TITLE: The role of intercostal nerve preservation in acute pain
control after thoracotomy

  ABSTRACT.OBJECTIVE:
 To evaluate whether the acute pain experienced during in-hospital recovery from
thoracotomy can be effectively reduced by the use of intraoperative measures
(dissection of the neurovascular bundle prior to the positioning of the
Finochietto retractor and preservation of the intercostal nerve during closure).


ABSTRACT.METHODS:
 We selected 40 patients who were candidates for elective thoracotomy in the
Thoracic Surgery Department of the Federal University of São Paulo/Paulista School
of Medicine, in the city of São Paulo, Brazil. The patients were randomized into
two groups: conventional thoracotomy (CT, n = 20) and neurovascular bundle
preservation (NBP, n = 20). All of the patients underwent thoracic epidural
anesthesia and muscle-sparing thoracotomy. Pain intensity was assessed with a
visual analog scale on postoperative days 1, 3, and 5, as well as by monitoring
patient requests for/consumption of analgesics. 

ABSTRACT.RESULTS:
 On postoperative day 5, the self-reported pain intensity was significantly lower
in the NBP group than in the CT group (visual analog scale score, 1.50 vs. 3.29; p
= 0.04). No significant differences were found between the groups regarding the
number of requests for/consumption of analgesics. 

ABSTRACT.CONCLUSIONS:
 In patients undergoing thoracotomy, protecting the neurovascular bundle prior to
positioning the retractor and preserving the intercostal nerve during closure can
minimize pain during in-hospital recovery.

BODY.INTRODUCTION:
A thoracotomy is one of the most painful procedures in surgical practice. The pain that
patients experience in the immediate postoperative period and in the late postoperative
period constitutes a constant concern among thoracic surgeons, because it is well
established that patients with severe postoperative pain are at an increased risk of
developing complications, including atelectasis and pulmonary infection.(

1

,

2

) In addition, chronic pain is a common cause of prolonged work absenteeism
because it often prevents patients from performing their regular activities for months
after the surgical procedure. Many studies have shown that the presence of severe pain
in the immediate postoperative period is associated with a higher occurrence of chronic
pain.(

3

-

5

)
  Postoperative pain assessment is based on individual perception, the subjective nature
of pain and the difficulty in measuring pain intensity making it difficult to
standardize studies addressing the issue of postoperative pain.  Pain resulting from the stimulation of receptors is designated nociceptive (myofascial)
pain. Nociceptive pain after thoracotomy might be due to any of the following: skin
incision; muscle retraction; rib spreading; trauma to sternocostal and costovertebral
joints; intercostal nerve compression; damage to the lung parenchyma; and damage to the
parietal pleura. Intercostal nerve injury can lead to the formation of a localized
neuroma that can cause persistent stimulation and, consequently, hyperalgesia (pain
resulting from noxious stimuli) and allodynia (pain resulting from typically painless
stimuli). In such cases, pain is designated neuropathic pain. Post-thoracotomy pain
syndrome can therefore be defined as a combination of nociceptive and neuropathic
stimuli.(

6

,

7

)
  Many thoracic surgical procedures are currently performed as video-assisted
thoracoscopic procedures; however, pulmonary resections, including those for the
treatment of lung cancer, are not, despite numerous studies showing the advantages of
video-assisted thoracoscopy. According to the American Association for Thoracic Surgery,
video-assisted procedures account for less than 20% of all major pulmonary resections
recently performed in the USA and less than 10% of all major pulmonary resections
recently performed in Europe.(

8

)
  During conventional thoracotomy, two intercostal nerves can be injured unless the
neurovascular bundle is preserved: one by the Finochietto retractor and one by
thoracotomy closure. On the basis of the assumption that post-thoracotomy pain is
primarily due to intercostal nerve injury, postoperative pain can be reduced by avoiding
intercostal nerve crushing.  There are currently three thoracotomy closure techniques: intracostal suture closure
(whereby stitches perforate the rib); subperiosteal suture closure (whereby stitches are
placed between the periosteum and the neurovascular bundle at the lower rib; Figure 1); and pericostal suture closure (whereby
stitches are placed in the middle of the intercostal muscles, thus crushing the
intercostal nerve against the rib).  
Figure 1Schematic illustration of subperiosteal suture placement.
  Cerfolio et al.(

9

) compared post-thoracotomy pain between patients undergoing pericostal
suture closure and those undergoing intracostal suture closure. The authors reported
that intracostal sutures resulted in significantly less postoperative pain. In another
study, postoperative pain was evaluated in patients in whom the neurovascular bundle had
been dissected before retractor placement in order to protect it from being compressed
by the retractor.(

10

) Many groups of authors have attempted to reproduce the results of the two
aforementioned studies,(

11

,

12

) having reached similar conclusions; some have attributed the reduction in
pain to the protection provided by the muscle flap containing the bundle, whereas others
have attributed it to the thoracotomy closure technique.  The present study was designed to compare, in a systematic manner, different techniques
for neurovascular bundle preservation (NBP), in an attempt to determine their efficacy
in reducing pain in the immediate postoperative period and during the in-hospital
postoperative period.

