---start----
anesth
4/9/98
klein

a couple of more EKGs...
she was 
impressed that we did so well on the exam...

classical picture of 
something that is really important...this is a normal lead II EKG from a 
dog. This dog was given K+ while anesthetized to produce this pattern. 
when extracellular K+ rises, the T wave ets much bigger/taller and wider. 
a high amplitude peaked T wave means K+ is rising. also K+ affects 
resting membrane potentials, making them less negative, so that APs 
generated in those cells are very poor, and poorly conducted. atrial 
tissue is more likely to be affected and it can get unexcitable. now, we 
see sinus rhythm with no conduction through atrial muscle - no P wave, 
but there is a QRS that is wider than normal and starting to merge with T 
wave - because of asynchronous de/repolarization. with still more 
potassium, there is very wide QRS and eventually it turns into 
ventricular fibrillation.

goat with ruptured bladder. no P waves visible 
b/c very flat or atria are inexcitable. peaked T waves present. high ECF 
K+ in this goat. how to treat this goat? some membrane effects are from 
potassium...you could treat with bicarb if he is acidotic. otherwise, tx 
insulin and glucose. this fixed the problem.

more typical appearance of 
foal with ruptured bladder - now we just see P waves. we do not see 
peaked T waves and disappearance of P waves in these foals. shortly after 
anesthetic induction in foal with high K+ who had been treated with 
glucose and insulin, this pattern appeared. so, there is zero cardiac 
output - no ventricular contractions. CPR required, if possible with foal 
in dorsal recumbency with abdomen open. what else do you do? epinephrine. 
atropine is probably not useful to restore AV conduction. if there were 
an occasional dropped beat, you might try to use atropine but generally 
epi is chosen.

this hour should be relaxing, the rest of it.


endotracheal intubation:

used to control the airway, to deliver 
anesthetics. masks do not fit well on animal faces in general. some 
animals can be ventilated by mask but generally for PPV you must use an 
ET tube. may use ET tube for animal with collapsed larynx, head or facial 
trauma, blood in airway, emergency situations. also to protect airway 
from secretions, flushing solutions during dental work, etc. in the 
ruminant, to protect from aspiration during anesthesia as well - 
ruminants frequently regurgitate constantly during anesthesia.

slide: 
gavoun viper - very venemous snake - you wouldn't want it to wake up 
during your procedure, so it is intubated and anesthetized.  intubation 
is often done awake in nonvenemous snakes and other reptiles. induction 
is really slow b/c they do not breathe very quickly at all - can be 20 
min/half an hour. so if you can intubate and gently ventilate you will 
speed induction.

types of ET tubes:
some are better than others and 
usually more expensive:
these are all cuffed types:
red rubber: soft, 
atraumatic, old, tend to kink/rot, don't last as long - sometimes double 
cuffed for ruminants
human disposable plastic tubes: cheap, rugged, last 
long, stiff, somewhat traumatic. these have low volume cuffs. if you use 
a smaller tube than you would like to, you may need a lot of pressure in 
the cuff to make a seal, and that pressure can caues damage to the 
trachea. some plastics are bad....one plastic tube was used in a horse 
who required PPV, and there was a leak around the cuff, so they had to 
hyperinflate the cuff. at the end of the procedure, the horse started 
breathing again but couldn't move any air...they ventilated it ok but 
horse couldn't breathe off the ventilator. it turned out that when they 
deflated the cuff, the horse could breathe. but the cuff was so stiff 
that it was occluding the lumen of the tube during spontaneous 
ventilation, because the cheap plastic got soft at body temperature.

the 
best cuffed tubes are the easy to inflate ones with very compliant cuffs. 
they have large surface area so you do not need much pressure against the 
tracheal wall.

Magill tubes do not have little holes at the end
Murphy 
tubes have an eye at the end. in the event that the end of the tube is 
pushed against the wall of the trachea, animal can breathe through the 
eye.

uncuffed: for tiny animals, you can't use a cuffed tube, takes up 
too much room, no room for lumen of tube. not as good a seal:
Cole tube: 
made for human infants. uncuffed. narrow end of tube goes into trachea, 
"shoulder" creates a seal against the laryngeal opening. can provide a 
good seal if you use the right size of tube, you can ventilate using 
these. not as good at preventing aspiration. human Cole tubes are kind of 
long for our patients so we sometimes cut the ends off to reduce dead 
space. for a tiny bird these would be way too long. 
Cole tubes for large 
animals are pretty useless - not enough difference in diameter b/w the 
tip and main part of the tube, also they were made too short and ended 
way inside the horse's mouth, and also often the shoulder wasn't wide 
enough to seal against the laryngeal opening, and it would all slide in. 
really useless for ruminants.

