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Kocaeli University School of Medicine, Department of Anesthesiology and Reanimation, Kocaeli, Turkey
Address correspondence and reprint requests to Dr. Yavuz Gürkan, Kalamis, Erguvan Sok. Kucukgul Apt. No. 17/6, Kadikoy, Istanbul, 81030, Turkey. Address e-mail to yavuzg{at}superonline.com
| Abstract |
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2 tests and Students t-test, as appropriate. The incidence of pruritus was significantly more frequent in the placebo group compared with the ondansetron group (68% versus 39%) (P = 0.001). Time to pruritus was similar in both groups (placebo group, 55 ± 32 min versus ondansetron group, 50 ± 31 min). Duration of pruritus was also similar in both groups (placebo group, 98 ± 60 min versus ondansetron group, 103 ± 58 min). Ondansetron prophylaxis significantly reduced the incidence of intrathecal fentanyl-induced pruritus in patients undergoing surgery under bupivacaine spinal anesthesia. IMPLICATIONS: Pruritus is a commonly reported side effect after intrathecal fentanyl administration during spinal anesthesia. This study was performed in a prospective, randomized, double-blinded, placebo-controlled manner to investigate the efficacy of prophylactic IV ondansetron in the prevention of pruritus after intrathecal fentanyl administration during spinal anesthesia. The incidence of pruritus was significantly more frequent in the placebo group compared with the ondansetron group (68% versus 39%) (P = 0.001).
| Introduction |
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Ondansetron, a selective serotonin Type 3 receptor antagonist, is often used for nausea and vomiting in patients undergoing chemotherapy or general anesthesia (5). Furthermore, there has been some clinical evidence for a significant antipruritic effect of ondansetron in patients with renal failure, cholestatic jaundice, and neuroaxial morphine (69). Because the side effects of intrathecal morphine are more pronounced than those of intrathecal fentanyl (4), the addition of fentanyl to local anesthetics during spinal anesthesia is preferred for most patients. It has been demonstrated that prophylactic IV ondansetron reduces the incidence of intrathecal morphine-induced pruritus in patients undergoing cesarean delivery (10), but a study evaluating the efficacy of prophylactic ondansetron treatment for intrathecal fentanyl-induced pruritus has not been reported. We therefore performed a prospective, randomized, double-blinded, placebo-controlled study to investigate the efficacy of pro-phylactic ondansetron in the prevention of pruritus after intrathecal fentanyl administration during spinal anesthesia.
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All patients received an intrathecal injection of 710 mg of hyperbaric bupivacaine 0.5% (the decision about the dose of hyperbaric bupivacaine was left to the attending anesthesiologist responsible for the case) and 25 µg of preservative-free fentanyl, both to increase the quality of anesthesia and to provide postoperative analgesia. Intrathecal bupivacaine and fen-tanyl were administered with separate syringes. Intrathecal fentanyl was given first, followed by an appropriate dose of intrathecal bupivacaine for surgery. Patients in the ondansetron group received ondansetron 8 mg IV, and patients in the placebo group received 2 mL of normal saline IV before the commencement of spinal anesthesia. The dose of 8 mg of ondansetron was chosen because previous studies have shown that this dose is effective both in the treatment and prevention of morphine-induced pruritus (10,11). The degree of pruritus was classified as 0 = no pruritus, 1 = mild pruritus, 2 = moderate pruritus, and 3 = severe pruritus. The patients were evaluated by an anesthesia research fellow who was blinded to the treatment group. Evaluations were performed every 15 min in the first hour after the injection of study drugs. Afterward, evaluations were performed at 1, 2, 3, 4, 5, and 6 h after the administration of study drugs. Patients were asked about the presence of pruritus. The site and the degree of pruritus and whether treatment was wanted was asked of those patients who had pruritus. If treatment was wanted, propofol 10 mg was injected IV. Postoperative pain was evaluated by using a visual analog scale (from 0 = no pain to 100 = worst pain imaginable). Patients were asked for the presence and the characteristics of headache, if present. The presence of cardiac arrhythmia was evaluated with patient complaint of palpitation. Twelve-lead electrocardiograms were performed for verification. None of the patients received intra- or postoperative sedation with propofol. Intraoperative sedation was provided with IV midazolam 0.030.05 mg/kg bolus doses.
A power analysis showed that 55 patients per group would provide 80% power to detect a 50% decrease in the incidence of pruritus from 60% in the placebo group to 30% in the ondansetron group. Statistical analysis was performed with
2 tests and Students t-test, as appropriate. Results are expressed as mean ± SD. For all determinations, a P value of <0.05 was considered significant.
| Results |
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1 in most patients (Table 2). Seven patients in the placebo group and three patients in the ondansetron group required treatment for severe itching. Five patients in the placebo group and two patients in the placebo group responded to a propofol 10 mg IV injection. Time to pruritus was similar in both groups (placebo group, 55 ± 32 min versus ondansetron group, 50 ± 31 min). Duration of pruritus was also similar in both groups (placebo group, 98 ± 60 min versus ondansetron group, 103 ± 58 min).
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None of the patients had abdominal cramps, cardiac arrhythmia, or extrapyramidal symptoms. Six patients in the ondansetron group had mild headache, whereas five patients in the placebo group had headache. Only one patient in the placebo group had postdural puncture headache.
| Discussion |
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The precise mechanism of pruritus after intrathecal opioids is not completely clear. Borgeat and Stirnemann (11) reported that ondansetron was effective for the treatment of spinal or epidural morphine-induced pruritus. Serotonin Type 3 receptors are abundant in the dorsal horn area of the spinal cord and in the spinal tract of the trigeminal nerve in the medulla (15,16). Fan (17) reported that morphine can activate serotonin Type 3 receptors by a mechanism independent of opioid receptors. Therefore, a direct stimulation of serotonin Type 3 receptors in the dorsal horn of the spinal cord and in the medulla by intrathecal injection of opioids may be a possible mechanism for the pruritus. These observations suggest that the serotonin Type 3 receptor is, to a certain degree, implicated in the development of the pruritus associated with the application of neuroaxial opioids.
Although ondansetron significantly decreased the incidence of fentanyl-induced pruritus, this complication still occurred in 39% of the patients. Yeh et al. (10) demonstrated that ondansetron treatment decreased the incidence of pruritus from 85% in patients undergoing cesarean delivery receiving placebo to 25% in patients receiving 0.15 mg of intrathecal morphine. Kyriakides et al. (18) showed that 4 mg of ondansetron decreased the incidence of nasal scratching from 70% in the placebo group to 43% in the ondansetron group after alfentanil 10 mg/kg IV. Further studies are necessary to determine whether ondansetron is more effective for pruritus after morphine application than fentanyl or alfentanil.
Because pruritus was mild and of relatively short duration in most patients, the routine prophylactic use of this drug may be associated with unnecessary drug administration in a large majority of the patients who might not develop pruritus or who would not have requested treatment. Although routine use of ondansetron would be associated with a somewhat higher cost of care, it should be questioned whether this might be balanced by increased patient satisfaction as a result of the decreased incidence of pruritus.
Although IV ondansetron significantly decreased the incidence of fentanyl-induced pruritus, this complication still occurred in 39% of patients. It is possible that other mechanisms, independent of serotonin receptors, might be involved in the pathogenesis of fentanyl-induced pruritus.
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