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Details

General and Local Anesthetics
Inhalants, IV and locals
29
Medical
Graduate
04/23/2010

Additional Medical Flashcards

 


 

Cards

Term

 

 

Factors that Increase MAC

 

 

Definition

HASHI needs more than 1 MAC

 

Hyperthermia

Alcohol abuse (chronic)

Sodium (hypernatremia)

Hyperbaric pressure

Increased central neurotransmitters

Term

 

 

Factors that Decrease MAC

Definition

Less than 1 MAC makes you SHOP HAHA

 

Sodium (hyponatremia)

Hypothermia

Opioids

Pregnancy

Hypoxia

Alcohol (acute)

Hypovolemia

Age

Term

 

 

Nitrous Oxide

Definition

Inhaled general anesthetic.  Inorganic gas that is less potent than other inhaled anesthetics (MAC = 104%).  Commonly used in combination with other agents because high solubility makes it very easy to control.


Causes direct myocardial depression, and is a mild sympatomimetic.  Increases CBF and ICP by vasodilation. 


AE include decreased methionine synthetase and granulocytopenia

Term

 

 

Isoflurane

Definition

Inhaled general anesthetic that is a halogenated ether (decreases flammability).  MAC = 1.17%. Positive chronotrope and negative inotrope, that also causes vasodilation and increased HR.  Also acts as a bronchodilator.  Little effects on CBF. 


AE include cardiac ischemia due to positive chronotropy.  DOES NOT CAUSE ARRHYTHMIAS OR HEPATOTOXICITY COMPARED TO HALOTHANE

Term

 

 

Desflurane

Definition

Inhaled general anesthetic that is a halogenated ether (reduces flammability).  MAC = 6.6%.  Causes significant SYMPATHETIC STIMULATION if [] increases too rapidly. 

 

AE include being extremely volatile and needing a special inhaler.  Also is very irritating.  Non-flammable and does not cause hepatotoxicity

Term

 

 

Sevoflurane

Definition

Inhaled general anesthetic that is a halogenated ether (decreases flammability).  Similar to desflurane, but is MUCH LESS IRRITATING TO THE AIRWAY!!  Also acts as a bronchodilator and vasodilator and decreases HR.

 

AE include possibility of renal injury, but generally very safe.

Term

 

 

Thiopental, Thiamylal, Methohexital

Mechanism of Action and Elimination

Definition

Barbituate IV general anesthetics with a binding site on the GABAA receptor Cl- channel.  This functions to decrease GABA dissociation from the receptor and, at higher concentrations, to activate the Cl channel autonomously.  Dosing based on BMI, age, and volume status


Rapidly mixes with the central blood pool and eliminated by redistribution.  With prolonged infusion, uptake by fat and clearance play increasing roles in the elimination

Term

 

 

Barbituate Organ System Effects

Definition

CNS - Increased pain sensitivity in sub anesthetic [], decreased CBF, central O2 consumption, and ICP


CV - Venodilation (↓VR, ↓SV), ↓Contractility, Does not change SVR/MAP


Respiratory - Causes respiratory depression, and can lead to hypercarbia and hypoxemia

Term

 


Barbituate Side Effects

Definition

When giving IV barbituates, you have to TAPE the syringe

 

Thrombosis/phlebitis

Anaphylaxis (non-IgE)

Porphyria (problems in heme synthesis)

Excitatory phenomena (rare)

Term

 

 

Midazolam, Lorazepam, Diazepam

Mechanism and Pharmacokinetics

Definition

Benzodiazapenes that act on the GABAA receptor to increase chloride conductance, but require the presence of GABA to function.  As receptor occupancy increases, anesthetic effects increases. Termination primarily via redistribution.  Must be used as adjuncts to other anesthetics


Duration of action:

Diazepam>Lorazepam>Midazolam

Term

 

 

Benzodiazapene Organ

System Effects

Definition

CNS - Decreases cerebral O2 consumption, CBF, and induces ANTEROGRADE AMNESIA


CV - Minimal effects when used alone (additive effects with others), ↓BP with ↓SVR, does not block sympathetic response to noxious stimuli (get reflex tachy and HTN)


Respiratory - Central respiratory depression with increasing dose and apnea

Term

 

 

Benzodiazapene Side Effects

Definition

 

Venous irritation at injection site

 

Prolonged post-operative sedation (REVERSED BY FLUMAZENIL)

Term

 

 

Phencyclidines

Definition

 

Hallucinogenic IV general anesthetics that include LSD and PCP.  Ketamine is the only clinically used phencyclidine. 

Term

 

 

Ketamine Organ System Effects

and Elimination

Definition

CNS - Dissociative anesthesia (eyes open, reflexes intact), muscle activity intact, ↑CBF, O2 use and ICP.  Can induce seizures. Vivid dreams/agitation common in adult females


CV - Stimulates CV system (so useful in patients in shock), with increased HR, BP and CO.  ↑Myocardial O2 demand


Respiratory - Potent bronchodilator, so very useful in asthmatics, causes increased oral secretions

 

Elimination by hepatic metabolism and urinary excretion

Term



Side Effects of Ketamine

Definition

-Increased myocardial O2 demand makes it difficult to use in patients with history of MI/angina/CAD

-Seizure risk

-Cannot be used in Schizophrenia

-↑ICP can cause herniations

Term

 

 