other: armor tube - nonkinking wall with 
wire in it - good for sx on upper airway requiring intubation via 
tracheotomy site and weird tube placement. 
extralong tubes: for 
nasotracheal intubation in foals. a cuffed tube type. sometimes can 
intubate foals while awake. if foal will tolerate nasal intubation while 
awake you can use this tube, make a good seal with the cuff (horses have 
very unreactive airways so this doensn't bother them that much.) also 
used in adults when having surgery in the mouth. tubes need to be a bit 
longer than normal.

silicone cuffed tracheotomy tubes - for using 
anesthesia through trach site - can leave in place postop. has flange for 
tying or taping to neck. since it is cuffed, it will prevent blood or 
other material from upper airway from being aspirated during recovery.


many small animals are intubated usingg laryngoscopes.
blades:

curved: 
useful for cats, monkeys. placed at the base of the tongue beneath the 
base of the epiglottis (b/w tongue and epiglottis). base of tongue is 
depressed and pulled forward, flipping epiglottis down and forward.

straight: placed on top of epiglottis to pull it down and forward. must 
be gentle with this.  in most spp, this is more effective.
tiny blades: 
for tiny monkeys and kittens
big blades: swine, small ruminants 

all 
have same kinds of connectors, light source, batteries.

other equipment 
sometimes required: 

for animals with long, narrow mouths that do not 
open wide - a stylet to put into the tube to make it straighter or to 
change shape of curve. can make these out of wire hangers or kirshner 
wire or get them premade. you must not let stylet protrude from end of 
airway! commercially made ones have a stopper to prevent it from 
protruding out of the tube. however, the stopper occludes the lumen of 
the tube. the whole time you are trying to intubate, you are obstructing 
the airway. better to just bend your stylet so it can't go in further.


some aimals like monkeys, cats, small ruminants have very reactive 
larynges that close rapidly - not complete laryngospasm like in person, 
but more likely to flutter closed and get in your way. can spray larynx 
with local anesthetic - lidocaine via atomizer, or squirted in with 
syringe and needle, being careful not to poke larynx. best to use locking 
needle so you do not blow it off the end of the syringe. some people use 
q tips soaked in anesthetic - but that's suboptimal - stimulates larynx.

cetacaine: can of pressurized anesthetic - however, be aware of three 
problems - one, there are preservatives in here and some of them can 
cause irritation on the mucous membranes and some cats are very sensitive 
to this and have inflammatory responses. also the anesthetic in here is 
benzocaine which is not as safe as lidocaine and can be absorbed and 
cause methemoglobinemia - this is a documented response - and it is hard 
to control the dose that comes out, so if you accidentally spray too much 
on you can cause problems.

foal being intubated through nose - if you do 
a lot of these, you may want to use a laryngotracheal anesthesia kit- 
lidocaine in there, long plastic tube to put up the nose with tiny holes 
along it - so you can spray in lidocaine and get all the mms in the nose.


also you need: syringe to fill cuff, hemostat or stopcock to keep air 
from leaking back out if there isn't something built in, something to 
keep the mouth open - PVC with tape around it, or something else, to keep 
animal from chewing on the tube.

dr klein remarked on a story of a pony 
who bit down on his tube, occluded it, and got really really upset and 
started waking up, b/c he couldn't breathe...

there are also commercial 
specula to keep mouths open - especially useful when manually intubating 
large animals so you don't worry about losing your arm in there. routine 
bovine speculum is hinged, you put it in and manually open the mouth - 
useful for adult cattle, unfortunately is "one size fits all" though.

if 
anesthetizing an animal you need to know how wide the mouth can open. if 
facial trauma exists, or TMJ problems, more important.
remember anatomy. 
most domestic animals in resting position with mouths closed are 
breathing through the nose, and the soft palate is in front of the 
epiglottis. you have to dislodge the soft palate. this may occur when you 
pull the mouth open, extend the head, and put the laryngoscope in, or you 
might have to use the tube or laryngoscope blad to move it.

look for 
arytenoid cartilage and vocal folds and epiglottis. not just the opening 
b/w the arytenoids. 