BODY.METHODS:
This was a prospective randomized clinical trial of candidates for elective thoracotomy
in the Thoracic Surgery Department of the Federal University of São Paulo/Paulista
School of Medicine, located in the city of São Paulo, Brazil. The trial was conducted
between January of 2009 and January of 2010. All patients were blinded to the technique
used. We initially selected 142 patients requiring thoracotomy. The inclusion criteria
were being 18 years of age or older and agreeing to participate in the study. Most of
the patients who were initially selected were excluded during the perioperative period
on the basis of the following criteria: need for thoracoplasty or pleurectomy;
occurrence of rib fractures caused by retractor placement; impossibility of performing
epidural anesthesia; impossibility of using a visual analog scale in the postoperative
period (because of prolonged intubation); and need for reintervention.  The study was approved by the Research Ethics Committee of the Federal University of São
Paulo (Protocol no. 1323/09).  Before the surgical procedure, all patients underwent thoracic epidural anesthesia in a
sitting position (puncture at the level of T5-T6), followed by local anesthetic infusion
and epidural catheter placement. The incision was 8-10 cm in length. The latissimus
dorsi was dissected and reflected posteriorly. The serratus anterior was identified,
dissected, and reflected medially.  The intercostal muscles were separated midway between the upper and lower rib edges. A
medium-sized Finochietto retractor with 4-cm blades was used in all procedures.  The patients were randomized into two groups of 20 patients: the conventional
thoracotomy group and the NBP group. In the group of patients undergoing conventional
thoracotomy, the retractor was placed immediately after separation of the intercostal
muscle. After the surgical procedure, intercostal space closure was achieved with
pericostal sutures (absorbable polyglactin 1 suture material). In the NBP group, the
intercostal muscle was dissected together with the neurovascular bundle, over a length
of 5 cm, with the use of an osteotome and electrocautery, being therefore freed from the
upper rib; the muscle flap was subsequently tied by a Penrose drain (Figure 2A) and retracted for the placement of the
Finochietto retractor. After the surgical procedure, intercostal space closure was
achieved with three stitches with subperiosteal sutures (a single layer of absorbable
polyglactin 910 suture material; Figure 2B).  
Figure 2In A, intercostal muscle flap tied by a Penrose drain. In B, periosteal
retraction.
  A visual analog scale ranging from zero to ten (i.e., from "no pain at all" to "the
worst pain I have ever felt") was used for postoperative pain assessment. Patients used
the visual analog scale to rate their pain on postoperative days 1, 3, and 5. All
ratings were performed at 8:00 a.m. before any manual handling of patients, including
bathing, physical therapy, and radiological examinations.  Objective postoperative pain assessment consisted of measuring the consumption of
analgesics by patient demand (analgesics being prescribed and administered on the basis
of self-reported pain).  Analgesia was achieved by the administration of 0.25% bupivacaine with 2 mg of morphine
via an epidural catheter between 10:00 a.m. and 12:00 p.m. on postoperative days 1, 2,
and, 3, the catheter being then removed. We analyzed the following parameters: duration
of surgery; length of hospital stay; duration of chest tube drainage; pain intensity;
consumption of analgesics by patient demand; and complications. Complications included
segmental or lobar atelectasis, pneumonia, prolonged air leak (i.e., air leak for more
than 3 days), and surgical wound complications, including seroma, hematoma, and
infection.  Statistical analysis was performed with the chi-square test and the Student's t-test.
Sample size was calculated by comparison with similar studies,(

11

,

13

) the mean and standard deviation being taken into consideration; the
expected response was 30%, with a value of p < 0.05. A descriptive analysis was
performed with calculations of arithmetic means and standard deviations.

