Phrenic nerve block for thoracic surgery

Blichfeldt-Eckhardt et al.'s randomised controlled trial of phrenic nerve blockade 1 provides a promising new approach to analgesia for a patient cohort in which pain can be troublesome 2. However, we would ask the authors to consider the effect of patient comorbidity on the potential for wider therapeutic application. Their study is limited to patients undergoing thoracic surgery for non-small cell lung cancer. Both thoracotomy and video-assisted thorascopic surgical approaches have been described for lung volume reduction surgery in patients with chronic obstructive pulmonary disease 3, and in the treatment of tuberculosis where medical management alone is insufficient 4. Unilateral phrenic nerve palsy is unlikely to be tolerated in both such patient groups, where the pathology is bilateral. Further, phrenic nerve palsy is likely to impede lung re-expansion following surgery requiring one lung ventilation, such as the thorascopic stage of minimally invasive oesophagectomy 5. This is unlikely to improve the high rates of pneumonia known to be associated with thoracic surgery 6. Finally, the authors acknowledge their placebo intervention was invasive. We would like to ask whether they considered avoiding catheter placement as a method for limiting its invasiveness, and if their approach presented problems in terms of gaining ethical approval?