1. DR AFTAB HUSSAIN POST OP ANALGESIA IN THORACIC SURGERY
2. Pain What is pain? An unpleasantsensory and emotional
experience associated with actualor potential tissue damage, or
described in terms of such damage.
3. Anatomy and pathophysiology of pain in thoracic surgery
Nociceptive transmission is via C and Ad fibres and can be
considered in three discrete routes. 1. Intercostal nerves carry
impulses from the skin and intercostal muscles. 2. Stimuli from
lung and mediastinum are carried by the vagus nerve. 3. The
visceral pleura is relatively insensitive, except to stretch.
Parietal pleura, which is highly sensitive to noxious stimuli,
receives innervation from intercostal and phrenic nerves.
4. Anatomy and pathophysiology of pain in thoracic surgery
contd. In addition, latissimus dorsi and serratus anterior are
supplied by the thoracodorsal and long thoracic nerves,
respectively. These arise from roots C5C7 via the brachial plexus
Thoracotomy for lung resection usually involves a skin incision at
the 5th intercostal space, a variable degree of muscle cutting and
either excision or division of a rib.
5. Nerve supply of thorax Intercostal nerve
6. Anatomy and pathophysiology of pain in thoracic surgery
contd. Oesophageal surgery requires a lower incision, usually
around the 7th intercostal space. Forceful retraction of the wound
is needed to achieve reasonable access and this frequently causes
pressure on the intercostal nerves and may cause acute intercostal
neuritis. Other sites damaged by retraction are the anterior and
posterior intercostal articulations.
7. Anatomy and pathophysiology of pain in thoracic surgery
contd. Up to three chest drains may be inserted after thoracotomy.
Shoulder pain is a common complaint after thoracotomy. Furthermore,
patients may well be extremely anxious after major thoracic
surgery, exacerbating the perception of postoperative pain.
9. The choice of analgesic technique When no contraindication
to central neuraxial or regional analgesia exists, this is commonly
accepted as the best approach. When this is impossible, whether
attributable to local or systemic infection, refusal by the patient
or anatomical difficulties, parenteral opioid infusion is the
technique of choice.
10. The choice of analgesic technique contd. In order to
deliver good quality analgesia, a reliable method of feedback from
patients is needed so that analgesia can be optimized. Assessment
of pain relief in patients after thoracotomy should take
intoaccount dynamic analgesia, with pain scores reflecting
functional ability to cough and breath deeply.
11. The choice of analgesic technique contd. Appropriate
regimens or drugs may be prescribed, but unless there is adequate
communication between anaesthetists, surgeons and nurses, these may
fail to reach the patient at the right time. Appropriate
anti-emetic therapy and avoidance of potent emetic stimuli can
reduce the likelihood of vomiting, a painful event in the
postoperative period.
12. Analgesic approaches There are a selection of analgesic
techniques which have been refined to give good pain relief with
minimal side-effects. There are systemic methods which includes 1.
Systemic infusion 2. Patient-controlled analgesia (PCA) 3. Regional
techniques that mainly rely on epidural, intrathecal or
paravertebral blocks. 4. Other techniques range from intercostal
nerve block to cryoprobe neurolysis.
13. Parenteral opioid infusions Reasonable analgesia can be
achieved with i.v. opioid infusions. PCA is often not effective
immediately after thoracotomy as patients are often too drowsy to
use the demand button properly. Where parenteral opioids are used,
whether by infusion or PCA, adequate loading doses must be given to
achieve therapeutic plasma concentrations. Side-effects
(respiratory depression and inhibition of the cough reflex) are
undesirable after thoracotomy.
14. Patient controlled analgesia
15. Epidural analgesia Epidural analgesia is considered gold
standard. The catheter is sited at a level corresponding
approximately with the midpoint of the dermatomal distribution of
the skin incision. Thoracic epidural analgesia is superior to
lumbar epidural analgesia. Epidural local anaesthetics increase
segmental bioavailability of opioids in the cerebrospinal fluid and
increase the binding of opioids to receptors and the blocking of
the release of substance P in the substantia gelatinosa of the
dorsal horn of the spinal cord.
16. Epidural analgesia contd. Minimize motor and sympathetic
blockade, maintain conscious level and cough reflex and reliably
produce increased analgesia with movement and increased respiratory
function after thoracotomy. The epidural mixture can be
administered either as a continuous infusion, by patient controlled
epidural analgesia (PCEA) or a combination of the two. PCEA allows
easy supplemental boluses before mobilizing or physiotherapy.
17. Drawbacks of Epidural analgesia Failure rate of up to 15%,
even in experienced hands. Placement of a thoracic epidural
catheter may be technically difficult because of caudal angulation
of the spinous processes and spinal cord damage is more likely than
with lumbar placement. Consequential bilateral sympathetic blockade
frequently causes hypotension, especially in this group of patients
who are managed in a relatively hypovolaemic state. This may
require the infusion to be stopped. Motor blockade of intercostal
muscles may reduce the effectiveness of coughing, especially in
patients who already have a low FEV. The technique is
contraindicated in the presence of local or systemic sepsis, for
example in active empyema.
