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PHARMACOLOGY 
didn't let them drift. We somewhat controlled 
the PC02. But we didn't have an entire sample. 
Dr. Jankus : Thank you. 
Geraldine Kent, Hospital for Sick Children, 
Toronto: You mentioned that you had a pe- 
ripheral vascular constriction with halothane. 
Dr. Sawyer : Yes, a httle bit. Only 14=%. 
Dr. Kent: Right. Now the reason we use 
halothane for open heart surgery is to get a 
good perit)heral vascular dilation. I suggest that 
the acidosis from inadequate ventilation pro- 
duced your peripheral vasoconstriction and the 
Bird respirator isn't adequate for the pig. 
Dr. Sawyer : Well, the pig triggered the ma- 
chine. And it was spontaneously breathing and 
I won't argue with you on that point. 
Dr. Kent: Well, are you then stating that 
halothane is a peripheral vasoconstrictor in the 
pig? 
Dr. Sawyer: Under the conditions of the 
study, under spontaneous ventilation, sponta- 
neous assisted ventilation, it was. 
Dr. Kent : But halothane is a marked respir- 
atory depressant in the pig. 
Dr. Sawyer : Right. 
Dr. Kent : And unless you're on top of that 
ventilation, you're losing out on your acidosis. 
Right? I suggest that you buy a volume cycle 
ventilator instead of a Byrd. 
Dr. Sawyer : I think that that's a very good 
point. Halothane has been noted as a vasodila- 
tor in many, many studies. 
Allen Ingling, University of Maryland, 
College Park, Md. : I'd like to know two things : 
one, what was the material, and size, of the tub- 
ing you used in the portal vein ? Secondly, what 
procedures did you use daily or every six hours 
to keep that material open ? 
Dr. Sawyer: We used nylon. In the March 
issue of "Anaesthesiology," we have noted the 
size of the catheters and the other details of the 
study. We filled these catheters with heparin 
and then would flush these catheters every 
other day or from Friday to Monday, so there 
would be anywhere from two to four days be- 
tween flushings. 
Alden E; Stilson, Ohio State University, 
Columbus : I might mention the possible use of 
nitrous oxide together with halothane. I'm sure 
you have already used that in other cases. It 
might tend to ameliorate some of the wide fluc- 
tuations due to halothane by itself, by the sim- 
ple process of reducing the amount of halothane 
necessary. 
Dr. Sawyer : Right. I agree with that. 
Hugh Calderwood, University of Florida, 
Gainsville : How do you determine surgical an- 
aesthesia for a skin incision in a paralyzed ani- 
mal? 
Dr. Sawyer: This animal was paralyzed 
only for about three minutes. And we had one 
hour before we evaluated the depth of anaes- 
thesia, before we did the study. So we had one 
hour of equilibration and we assume that most 
of the paralyzing anaesthesia was dissipated by 
then. Spontaneous respiration resumed in about 
three minutes. 
Dr. Calderwood: Using these animals with 
repeated different drugs, how do you think 
these drugs effect enzyme induction and metab- 
olism of subsequent drugs ? 
Dr. Sawyer: We may have seen that influ- 
ence, I agree. We evaluated the control values 
between each study and found there was no sig- 
nificant difference between the controls prior to 
each of the four different anesthetics. There 
may have been some enzyme induction but we 
didn't study it. 
Questioner (Unidentified) : Dr. Sawyer, 
Dr. Clarkson at our institution has come out 
very strongly for a clinical syndrome of halo- 
thane hepatic toxicity and he feels that this is a 
predictable response in perhaps 1 to 2% of the 
individuals who were repeatedly exposed to hal- 
othane. Did you make any observations in your 
swine who did receive halothane several times 
as to hepatic toxicity or unexplained fevers 
after exposure to it? 
Dr. Sawyer: I was looking for this, with 
great interest, and never found it. And I never 
saw any problem with it in pigs. I have only 
seen it in one dog clinically. And I'm looking for 
it with great fervor. 
