Nitrous oxide for pneumoperitoneum: no laughing matter this! A prospective single blind case controlled study

The search for the perfect insufflating gas has been elusive. Even though Carbon dioxide (CO(2)) is the most commonly used gas, it has numerous cardiovascular, respiratory and hemodynamic side effects, which have often been taken for granted. In the current scenario of ever expanding and complex indications for Laparoscopic Surgery these changes have an increasing implication of placing the patient at risk. Nitrous Oxide (N(2)O) has now made a comeback and shown by recent studies to be as safe as CO(2) for creating pneumoperitoneum (PP). The purpose of our study is to determine whether benefits of N(2)O (PP) outweigh those of CO(2) PP in Laparoscopic Surgery.

All patients undergoing Laparoscopic Surgery over an 8 week period were divided into two groups. Data were collected prospectively for Group I {N(2)O(n = 38)} and Group II {CO(2) PP(n = 39)}. Heart rate, Mean Arterial Blood Pressure, End-Tidal CO(2), Arterial pH, Peak Airway Pressure, Minute Ventilation and O(2) Saturation were recorded before PP, 15 minutes after PP and 10 minutes after exsufflation. Intraoperative anesthetic agent and postoperative pain medication use was recorded. Pain was assessed by means of visual analog scale (VAS) at postoperative hours 2 and 4 and on day 1. Results tabulated and analyzed statistically.

There was no statistical difference in age, sex, weight, complexity of surgery (type of procedure and duration of PP), Anesthetic risk, and duration of hospitalization between the two groups. Mean End-Tidal CO(2) increase was greater despite a greater mean intraoperative increase in Minute Ventilation in group II, Heart Rate, Arterial pH, Mean Arterial Pressure under anesthesia were significantly higher in group II. The quantum of intraoperative anesthetic agent and postoperative pain (as assessed by Visual Analog Scale) was less in group I.

This is an initial study assessing the use of N(2)O for insufflation; the results of our study suggest N(2)O PP has a definitive advantage over CO(2) PP. Further multicentric randomized trials are necessary before N(2)O becomes the standard insufflating agent.