Efficacy of single dose epidural morphine versus intermittent low-dose epidural morphine along with bupivacaine for postcaesarean section analgesia.

BACKGROUND: Obstetric anesthesia presents a challenge to the anesthesiologist. The effective pain management allows the partu-rient adequate degree of comfort and promotes physical reco-very and a sense of well being.
MATERIALS AND METHODS: This randomized controlled study was designed to assess the analgesic efficacy and side effects of 1.20 mg single-dose epidural morphine (Group 1) versus intermittent 12 hourly epidural morphine (0.5 mg) with bupivacaine (Group2) for postoperative analgesia in lower segment caesarean section cases.
RESULTS: Each group consisted of 36 patients. Demographic characteristics of two groups were comparable and differences among them were not statistically significant. Mean duration of analgesia was significantly longer in group one patients (16.5±2.5h) in comparison to group two patients (11.5±1.5h). Mean highest visual analog scales (VAS scale) was significantly lower (3.2±0.9) in group one patients in comparison of group two (6.7±0.8) patients. Only 43% patient in group one required supplementary perenteral analgesic (Paracetamole/Diclofenac) and 71% required epidural morphine/bupivacaine in group two. Mean number of supplementary perenteral analgesic required in group one was 0.7 and it was 1.8 in group two. There was no significant difference in nausea, vomiting, itching, and pruritis in two groups of patients.
CONCLUSION: Our study showed that the use of single dose epidural morphine is associated with lower pain scores at rest and movement when compared to intermittent epidural morphine with bupivacaine in postcaesarean section analgesia.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Obstetric anesthesia presents a spectrum of challenges to the anesthesiologist not only in provision of the acute intrapartum labor analgesia, but also in provi-sion of postoperative analgesia.[1] It has been well established that postoperative pain leads to patient discomfort, decreased level of satisfaction, prolonged recovery and higher health care cost. Specifically in the parturient inadequate postoperative pain control after cesarean section may interfere with ambulation, breast-feeding, and early maternal bonding with the infant. The effective pain management does not necessarily make the partu-rient totally insensible to the fact that cesarean section was performed, but rather, it allows adequate degree of comfort and promotes physical reco-very and a sense of well being.[2] Effective postoperative analgesia can be provided with systemic administration of opioids and/or nonopioid analgesics as well as with epidural and spinal techniques.[3-10] The American Academy of Pediatrics Committee on Drugs lists morphine, fentanyl, and butorphanol as mater-nally administered opioids that are compatible with breast-feeding.[11] This prospective randomized controlled study was designed to assess the analgesic efficacy and side effects of single dose epidural morphine versus intermittent epidural morphine with bupivacaine for postoperative analgesia in lower segment caesarean section cases.

MATERIALS AND METHODS

This randomized control study was conducted in a hospital of UP. Approval for study was obtained from the institutional ethical committee and written informed consent from each patient was taken before the study. Postoperative visual analog scales (VAS score) was considered the primary end point in determination of the sample size. It was determined that a sample size of 36 patients in each group would have 80% power to detect 30% difference in VAS while limiting the type-I error less than 5%. Seventy two patients at term American Society of Anesthesiology Classification (ASA-I and ASA-II) scheduled for lower segment caesarean section under epidural anesthesia were selected for study and divided into two groups with the help of simple random sampling (sealed coded envelop). Patients with complicated pregnancy, acute fetal distress, history of hypersensitivity to opioids/local anesthetics were excluded. In the preanaesthetic visit, all the patients were made familiar with the study plan and visual analogue scales (VAS) to be used in the assessment by the investigators. Respiratory rate, arterial blood pressure, peripheral arterial saturation, and heart rate were monitored throughout the perioperative period. To avoid bias staff involved in anesthesia was not involved in pain assessment.

Epidural anesthesia (15 mL of 2% Inj lignocaine) was used for caesarean section in both groups. Intensity of postoperative pain during the first 24 h postoperatively was assessed at hourly interval using a visual analogue pain score (VAS).[12] 0 denotes “no pain” while 10 denotes “worst pain imaginable.” When the patient was asleep, no VAS assessments were made and VAS of 0 was given. Group one received single dose of 1.20 mg epidural morphine along with 15 mL of 2% Inj lignocaine (which was used for epidural anesthesia) and subsequently Inj Paracetamole/Inj Diclofenac when the pain score was 4 or more, or if the patient requested analgesia (whichever occurred earlier). Total supplementary analgesics (Inj Paracetamole/Inj Diclofenac) required was recorded. Group two received 15 mL of 2% Inj lignocaine epidurally initially for caesarean section and 0.5 mg epidural morphine (dissolved in 10 mL of 0.125% Inj bupivacaine) after on hour with the help of epidural catheter and it was repeated after 12 h. If patient requested analgesia at interval less than 12 h Inj bupivacaine alone was given with the help of epidural catheter. Total supplementary analgesics (Inj morphine/ inj bupivacaine) for group two was also recorded.

