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The Effects of Glossopharyngeal Nerve Block on Postoperative Pain Relief After Tonsillectomy: The Importance of the Extent of Obtunded Gag Reflex as a Clinical Indicator

Park, Hee-Pyoung MD*; Hwang, Jung-won MD*; Park, Sang-Hyun MD*; Jeon, Young-Tae MD*; Bahk, Jae-Hyon MD†; Oh, Yong-Seok MD*

doi: 10.1213/01.ane.0000266440.62424.f1
Analgesia: Research Report

BACKGROUND: We evaluated the efficacy of glossopharyngeal nerve block (GNB) for the control of posttonsillectomy pain in adult patients, and correlated the extent of obtunded gag reflex as a clinical indicator of GNB with the extent of pain relief.

METHODS: Seventy-five patients undergoing tonsillectomy received bilateral GNB with 0.75% ropivacaine with epinephrine (Group R), 0.5% bupivacaine with epinephrine (Group B) at the end of the operation, or no intervention (Group C). To evaluate the effects of GNB, we assessed throat pain (100 mm visual analog scale) and severity of gag reflex response 0.5, 8, and 24 h after surgery.

RESULTS: In the immediate postoperative period, pain scores at rest and when swallowing in Groups R and B were significantly lower than those in Group C (21 ± 17 and 23 ± 13 vs 42 ± 16, 28 ± 22 and 32 ± 19 vs 62 ± 14, P < 0.001). The analgesic effect of GNB was strongly correlated with the extent of obtunded gag reflex (P < 0.01).

CONCLUSIONS: GNB is a useful method for the palliation of posttonsillectomy pain. An obtunded gag reflex response may be a clinical indicator for analgesia from GNB.

IMPLICATIONS: Glossopharyngeal nerve block (GNB) is a useful method for the palliation of posttonsillectomy pain. An obtunded gag reflex response may be a clinical indicator for analgesia from GNB.

From the *Department of Anesthesia and Pain Medicine, Seoul National University Bundang Hospital, Seongnam, Korea; and †Department of Anesthesia and Pain Medicine, Seoul National University Hospital, College of Medicine, Seoul National University, Seoul, Korea.

Accepted for publication March 12, 2007.

Reprints will not be available from the author.

Address correspondence to Jung-won Hwang, MD, Department of Anesthesia and Pain Medicine, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Korea 463-707. Address e-mail to

Postoperative pain is the principal cause of morbidity after tonsillectomy. This pain can affect the patient’s nutrition, ability to return to work or school, discharge from the hospital, and overall satisfaction with the procedure. Tonsillectomy produces severe pain on the first postoperative day (1). Several techniques have been described for the alleviation of this pain, including the use of opioids (2), steroids (3), and nonsteroidal antiinflammatory drugs (2,4), as well as local anesthetic sprays (5) and infiltration with local anesthetics around the tonsillar bed (6–10).

There is some controversy regarding the efficacy of glossopharyngeal nerve block (GNB) for the control of immediate posttonsillectomy pain. Some authors have reported that GNB or modified peritonsillar infiltration with local anesthetic are effective for pain associated with tonsillectomy (11–15). Other reports indicated that GNB with 0.5% bupivacaine or ropivacaine was ineffective for the reduction of early posttonsillectomy pain in adult and pediatric patients (16–19). However, no report provided a method to assess successful performance of GNB. We hypothesized that an obtunded gag reflex response is expected in patients receiving GNB, and that it might be a useful clinical indicator for evaluation of the extent of GNB.

Our prospective, randomized study was designed to assess the efficacy of GNB for the control of pain experienced by adult patients in the immediate postoperative period after tonsillectomy, and to determine whether the extent of obtunded gag reflex as a clinical indicator of GNB correlates with the extent of postoperative pain relief.

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After approval of the Institutional Ethics Committee and obtaining written informed consent from each patient, 75 ASA 1–2 physical status adult patients scheduled for tonsillectomy under general anesthesia were recruited into this study (Table 1). Exclusion criteria included diabetes, cardiac conduction anomalies, liver or kidney disease, hypersensitivity to local anesthetics, chronic pain, regular analgesic use within 1 wk of surgery, peritonsillar abscess or swallowing disorder.

