Comparing Different Doses of Dexmedetomidine Combined with Ropivacaine for Ultrasound-Guided Supraclavicular Brachial Plexus Block in Upper Limb Surgeries - A Prospective Randomized Controlled Trial.

Background: Dexmedetomidine is used as an adjuvant to local anesthetic agents to provide prolonged analgesia in peripheral nerve blocks. This study aimed at determining the optimal dose of dexmedetomidine, which when combined with ropivacaine will produce a superior quality block in terms of extended pain-free period and reduced perioperative analgesic/opioid use, which in turn improves patient satisfaction. Objective: The objective of the study is to assess the duration of analgesia with two different doses (25 μg and 50 μg) of dexmedetomidine with ropivacaine in supraclavicular brachial plexus block. Subjects and
Methods: This prospective randomized controlled study included 50 patients undergoing upper limb surgeries under supraclavicular brachial plexus block randomly divided into two groups. Group D25 received 29 mL of 0.5% ropivacaine +25 μg dexmedetomidine diluted in 1 mL of normal saline (total 30 mL); Group D50 received 29 mL of 0.5% ropivacaine +50 μg dexmedetomidine diluted in 1 mL of normal saline (total 30 mL). Onset and duration of sensorimotor block, duration of analgesia, and time interval for the rescue analgesia and hemodynamic stability were observed.
Results: The mean onset of motor and sensory block was significantly higher in the D25 group (P = 0.001). The Visual Analog Scale pain scores and rescue analgesia consumption were significantly lower in the D50 group (P = 0.013, 0.001). The duration of analgesia was significantly higher in the D50 group (P = 0.001).
Conclusion: Dexmedetomidine 50 μg is an effective adjuvant dose to ropivacaine with insignificant hemodynamic changes with better duration of analgesia and lesser pain scores. Copyright:

INTRODUCTION

With the advent of ultrasound, regional anesthesia techniques have taken acceleration in its application and are being used as a choice of anesthesia by anesthetists with success rates up to 95%.[1] Regional anesthesia has the advantage that it can provide a good perioperative analgesia, safety, and better patient satisfaction. Supraclavicular block, also known as “spinal of the arm,” blocks the nerves at the base of the neck and gives a uniform distribution of the drug throughout the brachial plexus with high anesthetic efficacy.[2]

Dexmedetomidine, being an alpha-2 adrenoceptor agonist, has a sedative action by acting on the locus coeruleus. It has additional analgesic properties that reduce the anesthetic requirement and also perioperative sympatholytic and cardiovascular stabilizing effects.[345]

Although there is adequate literature to prove that dexmedetomidine extends the duration of analgesia provided by local anesthetics for nerve blocks,[678] the optimal dose range has always been debatable. As lesser doses do not provide effective analgesia and the higher doses are reported to cause bradycardia and hypotension,[9] it is warranted to identify the optimal dose of dexmedetomidine which will provide the desired effect and also not compromise on the hemodynamic status. Previous studies compared dexmedetomidine in the doses of 50 μg, 100 μg, and 150 μg.[1011] Therefore, this study was done to evaluate perioperative analgesic effects and hemodynamic changes with the lower doses of 25 μg and 50 μg.

SUBJECTS AND METHODS

This was a randomized, double-blinded study conducted for a period of 18 months in our institute after obtaining clearance from the Institutional Ethics Committee (IEC No. 2019/561, dated November 29, 2019). The trial was registered prospectively with Clinical Trial Registry of India (CTRI/2020/02/030963). Written and informed consent was obtained from all the patients for participating in the study, as well as for using their data for research and academic purposes. All the procedures were performed as per the guidelines laid down in the Declaration of Helsinki (1964).

Included patients were randomly divided into two groups by computer-generated list of random numbers. Both Group 1 and Group 2 consisted of 25 patients. Following the preanesthetic assessment, patients were admitted to the hospital the day before the surgery. After obtaining informed consent, the patients were shifted to the operation theater with a preoperative fasting status of 8 h.

In the operation theater, an intravenous (i.v.) access was secured and American Society of Anesthesiologists monitoring devices were attached which includes electrocardiograph, pulse oximetry (SpO2), and noninvasive blood pressure (BP), and the baseline parameters were recorded. Supplemental oxygen was provided through nasal cannula at 4 L.min−1 and the patients were sedated with i.v. midazolam 1 mg and fentanyl 1 μg.kg−1 before the block.

