TAP Block with dexamethasone as a Pain Treatment Modality after Lower Abdominal Gynecological Procedures

INTRODUCTION

Lower Pfannenstiel incisions are the most usually utilized surgical procedures worldwide.¹ A Pfannenstiel is one type of abdominal incisions used for abdominal surgery.² It is used for gynecologic operations, orthopedics pelvic operations. ³ as well as Cesarean sections today. Pfannenstiel incision is used in hysterectomy operations ⁴. Large uterine size is a common reason to do the abdominal hysterectomy as an enlarged uterus requires better visualization and exposure to avoid the risk of blood loss, injury to other organs, and long operative time.⁵ Although laparoscopic operation is a less invasive technique, the surgical pain is predictable in the first 24h postoperative. ⁶

Post-operative pain is the most common problem in medicine especially in obstetrics and gynecology operations. Adequate postoperative analgesia can enhance recovery and increase patient comfort and decrease Post-operative complications.⁷

TAP block can give a good analgesia after lower abdominal surgery. ⁸ The safety and success rate of the TAP block has increased with the use of ultrasound^{. 9} The ultrasound guided (USG) TAP block for pain relief after surgery is utilized as a modality in lower abdominal surgeries. ¹⁰

The administered local anesthetics determine the TAP block duration, so administration of adjuvants can be utilized to extend the time of local anesthesia, also enhance the efficacy.¹¹

Dexamethasone is a glucocorticoid that provides anti-inflammatory action. It extends the action time of local anesthetics when utilized in peripheral blocks as an adjuvant.¹²

Dexamethasone improves the efficacy and extends the time of the local anesthetic by inhibiting the discharge of inflammatory mediators, decreasing ectopic neuronal release and depressing potassium channel-mediated discharge of nociceptive C-fibers.¹³

Glucocorticoids have a direct impact on the nerve conduction; also they induce perineural vasoconstriction resulting in delayed absorption of local anesthetics used. ¹⁴

The aim of this work is to assess the efficacy of TAP block with dexamethasone on pain relief after lower abdominal gynecological procedures.

PATIENTS AND METHODS

After approval of local ethics committee and patient’s written informed consent. A prospective randomized, controlled double-blinded study was performed at obstetrics and gynecology department of Al-Zahraa University Hospital from October 2018 to November 2019. Study included 100 women, American Society of Anesthesiologists physical status (ASA) I & II listed for elective lower abdominal gynecological procedures e.g. (hysterectomy; myomectomy; laparoscopy; ectopic pregnancy and ovarian cystectomy) under general anesthesia. Patients were excluded in case of refusal to participate in the study, history of allergy to the study drugs, uncontrolled hypertension, diabetes, cardiac disease, infection, coagulopathy, chronic pain and long- standing steroid therapy.

Pre-operative assessment was done for all women a day before operation.

 All patients were trained on visual analogue score (VAS) during the preoperative assessment by anesthesia resident.

VAS, which was used for pain assessment is a horizontal line, 10 cm in length ranging from

 0= (no pain) to 10= (worst pain).

The primary outcome was to assess postoperative pain scores using VAS at rest and on activity e.g. (cough, mobilization), immediately postoperative then every 2 hours in the next six hours, and at 10, 12,18 and 24hours. The secondary outcomes were time to first analgesic request, number of patients needed meperidine, overall dose of meperidine consumption and complications.

Patients were randomly allocated by computer generated number and sealed envelope technique into two groups: Group I (n=50): bilaterally received 15ml 0.2% levobupivacaine (Abbvie, Curida AS, Norway, Italy) plus 1.5 ml normal saline. Group II (n=50): bilaterally received 15 ml 0.2% levobupivacaine plus 1.5ml (6 mg) Dexamethasone (Amriya Pharmaceutical, Alexandria, Egypt).  The medications for the TAP block were prepared by an anesthesia resident who was not a part of the study.

Surgical technique:

All gynecological procedures were carried out by Pfannenstiel incisions. The incision is often 1-2 fingerbreadths above the pubic crest. 10-14 cm is enough incision, made via the subcutaneous tissue, fat to the fascia. The rectus muscle is dissected away from the fascia. and separated from each other. The peritoneum is incised to complete a Pfannenstiel incision. ¹⁵ 2gm Cefazolin IV was taken before the surgery.