18. Epidural analgesia technique
19. Intrathecal opioids Preservative-free opioids introduced
into the lumbar subarachnoid space will produce analgesia extending
cranially to varying extents depending on the volume, strength,
baricity of solution and choice of opioid. Highly lipid soluble
drugs such as fentanyl and diamorphine tend to penetrate the spinal
cord easily and consequently act rapidly with restricted cranial
spread.
20. Intrathecal opioids contd. Morphine, possessing lower lipid
solubility, tends to spread within the cerebrospinal fluid to the
thoracic region more readily. Intrathecal opioid of choice for use
in thoracotomy Doses range 520 mg /kg of morphine intrathecaly.
Total dose may be the biggest factor affecting spread and magnitude
of effect, but increasing the total volume and performing barbotage
can increase cranial spread.
21. Intrathecal opioids contd. Single intrathecal injections of
morphine have been successfully used pre- or intraoperatively to
provide 1224 h of postoperative pain relief. They need to be
followed with some other form of analgesia. Boluses of i.v.
morphine and/or combined with intercostal nerve blocks are common
rescue methods of pain relief in the recovery ward for severe pain.
The technique avoids the need for an infusion catheter connected to
an infusion pump.
22. Adverse effect of intrathecal morphine Delayed sedation and
respiratory depression caused by excessive rostral spread. This
delayed respiratory depression is of slow-onset and associated with
progressive somnolence. Urinary retention , pruritus, and nausea
and vomiting are side-effects of both epidural and intrathecal
techniques. As with any technique involving dural puncture,
headache is also a risk.
23. Paravertebral blocks Paravertebral blockade offers one of
the best options for post-thoracotomy analgesia. The paravertebral
space is a wedge shaped area immediately lateral to the
intervertebral foramen. It communicates above and below with
adjacent paravertebral spaces. The intercostal nerve passes through
the space without a fascial sheath, where it can be reliably
blocked with local anaesthetic. At this point the nerves lie
outside the parietal pleura.
24. Paravertebral blocks contd. Paravertebral block may be
given as an infusion via a catheter placed with a Tuohy needle.
This can either be inserted using loss of resistance as in placing
an epidural catheter or under direct vision by the surgeon at
thoracotomy. Plain local anaesthetic solutions (bupivacaine
0.250.5%) or equivalent are generally used at a rate of 1015 ml/ h
Advantages of paravertebral blockade lie mainly in the fact that
the concomitant sympathetic and motor blocks are unilateral and
that opioids are not needed in the mixture. This results in less
hypotension, better preserved respiratory function and less stress
response.
25. Paravertebral blocks contd. Additional analgesics such as
NSAIDs may be given to appropriate patients and parenteral opioids
in the form of PCA may be used to supplement analgesia.
Neurological damage and CSF tap are potential complications.
Surgically placed catheters may give more reliable results.
26. Anatomy of paravertebral space and technique of block
27. View of the paravertebral space before percutaneous PVB
under direct vision. epidural needle tip is seen to tent pleura
lateral to the PVS in the medial aspect of the intercostal space.
The PVS is seen to fill beneath the pleura
28. Intercostal nerve blocks Unilateral intercostal blocks are
quick and simple to perform. Single injections for two or three
intercostal spaces above and below the incision have the advantage
of localized analgesia without the risks of sympathetic nerve
blockade. Technique is short-acting. Multiple intercostal catheters
can be sited but are generally too time-consuming.
29. Intercostal nerve blocks contd. The intercostal nerve gives
off a posterior division shortly after it emerges from the
intervertebral foramen Limitations of intercostal nerve blockade is
that it is usually performed anterior to this point (especially
above the 6th rib because of the presence of the scapula),
resulting in inadequate posterior analgesia. Large volumes of local
anaesthetic are needed if multiple injections are performed and it
is easy to exceed the toxic dose inadvertently.
30. Anatomy of intercostal nerve Technique of intercostal
block
31. Inter-pleural analgesia Local anaesthetic (bupivacaine
0.250.5%) may be injected between visceral and parietal pleura
either as a single bolus or as an infusion via an indwelling
catheter. The procedure can be performed either by the anaesthetist
when the chest is closed or by the surgeon when the chest is open.
The technique has been found to have some benefit but local
anaesthetic tends to pool in dependent areas and is also lost
through chest drains, limiting effectiveness.
32. Anatomy and technique of interpleural injection
33. Limited analgesic efficacy of interpleural analgesia
include (1) loss of local anesthetic through the chest tube (2)
dilution of local anesthetic with blood and exudative fluid present
in the pleural cavity (3) Binding of local anesthetic with proteins
(4) altered diffusion across the parietal pleural following
surgical manipulation and inflammation
34. Phrenic Nerve Infiltration Patients undergoing thoracic
surgery frequently complain of ipsilateral shoulder pain due to
diaphragmatic irritation. This pain is often not covered with the
band of analgesia achieved with epidural pain management.
