Abstract
Post-operative pain control is one of the key factors that can aid in
fast and safe recovery after any surgical interventions.
Thoracic surgery can cause significant postoperative pain which can lead
to delayed recovery, delayed hospital discharge and possibly
increased risk of chest complications in the form of atelectasis and
even lower respiratory infections. Therefore, appropriate pain
management following thoracic surgery is mandatory to prevent
development of such morbidities including chronic pain.
Keywords:Thoracic Surgery, Analgesia, VATS, Robotics, Thoracotomy
Introduction
Thoracic surgical procedures can result in severe pain
which can present as a challenge to be appropriately managed
postoperatively. In particular, thoracotomies are well known for
their severity of pain due to the incision, manipulation of muscles
and ligaments, retraction of the ribs with compression, stretching
of the intercostal nerves, possible rib fractures, pleural irritation,
and postoperative tube thoracotomy [1]. Recognition of this has
contributed to the development of minimally invasive techniques
such as video assisted thoracoscopic surgeries (VATS) and lately
robotic surgery [1]. These techniques not only aim to produce
better aesthetic results, but also reduce post-operative pain and
enhance recovery without compromising the quality of treatment
offered. Poor pain management can lead to several and serious
complications such as lung atelectasis, hypostatic pneumonia due
to avoidance of deep breathing in these patients as a result of pain
and superimposed infection [1]. Pain management as a result, does
not only lead to greater patient satisfaction, but it also reduces
morbidity and mortality in patients undergoing thoracic surgery
[2]. Historically, post-operative pain management for thoracic
surgery involved the use of narcotics alongside parenteral or oral
anti-inflammatory agents [2]. Post chest tube removal patients
typically are transitioned to oral analgesia. Multiple additional
pain control adjuncts were also implemented with differing levels
of success [1]. Over time, intra-operative techniques have been
developed which aims to target pain reduction postoperatively [2].
As our understanding of both pain management and the factors
that play a role in the development of pain has increased, we have
been able to target these and improve postoperative pulmonary
morbidity and pain scores [1,2]. We aim to review different means
of pain control in this paper in order to assess their effectiveness in
achieving optimum results.
Thoracotomy
The mechanism of pain in thoracotomy involves the innervation
of the intercostal, sympathetic, vagus and phrenic nerves [3].
Additionally, shoulder pain may result from stretching of the joints
during the operation.
After a thoracotomy, pain can persist for two months or more,
and in certain incidences it recurs after a period of cessation.
The incidence of chronic pain post thoracotomy is reported to
be 22-67% in the population [4]. Good surgical technique and
effective acute post-operative pain treatment are evident means
of preventing post-thoracotomy pain and consequent pulmonary
complications [4]. Due to the multifactorial character of the pain, a
multimodal approach to target pain is advised. Typically, both
regional and systemic anaesthesia are administered. A combination
of opioids such as fentanyl or morphine are typically used [5]. A
variety of techniques for the administration of local anaesthetics
are available at present, and the effectiveness of each is assessed
in this paper.
a) Thoracic Epidural Analgesia (TEA)
TEA was the most widely used method of means of analgesia.
It was the gold standard means of pain relief [6,7]. It is typically
inserted prior to general anaesthesia, at the level of T5-T6, midway
along the dermatomal distribution of the thoracotomy incision.
A study by Tiippana et al. [8] measured the visual analogue scale
(VAS) in order to assess the presence of pain during rest and at the
time at which they coughed in 114 patients of whom 89 had TEA
and 22 who had other methods of pain control. TEA was effective
in alleviating pain at rest and during coughing. In TEA patients, the
incidence of chronic pain of at least moderate severity was 11%
and 12% at 3 and 6 months, respectively. The study found that at
one week after discharge, 92% of all patients needed daily pain
medication. The study advised for extended postoperative analgesia
for up to the week post-discharge to be administered in order to
manage this. The study however concluded overall, that TEA was
effective in controlling evoked post-operative pain. However, the
study did encounter problems of technical form in 24% of the
epidural catheters. The incidence of chronic pain, however, was
lower compared with previous studies where TEA was not used.
Several other studies support that TEA is superior to less invasive
methods. According to Shelley B. et al. [9] TEA was preferred by
62% of the respondents over paravertebral block (PVB) with
30% and other analgesic techniques with 8%. Limitations of this
technique included hypotension and urinary retention. Certain
patients with active infection and on anticoagulation are excluded
from epidural placement.
b) Paravertebral Block (PVB)
PVB is considered an effective method for pain management
and its use has been increased in the recent years. This technique
involves injecting local anaesthetic into the paravertebral space and
it is able to block unilateral multi-segmental spinal and sympathetic
nerves. Previous studies have shown that it is effective in achieving
analgesia and is associated with a lower incidence of side effects
such as nausea, vomiting, hypotension and urinary retention
[10,11]. As the lungs are collapsed, it is associated with a lower risk
of pneumothorax.
