Anesthetic Agents

What is analgesia?

No pain

What are the inhaled anesthesia gases?

• Nitrous oxide

• Xenon

What are the vapor anesthetic gases?

• Sevoflurane

• Isoflurane

• Desflurane

• Halothane

What is general anesthesia?

Drug induced loss of consciousness during which patients are not arousable, even by painful stimulants

What is an inhalational agent?

Delivery of gases or vapors from the respiratory system to produce anesthesia

What is the purpose of inhaled agents?

Develop and maintain a partial pressure of anesthetic agent in the brain

What is the pathway for anesthetic uptake of inhaled agents?

Alveoli → pulmonary capillary → cell membranes → brain

What is MAC?

Minimum alveolar concentration - concentration of inhaled anesthetic that prevents movement in 50% of patients in response to surgical stimulation

How does higher blood solubility influence uptake of anesthesia?

Slower uptake

How does lower solubility influence uptake of anesthetic gases?

Faster uptake

How does potency affect solubility?

Increases solubility and lowers MAC value

If solubility is high how does it influence MAC?

Lowers MAC value

If solubility is low how does this impact MAC?

Increases MAC value

What is the most potent inhaled vapor?

Halothane (MAC = 0.75)

Does nitrous oxide have low or high potency?

Low

What is the function of isoflurane?

• Controls BP

• Reduced MAP and SVR

• Muscle relaxant

• CNS Depressant

What is uptake of isoflurane?

Fairly slow

What is the uptake for sevoflurane?

Rapid

What can be used to help control high pressures?

Anesthesia

When does most awareness occur during CPB?

During rewarming, maintain at least 0.5 MAC of agent

What is MH?

Malignant hyperthermia

What can trigger malignant hyperthermia?

• Halothane

• Isoflurane

• Sevoflurane

• Desflurane

• Succinylcholine

What are characteristics?

• Inherited component (dominant)

• Defect in calcium reuptake

• Intracellular calcium increases 500 fold

How do you treat malignant hyperthermia?

• Stop all triggering agents

• 100% oxygen

• Dantrolene

• Sodium bicarb

What is the function of dantrolene?

Inhibits intracellular calcium ion flux, inhibits excitation-contraction coupling

What is dose of dantrolene?

2.5 mg/kg or up to 10 mg/kg

What is classification of propofol?

Sedative/hypnotic agent

When is propofoleliminated?

2-20 hours

Where is propofol metabolized?

Liver by cytochrome P-450 system

How is propofol eliminated?

Renal

What is the mechanism of action for profol?

Binds Gaba alpha receptor

What effect does propofol have on the cardiac system?

• Decreases SVR, CI, SV

• SBP decreases 15-40%

• Depression og baroreceptor reflex

What effect does propofol have on respiratory?

Depresses the system

What effect does propofol have on CNS?

• Decreases cerebral blood flow

• Decreases ICP

What are narnotirates

Class of prescription medications that act as central nervous system depressants to slow down brain activity

What is the mechanism of action for barbiturates?

Binds GABA alpha receptor to cause dose-dependent suppression of CNS activity - decreases cerebral metabolic rate

What is the most commonly used barbiturate?

Thiopental

When are barbiturates used?

• Treats increased ICP

• Given prior to circ arrest for cerebral protection

How do Barbiturates affect cardiac?

• Venous pooling

• Decrease CO

• Increase HR

• Myocardial depression

What are barbiturates not compatible with?

Acidic drugs (opioids, catecholamines, neuromuscular blocking agents)

What are the different benzodiazapines?

• Midazolam - Versed

• Lorazapam - Ativan

• Diazapam - Valium

What is mechanism of action for benzodiazapines?

Binds to GABA alpha and enhance affinity of GABA to receptor

What is most commonly used benzodiazapine?

Midazolam

How does midazolam effect cardio system?

Cause peripheral vasodilation

Which benzodiazapine is long lasting?

Diazepam

How do benzos effect respiratory system?

Decreased response to increased CO2

What is antagonist for benzos?

Flumazinil (Romazicon)

What is function of etomidate?

Induction of anesthesia

What causes etomidate to become inactive?

Hydrolysis by esterases

What is the effect on cardiac on etomidate?

• Preserves myocardial contractility

• SV, LVEDV, and contractility are unchanged

• Respiratory depression

How does tomidate effect CNS?

Decreases ICP

What is function of etomidate on endocrine?

Adrenal suppression

What is the function of ketamine?

Analgesia and amnesia with minimal effect on respiratory function

What is the byproduct when ketamine is broken down?

Norketamine - 1/3 biologically active

What is mechanism of action for ketamine?

NMDA receptor antagonist - blocks glutamate - mu receptor

How does ketamine effect cardiac?

Increase BP and HR

How does ketamine effect CNS?

Increase ICP

How does ketamine effect respiratory system?

Bronchodilation and salivation