Page 194 - Clinical Manual of Small Animal Endosurgery

182 Clinical Manual of Small Animal Endosurgery

Single-lung ventilation by means of endobronchial blockers or selective
bronchial intubation directed by preoperative bronchoscopy has been
reported in a number of studies. While some have regarded this as essen-
tial for safe lateral recumbent thoracoscopic procedures (Potter and
Hendrickson, 1999), many others have performed the same procedures
with no more difficulty without this technique. Single-lung ventilation
notably increases the anaesthetic time, as well as having effects on anaes-
thesia and requiring attentive monitoring throughout. There is a learning
curve to these techniques, and single-lung ventilation should be estab-
lished in the operating theatre immediately before thoracoscopy. Dis-
lodgement can occur with moving or positioning of the patient. Incorrect
placement can result in the lung in the operative hemithorax remaining
inflated. Depending on the initial placement, inflation of the balloon can
also result in displacement into the carina or trachea. Initial placement
or confirmation of both techniques requires bronchoscopy.
Kudnig et al. (2006) found single-lung ventilation in thoracoscopy
comparable with clinical parameters encountered in bilaterally ven-
tilated lungs in dogs undergoing open thoracotomy. This was believed
to be due to hypoxaemic vasoconstriction in the atelectatic lung
and shunting of blood flow to ventilated regions of lung, reducing
ventilation/perfusion mismatching. Radlinsky (2008), however, high-
lights that single-lung ventilation in ill patients may be more difficult,
and recommends the addition of 5 cmH 2 O positive end expiratory
pressure (PEEP), in an effort to recruit more alveoli in the ventilated
lung and reduce ventilation/perfusion mismatching. Potter and Hen-
drickson (1999) recommend that initially during one lung ventilation
half the tidal volume is used (4–5 ml/kg for a medium-sized dog) with
double the respiratory rate (20 breaths/min), and that this is gradually
changed during the first 30 min to a more normal tidal volume (10 ml/
kg) and respiratory rate (10–12 breaths/min), while maintaining an
airway pressure of 20 cmH 2 O.
At the end of the thoracoscopy procedure, the bronchial endotrachial
tube is withdrawn into the trachea, and the re-ventilation of the atelec-
tatic lung observed with the endoscope. Levionnois et al. (2006) reported
the accidental entrapment of an endobronchial blocker tip by staples
during a lung lobectomy (see below). The author rarely uses single-lung
ventilation, even in lateral recumbency procedures, instead preferring
atraumatic lung retraction if needed.

Safe thoracoscopic access

As for laparoscopy, the optical and instrument ports should not be
inserted over a lesion or target organ, but a reasonable distance away
from and directed towards them to allow good, wide-angle visualisation,
and a suitable operating space. Similarly, instruments should ideally
always be inserted into the chest under visualisation. With limited space