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 Table of Contents  
Year : 2019  |  Volume : 33  |  Issue : 3  |  Page : 141-146

Comparison of analgesic efficacy of dexamethasone versus tramadol as adjuvant to ropivacaine for oblique subcostal transversus abdominis plane block in open cholecystectomy

1 Department of Anaesthesiology and Critical Care, Pt. BD Sharma, PGIMS, Rohtak, Haryana, India
2 Department of Health, Govt of Haryana, Civil Hospital, Sonipat, Haryana, India

Date of Submission25-Aug-2019
Date of Decision11-Oct-2019
Date of Acceptance30-Oct-2019
Date of Web Publication5-Dec-2019

Correspondence Address:
Dr. Renu Bala
Department of Anaesthesiology and Critical Care, Pt. BD Sharma, PGIMS, Rohtak, Haryana
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijpn.ijpn_62_19

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Background: “Oblique subcostal” transversus abdominis plane (TAP) block is a combination of rectus abdominis and TAP block which is currently used in a wide variety of abdominal procedures. Dexamethasone and tramadol are both used as adjuvants in several blocks for improving efficacy and prolonging analgesia. The present study was intended to compare both these drugs along with ropivacaine in ultrasound-guided subcostal TAP block following open cholecystectomy. Materials and Methods: The present prospective, randomized, and double-blind study was conducted in 60 adult patients of either sex undergoing open cholecystectomy. The patients were randomized into two groups; Group D (n = 30) and Group T (n = 30). Former received 18 ml of 0.75% ropivacaine with 2 ml (8 mg) of dexamethasone whereas latter received 18 ml of 0.75% ropivacaine with 2 ml (25 mg/ml) of tramadol through right-sided ultrasound-guided oblique subcostal TAP block after the induction of general anesthesia following standard protocol. Postoperative pain at rest and knee flexion as per visual analog scale (VAS) score, time for first and second rescue analgesia, total tramadol consumption in 24 h, sedation and nausea score, and quality of healing at discharge were noted. Results: Requirement for first and second rescue analgesia was similar in two groups but overall 24 h tramadol consumption was less in Group D. VAS score was similar in two groups except at 4 and 24 h. None of the patients were sedated, but nausea score was less in Group D. The quality of wound healing was good in both groups. Conclusion: The addition of 8 mg dexamethasone or 50 mg tramadol as adjuvants to ropivacaine is effective and safe drugs to administer in TAP block for postoperative analgesia following open cholecystectomy.

Keywords: Dexamethasone, open cholecystectomy, ropivacaine, tramadol, transversus abdominis plane block

How to cite this article:
Kiran S, Bala R, Kumar K. Comparison of analgesic efficacy of dexamethasone versus tramadol as adjuvant to ropivacaine for oblique subcostal transversus abdominis plane block in open cholecystectomy. Indian J Pain 2019;33:141-6

How to cite this URL:
Kiran S, Bala R, Kumar K. Comparison of analgesic efficacy of dexamethasone versus tramadol as adjuvant to ropivacaine for oblique subcostal transversus abdominis plane block in open cholecystectomy. Indian J Pain [serial online] 2019 [cited 2020 Sep 23];33:141-6. Available from: http://www.indianjpain.org/text.asp?2019/33/3/141/272386

  Introduction Top

Cholecystectomy is one of the most commonly performed upper abdominal surgeries. Although laparoscopic approach has become the gold standard for this procedure; open approach is still carried out in certain conditions such as gall bladder carcinoma, cholecystobiliary fistula, gall stone ileus, and conversion of laparoscopic to open procedure.[1],[2],[3] Postoperative pain after cholecystectomy may be severe, sustained and can cause significant morbidity to the patients. Various analgesics such as opioids and Non Steroidal Anti Inflammatory Drugs (NSAIDS) are used for treating pain; however, their use is associated with several side effects. Alternative technique to systemic analgesia is regional anesthesia with local anesthetics.[4]

The transversus abdominis plane (TAP) block is a rapidly expanding regional anesthesia technique that provides analgesia to the parietal peritoneum as well as skin and muscles of the anterior abdominal wall following abdominal surgery. It has been described as an effective component of multimodal postoperative analgesia following a wide variety of abdominal procedures.[5],[6],[7],[8] Among all local anesthetics, ropivacaine is quite favored in regional blocks due to its long duration of action, safety profile, and better sensory block.[9] Dexamethasone and tramadol both have been successfully used as adjuvants to local anesthetics in several nerve blocks.[10],[11],[12],[13] There is paucity of literature comparing dexamethasone and tramadol as adjuvant to ropivacaine in oblique subcostal approach of TAP block for postoperative analgesia following open cholecystectomy. Therefore, the present study was planned to do their comparative evaluation for analgesic efficacy and analyze any complications, if any.

