|Year : 2014 | Volume
| Issue : 3 | Page : 381-387
The effect of adding dexamethasone to bupivacaine on the duration of postoperative analgesia after caudal anesthesia in children
Department of Anesthesia and Surgical Intensive Care, Faculty of Medicine, Cairo University, Cairo, Egypt
|Date of Web Publication||27-Aug-2014|
Department of Anesthesia and Surgical Intensive Care, Faculty of Medicine, Cairo University, Cairo 12562
Source of Support: None, Conflict of Interest: None
Different additives have been reported to prolong the duration of caudal anesthesia in pediatrics. Although these drugs successfully increased the duration of the block, many of them were associated with undesirable adverse effects. Dexamethasone has been found to effectively increase the duration of an epidural block in adults, with no resulting side effects.
The aim of this study was to assess the effect of adding dexamethasone to bupivacaine on the duration of a caudal block in pediatric patients.
Patients and methods
This was a prospective randomized-controlled study that included 80 children, aged 1-6 years, American Society of Anesthesiologists physical status I, undergoing elective unilateral inguinal herniotomy. Patients were randomized to receive 1 ml/kg bupivacaine 0.25% (group B) or a mixture of dexamethasone 0.2 mg/kg added to 1 ml/kg bupivacaine 0.25% (group BD). In the postoperative period, pain was assessed using a modified Objective Pain Scale (mOPS) score until 24 h after surgery and rescue analgesia (oral paracetamol 15 mg/kg) was administered when mOPS score 4 or more was recorded. The primary outcome measure was the time to first analgesic requirement. The number of analgesic doses required in the first 24 h after surgery, residual motor block, sedation scores, intraoperative and postoperative hemodynamic variables, postoperative nausea and vomiting (PONV), and other adverse effects were recorded.
Group BD showed a significantly longer time to first analgesic requirement than group B. The number of oral paracetamol doses required in the first 24 h was significantly less in group BD. Group BD showed lower mOPS scores than group B. Modified Bromage scale scores, sedation scores, as well as intraoperative and postoperative hemodynamic variables were comparable in the two groups. Group BD showed significantly fewer incidences of PONV compared with group B.
Adding dexamethasone to bupivacaine prolongs the duration of postoperative analgesia and decreases the incidence of PONV after a caudal block in pediatric patients.
Keywords: bupivacaine, caudal anesthesia, dexamethasone, pediatric, postoperative analgesia
|How to cite this article:|
Girgis K. The effect of adding dexamethasone to bupivacaine on the duration of postoperative analgesia after caudal anesthesia in children. Ain-Shams J Anaesthesiol 2014;7:381-7
|How to cite this URL:|
Girgis K. The effect of adding dexamethasone to bupivacaine on the duration of postoperative analgesia after caudal anesthesia in children. Ain-Shams J Anaesthesiol [serial online] 2014 [cited 2017 Aug 24];7:381-7. Available from: http://www.asja.eg.net/text.asp?2014/7/3/381/139573
| Introduction|| |
Caudal anesthesia is the most commonly performed regional anesthesia technique in the pediatric age group . It is a safe and simple technique, with a high success rate, that can be used for any surgery below the level of the umbilicus [2,3]. The major drawback of a single-shot caudal block is its limited duration of action . Research has shown that more than 60% of children who receive a caudal block during groin surgery require additional analgesics in the postoperative period . Placing a catheter in the caudal space to perform a continuous caudal block has not gained popularity because it carries a risk of infection and causes delayed mobility .
Various additive drugs have been combined with the local anesthetic injected into the caudal space in an attempt to prolong the duration of the block. In a recent survey of pediatric anesthesiologists in the UK, 76.7%.of them reported using caudal additives . Opioids have been used successfully for this purpose, but they were shown to cause different undesirable side effects, the most serious of which is delayed respiratory depression [8,9]. Other nonopioid additives such as epinephrine , ketamine [10,11], midazolam [12,13], neostigmine [13,14], clonidine [15,16], and dexmedetomidine  have all been used during caudal anesthesia with varying degrees of success and with different resulting side effects. Continuing research is being carried out in an attempt to find relatively safer drugs associated with minimal side effects.
