Anesthesia Flashcards
Define general anesthesia.
CNS depressant characterized by its ability to cause loss of consciousness, loss of sensation and adequate muscle relaxation.
What are the stages of GA?
4 stages:
- Stage of analgesia or induction
- Stage of excitement and delirium with dilated reactive pupil
- Stage of surgical anesthesia with normal pupil
- Stage of medullary paralysis with dilated nonreactive pupil.
How does N2O and ketamine induce GA?
By decreasing NMDA receptors of glutamate.
How is chloroform different from other anesthetics?
It stops respiration with circulation while most anesthetics stop respiration before circulation.
What does the onset of a GA depend on?
Solubility in blood or blood/gas partition coefficient. The less soluble, the more rapid its induction and recovery. Examples: N2O has low solubility hence its rapid onset. While methoxyflurane has high solubility hence its delayed onset.
Mention 2 benefits of halothane.
It has bronchodilator action so useful in bronchial asthma, it causes controlled hypotension so provides a bloodless field of work.
What are the disadvantages of halothane?
Weak muscle relaxant and weak analgesic Cardiotoxic Hepatotoxic Causes malignant hyperthermia Uterine relaxant.
Mention an advantage of N2O in labor.
Good analgesic in labor.
What’s diffusion hypoxia? What causes it? And how to overcome it?
It occurs during recovery from N2O due to diffusion of N2O which is poorly soluble in blood which decreases O2 conc. In alveoli causing hypoxia.
N2O causes it.
It can be overcome by giving oxygen during recovery.
What are the disadvantages of N2O?
Weak anesthetic Weak skeletal muscle relaxant Diffusion hypoxia Megaloblastic anemia Teratogenicity
What’s the difference between methoxyflurane and other fluranes.
Methoxyflurane is cardiotoxic and nephrotoxic while other fluranes are less or not cardiotoxic.
What’s the relation between oil/gas partition coefficient and MAC?
The higher the o/g partition coefficient the lower the MAC, which means the more potent the anesthetic is.
Methohexital is preferred sometimes.
Because it has little effect on blood pressure.
Thiopental should never be mixed with succinylcholine. Yes or No?
Yes because it’s highly alkaline and succinylcholine is acidic.
What causes dissociative anesthesia?
Ketamine.
What increases all pressures and is contraindicated in glaucoma?
Ketamine.
What causes emergence phenomenon?
Ketamine.
Which anesthetic has antiemetic effect?
Propofol
Which anesthetic is given only to patients with coronary or CVS disease?
Etomidate.
What anesthetic causes adrencortical suppression?
Etomidate.
What anesthetic has selective alpha2 agonist effect?
Dexmedetomidine.
What’s used instead of atropine and gallamine in thyrotoxic patients?
Hyoscine instead of atropine
Curare instead of gallamine.
Which LA useful only by injection?
Procaine
How are esters metabolized? And what’s the exception?
By plasma pseudocholine esterase. Except cocaine which is metabolized by HME.
What’s the sequence in which nerve fibers are affected by LA?
Sensory, cold, touch, pressure then motor.
And unmyelinated before myelinated.
Inflammation decreases the action of LA. Why?
Because it causes acidosis which decreases the action of LA.
Calcium antagonizes the action of LA while Potassium enhances it. Yes or No?
Yes.
What anesthetic causes methemoglobinemia?
Prilocaine.
PABA ester anesthetics shouldn’t be given with sulfonamides. Why?
Because they’re metabolized into PABA which antagonizes the effect of sulfonamides.
Noradernaline shouldn’t be given to patients with hypertension but can be given with anesthetic to thyrotoxic patients. Yes or No?
Yes
