Dr. A. Ramya Parameswari from Coimbatore. I completed my undergraduation from Coimbatore Medical College. Then I joined Diploma in Anesthesiology at Madras Medical College, Chennai, followed by DNB in Anaesthesiology at Apollo Hospitals, Chennai. I then worked at Sri Ramakrishna Hospital, Coimbatore, for a year. Later I moved to UK for a few years. Now, I work at Sri Ramakrishna Hospital, a 750-bedded multispecialty hospital in Coimbatore. My areas of interest are regional anaesthesia and ultrasound-guided nerve blocks.
Background: Increasing rate of Caesarean sections and inadequate pain relief following Caesarean section is seen in almost all parts of the world. Transversus abdominis plane block is gaining popularity as a part of multimodal analgesia for post-operative pain relief following abdominal surgeries.
Aim: To compare bupivacaine and bupivacaine with dexmedetomidine in transversus abdominis plane block for pain relief after Caesarean section.
Method: American Society of Anaesthesiologists I and II parturients with no comorbidities admitted for elective Caesarean section were included in the study. Thirty-five patients were in each study (with dex) and control (without dex) groups. At the end of Caesarean section done under spinal anaesthesia, transversus abdominis plane block was done bilaterally under ultrasound guidance using in-plane technique of needle insertion. 20 ml of 0.25% bupivacaine with 0.5 mcg/kg of dexmedetomidine in the study group and 20 ml of 0.25% bupivacaine in the control group were injected in the neurovascular plane.
Results: Eight patients from the study group and 15 from the control group were given opioids as rescue analgesia. The average time at which rescue analgesia was first sought was 14.25 and 7.73 h in the study and control groups, respectively. The P value of this difference was 0.0136 and was found to be statistically significant.
Conclusion: The addition of dexmedetomidine to bupivacaine in TAP block prolonged the duration of time at which first dose of rescue analgesia was sought and also reduced the total dose of opioid requirement in the first 24-h postCaesarean section.
Keywords : Bupivacaine, Dexmedetomidine, TAP block, Post-operative analgesia
Until 2010, Caesarean—or C-sections—were limited to 8.5% of all deliveries in the country, just under the recommended level of 10–15%, according to the World Health Organization [1] report.
But in the last decade or so, the numbers have escalated in many parts of India—reaching as high as 41% of deliveries in Kerala, and 58% in Tamil Nadu, according to a report by the ICMR School of Public Health [2]. Despite better understanding of pathophysiology of post-operative pain and introduction of newer analgesics and delivery techniques, approximately 80% of patients have acute post-operative pain and among them 75% have moderate to severe pain [3].
Women, following Caesarean delivery, have even more compelling reasons to receive optimal post-operative pain relief, for improved maternal and neonatal well-being. Also adequate pain relief helps patient to ambulate early and prevent any thrombotic incidents [4].
In an effort to achieve the target recommended by the RCoA, this study was done to evaluate the efficacy of transversus abdominis plane block with bupivacaine 0.25% versus bupivacaine 0.25% and dexmedetomidine 0.5 mcg/ kg under ultrasound guidance for post-operative pain relief following lower segment caesarean section.
Dexmedetomidine, an imidazole compound, is the pharmacologically active dextroisomer of medetomidine that displays specific and selective a2-adrenoceptor agonist activity and causes sedation, analgesia without any delirium, or respiratory depression [5, 6]. The mechanism of action is unique and differs from those of currently used agents, including clonidine. Activation of the receptors in the brain and spinal cord by dexmedetomidine inhibits neuronal firing, causing hypotension, bradycardia, sedation, and analgesia.
The transversus abdominis plane block was first described in 2001 by Rafi, who performed the traditional landmark technique, through the lumbar triangle of Petit.
In this, the drug that is injected into the neurovascular
plane between the internal oblique and transverses abdominis
muscle anaesthetizes the nerves of the anterior
abdominal wall (T6–T11).
In a recent meta-analysis by Siddiqui, TAP block reduces
the dose of opioids used in the post-operative period, prolongs
the duration of analgesia, and provides excellent pain
relief, while decreasing opioid-related side effects such as
sedation and post-operative nausea and vomiting [7].
These results were noted in both abdominal and
gynaecologic procedures [8, 9].
The use of ultrasound helps us to perform the block more precisely [10].
To study the efficacy of bupivacaine 0.25% with dexmedetomidine and that of bupivacaine 0.25% alone in transversus abdominis plane (TAP) block for post-operative analgesia in patients undergoing elective Caesarean section.
Group 1: bupivacaine 0.25% ? Dexmedetomidine 0.5 mcg/kg
Group 2: bupivacaine 0.25%
Prospective Randomized Interventional Single-blind study.
Primary Outcome
The time for first rescue analgesia after the TAP block
Secondary Outcome Measures
Total dose of rescue analgesia (tramadol) required in 24 h post-operatively.