  Materials and Methods Top

The present prospective, randomized, double-blind, comparative study was conducted in the department of anesthesiology and critical care of our institution. The approval from institutional ethics committee was obtained, and the study was registered in the clinical trial register. Sixty patients of either sex, aged between 20 and 60 years, belonging to the American Society of Anesthesiologists physical status I-II, scheduled to undergo conventional open cholecystectomy under general anesthesia were included in the study. Patients who had a contraindication to regional block, history of local anesthetic allergy, psychiatric disorders, chronic opioid use, body mass index > 35 kgm − 2, and diabetes mellitus were excluded. Informed written consent for participation in the study was obtained from the patients prior to surgery.

Randomization was done using computer-generated randomization number which were kept in opaque sealed envelopes to ensure concealment and blinding. Group D (n = 30) received 18 ml of 0.75% ropivacaine with 2 ml (8 mg) of dexamethasone whereas Group T (n = 30) received 18 ml of 0.75% ropivacaine with 2 ml (25 mg/ml) of tramadol through ultrasound-guided oblique subcostal TAP block on the right side.

The patients were examined before surgery and subjected to complete physical as well as systemic examination. All patients were prescribed tablet alprazolam 0.25 mg and tablet ranitidine 150 mg before sleep and 2 h before surgery. Prophylactic antiemetics were not administered. Linear visual analog scale (VAS) on 0–10 cm was explained to the patients for the assessment of postoperative pain, where 0 denoted no pain and 10 denoted worst pain imaginable.

A standardized general anesthesia technique comprising of morphine (0.15 mg/kg), propofol (2 mg/kg), and vecuronium bromide (0.1 mg/kg) was followed in all patients and airway was secured. The maintenance of anesthesia was carried out using nitrous oxide and oxygen in isoflurane (1MAC). No other analgesic was administered during surgery.

Ultrasound-guided oblique subcostal TAP block was performed before surgical incision. Under all aseptic conditions, the probe was placed medial to the linea semilunaris near coastal margins. Images were obtained using a Sonosite M-Turbo ultrasound machine with an HFL 38 × 13–6 MHz 40 mm broadband linear array probe. The TAP block was performed with a 23G Quincke spinal needle attached to 10 cm extension line for drug infusion. The needle was inserted in a sagittal plane approximately 3–4 cm medial to ultrasound probe and was held parallel to the long axis of the probe (in-plane technique). The probe was moved slightly anterior to image the skin puncture in superficial course and then gradually posterior to the midaxillary line, directing the needle to the correct position into the plane below the internal oblique and above the transversus abdominis muscle [Figure 1]. Initially, 1 ml normal saline was injected after negative aspiration to check the drug spread in the right plane. After confirming the plane, the entire study drug as per group allocation was injected into the TAP plane in incremental doses over a period of 10 s. The spread of drug in the TAP plane was observed on ultrasound imaging.
Figure 1:Ultrasonography-guided subcostal block

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The surgery was commenced 5 min after performing the block. Intraoperative heart rate, electrocardiogram, noninvasive blood pressure, and oxygen saturation through pulse oximetry were monitored every 5 min till 15 min and then every 15 min till the end of the surgery. The duration of surgery was recorded.

After completion of surgical procedure and successful extubation, the patients were transferred to postanesthesia care unit. All patients were asked to score their pain at rest and on movement (knee flexion) 2, 4, 6, 12, and 24 h after surgery. When VAS score was ≥4, injection paracetamol (1 gm) was administrated intravenously as first rescue analgesic. If pain was not relieved and VAS score remained ≥4, injection tramadol 50 mg was administered intravenously as second rescue analgesic. In the surgical ward, injection tramadol 100 mg intramuscularly was administered as and when required. In wards, nursing staff administers the drug at our institution; thus, we adviced intramuscular route for tramadol as a standard protocol of our center. The total consumption of tramadol in 24 h postoperatively was noted.

