthermia?
Dalontrene
What is the MOA of Dantrolene?
Interferes with releae of Ca from the SER via ryanodine receptor channel
Prevents excitation-contraction coupling
What are the AEs of Dantrolene?
Muscle weakness, sedation, occasional hepatitis
Cardiac smooth muscle depressed slightly
Spasmolytic
What are the different IV aneshtetics?
Thiopental
Propofol
Etomidate
Ketamine
Dexmedetomidine
What is the ultra-short acitng IV anesthetics?
Thiopental
Used in execution chambers for convicts in death row
What is the most widely used IV anesthetic?
Propofol
What is the phenomena experienced in Propofol?
Excitatory phenomena
What IV anesthetic maintains hemodynamic stability, cerebral protection, temporary inhibition of steroid synthesis in adrenals?
Etomidate
What IV anesthetic causes dissociative amnesia?
Ketamine
What is the MOA of Ketamine?
Mainly NMDA receptor antagonist -> blocks membrane effects of the excitatory NT glutamate
What phenomena occurs with Ketamine?
Emergence phenomena = + postop disorientation, sensory & perceptual hallucinations, vivid dreams,nightmares
What IV anesthetic is an a2-adrenergic agonist where it maintains spotaneous respirations?
Dexmedetomidine
What are other uses of Dexmedetomidine?
- rapid opioid detoxification, cocaine withdrawal
- iatrogenic-induced benzodiazepine and opioid tolerance after prolonged sedation
What IV anesthetic’s effet is terminated by redistribution?
Etomidate
What are the 3 basic parts of local anesthetic?
Lipophilic grp
Intermediate bond
Hydrophilic group
What is an atypical local anesthetic?
Benzocaine
What prototype of amide is the most commonly used in PH and used as an alternative for px wtih PABA allergy?
Lidocaine
What metabolite formed from Esters can produce allergic reactions?
Para-aminobenzoic acid (PABA)
What enzyme is responsible for hydrolyzing the action of esters in the blood?
Butyrylcholinesterase
What are the 3 topical local anesthetics?
1.Benzocaine
2. EMLA (Eutectic mixture of LA ointment) Lidocaine + Prilocaine
3. Lidocaine (gel)
What is the MOA of local anesthetics?
Blockate of voltage-gated Na channels
What marine toxin is found in shellfish in “red tide” that causes paralysis?
Saxitoxin
What is added to local anesthetics?
Epinephrine
- to DEC rate of vascular absorption
- INC depth and duration of anesthesia
What are the effects of local anesthetics in CNS with low concentrations?
Sleepiness, light-headedness
Visual/auditory disturbance
Restlessness
What are early symptoms of CNS toxicity?
Circumoral
Tongue numbness
What are CNS effects of Local anesthetics in high conc?
Nystagmus
Muscular twitching
Tonic-clonic seizure
CNS depression
Death
What are othetr toxicities that can happen with admin of local anesthetics?
Neural toxicity
Transient neurologic symptoms: concentration dependent
What are the commonly used local anesthetics?
Articaine
Benzocaine
Cocaine
Bupivacaine
Levobupivacaine
Lidocaine
Ropovacaine
What are the different local anesthetics with Ester properties?
Cocaine
Procaine
Tetracaine
What are the diff local anesthetics with Amide compoentns?
Lidocaine
Bupivacaine
Prilocaine