slides:

you open the animal's mouth and look in 
and see soft palate and a little bit of epiglottis. you put in 
laryngoscope and press down - now epiglottis is in front of soft palate, 
but epiglottis isn't forward. so you use a flat blade and press down on 
epiglottis. we see arytenoids there, but not vocal folds. press down 
harder - now we see the vocal folds and a nice big diamond shaped lumen. 
you want to see these things before you intubate. you do not want to put 
the tube in the wrong place. you put it in and tie it in place - if there 
are no teeth to hold it in, you can tie to the back of the head. it is 
really important to be sure you are in the right place before you 
ventilate. 

if animal is breathing spontaneously, you can usually feel 
air coming out, and if tube is clear you can usually see it clouding with 
each exhalation. if animal is small or you aren't sure, you can hold hair 
or feather in front of the hole in the tube and see if it moves. if 
animal isn't breathing spontaneously, you may have to push chest to make 
a puff of air come out - a short, sharp air, not a big squoosh. a big 
squoosh can force air out of stomach and through tube, or push out rumen 
contents. if you aren't sure after that, you can palpate the neck, see if 
you feel the tube in the trachea. you can blow some air into the tube and 
watch the chest move, and see how it feels. stomachs accept air but do 
not send it back and do not feel elastic. exhale into the tube and see 
how it feels (if animal has no diseases you can catch). be careful, 
though. a little puppy here last week was ventilated into the stomach so 
much that he needed a stomach trochar to decompress it. this was a 
terrible accident. we don't know how this happened or who did it.

for 
ruminants that are also intubated laryngoscopically, there is an anatomic 
situation where mouth is long and narrow and larynx is down ventrally - 
you need to put a lot of pressure on the poll to create some dorsiflexion 
to straighten the airway,a nd also a stylet in the tube to make a curve 
will help.

swine are tricky to intubate.

a split larynx prep shows us 
that the gentle curve through the mouth of the foal continues down 
through larynx into trachea. not so in swine.

in swine, the axis of the 
airway takes a sharp dorsad bend as you get to the vocal folds. tube gets 
hung up here. you have to rotate 180 degrees so the curve is pointing the 
right way.

porpoise - remember, these guys are breathing out of the tops 
of their heads. their nasal airways are at right angles to their oral 
airways. larynx is way up behind the palate. you can not see the airway 
through the mouth. you need to reach in, grab the larynx, pull it 
forward, and intubate. you can't intubate through the blow hole because 
they have a nasal septum in there. so you pull larynx forward into mouth.


rabbits are hard to do too - mouth small, doesn't open wide, teeth in the 
way. some people put them in dorsal recumbency with towel under neck for 
dorsiflexion. also you can intubate awake nasally with local anesthetic, 
requiring great skill.

rodents - long narrow mouth that doesn't open 
well. can use slit otoscope cone as speculum, shine light through there, 
pass in tiny catheter through the slot with a cole tube threaded over it 
- when catheter goes in, remove cone, push in cole tube over the 
catheter, then pull out catheter. 

in horses - they tend to have food up 
in the back of their mouth so you have to rinse it out first.   then, 
also, mouth doesn't open wide, can't get laryngoscope in there. use end 
of tube to move soft palate. push it in blindly and move it around til it 
goes in. sometimes you push soft palate back into larynx. doesn't seem to 
cause injury, but you should be gentle anyway. horses are easy to 
intubate. 

cattle: sometimes can intubate blindly, but more often must 
do manually by cranking mouth open, holding the end of the tube with your 
fingers in front of it so you can palpate the larynx and then push tube 
past your fingers into larynx. with smaller cows, may require using a 
small tube inside the big tube if tube won't fit with your arm in there. 
then use the over the tube technique.
in smaller animals can do similar 
thing with an endoscope inside the tube

reptiles and birds - easy to 
intubate. airway kind of jumps out at you - just push tube in. some 
reptiles are venemous - use something other than fingers to open the 
mouth.  do not try this at home. have an experienced handler with you. 

you may also want to put the snake inside the tube instead of the other 
way around.

birds - this ostrich has a giant airway you see as soon as 
it opens the mouth. even tiny birds are easy to intubate. psittacines 
have fat, fleshy tongues and you may have to grab tongue with hemostat or 
fingers to pull forward to expose larynx. for flamingoes, filter feeder 
s- those can be hard to intubate.

also, if you have a really hard 
situation for intubation, here is a diagram of a llama with a needle 
placed b/w tracheal rings - then a wire is fed through the needle  - it 
can then come out through nose or mouth - use laryngoscope blad to push 
up palate to keep it out of nose. then you can thread a tube over the 
wire and into trachea and then remove needle and wire.

