Effect of dexamethasone on analgesic efficacy of transverse abdominis plane block in laparoscopic gynecological procedures: A prospective randomized clinical study

Abstract

Introduction

Although laparoscopic surgery is a minimally invasive procedure, acute surgical pain is common especially in the first postoperative day.[1] Postoperative pain following laparoscopic surgeries is of multifocal origin, with both parietal and visceral components, however, several studies have proven the opioid sparing effect with transverse abdominis plane (TAP) block in laparoscopic surgeries.[2]

Dexamethasone has shown to prolong the analgesia time when used as an adjuvant to local anesthetics (LA) in peripheral nerve blocks.[3,4] A number of studies have also shown an opioid sparing effect of steroids, when used intravenously perioperatively.[5] Hence, it is not known whether the effect of perineural (PN) administered dexamethasone is because of its peripheral action or because of its systemic absorption. We hypothesized that analgesic efficacy of intravenous (IV) dexamethasone would be equivalent to its PN administration, when added as an adjuvant with TAP block given to treat pain after laparoscopic gynecological procedures in a multimodal analgesic technique. The primary outcome of our study was the time to request of first rescue analgesic. Secondary outcome measures were the total amount of rescue analgesic required in 1^st 24 h postoperatively, the pain scores assessed by visual analogue score (VAS), incidence of nausea, and vomiting.

Material and Methods

This prospective, randomized, parallel treatment, double-blinded study was carried out at a tertiary care teaching hospital between 1^st July 2014 and 30^th June 2015. It was conducted after approval by the hospital ethical committee (NK/1607/MD/10089-90) and patient's written informed consent. Women with infertility of American society of anesthesiologists (ASA) physical status 1 or 2 undergoing laparoscopic gynecological procedures under general anesthesia (GA) were included in the study. Those with local infection at the site of injection, morbid obesity (body mass index >35 kg/m²), allergy to LA, patient refusal, severe respiratory or cardiac disorders, pre-existing neurological deficits, liver or renal insufficiency, pre-existing diabetics, patient on steroid treatment for any reason, perioperative use of steroids were excluded from the study.

Laparoscopic gynecological procedures were done on outpatient basis. Patients were educated about reporting of pain on the 11-point VAS, where 0 = no pain and 10 = worst imaginable pain in the pre-anesthesia check-up clinics. All the patients were kept fasting overnight (8 h for solids and 2 h for clear liquids). Forty patients were randomly assigned to one of either 2 groups (Group PN and Group IV) using a computer-generated random numbers table. The group allocation was concealed using sealed opaque envelopes technique. The patient, anesthesiologist performing the blocks, intraoperative anesthesiologists, surgeons, nurses, and data collecting person were blinded to the group allocation.

After induction of GA, patients in Group PN received ultrasound guided TAP block with 15 ml of 0.25% levobupivacaine (Levo Anawin, Neon Laboratories Limited, India) plus 4 mg (1 ml) PN dexamethasone (preservative methyl and phenyl paraben, decoin, Biocare, India) on either side and 2 ml of normal saline IV. Patients in Group IV received TAP block with 15 ml of 0.25% levobupivacaine plus 1 ml of normal saline on each side and 8 mg (2 ml) dexamethasone IV.

Study drugs were prepared by an independent anesthesiologist who was not involved in administrating the drug and in the postoperative follow-up of the patients. A second anesthesiologist blinded to the study drug preparation, administered the drug, and followed the patients postoperatively.

Standardized balanced anesthesia technique with muscle relaxation and endotracheal intubation was used in both the groups. GA was maintained with isoflurane and nitrous oxide in O₂ with target Minimum alveolar concentration (MAC) of 1–1.3. Heart rate (HR) and non-invasive blood pressure were maintained within 20% of the baseline. Surgical procedure was done in 30 to 45 degree trendelenburg position. Carboperitonium was achieved, and intra-abdominal pressure was maintained between 10 to 12 mmHg. In addition, 20 min before the completion of the surgery IV ondansetron 0.1 mg/kg and IV diclofenac 75 mg were given. At the end of the surgery, residual neuromuscular blockade was reversed with IV neostigmine 50 mic/kg and IV glycopyrolate 10 mic/kg, and patients were extubated after return of spontaneous respiration and consciousness.

TAP block was performed with linear probe (7–12 Hz) with Sonosite Turbo (Washington, USA) ultrasound machine. Ultrasonographic probe was applied transversely at the midpoint between the costal margin and the iliac crest on the mid-axillary line. Using an in plane technique and after identification of the plane between the internal oblique and transverse abdominis muscle block was performed with a 23G spinal needle (Quincke, USA).

In the post-anesthesia care unit (PACU), patients were monitored for BP, HR, and VAS score for pain during rest and cough, severity of nausea and vomiting [Annexure 1] every 15 min for 1 h and at 2 h, 4 h, and 6 h. Rescue analgesic IV tramadol 2 mg/kg was administered when VAS was >3 for initial 6 post-operative hours.[6] Patients were discharged from the PACU after 6 h, with advice to take oral paracetamol 500 mg as and when VAS >3 was observed by the patient. They were contacted over phone at 24 h to enquire about pain scores and paracetamol consumption. Time to first rescue analgesia and the 24 h analgesic consumption were recorded. Any incidence of nausea, vomiting, and complications associated with the procedure such as LA toxicity, hyperglycemias, and infection were recorded.