There have been several reports of the addition of dexamethasone to local anesthetics during peripheral nerve blocks (PNBs) in animal [17,18] as well as human studies [19-24]. Although the exact mechanism is unclear, adding dexamethasone consistently resulted in prolongation of the performed block, with fewer supplemental analgesic requirements. In addition to PNBs, there have also been reports on the use of dexamethasone during epidural blocks in adult patients [25-28]. Epidurally injected dexamethasone added to local anesthetics was found to prolong the duration of the epidural block [26,28] and to have an opioid-sparing and antiemetic effect in the postoperative period [25-27].
The aim of this study was to assess the effect of adding dexamethasone to bupivacaine during a caudal block in pediatric patients undergoing inguinal herniotomy. Our hypothesis was that adding dexamethasone would prolong the duration of a caudal block and decrease postoperative analgesic requirements.
| Patients and methods|| |
This study was carried out at the Cairo University Specialized Children's Hospital during the period from February 2013 till October 2013. After local ethics committee approval and written informed consents were obtained from parents or legal guardians, we included 80 patients undergoing elective unilateral inguinal herniotomy in this prospective randomized-controlled trial. All the children were 1-6 years old and American Society of Anesthesiologists (ASA) physical status I. Patients were excluded if they had a known or a suspected coagulopathy, hypersensitivity to any of the study drugs, abnormalities of the sacrum, mental retardation, pre-existing neurological disease, or any infection at the puncture site.
The patients included were randomized before induction of anesthesia using computer-generated randomization numbers into two equal groups: group B (n = 40), in which the caudal block was performed using only bupivacaine, and group BD (n = 40), in which the caudal block was performed using dexamethasone added to bupivacaine.
All patients were fasted according to the ASA guidelines (2 h for clear fluids; 4 h for breast milk; 6 h for formula milk or light meal). Patients were premedicated with midazolam 0.5 mg/kg orally 30 min before the induction of anesthesia. On arrival to the operating room, routine monitors were applied (ECG, noninvasive blood pressure, and pulse oximetry). General anesthesia was induced using sevoflurane 8% in 100% oxygen. After induction of anesthesia, an intravenous line was placed, followed by the insertion of an appropriately sized laryngeal mask airway when an adequate depth of anesthesia was reached. Anesthesia was maintained using isoflurane 1-2% in 100% oxygen. No muscle relaxants were administered and the patients were kept spontaneously breathing using an Ayre's T-piece till the end of surgery.
After properly securing the laryngeal mask airway, patients were turned to the left lateral position. Under complete aseptic conditions, a caudal block was performed using a 23-G short beveled needle. Correct placement of the needle was confirmed by the characteristic 'pop' felt as the sacrococcygeal membrane was penetrated, followed by a positive 'whoosh' test using 0.5 ml of air. In group B, patients received 1 ml/kg bupivacaine 0.25% (maximum volume = 20 ml). In group BD, patients received a mixture of 0.2 mg/kg dexamethasone in 1 ml/kg bupivacaine 0.25% (maximum volume = 20 ml). The total volume injected was 1 ml/kg in all patients. The anesthesiologist performing the block was blinded to the identity of the drug used.
Surgery was started 10-15 min after the block was performed. A standardized intraoperative fluid therapy was used in all patients (6 ml/kg/h of lactated Ringer's solution). Mean arterial blood pressure (MAP), heart rate (HR), and arterial oxygen saturation (SpO 2 ) were recorded before induction and then every 5 min after induction of anesthesia till the end of surgery. During the intraoperative period, adequacy of analgesia was assessed by hemodynamic stability, which was defined by the absence of an increase of more than 20% in HR or MAP compared with preincision values. An increase of more than 20% in HR or MAP was considered an indication of inadequate analgesia and managed by a bolus dose of intravenous fentanyl 1 mcg/kg, followed by further doses of fentanyl 0.5 mcg/kg if needed. The need for intraoperative analgesics was recorded.
