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Do you feel the same way about inhalational anesthesia?
Release date:
2020-12-29 16:31
Source:
Ruivode
Inhalation anesthesia in animals refers to an anesthetic technique in which anesthetic agents are administered via the respiratory tract, suppressing the central nervous system and inducing temporary loss of consciousness without eliciting systemic pain. It is also the primary method of general anesthesia. The depth of anesthesia correlates with the distribution of the drug in brain tissue; as the agent is eliminated from or metabolized within the body, the animal gradually regains consciousness without any lasting sequelae.
Because inhaled anesthetics are poorly metabolized and degraded in the body, most of them are exhaled unchanged via the lungs. Consequently, inhalation anesthesia is easy to control, safe, and effective, making it one of the most commonly used methods in modern anesthesia; it is suitable for a wide range of laboratory animals, including rodents, dogs, monkeys, and others. During experiments, inhalation anesthesia is typically administered using specialized animal anesthesia equipment.
Injectable anesthetics are typically prepared fresh, with the choice of agent tailored to the specific requirements of the animal study. Prolonged storage can reduce or eliminate the drug’s efficacy. Moreover, during administration, variability in needle insertion site and depth can compromise accuracy; inadvertent injection into unintended tissues may result in suboptimal anesthesia, while intravascular or organ‑injection carries the risk of mortality. Some injectable anesthetics provide only analgesia without sedation, potentially eliciting rudimentary neural reflexes that interfere with intraoperative procedures.
Inhalational anesthesia typically employs anesthetics that are stable, non‑flammable, resistant to microbial growth, and readily volatile, such as isoflurane. When administered via an evaporator, the anesthetic concentration can be precisely adjusted without volatilizing or dispersing into the experimental environment, enabling controlled anesthesia with smooth and rapid recovery, and ensuring greater safety by minimizing metabolic toxicity and adverse effects in animals.
The effects of anesthetics on the body mainly include:
1) Effects on the respiratory system
It is irritating to the respiratory tract and exerts a certain degree of respiratory depression, inhibiting the ventilatory response to CO2. Under normal conditions, the ventilatory response to carbon dioxide is mediated by intercostal muscle activity; however, anesthesia reduces the contractile force of these muscles, thereby attenuating the ventilatory response.
Isoflurane has no effect on respiratory rate and primarily reduces tidal volume.
2) Effects on the circulatory system
It has minimal impact on cardiovascular function, maintains stable hemodynamic parameters, and exerts cardioprotective effects, particularly in myocardial ischemia-reperfusion models.
3) Effects on the liver and kidneys
Isoflurane: Most of it is eliminated via the lungs, with no adverse effects on the liver or kidneys. (The longer intravenous anesthetics are administered and the more frequently they are repeated, the greater the cumulative dose in the body and the more pronounced the suppressive effect on hepatic function.)
4) Neuroprotective effects
Most anesthetics exhibit neuroprotective effects, including barbiturates, propofol, and most volatile agents (such as halothane, isoflurane, sevoflurane, desflurane, and xenon). These agents can, to varying degrees, counteract apoptosis, degeneration, inflammation, and energy depletion induced by chronic neurodegenerative diseases, ischemia, stroke, or neurological trauma, thereby protecting brain tissue. However, this protective effect typically lasts no more than one week and is not sustained over the long term.
5) Effects on the Nervous System
Isoflurane affects the nervous system of young mice (<15 days old) but has no effect on adult mice (>15 days old). (In fact, ketamine, midazolam, and diazepam also induce neuronal apoptosis and other adverse effects in young mice.)
References
Wang Hongbin, Modern Veterinary Anesthesiology, 2009.
Zhou Kun, Laboratory Animal Science, 2008.
Sara Gargiulo, Journal of Institute for Laboratory Animal Research, 2012.
Paul Pagel, Journal of Cardiothoracic and Vascular Anesthesia, 2013.
Yang Juan, Jiao Shulan, Medical Information, 2015.
Kawaguchi M, Furuya H, Patel P M. ,Journal of anesthesia, 2005.
R. Daniel Mellon et al., Pediatric Anesthesia, 2007.