Pain control in Throracic Surgery

PAIN CONTROL IN THORACIC SURGERY

For all the happiness man can gain is not in

pleasure but rest from pain.

John Dryden (1631–1700)

Postoperative pain relief is not solely for the relief of an unpleasant sensation. Disturbances of pulmonary function are common after any form of intrathoracic operation. A decrease in functional residual capacity (FRC) with minimal change in closing volume leads to atelectasis

PAIN CONTROL IN THORACIC SURGERY


(Sabanathan et al. 1990). Patients also experience an inability to cough effectively, thus becoming prone to sputum retention leading to infection and arterial hypoxaemia (Ali et al. 1974). Pain from the incision site and drains can be severe for up to three days (Kaplan et al. 1975) and abnormal patterns of breathing owing to pain will only worsen these problems.

Good postoperative pain control is essential in order to carry out effective physiotherapy. This can be delivered in several ways: epidural anaesthesia, paravertebral block, patient-controlled analgesia (PCA), transcutaneous nerve stimulation (TENS) and oral analgesia are the most commonly used.

Epidural anaesthesia

An epidural provides delivery of a local anaesthetic agent, such as bupivicaine, and an opiate, such as fentanyl, directly into the small space just outside the dura mater – the ‘epidural space. The local agent will provide dermatomal relief over the incision site and the opiate a more central effect. Epidurals can provide profound analgesia in considerably smaller doses of opiate drug than if used systemically (Chaney 1995). This will minimise the unwanted side effect of respiratory depression commonly seen in opiate use. Lui et al. (1995) demonstrated improved analgesia with physiotherapy in thoracotomy patients using bupivacaine epidurals. An epidural will be inserted by an anaesthetist before the operation begins.

Paravertebral block

If it is not possible to insert an epidural, continuous delivery of a local anaesthetic agent can be achieved using a paravertebral catheter positioned in the paravertebral groove. This can provide safe and effective pain relief after thoracotomy (Inderbitzi et al. 1992). The catheter will be sited by the surgeon prior to closure of the chest.

Patient-controlled analgesia

PCA allows the administration of small doses of intravenous opioids on demand by the patient. The patient must be awake, co-operative and have had adequate instruction pre-operatively on how to use the system. The dose delivered is dependent upon patient weight. A ‘lock-out’ interval is set to allow time for the opiate to work; this also prevents overdosing.

Transcutaneous nerve stimulation

TENS can be useful if it is initiated postoperatively to relieve referred shoulder pain. The phrenic nerve supplies the diaphragm and if irritated during surgery patients can experience ipsilateral referred shoulder pain (Scawn et al. 2001). TENS can also be of benefit in patients with persistent wound pain when an epidural or paravertebral has been removed.

Oral analgesia

Epidurals, paravertebrals and PCAs will continue, on average, for 72 hours, but analgesia will still be required for many days. The pain experience is individual and oral analgesia required will vary from patient to patient. Simple analgesia, such as paracetamol or ibuprofen, may be adequate, but some patients require stronger medication, such as dihydrocodeine or diclofenac. Oral medication can be prescribed on a regular or an ‘as required’ (p.r.n.) basis. Most hospitals will have a specialist nurse for pain control. The nurse will be very helpful in the care of patients with severe pain that is difficult to control on standard analgesia.

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