The addition of dexmedetomidine to bupivacaine in Transversus Abdominis Plane (TAP) blockade reduced postoperative pain scores and morphine consumption, in addition to increasing satisfaction in patients undergoing lower abdominal surgery. Dexmedetomidine had no effect on nausea and vomiting scores and the need for antiemetic. 

Various surgeries such as inguinal hernioplasty and open appendectomy lead to mild to severe postoperative pain. In many cases, this postoperative pain can be chronic and may cause undesirable events. Among patients who undergo the hernia repair, about 54% patients are known to suffer from pain after the procedure. The transverse abdominis plane, one of the peripheral nerve blocks is known to significantly control the pain after the hernioplasty. However, coadministration of local anesthesia provides synergistic effect and prolonged duration of blockade. Dexmedetomidine is a selective α -2-adrenergic agonist with analgesic and sedative properties. When administered as a perineural adjuvant, dexmedetomidine reduces the initial blocking time while prolonging the duration of sensory-motor blockade.

Rationale behind the research:

Postoperative pain is the chronic condition causing discomfort and prolonged immobility in patients. None of the published study provide the satisfactory results to patients.

Therefore, the present study by Aksu R et. al., evaluated the effect of bupivacaine and dexmedetomidine added to bupivacaine for TAP blockade in pain control and estimated the patient satisfaction after the lower abdominal surgery.

Objective:

To evaluate the effect of bupivacaine and dexmedetomidine added to bupivacaine used in TAP block on postoperative pain and patient satisfaction in patients undergoing lower abdominal surgery.

Study outcome measures:

• Primary endpoint: To evaluate the use of morphine in the postoperative period

• Secondary endpoint: Patient satisfaction through pain scores assessed with Visual Analogue Scale (VAS) in the postoperative period of 24 h, hospitalization period, nausea, vomiting and antiemetic

• Heart rate (HR) (bpm):

During the postoperative period, HR continued to increase in the BD Group at zero and 24 h compared to Group C and at 120 h, 6 h and 12 h compared to groups C and B (p<0.05). Intergroup HR assessment showed a decrease from baseline HR at 10, 30, 45 and 60 minutes of operation in Group B and at each measurement period, excluding the postoperative period of 24 h in the BD group (p<0.05). However, 0.5 mg of atropine was required because the HR of two patients was <50 bpm. There was no difference in relation to the baseline values of Group C (p>0.05) (Figure 1).

Figure 1: Heart rate (HR)

• Mean blood pressure (MBP) (mmHg):

Compared with Group C, there was a decrease in the normal clinical blood pressure level at the 10th minute of Group B operation; at the 30th, 45th and 60th postoperative hours and at the 6th postoperative hour in the BD Group and in the 12th hour in comparison to the Group B (p>0.05) (Figure 2).

Figure 2: Mean blood pressure (MAP) (mmHg)

• VAS scores in the postoperative period:

Although a statistically significant reduction in VAS score was observed only in the BD group compared to the C group in the postoperative period (0 min), reduction in groups B and BD between 120min to 8 h in post-was statistically significant (p<0.05). The reduction in the BD group between 10 to 24 h postoperatively was statistically significant when compared with groups B and C (p<0.05) (Figure 3).

Figure 3: VAS scores in the postoperative period

• The consumption of morphine in the BD group was low at all times postoperatively. While, the consumption of morphine was lower in Group B than in Group C at hours 6, 12, 18 and 24 (p<0.001)
• There was no significant difference between the groups regarding the number of patients presented with nausea, vomiting, need for antiemetic or additional administration of analgesic (p<0.05)
• There was a significant increase in patient satisfaction scores in groups B and BD compared to Group C and also in Group BD when compared to groups B and C (p<0.001)
  

The present study demonstrated that the administration of TAP block after induction of anesthesia reduced the VAS score in comparison with the control group, while minimizing postoperative morphine consumption.

To prolong the duration of pain relief with TAP block, the blockade should be administered soon after the induction of anesthesia and shortly before the surgical incision. Bharti et al applied the TAP block at the end of the surgery and reported that the blockade did not extend the time to the first need for analgesia compared to the control group; however, the authors reported a reduction in total morphine consumption in the second postoperative hour. Niraj et al administered a unilateral TAP block with 20 mL of 0.5% bupivacaine in open appendectomy. In the control group, the mean 24-hour morphine intake was 50mg, compared with 28mg in the group that received the TAP blockade. Cho et al reported that administration of the TAP block with 20 mL of 0.5% bupivacaine for open appendectomy reduces intraoperative fentanyl consumption as compared to the control group. Besides, TAP blockade with 20 mL of 0.5% levobupivacaine provided 12 h of postoperative analgesia, but the effect was not continuous till 24 h postoperatively. However, this result may be due to the limited number of patients.

The number of studies reported that the addition of dexmedetomidine to local anesthesia prolonged the local anesthetic action time and reduced the need for anesthetics. According to Agarwal et al., the analgesia lasted for up to 8 h with the addition of 100μg of dexmedetomidine to bupivacaine for the supraclavicular block. Similarly, the study conducted by Almarakbi et al added dexmedetomidine to TAP blockade and showed significantly longer analgesic action in the dexmedetomidine group and lowered the morphine consumption. In our study, we administered the TAP block with 20mL of 0.5% bupivacaine and 100μg of dexmedetomidine + bupivacaine for the open appendectomy and inguinal hernia, and 24 h morphine consumption in the control, bupivacaine, and bupivacaine + dexmedetomidine groups was of 28.8mg, 17.5mg, and 8.2mg, respectively. The use of morphine in the period of 2-24 h in both TAP groups was significantly lower than in the control group, but lower consumption of morphine was observed in the bupivacaine group + dexmedetomidine at all times measured at 24 h, including the first 2 h, compared to the control and bupivacaine groups. In general, VAS measurement is used for postoperative pain assessment.

The present study suggested that there was a significant decrease in the BD group at 0-24 h when compared to the control group and at 10-24 h when compared with the B group. In the BD group, there was a decrease in 2-8 h in comparison with the control group. While in the TAP block administration of bupivacaine alone provided a reduction of the VAS scores for 8 h, the addition of dexmedetomidine prolonged this effect up to 24 h. The VAS score was lower postoperatively (0 min) in the group with dexmedetomidine addition. Therefore, it can be considered that dexmedetomidine provides a faster onset of sensory block and increases the efficiency of the blockade.

The satisfaction scores in the group receiving the addition of bupivacaine-dexmedetomidine were higher than in other two groups.