Nitrous oxide in waste anesthetic gases with different fresh gas flow: a case-based pilot observation and a practical thought on scavenging

Abstract

Use of nitrous oxide (N2O) as an anaesthetic gas has been on contradicting views for various reasons; operating room (OR) pollution and occupational exposure is one of those controversies. The present pilot experiment was planned to analyze the anaesthesia gas waste at the machine end of scavenging outlet and calculate the probable portion of N2O in the OR air, which is likely to help us in informed decision making. Anaesthesia gas waste was sampled at the machine end of scavenging outlet and was connected directly and analyzed using a gas analyzer attached to Mindray A7 anaesthesia workstation. An assembly of L connector, sampling line, corrugated tube and endotracheal tube were used to perform the procedure. The measurements were taken at 600, 1200 and 1800 mL/minutes of fresh gas flow (FGF). A total of 15 paired readings from five general anaesthesia cases were taken. The N2O percentage in the anaesthesia waste gases with a FGF of 600, 1200 and 1800 mL was 3.4 ± 0.54, 8.2 ± 0.83 and 14.0 ± 0.70, respectively. On calculation, the likely concentration of N2O in OR with FGF of 600 mL/min is 0.576 ppm, which will lead to the time weighted average 4.6 ppm exposure per day in modular OR. Reducing FGF to 600 mL/min reduces the N2O concentration in OR by 75% as compared to the FGF of 1800 mL/min. The time weighted average exposure to N2O is far below the permissible limit in modular OR.

Effect of nitrous oxide on clinical outcome in patients undergoing cerebellopontine tumor surgery under sevoflurane anesthesia: a randomized controlled trial

“… 2 Major concerns with its use include its short duration of action, ability to expand air-filled spaces, postoperative nausea and vomiting (PONV), 3 bone marrow depression, 4 demyelination, 5 neuronal degeneration, 6 and neurotoxicity, 7 subacute combined degeneration of the spinal cord, 8 postoperative myocardial ischemia 9 and health risks to operating room personnel. 10 It also increases cerebral blood flow and cerebral metabolic rate, impairs cerebral autoregulation, and may increase intracranial pressure (ICP), 11 thus making its use in neurosurgical procedures further questionable. On the other hand, it has an anesthetic sparing effect resulting in less cardiovascular and respiratory depression, less potential for drug interactions, predictable pharmacokinetics, rapid induction and recovery from anesthesia, and a combination of amnesic and analgesic properties.…”