Sedation score was noted using a sedation scale (awake and alert = 0; quietly awake = 1; asleep but easily roused = 2; deep sleep = 3). Nausea was noted using a scoring system (none = 0; mild = 1; moderate = 2; and severe = 3). The requirement of rescue antiemetics to any patient complaining of nausea was noted. Any episode of hypotension (decrease in mean arterial pressure ≥10% of the baseline value), bradycardia (heart rate <60/min), nausea or any other side effect as a result of subcostal TAP block or tramadol use, was recorded and managed accordingly. All patients were followed up till 1 week after surgery, and wound was examined for quality of healing, where 0 = unsatisfactory, 1 = satisfactory, and 2 = good. It was subjective assessment for wound healing done by operating surgeons at the time of follow-up on the basis of several parameters such as delay in healing, infection, necrosis, and gaping.

The primary outcome measured in this study was 24 h tramadol consumption. Secondary outcomes measured included time to first request for analgesic, VAS score, nausea score, sedation score, and any other side effects.

Sample size

Since there was no similar study of such kind, we conducted 10 pilot cases in each group (not included in the study), and found tramadol consumption was 106 ± 30 mg and 132 ± 42 mg in Group D and T, respectively; 28 patients per group were required to have a power of 80%, alpha error 0.05 and beta error 0.2.

Statistical analysis

At the end of the study, data were compiled and analyzed using Statistical Package of Social Sciences (SPSS) version 17.0, Chicago IL, USA. Data were presented as mean with standard deviations or number and percentage. Demographic data were analyzed using Student's t-test. Paired comparisons at each time interval were performed using the t-test. Categorical data were analyzed using Chi-square test or Fisher's exact test as appropriate. P ≤ 0.05 was considered as statistically significant.

  Results Top

The demographic profile of the patients in the two groups was comparable, as shown in [Table 1]. Majority of patients in both groups were females, and indications in all the patients in both groups were gall stones. The duration of surgery was 63 ± 15.29 min in Group D and 67.0 ± 14.77 min in Group T (P = 0.30). A number of patients requiring first rescue analgesia (paracetamol), second rescue analgesia (tramadol) and time required for it was comparable in two groups [Table 2]. Despite the fact that all patients required postoperative pain relief, but overall tramadol consumption in 24 h was much more in Group T (P< 0.01), as shown in [Table 3]. It was calculated by dividing the total consumption of tramadol in a group by the total number of patients (n = 30). VAS score at rest and knee flexion at various time intervals during postoperative period is shown in [Figure 2] and [Figure 3], respectively. VAS at rest was significantly higher in Group T at 4 and 24 h, whereas VAS at knee flexion was higher at 24 h in the same group. The sedation score and nausea score were comparable in two groups [Figure 4]. Antiemetics were required in three patients (10%) and six patients (20%) in Group D and T, respectively. [Table 4] shows the quality of healing in two groups which was mostly good and comparable in two groups.
Table 1: Demographic profile of patients (n=30)

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Table 2: First and second rescue analgesia requirement (n=30)

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Table 3: Number of patients requiring postoperative tramadol (mg) and total tramadol consumption (n=30)

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Figure 2:Comparison of visual analog scale scores at rest between two groups at various postoperative hours

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Figure 3:Comparison of visual analog scale score at knee flexion between the two study groups at various postoperative hours

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Figure 4:(a) Sedation score (b) Nausea score between two study groups at various postoperative hours

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Table 4: Quality of healing in two groups (n=30)

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  Discussion Top

The TAP block is a relatively new type of peripheral nerve block which anesthetises thoracolumbar nerves (T6-L1). It involves injection of local anesthetic agent through the lumbar triangle of Petit into the TAP which lies between the internal oblique and transversus abdominis muscle.[14] An ultrasound-guided approach was first described in 2007 by Hebbard et al., and it has led to increased success rate and accuracy of TAP block and decreased complication rate as compared to landmark technique.[15],[16] The oblique subcostal approach of TAP block provides a wider analgesic blockade suitable for surgery both superior and inferior to umbilicus. The results of this block are encouraging and substantially reduce the need of systemic analgesia.[17]

The results of our study show that the total tramadol consumption during 24 h was less with dexamethasone when compared with tramadol as an adjuvant to ropivacaine.

