|Year : 2011 | Volume
| Issue : 1 | Page : 30-34
Comparative evaluation of transversus abdominis plane block with transcutaneous electrical nerve stimulation for postoperative analgesia following lower segment caesarean section
Sukhyanti Kerai, Kirti N Saxena, Raktima Anand, JS Dali, Bharti Taneja
Department of Anaesthesiology and Critical Care, Maulana Azad Medical College and Associated Lok Nayak Hospital, New Delhi, India
|Date of Web Publication||25-Aug-2011|
D-65, MMTC colony, Mehrauli road, New Delhi-110017
Source of Support: None, Conflict of Interest: None
Background : Pain relief after caesarean is more compelling than any other surgery. As most commonly used modalities are associated with various side-effects, a multimodal approach is recommended. Transversus abdominis plane (TAP) block and transcutaneous electrical nerve stimulation (TENS) as part of multimodal postoperative analgesia regimes have been shown to be promising following caesarean section.
Materials and Methods : 40 patients undergoing caesarean section under spinal anaesthesia were randomly allocated into 2 groups, first group receiving TAP block and second receiving TENS. In postoperative period pain, nausea and vomiting, sedation was recorded at 30 minutes, 2, 4, 6, 12 and 24 hours.
Results : Both TAP block and TENS were effective for post caesarean analgesia as a part of multimodal regimen. In both groups VAS was less than 3 at each time interval. None of the patients required rescue analgesia. There was no complication with TAP block. Three patients in TENS group complained of discomfort and apprehension because of tingling sensation of TENS.
Conclusion : Both TAP block and TENS as a part of multimodal analgesia are effective following caesarean delivery. Both decrease requirement of opioids and thus associated side effects as a result of which the mother is able to care for baby more effectively.
Keywords: Lower segment caesarean section, post-caesarean analgesia, transversusabdominis plane block, transcutaneous electrical nerve stimulation
|How to cite this article:|
Kerai S, Saxena KN, Anand R, Dali J S, Taneja B. Comparative evaluation of transversus abdominis plane block with transcutaneous electrical nerve stimulation for postoperative analgesia following lower segment caesarean section. J Obstet Anaesth Crit Care 2011;1:30-4
|How to cite this URL:|
Kerai S, Saxena KN, Anand R, Dali J S, Taneja B. Comparative evaluation of transversus abdominis plane block with transcutaneous electrical nerve stimulation for postoperative analgesia following lower segment caesarean section. J Obstet Anaesth Crit Care [serial online] 2011 [cited 2019 Jun 16];1:30-4. Available from: http://www.joacc.com/text.asp?2011/1/1/30/84253
| Introduction|| |
Caesarean section is one of the most commonly performed surgeries. Adequate pain relief after caesarean is more compelling than any other surgery as inadequate pain relief in post operative period leads to decreased ability of mother to breast feed effectively and care for baby. Also the risk of thromboembolic disease which is increased during pregnancy is aggravated by immobility due to pain. 
The most commonly used modality for pain control after caesarean delivery is opioid administration either systematically as intramuscular injection, patient controlled analgesia, intravenously or as a part of regional anaesthesia. Opioids produce effective analgesia but are associated with frequent side effects such as nausea/vomiting, pruritis, sedation, respiratory depression, transfer through breast milk to neonates leading to transient neurobehavioral changes. Therefore a multimodal approach is recommended whenever possible and should focus not only on acute, but also chronic post-caesarean pain.  Transcutaneous electrical nerve stimulation (TENS) has been used for postoperative analgesia following various types of surgeries.
TENS is a simple, non-invasive form of acupuncture therapy; it does not need expertise like other therapy forms. TENS units usually have a single channel (with two electrodes) or dual channels (with four electrodes). An electronic stimulus generator transmits pulses to the electrodes which are placed directly on the skin. There are limited numbers of studies on TENS for post-caesarean analgesia.  TENS showed a greater reduction in the intensity and duration of the pain and in the amount of additional medication administered.
The transversus abdominis plane (TAP) block is a new regional anaesthesia technique where local anaesthetics are injected into TAP, which is an anatomic space between internal oblique and transversus abdominis muscle and spans the abdomen wherever these two muscles exit. It targets nerves of anterolateral abdomen wall.  Various randomized trials have been done to establish analgesic efficacy of TAP block following retro pubic prostatectomy,  large bowel resection via a midline abdominal incision,  laparoscopic cholecystectomy  and for total abdominal hysterectomy. 