During the preoperative visit, patients were instructed how to express pain on a 100-mm visual analog scale (VAS). All patients were empirically premedicated with 2.0–2.5 mg of midazolam in the reception room, and were noninvasively monitored during surgery. Anesthesia was induced with 2 mg/kg of propofol and 10 μg/kg of alfentanil. Rocuronium (0.6 mg/kg) was used to facilitate neuromuscular blockade. After tracheal intubation, anesthesia was maintained with 50% nitrous oxide and 2%–3% sevoflurane.

Tonsillectomies were conducted by the same two experienced surgeons, and there was no difference in surgical procedure or study group distribution between surgeons. Peritonsillar infiltration using 1% lidocaine with epinephrine (1.5–2.0 mL per tonsil) was performed by the surgeon before incision. Patients were randomly assigned to one of three groups using a sealed envelope method. At the end of surgery, bilateral GNB was done under direct vision using the McIvor gag with 0.75% ropivacaine with 1:200,000 epinephrine (Group R) or 0.5% bupivacaine with 1:200,000 epinephrine (Group B), respectively. Group C did not receive any intervention. All GNBs were performed as described previously (11,12,17) by one anesthesiologist who was not involved in postoperative evaluation of the patients. In brief, a 25G spinal needle was angled to 45° at 1 cm from the tip of the spinal needle. The needle tip pierced the retropharyngeal mucosa at the middle point of the posterior tonsillar pillar (palatopharyngeal fold). The needle was directed behind the posterior tonsillar pillar as laterally as possible and was inserted through the pharyngeal wall about 0.5–1.0 cm in depth. After careful aspiration, 3 mL of study solution was injected slowly. The injection was repeated on the opposite side. After confirming no bleeding at the puncture site, all patients recovered from anesthesia and were transported to the postanesthesia recovery room.

The status of each patient was evaluated by one assessor who was blinded as to group allocation. Thirty minutes after surgery, pain at rest and swallowing was assessed using the 100 mm VAS (0: no pain, 100: unbearable) in the recovery room. If pain scores were more than 60 mm at rest, 30 mg of ketorolac was administered IV.

Gag reflex response was evaluated by lightly touching the posterior wall of the lower part of the oropharynx with a tongue depressor. The gag reflex response was objectively assessed according to our artificial scale (None: no response, Mild: grimace but tolerable, Moderate: facial flushing, Severe: facial flushing with cough or lacrimation or restlessness). The extent of difficulty in swallowing was also assessed on a 4-point artificial scale (None: normal or no difficulty in swallowing, Mild: mild difficulty in swallowing, Moderate: moderate difficulty in swallowing, Severe: no swallowing or swallowing only with maximal effort). Our evaluation of the degree of swallowing difficulty depended exclusively on the patients’ answers. Most patients with severe swallowing difficulty were able to swallow with maximal effort. But, five patients (three in Group R and two in Group B) with GNB reported no swallowing ability despite their maximal effort. In these patients, VAS scores during swallowing were replaced with VAS scores at rest. Any problems related to GNB, such as upper airway obstruction and foreign body sensation in the throat were recorded.

On the ward, oral analgesic intake started 8 h after surgery and 600 mg of acetaminophen dissolved in water was administered every 8 h. If oral analgesia was not sufficient for pain control, 30 mg of ketorolac was administered IV as needed. The assessor reviewed all study patients on the ward 8 h after surgery, as well as on the following day, before discharge. Doses of parenteral analgesics administered until 8 h and 24 h after surgery were recorded, and VAS pain assessments were done 8 h and 24 h after surgery.

The sample size was determined to have a power of 90% at a 5% significance level to detect a difference of 25 mm in VAS scores during swallowing between Group C and the other groups. The comparison of pain at rest and on swallowing was conducted with a repeated measures ANOVA for time by treatment effect and was followed by ANOVA and Tukey test for comparison of VAS at each time point. ANOVA was used to determine the differences in demographic data. Other data were analyzed using χ2 test, when appropriate. Kruskal–Wallis test and Tukey test were used to determine a difference in the extent of gag reflex response among groups. Spearman’s coefficients were used to determine significant correlations. Values of P < 0.05 were considered statistically significant.

