Abstract

Background

Epidural patient-controlled analgesia (EPCA) and intravenous patient-controlled analgesia (IVPCA) have been used widely in parturients after cesarean section. Although many studies have demonstrated the safety and effectiveness of both EPCA and IVPCA, their effects on bowel activity of patients who have undergone cesarean section delivery have not yet been investigated. The purpose of this study was to compare the effect of EPCA and IVPCA on bowel activity after cesarean section.

Methods

We collected data from 726 parturients who consented to receive either EPCA or IVPCA for postoperative analgesia following cesarean section delivery. All patients used postoperative PCA for at least 2 days. The analgesic solution for EPCA was 0.05% bupivacaine plus fentanyl (3 μg/mL), and that for IVPCA was 0.1% morphine. The patients were assessed by visual analog pain scale (VAS) scores at rest and in a dynamic state, time to first flatus passage after the surgery, and overall satisfaction after completion of the PCA course. Student's t test was used to determine intergroup differences.

Results

There were statistically significant differences between the EPCA and IVPCA groups in the time to first flatus passage, overall satisfaction and VAS scores at rest and in a dynamic state. Patients in the EPCA group had a shorter time to first flatus passage, higher overall satisfaction and lower VAS scores. In addition, regional anesthesia offered an apparently shorter time to first flatus passage in comparison with general anesthesia.

Conclusion

PCA is safe and effective in alleviating postoperative pain following cesarean section. EPCA offers a faster return of bowel activity, lower VAS scores, and better patient satisfaction than IVPCA.

Keywords

analgesia; epidural; analgesia, intravenous; analgesia, obstetrical; analgesia, patient-controlled; analgesics, opioid; intestines; peristalsis;

1. Introduction

Cesarean section, which accounted for more than one quarter of all deliveries in the USA in 2003,¹ is a common major hospital surgical procedure performed in the industrialized world. In the past decade, the high cesarean section rate in Taiwan varied between 33% and 35%.² Post-cesarean section pain cannot be overlooked because it may hinder the bond of affection and interaction between mother and child, early ambulation and discharge. Both epidural and intravenous opioids through patientcontrolled analgesia (PCA) provide effective postoperative analgesia and their use has become wide spread in past decades.^3,4

Gastrointestinal (GI) motility is increased by parasympathetic stimulation. It is well known that a surgical noxious stimulus activates inhibitory sympathetic splanchnic reflexes, and the choice of analgesic technique may affect the surgical stress response in several aspects, including these inhibitory reflexes.⁵ Thus, we can conceive that when the splanchnic nerves or splanchnic reflexes are blocked simply by spinal or epidural anesthesia (analgesia), increased motility may occur to forestall the development of ileus. Experimental studies also indicate that opioids have a profound inhibitory effect on resting and post-traumatic GI motility.^6,7 These effects are primarily seen during systemic opioid administration with intravenous PCA (IVPCA), conventional intramuscular opioid administration or epidural opioid administration.^8,9 However, many studies have demonstrated that more advantages could be seen with epidural PCA (EPCA) than with IVPCA, such as a better analgesic effect,^10,11 greater patient satisfaction,¹² fewer postoperative complications,^13,14 and acceleration of postoperative return of GI function.^15,16

Numerous studies have compared epidural analgesia and systemic analgesia with regard to postoperative recovery of GI function.^15,16 However, Neudecker et al¹⁷ in 1999 claimed that perioperative epidural analgesia did not have a clinically relevant effect on the duration of postoperative ileus after surgery. Since few clinical trials have elucidated the above issue, the aim of this study was to compare the effects of EPCA and IVPCA on the recovery of bowel function after cesarean section.