Dexamethasone is a synthetic adrenal corticosteroid with potent anti-inflammatory action. It is a very potent and highly selective glucocorticoid. It is 40 times more potent than hydrocortisone. It is used as an adjuvant to various local anesthetics as it increases the duration of the nerve blockade.[10],[18] Tramadol is a synthetic 4-phenyl-piperidine analog of codeine. It is an analgesic drug, acting at central and peripheral μ-opioid and monoaminergic receptors. It also exhibits local anesthetic property. Tramadol has a moderate affinity for mu-receptors and weak kappa and delta-opioid receptor affinity but is 5–10 times less potent than morphine as an analgesic. It is used for the treatment of severe acute pain and chronic pain. It is also used as an adjuvant to various local anesthetic agents.[13],[19]

In our study, we used dexamethasone and tramadol as adjuvants as they are easily available and have been used successfully in various nerve blocks. The pharmacological profile of dexamethasone and tramadol, along with their minimal side effects, makes them attractive drugs as an adjuvant in nerve blocks. We used 8 mg of dexamethasone as an adjuvant to ropivacaine for TAP block in open cholecystectomy. The dose of 8 mg was chosen because it has been used previously for perineural injection in several studies and is within clinically safe dose range. We used tramadol in the dosage of 50 mg as an adjuvant to ropivacaine in our study. In literature, various doses of tramadol (40–200 mg) have been used as an adjuvant to local anesthetics. If we had used 100–200 mg of tramadol may be it would have been more effective. But with increasing dose, the incidence of adverse effects such as nausea, vomiting would have been on the rise.[20]

Our results are similar to results by Ammar and Mahmoud in which dexamethasone added to bupivacaine in TAP block for abdominal hysterectomy was found to prolong the duration of block.[21] Dexamethasone has been evaluated as adjuvant to ropivacaine for incisional infiltration in laparoscopic cholecystectomy and supraclavicular brachial plexus block. In both the studies, it was found to prolong analgesia.[22],[23] In a recent meta-analysis, it has been found that dexamethasone as adjuvant to local anesthetics in TAP block decreases VAS score, postoperative opioid consumption, and nausea and vomiting.[24]

Tramadol has been used as adjuvant to ropivacaine in brachial plexus block. It was observed that the addition of 50 mg of tramadol to 0.375% ropivacaine extended the onset and duration of block with improved quality of postoperative analgesia.[12] However, contrary to our study, 100 mg of tramadol added to 0.75% ropivacaine for axillary plexus block was not found to have any added advantage. The authors attributed this finding to the fact that in their study, the patients underwent minor to moderate orthopedic procedure which generally produce mild intensity of postoperative pain. Second, they did not follow the VAS pain scores beyond the time of the first pain medication; therefore, total analgesic consumption in 48 h could not be ascertained. Moreover, they speculated that the lack of analgesic effect of the addition of tramadol could be related to use of long-acting local anesthetics, i.e., ropivacaine which could have masked any potential peripheral analgesic effect of tramadol on the nerve block.[25]

In our study, the two groups were comparable in relation to sedation scores at various postoperative hours (P > 0.05). None of our patients was deeply sedated. Our study findings are in agreement with that of Dikman et al., who evaluated the efficacy of tramadol as an adjuvant to ropivacaine for axillary brachial plexus block in uremic patients.[26] The incidence of nausea and vomiting after open cholecystectomy is 28.6%. In our study, moderate degree of nausea was observed in 10% of patients in Group D requiring antiemetics. Although the addition of dexamethasone to ropivacaine for TAP block decreases the incidence of nausea and vomiting; the mechanism of its antiemetic action is not well understood. A commonly held theory is that corticosteroids exert their antiemetic activity via prostaglandin antagonism. There was no significant difference in the occurrence of nausea between two groups in our study. This could be because of less number of patients in our study or due to the reason that dexamethasone was administered in blocks whose systemic absorption may not be to that extent to prevent nausea and vomiting.

