Hi,

 I recommend continuous infusion for paravertebral block for postsurgical acute pain management.

 Paravertebral block can affect only 12-18 hours with long-acting local anesthetics like ropivacaine or levobupivacaine. Postoperative pain management after thoracotomy, VATS, MICS, open nephrectomy, and even after radical mastectomy should be emphasized more than a day, 2-3 days in my opinion, in our daily practice.

 If you hesitate because of the risk of nerve/vascular injuries and pneumothorax, you can try retrolaminar block (or lamina technique of PVB). Although the effect of retrolaminar block is quite short after single injection, continuous infusion can work like PVB, especially with patient-controlled analgesia systems.

http://www.ncbi.nlm.nih.gov/pubmed/21752620

This article may help understanding the distribution of the injectate and the "unpredictable" effect.

http://www.ncbi.nlm.nih.gov/pubmed/15096240

Continuous paravertebral blocks are advised for analgesia. Consider it as a unilateral thoracic epidural. The catheter is inserted one segmental level below the midpoint of the  incision line.

Use the standard 10 cms epidural kit with 18 G Tuohy needle.

The loss of resistance can be a bit tricky here. You may not always get a loss of resistance when you enter the paravertebal space. 

Whether you insert a catheter depends on the surgery. For breast work single shot techniques work well. In our institute blocks last 12-18 hours with simple analgesia required after this period. PVB do have an unexplained analgesic effect after clearance of the LA. I agree with Takeshi about catheters for cavity surgery. A catheter is essential as pain can be fficult to control once a single shot wears off for these procedures. If you are covering a dermatome e.g thoracotomy an infusion is usually fine. You often need to run above 10ml/hr and 0.25% chirocaine or equivalent. If you are covering a range of dermatomes e.g open nephrectomy I have found  a catheter with regular boluses of 20ml 0.25% chirocaine or equivalent is more reliable than an infusion. If a PVB and infusion is reported as failed it is worth a bolus and waiting 15min as this often returns analgesia.

Yes parvertebral block is a good choice for chest surgeries. but when it comes to mastectomies for carcinoma breast we offer to thoracic epidural keeping in mind the probability of phantom breast.

Continuous infusion for paravertebral block is recommended for postsurgical acute pain management. Paravertebral block is as effective as epidural block for that porpuse. In addition, paravertebral block is more safe.

I Would like to thank you all for your excellent answers which are very helpful and informative. 

Sure paravert is a good choice for unilaterall thoraxic surgeries. But they cannot be used in infective procedure such as decortication . The infection can track down in epidural as well. For non infective yes a good choice.