Use of Sevoflurane Inhalation Sedation for Outpatient Third Molar Surgery: DISCUSSION

In: Anesthesia

7 Mar 2010

Inhalation Sedation for Outpatient

This pilot study attempted to determine whether sevoflurane as a sole agent could be used as a deep sedative agent for minor surgical procedures in healthy young adults. Additionally, the quality of the sedation and the vital signs changes were compared with a common intravenous technique used by most dentist anesthesiologists and in many hospital and outpatient surgical facil­ities: the combination of midazolam and fentanyl followed by a propofol infusion.

It would appear that sevoflurane can be used as a deep sedative with high patient acceptance for minor oral surgical procedures. There was no significant difference noted between any parameter; however, 2 parameters approached statistical significance. First, the anesthesiologist did not rate the inhalation sevoflurane sedative as highly as the intravenous propofol sedative. This was because the inhalation sedative was more difficult to control in some patients than the intravenous technique, in part owing to the surgical model chosen. It was noted that during the initial stages of the sedation, patients had their mouths closed and nasal breathing produced a fairly rapid and reliable uptake of inhalation agent. After the initial period of titration, a mouth prop was used to hold the jaw open for the surgeon allowing for admixture of room air, especially in those patients who showed a preference for breathing through the mouth. At times during the procedure, in order to deepen the sedative, the dentist anesthesiologist would have to hold his hand over the patient’s mouth to prevent oral inspiration of room air and maintain inspired sevoflurane concentrations despite the use of an oro-pharyngeal gauze screen. If there was an interruption of the surgical procedure due to the need to adjust sedative levels, there was a greater time required to produce adequate sedation with the inhaled sevoflurane as opposed to the intravenous propofol.
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There may also have been a learning curve effect as the dentist anesthesiologist became more familiar with the clinical pharmacokinetics of the inhalation technique. If a full face mask was utilized, as opposed to a nasal hood, and if the surgical procedure was other than in the mouth, this disadvantage would likely be eliminated or significantly reduced. Admittedly, the dentist anesthesiologist was not blinded as to which drug group was selected for a given patient. Nevertheless, a similar criterion was used to determine if increased depth of sedation was needed; unacceptable patient movement would interfere with the procedure. Interestingly, surgeon satisfaction was not statistically different (P = 0.13) between the 2 groups. Importantly, no significant difference (P = 0.46) or trend was noted in patient satisfaction between the 2 groups, with a median VAS score of 92 for satisfaction with sevoflurane compared with a median VAS score of 96 for propofol.

The second parameter that approached significance was the adjusted Trieger test (P = 0.056) at the first recovery time. The median adjusted Trieger test scores at this 10-minute postoperative time were 0.0 for the sevoflurane group and 2.5 for the propofol group, with a high standard deviation. This first recovery period 10 minutes following the discontinuation of the sedative may, with increased patient number, show a faster recovery with sevoflurane. Although potentially biased by the dentist anesthesiologist’s knowledge of the sedative drug administered, his subjective opinion was that the sevoflurane patients were more mobile and required less assistance for going to the recovery room than the propofol group. In an outpatient setting, particularly a private office, a rapid return to an ambulatory state is very desirable.

Although sevoflurane has a low blood: gas solubility coefficient, thus allowing for rapid titration, this should not necessarily be equated to the rapid recovery seen with nitrous oxide. The fat:blood partition coefficient of sevoflurane is 48, comparable to that of isoflurane. This is in contrast to nitrous oxide, whose fat:blood partition coefficient is 2.3. Thus, sevoflurane, as opposed to nitrous oxide, has a much greater potential for being stored in fat during the anesthetic maintenance period, especially during long procedures. Fatty tissues can act as a reservoir for sevoflurane, which would then be slowly released during the recovery period. In a sedation lasting longer than 30 minutes, recovery times with sevoflurane may therefore be somewhat prolonged. The coadministration of 50% nitrous oxide with a reduced inspired sevoflurane concentration might reasonably be expected to enhance wake up and recovery because of nitrous oxide’s poor solubility in all tissues and low blood: gas partition coefficient.