BODY.RESULTS:
Of the 142 patients requiring elective thoracotomy during the study period, 40 (28%)
were included in the study. Patients were excluded for the following reasons: lack of
thoracic epidural anesthesia, in 38 patients; rib fracture during the intraoperative
period, in 24; impossibility of assessing pain intensity (because of prolonged
intubation), in 15; history of chronic analgesic use, in 12; chest wall invasion by lung
cancer, in 8; and need for reintervention, in 5.  The 40 patients included in the present study were randomized into two groups of 20
patients: the conventional thoracotomy group and the NBP group. The mean age was 48.3 ±
14.5 years in the conventional thoracotomy group and 48.8 ± 17.3 years in the NBP group.
The body mass index was 24.6 ± 3.7 kg/m2 in the former and 22.8 ± 4.5
kg/m2 in the latter. Of the 20 patients in the conventional thoracotomy
group, 11 were male, and 7 were smokers. Of the 20 patients in the NBP group, 10 were
male, and 8 were smokers. Table 1 shows the
surgical procedures performed in each group of patients.  
Table 1Surgical procedures in the patients undergoing conventional thoracotomy (n
= 20) and in those undergoing thoracotomy with neurovascular bundle
preservation (n = 20).a Surgical procedures Groups CT NBP Segmentectomy 7 9 Lobectomy 6 8 Mediastinal tumor resection 2 1 Metastasectomy 2 1 Diaphragmatic defect repair 1 Pneumonectomy 1 1 Pleural tumor resection 1CT: conventional thoracotomyNBP: neurovascular bundle preservationaValues expressed as n of patients
  We analyzed the duration of surgery, length of hospital stay, and duration of pleural
drainage in the two groups of patients (Table
2). We found no significant differences between the two groups regarding any of
the aforementioned parameters.  
Table 2Duration of surgery, length of hospital stay, and duration of chest tube
drainage in the groups studied.a Variables Groups p* CT NBP Duration of surgery, min 206.00 ± 112.96 190.32 ± 86.08 0.53 Length of hospital stay, days 6.0 ± 5.3 6.3 ± 3.9 0.85 Duration of chest tube drainage, days 4.6 ± 2.7 4.3 ± 2.6 0.21CT: conventional thoracotomyNBP: neurovascular bundle preservationaValues expressed as mean ± SD*Student's t-test
  Regarding the subjective assessment of postoperative pain, mean visual analog scale
scores were higher in the conventional thoracotomy group than in the NBP group (p =
0.04). Although postoperative pain intensity on postoperative days 1, 3, and 5 was lower
in the NBP group than in the conventional thoracotomy group, the difference was
significant only on postoperative day 5 (p = 0.04; Table 3).  
Table 3Pain intensity, as assessed by visual analog scale scores, in the groups
studied.a Results Groups p* CT NBP Highest score 6.14 ± 3.38 4.12 ± 2.63 0.04 Postoperative day 1 5.29 ± 3.94 3.58 ± 2.30 0.13 Postoperative day 3 2.86 ± 2.47 2.65 ± 1.83 0.51 Postoperative day 5 3.29 ± 2.36 1.50 ± 1.82 0.04CT: conventional thoracotomyNBP: eurovascular bundle preservationaValues expressed as mean ± SD*Student's t-test
  Although the consumption of analgesics (tramadol hydrochloride and dipyrone) by patient
demand was lower in the NBP group than in the conventional thoracotomy group, the
difference was not significant. The mean consumption of tramadol hydrochloride was 1,025
± 464 mg in the conventional thoracotomy group and 834 ± 568 mg in the NBP group (p =
0.22). The mean consumption of dipyrone was 16.67 ± 12.06 g in the former and 15.71 ±
11.73 g in the latter (p = 0.98).  Regarding the occurrence of postoperative complications, there were no significant
differences between the conventional thoracotomy and NBP groups (28.18% vs. 30.77%; p =
0.58). In addition, none of the complications were attributable to the intervention
(dissection of the neurovascular bundle and subperiosteal suture closure).

BODY.DISCUSSION:
Although post-thoracotomy pain is a topic of great interest to thoracic surgeons, few
studies have examined it. This might be due to the lack of objective data to quantify
post-thoracotomy pain. In the present study, we sought to answer a simple question: what
can surgeons do to minimize the pain of patients undergoing thoracotomy?  Although thoracic epidural anesthesia is still considered the gold standard for
postoperative analgesia in thoracic surgery, it can cause nausea, vomiting, dizziness,
and torpor (all of which are due to hypotension), as well as muscle weakness and urinary
retention, in 15-20% of cases.(

