Dong Woo Han

Effects of fentanyl pretreatment on the QTc interval during propofol induction

Prolongation of the corrected QT (QTc) interval is associated with various anaesthetic drugs. The QTc prolongation may become more exacerbated during laryngoscopy and intubation, which is possibly caused by sympathetic stimulation. The aim of this study was to investigate the effects of fentanyl on the QTc interval during propofol induction in healthy patients. The patients were randomly allocated to receive either fentanyl (n = 25) or saline (n = 25) before induction. The QTc interval was significantly prolonged immediately after intubation in control group compared to preceding values, but it did not change in the fentanyl group. The number of patients with the prolonged QTc interval exceeding 20 ms immediately after intubation compared to the baseline values was 14 in the control group and seven in the fentanyl group. In conclusion, pretreatment with fentanyl 2 μg.kg−1 significantly attenuated QTc prolongation associated with laryngoscopy and tracheal intubation during propofol induction.

The effect of bolus administration of remifentanil on QTc interval during induction of sevoflurane anaesthesia.

Stimulation of the sympathetic nervous system associated with tracheal intubation causes corrected QT (QTc) interval prolongation. We postulated that the use of remifentanil during induction of anaesthesia might prevent this. Sixty unpremedicated, ASA grade 1 patients were selected and randomly allocated to receive either saline (group S), remifentanil 0.5 μg.kg−1 (group R 0.5) or remifentanil 1.0 μg.kg−1 (group R1.0) 1 min before laryngoscopy. The QTc interval was significantly prolonged immediately following intubation in group S and group R0.5, but it remained stable in group R1.0, compared with the QTc interval just before laryngoscopy. It is concluded that the administration of remifentanil 1.0 μg.kg−1 before intubation can prevent the prolongation of the QTc interval associated with tracheal intubation during induction of anaesthesia with sevoflurane.

Effects of target concentration infusion of propofol and tracheal intubation on QTc interval

This study was designed to evaluate the effect of target controlled infusion of propofol on QTc interval and tracheal intubation. Twenty‐five unpremedicated, ASA class I or II patients were selected and target concentration infusion of propofol at 5 μg.ml−1 was used throughout the study. The QTc interval was measured before anaesthetic induction (baseline, T1), 10 min after propofol infusion (T2), immediately after tracheal intubation (T3), and 1 min after tracheal intubation (T4). The QTc interval increased significantly at 10 min after the propofol infusion started compared to baseline (p = 0.003). After tracheal intubation, the QTc interval was further increased when compared to that at T2 (p < 0.0001). The increased QTc interval was within normal limit and no patient had an arrhythmia. In conclusion, although statistically significant, the increase in QTc interval was too small to be clinically significant during propofol infusion. However, the combination of propofol and tracheal intubation must be used carefully in patients with prolonged QTc interval.

Modeling the Effect of Sevoflurane on Corrected QT Prolongation A Pharmacodynamic Analysis

Background:Sevoflurane may prolong the corrected QT (QTc) interval in healthy humans when administered for induction and maintenance of anesthesia. Little information is available about the dose-response relationship of sevoflurane on the QTc interval. We performed a pharmacodynamic analysis of the relationship between end-tidal sevoflurane concentration (CET) and the QTc. Methods:Twenty-one patients aged 20–50 yr were enrolled in this study. Sevoflurane concentrations were progressively increased and then decreased over 15 min at the start of anesthesia; CET and automated QT interval were recorded continuously. Pharmacodynamic analysis using a sigmoid Emax model was performed to assess the concentration-effect relationship. Results:Maximal CET was 4.30 ± 0.33%. Measured baseline and maximally prolonged QTc interval values were 351.7 ± 15.4 ms and 397.8 ± 17.5 ms, respectively. During sevoflurane anesthesia, increased concentrations were correlated with prolonged QTc interval. Hysteresis between the CET and QTc interval were observed and accounted for in the model. Ce50 and ke0 were 2.5 ± 1.4 and 2.0 ± 1.0, respectively. The median prediction error, median absolute prediction error, and the coefficient of determination (R2) were 0.02%, 0.75%, and 0.95, respectively. The effect-site concentration (Ce50) and QTc interval data fit to a sigmoid Emax model. Conclusions:Among patients receiving sevoflurane for anesthesia, QTc interval changes correlate to anesthetic level. The Ce50 for significant QTc change is at clinically relevant levels of sevoflurane anesthesia.