There are two randomized trials , and one case report  till date in literature regarding role of TAP block for post caesarean analgesia. Results showed adequate analgesia, decreased consumption of opioids, decreased nausea and sedation in postoperative period. However this technique needs further evaluation and comparison with other modalities.
| Materials and Methods|| |
Following clearance from the institutional review board, this prospective randomized study was performed on 40 ASA grade 1 and 2 patients admitted to our institution undergoing either elective or emergency caesarean section by Pfannelstein incision under spinal anaesthesia. Following detailed pre-anaesthetic check up, written informed consent was taken from all patients. Only patient who were willing and not having history of allergy to opioids, amide group of local anaesthetic and nonsteroidal anti-inflammatory drugs, deranged coagulation or bleeding parameters and local infections were included in this study. Patients with Cardiovascular, pulmonary and neurological diseases were excluded from study.
Patients were randomly allocated by computer generated random tables to one of two groups comprising 20 patients each. In group TAP block was given at the end of surgery on both sides. In group TENS was performed after completion of surgery.
The patients were explained about thewhole procedure. In operation theatre monitoring for electrocardiography, pulse oximetry and non-invasive blood pressure was started and continued till patient was out of operation room. All patients were pre-loaded with Ringer Lactate amounting to10 ml/kg body weight before start of surgery and received spinal anaesthesia with 2-2.5 ml of 0.5% heavy bupivacaine. Surgery was conducted after adequate sensory level was achieved.
Group transversus abdominis plane
In this groupbilateral TAP block in lumbar triangle of Petit was given at the end of surgery. The technique described by Rafi et al., consisting of double pop elicited by the needle was used and 15 ml of 0.25% bupivacaine was used on each side. The skin was pierced by a blunt regional anaesthesia needle and the needle was advanced at right angle to the skin, which resulted in a "pop "sensation as external oblique muscle was traversed. Further advancement resulted in a second "pop "which signaled entry to transverses abdominis fascial.
Group transcutaneous electrical nerve stimulation
In this group, after surgery, patients were shifted to postoperative ward. TENS was started with portable TENS unit after block had receded below T10 level. The TENS skin electrodes were positioned across the surgical incision site at adjacent dermatome levels. The frequency of TENS was set to 50Hz and the intensity of electrical stimulation initially at 9-12 mA, which was reduced if not tolerated by patient. It was continued for 30 mins every 2 hrs. The stimulation using TENS unit for 30 minutes is the minimum effective time after which analgesic action begins and was used every two hours as per the protocol suggested by Wang et al.
In both groups injection diclofenac 1 mg/kg was started 8 hrly in postoperative ward as per routine analgesic protocol being followed in our institution by obstetrician starting from the time when patient has arrived in postsurgical ward from operation theatre. In both the groups' presence of pain, nausea and sedation was assessed at 30 mins, 2, 4, 6, 12 and 24 hours after completion of surgery.
Visual analogue score (VAS) score was used to assess pain at rest and at movements, at above intervals. At any point of time if VAS was>3, injection tramadol 1 mg/kg body weight 8 hrly was planned to be added. If patient had VAS >3 even 30 minutes after receiving tramadol then morphine 2mg i.v. was planned to be started by PCA pump with lock out interval fixed in 20min.
Nausea and vomiting was assessed on a three point score:
0. No nausea/vomiting in past time interval and
1. nausea in the past interval,
2. vomiting in the past interval.
Nausea lasting for more than 10 mins and vomiting was planned to be treated with parentral ondensetron 0.1 mg/kg body weight.
Sedation was assessed on a score of 0 to 2:
0. awake and alert patient,
1. a quietly awake patient and
2. asleep but easily arousable patient.
Statistical analyses were performed using a standard statistical program. Demographic data were analyzed using student's t-test. Repeated measurements (pain scores, nausea and vomiting scores) were found to be non normally distributed. Comparisons between groups at each time point was made by nonparametric Mann Whitney test and within groups by Wilcoxon signed rank sum test. The p value <0.05 was set as statistically significant.
| Results|| |
Forty patients were taken up for the study, twenty were randomized to undergo TAP block and twenty were randomized to undergo TENS.
Groups were comparable in terms of age, weight and height [Table 1].
|Table 1: Age, height and weight characteristics of patients in two groups|
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Both TAP block and TENS were effective for post caesarean analgesia as a part of multimodal regimen. In both groups VAS was less than 3 at each time interval [Table 2]. None of the patients in either group required rescue analgesia.
|Table 2: Visual analogue scores in two groups at different time intervals|
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The comparison of VAS scores at different time intervals showed that TAP block had better analgesia than TENS at all time intervals.