After recovery and when they were able to maintain a patent airway, the patients were transferred to the postanesthesia care unit (PACU), where they remained for at least 2 h before being transferred to the ward. Hemodynamic variables (MAP and HR) were recorded on admission to PACU and then every 30 min till the patient was discharged to the ward. Postoperative pain was assessed using a modified Objective Pain Score (mOPS) every 30 min for the first 2 h and at 4, 6, 8, 10, 12, 18, and 24 h postoperatively. This score includes five criteria: crying, agitation, movement, posture, and localization of pain. Each criterion is assigned a score from 0 to 2, with 2 being the worst, to yield a possible total score of 0-10 . If the mOPS score was more (4), rescue analgesia in the form of paracetamol 15 mg/kg orally was administered. Further boluses of paracetamol 15 mg/kg were administered orally every 4 h if required.
Residual motor block and sedation level were also assessed at 30 min and at 1, 2, 4, and 6 h after surgery. Motor block was assessed using a modified Bromage scale consisting of four points [0 = full motor strength (flexion of knees and feet), 1 = flexion of knees, 2 = little movement of feet only, 3 = no movement of knees or feet] . The sedation score was assessed using a four-point scale (1, alert and aware; 2, asleep, arousable by verbal contact; 3, asleep, arousable by physical contact; and 4, asleep, not arousable) .
The occurrence of postoperative nausea and vomiting (PONV) during the first 24 h after surgery was recorded. If needed, PONV was treated by ondansetron 0.1 mg/kg intravenous. Any other complications including itching, urine retention (no voiding of urine for 6 h postoperative), respiratory depression (respiratory rate<10 breaths/min), hypotension (MAP decreased>20% of baseline), or bradycardia (HR decreased>20% of baseline) were recorded. All the postoperative data were recorded by an observer who was blinded to the drugs used during the caudal block.
The primary outcome measure was the time to first analgesic requirement, which was defined as the time from the caudal injection till the first rescue analgesia was administered (mOPS score4). Secondary outcome measures included the number of oral paracetamol doses required in the first 24 h postoperative, as well as the pain, motor block, and sedation scores recorded at the different time points. The incidence of PONV and other postoperative complications in the first 24 h after surgery were also recorded.
Given that the time to first analgesic requirement with bupivacaine caudal block was reported to be 7.6 ± 5.2 h , a total sample size of 80 patients allocated randomly to two equal groups (40 patients/group) had 90% power to detect an assumed clinically significant difference of 50% or more in the mean time to first analgesia between both the study groups (effect size d = 0.73, b error = 0.1, a error = 0.05, two-tailed). Statistical power calculations were carried out using the computer program G*Power 3 (Franz Faul, Universitδt Kiel, Germany) for Windows; an independent-samples t-test was used.
Collected data were presented as mean ± SD, numbers, and percentages as appropriate. Categorical variables were analyzed using the χ2 or Fisher's exact test as appropriate. Continuous variables were tested using an unpaired student's t-test. Ordinal and non-normally distributed variables were analyzed using the Mann-Whitney U-test. Statistical calculations were carried out using Microsoft Office Excel 2010 (Microsoft Corporation, NY, USA) and SPSS (version 20, 2011; SPSS Inc., Chicago, Illinois, USA). P value of less than 0.05 was considered statistically significant.
| Results|| |
Eighty children were enrolled in this study and divided into two groups of 40 patients each. The patient demographic data are presented in [Table 1]. The two groups were comparable in age, weight, sex distribution, and baseline HR and MAP. The duration of surgery and duration of anesthesia were also comparable in the two groups.
The caudal block was successful in all the patients included in the study. None of the patients in either group required intraoperative rescue analgesia. All patients remained vitally stable throughout the procedure and intraoperative hemodynamic parameters were comparable in the two groups.
