Neuroanatomy-General Anesthetics Flashcards
Halothane
Gas
Advantages
- None over other agents
- Big early advantage was not flammable
Disadvantages
- Decreases hepatic and renal blood flow
- Decreases blood pressure
- Sensitizes myocardium to catecholamines
- Hepatotoxic
- Causes arrythmias
Isoflurane
Gas (first good replacement for Halo..)
Advantages
- Good muscle relaxation
- Rapid recovery
- Stabilizes cardiac output
- No increase in intracranial pressure
- Does not sensitize myocardium to epinepherine
Disadvantages:
- none
Desflurane
Gas (similar to isoflurane)
Advantages
Disadvantages
- Requires special vaporizor
Sevoflurane
Gas
Advantages
- *- Relaxes bronchial smooth muscle- good for asthmatics**
- Rapid onset and recovery
- Non-irritating, can be used for mask induction in children
Disadvantages
- Potential renal toxicity at low flow rates
Nitrous Oxide
Gas
Advantages
- Good analgesia
- Rapid onset and recovery
- Relatively safe, nonirritating
Disadvantages
- Incomplete anesthesia (must be mixed with things)
- No muscle relaxation
- Must be combined with other , more potent anesthetics for surgical anesthesia
IV Anesthetics
Usually maintained with inhalation agents for long procedures or may be sole agent for short procedures.
- Recovery:
Occurs by redistribution from the brain into the other tissues eventually reaching high levels in adipose. (into muscle and fat)
It slowly diffuses out of these into the blood where the liver and kidney metabolize it
Recovery slows after repeated doses and metabolism and plasma clearance then become important
- Effect of Cardiac Output:
Elderly and other patients with decreased cardiac output divert more blood to the CNS to compensate for reduced flow
Thus more drug reaches the brain in these patients requiring caution in administration and reduced doses – want to reduce dose
Propofol
IV
Water-insoluble (egg or peanut alergies make patient not able to use this)
Michael Jackson’s death
Advantages:
- Reduces blood pressure and intracranial pressure without affecting myocardium
- Frequently used for outpatient procedures and sedation in intensive care units.
- Not likely to cause nausea
- Rapid onset
Disadvantages:
- Poor analgesia – usually need to mix with something
Fospropofol
IV - pro-drug of propofol (water soluable, slow effects by longer duration. ~4 min not 30 seconds, a big deal)
Barbiturates
- Ultra-short acting barbiturates such as thiopental and methohexital are used to induce anesthesia
- Effects occur in less than a minute but recovery is also quick and due to tissue redistribution
- Only about 15% is metabolized per hour
- Not analgesic and may cause hypotension
- Causes apnea, coughing, laryngospasm, bronchospasm and chest wall spasm
- Contraindicated in patients with a_sthma or with acute intermittent or variegate porphyria_ – can’t metabolize the agents.
Thiopental
Barbiturate
Advantages
- Rapid onset of action
- Potent anesthesia
Disadvantages
- Poor analgesia
- Causes significant nausea
- Little muscle relaxation
- Causes laryngospasm
Benzodiazepines
Alone: Quick acting and quick recovery. Patient is not completely out, but they don’t remember also.
- Used with other agents to increase sedation and amnesia in patients.
- Midazolam (versaid) is most frequently used but diazepam (recovery slower than versaid) and lorazepam are also used
- Minimal cardiovascular depression but all can cause respiratory depression
- Erythromycin inhibits benzodiazepine metabolism
- Amnesia is anterograde resulting in failure to place information in long-term memory.
Opioids
- Used to reduce amount of anesthetic by producing analgesia
- Fentanyly and its congeners sufentanyl and remifentanyl are most commonly used
- Not good amnesics and all cause respiratory depression
- Effects can be antagonized by naloxone or naltrexone – can treat overdose with these two.
Fentanyl
Opioid
Advantages
- Good analgesia
- More rapid acting than morphine
- Effects can be antagonized by naloxone
Disadvantages
- Respiratory depression
- Hypotension
- Muscle rigidity (opposite of what you want to accomplish)
Etomidate
- Hypnotic without analgesia used to induce anesthesia
- Not water-soluble but is produced in propylene glycol solution
- Rapid induction and short-acting
- *- Used for patients in shock and with coronary artery disease because it has little effect on the heart and circulation**
- Causes decreased plasma cortisol and aldosterone levels that can persist for 8 hours by inhibiting 11-beta-hydroxylase, should not be continually infused
- Can cause involuntary motions
Ketamine
Opioid
- Short-acting non-barbiturate anesthetic that causes a dissociated state; the patient is unconscious but may appear to be awake, does not feel pain.
- The dissociated state results in amnesia, sedation and immobility
- Ketamine works through the NMDA receptor and also stimulates central sympathetic outflow causing increased cardiac output and blood pressure
- *- Useful in asthmatics (no effect on bronchial tree), patients in shock but contraindicated in stroke and hypertension**
- Most widely used for short procedures in children and elderly
- Increases cerebral blood flow and frequently causes post-operative hallucinations (nightmares) in adults – biggest negative to this one.
Advantages
- Good analgesia
- Partial amnesia
Disadvantages
- Emergence phenomena (nightmares) particularly in adults