In a study by Davies R.G. et al. [10] there was no significant
difference in pain scores, morphine consumption and
supplementary use of analgesia between TEA and PVB. The rate of
failed technique was lower in PVB (OR =0.28, p=0.007). Respiratory
function was improved at both 24 and 48 hours with PVB but only
significantly improved at 24 hours.
c) Intercostal Nerve Block (ICNB)
ICNBs are generally administered as single injections at least
two dermatomes above and below the thoracotomy incision [12].
It is performed percutaneously or under direct vision, using single
injections or through placement of an intercostal catheter. It can
also be formed using cryotherapy. It is associated with reduced
post-operative pain scores; however, it is less effective than TEA
in controlling chronic pain [12]. This was illustrated by a study by
Sanjay et al. [12] which found that patients that underwent ICNB
had higher pain scores 4 hours post-operatively, than those who
received epidural anaesthesia using 0.25% bupivacaine (p<0.05).
The study concluded that in the early post-operative period there
was significant impact in pain relief for both techniques, but
thereafter, epidural anaesthesia was proven to significantly reduce
post thoracotomy pain over ICNB. Due to the multifactorial nature
of post-thoracotomy pain, various approaches are required in
order to target pain. ICNBs are useful in the blockade of intercostal
nerves, whilst PVB and TEA appear to block the intercostal and
sympathetic nerves. Due to the inability of regional anaesthesia
to block the vagus and phrenic nerves which are implicated in
the pathophysiology of pain, NSAIDs and opioids are required as
adjuncts. TEA is proven to be the most effective means of treating
pain alongside PVB; however, it is associated with more side effects
than PVB. At present, there are a limited number of studies directly
comparing pain control and post-operative outcomes between PVB
and TEA. There is no conclusive evidence that either method is
superior to the other regarding pain control.
Video-Assisted Thoracoscopic Surgery (VATS)
Existing evidence supports the noninferiority of thoracic PVB
when compared to TEA for postoperative analgesia [13]. PVB
is versatile and may be applied both unilaterally or bilaterally. It
can be used to avoid contralateral sympathectomy, consequently
minimising hypotension. This is an apparent advantage it has over
thoracic epidural. Furthermore, it offers a more favourable side
effect profile when compared to epidural anaesthesia. At present,
the factors taken into consideration when selecting a regional
technique include tolerance of side effects associated with TEA,
consensus on best practice/technique, and operator experience
[13]. A randomised controlled trial by Kosiński et al. [14] compared
the analgesic efficacy of continuous thoracic epidural block and
percutaneous continuous PVB in 51 patients undergoing VATS
lobectomy. The primary outcome measures were postoperative
static (at rest) and dynamic (coughing) visual analogue pain scores
(VAS), patient-controlled morphine use and side-effect profile. The
study found that pain control (VAS) was superior in the PVB group
at 24 hours, both at rest (1.7 vs3.3, p=0.01) and on coughing (5.8
vs 6.6, p=0.023), and control of pain at rest was also superior in
the PVB group at 36 hours (3.0 vs 3.7 (p=0.025) and at 48 hours
(1.2 vs 2.0, p=0.026). There were no significant differences in the
postoperative morphine requirements. In regard to side-effect profile,
the study showed that the incidence of postoperative urinary
retention (defined as no spontaneous micturition for 8 hours
or ultrasound-assessed volume of the urinary bladder >500ml)
was greater in the epidural group (64.0% vs 34.6%, p=0.0036),
as was the incidence of hypotension (32.0% vs 7.7%, p=0.0031).