Infiltration of 10 mL of 1% lidocaine into the periphrenic fat pad
at conclusion of surgery at the level of the diaphragm in patients
undergoing thoracotomy significantly decreased incidence of
ipsilateral shoulder pain. This may be a simple and effective
technique for optimizing postoperative pain control when used in
conjunction with epidural analgesia.
35. Cryoprobe neurolysis The technique of destroying individual
intercostal nerves by intraoperative application of a low
temperature probe has been used to provide analgesia. The results
may last for 3 months until the nerves grow back by axonal
regeneration. This suffers from the problem of missing the
posterior division, which supplies the posterior ligaments, muscles
and skin. Significant long-term morbidity such as neuralgia and
paraesthesia are commonly seen, and this technique is rarely used
today.
36. Intercostal nerve cryoprobe neurolysis
37. Balanced analgesic technique Wherever possible, use should
be made of synergistic, multimodal analgesia. Regional and
neuraxial methods (such as epidural with local anaesthetic alone or
combined with opioids) have advantages, some afferent routes will
not be blocked by the techniques described above (for example
diaphragmatic irritation via the phrenic nerve). Regular
paracetamol, parenteral or oral opioids and, where appropriate,
NSAIDs are good choices and also assist when stepping down from
regional and neuraxial techniques.
38. Systemic Treatment Options NSAIDS Nonsteroidal
anti-inflammatory drugs (NSAIDs) are useful in pain states, and
work by inhibiting the cyclooxygenase (COX). Ketorolac is an NSAID
available in a parenteral form, and it has been shown to be an
effective adjunct agent to improve the quality of intercostal and
epidural analgesia. Tramadol Tramadol is a unique, non opiate drug
with an unclear mechanism of action. It binds to opiate receptors
and inhibits epinephrine and serotonin reuptake, but lacks many of
the side effects associated with other drugs with similar sites of
action.
39. Systemic Treatment Options CONTD. Ketamine Ketamine confers
analgesia by blocking the NMDA receptor. NMDA receptor is involved
in central sensitization, making ketamine a logical choice in
preemptive pain management. Ketamine, administered by the systemic
or epidural route, improves postoperative analgesia for abdominal
surgery, although it is not entirely clear whether these effects
reflect a preemptive action of the drug, or a direct analgesic
effect.
40. Systemic Treatment Options CONTD. N-Type Calcium-Channel
Blockers N-type channel blocker Pain events are signaled through
voltage-sensitive, calcium- channel conduction. Subtypes of
calcium-channel blockers includes types L and N. Ziconotide, a
neuronal N-type channel blocker derived from the venom of the
fish-hunting marine snail (Conus magnus), exerts its analgesic
effect by hindering the influx of calcium needed to induce
neurotransmitter release in the signaling of pain . Currently,
ziconotide is being recommended for Food and Drug Administration
(FDA) approval for malignant and nonmalignant pain syndromes DOSE
2.4 mcg/day ,intrathecaly , used only in medtronic synchromed
infusion systems
41. Preemptive analgesia and thoracotomy Preemptive analgesia
is intended to prevent the establishment of central sensitization
caused by incisional and inflammatory injuries. Evidence indicate
that analgesic drugs are more effective if administered before,
rather than after, a noxious stimulus The benefit of pre-emptive
analgesia has been supported by some clinical studies using local
anesthetics , opioids , and non-steroidal anti-inflammatory drugs.
However, the clinical usefulness of pre-emptive analgesia has
remained controversial.
42. Impact of analgesia on outcome Good pain relief is an
obvious humanitarian issue. Consequences of poor analgesia can be
costly in terms of human life and in the cost to the health care
provider. Shallow breathing and impaired coughing resulting from
postoperative pain are a major cause of atelectasis and retention
of secretions , which can lead to hypoxaemia, hypercapnia and
respiratory failure, especially in patients with pre-existing lung
disease.
43. Impact of analgesia on outcome Acute pain causes increased
sympathetic tone accompanied by increased myocardial oxygen demand,
increased afterload, myocardial dysfunction and arrhythmias. Poor
analgesia may also result in a delay in mobilizing patients,
resulting in an increased incidence of deep venous thrombosis and
pulmonary embolism. It has been demonstrated that poor analgesia is
associated with increased ICU admissions, and longer stays in ICU
and hospital overall.
44. Conclusion : Thoracotomy is one of the most painful
surgical procedures Analgesic plan should start preoperatively .
Multimodal approach by modulating different pain pathways. Mid
Thoracic epidurals are the standard of analgesia. Extradural
,intercostal and paravertebral catheters are gaining popularity and
are excellent alternative. .
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Guerrero M.Analgesia after thoracotomy: epidural
fentanyl/bupivacaine compared with intercostal nerve block plus
intravenous morphine. J Cardiothorac Vasc Anesth 2004; 18: 3226 3.
Atlas of pain management injection techniques , S.Waldman, 3rd
edition. 4. Waldman pain management , S.Waldman, 2nd edition 5.
Watson DS, Panian S, Kendall V, et al. Pain control after
thoracotomy: bupivacaine versus lidocaine in continuous
extrapleural intercostal nerve blockade. Ann Thorac Surg
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THORACOTOMY
