Single Versus Multiple Injection Ultrasound Guided Paravertebral Blocks

Paravertebral block (PVB) has been shown to provide excellent analgesia for major breast surgeries resulting in reduced narcotic consumption, reduced nausea, improved quality of recovery, reduced chronic pain and possibly reduced metastasis with breast cancer. Traditionally, PVB is done by multiple injections below T1-T5 transverse processes. With multiple injections, the risk is increased for a pleural, an intraneural, and/or an intravascular injection. Recently, ultrasonography is being used to facilitate PVB. The use of ultrasound imaging enables real-time needle visualization during the procedure. This may improve efficacy and reduce the chances of complication like pneumothorax. Currently, there are no data comparing ultrasound-guided single injection technique with multiple injections technique with regards to extent of spread for PVB. Our objective is to investigate the extent of dermatomal spread of PVB when equal volumes of local anesthetic are injected at one versus five paravertebral sites for patients undergoing major breast surgery. In addition, the investigators wish to compare the performance time and duration of analgesia.

Methodology: After local REB approval, 72 patients undergoing a unilateral mastectomy with or without axillary node dissection will be randomized to receive either single or multiple injections PVB. The PVB will be performed in prone position under real-time ultrasound guidance using a para-sagittal approach.The patients in single injection group will receive single injection PVB at T3-T4 level with 25 ml of 0.5% ropivacaine and four subcutaneous sham injections. Patients in the multiple injection group will receive five injections of PVB from T1 to T5 level. 5 ml of 0.5% ropivacaine will be injected at each level. Pleural drift will be used as a sign of correct needle tip location and local anaesthetic spread. The pinprick method will be used to assess the extent of dermatomal blockade, 20 minutes following the completion of procedure. All patients will receive a standardized general anesthesia for the surgery. Any adverse events including pneumothorax, epidural spread, LA toxicity/seizure, total spinal, will be recorded.