|Year : 2016 | Volume
| Issue : 4 | Page : 542-548
Ultrasound-guided caudal analgesia using fentanyl versus dexmedetomidine as an adjuvant for levobupivacaine in infraumbilical pediatric surgeries
Mai Mohsen Abdel Aziz, Amr Mohamed Abdelfatah, Hadil Magdy Abdel Hamid
Department of Anesthesia, Intensive Care & Pain Management, Ain Shams University, Cairo, Egypt
|Date of Submission||24-Apr-2016|
|Date of Acceptance||14-May-2016|
|Date of Web Publication||12-Jan-2017|
Hadil Magdy Abdel Hamid
Hadil Magdy Abdel Hamid, MD, 12345 Ain Shams
Source of Support: None, Conflict of Interest: None
Single-shot caudal analgesia is a useful technique in controlling postoperative pain in infraumbilical pediatric surgeries, although of a limited duration. The aim of this study was to evaluate the analgesic efficacy and rate of success when incorporating dexmedetomidine or fentanyl to levobupivacaine in ultrasound (U/S)-guided caudal block for infraumbilical surgeries.
Patients and methods
This prospective, randomized, double-blinded study was conducted on 63 pediatric patients undergoing infraumbilical surgeries, allocated into three groups to receive inhalational anesthesia with an appropriately sized laryngeal mask airway, followed by U/S-guided caudal epidural block using either only 0.25% levobupivacaine (L), or incorporating it with 1 μg/kg fentanyl (LF) or 1 μg/kg dexmedetomidine (LD) in a total volume of 0.7 ml/kg. Pain assessment using Children’s and Infants’ Postoperative Pain Scale (CHIPPS) score, time to first analgesic, and total analgesia required in the three groups and Ramsay sedation score were recorded. Hemodynamics and any adverse effects were also documented.
None of the patients required intraoperative additional analgesia. A statistically significantly lower postoperative CHIPPS values with prolonged analgesic duration and time to rescue analgesia was observed in the levobupivacaine–fentanyl and levobupivacaine–dexmedetomidine groups (275±20.62 and 304.75±25.2, respectively) as opposed to the levobupivacaine only group (203.1±18), with an evident reduction in the total paracetamol dose required postoperatively (P<0.001). Arousable sedation time was significantly prolonged in the levobupivacaine–fentanyl and levobupivacaine–dexmedetomidine groups. Apart from pruritus and urine retention in the levobupivacaine–fentanyl group, no adverse events were recorded in all groups.
Caudal levobupivacaine combined with dexmedetomidine 1 μg/kg in pediatric patients undergoing infraumbilical surgeries provides prolonged postoperative analgesia comparable to levobupivacaine–fentanyl and superior to levobupivacaine alone, with reduced postoperative analgesic requirements and extended arousable sedation time. The use of U/S raises the safety and ensures the success of caudal block.
Keywords: caudal, dexmedetomidine, levobupivacaine, ultrasound
|How to cite this article:|
Abdel Aziz MM, Abdelfatah AM, Abdel Hamid HM. Ultrasound-guided caudal analgesia using fentanyl versus dexmedetomidine as an adjuvant for levobupivacaine in infraumbilical pediatric surgeries. Ain-Shams J Anaesthesiol 2016;9:542-8
|How to cite this URL:|
Abdel Aziz MM, Abdelfatah AM, Abdel Hamid HM. Ultrasound-guided caudal analgesia using fentanyl versus dexmedetomidine as an adjuvant for levobupivacaine in infraumbilical pediatric surgeries. Ain-Shams J Anaesthesiol [serial online] 2016 [cited 2018 Apr 22];9:542-8. Available from: http://www.asja.eg.net/text.asp?2016/9/4/542/198267
| Introduction|| |
Caudal epidural block is a widespread technique for pediatric pain management in lower abdominal surgeries.
Caudal epidural block can be performed easily in pediatric population because the anatomical landmarks are superficial. However, in pediatric patients, the sacral hiatus is small and shallow, and hence careful needle advancement is necessary to avoid dural puncture or inadvertent intravascular injection. This is because, in younger ages as opposed to adults, the dural sac and epidural veins terminate at S3–S4 .