Under all aseptic precautions, supraclavicular brachial plexus block was performed by an anesthesiologist under ultrasound guidance with 30 mL of study drug. The anesthesiologist performing the procedure and the observer were both blinded to the drug administered to both groups. Motor and sensory components were evaluated every 3 min after giving the block until complete motor and sensory block of the upper limb has been achieved. Sensory block was assessed by the pinprick test using a blunt 26G needle in the dermatomes supplied by the ulnar, radial, median, and musculocutaneous nerves. This was charted using a three-point scale. Motor block for the mentioned nerves were evaluated by thumb adduction, thumb abduction, thumb opposition, and flexion at elbow, respectively, and this was also charted on a three-point scale.[121314]

The loss of sensation to pinprick and the complete paralysis of mentioned actions from the time of injection were considered commencement of sensory and motor blockade, respectively. Similarly, the time taken for reappearance of pinprick response from the onset of sensory blockade and achieving complete movement of wrist and fingers from the onset of motor blockade was considered the duration of sensory and motor blockade, respectively. The time duration after which the patients required their first dose of rescue analgesic from the time of sensory blockade was considered the duration of analgesia provided by the drugs.

Patients in whom a sensory and motor block of Grade 2 was achieved were included in the study, while those with Grade 0 or 1 sensory or motor block were excluded from the study and converted to general anesthesia.

Feedback regarding patient satisfaction was obtained at the end of the procedure and was graded as follows:[15]

“Excellent (4): No complaint from the patient

Good (3): Minor complaint with no need for supplemental analgesics

Moderate (2): Complaint that required supplemental analgesics

Unsuccessful (1): Patient required general anesthesia.”

Postoperative pain was assessed using Visual Analog Scale (VAS),[1617] and thereafter, pain was assessed regularly for every 1 h till the patient regains his motor power.

Rescue analgesia was provided with injection tramadol 50 mg if the VAS ≥4/10. Level of sedation was measured using the Ramsay sedation score.[1819] The occurrence of side effects such as bradycardia and hypotension was noted.

It was decided to manage bradycardia (heart rate [HR] ≤50 beats/min) with 0.6 mg i.v. bolus of atropine and hypotension (fall in BP by 20% from the baseline or an absolute mean aterial pressure [MAP] ≤60 mmHg) with i.v. ringer lactate or normal saline or increments of mephentermine 3 mg i.v., depending on the requirements. Total amount of rescue analgesic given and hemodynamic parameters were monitored regularly.

Statistical analysis was done using the SPSS(Statistical Package for the Social Sciences) Statistics for Windows, Version 25.0. (Armonk, NY: IBM Corp.). The Chi-square test and Fisher's exact test were used to calculate the significance. P < 0.05 was considered statistically significant.

RESULTS

A total of 50 patients satisfied the inclusion criteria and were enrolled in the study, among which 25 patients were in the D25 group and 25 patients were allocated to D50 group. The demographic characteristics of patients in both groups including age, body mass index (BMI), and type and duration of surgery were comparable.

The onset of sensory block was earlier in the D50 group when compared to the D25 group (11.47 ± 2.21 vs. 14.6 ± 2.42, P = 0.001). Similarly, the onset of motor block was also earlier in the D50 group when compared to the D25 group (18.92 ± 1.94 vs. 23.01 ± 3.00, P = 0.001) [Table 1].

Table 1

Distribution of onset of sensory and motor block with drug group among the study population

	Drug group	n	Mean±SD	P value by t-test
Onset of sensory block (min)	D25	25	14.60±2.42	0.001
	D50	25	11.47±2.21
Onset of motor block (min)	D25	25	23.01±3.00	0.001
	D50	25	18.92±1.94

SD=Standard deviation

Though the pain score at 4 h was more with 25 μg dexmedetomidine, the results were not statistically significant. Pain score at 8 h (2.40 vs. 1.64, P = 0.001), 12 h (2.60 vs. 1.84, P = 0.001), 20 h (3.00 vs. 2.36, P = 0.015). and 24 h (3.36 vs. 2.56, P = 0.013) was significantly higher in the D25 group [Figure 1].

Figure 1

Distribution of Visual Analog Scale pain score 4th hourly postsurgery with drug group among the study population

The mean duration of analgesia (652.32 ± 83.25 min in D25 vs. 960.00 ± 78.67 min in D50, P = 0.001) was significantly more in the D50 group [Figure 2], whereas the requirement for rescue analgesia at 16 h (1.71 ± 0.49 vs. 1.00 ± 0 doses, P = 0.008), 20 h (2.1 ± 0.32 vs. 1.00 ± 0 doses, P = 0.001), and 24 h (2.56 ± 0.62 vs. 2.00 ± 0 doses, P = 0.001) was more in the group that received 25 μg of dexmedetomidine [Table 2].