Etomidate Organ System Effects

Definition

CNS - No analgesia, ↓CBF, CMRO2, and ICP, can induce seizures


Respiratory - Minimal effect on ventilation or bronchial sm m tone


CV - NO EFFECTS ON CV SYSTEM AT ALL, however, does not blunt sympathetic responses


Endocrine - Only one with endocrine, causes transient hypoadrenalism by inhibitng 11-β hydroxylase, resulting in decreased synthesis of cortisol and aldosterone

Term



Etomidate Side Effects

and Elimination

Definition

AE include:

Nausea and vomiting very common (must give anti-emetics)

Pain on injection (must administer lidocaine first)

Myoclonus (uncoordinated muscle fasciculations)


Termination due to redistribution, while elimination is via hepatic metabolism and produces inactive metabolite

Term

 

 

Propofol Elimination and Side Effects

Definition

Most popular and commonly used general IV anesthetic.


Termination by redistribution, while elimination is via hepatic conjugation to glucoronide and sulfate and renal excretion


AE include pain at injection site (must use lidocaine), myoclonus (less than etomidate), and contraindicated in hypovolemia

Term



Propofol Organ System Effects

Definition

CNS - Acts at GABAA Cl channels, but has no analgesic properties; ↓ICP and perfusion due to ↓BP


Respiratory - Dose related respiratory suppression, with apnea common, though does cause bronchodilation


CV - Veno and vasodilator causing ↓preload and afterload, as well as ↓myocardial contractility.  Cannot use in trauma patients

Term

 

 

General Use for Opioids

and Side Effect

Definition

Useful adjuvants to other anesthetics, that function to ↓MAC with inhaled anesthetics.  However, they do have a ceiling effect, and do not function as anesthetics themselves, because they have only analgesic properties (do not cause amnesia) so risk of recall exists.  Few CV effects and no organ toxicity


AE include non-specific CNS depression, some risk of anaphylaxis via histamine release, postoperative respiratory depression, and chest wall rigidity (especially with fentanyl)

Term

Anesthetics for:

1) Routine Induction

2) Asthmatics

3) Hypovolemia

4) Myocardial Dysfunction

5) Continuous infusion

6) Porphyria

Definition

 

1) Routine Induction - Propofol, (thiopental)

2) Asthmatics - Bronchodilators Ketamine or Propofol

3) Hypovolemia - Ketamine, Etomidate, or Midazolam

4) Myocardial Dysfunction - Etomidate, Midazolam, or Fentanyl

5) Continuous Infusion - Propofol, ketamine (give lidocaine with both)

6) Porphyria - Propofol

Term

 

 

Local Anesthetic Additives

(name 4 and benefits)

Definition

Epinephrine - Prolongation of block with local dosing, avoidance of cardiotoxic effects

Bicarbonate - LA are weak bases, so addition of HCO3 brings pH closer to pKa and makes more in unionized (active) form

Opioids - Can have additive analgesic effects with LAs, therefore allowing lower dosing of both agents, avoiding toxicity

Alpha 2 agonists (clonidine) - Act synergistically with LAs providing peripheral/neuraxial blocks.  No neurotoxicity.  Allow lower dosing

Term

 

 

Lidocaine

(Local Anesthetic)

Definition

Most widely used amide local anesthetic for topical, nerve block or epidural.  Can be used for spinal block, but induces neurotoxicity at high doses.  Moderately rapid onset and duration; prolonged by addition of a vasoconstrictor (which also reduces toxicity). 


Specific toxicities associated with respiratory depression and cauda equina syndrome. 


Secondary use for ventricular arrhythmias

Term

 

 

Bupivacaine and Levobupivacaine

(Local Anesthetic)

Definition

Longer duration amide local anesthetics that have greater sensory blockade than motor, making it ideal for epidurals during labor to allow movement with no sensation (walking anesthesia).  Also commonly used for spinal anesthesia.

 

Some risk of cardiotoxicity (torsades de pointes)

Term

 

 

Ropivacaine

(Local Anesthetic)

Definition
Bupivacaine analogue that is less cardiotoxic and has same duration of action.  Functions as a walking epidural, with less motor block than sensory block, but may be less potent than bupivacaine, requiring higher doses
Term

 

 

Mepivacaine

Definition

 

Amide local anesthetic similar to lidocaine, with minimal vasodilation, so similar in effects to lidocaine + epinephrine.

Term

 

 

Chloroprocaine

Definition

Ester local anesthetic with rapid onset and short duration of action, giving it a minimal toxicity profile due to rapid elimination.  High pKa makes it highly ionized, but low toxicity profile allows high (sufficient) doses to be given. 

 

Commonly used early until more long-lasting anesthetics "kick in"

Term

 

 

Cocaine

(Local Anesthetic)

Definition

Opioid local anesthetic, unique in its vasocontrictor effects, and useful in anesthesia of nasal mucosa for intubation in the nose (prevents pain and bleeding).

 

Get similar effects with lidocaine + phenylephrine (α-1 agonist)

Term

 


Non-anesthetic Properties of LAs

(Mechanism and specific situations)

Definition

Decrease release of inflammatory mediators

Prevent PMN chemotaxis and migration

Inhibit widening of endothelial gap junctions

Reduce superoxide radical formation


Commonly used in:  Acute lung injury, asthma, burns, MI, and sepsis


Also used in brain injury/ischemia and proves to salvage more neurons

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