Anesthesia

In the “old days” the following were used for anesthesia.

– Alcohol– Drugs– Ice for numbing– Blow to the head– Strangulation

Anesthesia

Now, anesthesia is designed to focus on specific systems, such as

• Nervous system • Skeletal system• Respiratory system • GI system• Endocrine system • Hepatic system• Cardiovascular system

Anesthesia

Goals of Balanced Anesthesia– Amnesia (Loss of memory)– Adequate Muscle Relaxation– Adequate Ventilation– Pain Control

Types of Anesthesia• Preansthetics agents• General (inhaled: desflurane,

halothane, isoflurane, Nitrous oxide, sevoflurane, enflurane; IV:barbiturate, benzodiazepines, ketamine, opoids, propofol, etomidate)

• Local ( Bupivacaine, Lidocaine, Procaine, Tetracaine)

General Anesthesia

Preanesthetic Medications (antiemetics, muscle relaxants, Anticholinergics, antihistamines, Benzodazepines, Opioids)– Control sedation– Reduce postoperative pain– Provide amnesia– Decrease anxiety

Discussion

What are some of the indicators used to access general anesthesia?

Answer: Blood pressure, hypervolemia, oxygen level, pulse, respiratory rate, tissue perfusion, urinary output

General Anesthesia

Malignant Hyperthermia– Side effect of anesthesia

• Fever of 110°F or more• Life threatening

– Treatment: dantrolene (Dantrium)

Inhalant Anesthetics

• desflurane (Suprane)• enflurane (Ethrane)• halothane• isoflurane (Forane)• nitrous oxide

Drug List

Inhalant Anesthesia Side Effects

• Causes reduction in blood pressure• May cause nausea and vomiting

nitrous oxide

• Causes analgesia only; no amnesia or relaxation

• May be given alone or may be given with more powerful anesthetics to hasten the uptake of the other agent (s)

• Commonly used for dental procedures• Rapidly eliminated

desflurane (Suprane)

• Has rapid onset and recovery

• Often used in ambulatory surgery

Intravenous General Anesthesia

• Often dispensed by IV drip• Very lipid soluble

Injectable Anesthetics

• etomidate (Amidate)• fentanyl (Duragesic, Sublimaze)• fentanyl-droperidol• ketamine (Ketalar)• morphine• propofol (Diprivan)• sufentanil (Sufenta)

Drug List

Injectable Anesthetics

Barbituates– methohexital (Brevital)– thiopental (Pentothal)

Benzodiazepines– diazepam (Valium)– lorazepam (Ativan)– midazolam (Versed)

Drug List

propofol (Diprivan)

• Used for maintenance of anesthesia, sedation, or treatment of agitation

• Has antiemetic properties– Drowsiness– Respiratory depression– Motor restlessness– Increased blood pressure

fentanyl

• Dosage Forms– IV – patch– lozenge for children

• Used extensively for open-heart surgery due to lack of cardiac depression

Benzodiazepines

• Used for induction, short procedures, and dental procedures

• Useful in controlling and preventing seizures induced by local anesthetics

• midozolam (Versed) – fastest onset of action– greatest potency– most rapid elimination

Antagonist Agents

Antagonist agents reverse benzodiazepine and narcotic overdose.

Antagonist Agents

• flumazenil (Romazicon)• nalmefene (Revex)• naloxone (Narcan)

Drug List

Neuromuscular Blocking Agents• Causes immediate skeletal muscle

relaxation. – Short Duration– Intermediate Duration– Extended Duration

• Used to facilitate endotracheal intubation. – Allows for easier insertion of endotracheal

tube.– Keeps airway open.

Neuromuscular Blocking Agents

• atracurium (Tracrium)• cisatracurium (Nimbex)• mivacurium (Mivacron)• pancuronium• rocuronium (Zemuron)• succinylcholine (Quelicin)• vecuronium (Norcuron)

Drug List

succinylcholine (Quelicin)

• Often called “sux.”• Only depolarizing agent. All others work as

competitive antagonists to ACh receptors.• Persistent depolarization at motor endplate.• Causes sustained, brief period of flaccid

skeletal muscle paralysis.

Reversal of Neuromuscular Blocking Agents

• Increases the action of acetylcholine by inhibiting acetylcholinesterase

• Used for reversal of nonpolarizing agents

Anticholinesterase Agents

• edrophonium (Enlon)• neostigmine (Prostigmin)• pyridostigmine (Mestinon)

Drug List

Local Anesthesia

Relieves pain without altering alertness or mental function.

Local Anesthesia

Variety of Dosage Forms– Topical– Superficial injection (infiltration)– Nerve block– IV– Spinal

Under what conditions would a local anesthetic be used over a general

anesthetic?

Answer: It is chosen when a well-defined area of the body is targeted.

Discussion

Local anesthetics are classified by their chemistry into two classes. EsterAmides

Local Anesthesia

Esters– Short acting– Metabolized in the plasma and tissue fluids– Excreted in urine

Local Anesthesia

Amides– Longer acting– Metabolized by liver enzymes– Excreted in urine

Local Anesthesia

Esters• benzocaine (Americaine)• chloroprocaine (Nesacaine)• dyclonine (Cēpacol Maximum Strength)• procaine (Novocain)• tetracaine (Cēpacol Viractin, Pontocaine)

Drug List

Local Anesthesia

Amides• bupivacaine (Marcaine)• levobupivacaine (Chirocaine)• lidocaine (L-M-X, Solarcaine, Xylocaine)• lidocaine-epinephrine (Xylocaine w/ Epinephrine)• lidocaine-prilocaine (EMLA)• mepivacaine (Carbocaine)

Drug List

What functions are lost with local anesthetics?

Answer– Pain perception– Temperature– Touch sensation– Skeletal muscle tone