Anesthetics

Front 1

MAC Value

Back 1

measure of anesthetic potency

minimal alveolar anesthetic concentration (% of inspired air) at which 50% of patients do not respond to surgical stimulus

MAC values are additive, lower in elderly pt's and in precence of opioid analgesics and sedative hypnotics

Front 2

Blood-gas solubility ratios

Back 2

the more soluble the anesthetic in the blood, the longer it takes to achieve partial pressure that will permit movement to CNS and other tissues

high ratio--slow onset, longer recovery rate (e.g Halothane)

Desflurane and sevoflurane have low solubility ratios--rapid onset and recovery

Front 3

Nitrous Oxide

Back 3

lowest potency. often used in combination. rapid onset and recovery

Front 4

Desfluranes

Back 4

Inhaled anesthetic

Desflurane--vasodilates, increases HR. Most rapid onset but airway irritation and coughing
low volatility---needs a special heated vaporizer

Front 5

Sevoflurane

Back 5

Inhaled anesthetic

decreased HR. Metabolized to F- ions--potential for renal damage. Rapid action

Front 6

Enflurane

Back 6

Inhaled anesthetic
decreased HR

SE: tonic clonic muscle spasms
Metabolized to F- ions--potential for renal damage.

Front 7

Isoflurane

Back 7

Inhaled anesthetic
Vasodilation, increased HR.
SE: Brochiolar secretions and spasms

Front 8

Halothane

Back 8

Inhaled anesthetic
Decreases HR directly, but sensitizes heart to catecholamines
SE: Hepatitis, malignant hyperthermia, cardiac arrhythmias

Front 9

Thiopental

Back 9

IV anesthetic

highly lipid soluble, rapid onset, short acting barbiturate

Front 10

Effects of inhaled anesthetics on CNS

Back 10

decrease the metabolic rate of the brain. Nevertheless, the more soluble volatile agents increase cerebral blood flow because they decrease cerebral vascular resistance. The increase in cerebral blood flow is clinically undesirable in patients who have increased intracranial pressure because of a brain tumor or head injury.

NO is least likely to cause increased blood flow

Front 11

Midazolam

Back 11

IV benzodiazepine, used for pre-op sedation & conscious sedation (anterograde amnesia). often used for colonoscopy

depresses respiratory function but can be reversed with BZ receptor antagonist--Flumazenil

Front 12

Propofol

Back 12

IV Anesthetic
Very rapid onset and recovery + antiemetic effect

used for outpatient surgery

Front 13

Fentanyl

Back 13

IV opioid analgesic used for anesthesia

chest wall rigidity with IV use

Neurolept anesthesia: Fentanyl, droperidol, NO

Front 14

Ketamine

Back 14

IV Anesthetic

rapid onset, short duration

causes dissociative anesthesia w/ amnesia, catatonia and analgesia

Only anesthetic that causes CV stimulation

SE: vivid dreams, hallusinations

Front 15

Mode of action of local anesthetics

Back 15

via infiltration near nerve bundles or by epidural/subarachnoid injection

bind to the inactivated Na+ channel in axonal membranes--block reactivation
2 Steps:
1.must cross lipid bilayer--non-ionized (if too acidic extracellularly, can decrease effect)
2. convert to ionized--binds Na+ channel

Front 16

Ester vs Amide local anesthetics

Back 16

Esters: have one "i" in their names (cocaine, procaine)

Amides: more than one "i" (lidocaine, bupivacaine)

Front 17

The order of nerve fiber sensitivity to anesthetic blockage

Back 17

small fibers more sensitive

type B & C> A delta> A beta/gamma> A alpha

Front 18

skeletal muscle relaxants

Back 18

interact with the nicotinic receptors at the skeletal muscle end plate

nicotinic receptors--comprised of five subunits--2 (alpha) bind ACh--open Na+ channels

most drugs bind to alpha subunits and prevent depolarization (competitive-nondepolarizing)
can be reversed w/ ACh inhibitors--neostigmine or pyridostigmine

Succinylcholine binds noncompetitively and opens Na+ channel causing excessive depolarization and desensitazion

cause progressive paralysis starting w/ muscles of eye and face--then limbs and resp. muscles.
No effect on cardiac or smooth muscle or consciousness

Front 19

Malignant hyperthermia

Back 19

life threatening syndrome associated with use of skeletal muscle relaxants (Succinylcholine, d-Tubocurarine)

symphtoms: Muscle rigidity, hyperthermia, HTN, acidosis, hyperkalemia

genotypic susceptibility:
ryonodine & L-Ca+ channels

Front 20

d-Tubocurarine

Back 20

blocks ANS ganglia and releases histamine--decreased BP, may cause bronchial secretion and bronchospasm, malignant hyperthermia

Front 21

Pancuronium

Back 21

competitive (non-depolarizing muscle relaxant)
more rapid onset and recovery
increased BP (vagolytic and sympathomimetic)

Front 22

Atracurium

Back 22

competitive (non-depolarizing muscle relaxant)

More rapid recovery and safer in hepatic or renal dysfunction because spontaneously inactivated--forms laudanosine which enters CNS--seizures

Front 23

Mivacurium

Back 23

competitive (non-depolarizing muscle relaxant)

very short duration--metabolized by plasma pseudocholinesterase, histamine release

Front 24

Succinylcholine

Back 24

Nicotinic receptor agonist muscle relaxant
Non-competitive (depolarizing)

Acts in two phases:
Phase I block (depolarizing)
following brief fasciculation--flaccid paralysis ensues, which is augmented, not reversed by ACh inhibitors

Phase II (desenziting)-- endplate repolarizes but the membrane is desensitized and remains unresponsive to ACh for some time before recovery

Short duration-- inactivated by plasma pseudocholinesterase

may cause hyperkalemia & hyperthermia

Front 25

Spasmolytics

Back 25

muscle relaxation caused by action of drug on CNS, spinal cord or muscle itself

used to reduce excessive muscle tone or spasm in acute muscle injury and CNS dysfunction (CP, MS, stroke)

usually no loss of muscle strength

Front 26

Baclofen

Back 26

Spasmolytic

facilitates GABA action by acting on direct agonist at GABA-b receptors in the spinal cord
*as effective as diazepam w/ much less sedation

Front 27

Dantrolene

Back 27

Spasmolytic
Blocks Ca2+ release from SR

acts directly on skeletal muscle to decrease contractability
useful in tx of malignant hyperthermia muscle rigidity