Abstract
Objective
Transversus abdominis plane (TAP) block is a recently introduced regional anesthesia technique that is used for postoperative pain reduction in some abdominal surgeries. The present study evaluated the efficacy of the TAP block on the post laparoscopic cholecystectomy pain intensity and analgesic consumption.
Methods
Fifty-four patients were enrolled in three groups: TAP block with normal saline (Group 1, n = 18); TAP block with bupivacaine (Group 2, n = 18); and TAP block with bupivacaine plus sufentanil (Group 3, n = 18). The time to the first fentanyl request, fentanyl consumption in the 24 hours following surgery, and postoperative pain intensity at 30 minutes, 1 hour, 6 hours, 12 hours, and 24 hours following discharge for recovery were measured and recorded.
Results
The total amount of 24-hour fentanyl consumption was higher in Group 1 (877.8 ± 338.8 μg) than either Group 2 (566.7 ± 367.8 μg) or Group 3 (555.5 ± 356.8 μg; p = 0.03). Postoperative pain score was higher in Group 1 than intervention groups (p = 0.006); however, there was no significant difference in intervention groups. The time to the first fentanyl request in Group 1 (79.44 ± 42.2) was significantly lower than Group 3 (206.38 ± 112.7; p = 0.001).
Conclusion
The present study demonstrated that bilateral TAP block with 0.5% bupivacaine reduces post laparoscopic cholecystectomy pain intensity and fentanyl request and prolongs time to the first analgesic request. Adding sufentanil to the block solution reduced neither pain intensity nor fentanyl further consumption.
Keywords
multimodal analgesic techniquepostoperative paintransversus abdominis plane;
1. Introduction
Postoperative pain management is a challenging issue in anesthesiology and one of the most important factors in postoperative rehabilitation and return to normal activities. Opioids as the most efficient used analgesic agents, but are accompanied with adverse effects such as nausea, vomiting, pruritus, respiratory depression, and urinary retention. The adverse effects of opioids are dose-dependent, so using a multimodal approach to pain control would enhance analgesia while decreasing opioid side effects.1
Transversus abdominis plane (TAP) block has been recently introduced as a postoperative pain control modality to reduce the usage of opioids and reduce the side effects and patient management costs.2, 3, 4 Almost a decade has passed since the introduction of TAP block, and tremendous interest has evolved into its utility; it has been used for pain control in the radical prostatectomy, hysterectomy, cesarean delivery, and laparoscopic surgeries.1
The analgesia produced by neuraxial opioids alone, or opioids as adjuvants to local anesthetics, has been demonstrated for acute postoperative pain control.5, 6 Research in the past three decades has proven the effectiveness of opioid receptors for excitatory and inhibitory peptides in peripheral tissues including sensory afferent nerve terminals. Several studies have been conducted to evaluate the effect of opioids as adjuvants in peripheral nerve blocks7, 8; however, there are many controversies about their efficacy. To our knowledge, the effect of sufentanil as an adjuvant in TAP block has not been evaluated yet.
In the present study, it was hypnotized that the TAP block can efficiently reduce postlaparoscopic cholecystectomy pain intensity and adding the sufentanil to local anesthetic solution can enhance this effect. The pain intensity and time to the first fentanyl request were evaluated as secondary outcomes.
2. Methods
After getting the approval of the Institutional Ethics Committee and patients' informed consent, 54 participants scheduled for elective laparoscopic cholecystectomy under general anesthesia were enrolled in this study.
Patients with a history of addiction (including opioids and benzodiazepines), chronic pain, sensitivity to prescribed drugs, psychological disorders, coagulopathy, any contraindication for TAP block, and those receiving any drugs within 48 hours of surgery (except for the study protocol) were not enrolled to this study. Any patients with surgical complication, and in cases where the operation was longer than 100 minutes, were also excluded from this study.
In a controlled, randomized double blind design and using a computer-generated randomization list, patients were allocated into three groups, to receive: 32 mL of 0.9% normal saline 16 mL in each side (Group 1, n = 18); 30 mL of bupivacaine 0.5% plus 2 mL normal saline, 16 mL in each side (Group 2, n = 18); or 30 mL of bupivacaine 0.5% plus 2 mL (10 μg) sufentanil, 16 mL in each side (Group 3, n = 18) at the end of surgical procedure.
At the time of the preoperative visit, a trained investigator explained the study plan and the scale [visual analog scale (VAS) for pain] used in the study to patients. Drug solutions were prepared and blocks were done by an anesthesiologist who was not involved in the data collection, and patients received their block when they were under anesthesia; thus both the investigators and the patients were blinded to the group assignment.
The severity of postoperative pain was measured and recorded using a 10-cm VAS scale, where 0 = no pain and 10 = the worst possible pain. Patients were asked to score the pain at different times after the operation including the time of discharge from recovery and 30 minutes, 1 hour, 6 hours, 12 hours, and 24 hours later.