The incidence of nausea was found to be statistical significantly lower in TENS group at 2 hours and comparable at all other time intervals [Table 3].
|Table 3: Nausea and vomiting scores in the two groups at different time intervals|
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There was no sedation in patients of either group at any time interval and the two groups were comparable. There was no complication with TAP block. Three patients in TENS group complained of discomfort and apprehension because of tingling sensation of TENS.
| Discussion|| |
Post-caesarean pain has two components. Somatic pain arising from nociceptors within the abdominal wounds has both cutaneous and deep components. It is transmitted within the anterior divisions of spinal segmental nerves, usually T10-L1, which runs laterally in the abdominal wall between the layers of transversus abdominis and internal oblique muscles. Visceral uterine nociceptive stimuli return via afferent nerve stimuli that ascend through the inferior hypogastric plexus and enter spinal cord via the T10-L1 spinal nerves. 
TAP block is a new regional anaesthesia technique which targets nerves of anterolateral abdominal wall. The posterior / landmark technique used in this study mainly blocks T10-L1 or T9-11, which supplies lower abdominal wall. Therefore this technique is suitable for surgeries below umbilicus. Subcostal approach of TAP block provides analgesia for periumbilical surgeries.  Since TAP block affects only somatic component of post-caesarean pain, it has always been used as a part of multimodal analgesia.
TENS stimulates nerves endings by electrical stimulation and works on gate theory of pain relief.  The analgesic effect of TENS has been found to be dependent on duration, intensity, frequency of stimulation and location of electrodes.  While previous systemic review Reeve et al. concluded that there is little if any evidence in favor of TENS for postoperative analgesia. Bjordal et al. found that these reviews were based on evaluation model that included trials with possible ineffective treatment dose and they recommended that TENS administered with a strong subnoxious intensity at an adequate frequency in the wound area can significantly reduce analgesic consumption for postoperative pain. Therefore in this study frequency of 50Hz, amplitude of 9-12 mA was selected for 30 minutes every 2 hours and 4 electrodes were placed in peri-incisional dermatomes.
Somatic pain may be relieved by both TAP block and TENS; but visceral pain may be more difficult to treat. NSAIDs are effective for relieving pain related to menstrual cramping and, as a result, there has been interest in the use of NSAID to treat a component of pain after caesarean delivery. Unfortunately NSAIDs alone are insufficient to effectively treat post-caesarean delivery pain. However, inclusion of NSAIDs in a multimodal approach to pain relief after caesarean delivery has been very successful both in improving the quality of analgesia resulting from systemic or neuraxially administered opioids and reducing side effects.  In this study we used TAP block and TENS in combination with diclofenac sodium in post-operative period so as to cover both somatic and visceral pain of caesarean section.
TAP block has not been compared with other analgesic modalities so far. This is the first study where its use for postoperative analgesia following caesarean section has been compared with TENS.
TAP block and TENS both are found to be efficacious as a part of multimodal analgesia following caesarean delivery. The use of TENS is cost effective, does not need monitoring and being a non pharmacological method is free from side effects of drugs which can affect mother or newborn. However use of this modality is cumbersome as it has to be repeatedly used over time to achieve adequate analgesia. Also the tingling sensation of electrical current can be unacceptable to some patients.
TAP block had better pain control over pain as compared to TENS at various time intervals. Single shot of local anaesthetic drugs in TAP results in analgesia for 24-48 hours as this plane is relatively avascular. No side effect of TAP was observed in this study. Kato et al., measured serum lignocaine level after giving bilateral TAP block with 40 ml (total) of 1% lignocaine and found them to be exceeding toxic levels, however we used 0.25% bupivacaine 30 ml(total) which is well within permissible limit and there was no evidence clinically that the dose of drug used had crossed the toxic blood levels. However measurement of blood levels requires further studies. No side effect of TAP block was found in this study. We obtained 100% success rate with TAP block in our study using landmark technique for posterior approach of block. Earlier McDonnell et al.,, also obtained good postoperative analgesic results using this landmark technique. Till now no study has been performed to compare the efficacy of landmark versus ultrasound technique for posterior approach of TAP block.
| Conclusion|| |
Both TAP block and TENS are effective and safe modality of analgesia following caesarean delivery. Both decrease the requirement of opioids and thus associated side effects. However TAP block appears to be better modality because of ease of application, the patient is more comfortable and it requires little or no monitoring.
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[Table 1], [Table 2], [Table 3]