Early Versus Late Paravertebral Block for Analgesia in Video Assisted Thoracoscopic Lung Resection.

All patients will receive a general anaesthetic for their VATS procedure with full AAGBI monitoring and the WHO surgical safety checklist will be performed appropriately prior to skin incision. Induction of anaesthesia will be standardised by using propofol and the patient will be paralysed using the muscle relaxant atracurium. The amount given will be at the anaesthetist's discretion and dependent on the patient. Fentanyl at 2.5 mcg/kg will be used at induction of anaesthesia.

A double lumen endotracheal tube will be placed so lung isolation can be performed when necessary for the surgery. Anaesthesia will be maintained using a volatile agent or a target controlled infusion of propofol depending on the preference of the anaesthetist. The patient will be positioned laterally with the operative side up. All patients will receive simple intra-operative analgesia in the form of 1 gram of intravenous paracetamol and diclofenac unless the patient is over 70 or has abnormal renal function. Extra opioid analgesia will be given as intravenous morphine and this will be titrated by the anaesthetist. The amount given will be documented as part of the trial data.

Patients will be warmed to maintain a temperature between 36 and 37 degree Celsius using a warming blanket and warmed intravenous fluids. Anti-emetics in the form of ondansetron 4 mg and dexamethasone 4 mg will also be given unless there are any contraindications.

Prior to surgical incision patients in both groups will receive 1mg/kg 0.25% bupivicaine divided into 3 PV injections between the fifth and tenth thoracic vertebrae. Only trained anaesthetists with experience of over 30 PV insertions will perform the injections. The landmark technique for these injections is as follows: The spinous process of the thoracic vertebra is palpated by the anaesthetist, a 20 gauge needle is inserted 2.5 cm lateral to this and is advanced perpendicularly to the vertical and sagittal planes until the transverse process is contacted. The needle is then walked off the superior border of the transverse process, advanced a further 1 cm and one third of the weight determined local anaesthetic is delivered after careful aspiration.

Both groups will have a PV catheter placed at the start of the procedure and a bolus given straight away. As this is a double-blinded trial the anaesthetist will not know whether the bolus is local anaesthetic or saline solution.