A Study to Evaluate the Efficacy of Dexamethasone as an Adjuvant in Ultrasound-Guided Bilateral Superficial Cervical Plexus Block using 0.25% Bupivacaine in Patients Undergoing Thyroid Surgeries under Entropy-Guided General Anesthesia.

Context: Ultrasound-guided bilateral superficial cervical plexus block (BSCPB) is a technique described for thyroid surgeries for postoperative analgesia as the surgery can cause severe pain and discomfort. Perineural dexamethasone is known to prolong analgesic duration and reduce postoperative nausea/vomiting. Aims: To assess the efficacy of dexamethasone as an adjuvant to BSCPB with 0.25% bupivacaine on isoflurane consumption, intraoperative hemodynamic parameters, and postoperative analgesia in patients undergoing thyroid surgeries under general anesthesia. Settings and Design: This was a randomized control trial. Subjects and
Methods: Eighty patients were randomized to two equal groups using random number table into Group A with BSCPB receiving 20 mL of 0.25% bupivacaine and Group B with BSCPB receiving 19 mL of 0.25% bupivacaine + injection dexamethasone 4 mg in the preinduction period. Hemodynamic parameters, isoflurane consumption, postoperative visual analog scale (VAS) score, and antiemetic effect over 24 h were compared between two groups. Statistical Analysis Used: Microsoft excel data sheet, Chi-square test, and independent t-test were used for statistical analysis.
Results: The intraoperative hemodynamic parameters were comparable between the two groups. There was a significant difference in mean VAS score between two groups from 6 h to 20 h postoperatively. The time of rescue analgesic in Group A was 7.09 ± 1.04 min and Group was 13.19 ± 1.46 min with P < 0.0001. In Group A, 40% had nausea and 35% had vomiting, and in Group B, 7.5% had nausea and 5% had vomiting. Conclusions: Preinduction ultrasound-guided BSCPB with bupivacaine and dexamethasone provides longer duration of postoperative analgesia and lesser nausea and vomiting compared to bupivacaine alone. Copyright:

INTRODUCTION

Thyroidectomy is the most common endocrine surgical procedure being carried out throughout the world.[1] General anesthesia is the technique of choice for thyroid surgery. In addition to pain, discomfort while swallowing, a burning sensation in the throat, and nausea and vomiting can be caused by surgery or general anesthesia.[2] Thyroid surgery may cause severe postoperative pain and discomfort for patients. Postoperative pain management after thyroid surgery has also gained more importance and attention because thyroid surgery is recently being performed on a day case basis.[3]

Nonsteroidal anti-inflammatory drugs may not produce effective pain relief and at the same time may increase the risk of postoperative bleeding, with the thyroid being a highly vascular organ. On the other hand, opioid analgesics may increase the risk of postoperative nausea and vomiting or produce postoperative respiratory depression.[4]

Locoregional anesthesia, such as local anesthetic wound infiltration, bilateral superficial cervical plexus block (BSCPB), and bilateral combined superficial cervical plexus block (SCPB) and deep cervical plexus block, can potentially reduce postoperative pain in patients who undergo thyroid operations.[567] Ultrasound-guided block remains as a reliable tool for performing a cervical plexus block, provides faster onset and longer duration of the block, reduces the performance time, and reduces the complications in addition to reduced local anesthesia requirements.[8]

Dexamethasone is a systemic glucocorticoid commonly used to reduce postoperative nausea/vomiting pain and to improve the quality of recovery after surgery.[9] Recently, several studies have examined the use of perineural dexamethasone to prolong analgesic duration of peripheral nerve blocks, which is thought to be mediated by attenuating the release of inflammatory mediators, reducing ectopic neuronal discharge, and inhibiting potassium channel-mediated discharge of nociceptive C-fibers.[10]

The main objective of the current investigation was to evaluate the effect of perineural dexamethasone on analgesic outcomes along with BSCPB, intraoperative inhalation anesthetics required, antiemetic effect, postoperative pain visual analog scale (VAS) scores, and postoperative analgesic requirement.

SUBJECTS AND METHODS

This was a prospective, randomized double blinded study conducted after obtaining Institutional Ethical Committee Clearance (BMCRI/PS/298/2020-21 dated 6th February 2021) and was registered prospectively in the Clinical Trial Registry India (CTRI/2021/04/032612) and all the procedures followed the guidelines laid down in the Declaration of Helsinki. Eighty patients (age, 20–60 years) of the American Society of Anesthesiologists PS Classes I and II who were undergoing elective thyroid surgery under general anesthesia were randomly allocated into two groups of 40 each using a computer-generated randomization sequence (www.random.org). Group A received BSCPB with 20 mL 0.25% bupivacaine, and group B received BSCPB with 19 mL 0.25% Bupivacaine and dexamethasone 4 mg [Figure 1]. Patient not willing to give informed consent, history of allergy to bupivacaine, diagnosed with vocal cord palsy by preoperative indirect laryngoscopy, thyroid mass extending retrosternally, any gross compression, or deviation of trachea were excluded. Patients scheduled for extensive surgery such as radical neck dissection, electrolyte abnormalities, hepatic or renal insufficiency, coagulation disorder, hypertension, cardiac disorder, pregnant women/ breastfeeding mothers were alsoexcluded from the study.

