Comparison of Analgesic Efficacy of Caudal Dexamethasone with Intravenous Dexamethasone as an Adjuvant to Caudal Block in Pediatric Patients Undergoing Urogenital Surgeries.

CONTEXT: Caudal block is one of the most common regional anesthetic techniques employed in pediatric urogenital surgeries. Adjuvants play an important role to improve postoperative analgesia. AIMS: The aim of this study was to evaluate the analgesic effect of dexamethasone when given systemically as against caudally as an adjuvant to caudal block. SUBJECTS AND METHODS: In this randomized controlled study, sixty American Society of Anesthesiologists Physical Status I and II patients aged 3-6 years were randomly allocated into two groups of thirty each. Group D received caudal block with local anesthetic solution and 0.1 mg/kg injection dexamethasone. Group I received a caudal block with local anesthetic solution. They received intravenous injection dexamethasone 0.1 mg/kg after the block. Both the groups were compared for the duration of postoperative analgesia and analgesic requirement. STATISTICAL ANALYSIS USED: Statistical analysis was done with unpaired t-test and Chi-square test as was appropriate.
RESULTS: Group D showed a significant prolongation of postoperative analgesia (626.33 ± 59.39 min) as compared to Group I (194.67 ± 27.76 min). Similarly, requirement of analgesic was reduced on 1st postoperative day in group receiving caudal dexamethasone.
CONCLUSIONS: Dexamethasone significantly prolongs the duration of postoperative analgesia of a caudal block when given caudally than when given intravenously.

INTRODUCTION

Caudal block is one of the most common regional anesthetic techniques employed in pediatric urogenital surgeries. Various adjuvants such as opioids and α2 agonists are used for better postoperative analgesia with caudal block. They have certain disadvantages such as urinary retention, nausea, vomiting, pruritus, and respiratory depression by opioids.[12] Similarly, α2 agonist can cause bradycardia, hypotension, and sedation.[123] Dexamethasone, when used as an adjuvant in small doses, is safer and not associated with such complications. Many studies show that addition of dexamethasone in epidural and caudal blocks prolongs the duration of action of the block.[456] It exerts some analgesic activity by its anti-inflammatory action when given intravenously as well. It inhibits synthesis of cycloxygenase-2 in peripheral tissues and central nervous system, thus reducing the prostaglandin production responsible for inflammation and pain.[7] We conducted this study to determine the analgesic effect of dexamethasone as an adjuvant to caudal block when given systemically and caudally.

SUBJECTS AND METHODS

This was a prospective double-blinded randomized controlled trial.

After approval from the Institutional Ethics Committee, sixty American Society of Anesthesiologists Physical Status I and II patients, aged 3–6 years, and weighing 8–20 kg were enrolled for the study. They were posted for urogenital surgeries such as herniotomy for congenital hernia or hydrocoele, orchidopexy, orchidectomy, cystolithotomy, etc.

Children having any contraindication for caudal blocks such as known allergy to local anesthetic agents, coagulation disorders, preexisting neurological disorders, any systemic or local infection, and anatomical abnormalities of spine were excluded from the study. Similarly, children having any other comorbidity such as cardiovascular or respiratory problems, history of convulsions, psychiatric disorders, and mental retardation were excluded from the study. A written, valid, and informed consent was obtained from their caregivers/parents.

A thorough preoperative assessment was done including a detailed history, thorough general and physical examination, and review of investigations. The patients were randomized into two groups of thirty each using sealed envelopes method, as Group C (who would receive caudal dexamethasone) and Group I (who would receive intravenous [IV] dexamethasone after a caudal block. All patients were kept fasting for 2 h for clear fluids and 6 h for other foods preoperatively. A proper sized intracath was taken and fixed by a splint in all patients.

In the preoperative room, the patients were given premedication with injection ketamine 0.5 mg/kg IV, injection glycopyrrolate 0.04 mg/kg IV, and injection midazolam 0.05 mg/kg IV to alley anxiety and parental separation and taken to the operation theater.

