Sir,We read with interest the article “Effect of intraoperative depth of anesthesia on postoperative pain and analgesic requirement: A randomized prospective observer blinded study” by Sahni et al.[1] The authors compared two groups of patients both anesthetized with standardized isoflurane and nitrous oxide anesthesia, in one group supplemental propofol boluses were administered in order to maintain bispectral index (BIS) between 40 and 45. As rescue analgesic requirement was lower in the group with the lower BIS, the authors concluded that maintaining BIS to a value of 45–40 throughout the surgery results in better postoperative pain relief.However, to draw their conclusions, the authors did not take into consideration the difference in the total amount of propofol administered, which was statistically larger in the group with the lower BIS. Cheng et al.[2] showed that general anesthesia with propofol is associated with less postoperative pain and morphine use than the general anesthesia with isoflurane. The lesser rescue analgesic requirement observed in the low BIS group could have been caused by the larger propofol dose as well. In order to be sure that the better postoperative pain relief was caused only because of a deeper anesthesia, authors should have used isoflurane to deepen anesthesia instead of propofol.