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Original Article
Anesthesia with nontracheal intubation in thoracic surgery
1Department of anesthesia; 2Department of Cardiothoracic Surgery, The First Hospital Affiliated to Guangzhou Medical College;
3Guangzhou Institute of Respiratory Disease, State Key Laboratary of Respiratory Disease, Guangzhou 510120, China
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Abstract
Objective: To study one-lung respiration during VATS wedge resection of bullae and pulmonary nodules with nontracheal intubation, and to explore the changes of vital signs when patients return to two-lung ventilation. Methods: Twenty-two patients with normal cardiopulmonary function and absence of contraindications to epidural anesthesia were included in this study. VATS wedge resection of bullae or pulmonary nodules was performed. 0.5% Ropivacain was administrated for epidural anesthesia (T8-9), and 2 mL of 2% lidocaine was used for local anesthetic block of the intrathoracic vagus nerves. The BIS value was maintained between 50 and 70 by target-controlled infusion of propofol and remifentanil. Electrocardiogram (ECG), heart rate (HR), blood pressure (Bp), pulse oxygen saturation (SpO2), respiratory rate (RR), bispectral index (BIS) and urine volume were monitored. Results: None patients were converted to endotracheal intubation during anesthesia. MAP and SpO2 after wound disclosure were stable (P>0.05), level of CVP significantly elevated, HR and RR increased (P<0.05), PaCO2 increased gradually while PaO2 remained stable. Fifteen minutes after wound closure, MAP, RR and SpO2 returned to their preanesthesia levels, PH value gradually recovered, PaCO2 tended to decrease and returned to normal one hour after wound closure. Physical agitation occurred in one case due to inadequate epidural anesthesia during skin incision. Cough before intrathoracic vagal blockade was noted in two cases (9.1%) because of lobe traction. Conclusions: Nontracheal intubation is feasible in VATS wedge resection of bullae and pulmonary nodules. The patients are with stable intraoperative vital signs and none experiences hypoxemia; intraoperative hypercapnia is tolerable and transient, which can be improved quickly when bilateral lungs resume spontaneous respiration. Key words
Anesthesia; nontracheal intubation; thoracic surgery
J Thorac Dis 2012;4(2):126-130. DOI: 10.3978/j.issn.2072-1439.2012.03.10
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Introduction
As lung separation techniques and anesthesia management
advances in thoracic surgery, video-assisted thoracic surgery rapidly develops as well. As a result, the operating time and
surgical trauma in wedge resections of bullae and pulmonary
nodules have been significantly reduced. Since Pompe reported
awake VATS wedge resection of solitary pulmonary nodules under
thoracic epidural anesthesia in 2004, thoracic sympathectomy,
lung metastases resection, pulmonary nodule resection,
pulmonary bulla resection, biopsy of lung and pleura, resection
of mediastinum nodules and pulmonary lobectomy in a similar
anesthetic manner have continually been reported (1-7).
Although VATS wedge resection of bullae and pulmonary
nodules with nontracheal intubation has been proven to be
feasible, various factors, such as spontaneous respiration with
one-lung ventilation during operation, intercostal muscle
damage induced by thoracic epidural anesthesia intravenous
administration of sedatives and analgesics, and operative position,
may aggravate respiratory impairment, causing hypoxemia and
hypercapnia, or even serious complication as well.
In addition, as for VATS operations under anesthesia with
nontracheal intubation, it is not clear how the vital signs, such as respiration and circulation, will change during one-lung
ventilation. Moreover, the trend and time of vital signs recovery
after conversion to two-lung ventilation have not been reported.
This clinical observation of 22 cases of VATS wedge resection of
bullae or pulmonary nodules under anesthesia with nontracheal
intubation explored changes of the vital signs during one-lung
ventilation and subsequent two-lung ventilation.
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Patients and methods
Research design
Anesthesia protocols were audited and approved by the Hospital
Ethical Committee. The inclusion criteria for subjects were
ASA I-II, age between 18 and 65, BMI <25, Mallampati grade
I-II, little airway secretion and absence of epidural puncture
contraindication. VATS wedge resections of bullae and
pulmonary nodules were performed. Anesthetic protocols were
explained to the participants before the informed consent was
obtained.
Anesthesia
Patients received intramuscular Midazolam 0.06 mg/kg
and Atropine 0.01 mg/kg 30 minutes before anesthesia.
Electrocardiogram (ECG), heart rate (HR), blood pressure
(Bp), pulse oxygen saturation (SpO2), respiratory rate (RR)
and bispectral index (BIS) and urine volume were continuously
monitored after the patients entered the operation room. The
thoracic epidural catheter was inserted at the T8-9 interspace,
3 cm towards the head, after intravenous infusion had been
established. 2 mL of 2% Lidocaine was injected with the patients
in supine position. Five minutes after the injection when no
abnormal reaction to the anesthesia was observed, 3 mL of 0.5%
Ropivacain was administrated followed by re-injection of another
3 mL 5 minutes later to reach a level of anesthesia between T2 and
T10. Target-controlled infusion of Propofol and Remifentanil was
started, and the BIS value was maintained between 50 and 70 by
adjusting target concentration. During the whole research process,
nasopharyngeal airway and face mask were used for oxygen
inhalation, with an oxygen flow of 3-5 L/min.