2. Methods

This retrospective study was conducted at China Medical University Hospital, Taichung, Taiwan. Data were collected between January 2006 and November 2007 from 726 consecutive patients who underwent elective or urgent cesarean section delivery under regional or general anesthesia and received PCA postoperatively. The decision for postoperative IVPCA or EPCA was principally based on patient preference. The drug delivery machine was Pain Management Provider™ (Abbott Laboratories, North Chicago, IL, USA). Patients who required any interventional treatment for respiratory depression, changed from IVPCA to EPCA or vice versa during the treatment course, or had interruption of PCA use even for a brief period, were excluded from the study. Patients in the EPCA group had an epidural catheter inserted between the L2 and L4 intervertebral spaces under local anesthesia before the operation. Patients were divided into IVPCA and EPCA groups. After arriving at the postanesthesia care unit, a PCA device was connected either to the patient’s epidural catheter or intravenous catheter within 30 minutes. Pain score was assessed before the start of PCA by a visual analog pain scale (VAS), with rating scores from 0 to 10, where 0 = no pain, 3 = mild pain, and 10 = worst pain possible. The VAS was treated as a continuous variable. VAS > 3 was considered as inadequate analgesia. The IVPCA solution was 0.1% morphine (1 mg/mL) at an initial background infusion rate of 0.2 mL per hour. The bolus dose was 1 mL each time with a lockout interval of 8 minutes. Inadequate analgesia was treated with a topup of 0.5−1 mL infusion followed by an increase in the background infusion of 0.1 mL per hour. The EPCA solution was 0.05% bupivacaine plus 3 μg/mL fentanyl at an initial background infusion rate of 3 mL per hour. The EPCA bolus was 3 mL each time with a lockout interval of 15 minutes. Inadequate analgesia was treated with a top-up of 1−3 mL infusion mixture followed by an increase in the background infusion of 1 mL per hour. After setting up the PCA device, continuous infusion and cumulative dose recording were started. All patients were visited daily by the staff of the PCA team in the morning and whenever necessary. Numbness, nausea, vomiting, pruritis or other adverse effects related to PCA were treated by a decrease in the infusion rate of 0.1 mL per hour in IVPCA and 1 mL per hour in EPCA. Pain intensity was assessed by VAS on every visit. Data col lection included patient age, body weight, and anesthetic method. The total PCA dose delivered was calculated by the PCA staff after a 2-day course had been completed.

The patients were assessed on the following: pain score at rest and in a dynamic state using the VAS, where dynamic state was defined as change from supine to sitting/standing position or coughing; time to first passage of flatus after the surgery (days); overall satisfaction. The overall satisfaction of a patient with postoperative analgesia was graded and recorded (1 = poor, 2 = fair, 3 = good, 4 = excellent) after completion of the PCA course.

2.1. Statistical analysis

The statistical analysis was performed by SPSS software (SPSS Inc., Chicago, IL, USA). Data are presented as mean ± standard deviation. Student’s t test was used to determine intergroup differences. A p value less than 0.05 was considered statistically significant.

3. Results

All patients saw adequate analgesia throughout the study period. The age of the EPCA and IVPCA groups was 33.32 ± 4.61 years and 32.03 ± 4.82 years, respectively; and body weight was 68.92 ± 9.76 kg and 70.15 ± 12.69 kg, respectively. The results are shown in Table 1. There were significant statistical differences between the EPCA and IVPCA groups in the time to first flatus passage, overall satisfaction and VAS scores at rest and in the dynamic state.

Patients in the EPCA group had a shorter time to first flatus passage and their overall satisfaction was also higher. The reported VAS scores at rest and in the dynamic state in this group of patients were 0.94 ± 0.44 and 2.13 ± 0.49, respectively. Patients in the IVPCA group had reported VAS scores at rest and in the dynamic state of 1.04 ± 0.53 and 2.40 ± 1.88, respectively. According to Kaplan−Meier survival analysis, time to first flatus passage after the surgery was significantly shorter in the EPCA group than in the IVPCA group (p< 0.05; Figure 1).

Table 2 shows the difference between general and regional anesthesia (spinal anesthesia or epidural anesthesia) in the effect on time to first flatus passage. Times to first flatus passage in general and regional anesthesia were 1.56 ± 0.64 days and 1.39 ± 0.56 days, respectively. Patients who received regional anesthesia had an apparently shorter time to first flatus passage compared with those who had general anesthesia. Thus, spinal or epidural anesthesia demonstrated a beneficial effect on postoperative ileus.

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Figure 1 Survival plots of times to first flatus. Time was reduced significantly in the EPCA group (p < 0.05, Kaplan− Meier survival analysis). EPCA = epidural patient-controlled analgesia; IVPCA = intravenous patient-controlled analgesia.

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4. Discussion

Epidural fentanyl plus local anesthetic in postoperative analgesia is a safe, simple and effective technique. It has become more popular because of the low incidence of side effects, such as nausea, vomiting, respiratory depression, and urinary retention.¹⁶ Many studies have demonstrated a clear benefit of epidural analgesia for postoperative pain relief after abdominal surgery.^17,18 Joshi et al suggest that, compared with morphine IVPCA, epidural fentanyl infusion provides significantly superior analgesia after surgery.¹⁶ Numerous studies have also shown that dynamic pain relief was better in the EPCA group than in the IVPCA group.^16,18 Our study has also corroborated these findings. Patients in the EPCA group had significantly lower pain scores at rest and in the dynamic state postoperatively.