Results

Out of 40 enrolled patients who underwent laparoscopic gynecological procedures under GA, 36 patients were analyzed. The demographic characteristics and intraoperative data were comparable in both groups. The patients in both the groups had similar requirement of fentanyl [Table 1]. A statistically significant (P < 0.05) difference was observed in the time to request for first rescue analgesic, with the time being 6.632 ± 1.5 h in PN Group and 5.04 ± 1.7 h in IV Group. Paracetamol consumption in the first 24 h postoperative hours was less in PN Group as compared to IV Group (0.736 ± 0.25 vs. 0.964 ± 0.133), with the difference being statistically significant, P < 0.05 [Table 2].

There was no statistically significant difference in VAS score at rest among the two groups at all the points except at 12 h (P < 0.05), where the mean VAS score of PN Group was lesser than IV Group [Table 3]. There was no statistically significant difference in VAS score with cough among the two groups at all the points of time except at 4 and 12 h (P < 0.05), where the mean VAS score of PN Group was lesser than IV Group [Table 4]. At most of the time points in 24 h postoperatively, the median VAS score was <3 on rest and cough. None of the patients in either of the groups had nausea or vomiting.

Discussion

A number of previous studies have shown that single bolus injection of LA in TAP block can provide pain relief for about 3–4 h irrespective of the LA used.[7,8,9] In comparison to these studies, our study shows that the addition of dexamethasone in any form, IV or PN, causes prolongation of duration of analgesia. In another study by Kawahara et al., the authors studied the analgesic efficacy of ultrasound-guided TAP block after gynecologic laparoscopic surgery and found a significant reduction of tramadol consumption in the 0–6 h postoperative time period, specifying that the TAP block was possibly most effective for early postoperative pain.[10] In our study, we found that there was a statistically significant prolongation in the time to first request for rescue analgesic in PN Group (6.632 ± 1.5 h) as compared to the IV Group (5.04 ± 1.7 h) with the total rescue analgesic consumption also being less in the PN Group. Postoperative VAS pain scores at rest and on cough were <3 in both the groups most of the times in the first 24 h. Although mean difference in time to first rescue analgesic and paracetamol consumption looks clinically insignificant, low VAS scores seem to have clinical significance in a day care patient population who become home ready within 6 h.

Dexamethasone, a commonly used adjuvant, is known to extend the analgesia time when added to LA for different blocks. In a meta-analysis of randomized controlled trials on effects of combination of dexamethasone with local anesthetic solution for peripheral nerve (brachial plexus) blocks showed that it prolongs the block duration.[11] Parrington et al. observed that the addition of dexamethasone to 30 ml of 1.5% mepivacaine in a supraclavicular brachial plexus block prolonged the duration of analgesia [104 min (1.6 h)].[3] Cummings and colleagues observed a 1.9-fold and 1.5-fold increase in the duration of analgesia in interscalene block when dexamethasone (8 mg) was added to ropivacaine (30 ml, 0.5%) and bupivacaine (30 ml, 0.5%).[12] Akkaya et al. studied the effect of addition of dexamethasone (16 mg) to levo-bupivacaine (30 ml 0.25%) and compared it to control of TAP block with LA alone in patients undergoing lower segment caesarean section. The time before the administration of the first additional analgesic dose was prolonged, and pain scores and total consumption of tramadol were significantly lower in the dexamethasone group (13 h) compared to the levobupivacaine group (6).[13] Compared to our study, duration of analgesia was prolonged in this study in both PN and control group. This could be because Akkaya et al. administered TAP block at the end of surgery, whereas we had given the block after induction of GA. Further, as compared to our study, Akkaya et al. used higher volume of LA (30 ml vs. 60 ml) and higher dose of dexamethasone (8 mg vs. 16 mg). To the best of knowledge of authors, this is the first study comparing the additive effect of dexamethasone administration by various routes along with TAP block. In our study, dexamethasone did not seem to significantly prolong the analgesia time, independent of mode of administration, but it improved the quality of analgesia as depicted by the VAS in the first 24 h which is <3.

It is well-known that IV dexamethasone in an intermediate dose of 0.1–0.21 mg/kg has an opioid sparing effect when added to a multimodal regimen.[5,14,15,16] Similarly, we also used an intermediate dose of dexamethasone (8 mg) in our study.

In a single-injection peripheral nerve block (interscalene, supraclavicular, and ankle) with long-acting LA, the effectiveness of IV dexamethasone in prolonging the duration of analgesia is similar to PN dexamethasone.[17,18,19]

The precise mechanism of action of dexamethasone added to LA is unknown. Some studies have described a direct effect of glucocorticoids on nerve conduction, whereas others have reported that dexamethasone leads to PN vasoconstriction with concomitant slower absorption of the administered LA.

In our study, we administered dexamethasone (8 mg) in either route after induction of GA. The nausea and vomiting were nil in both the groups. This could be because of less opioid consumption as well as because of the well-known antiemetic effect of dexamethasone.[20,21]

Conclusion

The administration of dexamethasone in either route PN or IV in patients receiving bilateral TAP block with levobupivacaine improves the quality of analgesia in patients undergoing laparoscopic gynecological surgeries.

Annexure I: PONV grade

References