Adverse effects like pruritus, nausea and vomiting, hypotension, bradycardia, and sedation.
The study was conducted at Sri Ramakrishna Hospital, (Tertiary Caresample Hospital), Coimbatore, between March and September 2016 on parturients of American Society of Anaesthesiologists I and II and above 18 years of age, who were admitted for safe confinement.
Exclusion criteria used in the study were patient refusal, allergy to study medications, localized infection over injection point, patients with significant coagulopathies and with contraindications to regional anaesthesia, patients with heart diseases, altered renal or liver functions, psychological disorders, patients with pregnancy-induced hypertension and gestational diabetes, chronic use of pain medications, and BMI[35 or weight \50 kg.
Sample size (70) was determined prospectively using datafrom previous studies [11].
Detailed Description
Institutional ethical committee clearance was obtained.
Written informed consent was obtained from all patients. Routine nil per oral guidelines were followed. Any sedative or analgesic medications other than that used in the study were avoided in the 24 h before and after the Caesarean section. Patients who satisfied the inclusion criteria were allotted to either group by the sealed envelope technique. Preoperatively, the patient’s blood pressure, heart rate, and oxygen saturation were recorded. All patients were preloaded with 1 litre of crystalloids (Tables 1, 2, 3, 4).
Subarachnoid block with 27G Quincke’s spinal needle in the sitting position with bupivacaine heavy 0.5% 10 mg and 20 micrograms of fentanyl was given to achieve a block level of T6 for the Caesarean section. The patient’s heart rate, NIBP, oxygen saturation were recorded every 5 min during the intraoperative period (Figs. 1, 2).
At the end of the Caesarean section, the operative wound was covered with a sterile pad. TAP block was performed under strict aseptic precautions after cleaning the site of injection with antiseptic solution. Bilateral TAP block was performed under ultrasound guidance with GE logiq e machine using high-frequency probe and in-plane technique of needle insertion. The probe was placed above and lateral to the skin incision and its position adjusted until the three layers of the muscles were clearly visible. 21G spinal needle with 100-cm extension tube was used to inject the drug. Saline was injected under ultrasound guidance to confirm the correct placement of the needle in the neurovascular plane.
Dexmedetomidine 0.5 micrograms/kg (Dexem) with 0.25% bupivacaine (Sensorcaine) to a total volume of 40 ml (20 ml each side) was used for the TAP block.
0.25% bupivacaine 40 ml (20 ml each side).
At the completion of the TAP block, sterile dressing was applied to the operative wound and patient blood pressure, heart rate and VAS were recorded. Average duration of the surgery was between 1 and 1.5 h.
None of the patients in either group had any complications intraoperatively.
Patient was then transferred to the recovery room, and baseline vital parameters were recorded. A trained postoperative nurse who is unaware of the drug injected was in charge of monitoring and recording the vital parameters on the proforma. She was unaware of the group to which the patient belonged.
She was instructed to monitor the blood pressure, heart rate, SpO2, VAS score at rest and movement, sedation score, PONV score. She was advised to give Inj. Ephedrine 6 mg i.v. stat if the systolic blood pressure \90 mmHg, Inj. Atropine 0.6 mg i.v. when the heart rate was less than 45/min stat and then inform the concerned anaesthetist immediately.
When the patient had a sedation score of C3, supplement oxygen via facemask@10 l/min and alert the anaesthesiologist.
Patients received 1 g paracetamol intravenous immediately in the recovery room and every 8 h thereafter. Rescue analgesia was provided with 50 mg of intravenous tramadol and additional doses of 50 mg every 6 h thereafter till VAS was less than 3 or was precluded by adverse effects such as nausea and/or vomiting, respiratory depression (SpO2 \92%, ventilatory frequency rate\10), or occurrence of deep sedation.
In the first 24 h post-operatively, mean arterial pressure (MAP), heart rate, VAS (at rest and on coughing), sedation score (RS), nausea and vomiting score were recorded on admission to recovery and at 1,2,4, 8, 12, 18, and 24 h post-operatively by a post-operative care nurse who was unaware of the group to which the patient belonged.
The time following the TAP block when rescue analgesia was first sought, total dose of tramadol required in the first 24 h post-operatively, and its adverse effects like pruritus, nausea and vomiting were recorded. Visual analogue scale (where 0 = no pain and 10 = worst imaginable pain) was used to assess post-operative pain during rest and on coughing.
Nausea and vomiting was recorded on a 4-point scale (0 = none, 1 = nausea, 2 = retching, 3 = vomiting). IV ondansetron 4 mg was offered for any patient with a score C1.
A sedation score on a 6-point scale was used.
The sample size was calculated from data based on the previous similar studies [11].
Thirty-five patients received TAP block with 0.25% bupivacaine only (control), and 35 patients received TAP block with 0.25% bupivacaine and 0.5 mcg/kg dexmedetomidine (study). The results were analysed using the PrismPad Graph software version 7.02.