Catheters were inserted via the right internal jugular vein or
the right subclavian vein to continuously monitor the central
venous pressure (CVP). And catheterization via the radial
artery was performed to continuously monitor the invasive
blood pressure (IBP). An incision into the chest wall on the
operated side caused pulmonary collapse, leading to iatrogenic
pneumothorax. Patients received local administration of 2 mL of
2% Lidocain injected under thoracoscopic guidance to achieve
local anesthetic block of the intrathoracic vagus nerves. After the
pleural cavity was closed and the wound was sutured, a face mask
was used to assist the patients in ventilation to inflate the lung
tissue. After the target controlled infusion was stopped and the
epidural catheter was removed, the patients were transferred to a
post anesthesia care unit (PACU).
If SpO2 gradually decreased below 90% during anesthesia, a
face mask was needed to assist ventilation in order to improve
systematic oxygenation; if PaCO2 ≥80 mmHg, operation had to
be suspended and mechanical ventilation was delivered via a face
mask to assist gas exchange. If ventilation could not be improved
by the face mask, endotracheal intubation would be resorted.
Vital signs were monitored at pre-anesthesia, before and 15, 30,
45 minutes after wound disclosure as well as 15, 30, 45 minutes
after wound closure. At the above time points, arterial blood
was simultaneously extracted for blood gas analysis to detect
values of pH, PaO2, PaCO2 and Lac. Operating time, arrhythmia,
physical agitation, coughs before and after local anesthetic block
of the intrathoracic vagus nerves and the cases transferred to
endotracheal intubation were all recorded.
Statistical analysis
Primary outcome measures included values of HR, SpO2, RR,
Bp, CVP and arterial blood gas analysis. Secondary outcome
measures included BIS, operating time, physical agitation and
coughs. Age, height, weight and BMI were expressed by average
value ± standard deviation. Two-sample t-test was used for
statistical analyses. All data were analyzed with SPSS 13.0. A P
value of <0.05 was considered statistically significant.
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Results
From July to December of 2011, 9 VATS resections of bullae
and 13 wedge resections of lung nodules were performed under
combined anesthesia with epidural block, local block of the
thoracic vagus nerve and analgesic sedation.
The general clinical data of the patients were detailed in
Table 1. Their average age was 39.18±18.52 years and their
average BMI was 20.57±2.35. No arrhythmia was found by ECG
monitoring. No patients needed conversion to endotracheal
intubation during anesthesia. Physical agitation caused by
inadequate epidural anesthesia was noted in one case (4.5%)
during skin incision. Cough occurred before local anesthetic
block of the vagus nerves in two cases (9.1%), which was caused
by stretching of pulmonary lobes when exploring and exposing
the vagus nerves, but no cough occurred after completion of the
vagus nerve blockade.
The HR and SpO2 values before wound disclosure were almost
the same as those before anesthesia; the BIS value obviously
declined by 28.8% (P<0.01); the mean arterial pressure (MAP)
slightly declined by 15.4%; the respiration rate decreased by 30.3%
(Table 2). The changes of operative indexes after wound disclosure were detailed in Table 3. The MAP and SpO2 changed slightly
(P>0.05) while the CVP rose significantly; the sedation level
deepened with gradually decreased BIS value; HR and respiratory
rate (P<0.05) gradually increased; acidemia was gradually
aggravated with increasing PaCO2 but no hypoxemia occurred
after PaO2 was maintained stable.
Compared with those before anesthesia, the MAP, RR and
SpO2 values 15 minutes after wound closure returned to their
pre-anesthesia levels. Patients were still in light sedation, with
slightly increased HR and BIS value of 73.4±13.6 (Table 4).
Under spontaneous respiration with oxygen inhalation via a
nasal tube (2-3 L/min), arterial blood gas analysis showed that
PH value gradually recovered and PaCO2 tended to decrease
but returned to normal one hour after wound disclosure. The
oxygenation index significantly declined 15 minutes after
thoracotomy but recovered to that before thoracotomy 30
minutes later. Although the value of Lac after thoracotomy was
higher than that before wound disclosure, both Lac values were
within the normal range (Table 5).
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Disussion
The present study enrolled subjects to undergo VATS bullectomy
or lumpectomy which can be accomplished simply and in a short
time. In our series, the operation duration was (57.5±14.2) min,
and the duration from wound disclosure to closure when the
negative pressure restored in the thoracic cavity in all cases did
not exceeded 45 minutes. As a result, we did not have a long time
to observe the pathophysiologic changes after pneumothorax.
Incisions through the chest wall for VATS are generally made
between the 4th and 7th costal interspace, so we chose the T8/9
thoracic interspace as the puncture site to perform thoracic
epidural blockade because it could maintain effective analgesia
in the operative field. In this study, limb agitation occurred during skin incision due to insufficient epidural anesthesia in one
patient, whose operation was then completed after further TCI
anesthesia.