The success rate of caudal epidural analgesia using the blind technique in pediatric population is reported to be only 75% .
The use of ultrasound (U/S)-guided caudal block has been introduced as a tool for improving outcome, confirmation of correct needle placement within the sacral hiatus, increasing success rate, and minimizing the incidence of inadvertent injury to the dural sac or intravascular injection .
Although rare in infants and children, local anesthetic toxicity has been documented to cause neurological side effects, seizures, dysrhythmias, and cardiac complications. Racemic bupivacaine is the most commonly used local anesthetic drug for caudal analgesia in pediatric patients. Levobupivacaine, an enantiomer of the pure racemic bupivacaine S, is less toxic, provides the same analgesic effect as bupivacaine, and has a wider safety margin and better differential block (less motor block) . It is less likely to cause myocardial depression and fatal arrhythmias .
The duration of action of a single-shot local anesthetic drug is relatively short. Prolongation of action can be achieved with the use of various adjuvants, either narcotics such as morphine and fentanyl, α-2 blockers such as clonidine and dexmedetomidine, ketamine, or midazolam .
In our study, we aimed to evaluate the analgesic efficacy and success rate of U/S-guided caudal block using dexmedetomidine or fentanyl as adjuvants to caudal levobupivacaine in patients undergoing infraumbilical surgeries.
| Patients and methods|| |
This is a prospective randomized, blinded study, performed at Ain Shams University Hospitals during the period between January 2015 and December 2015. The study was conducted on 63 pediatric patients between the age of 1 and 5 years and ASA physical status of I–II scheduled for lower abdominal procedures (inguinal hernia, circumcision, or orchiopexy).
The approval of the local Ethics committee and written consent from parents were obtained. Exclusion criteria were as follows: parents’ refusal, contraindications to caudal block (infection at injection site, congenital diseases or sacral anomalies, or coagulopathy), known allergy to local anesthetics, history of developmental delay or mental retardation, diabetes mellitus, having heart block or liver impairment.
The patients were divided randomly into three groups:
Group L, which received levobupivacaine 0.25% (total volume 0.7 ml/kg).
Group FL, which received levobupivacaine 0.25% combined with fentanyl 1 μg/kg to a total volume of 0.7 ml/kg.
Group DL, which received levobupivacaine 0.25% combined with dexmedetomidine 1 μg/kg to a total volume of 0.7 ml/kg.
The patients were made to fast for appropriate fasting hours according to ASA guidelines for water (2 h), breast milk (4 h), and infantile formulas or meals (6 h).
Inside the operation room, general anesthesia was induced using inhalational induction with sevoflurane 8% in oxygen 100% under standard monitors (ECG, pulse oximetry, and noninvasive blood pressure MAP) and insertion of an intravenous cannula 22 or 24 G. An appropriate size laryngeal mask airway was secured in place. Anesthesia was maintained on sevoflurane 1–2% in 50% oxygen+50% air with spontaneous ventilation.
Patients were then randomized using the sealed envelope technique into three groups: L, FL, and DL.
The patients were then placed in the left lateral decubitus position with the hips flexed to 90°. Under complete aseptic conditions, the sacral hiatus and sacrococcygeal ligament were identified using a linear 6–13 MHz probe (M-Turbo C® ultrasound machine; Sonosite Inc., Bothel, Washington, USA). A transverse image was first viewed and then the transducer was rotated 90° to view the sacral hiatus and the caudal epidural space. Using an in-plane technique, a B-Braun (Bethlehem, PA) Stimuplex 22 Ga×35 mm insulated echogenic needle with 30° Bevel was advanced through at an angle of ∼45° passing through the sacrococcygeal ligament into the sacral canal in real time to a distance of 1 cm, confirming negative aspiration for blood, and cerebrospinal fluid the studied drug was injected. Syringes containing the studied medications were labeled numerically to blind the physician as regards the injected contents and were revealed at the end of the study.
