438 
SURGERY AND TRANSPLANTATION 
tions: (1) that the usual pulmonary artery an- 
astomosis can, under certain circumstances, 
contribute to the high vascular resistance which 
occurs in transplanted canine lungs; (2) that 
the fixed nature of the vascular resistance in 
dog lung transplants is largely due to the fail- 
ure of the arterial anastomosis to dilate, as the 
normal pulmonary artery does in response to 
increased flov^; (3) that lung transplants w^ith 
v^'ide distensible pulmonary artery anastomoses 
can have a normal decrease in vascular resist- 
ance with increasing flows; and (4) that dogs 
receiving a lung autograft or allograft with 
such a distensible anastomosis can tolerate si- 
multaneous ligation of the contralateral pul- 
monary artery and can survive solely on the 
vascular and respiratory function of the trans- 
planted lung.^'^*' 
The present communication will attempt to 
answer some of the questions and objections 
that have been raised in connection with our 
model of single lung transplantation and imme- 
diate ligation of the opposite pulmonary artery 
in the dog. In addition, we will present new find- 
ings which elucidate the efficacy of presently 
available immunosuppression in preventing the 
functional defects of lung allograft rejection 
and which relate to the long-term fate, morphol- 
ogy, and functional capabilities of autografted 
lungs that are providing total gas exchange and 
carrying the entire cardiac output for periods 
up to 45 months. 
METHODS 
Left lung autografts were performed in 16 
mongrel dogs, and left lung allografts were per- 
formed in 115 mongrel dogs. Surgical tech- 
niques for these operative procedures have been 
described elsewhere.^'^ Key features of the op- 
erative procedures included: (1) a two-layered 
everting atrial anastomosis which excludes 
atrial muscle from the lumen and prevents 
thrombosis, (2) a telescoped bronchial anasto- 
mosis, and (3) a distensible pulmonary artery 
anastomosis. Within ten minutes of completion 
of the transplant the right pulmonary artery 
was doubly ligated thereby placing total func- 
tional dependency on the transplant. 
All animals with allotransplants received im- 
munosuppression. This included 1-3 mg/kg/day 
of azathioprine and varying doses of rabbit 
antidog lymphocyte serum (ALS) and corti- 
costeroids (Table I). 
All autografted and selected allografted re- 
cipient dogs underwent serial studies of their 
pulmonary hemodynamics, arterial and venous 
blood gases, and pulmonary angiographic morph- 
ology. These studies were carried out pre- 
operatively in most animals and, at two to six 
month intervals up to 45 months postopera- 
tively. The methodology and calculations used 
in these studies have been described in detail 
elsewhere.^'^ Briefly, the animals were anes- 
thetized with pentobarbital, the femoral artery 
was cannulated, and a polyethylene catheter 
was introduced by way of the external jugular 
vein and fluoroscopically guided into the pul- 
monary artery. While the dogs were breathing 
room air spontaneously through an endotra- 
cheal tube, the pulmonary artery pressure and 
cardiac output were determined; p02, pCOg, 
and pH of blood from the pulmonary and fe- 
moral arteries were measured ; and oxygen sat- 
urations and left lung vascular resistance were 
calculated. Then, after the injection of 25 milli- 
liters of 60 per cent diatrizoate meglumine 
(Renografin) into the main pulmonary artery, 
12 serial roentgenograms were taken at half 
second intervals with the use of a mechanical 
cassette changer. 
Complete autopsies were performed on all 
dogs that died. All anastomoses and the site of 
right pulmonary artery ligation were inspected 
.—Immunosuppressive Regimens and Survival Results in Groups of Dogs Receiving Left Lung Allograft: 
with Right Pulmonary Artery Ligation 
Group 
Number 
No. 
of 
Dogs 
Azathioprine 
(mg/kg/day) 
ALS 
(ml/day) 
Prednisone 
(mg/day) 
Mean 
Survival 
(Days) 
No. Dogs 
Surviving 
>1 month 
1 
33 
1-2 
3-9 
16 
6 
2 
21 
1-2 
10-19 
6 
2 
3 
61 
2-3 
20-50 
50-75 
6 
3 