Uncomplicated postoperative ileus occurs mostly in abdominal surgeries. GI motility is regulated by the sympathetic fibers from the thoracic and lumbar regions of the spinal cord (between T5 and L2). Many studies in the literature have documented quicker recovery of GI function with epidural analgesia.^13,18 The combination of a local anesthetic and opioid is popular for EPCA.¹⁹ The return of GI function is facilitated with a local anesthetic-based regimen for analgesia.²⁰ One potential disadvantage with epidural opioids is their adverse effect on gastric emptying.²¹ Fentanyl is commonly used in EPCA. One study showed that epidural administration of opioids can impair bowel function after hysterectomy.²² Geddes et al²¹ demonstrated that by adding fentanyl 100 μg to epidural bupivacaine 0.5% after cesarean section delivery, there was a significant delay in gastric emptying after the surgery. Our study showed a significant difference in the return of GI function between IVPCA and EPCA groups. This finding correlated with those in the studies of Liu et al²⁰ and Bredtmann et al²³ which demonstrated a quicker return of GI function with the use of thoracic EPCA in colon resections in comparison with IVPCA. However, a randomized prospective study conducted by Neudecker et al¹⁷ found no difference between these two groups.

The combination of epidural opioid plus low dose bupivacaine may reduce ileus compared with epidural opioid alone or systemic opioid.²⁴ In a randomized study on hip surgery,²² combined intraoperative and postoperative lumbar epidural local anesthetics reduced ileus compared with general anesthesia plus postoperative intravenous analgesia. The established positive effect of epidural local anesthetic administration is related to segmental visceral afferent/efferent blockade which, in abdominal surgery, can be obtained only by thoracic application of local anesthetic. Not surprisingly, the studies employing lumbar or low-thoracic epidural local anesthetics have not demonstrated the positive effects of epidural analgesia on ileus.²⁴ However, our study revealed that the time to first flatus was shorter in the EPCA group than in the IVPCA group, indicating a reduced duration of postoperative ileus. The earlier return of GI motility in the epidural bupivacaine/fentanyl group is in agreement with the results of previous studies demonstrating an ileus-reducing effect with local anesthetic-opioid mixtures.^20,24 One study suggested that the combined use of epidural bupivacaine and morphine in continuous infusion may not negatively affect the postoperative recovery of either colon motility or gastroduodenal function. Patients in this group saw a shorter time to flatus passage, a smaller inhibitory effect on gastroduodenal function, and a lower incidence of nausea and vomiting compared with intravenous morphine.²⁵ There was no correlation between the dose of morphine and the time to first passage of flatus. The absence of suppression of bowel movement by IVPCA morphine for postoperative pain control suggests that the favorable pharmacokinetic profile of IVPCA can help reduce morphine-induced bowel dysfunction at its therapeutic level.²⁶ Despite ample evidence showing that neuroaxial opioids are superior to parenterally administered opioids, their routine use is often limited by the availability of staff needed for appropriate monitoring of the side effects, such as delayed respiratory depression, and above all by the objection of surgeons and preference of patients.

Here, it was revealed that patients who underwent spinal or epidural anesthesia had a significantly quicker return of bowel activity than those who received general anesthesia. GI motility is known to be altered after general anesthesia. The extent of the change in motility is proportional to the length of anesthesia, and is known to be greater in patients who receive operations on the GI tract than on any other intra-abdominal organs.²⁷ Although various anesthetic agents used intraoperatively exert their effects by different mechanisms, a com mon result is inhibition of bowel motility.²⁸ Inhaled anesthetics may decrease GI motility, but in multiple animal studies, motility consistently recovered within a matter of minutes after cessation of anesthesia.²⁹ Thus, it is unlikely that inhaled anesthetics are responsible for decreased GI motility beyond the immediate postoperative period. Since GI tract motility may be reduced markedly after surgery, especially reflected by a delay in gastric emptying, these alterations are believed to be induced partly by surgery, partly by the residual effects of anesthetic agents, and, in particular, partly by opioids administered for postoperative pain relief.³⁰ Udassin et al demonstrated beneficial effects of epidural anesthesia on ileus.³¹ However, Shir et al found that postoperative ileus did not differ between general and spinal anesthesia groups.³²

Differences in postoperative pain score and alteration of GI motility arise from multiple factors (sympathetic or parasympathetic stimulation, pain, opioids, nitric oxide, spinal or epidural anesthesia, inhalation anesthetics, vasopressin, increased endogenous catecholamines).³³ In our study, the EPCA group obtained better pain relief and quicker recovery of postoperative GI motility than the IVPCA group. Pain is known for its effect in decreasing GI motility; whether the recovery of bowel movement has relevance to the postoperative pain score remains controversial. Several studies have shown that patients in EPCA groups had lower pain scores and earlier bowel movement than did IVPCA groups.^20,23,25 Other studies have shown no significant differences in recovery of bowel movement between EPCA and IVPCA groups despite lower pain scores in the former.³⁴⁻³⁶ Further studies with control of the factors (such as postoperative pain score) that affect bowel movement need to be done.

In conclusion, our findings revealed that PCA is safe and effective in patients experiencing postcesarean section pain. EPCA results in a quicker return of bowel activity, a lower VAS score, and greater patient satisfaction compared with IVPCA in the post-cesarean section period.