Upon arrival in the operating room, pulse oximetry, continuous electrocardiogram, and noninvasive blood pressure monitoring was started. An IV drip of Isolyte P was initiated. All patients were induced with injection propofol 2 mg/kg IV and maintained on spontaneous respiration with oxygen and 2%–3% sevoflurane in lateral position for giving caudal block. Caudal block was performed using 11/2 inch, 23G needle. The local anesthetic solution used was injection bupivacaine 0.25% - 2 mg/kg and injection 2% lignocaine with adrenaline 5 mg/kg. Normal saline was added to the mixture if required, to make a total volume of 1.25 ml/kg. Patients in Group C received caudal block with a local anesthetic solution and injection dexamethasone 0.1 mg/kg. Patients in Group I received caudal block with a local anesthetic solution. Injection dexamethasone 0.1 mg/kg was given IV in this group after giving caudal block.

All the blocks were performed by the same anesthetist. The adequacy of the block was tested over the incision site with a toothed forceps by surgeon after 10 min of performing block. Adequacy of blocked was judged as no change in respiratory rate, pulse rate, and blood pressure in response to testing. After incision, the inhalational agent was discontinued. Patients were then maintained on spontaneous respiration with oxygen supplementation of 4-5 L/min with a venturi mask. They were given sedation as required intraoperatively, with appropriate doses of injection propofol. In those patients where the block turned out to be inadequate, full general anesthesia with endotracheal intubation was instituted, and such patients were excluded from the study. Vital parameters were recorded intraoperatively every 5 min till the end of surgery. Patients were shifted to postoperative room after awakening and vital parameters were monitored along with oxygen supplementation for 1–2 h. Postoperative pain was assessed by Wong-Baker faces scale,[8] on a scale from 1 to 10, 1 indicating no pain and 10 indicating maximum pain [Figure 1]. The observer was blinded to the route of administration of dexamethasone at induction. Rescue analgesia was given for a score of 4 or more with IV paracetamol 15 mg/kg given slowly as a diluted solution. The time required for first rescue analgesia was recorded as the duration of postoperative analgesia.

Figure 1

Wong-Baker faces pain scale

The time required for Bromage motor score to become 0 was recorded as a time for complete regression of motor block. Bromage score of 0 indicated no paralysis, i.e., full flexion of legs and feet, 1 = inability to raise extended legs, 2 = inability to flex knees, and 3 = inability to flex ankle joint. The frequency of analgesic consumed in first 24 postoperative h was noted in both the groups. The frequency of analgesics consumed in next 24 postoperative h was also noted in both the groups. Postoperative nausea and vomiting if any and any other complication were recorded in both the groups. The observer was blinded to the route of administration of injection dexamethasone.

Statistical analysis

We have used α = 0.05 with a power (1 − β) of 0.9 with regard to the study conducted by Shrinivasan et al.[5] using duration of postoperative analgesia as the main response variable. We have studied thirty patients per group. Demographic data and continuous variables were analyzed by independent sample t-test. Categorical data were analyzed by Chi-square test. P = 0.05 or less was considered to be statistically significant.

RESULTS

The two groups were comparable in terms of demographic parameters and baseline pulse rate and blood pressure and pulse rate as shown in Table 1. The duration of postoperative analgesia was measured as the time till the first rescue analgesia was required by the patient. As per Wong-Baker faces scale modified for pediatric patients, when a score of 4 was observed, the rescue analgesia was given. Group D showed a significantly longer duration of postoperative analgesia than Group I [Table 2]. The time required for Bromage motor score to return to 0 was noted as a time for complete regression of motor block. There was no significant difference in the two groups regarding the same. Table 3 shows that the frequency of analgesics consumed in first 24 h was significantly low in group receiving caudal dexamethasone. However, there was no difference among the two groups in the analgesics consumed in next 24 h, i.e., on 2nd postoperative day [Table 4]. There was no evidence of fever, wound dehiscence, or wound infection among both the groups in the postoperative period.

