F. T. GALYSH AND R. F. WALLIN 
1037 
hoisting the animal to a convenient height 
above the floor. This method of suspending 
calves has provided a useful and convenient fa- 
cility for postoperative care and monitoring of 
this species. 
ANESTHESIA IN CALVES 
Techniques of anesthesia in the larger mam- 
malian species undergoing thoracic surgery 
have evolved principally as modifications of 
procedures used for cardiac surgery in man. 
Thus, Short et al.,^ who described in detail their 
anesthetic technique, induced anesthesia in 
calves with A% halothane vaporized into a par- 
tial rebreathing circle system Mrith 25 to 50% 
nitrous oxide in oxygen at a level of 4 liters per 
minute. This vapor was administered through a 
mask adapted for the muzzle of these calves in 
which valve replacement or bypass pump im- 
plantation procedures were to be carried out. 
The trachea was then intubated without re- 
course to the use of muscle relaxants but with 
the aid of a specially constructed laryngoscope. 
Anesthesia was maintained with 0.25 to 0.5% 
concentrations of halothane until the skin was 
incised. At this time, nitrous oxide was discon- 
tinued; halothane concentration was increased 
to a mean value of 2% in oxygen until control 
of respiration was achieved. These calves were 
then mechanically ventilated with a Bird^ re- 
spirator connected through a Fluotec^ halo- 
thane vaporizer, using 1.0 to 1.5% halothane in a 
non-rebreathing system. Respiratory rate var- 
ied from 12 to 18 breaths per minute, inspira- 
tory pressure was 20 to 30 cm H2O with tidal 
volumes of 1 to 3 liters. Depth of anesthesia 
during surgery was characterized by lack of re- 
spiratory efforts, dilated pupils and absence of 
movement. During extracorporeal circulation 
these workers used either succinylcholine (50 to 
100 mg) or intermittent intravenous injections 
of 50 to 100 mg of thiopental to maintain immo- 
bility, Halothane was again used intermittently 
to maintain anesthesia until the pleura were 
closed and discontinued during closure of the 
J Bird Mark 7, Bird Corporation, Palm Springs, California 92262 
^ Fluotee, Harris Calorific Company, Medical Division, Cleveland, 
Ohio 
chest wall. Calves awakened promptly at the 
conclusion of surgery. 
Many additional anesthetic techniques have 
been described for cardiac surgery in calves. 
Larson et al.^ induced anesthesia with diethyl- 
ether and then administered 0.5 to 3.0% hal- 
othane with oxygen for maintenance. When 
they employed thiopental instead of diethyl- 
ether for induction, prolonged recovery times 
of 24 hours or more were observed. 
Bonchek et al.^ also used diethylether for in- 
duction followed by 0.5 to 1.5% halothane in ox- 
ygen for maintenance. Additionally, they ad- 
ministered succinylcholine to control muscle 
relaxation during surgery. Donawick et al.^ in- 
duced anesthesia with 4% halothane, 71% ni- 
trous oxide and 25% oxygen, using a conical 
face mask. After tracheal intubation, their 
calves breathed a 50-50 nitrous oxide-oxygen 
mixture with 0.5 to 2% halothane. When the 
thorax was opened, they reduced the halothane 
concentration by one-half and instituted posi- 
tive pressure ventilation at a rate of 14 to 18 
breaths per minute at a pressure of 25 to 30 cm 
H2O. During cardiopulmonary bypass they 
statically inflated the lungs to 25 cm H2O with 
the 50-50 nitrous oxide-oxygen mixture. 
We have drawn upon the experience of sev- 
eral investigators in developing the following 
anesthetic technique which we have used with 
satisfactory results in over 100 calves. Food and 
water are withheld for 24 hours and calves re- 
ceive no preanesthetic drugs. Anesthesia is in- 
duced with 5% halothane delivered from an 
anesthesia machine,^ to a specially constructed 
face mask, similar to that described by Dona- 
wick, et al.^ Alternatively, anesthesia is induced 
with the aid of a special face mask containing 
gauze sponges saturated with halothane. Anes- 
thesia is maintained with 0.5 to 1.0% halothane 
during skin preparation. The animal is then 
placed on the operating table and the trachea 
intubated with the aid of a laryngoscope and a 
metal obturator placed in the lumen of the en- 
dotracheal tube. The endotracheal tube is con- 
nected to the yoke of the anesthesia machine. A 
Bird respirator'^^ is used to drive a Bird 
^ Ohio Heidbrink, Ohio Medical Products, Madison, Wisconsin 
53701 
M Bird Mark 8 or 10, Bird Corporation, Palm Springs, California 
92262 