Cough reflex is a complicated process of neuro-physiological
reflex. The cough center is located in the solitary nucleus over the
medulla oblongata area of the brain, associated with respiratory
neurons. Cough receptors are located mainly on the posterior
wall of trachea, pharynx, and mucosa of bronchus. Receptors
above secondary bronchi are sensitive to mechanical stimuli
while those below are sensitive to chemical stimuli. Impulses
caused by stimuli travel via the vagus nerve to the medulla of the
brain and trigger a cough. Two cases in our study coughed during
operative exploration and lobe traction before intrathoracic
vagal blockade, but none had operation-irritated cough during
the whole procedure after local anesthesia with lidocaine over
the intrathoracic vagus nerve. This indicates intrathoracic vagal
blockade may effectively prevent cough reflex, which is in
consistency with another relevant study (7).
While patients maintained spontaneous breathing during
anesthesia, the operated lung collapsed after iatrogenic
pneumothorax. Moreover, factors related to operation and
anesthesia aggravated the impaired respiratory function,
mainly as follows: (I) decreased activity of the non-operated
thoracic cage due to operative posture related compression;
(II) further decreased activity of the thoracic cage caused by
impaired intercostal muscle function following thoracic epidural
anesthesia; (III) inhibition of the respiratory center caused by
any anesthetic, sedative and analgesic agent; (IV) paradoxical breathing due to the collapse and insufficiency of the operated
lung; (V) muscle flaccidity over the laryngopharynx in sedation
which may produce and accelerate glossoptosis, leading to upper
respiratory obstruction and aggravating paradoxical respiration
and mediastinal flutter.
We strictly selected subjects with good cardiorespiratory
functions and without difficult airway. The patients breathed
oxygen through a ventimask during the procedure to maintain a
good oxygenation index, with SpO2 above 95%. When epidural
anesthesia worked and TCI analgesia was administered, the
breathing slowed down and hypercapnia was observed. When
iatrogenic pneumothorax occurred on the operated side, the
respiratory rate grew compensatingly and PaCO2 increased
continuously, which reached to the peak 15 minutes after
pneumothorax but began to relieve slightly 30 minutes later.
We consider that the hypercapnia occurring in this procedure is
tolerable and has little effect on the hemodynamics. It is believed
that the increase of PaCO2 along with the decrease of pH mainly
depends on the increasing speed of PaCO2 and functional
compensation of the kidney. The side effects and tolerance
of hypercarbia are mainly related to the cardiovascular and
cerebrovascular status of the patients. Studies have indicated that
permissive hypercarbia relieves as well as deteriorates cerebralischemia-
reperfusion injury in rats. Which role it will play is
closely correlated with its severity. In a range of 60-100 mmHg,
PaCO2 relieves cerebral-ischemia-reperfusion injury in rats by
inhibiting neuron apoptosis while it aggravates cerebral edema
induced by cerebral-ischemia-reperfusion injury in a range of
101-120 mmHg (8). Propofol may significantly decrease the
intracranial pressure and maintain the balance of cerebral oxygen
supply and demand in patients with permissive hypercapnia (9).
Patients breathed with bilateral lungs after wound closure,
lung dilatation and thoracic negative-pressure drainage. The
arterial blood gas analysis 15 minutes later showed all values
returned almost to their levels before wound disclosure. Our
results also showed that the hypercapnia during pneumothorax
was quickly and effectively improved after operation, particularly
one hour later.
The blood pressure before operation was lower than that
before anesthesia, which was induced by epidural anesthesia
and TCI sedation. Thoracic epidural blockade may significantly
influence the thoracic sympathetic nerve system, inducing
vasodilatation and decreased blood pressure. The arterial
blood pressure maintained basically normal after iatrogenic
pneumothorax, with no arrhythmia noted by continuous ECG
monitoring, which indicates that the mediastinal flutter has no
significant influence on circulation. The increases of heart rate
and CVP may be compensations for the slowed down venous
return following the disappearance of negative pressure in
unilateral thoracic cavity.
In the present study, we demonstrated that VATS wedge
resection of bullae and pulmonary nodules with nontracheal
intubation are feasible in operations that can be accomplished in
a short time. Patients can maintain stable intraoperative physical
signs without severe hypoxemia. The intraoperative hypercapnia
is tolerable and transient and can be improved quickly when
the bilateral lungs resume spontaneous respiration. Further
research, however, is still to be further studied to characterize the
hypercarbia 30 minutes after pneumothorax and to explore its
systematic impacts.
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References
Cite this article as: Dong Q, Liang L, Li Y, Liu J, Yin W, Chen H, Xu X, Shao
W, He J. Anesthesia with nontracheal intubation in thoracic surgery. J Thorac
Dis 2012;4(2):126-130. doi: 10.3978/j.issn.2072-1439.2012.03.10
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±s).
