Disclaimer: This article is intended solely for informational and educational purposes only. It does not constitute medical advice.
Inhaled induction of anesthesia is largely considered a pediatric technique that reduces distress associated with intravenous induction, while intravenous induction has dominated adult practice in part because of the pungency and airway irritability of older volatile anesthetics such as ether, chloroform, and halothane (van den Berg et al., 2005). However, there are clinical situations in which mask induction in adults is safe and suitable, particularly since the introduction of sevoflurane, a non-pungent, low-blood-solubility volatile agent.
When considering whether to utilize mask or intravenous induction in adults, it is important to consider patient preference. An audit of 240 ASA I–II patients presenting for ambulatory surgery found that although 85% of patients had prior experience with needle-based induction, only 33% actively chose intravenous induction when offered a genuine choice; half selected inhaled induction with sevoflurane, and the remainder deferred to the anesthesiologist’s judgment (van den Berg et al., 2005).
This finding challenges the long-held assumption that adults uniformly dislike anesthesia masks and suggests that needle aversion remains relevant beyond pediatric ages. The authors reported that sevoflurane induction was offered to 154 patients and completed successfully for all of them.
Another study gave 20 healthy, non-premedicated volunteers aged 19 to 32 years high inspired concentrations (6–7%) of sevoflurane by face mask using a three-breath vital capacity technique. Loss of the lid-lash reflex occurred within roughly one minute, a speed approaching that of intravenous induction, and acceptable conditions for laryngeal mask insertion were achieved in a mean of 1.7 minutes. No episodes of laryngospasm or increased secretions occurred, and coughing on induction was absent in all 60 anesthetics administered, although breath holding and expiratory stridor were relatively common, transient findings.
These results support sevoflurane mask induction as a reasonable technique in young, healthy adults, including for laryngeal mask airway placement, and indicate that acceptable tracheal intubating conditions can be achieved without neuromuscular blockade when adequate depth of anesthesia is allowed to develop. However, it is important to note that these results are limited by the small sample size and the physical condition criteria of participants—the bulk of patients undergoing a procedure with anesthesia do not fit within these constraints.
Patient age also affects the efficacy of mask induction in adults, with older adults responding less promptly. Lewis et al. (2006) examined 20 adults aged 26–65 years using a vital capacity sevoflurane/nitrous oxide technique and found a strong positive correlation between age and time to loss of eyelash reflex, as well as time to a bispectral index of 60 or below.
Times to these endpoints were predicted to be roughly fourfold and twofold longer, respectively, in a 60-year-old compared with a 30-year-old patient, likely reflecting age-related increases in functional residual capacity, reduced cardiac output, and greater tissue solubility of volatile agents. This prolongation has direct clinical implications: mask induction in older adults may require more time and be less predictable, potentially increasing the risk of airway complications and hemodynamic instability in the meantime.
Mask induction with sevoflurane is best indicated in healthy, cooperative adult patients without risk factors for pulmonary aspiration, including those with reflux disease, hiatus hernia, gastroparesis, or diabetic neuropathy (van den Berg et al., 2005). It is similarly appropriate to defer to intravenous access first in patients with an anticipated difficult airway, where early cannulation supersedes any expressed preference for an inhaled technique.
Younger patients, needle-averse patients, and those in whom intravenous access is anticipated to be difficult—such as some obese patients, in whom the venodilatory effect of volatile agents can facilitate later cannulation—may be reasonable candidates. Adequate staffing, which includes the presence of an assistant capable of managing the airway and securing venous access after loss of consciousness, is highly beneficial. Clinicians should anticipate a slower, more variable induction course in older adults and adjust monitoring and expectations accordingly.
References
van den Berg AA, Chitty DA, Jones RD, Sohel MS, Shahen A. Intravenous or inhaled induction of anesthesia in adults? An audit of preoperative patient preferences. Anesth Analg. 2005;100(5):1422–1424. https://doi.org/10.1213/01.ANE.0000150609.82532.C5
Lewis MC, Gerenstein RI, Chidiac G. Onset time for sevoflurane/nitrous oxide induction in adults is prolonged with increasing age. Anesth Analg. 2006;102(6):1699–1702. https://doi.org/10.1213/01.ane.0000205749.92049.91
Muzi M, Robinson BJ, Ebert TJ, O’Brien TJ. Induction of anesthesia and tracheal intubation with sevoflurane in adults. Anesthesiology. 1996;85(3):536–543. https://doi.org/10.1097/00000542-199609000-00012