The time to first analgesic requirement was significantly longer in group BD compared with group B (11.2 ± 3.5 vs. 7.1 ± 3.2 h, P<0.001). Group BD required significantly fewer doses of oral paracetamol than group B in the first 24 h after surgery (P<0.05) [Table 2]. The mOPS scores were lower in group BD than group B at all set time points, with the difference reaching statistical significance at 6, 8, 10, and 12 h [Figure 1].
|Figure 1: Modifi ed Objective Pain Scale (mOPS) score in the postoperative period. The mean mOPS scores were lower in group BD than in group B. The difference was statistically signifi cant at 6, 8, 10, and 12 h after|
surgery (†P<0.05, *P<0.01, **P<0.001). Data are presented as mean
(bar) and SD (error ba rs).
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Both groups showed comparable modified Bromage scale scores at all the set time points [Figure 2]. At 4 h after surgery, none of the patients in the two groups had residual motor block. The sedation scores were also comparable in the two groups at all set time points [Figure 3].
|Figure 2: Modifi ed Bromage scale in the postoperative period. The scores were not signifi cantly different between the two groups at all time points. Data are presented as mean (bar) and SD (error ba rs).|
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|Figure 3: Sedation score in the postoperative period. The scores were not significantly different between the two groups at all time points. Data are presented as mean (bar) and SD (error ba rs).|
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Hemodynamic variables recorded in the PACU were comparable in the two groups ([Figure 4] and [Figure 5]). Group BD showed a significantly lower incidence of PONV in the first 24 h after surgery than group B. Eight (20%) patients developed nausea in group B compared with only one (2.5%) patient in group BD (P<0.05). Six patients had vomiting in group B patients, whereas no vomiting was recorded in group BD (P<0.05). All the patients who developed PONV were treated effectively by a single intravenous dose of ondansetron 0.1 mg/kg. There were no incidences of hypotension, bradycardia, or respiratory depression in either group [Table 2].
|Figure 4: Mean arterial blood pressure (MAP) in the postoperative period. Values were not signifi cantly different between the two groups at all time points. Data are presented as mean ±SD.|
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|Figure 5: Heart rate (HR) in the postoperative period. Values were not significantly different between the two groups at all time points. Data are presented as mea n±SD.|
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|Table 1 Demographic data, baseline hemodynamics, duration of surgery, and anesthesia|
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| Discussion|| |
The present study showed that the addition of 0.2 mg/kg dexamethasone to 0.1 ml/kg bupivacaine 0.25% during a caudal block significantly prolonged the duration of the block, which resulted in decreased need for postoperative analgesics in the first 24 h after surgery. The addition of dexamethasone resulted in a decreased incidence of PONV and was not associated with increased sedation or prolonged motor block.
Dexamethasone, a corticosteroid with a powerful anti-inflammatory action, has been used successfully for prophylaxis against PONV . Its administration by either intravenous [32,33] or oral [34,35] routes has resulted in reduced pain scores and decreased analgesic requirements in the postoperative period, without causing side effects. However, the exact mechanism of the analgesic effect produced by dexamethasone is still not fully understood.
Acute nociception at peripheral tissues that occurs during surgery results in the sensitization of dorsal horn neurons in the spinal cord through the release of excitatory amino acids including aspartate and glutamate. These amino acids activate N-methyl-d-aspartate receptors, leading to an influx of calcium ions. The increase in intracellular calcium results in the activation of phospholipase A 2 , which converts membrane phospholipids into arachidonic acid. At the same time, there is upregulation of the expression of cyclo-oxygenase-2 in the spinal cord, causing prostaglandin E 2 synthesis resulting in a hyperalgesic state [36,37]. Corticosteroids are capable of inhibiting phospholipase A 2 and the expression of cyclo-oxygenase-2 during inflammation, therefore reducing prostaglandin synthesis, which in turn suppresses the hyperalgesia associated with acute noxious stimuli during surgery [37,38].