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The time-by-GNB treatment interaction for postoperative pain was significant (P = 0.002 pain at rest, P < 0.001 pain during swallowing) and Group C was different from Group B or Group R (P < 0.01 at rest, P = 0.001 during swallowing, Table 2). VAS pain scores at rest in Group C were significantly higher throughout the 24 h study period. There was no significant difference in the VAS of Group R compared to Group B at any time (Table 2). The number of ketorolac injections for additional pain control during the immediate postoperative period was significantly higher in Group C than in Group R or Group B (P < 0.001, Table 2).

Gag reflex obtundation was more intense in both the R and B groups than in group C (P < 0.01, Table 3). In both R and B groups, VAS scores during swallowing in the recovery room were strongly correlated with the extent of obtunded gag reflex (P < 0.01, Fig. 1).

There were no significant differences in postoperative nausea and vomiting, difficulty in swallowing, foreign body sensation in the posterior pharynx, dyspnea, nasal obstruction, or dry mouth among groups (Table 4).

An accidental intravascular injection of epinephrine-mixed ropivacaine occurred in one female patient in Group R. As soon as the ropivacaine was injected, the patient’s arterial blood pressure and heart rate increased abruptly. However, no significant sequelae were observed in this patient. No patient developed secondary posttonsillectomy bleeding. Blood-tinged saliva was observed in 15 patients (six patients in Group C, four in Group R, five in Group B).

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This study is differentiated from previous GNB studies by providing a relationship between the extent of diminished gag reflex and the degree of posttonsillectomy pain relief after GNB. To evaluate GNB’s effectiveness for postoperative pain control, GNB itself should be performed successfully. We believed that the more successful GNBs resulted in less posttonsillectomy pain, because the glossopharyngeal nerve supplies sensory fibers to the tonsil and peritonsillar area. But whether the glossopharyngeal nerve was completely blocked, partially blocked, or not blocked, in all previous studies (11–19) was not fully investigated (Table 5). Ineffectiveness of GNB for pain control could be expected if local anesthetics did not actually reach the glossopharyngeal nerve terminals corresponding to the tonsillar area. Because the response to gag reflex decreases after successful GNB, the degree of obtunded gag reflex was used as a clinical indicator to assess how successfully the glossopharyngeal nerve was blocked. Our results indeed demonstrated a strong relationship between the extent of the obtunded gag reflex and the extent of posttonsillectomy pain relief (Fig. 1). Not all patients received satisfactory GNB in this study. Twelve patients (six in each Group R and B) with severe gag reflex after GNB had unsatisfactory pain relief.

One of the advantages of better postoperative pain control with GNB is less use of parenteral or oral analgesics. There was a significant decrease in the use of ketorolac throughout the perioperative period. We experienced smoother emergence in the groups with GNB, however, this was not evaluated formally.

Complications related to local anesthetics in the course of tonsillectomy have not yet been systematically studied. A serious problem related to GNB is upper airway obstruction due to blockade of the vagus nerve proximal to the origin of the recurrent laryngeal nerves by an excessive volume of local anesthetic (17). In this study, mild dyspnea was observed in some patients undergoing GNB and the patients were managed conservatively.

This study had some limitations. First, we did not evaluate preoperative gag reflex for baseline data. Patients who have had no gag reflex after tonsillectomy might have no gag reflex even before surgery. It has been reported that the gag reflex is often absent in the normal population (20). Peritonsillar infiltration with epinephrine-mixed lidocaine was performed by surgeons to promote hemostasis during surgery. This may be a confounding factor in the interpretation of our results. Eeritonsillar infiltration could have affected the extent of gag reflex after tonsillectomy, especially in five patients in Group C who had no gag reflex or diminished gag reflex but had high VAS scores. Second, the degree of gag reflex was measured only in the immediate preoperative period. Third, patients in Group C did not receive any placebo, such as normal saline injection. Although one report showed that there was no difference in postoperative pain scores and analgesia consumption between GNB with saline and no injection (18), variations in injection technique may have affected our results. Finally, evaluation of the extent of swallowing difficulty was subjective and dependent on the patient’s effort and report. In clinical and practical settings, however, it is very difficult to objectively evaluate the extent of pharyngeal muscle paralysis.

In conclusion, this study demonstrated that effective GNB is a useful method for the palliation of postoperative pain after tonsillectomy in adult patients. The extent of an obtunded response to gag reflex correlated with the extent of postoperative pain relief. Therefore, an obtunded gag reflex response may be a clinical indicator for analgesia from GNB.

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