Researchers at National Yang-Ming University (Taipei, Taiwan) conducted a randomized controlled study involving 158 women who underwent laparoscopic surgery for benign gynecologic lesions from August 1, 2009, through June 30, 2010. The women were randomly assigned to three groups: the PRM group (53 patients), the INSI group (54 patients), and the control group (51 patients). PRM consisted of five manual pulmonary inflations using a maximum pressure of 60 cm H2O, with the anesthesiologist holding the fifth positive pressure inflation for approximately 5 seconds. INSI involved bilaterally filling the upper part of the abdominal cavity with 500 cc of 0.9% normal saline. The main outcome measures were evaluation of pain, including abdominal pain and shoulder pain, as measured 12, 24, and 48 hours postoperatively.

The results showed that the frequency of postoperative shoulder pain at 24 and 48 hours was significantly decreased in the INSI group, compared with that of either the PRM or the control group. The researchers clarified that while both methods reduced the frequency of upper abdominal pain after laparoscopic surgery, INSI might be better for both upper abdominal and shoulder pain. The study was published in the December 2011 issue of Archives of Surgery.

Laparoscopic surgery offers smaller incisions, shorter hospitalizations, and less postoperative pain as compared with traditional laparotomies. However, there is marked variability of postoperative shoulder-tip pain following laparoscopic surgery, varying from 35%-80%, and ranging from mild to severe. In some cases, it has been reported to last more than 72 hours after surgery. The hypothesis of postoperative shoulder-tip pain is that CO2 induced phrenic nerve irritation causes referred pain to C4, and that therefore surgeons should try to reduce CO2 retention in the pelvic cavity.

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