Postoperative pneumoperitoneum
Postoperative residual pneumoperitoneum remains between a few hours and 24 days, despite the high solubility of carbon dioxide (93). Other sources of residual gas in the subdiaphragmatic region are thought to be water vapour produced by diathermy use and room air.
Residual pneumoperitoneum symptoms may mask complications such as bowel perforation, the presentation of which may be of relatively rapid onset or up to a week or more. While the presence of subdiaphragmatic gas in an erect abdominal radiograph is essentially redundant as a diagnostic tool to detect bowel perforation following laparoscopic surgery, the absence of gas may be helpful in excluding bowel perforation (93).Residual peritoneal gas is associated with postoperative shoulder tip pain that occurs following 35-60% of laparoscopic surgery. Shoulder tip pain is thought to be associated with peritoneal stretching and irritation of the diaphragm and phrenic nerve, secondary to carbon dioxide insufflation (94). There are conflicting data on drains following laparoscopy to remove residual gas and these are summarized in Table 47.4. The use of oral analgesia has been reported to be more cost-effective than peritoneal drainage in a number of studies (95, 96). Drain complications and the need for a longer hospital stay are the usual reasons for not using them, which is supported by evidence (Table 47.4). Other methods to minimize postoperative shoulder tip pain, such as instillation of normal saline (93, 97, 98), pulmonary recruitment manoeuvre (98, 99), gasless laparoscopy (100), low-pressure laparoscopy (101), or active gas evacuation with aspiration cannula (102), have also been described in the literature but come with issues and complications of their own and have not been assessed in rigorous randomized trials.