Table 1

Demographic parameters

Table 2

Duration of analgesia and regression of motor block

Table 3

Analgesic consumption on first postoperative day

Table 4

Analgesic consumption on second postoperative day

DISCUSSION

Dexamethasone enhances the effect of regional blocks when used as an additive.[791011] It can also exert some analgesic action through its powerful anti-inflammatory properties. It reduces prostaglandin production which is responsible for enhanced nociception in inflamed tissues.[121314] Exact mechanism by which dexamethasone prolongs the regional block is not clearly understood. However, it might exert its action on nerve by its membrane stabilizing property.[15] Epidural injection of steroids prevents hyperalgesia by reducing nuclear factor Kβ.[16] Caudally or epidurally administered dexamethasone may also exert its action after systemic absorption.

Dexamethasone has been used caudally with local anesthetic drug in various doses such as 0.1–0.2 mg/kg body weight.[45617] We have used a dose of 0.1 mg/kg along with a local anesthetic mixture of lignocaine with adrenaline and bupivacaine. IV dexamethasone 0.5 mg/kg was used in previous studies along with caudal block to prolong postoperative analgesia.[46] In other studies such as pediatric tonsillectomies, a still higher dose in the range of 0.5–1 mg/kg was found to be necessary for pain reduction.[57] High dose of dexamethasone may be associated with complications such as wound infection and transient adrenal suppression[1718]. We have used an IV dose of 0.1 mg/kg only, which is the same as that used caudally. This served as a control for any action accountable to systemic absorption of caudally administered dexamethasone in Group D.

The mean age of our study population was around 4 years. We have used Wong-Baker Faces pain rating scale,[8] modified for pediatric patients as it is a nonverbal scale suitable for this age group. It is simple to understand and easy to train parents. This scale may not be as accurate as self-reported pain but has still shown good validity in pediatric patients who cannot be relied upon to report exact onset of pain.[19]

No patient was excluded from the study due to failed block. Srinivasan et al. conducted a study to compare the effect of 0.1 mg/kg dexamethasone as an adjuvant to caudal block with IV dexamethasone 0.5 mg/kg and a control group. They found that group receiving caudal dexamethasone had median time for first rescue analgesia of 720 min as against those receiving IV dexamethasone, in whom it was 620 min. Kim et al. found that addition of 0.1 mg/kg dexamethasone to caudal block led to significant reduction of pain scores in postoperative period for 48 h compared to patients of control group. Both the studies used 0.15% ropivacaine 1.5 ml/kg for their caudal block. Our study differed from the above in terms of local anesthetic used, which was a combination of 2% lignocaine with adrenaline and 0.5% bupivacaine. Furthermore, the IV dose of dexamethasone we used was less than previous study. We have found a significant increase in the duration of postoperative analgesia in patients who received caudal dexamethasone (626 ± 59 min) as compared to those who received IV dexamethasone in the same dose (194 ± 27 min). This was also reflected postoperatively in a significantly reduced analgesic consumption in the 1st postoperative day. However, on the 2nd postoperative day, the analgesic consumption was found to be similar in both groups. Our study indicated that the prolongation of action of postoperative analgesia is attributable to predominant caudal action of dexamethasone and not much affected by its action after systemic absorption. Furthermore, there was no significant difference in time for regression of motor block in the two groups.

In our study, we have followed our patients till discharge and found no complication attributable to dexamethasone-like wound infection, etc. However, we have not done any laboratory testing to rule out hyperglycemia or adrenal suppression which may be a theoretical possibility in these patients. This is a limitation of our study. However, adverse effects of dexamethasone when used in small and single doses are rare and minor.[71720] Again we could not do long-term follow up in these patients to rule out any delayed neurological symptoms that may be ascribed to the use of caudal additive. However, a study suggests no direct neurotoxicity after epidurally administered dexamethasone.[21]

CONCLUSIONS

From our study, we can conclude that dexamethasone 0.1 mg/kg, when used as an adjuvant to caudal anesthesia, can significantly prolong the duration of postoperative analgesia. It is better than IV dexamethasone at similar doses in controlling postoperative pain.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.