Effects and Dose Response of Dexamethasone on Intercostal Blocks With Bupivicaine in Post Thoracic Surgery Patients

Post-op analgesia is the most important part of early and safe patient recovery in thoracic surgery. This is for both humane and patient outcome reasons. Patient outcomes are greatly improved with optimal pain control and complications and length of stay are minimized. Most post-op thoracic complications are from decreased respiratory effort, failure to clear secretions and pulmonary infections from retained sputum with subsequent sequelae. Good post-operative analgesia not only prevents these complications but also considerably enhances early mobilization and thus, decreased hospital stay and efficient resource allocation. Early post-operative pain is also associated with late and chronic post thoracotomy pain syndromes which can be debilitating.

Pain following thoracic surgery is different to the standard surgical incision pain and is due to intercostal nerve damage, compression or traction injury to the nerve. This occurs with the incision, rib retraction, and is compounded by the on-going need for respiratory effort. The approach to managing this pain is multi-modal analgesia. The standard regimen stretches from preemptive analgesia and preoperative placement of thoracic epidurals to post-op opioid infusions. However, non-invasive pharmacology includes paracetamol, non steroidal anti inflammatory drugs (NSAIDs), mild and moderate opioids as well as anti-convulsants like pregabalin. However, opioid use has well-known side effects including central nervous system (CNS) and respiratory depression which unfortunately delay mobility and recovery. This has motivated opioid-sparing strategies.

The investigators study aims to assess whether the addition of perineural dexamethasone (a steroid) to the current practice of local anaesthetic wound catheters increases the efficacy and duration of analgesia provided.

Recent years have seen the importance of early mobility and respiratory toilet to minimise complications and hospital stay. Newer methods of pain relief with fewer systemic effects have become even more important. Continuous wound infiltration catheters (CWI's) aim to deliver local anaesthetic agents directly into the wound (4). This technique goes back to 1994, and has been established in this hospital and is used in a non-structured manner in thoracic surgery. Recent studies have demonstrated that the addition of dexamethasone (a steroid) to local anaesthetic agents in similar nerve blocks significantly improves the analgesic affect and prolongs the duration of the analgesia. To the best of the investigators knowledge this has not been tested in a thoracic surgery cohort of patients, though it has been tested safely and effectively in the thorax in healthy volunteers and in postoperative analgesia in abdominal and musculoskeletal post op patients. The investigators aim is to assess whether the addition of perineural dexamethasone to the local anaesthetic in CWI's is superior to the local anaesthetic alone in thoracic post operative patients, and at which dose. They also want to assess the levels of pain experienced 1 month post op to evaluate the potential effect of dexamethasone on post thoracoscopy pain syndrome.

The investigators aim is to compare the use of local anaesthetic agent in combination with perineural dexamethasone with the current practice of local anaesthetic alone at relieving pain in the immediate post op pain period. The investigators also want to assess whether the 8mg dose of dexamethasone used in similar studies is the optimal dose or whether a similar effect can be observed at a smaller dose of 4mg.

Eligibility Criteria:
Inclusion Criteria:

* Age \>18
* Consenting
* undergoing VATS procedure

Exclusion Criteria:

* Age \<18
* Refusal to consent
* Equipment failure
* Allergic reactions to local anaesthetic agent
* Incipient agents or opioid
* Patients on pre-existing long-term opioid use
* Any other concomitant or surgery within 2 weeks of the thoracic surgery