Previous research has shown that the addition of dexamethasone to local anesthetics injected during PNBs significantly prolonged the duration of these blocks. Adding dexamethasone to bupivacaine significantly prolonged the duration of intercostal blocks in animal  as well as human studies . When added to lidocaine, dexamethasone prolonged the duration of axillary brachial plexus blockade . The durations of interscalene [21,22] and supraclavicular brachial plexus blocks [23,24] were also prolonged by the addition of dexamethasone. In the pediatric age group, Ju et al.  found that adding dexamethasone to ropivacaine during peritonsillar infiltration led to reduced postoperative pain after tonsillectomy and adenoidectomy.
Several adult studies have reported the results of adding dexamethasone to local anesthetics during epidural blocks. Thomas and Beevi  reported that the preoperative epidural administration of dexamethasone, with or without bupivacaine, reduced postoperative pain and exerted an opioid-sparing effect after laparoscopic cholecystectomy. Khafagy et al.  found that an epidural bupivacaine-dexamethasone mixture had almost the same analgesic potency as bupivacaine-fentanyl, with the added advantage of decreased PONV. Jo et al.  found that the administration of dexamethasone epidurally, whether preoperatively or postoperatively, reduced pain and analgesic requirements after radical subtotal gastrectomy. Similarly, Naghipour et al.  showed that the addition of dexamethasone significantly prolonged the duration of epidural analgesia.
To the best of our knowledge, this is the first study to examine the use of dexamethasone as an additive to local anesthetics injected caudally in pediatric patients. In their study, Hong et al.  examined the effect of administering a single intravenous dose of 0.5 mg/kg dexamethasone in combination with a caudal block using 1.5 ml/kg of ropivacaine 0.15% in children undergoing orchidopexy. They found that the intravenous dose of dexamethasone resulted in prolonged postoperative anesthesia with decreased postoperative analgesic requirement, which is in agreement with the results of our study.
The duration of the caudal block reported by Hong and colleagues in the aforementioned study was 646 min, which is very similar to the duration we found in our dexamethasone group (11.2 h). However, the dose of dexamethasone that we chose to inject caudally (0.2 mg/kg) is less than the dose they injected intravenously (0.5 mg/kg). As described above, the analgesia mediated by dexamethasone is caused by its effect on intraspinal prostaglandin synthesis. We hypothesized that the direct injection of dexamethasone into the caudal epidural space will enhance its action at the spinal cord level. Therefore, we chose to use a smaller dose than the previously described intravenous dose. Further studies comparing equal doses of dexamethasone injected intravenously and caudally will help to determine whether the intravenous or the caudal route is more effective in providing postoperative analgesia.
We found that the incidence of postoperative vomiting was significantly less in the dexamethasone group. This is in agreement with several previous studies that showed that dexamethasone decreases the incidence of PONV [41-43]. The mechanism by which glucocorticoids decrease PONV is not fully understood, but this effect is most probably centrally mediated through the inhibition of prostaglandin synthesis or inhibition of endogenous opioids release . We found no relevant side effects with the use of dexamethasone as an additive during a caudal block. The addition of dexamethasone did not prolong the motor block or increase the sedation score compared with bupivacaine alone. Therefore, the patients' discharge readiness from the PACU and the hospital was not affected.
There are several limitations to our study. We used a single dexamethasone dose in all the patients. Additional studies comparing different doses of caudally administered dexamethasone are required to determine the optimal dose that produces the longest duration of postoperative analgesia with the least adverse effects. Another limitation was the difficulty in differentiating responses to pain from emergence agitation, especially in the preschool children. For this reason, we chose to use isoflurane for maintenance of anesthesia as opposed to sevoflurane to avoid the higher incidence of emergence agitation reported with sevoflurane maintenance anesthesia .
In conclusion, we found that the addition of dexamethasone, at a dose of 0.2 mg/kg, to bupivacaine significantly prolonged the duration of a caudal block in pediatric patients, leading to lower pain scores and decreased analgesic requirements in the postoperative period. Furthermore, addition of dexamethasone resulted in a decreased incidence of PONV and was not associated with any apparent side effects. Further studies are needed to determine the optimal dose of dexamethasone that is associated with the longest duration of analgesia and to compare the use of dexamethasone with other previously described caudal additives.
| Acknowledgements|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]