The onset of analgesia was defined as the time from injection of the study medication to first reduction in pain intensity by at least 1 in VAS; and the duration of analgesia was defined as the time between the onset of analgesia and either a return to baseline VAS or the time when additional pain medication was requested, whichever occurred first. The occurrence of nausea and vomiting, pruritus, shivering and respiratory depression (respiratory rate <12/min), sedation, and hypotension was noted up to 24 h following administration of the study medication. The collected data were analyzed using the Statistical Package for Social Science (version 10.0 for Windows, SPSS). Analysis of variance /Chi square test was used to compare the variables between groups. P value of <0.05 was considered significant.

RESULTS

A total of 72 patients were studied. Each group consisted of 36 patients. Demographic characteristics (age, weight, height and systolic, and diastolic BP) of two groups as mean, standard deviation and range are depicted in Table 1. Demographic characteristics of two groups are comparable and differences among them were not statistically significant.

Table 1

Demographic characteristics of patients

Table 2 gives the comparison of postoperative analgesia in two groups of patients. Mean duration of analgesia was significantly longer in group one patients (16.5±2.5 h) receiving single dose epidural morphine in comparison to group two patients (11.5±1.5 h) receiving intermittent epidural morphine with bupivacaine [Figure 1]. Mean highest pain score (VAS scale) was significantly lower (3.2±0.9) in group one patients in comparison of group two (6.7±0.8) patients. Only 43% patient in group one required supplementary analgesic (Inj Paracetamole/Diclofenac and 71% required Inj epidural Morphine/Inj bupivacaine in group 2. These differences in two groups were found statistically significant. Mean number of supplementary analgesic required in group one was 0.7 and it was 1.8 in group two.

Table 2

Comparison of postoperative analgesia in two groups

Figure 1

Mean duration of analgesia in various groups

Table 3 depicts comparison of side effects of drugs in two groups of patients. There was no significant difference in nausea, vomiting, itching, and pruritis in two groups of patients. Incidence of respiratory depression, sedation, and hypotension were nil in two groups of patients.

Table 3

Comparison of side effects in two groups of patients

DISCUSSION

Epidural morphine was first reported as an effective analgesic in humans by Behar et al.[13] In 1979, reports of its use in obstetric patients were published.[14] It has been reported that more than 90% of obstetric anesthesiologists administer subarachnoid or epidural opioids in parturients undergoing cesarean section under spinal, epidural, or combined spinal epidural anesthesia.[1516] Craig et al. observed that degree and duration of analgesia increase as the dose of epidural morphine increases over the range of 0 to 3.75 mg. Even the smallest dose 1.25 mg, had a modest patient controlled analgesia that persisted through the 24-h study period. In their study little relation was found between dose and side effects (nausea, vomiting, itching, and pruritis) over the range studied. They observed for optimal analgesia, augmentation of epidural morphine with systemic analgesics, or other epidural medications may be necessary.[17] Our study indicates that the degree and duration of analgesia was better with 1.20 mg single dose epidural morphine in comparison to intermittent morphine and requirement of supplementary/rescue analgesic was significantly less in patients receiving single dose epidural morphine. In our study there was no significant difference in nausea, vomiting, itching and pruritis in two groups of patients. Craig et al.[17] also reported that side effects of epidural morphine were not dose related. Incidence of respiratory depression, sedation, and hypotension were nil in two groups of patients. It had been reported that epidural opioid offers several advantages to partu-rients recovering from cesarean section. These include excellent postoperative analgesia with a decrease in total dose of opioids required, a low level of sedation, minimal accumulation of the drug in breast milk, facilitation of early ambulation and early return of bowel function.[18] In our study also single dose of epidural morphine was found more convenient, less cumbersome and less costly to intermittent epidural morphine with bupivacaine for postcaesarean section analgesia.

CONCLUSION

In conclusion, our study showed that the use of single-dose epidural morphine was associated with lower pain scores at rest and movement when compared to intermittent epidural morphine with bupivacaine in postcaesarean section analgesia. The use of nonsteroidal anti-inflammatory drugs (NSAIDs) enhanced the efficacy of analgesia of single dose epidural morphine. We did not detect any severe side effects (e.g. respiratory depression and sedation) with the doses of single dose epidural morphine used. There was no significant difference in nausea, vomiting, itching, and pruritis in two groups of patient. Single dose epidural morphine was found more convenient, less cumbersome and less costly to intermittent epidural morphine for postcaesarean section analgesia.