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perkowski
anesth review
5/5

so, we're going to review.
a 
couple of people have asked about ketamine- 
the thing about htat is, in 
general, ketamine is considered to be fairly sparing of the CV system. in 
normal, healthy patient, HR and CO go up a bit, BP goes up or stays the 
same. so we think it's nice to the cardiovascular system. BUT this is due 
to the catecholamine release it causes. in sick, debilitated patients who 
have used up endogenous catecholamines, you will not see that effect - 
you may see cardiovascular depression b/c ketamine is a direct negative 
inotrope. having said that, you have to make judgement calls all the time 
about what to use and one key factor is what do you have on the shelf. 
for sick patients, use drugs like opioids in combination with 
benzodiazepines. in practice, referral clinics use that too. many private 
practices do not have opioids - too much paperwork for these schedule II 
drugs. they only have ketamine or thiopental. then they may use ketamine 
over thiopental. also at NBC - don't use opioids in horses, they get 
excited. they use ket/val for induction instead of thiopental. so it is 
confusing - ketamine has different effects depending on status of animal. 
horses usually healthy prior to immediate colic. small pets often have 
been chronically ill. the other ketamine thing is if your patient has 
underlying heart disease, a patient with a sick heart - shouldn't use 
something that will increase HR, so do not use ketamine. 

you do not 
have to know everything about every drug for dr p, but you do need to 
know some basics.

her question from last year - which she graded easily 
- will now be gone over...
also dr. soma's small animal question.

1. her 
question from last year
(this year she will also do an essay)
(dr klide 
probably won't do essays)(neither will dr kim olsen)
who is dr olsen??


ok. so the question is - 3 yr old male castrated k9x, 20 kg. young dog. 
presents 2 days post HBC. last normal 2 days ago. then hit by car. took 
to emergency practice - tx with fluids for shock. responded well and went 
home next day. did well for a day. then got depressed. started to vomit 
this am. seems to be breathing rapidly. you do a PE - he's depressed. HR 
regular but elevated at 160 bpm. the peripheral pulses are bounding. that 
means what?? either vasodilation or hypovolemia causing decreased BP. 
probably hypovolemic  - no real reason for vasodilation. RR is elevated, 
obvious abdominal effort. lung sounds - muffled left, harsh right. 
mms 
pink, sl tacky, CRT 3 sec (that's a bit increased.)
chest rads show 
pulmonary contusions (goes along with harsh lung sounds) and loops of gut 
and liver and spleen cranial to diaphragm on left. so what do you worry 
about in a patient with diaphragmatic hernia? 
[question - what are your 
special concerns?}

blood work: PCV 48%, TS 4.2 g/dl - pretty normal, but 
if dog is dehydrated, and needs fluids, PCV Is a little high and fluids a 
little low b/c when you rehydrate these numbers will fall. TS will be 
low. 
BUN is elevated at 30-40 - this also indicates dehydration. 


pulses bounding, elevated azo, increased PCV --> dehydration.


pulsoximeter - 87% on room air. good or bad? bad. remember, we said that 
what pulsox reads is Hb saturation. Hb saturation - knee of curve occurs 
at PO2 of 60. >60 you are 92% saturated or greater. PO2 in venous blood 
is 40, and your SaO2 in venous blood is about 75%. you're in between 
those numbers. not good.

you have respiratory and cv problems.
are 
respiratory problems mainly oxygenation or ventilation? you tx these 
differently, remember. with diaphragmatic hernias you have both problems. 
can't ventilate - no room to inflate lungs. also ventilation perfusion 
mismatching occurs. so when you talk about these cases there are 
ventilatoin and oxygenation problems. not like dog with laryngeal 
paralysis - then, primary problem is ventilation - lungs are normal, 
chest films are normal. dog with pneumonia - problem is oxygenation. so 
you have problem with respiration here, problem with cardiovascular 
system. CNS? dog is depressed. no obvious head trauma...probably 
depressed b/c brain not perfused well. 

BP = mean pressure 60, systolic 
90, diastolic 40 - that is ok under anesth, but low for awake dog. 


cardiovascular problems are what? is dog still bleeding from two days 
ago? no, he'd be dead by now or something. no signs of that, no abdominal 
distension. main thing - is hypovolemic, been vomiting, not drinking 
well, probably third spacing since fluids are in chest, probably why 
protein is low relative to PCV. 

do you follow? 
the basic thing to get 
from this is - you were supposed to get from bounding pulse, increased 
RR, increased PCV, low pressures - know it is dehydrated and hypovolemic. 
you had to say that: dog is dehydrated, and dog is hypovolemic. 
second 
thing you needed to know: dog had problems breathing properly. dog had 
problems ventilating and his oxygenation was low.

points off: if you 
thought only problems were with ventilation, and not with cv system.


