Dexmedetomidine-ketamine combination and caudal block for superficial lower abdominal and genital surgery in children.

BACKGROUND: The use of dexmedetomidine-ketamine combination to perform different diagnostic and surgical pediatric procedures has increased. The optimal ketamine dose to combine with dexmedetomidine has not been determined. The goal of this study was to determine the ED50 and ED95 of ketamine, which in combination with, dexmedetomidine (1 µg · kg(-1)) provides an adequate anesthetic effect to perform a caudal block and then the ensuing superficial lower abdominal or genital surgery. MATERIAL AND METHODS: Twenty-five patients, aged 1-8 years, scheduled for superficial lower abdominal or genital surgery, were studied. All patients received an intravenous dose of dexmedetomidine 1 µg · kg(-1) and a random dose of ketamine from 1 mg · kg(-1) to 2 mg · kg(-1). After ketamine administration, a caudal block was performed and then surgery was initiated. Hemodynamics, respiratory variables, sedation level, and postoperative complications were recorded. The ED50 and ED95 of ketamine were calculated using logistic regression analysis. RESULTS: The ED50 and ED95 of ketamine to perform a caudal block were 1.53 (1.29-1.76) mg · kg(-1) and 2.25 (1.63-2.88) mg · kg(-1), respectively. The ED50 and ED95 of ketamine to perform a caudal block and to complete the entire procedure were 1.76 (1.57-1.95) mg · kg(-1), and 2.21 (1.77-2.64) mg · kg(-1), respectively. Three patients presented mild, self-limited, intraoperative bradycardia. CONCLUSIONS: These results suggest that adding ketamine 2 mg · kg(-1) to dexmedetomidine 1 µg · kg(-1) should produce an effective anesthetic level to perform a caudal block and the ensuing superficial lower abdominal or genital surgery in children.

Remifentanil requirements during propofol administration to block the somatic response to skin incision in children and adults.

BACKGROUND: During sevoflurane administration, children require a remifentanil infusion rate twofold higher than adults to block responses to skin incision. Similar data concerning remifentanil requirements are unavailable during total IV anesthesia. METHODS: We prospectively determined the infusion rate (IR) of remifentanil necessary to block the somatic response to skin incision in 50% (IR50) of adults (n = 20, aged 20-60 yr) and children (n = 20, aged 3-11 yr) during propofol anesthesia. In each patient undergoing lower abdominal surgery, a remifentanil infusion was initiated, followed by target-controlled infusion of propofol set at a plasma concentration of 6 mug/mL. After tracheal intubation, propofol was reduced to 3 microg/mL until the end of the study. Remifentanil IR was determined according to Dixon's up-and-down method, with the first patient in each group receiving 0.2 microg x kg(-1) x min(-1) followed by the consecutive patient receiving 0.02 microg x kg(-1) x min(-1) modifications according to the response of the previous patient. The remifentanil IR was kept unchanged for at least 20 min before surgery. At the beginning of surgery, only the skin incision was performed, and the somatic response was observed. If there was any gross movement of extremity the response was considered positive. RESULTS: The IR50 (CI(95%)) was 0.08 (0.06-0.12) microg x kg(-1) x min(-1) in adults and 0.15 (0.13-0.17) microg x kg(-1) x min(-1) in children (P < 0.001). CONCLUSION: These results demonstrate that, similar to sevoflurane anesthesia, during total IV anesthesia with propofol, children require a remifentanil IR almost twofold higher than adults to block the somatic response to skin incision.

[Controlled trial of dexamethasone compared with droperidol and ondansetron for the treatment of postoperative nausea and vomiting]. / Eficacia de la dexametasona en el tratamiento agudo de náuseas y vómitos posoperatorios: comparación con droperidol y ondansetrón.

BACKGROUND: Dexamethasone is useful as prophylaxis for postoperative nausea and vomiting (PONV). AIM: To study the short term efficacy of dexamethasone to treat PONV in adults without prophylaxis, and compare its efficacy with that of droperidol and ondansetron. MATERIAL AND METHODS: A prospective study was performed with 120 consecutive adult patients presenting PONV in the postanesthesia care unit (PACU) at a University teaching hospital. During the occurrence of PONV, patients were randomized to receive in a double blind manner dexamethasone 8 mg IV (Group 1, n=40), droperidol 1.25 mg IV (Group 2, n=40), or ondansetron 2 mg IV (Group 3, n=40). Risk factors for PONV were recorded. Evaluations were made until discharge from the PACU and included presence of PONV, degree of sedation, and other potential adverse effects of the study drugs. Short term efficacy was defined as the percentage of patients free of PONV during all the stay in PACU after treatment. RESULTS: General data was similar for the 3 groups. Mean +/- SD stay in PACU after treatment was 101+/-34 minutes in Group 1, 93+/-33 minutes in Group 2, and 99+/-32 minutes in Group 3 (NS). Short term efficacy (CI 95%) was 55% (40-70%) in Group 1, 90% (81-99%) in Group 2, and 63% (48-78%) in Group 3 (p <0.05 for group 2 vs 1 and 3). There were no adverse effects attributable to the study drugs. CONCLUSIONS: Short term efficacy of dexamethasone to treat PONV was similar to ondansetron, but inferior to droperidol. Further studies are needed to define the duration of this effect of dexamethasone.