After caudal injection, patients were placed in the supine position and heart rate and mean arterial blood pressure (MABP) were recorded immediately following caudal injection and then 10 min thereafter. Surgery was not allowed to proceed until 15 min had elapsed following caudal injection. Absence of a significant difference in hemodynamic readings, heart rate (HR), and MABP±20%, together with absence of gross physical movements (abdominal contraction, arm or leg flexion), following pin-prick stimulation of surgical site indicated adequate analgesia, and the surgery was allowed to proceed. Any additional intraoperative fentanyl for analgesia (based on hemodynamic changes from baseline) was recorded as regards the number of patients and the total fentanyl requirements.
At the end of the surgical procedure, inhalational anesthetic was discontinued. Emergence time (time from discontinuation of inhalational anesthetics to spontaneous eye opening) was recorded for all patients. Hemodynamic parameters were recorded together with pain assessment using Children’s and Infants’ Postoperative Pain Scale (CHIPPS) immediately following complete regaining of consciousness ([Table 1]) .
In the postanesthesia care unit, patient monitoring was resumed and pain was assessed using CHIPPS score. A score of 4 or above necessitated additional analgesia and a supplementary intravenous paracetamol dose of 15 mg/kg was administered. The time to required additional analgesia and the number of patients requiring analgesia and the total given dose were recorded. The patients were observed for side effects such as nausea, vomiting, pruritus, urinary retention, or respiratory depression; the latter was defined as a decline in SpO2 less than 95% on room air. Sedation was assessed using the Ramsay six-point sedation scale ([Table 2]) .
Statistical data analysis
In a one-way analysis of variance study, sample sizes of 21, 21, and 21 are obtained from the three groups whose means are to be compared. The total sample of 63 participants achieves 81% power to detect differences in the mean time for first rescue analgesia using an F-test with a 0.05000 significance level. The size of the variation in the means is represented by their standard deviation, which is 25.
Data were analyzed using SPSS 21.0 for Windows (SPSS Inc., Chicago, Illinois, USA). Analysis of variance was used to compare the three groups for quantitative parametric data with post-hoc Tukey’s test performed if there was a significant difference among the groups. A Kruskal–Wallis test was used for quantitative nonparametric data. The χ2-test was used for comparison of qualitative data. Continuous parametric data were presented as mean±SD, nonparametric data as median (interquartile range), and categorical data were presented as number of patients. P-values of less than 0.05 were considered significant.
| Results|| |
Demographic data among the three groups were comparable, with no statistically significant differences ([Table 3]). All administered U/S-guided caudal blocks were successful and all participants were included in the study.
[Figure 1] shows changes in heart rate recorded throughout surgery and up to 1 h in the postoperative period. There was a decrease in HR recorded in comparison with the baseline in all three groups, although not to the degree of bradycardia in any of the patients. A statistical significance was evident starting from 20 min after receiving the caudal block in the levobupivacaine–dexmedetomidine group compared with the other two groups and continued at 30th, 40th, and 50th minute intraoperatively (P<0.001).
|Figure 1: Heart rate changes throughout the studied period; lines are mean values and error bars are SD, and * represent significant differences between the groups.|
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As regards recording of MABP, there was a decrease in MABP in all three groups compared with baseline readings, although not to the extent of hypotension (decline <20% of baseline). This decrease started after induction of anesthesia, continued after administration of caudal analgesia, at 20th, 30th, 40th, and 50th minute intraoperatively. This was, however, of no statistical significance between the three groups. MABP began to rise toward baseline values for all patients following extubation; however, the levobupivacaine–dexmedetomidine and levobupivacaine–fentanyl groups maintained a slightly lower MABP compared with the levobupivacaine only group up to 1 h in the postoperative period ([Figure 2]).
|Figure 2: MABP changes throughout the studied period; lines are mean values and error bars are SD.|
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None of the patients included in the study required additional intraoperative intravenous fentanyl, which was evidenced by the absence of significant changes in hemodynamic parameters in response to surgical stimuli.
As regards recorded side effects, [Table 4] shows that there was no recorded hypotension, bradycardia, or respiratory depression in any patient in all three study groups.
Pruritus and urinary retention were significantly evident side effects in the levobupivacaine–fentanyl group. As regards vomiting, four patients in the levobupivacaine–fentanyl group experienced vomiting as opposed to only two patients in the levobupivacaine–dexmedetomidine group and only one patient in the levobupivacaine only group.