No other complication attributable to TAP block procedures such as liver trauma or bowel injury were observed in our study as we did the procedure under ultrasound guidance, which allows real-time visualization of needle tip and relevant anatomical structures, increasing the margin of safety.

There are few limitations in our study. First, we did not have any control group in our study. All the patients in our study received unilateral TAP block with 18 ml of 0.75% ropivacaine. Hence, the analgesic efficacy of TAP block could not be demonstrated by comparing with control group. Second, we could not assess the onset of abdominal wall sensory block as patients were under general anesthesia. Third, in literature TAP block has been performed with Stimuplex needle as it has a blunt end, but in our study, we used Quincke spinal needle because of cost constraints. Although Quincke spinal needle can cause puncturing of peritoneum, we performed TAP block carefully, tracing the tip of the needle under ultrasound guidance. We did not observe any complication related to block performance in any patient. Fourth, we did not perform a dose-response study to determine if a lower dose of ropivacaine or dexamethasone or tramadol would lead to the same results. Fifth, our study population was small, and observations during the postoperative period were limited to 24 h only. Therefore, further studies are required to evaluate the optimal doses of dexamethasone or tramadol as an adjuvant to local anesthetics for TAP block in a larger patient population.

  Conclusion Top

We conclude that ultrasound-guided subcostal approach of TAP block is a safe and effective technique for postoperative pain relief in open cholecystectomy. Further, dexamethasone and tramadol are useful adjuvants to ropivacaine, though out of two, former was better in attenuating analgesic dose. However, more dose-response studies involving large number of patients to determine optimum dose of dexamethasone or tramadol with ropivacaine are required to establish their role for TAP block by subcostal approach in patients undergoing open cholecystectomy.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Parks R, Welsh F. Gall bladder and biliary surgery. In: Farquharson M, Moran B, editors. Farquharson's Textbook of Operative General Surgery. 9th ed. United Kingdom, UK: Hodder Arnold; 2014. p. 321-38.  Back to cited text no. 1
Bittner R. Laparoscopic surgery--15 years after clinical introduction. World J Surg 2006;30:1190-203.  Back to cited text no. 2
Ros A, Gustafsson L, Krook H, Nordgren CE, Thorell A, Wallin G, et al. Laparoscopic cholecystectomy versus mini-laparotomy cholecystectomy: A prospective, randomized, single-blind study. Ann Surg 2001;234:741-9.  Back to cited text no. 3
Kenneth C 3rd, Mohamed AN. Opioids agonist and antagonists. In: Flood P, Rathmell JP, Shafer S, editors. Pharmacology and Physiology in Anesthetic Practice. 5th ed. Philadelphia: Wolters Kluwer Health; 2015. p. 217-56.  Back to cited text no. 4
Heil JW, Ilfeld BM, Loland VJ, Sandhu NS, Mariano ER. Ultrasound-guided transversus abdominis plane catheters and ambulatory perineural infusions for outpatient inguinal hernia repair. Reg Anesth Pain Med 2010;35:556-8.  Back to cited text no. 5
Mukhtar K, Singh S. Transversus abdominis plane block for laparoscopic surgery. Br J Anaesth 2009;102:143-4.  Back to cited text no. 6
McDonnell JG, Curley G, Carney J, Benton A, Costello J, Maharaj CH, et al. The analgesic efficacy of transversus abdominis plane block after cesarean delivery: A randomized controlled trial. Anesth Analg 2008;106:186-91.  Back to cited text no. 7
Carney J, McDonnell JG, Ochana A, Bhinder R, Laffey JG. The transversus abdominis plane block provides effective postoperative analgesia in patients undergoing total abdominal hysterectomy. Anesth Analg 2008;107:2056-60.  Back to cited text no. 8
Kuthiala G, Chaudhary G. Ropivacaine: A review of its pharmacology and clinical use. Indian J Anaesth 2011;55:104-10.  Back to cited text no. 9