Epidural ondansetron is more effective to prevent postoperative pruritus and nausea than intravenous ondansetron in elective cesarean delivery

Background. Postoperative pruritus, nausea, and vomiting are common side effects of intrathecal or epidural opioids. Intravenous ondansetron has been used for postoperative emesis. However, there are no reports regarding epidural ondansetron. Two studies were conducted to evaluate the prophylactic effects of epidural ondansetron for opioid‐induced pruritus, nausea, and vomiting. Methods. Neurotoxic signs were checked after epidural injection of ondansetron in rats. A clinical study was conducted to compare the prophylactic effects of epidural ondansetron with intravenous ondansetron for opioid‐induced pruritus, nausea, and vomiting in cesarean delivery. Results. No neurotoxic evidence was found in rats. The incidence of pruritus and nausea was significantly lower in the epidural ondansetron group than in the intravenous ondansetron group at 24 and 48 h postoperatively. Conclusions. Epidural ondansetron is more effective in preventing postoperative pruritus and nausea than intravenous ondansetron.

Does the Tibial and Sural Nerve Transection Model Represent Sympathetically Independent Pain

Neuropathic pain can be divided into sympathetically maintained pain (SMP) and sympathetically independent pain (SIP). Rats with tibial and sural nerve transection (TST) produce neuropathic pain behaviors, including spontaneous pain, tactile allodynia, and cold allodynia. The present study was undertaken to examine whether rats with TST would represent SMP- or SIP-dominant neuropathic pain by lumbar surgical sympathectomy. The TST model was generated by transecting the tibial and sural nerves, leaving the common peroneal nerve intact. Animals were divided into the sympathectomy group and the sham group. For the sympathectomy group, the sympathetic chain was removed bilaterally from L2 to L6 one week after nerve transection. The success of the sympathectomy was verified by measuring skin temperature on the hind paw and by infra red thermography. Tactile allodynia was assessed using von Frey filaments, and cold allodynia was assessed using acetone drops. A majority of the rats exhibited withdrawal behaviors in response to tactile and cold stimulations after nerve stimulation. Neither tactile allodynia nor cold allodynia improved after successful sympathectomy, and there were no differences in the threshold of tactile and cold allodynia between the sympathectomy and sham groups. Tactile allodynia and cold allodynia in the neuropathic pain model of TST are not dependent on the sympathetic nervous system, and this model can be used to investigate SIP syndromes.

Estimation of the length of the nares-vocal cord

The nasal route is preferred for fiberoptic intubation. Placing a lubricated endotracheal tube through the nostril can guide the fiberoptic scope towards the larynx. It would be helpful for optimal visualization of the vocal cord when the scope is passed through the endotracheal tube if the length of nares-vocal cord (NV length) could be predicted and the tip of the endotracheal tube could be placed close to the vocal cord. In this study we measured the NV length and examined the relationship between the NV length and various external measurements. Using a fiberoptic scope, the NV lengths were measured in 50 male and 45 female patients scheduled to undergo elective surgery under general anesthesia. In addition, the distances from the lateral border of the nares to tragus of the ear (NE distance) and to the angle of the mandible (NM distance) were measured. The age, height, and weight of all the patients were recorded. The NV length of the males was 18.3 ± 0.8 cm, and that of the females was 16.3 ± 0.7 cm. The relationship between the NV length and body height (P < 0.001, r = 0.755) and the NE distance (P < 0.001, r = 0.636) showed a significant correlation but NM distance did not (P = 0.075). The length of the NV cord can be predicted using the body height or the NE distance.