In the operating room, an infusion of 7 mL/kg lactated Ringer's solution was commenced. All patients were monitored with an electrocardiogram, noninvasive blood pressure, and pulse oximetry. All patients received standardized general anesthesia. The induction of anesthesia was done by administration of 2 mg/kg intravenous (IV) propofol and 3 μg/kg IV fentanyl, tracheal intubation was facilitated by 0.6 mg/kg IV atracurium and anesthesia was maintained with 80–100 μg/kg/min propofol and 1 μg/kg IV fentanyl and 0.3 mg/kg IV atracurium administrated every 30 minutes.
At the end of the surgical procedure and before wound dressing, the skin was prepared with 2% chlorhexidine solution. Blocks were performed by a senior trainee experienced in the technique, under the direct supervision of a study investigator. Images were obtained using a Sonosite M-Turbo ultrasound machine with an L38 from 10 MHz to 5 MHz 38-mm broadband linear array probe. Blocks were performed using a 150 mm Stimuplex needle (B-Braun Medical, Bethlehem, PA, USA). A high frequency linear ultrasound probe (6–13 MHz) is placed transverse to the abdominal wall between the costal margin and iliac crest on the mid axillary line. The satisfactory image was aimed to visualize the subcutaneous fat, external oblique muscle, internal oblique muscle, transversus abdominis muscle, peritoneum, and intraperitoneal cavity. The needle was introduced in plane of the ultrasound probe directly under the probe and advanced until it reaches the plane between the internal oblique and transversus abdominis muscles. Upon reaching the plane, 3 mL of prepared solution was injected. The transversus abdominis plane was visualized expanding with the injection and total blood anesthetic solution was injected.
Subsequently, anesthetic administration was stopped and neuromuscular blockade was antagonized by IV administration of 2.5 mg of neostigmine along with 1.0 mg atropine. Patients were considered awake when they opened their eyes on command or after gentle tactile stimulation; they were extubated soon thereafter.
Patients were scheduled to receive patient-controlled analgesia (PCA) following surgery. The loading dose of fentanyl was administrated at the first time of reported pain score >3. The patients were attached to a PCA device. The PCA device was programmed to achieve each patient's desired level of comfort and contained 50 mL of fentanyl. Bolus dose of 50 μg fentanyl with lockout at 8-minute intervals with no preset of maximum dose was set. The postoperative fentanyl consumption was considered as primary outcome.
For the partial η2 of 0.1 for the primary endpoint, the sample size of 18 patients per arm was calculated to achieve 80% power with a two-sided significance level of 0.05.
Continuous variables were presented as mean (standard deviation). Normality of variables was tested with Kolmogorov–Smirnov test; they followed normal distribution. In order to investigate the difference between the three groups, one-way analysis of variance (ANOVA) was used. Associations between sex, American Society of Anesthesiologists class, and groups were tested using Chi-square test. Repeated measure ANOVA was used to test the equality of time trend of pain score between three groups, and post hoc Tukey HSD test was performed to detect differences between groups.
Data were analyzed using SPSS version 20 (SPSS Inc., Chicago, IL, USA). For all analyses, p < 0.5 was considered statistically significant.
3. Results
Fifty-four patients were included in the study, 18 patients in each group. There was no protocol violation, so all data were analyzed. The mean age of patients was 45.39 ± 10.7 years (range, 28–61 years). Characteristics of the patients are summarized in Table 1. Patients in the three groups did not differ significantly in terms of the mean age and sex (p = 0.86 and p = 0.80, respectively). However, the mean duration of operation, time to the first fentanyl request and amount of 24-hour postoperation fentanyl usage were significantly different in the three groups (p = 0.019, p = 0.002, and p = 0.012, respectively). Post hoc Tukey test showed that the mean time to first fentanyl request in Group 1 (79.44 ± 42.20 minutes) was significantly lower than other groups (ANOVA, p = 0.001), but there was no significant difference between Group 2 (144.44 ± 83.1 minutes) and Group 3 (206.30 ± 112.7 minutes; p = 0.13). The 24-hour postoperation fentanyl usage was significantly higher in Group 1 (877.8 ± 338.8 μg) than either Group 2 (566.7 ± 367.8 μg) or Group 3 (555.5 ± 356.8 μg; p = 0.03 and p = 0.02, respectively), although Groups 2 and 3 showed no significant difference (post hoc Tukey test, p = 0.99).
VAS at all five measured times, separated for three groups are presented in Figure 1. Based on multivariable repeated measures ANOVA, there was a difference in three groups (p = 0.004). Post hoc Tukey test demonstrated that the changes in the mean of pain score in Group 1 was significantly different from both Groups 2 and 3 (p = 0.004 and p = 0.006, respectively); however, the two experimental groups were not significantly different (p = 0.98).
