Analgesic but NOT anesthesia

MAC 104; Blood/gas 0.46; Low potency

Use: conscious procedures (dentistry); combined w/ other anesthetics; Drug of abuse in dentists

Properties: Low ptency for anesthesia; low solubility in blood, therefore rapid onset of action; adjuvant with other inhaled anesthetics to increase rate of induction; little respiratory depression; attenuates hypotension (When combined with other anesthetics) 

Toxicities: Euphoria, Diffusion hypoxia (more than 70%), chronic low level may cause peripheral neuropathy; decreased production of leukocytes and RBCs, causing megaloblastic anemia

DON'T use for eye sx!; use within 3 months of procedure may cause irreversible loss of vision

Inhaled: General anesthetic

MAC: 0.75; Blood/Gas: 2.54 (High, slow induction, rapid awakening)

Toxicities: Sensitizes heart to catecholamines; may cause arrhythmieas; HEPATITIS from repeated exposure; Malignant hyperthermia with succinylcholine!; BV dilation, BP drop, CO depression, relaxes uterus, Decrease renal BF, increase intracranial pressure

Malignant hyperthermia treated with Dantrolene

Metabolism: chlorine and bromine removed from halothane, generating toxic metaboites, may lead to immune response and hepatitis

Other drugs: 

Enflurane (Ethrane^®) - MAC 1.63; B/G 1.90: more rapid induction than halothane; muscle relaxation and analgesia; depresses respiration with increased concentration

Side effects: nausea, vomiting, shivering, uterine relaxation; Production of fluoride during metabolism may cause reversible kidney damage (rare)

Metabolism: releases fluoride ions that can theoretically cause kidney damage (rare)

Inhaled General Anesthetic

MAC 1.17; B/G 1.46

Use: neurosurgery; most commonly used inhaled anesthetic (low tox)

 Advantages: Low toxicity; Decreases BP; no hepatic or renal tox; easy to adjust depth of anesthesia (low B/G); no myocardium depression, no sensitization to catecholamines

Side effects: Resp. depression, uterine relaxation (high concentration); dilates cerebral vasculature (increased IC pressure!)

Inhaled GA

MAC 1.80; Blood/gas 0.69

Use: Children (low irritation), 

Induction and emergence are rapid; least airway irritation; increased IC pressure (minimized with hyperventilating pt); Safest dx for pts with CV disease

Metabolism: releases fluoride ions that can cause kidney damage (rare)

Advantages: Safest drug for pts with cardiovascular disease; renal and hepatotoxicity are rare

Degradation of sevoflurane by CO2 absorbents in anesthesia machines have produces haloalkene (compound A), whid has lead to kidney tox in rats, doesn't happen if machine is working properly.

Inhaled GA

MAC 6.6; Blood/gas 0.42

Use: Out-pt Sx; 

Rapid emergence; very pungent odor, irritates airways, NOT used for induction; BP decreased; HR increase; profound vent depression; increases IC pressure (prevented by hyperventilating pt); no liver or kidney tox

IV anesthetic; Barbiturate

Mechanism: binds GABA channel independent of GABA, increases duration of Cl- channel opening

Use: Induction of anesthesia (short, rapid action); little analgesia

Absolutely contraindicated in pts with acute intermittent prophyria (may cause demyelination of PNS or CNs)

IV anesthetic: Benzo

Mechanism: binds GABA channel and increases frequency of opening in the presence of GABA

Use: Preanesthetic; induction; short procedures (combinded with opioid);

Why used for anesthesia induction: causes sedation, anxiety relief and anterograde amnesia; can be reversed with flumazenil (Romazicon)

Effect: causes amnesia

reversed with flumazenil (Romazicon)

IV anesthetic: 

Use: DOC for most anesthetic procedures (rapid induction/fast recovery); induction and maintenance of anesthesia

Mechanism: Facilitates GABAergic transmission

Effects: Causes resp depression esp.w/ opioids; Decreased cerebral BF, metabolism, IC pressure

Safe for use in pregnancy; Anaphylactic reactions (from the albumin containing emulsion it's in); Burning/stinging at the injection site (given lidocain for this)

Side effects: severe resp depression especially with opioids, should not be used outside Sx and critical care; anaphylactic reactions (albumin emulsion); propofol infusion syndrome (PRIS) = metabolic acidosis, hyperlipidemia, rhabdomyolysis, enlarged liver

Advantages: Least likely to produce nausea and vomiting; induces anesthesia as quickly as thiopental but emergence is 10X faster; Decreased cerebral bf/metabolism/IC pressure make it useful in neurosurgery; safe in pregnancy

Other drugs: ·      Etomidate (Amidate) - used when pt is at risk for hypotension; action in 1 min, duration = 5 min; very likely to cause nausea/vomiting

IV anesthetics

Mechanism: Blocks NMDA (glutamate) receptors

Type of anesthesia: Dissociative anesthesia (profound analgesia, no response to commands, amnesia w spontaneous respiration, limbs may move, eyes may be open); this is profound analgesia but not anesthsia

Useful for: Children; Vet med; pts at risk for bronchospasm or hypotension, date rape drug

Not used in adults because: Emergence delirium: bizarre dreams, hallucinations, even psychosis (reduced by benzos)

Effects: Catatonic state; potent analgesia; emergence delerium (add benzos), bizzare dreams, hyallucinations, even psychosis; dissociative anesthesia; profound analgesia; very little resp depression, increased BP

Date Rape drub; Drug of abuse

IV anesthetic: Opioid

Rapid onset, good analgesia; awareness if used alone so combo w/ midazolam

Use: children (pre-op lollipop to minimize anxiety and pain); 

Naloxone to reverse effects

Other drugs: ·      Sufentanil (Sufenta^®)

GA adjunct

Other drugs: Atropine