Figure 1

CONSORT flow diagram. Group A: BSCPB with Bupivacaine, Group B: BSCPB with Dexamethasone

Preanesthetic evaluation was done and patients were educated about VAS. Patients were nil per oral for 8 hours before surgery. Patients were premedicated the night before surgery with tablet Ranitidine 150 mg HS and Tablet Alprazolam 0.5 mg HS.

Intravenous (i.v.) access was obtained using 18G cannula, and Ringer's lactate was connected. Monitors such as electrocardiography, SpO2, noninvasive blood pressure, and entropy were connected and basal values were recorded.

Anesthesia was administered by the anesthesiologist who was not involved in postoperative monitoring of the patient. Patients were not aware about their group allocation. The patient was premedicated with glycopyrrolate 0.2 mg (i.v.), midazolam 0.2 mg.kg−1 (i.v.), and fentanyl 2 mg.kg−1 (i.v.).

Using the computer-generated random list, we allocated patients randomly to group A or group B. Group A received BSCPB with 20 mL 0.25% bupivacaine (10 mL on each side) after premedication. Patients in group B received BSCPB with 19 mL 0.25% Bupivacaine and dexamethasone 4 mg. The anesthesiologist administering the block was familiar with the technique and monitored patients intraoperatively.

Regional anesthesia tray with sterile towels, gloves, and gauze packs, as well as two 10 mL syringes containing the anesthetic mixture was arranged. A 2.5 inch, 23 gauge needle was attached to an extension tube. Under aseptic precautions, block was performed under local anesthesia with the patient lying supine and head turned to the contralateral side. The SonoSite M Turbo Linear probe (6–15 Hz) was placed transversely over the lateral aspect of the patient's neck, after skin sterilization, at the middle of the posterior edge of the sternocleidomastoid (SCM). The probe was displaced backward to identify and visualize the tapering posterior edge of the muscle in the middle of the view captured on the screen. The plexus appeared as nodules that are hypoechoic below the prevertebral fascia and immediately above the interscalene groove. The needle was then introduced from the posterior aspect, with an in plane technique, through the skin and platysma adjacent to the plexus, deep to SCM, under the prevertebral fascia and above the interscalene groove. After negative aspiration, 10 mL of local anesthetic was deposited on either side of the plane, just behind the posterior border of SCM. The local anesthetic spread was witnessed in the right plane. The same procedure was performed on the contralateral side also.

After administration of the block, patients were preoxygenated with 100% oxygen for 3 min and then induced with an intravenous injection of propofol 20 mg in 30 s increments until response entropy fell below 60. Mask ventilation was confirmed, and intubation was facilitated with an intravenous injection of 0.1 mg.kg-1 vecuronium. Proper positioning of the endotracheal tube was confirmed, the agent gas monitoring line was connected. Anesthesia was maintained with 50% nitrous oxide and oxygen as well as 0.2%–1% Isoflurane to maintain entropy values of 40–60.

Ventilation (tidal volume of 6–8 mL.kg−1) to maintain the end tidal CO2 between 35 and 40 mmHg. Intermittent doses of vecuronium bromide (0.01 mg.kg−1) (i.v.) was given.

Hemodynamic parameters (heart rate, systolic blood pressure, diastolic blood pressure, and mean arterial pressure), SpO2 and response and state entropy were monitored continuously and recorded at 5 min intervals until the end of surgery. Volume of isoflurane consumed was recorded at 30 min intervals (Datex Ohmeda Avance). An increase in heart rate or mean arterial pressure of more than 25% of basal (or systolic blood pressure >150 mmHg) was considered tachycardia and hypertension, respectively and Fentanyl (1 μg.kg-1) boluses were administered intravenously. Isoflurane and nitrous oxide were discontinued at the end of surgery. The neuromuscular blocking agent was reversed with an intravenous injection of 0.5 mg.kg-1 neostigmine and 10 μg.kg-1 glycopyrrolate, and the patient was extubated after complete recovery as assessed by clinical observation and neuromuscular monitoring. Postoperative pain was assessed using the VAS, with 0 representing no pain and 10 representing the worst pain. Hemodynamic parameters and VAS scores for pain were recorded at hourly intervals for the first 8 h and then every 4th hourly until the patient received rescue analgesia. Patients received 1 g paracetamol intravenously as a rescue analgesic once the VAS score was > 4. The duration of analgesia was recorded from the time of block administration to the first request for analgesia during the postoperative period. Even after 20 min of paracetamol infusion, if pain persists, tramadol 2 mg.kg-1 (i.v.) was given. Side effects such as nausea, vomiting, perioral numbness, headache, blurring of vision, and tachycardia were all monitored.