[PUBMED]  [Full text]  
Kumar S, Palaria U, Sinha AK, Punera DC, Pandey V. Comparative evaluation of ropivacaine and ropivacaine with dexamethasone in supraclavicular brachial plexus block for postoperative analgesia. Anesth Essays Res 2014;8:202-8.  Back to cited text no. 10
  [Full text]  
Kim YJ, Lee GY, Kim DY, Kim CH, Baik HJ, Heo S. Dexamathasone added to levobupivacaine improves postoperative analgesia in ultrasound guided interscalene brachial plexus blockade for arthroscopic shoulder surgery. Korean J Anesthesiol 2012;62:130-4.  Back to cited text no. 11
Senel AC, Ukinc O, Timurkaynak A. Does the addition of tramadol and ketamine to ropivacaine prolong the axillary brachial plexus block? Biomed Res Int 2014;2014:62-8.  Back to cited text no. 12
Kaabachi O, Ouezini R, Koubaa W, Ghrab B, Zargouni A, Ben Abdelaziz A. Tramadol as an adjuvant to lidocaine for axillary brachial plexus block. Anesth Analg 2009;108:367-70.  Back to cited text no. 13
Charlton S, Cyna AM, Middleton P, Griffiths JD. Perioperative transversus abdominis plane (TAP) blocks for analgesia after abdominal surgery. Cochrane Database Syst Rev 2010;8:CD007705.  Back to cited text no. 14
Hebbard P, Fujiwara Y, Shibata Y, Royse C. Ultrasound-guided transversus abdominis plane (TAP) block. Anaesth Intensive Care 2007;35:616-7.  Back to cited text no. 15
McDonnell JG, O'Donnell B, Curley G, Heffernan A, Power C, Laffey JG. The analgesic efficacy of transversus abdominis plane block after abdominal surgery: A prospective randomized controlled trial. Anesth Analg 2007;104:193-7.  Back to cited text no. 16
Hebbard P. Subcostal transversus abdominis plane block under ultrasound guidance. Anesth Analg 2008;106:674-5.  Back to cited text no. 17
Becker DE. Basic and clinical pharmacology of glucocorticosteroids. Anesth Prog 2013;60:25-31.  Back to cited text no. 18
Stoelting RK, Hillier SC. Opioids agonist and antagonists. In: Pharmacology and Physiology in Anesthetic Practice. 4th ed. Philadelphia: Lippincott Williams and Wilkins; 2006. p. 87-126.  Back to cited text no. 19
Robaux S, Blunt C, Viel E, Cuvillon P, Nouguier P, Dautel G, et al. Tramadol added to 1.5% mepivacaine for axillary brachial plexus block improves postoperative analgesia dose-dependently. Anesth Analg 2004;98:1172-7.  Back to cited text no. 20
Ammar AS, Mahmoud KM. Effect of adding dexamethasone to bupivacaine on transversus abdominis plane block for abdominal hysterectomy: A prospective randomized controlled trial. Saudi J Anaesth 2012;6:229-33.  Back to cited text no. 21
[PUBMED]  [Full text]  
Mendez EG, Garcia de Alba-Garcia JE, Sahagun-Flores JE. Analgesic efficacy of incisional infiltration of ropivacaine vs ropivacaine with dexamethasone during elective laparoscopic cholecystectomy. Cir Cir 2013;81:383-93.   Back to cited text no. 22
Biradar PA, Kaimar P, Gopalakrishna K. Effect of dexamethasone added to lidocaine in supraclavicular brachial plexus block: A prospective, randomised, double-blind study. Indian J Anaesth 2013;57:180-4.  Back to cited text no. 23
[PUBMED]  [Full text]  
Zhang D, Zhou C, Wei D, Ge L, Li Q. Dexamethasone added to local anesthetics in ultrasound-guided transversus abdominis plain (TAP) block for analgesia after abdominal surgery: A systematic review and meta-analysis of randomized controlled trials. PLoS One 2019;14:e0209646.  Back to cited text no. 24
Kesimci E, Izdes S, Gozdemir M, Kanbak O. Tramadol does not prolong the effect of ropivacaine 7.5 mg/ml for axillary brachial plexus block. Acta Anaesthesiol Scand 2007;51:736-41.  Back to cited text no. 25
Dikman B, Gamli M, Horasanli E, Ornek D, Pekel M, Selcuk A. The effects of adding tramadol to ropivacaine on axillary brachial plexus blockade in uremic patients. Turk J Med Sci 2009;39:733-9.  Back to cited text no. 26


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2], [Table 3], [Table 4]


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