CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 8, September 2013
AFRICA
e3
considered. Alternative incisions such as a left posterolateral
thoracotomy that would enable full exposure of the coronary
arteries may be required. Besides, it may be difficult to institute
standard CPB by means of aortic and right atrial cannulation.
These standard cannulation techniques may need to be
modified, for example by the use of direct bicaval cannulation,
femoral vein cannulation, or cannulation through the pulmonary
artery into the right ventricle. However, the off-pump technique
is most commonly used, as in our patient, for only CABG.
In patients who have multi-vessel lesions, hybrid myocardial
revascularisation is another option.
4-6
This approach involves the
anastomosis of one venous graft to the LAD and the placement
of stents in the left main coronary artery and in the ostial
and proximal lesion of the circumflex artery. It is difficult to
perform a proximal anastomosis to the ascending aorta due to
displacement and rotation of the ascending aorta and severe
adhesion to the thoracic cavity, so proximal anastomoses to the
descending aorta may be more advisable.
Consequent to displacement and rotation of the heart and to
hyperinflation of the contralateral lung, the internal mammary
artery (IMA) may not be useful as a graft for the target vessel
because of the risk of IMA stress and tension.Then too, harvesting
of the IMA may decrease pulmonary function and increase the
risk of injury to the phrenic nerve.
4,7,8
Therefore, venous grafts
have reportedly been used in most CABG procedures after
pneumonectomy.
In our patient, we chose saphenous vein grafts, chiefly because
the pedicle of the left IMA would not reach its target vessel (the
LAD) without being subjected to substantial tension. Also the
right lung was displaced to the mediastinal region and the heart
had moved into the left hemithorax. This condition could make
exposure of the coronary arteries and therefore CABG difficult
by making exposure of the heart difficult. However we could
fully expose the right coronary artery and LAD. Therefore
alternative interventions such as a hybrid revascularisation or
left thoracotomy were not required. Difficulty with cannulation
could also have occurred due to the mediastinal shift, however
we did not encounter any problems during the cannulation
procedures of the aorta and right atrium.
Although standard approaches are usually preferred in
patients who have undergone pneumonectomy and who need
to undergo open-heart surgery, sometimes different practices
may be required.
3-5
Observation of the mitral apparatus may be
difficult because of the shifting of the heart to the right as a result
of right pulmonary resection. In those cases, the mitral valve may
be approached through the left atrial airucula. Transseptal and
superior septal approaches may also be preferred.
9-11
However,
as our patient had undergone a left pneumonectomy previously
and the heart had displaced towards the left hemithorax, no
difficulties were encountered to access the valve. On the
contrary, a left atriotomy was done and mitral valve replacement
was performed.
Physiological changes likely to occur are impaired lung
function and poor pulmonary reserves where even minor
atelectasis or pulmonary infection in the postoperative period
can be disastrous, as the respiratory reserves decrease by over
50% in these cases; more so in cases of valvular heart disease
with high pulmonary artery (PA) pressures.
4,12
Mean PA pressures
>
40 mmHg carry a higher risk for surgery and we use only
glycerol trinitrate solution in the peri-operative period to lower
PA pressures.
7,13
As pulmonary dysfunction is both common and frequently
severe even after uncomplicated CPB, all possible measures must
be taken to preserve the single functioning lung. Postoperative
care includes careful fluid management, aggressive pulmonary
care including bronchodilator therapy and nebulisation with
chest physiotherapy.
2,4,12
Pulmonary function, which is inherently
reduced after pneumonectomy, becomes even worse after CABG.
Although the risk of pulmonary complications increases,
no deaths from respiratory failure have been reported in
cases of CABG after pneumonectomy. Therefore, there is
no general contraindication for open-heart surgery in these
special circumstances. Nevertheless, it is prudent to give careful
pre-operative consideration to pulmonary function.
Forced vital capacity usually reduces approximately 70% on
the first day after cardiac surgery compared to pre-operative
values. Reduced forced vital capacity improves from the
10th postoperative day. However this increase is about 30%
compared to the postoperative period.
4,7,14
Such changes may
be easily tolerated by patients with normal pulmonary reserve.
However pnemonectomy patients have difficulty tolerating
this change as their pulmonary reserve has reduced about
50–55% due to pneumonectomy.
4-7
Surgical morbidity is reduced
through pulmonary rehabilitation in the early period and mainly
with postoperative care. Pulmonary physical exercises and
bronchodilator therapy should be started in the pre-operative
period. We did this with our patient.
In general, conditions to be considered in patients who
have a single lung and will undergo open-heart surgery are
as follows. The central venous line should be placed from
the side that the pneumonectomy was performed because of
the risk of pneumothorax. The intra-operative position of the
coronary arteries and cannulation procedures should also be
considered because of cardiac displacement.
4,5,7
Cold topical
applications should be avoided in patients with a single lung as
diaphragm paralysis may develop. Besides, atelectasis and deep
vein thrombosis can be avoided with early mobilisation. Chest
physiotherapy and exercises should be done to reduce atelectasis.
Bronchodilators, steriods and diuretics should be used in
order to prevent pulmonary congestion and bronchospasm.
Non-steroid anti-inflammatory drugs may be used, as pain
may hinder pulmonary function in the postoperative period.
Beta-adrenergic blockage should be avoided due to the risk of
bronchospasm. Patients should be ventilated with low pressure
in order to avoid postoperative pulmonary barotrauma and they
should be extubated as early as possible in order to prevent
complications from prolonged intubation.
14
Conclusion
Performing open-heart operations in patients who have undergone
pneumonectomy may have potentially serious complications and
these cases require proper pre-operative assessment. Patient
selection regarding pulmonary function must be carefully done.
The surgical procedure needs to be carefully planned and
executed for a successful outcome. We believe that open-heart
surgery can be safely performed in patients who have undergone
pneumonectomy, with careful pre-operative assessment and
preparation for surgery, and fluid infusion (with measurement of
central venous pressure).