you do not want 
to create airway resistance - use largest possible tube without causing 
trauma. remember flow for any pressure differential is proportional to 
radius to the fourth power, and inversely proportional to the length of 
the tube. do not use a tube that is too long (increases resistance) or 
too narrow (decreases flow). use a tube that fits.

for mechanical 
ventilation situations, resistance isn't as important.

reflexes to know 
about are in handout. can elicit them by stimulating palate, pharynx, 
larynx, trachea, bronchi =- all carried by vagal afferents to brain and 
cause responses including vagal responses - increased airway secretions, 
decreased HR, decreased airway diameter; respiratory center responses - 
increased RR, coughing, apnea (barbiturates do this); 
laryngospasm/closure of glottis, gagging, esophageal activity - all these 
muscles are the striated muscles. these can't be blocked by atropine like 
the vagal responses  can. also, you may bet reflexes of diaphgram and 
abdominal muscles that can't be blocked by anticholinergics.

therefore, 
ensure adequate anesthesia prior to your intubation attempt, use of 
anticholinergics and local anesthetics as needed.

other complications - 
overinflated cuff damaging trachea.
two cats died at a practice to be 
unnamed with ruptured tracheas. at postmortem, holes in tracheas were at 
the same spot. an ET tube was placed and the hole was found to be exactly 
where the cuff was. someone overinflated the cuff and caused necrosis of 
these tracheas. this is bad. overinflation of cuff can reduce tracheal 
blood flow especially in situations of hypotension. 

inflate the cuff 
just enough to make a seal!
trauma can also be caused by having the cuff 
in the larynx. 
tubes can also kink or occlude the airway so always 
ensure airway is clear during anesthesia. 

lynx intubated with tube that 
is too long - kept getting stuck against tracheal wall so it couldn't 
breathe.

animals with short tracheas - primates, great apes, marine 
mammals - bifurcation is much closer to larynx - so you may accidentally 
place tube right at the carina or in a mainstem bronchus.

this gorilla 
was intubated at the zoo for a van ride to VHUP. dr klein intubated too 
far - xray showed the tube was down one mainstem bronchus, resulting in 
ventilation perfusion mismatch - a 50% shunt.

during recovery - this cat 
wasn't being watched - she chewed her tube in half and inhaled part of 
it. luckily they could grab it with alligator forceps. has also happened 
in a goat (snagged it with a urethral catheter they shoved into tube, 
expanded basket,and pulled back). also a nasal tube with no flange got 
inhaled into a horse's trachea. they had to remove it with an endoscope.


always watch intubated animals. this dog has a tube in his mouth and the 
open end got up against his lip. when they found him he was cyanotic but 
they fixed him up.
---break---

slide: curare exhibit.

neuromuscular 
blocking agents (NMBAs) are interesting. read the notes to learn about 
malignant hyperthermia since there won't be time to discuss it. 

NMBAs 
are used usually in domestic anesthetized animals to provide reliable 
muscle relaxation during delicate surgery. in humans they are used for 
most intubations and for all abdominal surgery. humans are more prone to 
laryngospasm and intubation is hard so they are usually paralyzed for 
that. this isn't usually done in animals but we use NMBAs for ophthalmic 
procedures, neurosurgery, cases where the animal is fighting a 
ventilator, and if you have an animal with a very unstable anesthetic 
plane and you can't predict reflex movement you might paralyze it. NMBAs 
are also used still for immobilizing large reptiles, especially dangerous 
ones, so they can be examined. you wouldn't do surgery with just an NMBA 
without analgesics or sedation. but in these large reptiles, the 
injectable anesthetics last too long, and the paralytic - succinylcholine 
- is short acting. some people use NMBAs in chelonians for intubation to 
get the heads out of their shells. also, b/c the muscles that determine 
pupil size in birds/reptiles are striated, not smooth, you can't dilate 
their pupils using atropine or tropicamide, so some people use topical 
NMBAs - but these do have some systemic effects that may be unpredictable 
so you haev to be careful with that.

remember you have a motor end plate 
MEP and ion channels in it. during relaxation of the muscle the channels 
are closed, the membrane is polarized. when an impulse comes to NMJ, ACH 
is released from nerve, it comes to receptors on the ion channels, and 
when each subunit is bound to an ACH, the channel opens, and K+ goes out 
of the cell, Na+ and Ca++ come in, and an electrical depolarization 
occurs, releasing intracellular Ca++ causingg contraction -this is a 
rapid effect, ACHesterase breaks down ACH, muscle relaxes. so when you do 
a movement like lifting something you have many nerve impulses.