what do you do to stabilize prior to sx? fluids and O2. that was all you 
had to say. that's all. fluids and o2. extra points given if you noticed 
that when you gave fluids, TS woudl drop, and you might want to give 
colloids. crystalloids would dilute out the solids. note: never give just 
colloids. just add some colloids to your crystalloids. or something. 
sometimes you don't measure it just give as fast as you can. 

so, that's 
it. 

list of primary problems and how to address them: 

1. hypovolemic 
- give fluids
2. poor oxygenation - give oxygen
3. not ventilating well  
- fix hernia

include any preop anesthetic agents you might give, and 
why.
answer: none. remember, if dog is depressed, you do not need 
premeds. last year five people knew that. O2 and fluids is all this dog 
should get preop. you could have said something, if you explained why and 
it made sense. if you had a clue, you got credit. someone said they woudl 
give an opioid as a premed. the problem with that is respiratory 
depression - but some people said butorphanol for less resp depression, 
or if you explain that you are using it to avoid problems with cv system, 
you could get credit.

some people said respiratory system was primary 
problem, and suggested giving ace to keep calm. that was bad. no ace for 
this dog. ever. some people gave xylazine - also bad. alpha 2 agonists 
are another no no. some people suggested induction agents as premeds - 
that was just clueless. you should know difference b/w premeds and 
induction agents. premeds - often used IM. 

once patient is stabilized 
how do you induce anesthesia and why?
answer: opioid plus benzo, ok. 
etomidate, ok. why? nice to cv system. some people said propofol - but if 
you explained why, that is ok. b/c at least w/ propofol given slowly you 
don't have too much cv problem. but you do worry b/c it causes 
vasodilation and further cv depression. thiopental - bad, since liver and 
spleen are in chest, and thiopental makes spleen bigger, causes 
arrhythmias. 
mask induction - bad - dog is vomiting, could aspirate, do 
not want long induction. want fast induction. 
ket/val - if explain why, 
probably ok. 
guaifenisin - this is a centrally acting muscle relaxant 
that someone suggested using as an induction agent last year. that person 
did not get points.

do not need to know doses for her question.

include 
not only choice of drugs, but any special concerns/considerations in pt 
with diaphragmatic hernia:

-rapid induction required, rapid intubation - 
patient is aspirating, chest is full of stuff. really need something that 
works fast.
-once ET tube is in, ventilate. you need PPV for good 
ventilation
-preoxygenate if possible for all cardiac/respiratory cases


one point given if you said preoxygenate
one point for rapid sequence 
induction or the word ventilation appearing on the page
one point for 
prevent aspiration.

if dog was just dehydrated, with bad cv instability- 
you do not want rapid induction. give meds slowly, to effect, til you can 
intubate, so you do not overdose. or patient with liver dz where patient 
can't metabolize well. 
but if can't ventilate well or is vomiting - 
rapid sequence induction.

another thing- almost no one got this - one 
point for patient positioning - remember, if patient has hernia, or 
something on one side of chest but not other, keep good side up for 
improved oxygenation - at least during induction. try to keep sternal 
during clipping. don't put bad side up as long as you can avoid it. 
realize position has an effect.

how would you maintain this dog? 

isofluorane. that's the best. some said they would use infusions. no 
points lost there.

do you need special monitoring equipment in addition 
to ekg, BP, esoph steth? 
yes, pulsoximeter. +/- capnograph or spirometer 
to measure ETCO2 or lung volume. pulsox was only required answer. 

what 
do you use for postop analgesia and why? 
local block - good choice. 
intercostal block, interpleural bupivicaine - good answers. 
opioid - 
butorphanol or buprenorphine for less resp depression - ok answer
opioid 
with increased monitoring of resp function - ok answer
nothing - bad 
answer
IP lidocaine - stupid answer

dr p is liberal with the points. be 
reasonable. 

--

dr soma's question:

case one from the studies he gave 
us.
22 kg dog, came to VHUP, another HBC. initial PE revealed: HR 180, 
very pale mms, CRT indeterminate (very rare, bad finding)(very long). 
distal extremities cold, no dorsal pedal artery is palpable. can barely 
palpate femoral pulse. dog semiconscious (semi unconscious). has pain 
response when leg manipulated, has swelling around right femur. probably 
fx femur. dog can lose 25% blood volume out of long bone fx. skin finally 
gets so taut that it compresses and no more bleeding. abdomen sl 
distended, painful on palpation. RR 35 (increased). 

initial dx - 
possible femoral fx, intrabd bleeding. 
initial tx - jugular cath, blood 
draw for gases, type, crossmatch.
abd tap is bloody
bladder cath  - no 
urine obtained.

based on this, discuss initial mgmt and animal's 
condition.

