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Correspondence |
University of Tsukuba Institute of Clinical Medicine, Tsukuba, Japan, E-mail: yfujii{at}md.tsukuba.ac.jp
To the Editor:
Postoperative nausea and vomiting (PONV) are common and unpleasant complications following thyroidectomy.1 Propofol, in small doses, possesses direct antiemetic properties.2 We previously reported that a single small dose (0.5 mg·kg–1) of propofol administered intravenously at the end of surgery was more effective than traditional antiemetics, droperidol and metoclopramide, for preventing PONV in patients scheduled for thyroidectomy.3 In the present study, we determined the minimum effective dose of propofol for prophylaxis against PONV in this population.
Eighty patients (62 females), aged 20 to 68 yr scheduled for thyroidectomy under general anesthesia were enrolled. Anesthesia was induced with thiopentone 5 mg·kg–1 iv and fentanyl 2 µg·kg–1 iv, with tracheal intubation facilitated by vecuronium 0.2 mg·kg–1 iv. Anesthesia was maintained using sevoflurane 1.0 to 3.0% and N2O 66% in oxygen. At the end of surgery, patients received intravenously, in a randomized, double-blinded manner, placebo (Intralipid®) or propofol at three different doses (0.25, 0.5 and 0.75 mg·kg–1); (n = 20 each). Residual neuromuscular blockade was antagonized with atropine 0.02 mg·kg–1 iv and neostigmine 0.04 mg·kg–1 iv, and the trachea was extubated. Postoperatively, all episodes of nausea, retching and vomiting from 0 to 24 hr after anesthesia were recorded.3 Statistical analyses were performed using ANOVA, Chi-square test, and Fisher’s exact probability test. A P < 0.05 was considered significant. Values are presented as mean ± SD or number (%). The treatment groups were comparable with respect to demographic data. The rate of emetic symptoms from 0 to 24 hr after anesthesia was less in patients who had received propofol 0.5 mg·kg–1 (15%) or 0.75 mg·kg–1 (15%) than in those who had received placebo (60%); (P < 0.05). However, there was no difference between propofol 0.25 mg·kg–1 (55%) and placebo (Table available as Additional Material at www.cja-jca.org).
To our knowledge, this is the first report to determine the minimum effective dose of propofol for the prevention of PONV following thyroidectomy. Propofol 0.5 mg·kg–1 administered intravenously at the end of surgery is the minimum effective dose for prophylaxis against PONV. The precise mechanism by which propofol acts as an antiemetic remains unclear, but there is a possibility that propofol may have a weak serotonin antagonistic effect.4 Propofol at small doses, less than 1.0 mg·kg–1, lacks sedative, dysphoric, and extrapyramidal signs.5
References
1 Dejonckheere M, Deloof T, Dustin N, Ewalenko P. Alizapride in the prevention of post-thyroidectomy emetic sequelae. Eur J Anaesthesiol 1990; 7: 421–7.
2 Borgeat A, Winder-Smith OH, Saiah M, Rifat K. Subhypnotic doses of propofol possess direct antiemetic properties. Anesth Analg 1992; 74: 539–41.
3 Fujii Y, Tanaka H, Kobayashi N. Small doses of propofol, droperidol, and metoclopramide for the prevention of postoperative nausea and vomiting after thyroidectomy. Otolaryngol Head Neck Surg 2001; 124: 266–9.[Medline]
4 Hammas B, Hvarfner A, Thorn SE, Wattwil M. Effects of propofol on ipecacuanha-induced nausea and vomiting. Acta Anaesthesiol Scand 1998; 42: 447–51.[Medline]
5 Smith I, White PF, Nathanson M, Gouldson R. Propofol. An update on its clinical use. Anesthesiology 1994; 81: 1005–43.[Medline]
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