the NMBA 
may be a nondepolarizing kind - where the drug occupies the ACH binding 
site and prevents channel from opening, and persists at the binding site 
for longer than ACH. there may also be NMBAs that bind inside an open 
channel and prevent things from passing through. 

or, depolarizing kind: 
succinylcholine is an agonist molecule - it will depolarize the MEP but 
after that it isn't metabolized by ACHesterase and it persists and holds 
the MEP in a depolarized state. so initially you see fasciculations 
occuring due to presynaptic effects of succinylcholine causing releases 
of ACH - fasciculations are a motor unit event, not due to the effect on 
individual fibers, but a neural event, some kind of feedback or 
something, but anyway, you initially see the results of the 
depolarizatino and then after that, paralysis occurs because even though 
the MEP is held in depolarized state, the ion channels on the rest of the 
membrane aren't responsive to agonist molecules - they respond to 
electrical stimulus. they have voltage dependent and time dependent 
gates. they initially open and depolarize membrane,b ut then, since no 
restoration of polarization of MEP occurs, the voltage dependent gates 
stay open,and time dependent gates close, and the channels are 
inactivated, can't be depolarized again - sodium is pumped out - membrane 
may repolarize but not at the MEP,and those channels can't be activated 
b/c time dependent gates won't open again until there is a new stimulus 
(electrical)

NMBAs: 
clinically used nondepolarizers: pancuronium, two 
others - atracurium, vecuronium
depolarizers: succinylcholine

human use 
- not vet
mivacurium: nondepolarizing but metabolized by ACHesterase- 
short acting
pipecuronium: longer acting - used for long human procedures


blocking agents also have autonomic effects. can attach themselves to 
cholinergic receptors on sympathetic ganglia or parasympathetic or 
sympathetic postganglionic receptors. effects vary.
vecuronium has no 
effect
pancuronium has a little vagolytic effect, not a problem in our 
spp
curare causes clinically significant hypotension and histamine 
release in dogs
atracurium causes histamine release in dogs - at three 
times the effective relaxing dose significant hypotension occurs due to 
histamine release.

there is a new isomer of atrocurium - cis-atrocurium 
- which doesn't cause histamine release. so this is probably preferable 
in dogs/cats. not a big deal in horses, though.

succinylcholine - 
interesting. affects autonomic ganglia. used to use in awake horses for 
restraint for castration. very inhumane. was popular many years ago 
before we had safe anesthetics to use in the field, and succinylcholine 
was the safest option compared to other choices. in healthy horses given 
appropriate doses apnea lasted only about 30 seconds. also extreme 
hypertension, tachycardia, hypoxia, hypercarbia, arrhythmias, myoglobin 
release, K+ release during initial fasciculation stage - probably all due 
to sympathetic ganglionic stimulation. also seen in anesthetized horses, 
dogs, cats. succinylcholine can also affect parasympathetic ganglia 
causing bradycardia and hypotension
so it's really unpredictable.


pancuronium and vecuronium - dno't really worry about it.

CNS effects? 
EEG activation - direct effect or indirect? well, muscle spindles are 
activated during initial depolarization, this may be the cause. 
no real 
CNS effects of NMBAs.

placental transfer - pancuronium only?
after 20-30 
min of giving pancuronium to mom during c-section you can detect some 
level of it in fetal circulation. these babies were not paralyzed, normal 
apgars, but they did have detectable drug on board. vecuronium and 
atracurium - much much less transfer. a non issue. these are fat polar 
molecules - enter CNS or placenta very very slowly.

as far as 
elimination of nondepolarizers goes...
there is some prolongation of 
pancuronium action in patients with renal failure. this may not be a 
problem b/c the action of the antagonist drugs given to reverse them are 
also prolonged; but there does have to be metabolism and excretion of pan 
and vec.