Assessment parameters: Hemodynamics Heart rate (HR) and mean arterial blood pressure (MAP) were recorded before induction of anesthesia and each 15 minutes through the time of operation, immediately post-operative then every two hours in PACU for next six hours and at 10,12, 18 and 24hours. VAS to assess postoperative pain scores at rest and on activity, time of first analgesic request, number of patients needed meperidine, overall dose of meperidine consumption/24h and complications were also recorded. Meperidine 30 mg IV was given when VAS ≥4 or patient request analgesia, can be repeated up to 3 times.

Bradycardia is defined as fall in HR˂60 b/min and managed by IV atropine (0.01mg/kg). Hypotension is defined as fall in MAP˃20% of baseline value and was managed by IV crystalloid solution and ephedrine 6mg IV increments. Nausea and vomiting were managed by ondansetron 8mg.

In operating theatre, 18-G peripheral intravenous cannula was inserted for all patients and ringer lactate solution (10ml/kg/h) was infused. Patient was connected to the standard monitor (Electrocardiography, heart rate (HR), non-invasive blood pressure, and pulse oximetry). Baseline readings were recorded. All patients were given general anesthesia after preoxygenation with fentanyl (1µg /kg), propofol (2 mg/kg) and cisatracurium (0.15 mg/kg) to facilitate endotracheal intubation. Anesthesia was maintained by sevoflurane (2%), oxygen: air mixture (1:1) and maintenance dose cisatracurium (0.03mg/kg) as required.

After the operation was done, ultrasound guided (USG) TAP block was performed under aseptic precaution, linear US probe (high frequency 6–13 MHz) was used to identify the abdominis muscle plane with Ultrasound Machine (Sonosite, M- Turbo, Fuj ifilm Sonosite, Inc, Washington, USA). The probe was placed in mid axillary line in the transverse plane to obtain a transverse view of abdominal layers, after visualization of abdominal layers; a 22 G/80 mm blunt needle was introducedmedial to the probe and was advanced using in- plain techniquebetween the internal oblique and transverses abdominis muscles. Accurate placement of tip of the needle was facilitated by injection of (2ml) saline to hydro dissect the appropriate plane. After negative aspiration 15 ml 0.2% levobupivacaine plus either 1.5 ml of normal saline in group I (n=50) or 1.5ml (6mg) dexamethasone in group II (n=50) was injected on each side, distribution of local anesthetic was detected by appearance of a hypoechoic fluid pocket immediately deep to the hyperechoic facial plane between the internal oblique and transversus abdominis muscles. The injection was performed by an anesthesiologist who was blind to the composition of the injectate. After completion of surgery, muscle relaxant was antagonized by neostigmine (0.04 mg/kg) and atropine (0.01 ml/kg). Patient was extubated on meeting all criteria for extubation. Then patient was transferred to Post-Anesthesia Care Unit for further monitoring.

Statistical analysis was done by SPSS v25 (IBM®, Armonk, NY, USA). Quantitative data were expressed as mean ± SD& Median, “Interquartile range (IQR). Qualitative data were expressed as percentage. comparison between two means was done by using Independent t-test. Mann Whitney z test for two-group comparisons in non-parametric data. p-value <0.05 was considered significant.

Sample size calculation: Prior to the study; the number of women needed per group was given after a power calculation depending on data collected (Fouad et al., 2016). In the study, VAS score at 12h movement in group I was 5.20±0.41 and Group II was 4.24±0.83, and a large effect size (f =0.3497). A sample size of 48 patients was determined in each group to give 80% power for independent samples T test at 5% significance level using G. Power 3.19.2 software.

RESULTS

Demographic and operative data were comparable between both groups as shown in table (1).

P-value

Table 1: Demographic and operative data in both groups.

There was no significant difference between both groups as regard HR at different times as shown in figure (1).

Fig. 1: Comparison between both groups as regard heart rate changes at different times. Data are presented as (Mean ± SD).

Regarding MAP (mmHg) we found no significant difference between both groups at different times as shown in figure (2)

Fig. 2: Comparison between both groups as regard MAP changes at different times.Data are presented as (Mean ± SD).