Aspiration Risk: Contributing Factors
Procedural sedation and analgesia performed during medical imaging or outside the operating room are associated with a number of factors that make them different from other settings. The most important factors are the preservation of airway reflexes and the lack of airway manipulation in most cases. These and other important contributing factors are highlighted below:
Airway reflexes are expected to be maintained during minimal and moderate sedation and lost during general anesthesia. In deep sedation, the reflexes might be impaired, but the cutoff point where the normal protective airway reflexes are lost is unclear. It is likely that a variety of factors specific to each individual patient determine the depth of sedation at which an individual is unable to protect him- or herself from significant aspiration. However, procedural sedation does not aim to provide sedation to the point of general anesthesia. Ketamine is used very frequently and, in general, reflexes are more likely to be preserved with this dissociative agent.
Inhalational anesthetics are known to be more emetogenic than the medications typically used for sedation practices.
The airway is not usually manipulated during procedural sedation except in procedures involving the airway itself such as drainage of peritonsillar abscess. Most cases of aspiration occur during induction, laryngoscopy, and extubation. However, intubation is neither needed nor expected for cases of procedural sedation.
A significant relationship has been noted to exist between aspiration and the patient's ASA status. One study examining the incidence of aspiration in adults undergoing elective procedures found that ASA class 1 and 2 patients have experienced only 1.1 and 1.3 episodes, respectively, per 10,000 procedures. The greater majority of patients receiving procedural sedation fall in the ASA 1 and 2 category.
Concern has been expressed that excessive NPO length can cause dehydration, hypoglycemia, and irritability leading to higher rates of failed sedation, a need for higher medication doses, and longer recovery times. A study of 324 patients receiving sedation with chloral hydrate prior to echocardiography found higher rates of sedation failure in children younger than 6 months who had fasted more than 2 hours when compared with those fasting less than 2 hours.
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Cite this: Krista Preisberga. A Child Needs Sedation: When Is It OK? - Medscape - Jan 25, 2013.