Hofmann elimination - this means at normal body temp and pH the 
molecule falls apart - atracurium does this - given as a bolus and it 
gets to NMJ quickly, but after that begins to degrade - so has short 
duration of action. 

ester hydrolysis - nonspecific plasma esterases 
degrade atracurium.

poor circulatory function, age, liver dz do not 
prolong action of atracurium. pancuronium really the one that is affected 
by those.

succinylcholine is really two ACH stuck together. is 
metabolized by pseudocholinesterase. most of a dose is metabolized before 
reaching the NMJ. what does reach NMJ causes paralysis. if animal was 
exposed to organophosphates and has little pseudocholinesterase left, you 
can overdose succinylcholine - very prolonged duration.

there are some 
physiologic states and some drugs that might be given concurrently that 
will affect sensitivity to NMBAs. they are in the handout. think 
specifically about aminoglycosides which increase sensitivity to NMBAs 
and also hypercarbia - when CO2 is very high, it is difficult to reverse 
the nondepolarizing agents, in fact it can't be done. this means that 
when ventilating a paralyzed animla you should continue until NMBA is 
totally worn off or reversed with antagonist drug. also cytotoxic drugs, 
electrolyte imbalances, muscle diseases are listed in handout.

when you 
use an NMBA you must decide: long acting (pancuronium) or short acting 
(vec, succ, atr). depends on length of procedure. or you could give 
infusion or repeat doses of short acting, or a bolus of long acting. 
usually the long acting is cheaper, but you have less control. with 
vecuronium, you can give a lot of repeat doses without a marked 
prolongation of effect. 

there are some - in the human, NMBAs are used 
for intubation often. this isn't recommended in animals with the possible 
exception of a dog with severe facial trauma or animal that is unable to 
breathe but can't be anesthetized and won't open mouth for intubation or 
some weird thing. for animals which have special circumstances, fine. but 
to use NMBA to intubate an animal that is normally hard to intubate - if 
you can't intubate it, you are going to have killed it. you must intubate 
once you use one of these drugs.

of the drugs that are useful for rapid 
intubation - succinylcholine because it works so quickly, and if you give 
enough, vec or atr can be used.

other effects:

succinylcholine has an 
effect on intraocular pressure. the extraocular muscles are multiply 
innervated and when succ is given it can cause prolonged contraction of 
these muscles. in a patient with unstable ocular injury, eg penetrating 
globe injury, if you have a rapid persistent contraction of extraocular 
muscles you may cause a rise in intraocular pressure - so succinylcholine 
shouldn't be use. use nondepolarizer.

also succ causes K+ release 
normally. in animals with denervation injuries, spinal injuries, crush 
injuries, burns - the receptors proliferate away from MEP and go all 
along the muscle fibers - so they are all totally sensitive to ACH/succ - 
so you can cause a huge K+ efflux and sudden arrhythmia and death. this 
starts to occur at about a week postinjury and can persist over a month. 
so if animal has had ths kind of injury use a nondepolarizer.

also 
animals susceptible to malignant hyperthermia may develop malignant 
hyperthermia if given succ.

what you need to know:
spp sensitivity to 
the NMBA - widely variable. remember that sheep/goats are exquisitely 
sensitive, requiring 1/10 or less of a horse dose. also know that in 
addition to spp differences, there are individual differences. dose 
required may vary widely. best to give minimal dose incrementally and 
observe.

the other thing is you must establish PPV. squeeze bag or use 
machine. 
face, eyes - more sensitive
neck, swallowing muscles next
the 
diaphragm is least sensitive, but when animals are partially paralyzed 
they still require ventilation - they can't breathe adequately.

it's 
nice to have  a nerve stimulator to test level of paralysis. can use 
peroneal nerve along the fibula, or the ulnar nerve inside the elbow. not 
good to use facial nerve - resistant to relaxants, can give erroneous 
impression (hey, she just said face was more sensitive!). note that the 
faster your test rate, the more stress you put on the system. if you look 
at one single twitch it may be hard to assess. clinically you are feeling 
strength of twitch - using more rapid stimulation rate gives you a better 
idea.

she has, again, gone over 50 minutes, and now someone is asking a 
question...feh.

when you are done - you can reverse nondepolarizers with 
an antagonist - cholinesterase inhibitors which prolong action of ACh in 
synaptic cleft, so it can compete for receptor. 
edrophonium, 
pheostigmine, something else.

there are some autonomic effects of 
cholinesterase inhibitors you should know, they are in the handout. 
sometimes you must also give an anticholinergic to prevent problems.


again, because of the side effects and the facts that antagonists can be 
overdosed, it is better to titrate them than to bolus them. if you do not 
have a nerve stimulator and you want to know if animal has adequate 
muscle strength you can use palpebral reflex in lightly anesthetized 
animal - check repeatedly. a single response doesn't mean it  is 
ready.also can look at neck strength, can occlude airway briefly and see 
if animal can overcome you.

---end----