Likewise, lengthy procedures using a propofol infusion would be expected to show increased recovery times. Once propofol had saturated the vessel-rich group and skeletal muscle, fat would act as a reservoir of drug, which would then be slowly released during the recovery phase for metabolism to inactive metabolites. Thus, the relative advantage of both sevoflurane and propofol in terms of rapid recovery from sedation may be less clear during longer surgical procedures.

It should be further noted that in actual clinical practice, the propofol infusion or sevoflurane concentration would likely be reduced or discontinued before completion of the surgical procedure to allow for an even earlier awakening and recovery than in this clinical trial. However, in order to more accurately compare recovery times between the 2 groups in this study, the drugs were not discontinued until the surgery was completed. Even with the constraints of this non-real-world scientific investigation, recovery in both groups was quite satisfactory. tadacip 20 mg

An important distinction between the 2 groups was the potential increased incidence of nausea in the sevoflurane group. One patient was withdrawn form the study because of nausea, and another patient experienced postoperative nausea. The patient who was withdrawn from the study was a particularly anxious woman with a high body mass index who later vomited after titrated administration of 10 mg of diazepam. Sevoflurane had not been administered above 0.5% and only for approximately 2 minutes. It seems likely that pre-sedation anxiety played a significant role in this patient’s reaction. The second patient, who completed the study, preferred not to have the sedative again but did indicate that there were no lingering effects of the deep sedation the next day. For those patients who report a history of nausea following a previous inhalation anesthetic, a propofol sedative may be advantageous, especially considering the potential antiemetic effects of this agent.

In regard to vital sign changes, both techniques provided a hemodynamically stable deep sedation. Interestingly, sevoflurane and propofol both produced similar positive and negative systolic and diastolic blood pressure changes. In this group of healthy young adults, this degree of blood pressure change was well tolerated. Caution would need to be exercised, however, in patients with coronary artery disease, peripheral vascular disease, or cerebrovascular disease, as these changes in absolute and mean pressures may have deleterious consequences. Heart rate changes were also comparable between the 2 groups.

Although respiratory parameters, such as tidal volume and end-tidal carbon dioxide concentrations, were not measured, oxygen saturation and pretracheal stethoscope auscultation of breath sounds revealed that all patients were spontaneously breathing and were able to maintain adequate oxygen saturations as long as manual airway support was provided. No patient experienced laryngospasm. In fact, on several occasions, when small amounts of secretions or irrigating fluid apparently approached the glottis, patients were noted to cough until suctioning of the pharynx was accomplished. Although this does not indicate with absolute certainty that protective airway reflexes were adequately intact, the presumption is that aspiration of foreign material would appear less likely than during nonintubated general anesthesia. Of course, because of the potential for propofol or any potent inhalation agent to produce unconsciousness and other consequences of general anesthesia, only those dentists with significant general anesthesia training should attempt any kind of sedation with sevoflurane or propofol, and then only with appropriate general anesthesia monitoring, as well as the immediate availability of emergency drugs and equipment consistent with modern general anesthesia guidelines.

This data was obtained with a healthy group of young adults, and it would not be prudent to extrapolate these findings to a group of ASA III or higher patients—or even ASA II patients with certain medical conditions.

Future studies should consider the use of nitrous oxide in addition to sevoflurane to reduce sevoflurane concentrations and perhaps improve recovery characteristics. Additionally, a longer surgical procedure may unmask an advantageous recovery profile for sevoflurane when compared with propofol. Finally, a surgical procedure allowing use of a full face mask would make this technique useful for a broader spectrum of patients. tadalis sx

CONCLUSION

The findings indicate that sevoflurane, when administered via nasal hood for oral surgery procedures in which local anesthesia is used, is well accepted by the patient and surgeon. The recovery from sedation is at least as good as that from a combination of a midazolam and fentanyl baseline sedation followed by a propofol infusion. Amnesia is equally profound for both techniques. Both techniques provided a hemodynamically acceptable deep sedation in the spontaneously breathing patient who was able to maintain adequate oxygenation provided manual airway support was provided. Side effects were minimal, except for the probable increased potential for nausea with inhaled sevoflurane.

The use of inhaled sevoflurane may provide another safe and pleasant technique when a deep sedative is needed for minor oral surgical procedures in healthy adults.


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