-hypovolemic
-bleeding out
+/- ruptured bladder

what do you 
do? right away - shock doses of fluids. 

within 10 minutes, these values 
were reported for venous blood: PCV 40, TS 7.5 g/dl. in acutely bleeding 
patients, these numbers do not change right away. that is why they are 
still normal. 

chemistry- Na+ 138 (a bit low), Cl 90 (? not sure if 
normal),K 23 (low)
blood gases - PaO2 = 30 mmHg (normal on venous side is 
40 so this is low. why? CO is low since hypovolemic. more O2 is being 
extracted from blood as it goes through tissue. 

if a patient is on room 
air, and PO2 is about 100 mmHg, their total O2 content will be - if the 
HCT is 45, Hb is about 15 gm/dl (1/3 of HCT), if you do your O2 content 
equation, recall O2 = 1.34 x grams Hb x % saturation + PO2 x sol 
coefficient which is .63

so that's about 20.1 ml O2/dl blood. what 
happens, the reason your mixed venous blood has PO2 of 40 is that to 
maintain O2 delivery, it extracts 5 ml O2 as it goes through tissues and 
now PO2 is forty. um, I got confused here. but if CO goes down, it 
extracts more, and PO2 falls. 

dog is tachypneic, hyperventilating. do 
you suspect pulmonary problem? well, could be hyperventilating due to 
pain, or pulmonary contusions. 

another point wrt O2 sat...if you put on 
supplemental O2 and make PO2 500, the O2 sat isn't goign to be over 100%, 
your total O2 content will never be over 20 by much, b/c of O2/Hb 
dissociation curve - only a little bit of O2 is dissolved, the rest is 
bound to Hb. so in venous blood, even with high arterial PO2, it won't be 
that much higher than PO2 40, b/c body has to use oxygen. even with very 
high PO2, you aren't carrying that much more oxygen in the blood. mixed 
venous PO2 may reach 45, but if it is over that, it's not mixed venous 
blood. 

PvCO2 is 35. should be 5 or 6 mm higher than in arterial blood 
b/c you make CO2 and venous blood picks it up. in arterial blood would be 
30 mmHg. so yes, dog is hyperventilating. PaCO2 should be b/w 35-45. if 
under 35, is hyperventilating - blowing off too much CO2. (on handout, 
should say PvCO2/PvO2 not Pa). pH is 7.12 - this is low, acidotic. bicarb 
is 13, BE is -15 meq.

so, we know it is acidotic. 
BE - normal is -3 to 
+3. BE is useful 

pretend we have arterial gases - say PaO2 80. BE 
basically calculates for us what the bicarb is at a theoretical normal pH 
- it normalizes the respiratory component, and says that what the bicarb 
then is x units apart from the measured bicarb. so this tells you the 
metabolic component. so bicarb is 13 in this acidotic dog. 

look at pH - 
acidotic.
look at PCO2 - respiratory component - if over 40: resp 
acidosis. if under 35 - respiratory alkalosis. this dog has respiratory 
alkalosis.
don't look at bicarb.
look at BE - here it is -15, which is 
too low. this is all metabolic. this is metabolic acidosis - a base 
deficit. 

usually the primary defect is going to match the pH - this dog 
has a metabolic acidosis with compensatory respiratory alkalosis -which 
explains high resp rate.

so first look at pH - acid or basic.
look at 
CO2 - high = resp acidosis, low = resp alkalosis
BE - high - met alk, low 
= met acidosis. 

ok. so, what is the approximate amt of bicarb needed to 
adjust acid/base status?

0.3 x weight x BE (based on arterial gas)


-note  - you do not really treat based on venous blood gases. so this is 
kind of specious... you can't really tell if hyper/hypoventilating based 
on venous gases b/c acidotic animal makes a lot of CO2. but we know 
venous CO2 is lower than normal here, under 35, so must be 
hyperventilating. 

[3 ml crystalloid per ml blood loss]
[give extra 
bicarb b/c not all stays in vessels]

other thing is - again, you have to 
ask him. we rarely use bicarb here. not unless pH is under 7. it's not in 
vogue to give bicarb. it does bad things.

bicarb dose = BE * wt in kg * 
.3

so initial tx given - dog lifts head, licks you. abdomen gets more 
distended.

why? bleeding.
urinary cath - no urine is obtained. why? 
could be ruptured bladder. could be poor renal perfusion and no urine 
production. with ruptured bladder, potassium goes up and this dog's 
potassium is low. could be reduced renal perfusion, not enough volume 
being given.

labs: PCV 22, TS 4.2 - explain drop: well, he's been 
bleeding all along. plus you've diluted him out. lab says no blood is 
available. need time to get donor. 
what can you do? fake blood, 
colloids. 
dog is moved to transport table - almost arrests. what do you 
do? increase fluids. what else do you do when BP bottoms out while you 
are anesthetizing the animal - turn off inhalant, turn up fluids, flush 
with O2, keep under with opioid infusion to maintain pressure, then use 
pressors or inotropes - to manage maybe give phenylephrine, epi, 
something like that. 

suggested anesthetic course -s omething good for 
CV system, same as other question. in this case, induce slowly, to 
effect, not rapid sequence induction, but slow, titrated induction. 
preoxygenate if possible. 
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