The mean duration of analgesia was prolonged and the time to rescue analgesia was significantly longer in the levobupivacaine–fentanyl and levobupivacaine–dexmedetomidine groups (275±20.62 and 304.75±25.2, respectively) as opposed to the levobupivacaine only group (203.1±18), with additional significant variation in total required dose of paracetamol postoperatively (P<0.001) ([Table 5]).
There was a statistically significant prolongation in the duration of arousable sedation, recorded using the Ramsay sedation score ([Figure 3]), in both the levobupivacaine–dexmedetomidine group (up to 5 h) and the levobupivacaine–fentanyl group (up to 4 h), in contrast to the levobupivacaine only group (up to 2 h).
|Figure 3: Ramsay sedation score. The middle solid black line represents the median, the upper and lower margins are interquartile range (IQR), whiskers are maximum and minimum values, and dots represent outliers.|
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[Figure 4] shows postoperative CHIPPS, which showed a statistically significant recording of prolonged analgesia (lower CHIPPS scoring <4) of up to 6 h of analgesia in the postoperative period in the levobupivacaine–dexmedetomidine group and up to 5 h in the levobupivacaine–fentanyl group as opposed to only 3 h in the group receiving only levobupivacaine (P<0.001).
|Figure 4: Children’s and Infants’ Postoperative Pain Scale (CHIPPS). The middle solid black line represents the median, the upper and lower margins are interquartile range (IQR), and * represent outliers.|
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| Discussion|| |
Caudal epidural anesthesia is one of the most commonly used regional techniques in pediatric age group. Its disadvantage is the relatively limited duration of action of caudally administered local anesthetics. This has prompted the use of caudal additive to prolong the duration of action and possibly provide a superior analgesic effect. These additives include narcotics such as morphine or fentanyl, ketamine, midazolam, and α-2 blockers such as clonidine and dexmedetomidine.
In our study, we evaluated the analgesic efficacy of U/S-guided caudal block using fentanyl versus dexmedetomidine as adjuvants to levobupivacaine in a prospective, randomized, double-blinded technique.
Isobaric levobupivacaine 0.25% has been introduced as an alternative to bupivacaine . Breschan et al., in 2005,  compared the analgesic effects of similar dose and concentration of bupivacaine, levobupivacaine, and ropivacaine and showed no difference in the quality of postoperative analgesia. Moreover, Breschan and colleagues reported that levobupivacaine has a significantly lower motor block degree compared with bupivacaine, especially during the first 2 h. This may be especially beneficial in outpatient or day-case surgeries . In our study, the full regaining of motor power was observed within the first 60–90 min in the postoperative period; however, scoring was not feasible, given the young age groups included in our study. The wider safety margin as regards less central nervous system toxicity and less likely myocardial depression or fatal arrhythmias together with better differential block provoked the use of levobupivacaine .
The use of U/S-guided injection protocol allowed for confirmation of correct needle placement within the sacral canal. U/S is effective for determining the depth of the epidural space and visualization of expansion of epidural space when injecting the local anesthetic. This has eliminated the inadvertent intravascular injection, interosseous injection due to incomplete vertebral ossification until the age of 6 years and accidental dural puncture as detrimental hazards of caudal block . This has also enhanced the success rate, which has been reported by Chen et al.  in 2004 to be 75% even in experienced hands using the blind anatomical technique. This has also been proved by Nikooseresht et al.  in 2014 using U/S for enabling identification of the location and morphology of the sacral hiatus and making it possible to adjust the optimal angle of needle advancement.
The high success rate in our study is evidenced by the almost nonexistent need for additional intraoperative intravenous fentanyl among the three study groups and nonsignificant hemodynamic changes on skin incision following the block performance.
