In Response.

August 2017 • Volume 125 • Number 2 www.anesthesia-analgesia.org 711 Second, volunteers lack the actual sensation of pain and therefore lack the ischemic-like conditions including decrease in pH, oxygen tension, and an increase in lactate concentration, which correlate well with pain behaviors like guarding after incision in postoperative period. An increase in neutrophils in the wound tissue occurs shortly after surgery, peaks around 24 hours, and is associated with the release of proinflammatory mediators and endogenous opioids peptides. The proinflammatory mediators contribute to hypersensitization after incision. These mechanisms are not activated in volunteers.3 Third, earlier evidence of advantage of intermittent boluses over continuous infusion was provided by Hogan4 in cadavers using cryomicrotome imaging. They demonstrated a uniform spread of an ink in epidural space of cadavers after bolus dosing but nonuniform spread in rivulets for infusions. A larger volume and a higher infusion pressure produced a more uniform spread. This observation was supported in popliteal nerve block5 and femoral nerve block6 studies in which intermittent bolus technique was found to be superior to continuous infusion in surgical patients. Additional validation was provided in surgical patients receiving adductor canal block for postoperative pain relief by Thapa et al.7 Though the present study1 demonstrated the extent of spread, it did not comment upon uniformity of spread, an important factor in quality of analgesia in postoperative period. The role of continuous abdominal muscle movements during respiration in spread of drugs is also not known in TAP block. Fourth, clinically intercepting and breaking the pain cycle in the initial postoperative period is important and may reduce the incidence of hyperalgesia and persistent postoperative pain. This cannot be assessed in a volunteer study. In summary, we need to know whether bolus dosing or continuous basal infusion is best in immediate postoperative period where and when it is most important. The results of the study by Khatibi et al1 suggest a relook.