The primary outcome was to calculate the time at which
the first dose of opioid was required. Total dose of opioid
used was calculated as the secondary outcome.
P value of\0.05 was considered as statistically
significant.
Results
The groups were comparable based on demographic data. Thirty-five patients were included in each study and control group.
Only 8 patients from the study group and 15 patients from the control group required any opioids. The average time at which the first dose of opioid was requested was 14.25 h in the study group and 7.73 h in the control group. The P value of this difference was found to be 0.0136.
The pain score was recorded at 4, 8, 12, 18, and 24 h after LSCS at rest and during movement. The time and dose of analgesic were also recorded.
The mean and median pain scores were calculated, and the P value was recorded. The difference between the pain scores of the two groups was found to be statistically significant.
The median pain score of the two groups was compared using the Mood’s median test. The Chi-square statistic is 3.9683. The P value is 0.046366. The result is significant at a P value\0.05.
The mean dose of tramadol required was 11.43 mg in the study group and 32.86 mg in the control group over the first 24 h, and the P value was found to be\0.001. This difference is statistically significant.
None of the patients in either group had nausea or vomiting. The patients who received dexmedetomidine had a sedation score of 3 versus the control group who had a score of 2.
With the introduction of the TAP block in 2001 by Rafi, it has been widely used for pain relief following lower abdominal surgeries. Ultrasound guidance has further refined the technique and increased the success rate. Several studies done by Lee et al. [12] and Onishi et al. [13] have concluded that TAP block is superior to or comparable to neuraxial opioids for the control of post-operative pain following Caesarean sections. This reduces the need for opioids and hence their side effects in the post-operative period. Mishriky et al. [14] have done a meta-analysis of RCTs on TAP block for pain relief after Caesarean section and concluded that TAP block produces pain relief comparable to intrathecal morphine without the side effects of morphine. Meta-analysis done by Nanze Yu et al. [15] has proved the superiority of TAP block over local wound infiltration for pain relief following lower abdominal surgeries. This supports Jankovic’s [16] idea of calling TAP block, the holy grail of anaesthesia for lower abdomen.
Almarakhi et al. [11] study has proved that the addition of dexmedetomidine to local anaesthetics in TAP block provided better pain relief than local anaesthetics alone following abdominal hysterectomies.
Clonidine, an alpha 2 agonist, also prolongs post-operative analgesia when added to bupivacaine in TAP blocks [17].
In a study by Toshniwal et al. [18], the use of ultrasound to perform the TAP block has increased the success rate even in obese patients.
Tan et al. [19] performed TAP block under ultrasound guidance after Caesarean section and concluded that TAP block not only reduced the morphine consumption but also improved patient satisfaction.
The study by Kanazi [21], Loane [21], and Costello [22]
showed that subarachnoid morphine was superior to TAP
block for post-operative pain relief following Caesarean section
at the expense of increased opioid-related side effects.
However, as we are moving away from injecting any adjuvant
in the intrathecal space, TAP block would still score higher.
A meta-analysis by Abdallah [23] compared the posterior
versus the lateral approach of performing the TAP
block and concluded that the posterior approach may be
superior to the lateral approach. The use of ultrasound has
overcome this, as the injection and spread of the drug in the
neurovascular plane can be clearly visualized.
Similar to our finding, many investigators reported that
the addition of dexmedetomidine to different types of LA
agents in various types of peripheral nerve blocks resulted
in prolongation of analgesic effect [24–28].
Also the use of ultrasound decreases the dose of local anaesthetic used in various peripheral nerve blocks due to the injection of the drug in close proximity to the nerves [29].
TAP block had a significant effect in the control of postoperative pain following Caesarean section. It reduced the opioid requirement in both the study and control groups. It shows that the addition of dexmedetomidine to local anaesthetics further reduced the need for rescue analgesia with opioids. It also significantly prolonged the duration of time at which the first dose of opioid was given.
Our study further emphasizes that the addition of dexmedetomidine to local anaesthetics in TAP block decreases the opioid requirement and prolongs the duration of time for the first dose of rescue analgesia with opioids. Two patients in the study group had bradycardia (HR 45–60) in the recovery room within 15 min of TAP block administration and were given Inj. Atropine 0.6 mg. However, they were hemodynamically stable. No other side effects were noted. Newborns were monitored for the first 24 h after birth for any respiratory depression and bradycardia. None of them required admission to the NICU.
The limitation of this study is plasma levels of dexmedetomidine were not monitored. Also the time at which the TAP block began to work and the time at which the sensory effect of the intrathecal block began to wear off could not be clearly differentiated.
Conflict of interest: Authors declare that they have no conflict of interest.
Ethical approval: Institutional ethical committee clearance was obtained. None of the patients in the study group had any adverse effect due to the addition of dexmedetomidine.