The duration of action of caudal levobupivacaine can be prolonged using multiple adjuvants. Among narcotics, fentanyl has been most commonly studied as an appropriate narcotic adjuvant, being more lipophilic compared with morphine, and thus is associated with fewer side effects. Reported side effects with caudal narcotics include nausea, vomiting, pruritus, urinary retention, and respiratory depression . Epidurally administered fentanyl acts chiefly in the substantia gelatinosa on the dorsal horn of spinal cord. It acts by blocking the fibers transporting nociceptive impulse presynaptically and postsynaptically . Fentanyl as a caudal adjuvant has been used at doses of 0.5–2 μg/kg. Bhaskar Dutt and collagu, in 2014,  used fentanyl 2 μg/kg combined with 0.2% ropivacaine and recorded a prolongation in postoperative analgesia of up to 6 h. However, at this dose, they reported side effects in the form of respiratory depression (13.3% of fentanyl group) and vomiting (20% of group). Another study by El-Feky and Abd El Aziz , in 2014, used fentanyl at a dose of 1 μg/kg as a caudal adjuvant to bupivacaine. They showed comparable results to dexmedetomidine as regards hemodynamic parameters and quality of postoperative analgesia together with prolongation in total analgesia time.
In our study, we used fentanyl at a dose of 1 μg/kg combined with caudal levobupivacaine to achieve the desired prolongation of analgesia and minimize the incidence of side effects. This has been achieved without the need for additional intraoperative intravenous fentanyl and prolonged postoperative analgesia compared with levobupivacaine alone and minimized side effects in the form of pruritus and vomiting.
Dexmedetomidine is a selective α-2 adrenergic receptor agonist. It has eight-fold greater affinity for α-2 adrenergic receptors compared with clonidine. It has sympatholytic, analgesic, and sedative effects. It exhibits its action at the spinal cord by activating α-2-C and α-2-ARs in superficial dorsal horn neurons, thus directly decreasing pain transmission by decreasing the release of substance P and glutamate (pronociceptive transmitters) from primary afferent terminals. Dexmedetomidine also causes hyperpolarization of spinal interneurons through G-protein-mediated opening of potassium channels .
The sedative and supraspinal analgesic effects of dexmedetomidine are also mediated through hyperpolarization of noradrenergic neurons. This causes decrease in neuronal firing from the locus ceruleus and inhibition of norepinephrine release in the descending medullospinal noradrenergic pathway .
It prolongs analgesic duration in neuroaxial blocks with minimum controllable side effects as opposed to narcotic additives .
In a study by Anand et al.  in 2011, dexmedetomidine at a dose of 1.5–2 μg/kg was used as a caudal adjuvant without significant side effects. Anand also recorded prolongation in the duration of analgesia.
Bhaskar, in 2014, also used dexmedetomidine at a dose of 2 μg/kg added to caudal ropivacaine and reported prolongation in arousable sedation and less emergence agitation. Recorded side effects were bradycardia (a HR<80 bpm up to 1 year of age or <60 bpm above 1 year) and hypotension.
In our study, we used a lower dose of dexmedetomidine (1 μg/kg) and observed longer duration of postoperative analgesia compared with the levobupivacaine only group and longer time to rescue analgesia in a statistically significant finding. Moreover, patients receiving dexmedetomidine adjuvant showed a higher Ramsay sedation score, denoting longer arousable sedation compared with the other two groups. The analgesic effects of dexmedetomidine were comparable to fentanyl as evidenced by CHIPPS score and were superior to that in the levobupivacaine only group.
This is in agreement with the study by El-Feky and Abd El Aziz  (2014), who, in their study, used dexmedetomidine 1 μg/kg as an adjuvant to bupivacaine. In their study, they found a significant prolongation in time to rescue analgesia compared with the control and fentanyl groups in conjunction with comparable hemodynamic parameters and prolonged duration of arousable sedation and lower incidence of side effects.
This reinforces the analgesic, sedative, and hemodynamic stability of dexmedetomidine as a safe and effective adjuvant and an alternative to fentanyl.
| Conclusion|| |
Caudal levobupivacaine combined with dexmedetomidine 1 μg/kg in pediatric patients undergoing infraumbilical surgeries offers prolonged postoperative analgesia comparable to levobupivacaine–fentanyl and superior to levobupivacaine alone, with reduced postoperative analgesic requirements and extended arousable sedation time. The use of U/S for caudal analgesia raises the safety and ensures the success of caudal block.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]