Use of Sevoflurane Inhalation Sedation for Outpatient Third Molar Surgery: MATERIALS AND METHODS

In: Anesthesia

5 Mar 2010

After approval from the Ohio State University Human Subjects Review Committee, 24 patients (17 women and 7 men) were enrolled in the study. All patients were American Society of Anesthesiologists (ASA) Physical Status I or II and between 18 and 40 years of age. Patients who were currently using benzodiazepines, antidepressants, or long-term analgesics were excluded from the study. Likewise, patients with a recent history of renal disease or documented coronary artery disease were excluded from the study. Any patients that were ASA status III or higher, prisoners or wards of the state, minors, mentally retarded or developmental^ disabled, pregnant or actively trying to become pregnant, or nursing were also excluded. All patients presented to the Department of Oral and Maxillofacial Surgery outpatient clinic for evaluation of removal of at least 3 impacted third molars. A health history was obtained, a videotape explaining the proposed surgery was viewed by each subject, an examination and consultation was performed, and a written consent for surgery and sedation was obtained. Once the patients decided to proceed with surgery, they were advised of the possibility of enrolling in the present study. For those patients who decided to participate, a separate human review committee-approved consent form was also reviewed and signed. The patients were reappointed for surgery at a later date.

After ensuring that the patients had nothing to eat or drink for at least 8 hours prior to surgery, the patients were escorted to the surgical suite where noninvasive blood pressure cuff (Critikon Dinamap 1846SX), pulse oximeter (Nellcor N200), electrocardiograph (Hewlett-Packard 43100A), and a pretracheal stethoscope were placed. Intravenous (IV) access was obtained in an appropriate upper extremity vein with a 20-gauge catheter over needle, and a slow infusion of 0.9% normal saline was started. A drape was placed to prevent the surgeon from viewing the IV line and the infusion pump. Blood pressure was obtained and recorded every 5 minutes thereafter until the end of the procedure. Electrocardiogram and pulse oximetry were monitored continuously until the end of the procedure and recorded every 5 minutes. At this time, a memory card was shown for 10 seconds and a baseline Trieger test (Figure 2) was completed. Memory cards were illustrations of an animal with its name printed below the picture. A different animal card was shown at the different time intervals before, during, and after the surgical procedure, as described below. The memory cards were all shown in the same order to each patient. A nasal hood was placed through which 100% oxygen was delivered at a rate of 5 L/min.
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Figure 2. A Trieger test

Figure 2. A Trieger test.

Patients were randomly assigned to 1 of the 2 deep sedation groups. Three first-year trainees in the Department of Oral and Maxillofacial Surgery with significant experience in dento-alveolar surgery and IV conscious sedation performed the surgical procedures.

Group 1

Sevoflurane in oxygen at a flow rate of 5 L/min was administered via nasal hood at an increasing rate of 0.25% per minute. The sevoflurane concentration was titrated to the concentration allowing difficult sustained arousability—that is, the patient required continual verbal or physical stimulation to maintain partial wakefulness. Then, an infusion of 0.9% normal saline placebo was started via an infusion pump set at 75 |xgAg/min preprogrammed as if for a 10-mg/mL medication. The patient was administered sevoflurane for at least 10 minutes; then the memory card and the Trieger test were again administered. The surgeon then entered the surgical suite and injected 2% lidocaine with 1:100,000 epinephrine local anesthetic for infiltration or conduction block in standard fashion. After completion of the last injection, the surgeon waited 5 minutes before evaluating mandibular local anesthesia by noting a lack of patient response. Then a sharp explorer was placed in the mucosa between the cuspid and first premolar and advanced to the periosteum. Additional local anesthetic was administered as needed. The surgical procedure was begun with sevoflurane concentration adjusted to difficult sustained arousability as described above. When the last suture was placed or the surgeon indicated that surgery was completed, the sevoflurane vaporizer and the infusion pump were turned to zero and a memory card and Trieger test were administered immediately. When the patient regained an adequate level of consciousness, he or she was transferred to the recovery area. A memory card and Trieger test were administered every 10 minutes for 40 minutes from the time sevoflurane was discontinued. canadian pharmacy viagra

Group 2

The protocol was as above with the following changes. Instead of sevoflurane administration, only 100% oxygen at 5 L/min was delivered via nasal hood. Midazolam 50 |xgAg was titrated over 5 minutes. At that time, 1 jxgAg fentanyl was administered. Two minutes later, if the patient did not achieve difficult sustained arousability, approximately 0.15 mgAg boluses of propofol were administered every minute until the patient reached a state of difficult sustained arousability. Then a propofol infusion at 75 jxgAg/min was begun. One minute later, a memory card and Trieger test were given; next, local anesthesia was administered and tested by the surgeon, as in group 1. Propofol maintenance infusion was titrated to difficult sustained arousability as described above. If the propofol infusion had not yet been started because of adequate sedation with midazolam and fentanyl, it could be started at any time during the surgical procedure with the bolus and infusion technique as described above. When the last suture had been placed or the surgeon indicated that the procedure was completed, the propofol infusion was stopped and the same postoperative protocol as in group 1 was followed.

Within 10 minutes of the conclusion of surgery, the surgeon and dentist anesthesiologist rated the quality of the sedation by placing a slash mark on a visual analogue scale consisting of a 100-mm line labeled “Poor Sedation” at the left side and “Excellent Sedation” on the right side. Just before discharge, the patient indicated the quality of the sedation by a slash mark on the above scale. When the patient met standard discharge criteria, he or she was discharged to home with his or her escort. The patient took home a sealed envelope to be opened the day following surgery; this envelope contained copies of all the memory cards that had been shown during the procedure as well as other cards not shown (control cards). The patient was to indicate which cards he or she remembered. Additionally, a questionnaire  was answered. The patient returned the documents by mail in the provided preaddressed and stamped envelope.

The data were analyzed as follows. The independent t test was used to assess between sedation group differences in age, weight, surgery time, recovery time, number of memory cards identified correctly, maximum percentage positive and negative change in systolic and diastolic blood pressure, heart rate, and lowest mean oxygen saturation. Between sedation-group differences in quality of sedation (VAS scales) and Trieger test scores were analyzed nonparametrically using the Mann-Whit-ney-Wilcoxon test. Questionnaire results and sex comparisons were evaluated using the Fisher test. All tests were 2-tailed and results were considered significant at the P < .05 level.

The Trieger tests were scored by giving a rank of 0 for any dot connected by the pen line. If the line missed a particular dot, a numerical score was given based on the number of millimeters the line was away from the respective dot as measured by a perpendicular from the line intersecting the dot. For example, if the line were 3 mm from the dot with a ruler held perpendicular to the line, a score of 3 was recorded for that individual dot. All dots that were not connected were assigned a rank as above and the results added. Trieger test scores were then divided into 4 categories: (1) 0-10 (representing minimal impairment and scored as 0); (2) 11-25 (representing mild impairment and scored as 1); (3) 26-50 (representing moderate impairment and scored as 2); and (4) >50 (representing severe impairment and scored as 3). This was done to fairly score those subjects who were unable to connect any of the dots. Data are reported for these adjusted Trieger test scores. Differences from baseline scores were not calculated since this method applies more to conscious sedation testing where all patients could complete a Trieger test, even immediately following the sedation or surgery.

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