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The mean of pain score increased during 6 hours after discharge for recovery, and then decreased. Indeed, maximum pain intensity was experienced at 6 hours following discharge for recovery, (6.44 ± 2.20 in Group 1, 3.61 ± 2.25 in Group 2, and 3.94 ± 2.24 in Group 3). In the Group 1, the gain of pain increase in the first 6 hours was statistically more than other two groups (Figure 1).
4. Discussion
The present study demonstrates that bilateral TAP blockade with 30 mL 0.5% bupivacaine (15 mL in each side) decreases post laparoscopic cholecystectomy pain intensity and analgesic consumption. However, adding 10 μg of sufentanil to the local anesthetic solution did not change either pain intensity or analgesic consumption. The time to the first analgesic rescue was longer in patients who received the TAP block. In all groups, the maximum pain intensity was recorded at the 6th hour following discharge for recovery, and it decreased beyond this time.
The pain and discomfort following laparoscopic cholecystectomy causes serious side effects such as nausea, vomiting, delay embolization, cardiac, and pulmonary problems and increased the costs.3, 9, 10 Opiates, which are the most commonly used and efficient postoperative analgesic agents, accompany adverse effects such as nausea, vomiting, pruritus, and respiratory depression.11 The adverse effects of opioids are dose dependent, so using a multimodal approach to pain control would enhance analgesia while decreasing the side effects.10, 12
TAP block is a regional anesthesia technique that blocks the abdominal wall neural afferents by introducing local anesthetic into the neurofascial plane between the internal oblique and transversus abdominis muscles. Since transversus abdominis plane block with the aim of anesthetizing nerve supplies to the anterior abdominal wall was first described in 2001 by Rafi,2 its use in postoperative pain management has gained popularity.
A meta-analysis study on the efficacy of TAP block on postoperative pain reduction demonstrated that it reduces the need for postoperative opioid, prolongs the time to the first request of analgesic, provides more effective pain relief and reduces opioid-associated side effects.13
Some studies have illustrated the efficacy of TAP block in decreasing postoperative pain intensity and analgesic requirement in procedures such as radical prostatectomy, hysterectomy, cesarean delivery, and laparoscopic surgery.13, 14, 15, 16, 17
In one study, bilateral ultrasound-guided TAP block and local anesthetic infiltration of trocar insertion sites showed the same efficacy for overall postoperative pain in a heterogeneous group of patients undergoing laparoscopic cholecystectomy. In this study there were no significant differences in age and sex between the three groups, so the confounder effect of these variables had no effect on the result of pain intensity between the groups.18
Considering the above mentioned points, there is substantial potential for TAP block to be part of an effective multimodal postoperative pain control regimen.
Adding adjuvants to various peripheral nerve block solutions has been studied previously. It has been shown that adding epinephrine to levobupivacaine reduces its peak plasma concentration after unilateral TAP blocks, with no remarkable effects on block characteristics or duration.19 However, adding clonidine to a TAP block using bupivacaine did not affect wound hyperalgesia index or improve short- or long-term pain scores in women undergoing elective cesarean delivery.20 The addition of fentanyl to local anesthetics improved the quality and prolonged the duration of cervical plexus block.21Buprenorphine may enhance and prolong the analgesic effect of bupivacaine when used for sciatic nerve blocks in patients undergoing foot and ankle surgery under general anesthesia.22
To our knowledge, the effect of adding opioids to TAP block on postoperative pain control and opioid consumption has not been studied previously.
The analgesic effect of opioids through the central nervous system (CNS) has been thoroughly studied previously, evidence demonstrates that opioid anti-nociception can be initiated by activation of opioid receptors located outside the CNS.23 Previous studies indicate that a large amount of the analgesic effects produced by systemically administered opioids can be mediated by peripheral opioid receptors.23, 24, 25, 26, 27 Clearly opioid agonists acting peripherally can be more attractive because of their possibly less central acting side effects, the typical adverse effects of opioid.
In the present study, sufentanil effect in TAP block was tested, sufentanil had no effect either on pain intensity or on postoperative fentanyl consumption. Other opioids such as fentanyl could be evaluated in future. Whether higher doses of sufentanil as an adjuvant to TAP block would act similarly is unclear.
There are some limitations in the present study. It is possible that the power of this study was not sufficient to show the effects of adding sufentanil to TAPS block. A higher-powered study is necessary to evaluate the incidence of opioid side effect. The plasma concentration of bupivacaine was not measured, which is considered as a possible shortcoming.
TAP block is a safe procedure; however, a few side effects have been reported previously. TAP blocks can result in elevated plasma ropivacaine concentrations, which may be associated with neurotoxicity.28 In one report, TAP block led to hepatic trauma.29 Colon puncture or hematoma formation are other potential side effects of TAP block.30
In conclusion, a bilateral TAP block with 0.5% bupivacaine decreases postlaparoscopic cholecystectomy pain and analgesic consumption. The time to the first 24-hour analgesic rescue would be longer in patients who receive TAP block. Adding sufentanil to the local anesthetic solution does not change pain intensity, postoperative fentanyl consumption, or time to the first analgesic request.