To the best of our knowledge this is the first study aimed to evaluate the effect of premedication with clonidine to prevent PONV in patients undergoing appendectomy. We showed that oral clonidine with the dose of 4 mg.kg-1 in children undergoing appendectomy can significantly decrease the incidence of PONV as compared with control group (70% vs. 16.7%). The incidence of post operative vomiting in control group of our study was 70% which is higher than the result of a similar study[5
]. The reason for this high incidence of PONV is not known to us.
PONV is a multifactorial complication of anesthesia and surgery which accounted for 13-42% of all post-operative complications in pediatric surgical patients[1
Many drugs (antihistamines, butyrophenones, dopamine receptor antagonists) have been attempted to prevent and treat PONV, but undesirable adverse effects, such as excessive sedation, hypotension, dry mouth, dysphoria, hallucinations and extrapyramidal signs have occasionally been noted[2
Clonidine is an α2-agonist which is used as a sedative premedication in children[1
]. Due to the lower costs of clonidine in comparison with other drugs such as opioid and benzodiazepines, as well as less complications of clonidine, it has been proposed as an effective drug for preoperative period. It has been shown that this drug can provide preoperative sedation, suppress cardiovascular responses to laryngoscopy and tracheal intubation and reduces anesthetic requirement. Moreover, clonidine has been reported to reduce shivering both after general and spinal anesthesia and the incidence of PONV has been shown to be reduced after both systemic and epidurally administered clonidine[10
]. However, there are conflicting results in the published literature about the effect of clonidine on the incidence of PONV. Some investigations in adults concluded that oral clonidine can reduce the incidence of PONV[12
], but in children the results are somewhat different. Our results are consistent with the two earlier studies who examined the effect of clonidine in children undergoing strabismus surgery and showed that preoperative oral clonidine at a dose of 4 µg.kg-1 is associated with a reduced incidence of postoperative vomiting in this group of patients [6
In contrast, some other investigators reported no significant antiemetic effect of clonidine given orally to children[16
]. The difference between the above mentioned results may be related to the nature and origin of vomiting during perioperative period.
In addition to age, sex, a history of PONV and motion sickness and also type of surgery which accounted as uncontrollable risk factors for PONV, there are anesthesia-related factors under control of anesthetists that have impact on the incidence and severity of PONV[1
]. It seems that the variety number of factors affecting the incidence of PONV in adults and children can be accounted for the different results of investigations evaluating the effect of clonidine on PONV. The mechanism of antiemetic effect of clonidine has not been yet clearly specified but some investigators believe that antiemetic effect of clonidine can result from its sedative and anxiolytic action which can directly reduce anesthetic and analgesic requirement of patients in perioperative period. It also has been suggested that clonidine can decrease PONV through its inhibitory action on sympathetic outflow and catecholamine release which can then block triggering of nausea and vomiting[18
One of the most important systemic side effects of clonidine is hypotension along with bradycardia in adults which have not been considered as main post-operative complications among children[17
]. However, none of the patients in our study experienced such episodes of severe hemodynamic change.
In our study all patients were comparable regarding demographic data, anesthetic technique, surgical procedure and postoperative medications, therefore the difference between the study groups with respect to incidence of PONV can be attributed to premedication with oral clonidine.
In this study we used oral clonidine with the dose of 4 µg.kg-1 which has been shown that it can reduce the incidence of PONV[6
]. Because of slow onset (0.5-l h) and a long duration (12 h) of action [8
], we administered oral clonidine to patients in intervention group one hour before transporting patients to the operating room.
Our study had a few limitations. In the present study the level of sedation and discharge time was not studied. Because of sedative effect of clonidine, further studies are required to elucidate if clonidine prolongs hospital stay in patients receiving clonidine in the perioperative period. However, to verify the antiemetic effect of clonidine in postoperative period, we need to design similar studies with larger sample size in appendectomy patients and also other pediatric surgical populations.