There was no significant difference in the incidence of atelectasis
(4.0% vs 7.7%, p=0.0542). However, the incidence of pneumonia
was significantly more frequent in the PVB group (3.8% vs 0%,
p=0/0331). Kosiński et al. concluded that PVB is as effective as
thoracic epidural block in regard to pain management as it offers a
superior safety profile with minimal postoperative complications. A
further randomised controlled trial by Okajima et al. [15] compared
the requirements for postoperative supplemental analgesia in 90
patients who received wither a PVB or thoracic epidural infusion
for VATS lobectomy, segmentectomy or wedge resection. The main
outcome measures were pain scores at rest (verbal rating scale
0= none and 10=maximum pain), blood pressure, side effects and
overall satisfaction scores relating to pain control (1=dissatisfied
and 5=satisfied). The study found a similar frequency of
supplemental analgesia (50mg diclofenac sodium suppository
or 15mg pentazocine intramuscularly) for moderate pain in both
groups, with 56% of those in the PVB group requiring ≥2 doses,
compared to 48% in the epidural group (p=0.26). Hypotension,
defined as a systolic blood pressure <90mmHg, occurred more
frequently in the epidural group (21.2% vs 2.8%, p=0.02). There
was no difference in the incidence of pruritus (3.0% vs 0%, p=0.29)
and post-operative nausea and vomiting (30.3% vs 25.0%, p=0.62)
between both groups. The study found no statistical difference
between patient-reported satisfaction in pain control between
epidural and PVB using the verbal rating scale (5.0 vs 4.5, p=0.36).
The study concluded that PVB offered additional to equivalent
analgesia to epidural, a lower incidence of haemodynamic
instability postoperatively. A further study by Khoshbin et al. [16]
performed an analysis on 81 patients undergoing VATS for pleural
aspiration +/- pleurodesis, lung biopsies or bullectomy. The main
outcome was postoperative pain levels, documented every 6 hours
and scored against the Visual analogue Scale (0= no pain, 10=
worst possible pain). In both PVB and epidural groups, bupivacaine
0.125% was the local anaesthetic of choice, with clonidine added
to the epidural infusion at 300μg in 500ml. The study showed that
there was no significant difference in mean pain scores between
PVB or EP (2.1 vs 2.9, p=0.899), therefore concluding that PVB is as
effective as epidural in controlling pain post-VATS.
Robotic Lung Surgery
Minimally invasive techniques are considered advantageous
over open surgical approaches due to their shorter recovery times,
reduced perceived levels of pain post-operatively and shorter postoperative
length of stay in hospital [17-19]. Robotic surgery has
become a popular method in recent years. Debate remains regarding
whether robotic surgery is superior to VATS in regard with pain
reduction. A case control study by Louie et al. [19] compared 45
robotic assisted lobectomies (RAL) to 34 VATS lobectomies. The
study showed that both groups had a similar mean ICU stay (0.9 vs
0.6 days) and a mean total length of stay (4.0 vs 4.5 days). The study
showed that patients that underwent robotic lobectomies had a
shorter duration of analgesic use post-operatively (p=0.039) and
a shorter time resuming to normal everyday activities (p=0.001). A
limitation in this study was an inaccurate record of the amount of
pain relief used by the patients, ultimately working as a confounding
factor when interpreting the results. In a separate study by Jang et
al. [18] 40 patients undergoing RAL were compared retrospectively
to 80 VATS patients (40 initial patients and 40 most recent patients),
all with resectable non-small cell lung cancer. The study showed
that the post-operative median length of stay was significantly
shorter in RAL patients compared to the initial VATS patients. The
rate of post-operative complications was significantly lower in the
RAL group (10%) compared to the initial VATS group (32.5%) and
similar to the recent VATS group (17.5%). Post-operative recovery
was easier for patients in both the RAL and VATS group due to
earlier mobilisation, allowing them to return to their everyday
activities quicker. In a retrospective review by Kwon et al. [17] 74
patients undergoing robotic surgery, 227 patients undergoing VATS
and 201 patients undergoing anatomical pulmonary resection were
assessed and compared with regard to acute (visual pain score) and
chronic pain (Pain DETECT questionnaire). The study showed that
there was no significant difference in acute or chronic pain between
patients undergoing robotic assisted surgery and VATS. Despite
no significant difference in pain scores, 69.2% of patients who
underwent robotic-assisted surgery felt the approach affected their
pain versus 44.2% of the patients who underwent VATS (p=0.0330).
These results all support the superiority of robotic surgery over
VATS and open approaches with regard to pain, length of hospital
stay and recovery times. Both robotic surgery and VATS have
their benefits i.e. two-versus three-dimensional view, instrument
manoeuvrability, and reduced post-operative pain.
Conclusion
Since post-thoracotomy pain is multifactorial, a multimodal
approach is required. In particular, ICNB blocks the intercostal
nerves, and PVB and TEA appear to block the intercostal and
sympathetic nerves. NSAIDs and opioids are required as valgus and
phrenic nerve cannot be blocked by regional anaesthesia. TEA is
evident to be the most effective in treating pain alongside with PVB.
It is however associated with more side effects than PVB.
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