Eficacia de la dexametasona en el tratamiento agudo de náuseas y vómitos posoperatorios: Comparación con droperidol y ondansetrón / Controlled trial of dexamethasone compared with droperidol and ondansetron for the treatment of postoperative nausea and vomiting

Background: Dexamethasone is useful as prophylaxis for postoperative nausea and vomiting (PONV). Aim: To study the short term efficacy of dexamethasone to treat PONV in adults without prophylaxis, and compare its efficacy with that of droperidol and ondansetron. Material and methods: A prospective study was performed with 120 consecutive adult patients presenting PONV in the postanesthesia care unit (PACU) at a University teaching hospital. During the occurrence of PONV, patients were randomized to receive in a double blind manner dexamethasone 8 mg IV (Group 1, n=40), droperidol 1.25 mg IV (Group 2, n=40), or ondansetron 2 mg IV (Group 3, n=40). Risk factors for PONV were recorded. Evaluations were made until discharge from the PACU and included presence of PONV, degree of sedation, and other potential adverse effects of the study drugs. Short term efficacy was defined as the percentage of patients free of PONV during all the stay in PACU after treatment. Results: General data was similar for the 3 groups. Mean ± SD stay in PACU after treatment was 101±34 minutes in Group 1, 93±33 minutes in Group 2, and 99±32 minutes in Group 3 (NS). Short term efficacy (CI 95%) was 55% (40-70%) in Group 1, 90% (81-99%) in Group 2, and 63% (48-78%) in Group 3 (p <0.05 for group 2 vs 1 and 3). There were no adverse effects attributable to the study drugs. Conclusions: Short term efficacy of dexamethasone to treat PONV was similar to ondansetron, but inferior to droperidol. Further studies are needed to define the duration of this effect of dexamethasone.

Estimation of the plasma effect site equilibration rate constant (ke0) of propofol in children using the time to peak effect: comparison with adults.

BACKGROUND: Targeting the effect site concentration may offer advantages over the traditional forms of administrating intravenous anesthetics. Because the lack of the plasma effect site equilibration rate constant (ke0) for propofol in children precludes the use of this technique in this population, the authors estimated the value of ke0 for propofol in children using the time to peak effect (tpeak) method and two pharmacokinetic models of propofol for children. METHODS: : The tpeak after a submaximal bolus dose of propofol was measured by means of the Alaris A-Line auditory evoked potential monitor (Danmeter A/S, Odense, Denmark) in 25 children (aged 3-11 yr) and 25 adults (aged 35-48 yr). Using tpeak and two previously validated sets of pharmacokinetic parameters for propofol in children, Kataria's and that used in the Paedfusor (Graseby Medical Ltd., Hertfordshire, United Kingdom), the ke0 was estimated according to a method recently published. RESULTS: The mean tpeak was 80 +/- 20 s in adults and 132 +/- 49 s in children (P < 0.001). The median ke0 in children was 0.41 min(-1) with the model of Kataria and 0.91 min(-1) with the Paedfusor model (P < 0.01). The corresponding t1/2 ke0 values, in minutes, were 1.7 and 0.8, respectively (P < 0.01). CONCLUSIONS: : Children have a significantly longer tpeak of propofol than adults. The values of ke0 of propofol calculated for children depend on the pharmacokinetic model used and also can only be used with the appropriate set of pharmacokinetic parameters to target effect site in this population.

Single-dose dexmedetomidine reduces agitation after sevoflurane anesthesia in children.

UNLABELLED: Emergence agitation is a common side effect of sevoflurane anesthesia in children. Dexmedetomidine, because of its sedative and analgesic properties, might be useful for the management of this adverse effect. We studied the effect of dexmedetomidine on recovery characteristics in 90 children aged 1 to 10 yr scheduled to undergo superficial lower abdominal and genital surgery. After inhaled induction with sevoflurane, patients were randomly assigned to receive saline (Group 1, n = 30), dexmedetomidine 0.15 micro g/kg (Group 2, n = 30), or dexmedetomidine 0.30 micro g/kg (Group 3, n = 30). After a laryngeal mask airway insertion a caudal block was performed in all patients. Maintenance of anesthesia was with 1% end-tidal sevoflurane and 50% nitrous oxide and spontaneous ventilation. Intraoperative hemodynamic and respiratory variables were recorded every 5 min. At the end of anesthesia time to eyes opening (TEO) and characteristics of emergence were recorded. General and intraoperative variables were similar in the 3 groups. The TEO was 7.5 +/- 5.0 min in Group 1, 8.2 +/- 5.0 min in Group 2, and 9.8 +/- 4.0 min in Group 3 (NS). The incidence (95% confidence interval) of agitation was 37% (20%-54%) in Group 1, 17% (4%-30%) in Group 2, and 10% (0%-21%) in Group 3 (P < 0.05). Paired comparisons showed a significant difference for Group 1 versus Group 3 (P < 0.05, 95% confidence interval of the difference: 7%-47%). The time to discharge from the postanesthesia care unit was similar for the 3 groups. We conclude that a dose of dexmedetomidine 0.3 micro g/kg administered after induction of anesthesia reduces the postsevoflurane agitation in children and with no adverse effects. IMPLICATIONS: In children undergoing surgery using sevoflurane anesthesia, dexmedetomidine 0.3 micro g/kg administered in 10 min after induction reduced the incidence of emergence agitation from 37% in the control group to 10%. No adverse effects attributable to dexmedetomidine were observed.