14

)
  Thoracic epidural anesthesia is contraindicated in patients with coagulation disorders
and depends on the skill and experience of the anesthesiologist. Thirty-eight patients
were excluded from the present study because of the impossibility of performing epidural
anesthesia (either because it was medically contraindicated or because of technical
difficulties). We do not question the benefits of thoracic epidural anesthesia, which is
routinely used at our facility. However, it is sometimes impossible to use it.  In such cases, one alternative is intercostal nerve block under direct vision, covering
one intercostal space above the incision and one below it, which can be beneficial
within the first 24 h after surgery.  Muscle-sparing thoracotomy is a variant of posterolateral thoracotomy, which is an open
procedure rather than a laparoscopic procedure. During muscle-sparing thoracotomy, the
latissimus dorsi and serratus anterior muscle fibers are separated rather than
sectioned. Although most pulmonary resections can be performed via a muscle-sparing
thoracotomy, the efficacy of this approach in reducing postoperative pain remains
controversial; some authors have suggested that it is ineffective in reducing
postoperative pain,(

15

) whereas others have reported that it significantly reduces postoperative
pain.(

14

) In our study, muscle-sparing thoracotomy was used in both groups, which
were therefore not compared in terms of the technique.  The purpose of our study was to determine the extent to which the techniques that
protect the neurovascular bundle from being compressed by the Finochietto retractor and
the modified intercostal space closure technique can reduce postoperative pain.  Cerfolio et al.(

9

) demonstrated the advantages of intracostal suture closure over conventional
(pericostal) suture closure.  Few studies have examined the issue of intercostal nerve compression by the Finochietto
retractor. Retractor-related factors contributing to the severity of post-thoracotomy
pain include the amount of rib spreading, the size of the blades, and the area of
contact between the retractor and the intercostal nerve.  In a study conducted in 2005, Cerfolio et al.(

10

) proposed that an intercostal muscle flap containing the neurovascular
bundle be harvested before placement of the retractor. The study included 114 patients,
who were randomized to conventional thoracotomy or thoracotomy with intercostal muscle
flap to protect the intercostal nerve. The authors found that the latter technique
reduced postoperative pain.  The chest tube is known to play a role in postoperative pain, chest tube removal being
often associated with a reduction in pain. In the present study, we found no significant
difference between the two groups in terms of the duration of chest tube drainage. The
results might have been different if we had.  In a prospective randomized study of 144 patients undergoing pulmonary resection, Wu et
al.(

12

) sought to determine whether the combination of intracostal suture closure
with intercostal muscle flap provided better pain relief than did intracostal suture
closure alone. Pain intensity was assessed by a visual analog scale in the period
between postoperative day 1 and postoperative day 7, as well as in the period between
postoperative week 2 and postoperative week 12. The combination of intracostal suture
closure with intercostal muscle flap did not reduce postoperative pain when compared
with intracostal suture closure alone.  In a prospective randomized study that involved 120 patients(

11

) and that is similar to the present study, 60 patients underwent intercostal
muscle flap and intracostal suture closure (for intercostal nerve protection) and 60
underwent conventional thoracotomy. Postoperative pain intensity was assessed by a
visual analog scale and by analgesic consumption and was found to be lower at
postoperative week 1 and at postoperative month 1 in the group of patients who underwent
intercostal muscle flap and intracostal suture closure.  In the present study, the two groups of patients were found to be similar in terms of
the length of hospital stay. This finding shows that the intervention reduces
postoperative pain but not the length of hospital stay. This was not taken into
consideration in studies similar to ours.(

10

-

12

) We believe that this is due to the fact that postoperative pain is quite
common and therefore a factor that is not relevant to discharge planning.  In the present study, the two groups were similar in terms of complication rates, and
the intervention was ineffective in preventing the most common post-thoracotomy
complications. Atelectasis and pneumonia are chief among the complications on which a
reduction in pain might have any impact. In the present study, atelectasis occurred in 3
of the patients in the conventional thoracotomy group and in 2 of those in the NBP
group. This difference might have reached statistical significance had our study
involved a larger sample size. None of the complications observed in the present study
were attributable to the intervention performed.  We conclude that the harvesting of an intercostal muscle flap before placement of the
retractor and thoracotomy closure with subperiosteal sutures are measures that are not
associated with additional morbidity or longer duration of surgery and can reduce
in-hospital postoperative pain in patients undergoing thoracotomy.

Question: Compared to conventional thoracotomy (CT) what was the result of neurovascular bundle preservation (NBP) on postoperative pain on day 5?
Evidence: Although postoperative pain intensity on postoperative days 1, 3, and 5 was lower
in the NBP group than in the conventional thoracotomy group, the difference was
significant only on postoperative day 5 (p = 0.04; Table 3).  
Answer: significantly decreased