A reply

We thank Al-Shather et al. and Williamson for their comments on our case series 1. The paravertebral space contains the spinal nerve, its dorsal ramus, the rami communicantes and the sympathetic chain anteriorly 2. Local anesthesia covers the spinal nerve and the sympathetic chain 3. Thus, in the present case series, the sympathetic nerve supply was covered from T6 to T11. Moreover, multiple paravertebral injections provide better sensory block distribution than single injection, and paravertebral block inhibits somatosensory-evoked potentials at the injected levels and several adjacent levels 4-7. Hence, in our cases the surgical area was anesthetised and consequently there was no visceral pain. The use of nerve stimulator with paravertebral block allows determination of the anatomical site for injection of local anesthetic into the paravertebral space. This provides a more predictable distribution pattern of the block 8. The point of injection in the paravertebral space relates to the spread of the solution. Injections made in the anterior part and in close proximity to the nerve result in longitudinal multisegmental distribution 8. In the present series, the chances of intercostal spread were minimal. Spread into the epidural space is prevented by use of a nerve stimulator at 0.4-0.5 mA. No epidural injections have occurred in other cases we have reported previously 5, 8. Patients were fully awake and communicated with the physician during the surgery, without any events of tachypnea, agitation, or distress. Respiratory rate, oxygen saturation, CO2 concentration and blood gases did not change after multiple paravertebral injections or during the operation. Paravertebral block is associated with good preservation of postoperative pulmonary function 9. In our series, no pulmonary complications or atelectasis occurred postoperatively. Local anesthesia injected around the superficial cervical plexus does not reach the phrenic nerve, but anesthetises the accessory branch and part of the trapezius muscle. In this series, none of the cases were converted to general anesthesia and no intra- or postoperative complications occurred. However, when we first started to perform this technique for laparoscopic sleeve gastrectomy four years ago, several cases were converted to general anesthesia due to incomplete block and difficulty determining the point of injections in obese patients 10. We modified the technique accordingly, as presented in the case series reported. In reply to the comments raised by Dr. Williamson, four patients in the case series we reported were morbidly obese (BMI ≥ 40 kg.m−2) and one patient was super-morbidly obese (BMI ≥ 50 kg.m−2). Paravertebral block has been performed at our institution since 2000, as analgesia for laparoscopic cholecystectomy 11. As the sole method of anaesthesia, we have used unilateral paravertebral block for anesthesia in mastectomy 12 and bilateral block for ventral hernia repair 4, and have performed the block successfully for obese patients undergoing mastectomy 7, 10. Based on this experience, our institution is a referral centre for loco-regional anesthesia and patients such as those in the present series come to our institution requesting surgery under paravertebral block only.