nitrous oxide, halothane, enflurane, isoflurane, desflurane, sevoflurane

-high lipid solubility

-NO - inhibit NMDA receptors, activate K channels

-effects due to differential sensitivity of cell populations to drugs

Partition coefficient - relative conc of a substance in two different mediums

-high partition coefficient ->slower effect - higher solubility in blood - also longer recovery time

[desflurane, sevoflurane, NO]<[isoflurane, enflurane, halothane]<methoxyflurane

Minimum alveolar concentration - % of alveolar concentration to prevent response in 50% of patients

>95% of patients respond to 1MAC

-lower for elders and infants

-MACs are additive

-All except NO cause decrease in arterial pressure

-enflurane, halothane - myocardial depression

-isoflurane, desflurane, sevoflurane decrease PVR

-isoflurane - dilate coronaries - coronary steal

-Enflurane, isoflurane - increase HR. Halothane decreases

-Halothane-arrhythmias due to sensitization of myocardium to catecholamines

-All reduce myocardial O₂ consumption

Other organ effects for anesthetics

Respiratory - except NO, depressants, blunt responses to CO₂ and hypoxia - even at low conc

Brain - decrease metabolic rate, increase cerebral blood flow - bad for high ICP. Halothane worst.

Kidney - decrease GFR, effective plasma flow, increase filtration fraction, renal vascular resistance

Liver - decrease hepatic blood flow. Halothane can cause hepatitis

Malignant hyperthermia - ryanodine receptor - fix with Dantrolene

Thiopental-respiratory depression, myocardial depression, decreases cerebral blood flow - best for pts with high ICP

Benzos-midazolam, causes anterograde amnesia

Opioids-alfentanil, remifentanil-pain control, causes respiratory depression

Propofol-GABA_A, glycine-rapid onset, short half life-patients feel better after. Respiratory depression, decrease PVR, increase TG

Etomidate-few side effects, fast-acting. nausea, myoclonus, cortisol suppression. Redistributed.

2 Types of local anesthetics

General action of anesthetic

Esters and amides, Amides - two "i"s

Esters have shorter duration of action

Drug must be neutral to cross cell membrane, but charged to bind to Na⁺ channel->work poorly in acidic infected tissues

-binds to open and inactivated sodium channel

Small diameter, myelinated, high-frequency firing, position on outside of nerve bundle

Absorption: combined with epinephrine to prevent distribution - amides tend to distribute to well-perfused areas.

Esters quickly hydrolized, amides metabolized by CYP450

Local anesthesia

Tachyphylaxis - slow infusions and multiple injections correlated with loss of effectiveness

Duration:

procaine<lidocaine, mepivacaine, prilocaine <tetracaine, bupivacaine, ropivacaine, etidocaine

Cocaine used for nose and throat

CNS: sleepiness, lip tingling, visual/auditory changes, seizures

PNS: toxic to nerve tissue

Cardiac: arrhythmias, hypotension (cocaine: vasoconstriction, HTN). Bupivacaine and ropivacaine are more cardiotoxic

Blood: Prilocaine->methemoglobinemia

Allergic reactions:esters metabolized to pamaniobenzoic acid