Nitrous oxide diffusion and the second gas effect on emergence from anesthesia.
Philip J Peyton1, Ian Chao, Laurence Weinberg
1Department of Anesthesia, Austin Hospital, Melbourne, Australia. phil.peyton@austin.org.au
Anesthesiology
|January 29, 2011
Summary
Eliminating nitrous oxide (N2O) during anesthesia speeds up the removal of sevoflurane, leading to faster patient emergence. This study shows N2O
Area of Science:
- Anesthesiology
- Respiratory Physiology
- Pharmacokinetics
Background:
- Nitrous oxide (N2O) elimination causes "diffusion hypoxia" by diluting alveolar oxygen.
- The impact of N2O elimination on concurrent volatile anesthetic agent concentrations and emergence speed is not well-understood.
Purpose of the Study:
- To evaluate the effect of nitrous oxide on the elimination of sevoflurane.
- To determine if nitrous oxide influences the speed of patient emergence from anesthesia.
Main Methods:
- Twenty surgical patients were randomized to sevoflurane with air-oxygen or with a 2:1 nitrous oxide-oxygen mixture.
- Arterial and tidal gas samples were analyzed for sevoflurane partial pressure at baseline, 2, 5, and 30 minutes post-surgery.
- Time to eye opening and extubation were recorded as measures of emergence speed.
Main Results:
- Arterial sevoflurane partial pressure was significantly higher in the control group at 5 minutes compared to the nitrous oxide group.
- Patients receiving nitrous oxide had faster times to eye opening and extubation.
- The difference in sevoflurane partial pressure was not significant at 30 minutes.
Conclusions:
- Eliminating nitrous oxide accelerates the reduction of accompanying volatile anesthetic agents.
- This acceleration contributes to the observed faster emergence from inhalational anesthesia when nitrous oxide is used.
More Related Videos
Related Concept Videos
Inhalational Anesthetics: Overview
Inhalation anesthetics are drugs that induce general anesthesia upon inhalation. They work by increasing the sensitivity of GABAA receptors or inhibiting NMDA receptors, leading to a decrease in central nervous system activity. The depth of anesthesia can be rapidly adjusted by changing the concentration of the inhaled gas. Some common examples of inhalational anesthetics include volatile liquids like isoflurane, desflurane, sevoflurane and gases like xenon and nitrous oxide. Isoflurane, a...
Physical Principles Governing Gas Exchange
Gas behavior plays a vital role in understanding bodily processes such as external and internal respiration. External respiration involves the diffusion of oxygen into the blood and carbon dioxide out of it in the lungs. In contrast, internal respiration happens in body tissues, where these gases move in opposite directions.
Gas Laws Governing Respiration
The behavior of gases is guided by Dalton's Law of partial pressures and Henry's Law.
Dalton's Law asserts that the total pressure exerted by...
Gas Laws Governing Respiration
The behavior of gases is guided by Dalton's Law of partial pressures and Henry's Law.
Dalton's Law asserts that the total pressure exerted by...
Behavior of Gas Molecules: Molecular Diffusion, Mean Free Path, and Effusion
Although gaseous molecules travel at tremendous speeds (hundreds of meters per second), they collide with other gaseous molecules and travel in many different directions before reaching the desired target. At room temperature, a gaseous molecule will experience billions of collisions per second. The mean free path is the average distance a molecule travels between collisions. The mean free path increases with decreasing pressure; in general, the mean free path for a gaseous molecule will be...
Stages of General Anesthesia
Various sedation levels offer significant advantages in facilitating procedural interventions for patients undergoing medical or invasive surgical procedures. These levels span from anxiolysis to general anesthesia, providing a spectrum of sedative effects to cater to specific patient needs. Anxiolysis reduces anxiety and is achieved through minimal sedation, enabling patients to remain awake and responsive while feeling more at ease during the procedure. This level can benefit minor...
Gas Exchange and Transport
Gas exchange, the intake of molecular oxygen (O2) from the environment and the outflow of carbon dioxide (CO2) into the environment, is necessary for cellular function. Gas exchange during respiration occurs largely via the movement of gas molecules along pressure gradients. Gas travels from areas of higher partial pressure to areas of lower partial pressure. In mammals, gas exchange occurs in the alveoli of the lungs, which are adjacent to capillaries and share a membrane with them.
Parenteral Anesthetics: Overview
Intravenous anesthetics are drugs administered parenterally to induce anesthesia or sedation. Propofol is a widely used agent formulated as a 1% emulsion in soybean oil, glycerol, and egg phosphatide. It induces rapid anesthesia primarily due to its rapid distribution from the bloodstream to target tissues and is metabolized in the liver. However, it can cause significant pain on injection and hypertriglyceridemia. Fospropofol, a water-based prodrug of propofol, lacks these adverse effects.