Figure 2

Distribution of duration of analgesia with drug group among the study population

Table 2

Distribution of rescue analgesia with drug group among the study population

Rescue analgesia (number of doses)	Drug group	n	Mean±SD	P value by t-test
16 h	D25	7	1.71±0.49	0.008
	D50	13	1.00±0.00
20 h	D25	10	2.10±0.32	0.001
	D50	12	1.00±0.00
24 h	D25	18	2.56±0.62	0.001
	D50	5	2.00±0.00

SD=Standard deviation

The hemodynamic parameters such as HR and BP were similar in both groups intraoperatively. Although there was a significant increase in the postoperative MAP in the D50 group, it was still well within normal limits.

DISCUSSION

Among the 50 patients included in our study, both groups had 25 patients who were randomly allocated to both groups. Adjuvant dose of 25 μg and 50 μg of dexmedetomidine was compared. Our study shows that there is a dose-dependent improvement in perioperative pain relief in the group that received 50 μg dexmedetomidine when given as an adjuvant to ropivacaine during supraclavicular nerve block in patients undergoing upper limb surgeries. The age, BMI, duration, and type of surgery were comparable in both groups.

The addition of dexmedetomidine to local anesthetics for peripheral nerve blocks has been time-tested to provide better perioperative analgesia in terms of earlier onset of sensory and motor blockade, prolongation of duration of this sensory and motor blockade, and duration of analgesia postoperatively without hemodynamic changes or significant adverse effects.[102021]

When the adjuvant action of fentanyl and dexmedetomidine with local anesthetics was compared, addition of dexmedetomidine was found to provide better and prolonged sensory and motor blockade when compared to fentanyl as an adjuvant.[22]

Studies comparing adjuvant dexmedetomidine doses of 50 μg and 100 μg with 0.5% levobupivacaine suggested that though the onset of sensory and motor blockade was earlier, the duration of analgesia was more (1033.6 ± 141.6 vs. 776.4 ± 138.6 min; P = 0.001) and need for rescue analgesia was lesser in the group that received 100 μg, and the incidence of hypotension and bradycardia was significantly higher in that group.[6] Therefore, we do not prefer adding higher doses of dexmedetomidine and decided to compare doses of 25 μg and 50 μg.

Very few studies have compared different doses of adjuvant dexmedetomidine.[1011] While comparing 1 μg.kg−1 and 2 μg.kg−1 doses of dexmedetomidine as adjuvant to levobupivacaine, Sinha et al. observed a significant decline in HR and MAP among the 2 μg.kg−1 dexmedetomidine group. They also observed a higher incidence of bradycardia and hypotension among the 2 μg.kg−1 dexmedetomidine group,[23] whereas in our study, there was no significant difference in the HR and MAP intraoperatively in both groups. Though postoperatively the MAP seemed to be significantly higher in the group that received 50 μg of dexmedetomidine, it was well within normal limits.

Studies comparing 1 μg.kg−1 with 2 μg.kg−1 of dexmedetomidine have shown similar time to onset of sensory (9.36 ± 1.114 min with 1 μg.kg−1vs. 8.32 ± 0.945 min with 2 μg.kg−1) and motor (14.40 ± 1.528 min with 1 μg.kg−1vs. 12.40 ± 1.21 min with 2 μg.kg−1) blockade.[14] The duration of sensory and motor blockade and duration of analgesia were also similar in both groups (P > 0.05). Although hemodynamic parameters were also similar between both groups (P > 0.05), three patients in the group that received 2 μg.kg−1 developed bradycardia requiring treatment with atropine. Therefore, the authors suggest using a lesser dose (1 μg.kg−1) of dexmedetomidine as adjuvant to 0.5% ropivacaine.[14] Since our study was done on adult patients, effects obtained with 50 μg dose of dexmedetomidine were similar to the effects obtained with 1 μg.kg−1 dose of dexmedetomidine in these studies.[14]

Thus, of the two different doses (25 μg and 50 μg) of dexmedetomidine, 50 μg can be preferred as an effective adjuvant dose to ropivacaine in upper limb surgeries for supraclavicular brachial plexus block with insignificant hemodynamic changes with better pain and sedation scores.

CONCLUSION

As there was no significant change in the hemodynamic parameters with 50 μg of dexmedetomidine, combined with the advantage of faster onset and prolonged duration of sensory and motor blockade and prolonged analgesia, we suggest administering dexmedetomidine at a dose of 50 μg as an adjuvant to 0.5% ropivacaine for ultrasound-guided supraclavicular brachial plexus block.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.