Effect of dexmedetomidine on the corrected QT and Tp-e intervals during spinal anesthesia.

Purpose The aim of this study is to evaluate the effect of dexmedetomidine on corrected QT (QTc) and Tp-e intervals in patients undergoing spinal anesthesia. Materials and Methods We studied 50 patients who were scheduled to undergo spinal anesthesia before orthopedic surgeries. Patients were allocated to receive either an infusion of dexmedetomidine or normal saline after spinal anesthesia. Results QTc intervals were significantly prolonged after spinal anesthesia, and the prolonged QTc interval returned to baseline values 10 minutes after either normal saline or dexmedetomidine administration in both groups. The QTc interval values after dexmedetomidine administration were significantly shorter compared to the QTc interval values just before dexmedetomidine administration. Conclusion Dexmedetomidine could promote the return of a prolonged QTc interval induced by spinal anesthesia and might be helpful in patients who have a prolonged QTc interval.

Comparison of the Efficacy of Dexmedetomidine plus Fentanyl Patient-controlled Analgesia with Fentanyl Patient-controlled Analgesia for Pain Control in Uterine Artery Embolization for Symptomatic Fibroid Tumors or Adenomyosis: A Prospective, Randomized Study

PURPOSE To investigate whether dexmedetomidine infusion could reduce opioid consumption and opioid-related side effects after uterine artery embolization (UAE). MATERIALS AND METHODS Fifty patients undergoing UAE for symptomatic leiomyomas or adenomyosis were randomized into two groups. In 25 patients, dexmedetomidine infusion was started at 0.2 μg/kg/h at 30 minutes before the procedure, followed by 0.4 μg/kg/h for 6 hours after the procedure. In another 25 patients (control group), volume-matched normal saline solution was administered. Both groups received fentanyl-based intravenous patient-controlled analgesia (PCA; fentanyl 10 μg/h with a bolus dose of 20 μg) during the 24 hours after the procedure. Nonspherical polyvinyl alcohol particles were used. Pain scores, fentanyl consumption, need for additional analgesics, and side effects were assessed for 24 hours after UAE. RESULTS Compared with the control group, patients in the dexmedetomidine group required 28% less PCA fentanyl during the 24 hours after UAE (P = .006). Numeric rating scale scores for pain (5.0±2.4 vs 7.0±2.2; P = .026) and the need for additional analgesics (two of 25 vs 17 of 25; P<.001) were lower in the dexmedetomidine group than in the control group during the first 1 hour after UAE. The incidence and severity of nausea and vomiting during the 24 hours after UAE were lower in the dexmedetomidine group than in the control group (P < .05). CONCLUSIONS The addition of dexmedetomidine infusion to fentanyl PCA provides better analgesia, fentanyl-sparing effect, and less nausea and vomiting, without significant hemodynamic instability.

Significance of the injection timing of ephedrine to reduce the onset time of rocuronium.

We postulated that the onset time of rocuronium can be accelerated effectively if it is administered at the time when the effect of ephedrine on cardiac output has reached its maximum. Seventy‐five male, anaesthetised, patients were randomly allocated to three groups. Ephedrine 70 μg.kg−1 was administered at 4 min (Early) or 30 s (Late) before administering rocuronium. The control group received saline at 4 min and at 30 s before rocuronium. The onset time of rocuronium in the Early group was significantly shorter than in the Control group, but there was no difference in the onset time between the Late and Control groups. There were no significant differences in the intubating conditions of the three groups. Ephedrine 70 μg.kg−1 can reduce the onset time of rocuronium effectively if rocuronium is administered at 4 min following the ephedrine injection, when the effect of ephedrine on cardiac output is expected to reach its maximum.