Discussion
The severity of CRBD and postoperative pain in patients treated with 1.5 mg/kg tramadol was significantly reduced compared with those given 1 mg/kg tramadol and normal saline. No difference in adverse effects among the three groups was found.
It is clinically common for patients to complain of CRBD when awakening from anesthesia postoperatively and CRBD is identified as a risk factor for postoperative emergence agitation.[18] Severe CRBD usually results in strong vocal response, with shaking of arms and legs; patients will even attempt to pull out the urinary catheter. CRBD can exacerbate postoperative pain and increase the workload of medical personnel. However, CRBD is frequently neglected and left untreated clinically. Management of CRBD is beneficial to improving patients' comfort and reducing postoperative emergence agitation and pain.
The major two independent predictors of CRBD are male gender and the diameter of the catheter.[2] Operation type is also regarded as one of the risk factors for CRBD, with urological and lower abdominal (such as obstetric and gynecological) surgeries having a higher incidence of CRBD.[2,19] To eliminate these interference factors, we only enrolled women who underwent elective gynecological operation with a 16F Foley urinary catheter inserted.
Bladder involuntary contraction is mediated by muscarinic receptors, which are stimulated by acetylcholine. The urinary bladder has different types of muscarinic receptors; the M3 receptor leads to direct contraction and the M2 receptor is associated with indirect contraction of the bladder.[20,21] The major mechanism of CRBD occurs through the M2 and M3 receptors. Tramadol is a centrally acting, synthetic opioid analgesic routinely used to manage postoperative pain. The effects of tramadol include inhibition of noradrenaline (NA), serotonin (5HT) reuptake, and M1 and M3 receptors.[22] Tramadol has been reported to be effictive in preventing the incidence and severity of CRBD.[13] It has also been used as a rescue therapy for moderate or severe CRBD at different dosages, such as 1.5 mg/kg or 50–100 mg.[11,23–25] The present study evaluated the dose-response effect of tramadol for the management of CRBD. The onset time of tramadol is within 10 min, and the peak effect time is approximately 30 min. Therefore, we observed patients at 0.5 h after the medicine was administered. However, we did not find out any difference among the three groups at o.5 h.
Although adverse effects of nausea and vomiting for tramadol are very common,[13,26] dose–response adverse effects were not observed in this study, and there was no significant difference in the incidence of adverse effects among the three groups. Because the medication was administered from Murphy's dropper with a slow drip, and the drug concentration was diluted. This study also investigated the dose–response effect of tramadol on postoperative pain relief. The VAS was reduced in group C compared with that in groups A and B at all time intervals; thus 1.5 mg/kg tramadol was more effective than 1 mg/kg tramadol at relieving postoperative pain relief.
There are some limitations in this study. First, we did not evaluate the efficacy of tramadol for all types of surgeries and different surgeries might have different degrees of interference. Moreover, we only observed up to 6 h after the medicine was administred. Although there was no difference in the severity of CRBD among the three groups at 6 h, the half-life of tramadol is 6 h; thus a longer observation time may be necessary. In addition, all the patients enrolled in this study were women, and male gender might have some associated interference.
BMC Anesthesiol. 2018;18(194) © 2018 BioMed Central, Ltd.