RESULTS

A total of 80 patients were enrolled into the study. There were no dropouts. Females were more in number compared to male patients among the two groups. Demographic parameters such as age, height, and weight were comparable between the two groups. There was no significant difference in mean Heart Rate, Systolic Blood Pressure, Diastolic Blood Pressure, mean arterial Pressure, mean isoflurane consumption, and mean entropy values between two groups. The trends of the mean Visual analog score between the two groups is shown in Figure 2. There was significant difference in mean VAS Score between two groups from 6 h to 20 h post op. Mean VAS was lower in Group B compared to Group A at these intervals [Table 1]. [Figure 3] depicts a bar diagram comparing the mean time of rescue analgesic between the two groups in the post-operative period. The mean time of rescue analgesic was much longer in group B than in group A [Table 2]. Side effects such as nausea, vomiting was compared between the two groups [Figure 4]. Incidence of postoperative nausea and vomiting was lesser in Group B compared to Group A [Table 3].

Figure 2

Line diagram showing mean visual analog scale comparison between two groups at different intervals of time in postoperative period

Table 1

Visual analog scale scores comparison between two groups at different time intervals

VAS score	Group				P
	Group A		Group B
	Count	Mean±SD	Count	Mean±SD
5 min	40	1.00±0.00	40	1.00±0.00	-
30 min	40	1.00±0.00	40	1.00±0.00	-
1 h	40	1.00±0.00	40	1.00±0.00	-
2 h	40	1.25±0.34	40	1.41±0.44	0.067
3 h	40	1.99±0.45	40	2.03±0.63	0.759
4 h	40	2.79±0.58	40	2.56±0.70	0.120
6 h	40	3.66±0.69	40	3.13±0.73	<0.001
8 h	40	4.88±0.91	40	3.75±0.79	<0.001
12 h	40	6.10±0.95	40	4.65±0.93	<0.001
16 h	40	7.21±0.84	40	5.91±0.97	<0.001
20 h	40	8.21±0.63	40	7.77±0.83	0.010
24 h	40	9.95±0.32	40	10.00±0.00	0.320

VAS=Visual analog scale, SD=Standard deviation

Figure 3

Bar diagram showing mean time of rescue analgesic comparison between two groups in the postoperative period

Table 2

Mean time of rescue analgesic

Mean±SD		P
Group A	Group B
7.09±1.04	13.19±1.46	<0.001

SD=Standard deviation

Figure 4

Bar diagram showing side effects and nausea distribution between two groups

Table 3

Side effects - Nausea distribution between two groups

Side effects	Group A	Group B
Nil	10	35
Nausea	16	3
Vomiting	14	2

Statistical analysis

The Categorical data were represented in the form of frequencies and proportions. Chi square test or was used as test of significance for qualitative data. The Continuous data were represented as mean and standard deviation, Independent t test was used as test of significance to identify the mean difference between two quantitative variables. P (probability that the result is true) < 0.05 was considered as statistically significant after assuming all the rules of statistical tests.

DISCUSSION

Thyroid surgery is a quite painful procedure performed in a sensitive skin area of the human body. Unless pain is treated adequately, thyroid surgery may cause severe postoperative pain and discomfort for the patients. Opioids used to treat postoperative pain cause potential side effects such as nausea and vomiting that contributes to patient discomfort and even delayed discharge from the hospital.

Regional techniques may help alleviate postoperative pain and reduce systemic analgesic requirement. Cervical plexus block and wound infiltration techniques are the main regional techniques that can be performed to provide postoperative analgesia following thyroid surgery. The study of Suh et al. has shown that SCPB alone is a more effective technique than combining SCPB and deep cervical plexus block.[11]

Ultrasound guidance during regional anesthesia practices has been a revolutionary advancement to improve success and safety of regional anesthesia. The main advantages of ultrasound-guided SCPB include provide real-time visualization of anatomical structures, reduce volumes of local anesthetics, and avoid inadvertent damage or accidental puncture of vessels. Owing to its feasibility and efficacy, ultrasound-guided SCPB is a well-established technique for providing regional anesthesia during thyroidectomy.

Local anesthetics such as bupivacaine, ropivacaine, and levobupivacaine and adjuvants such as clonidine, dexamethasone, and dexmedetomidine have been administered as SCPB.

In the present study, we analyzed the efficacy of dexamethasone as adjuvant in ultrasound-guided SCPB using bupivacaine in terms of isoflurane consumption and hemodynamic parameters in patients undergoing thyroid surgeries under entropy-guided general anesthesia. It was observed that there was no significant decrease in isoflurane consumption, hemodynamic parameters, and the entropy values among the two groups.

Preoperative administration of block increased the duration of postoperative analgesia among the patients. We found that there was significant prolongation of duration of analgesia postoperatively in the first 24 h in patients receiving bupivacaine and dexamethasone as adjuvant. There were no significant differences in the hemodynamic parameters during postoperative period.

Utilizing electroencephalography-based monitors, such as entropy, to judge the depth of general anesthesia and the level of hypnosis during surgery results in reduced isoflurane consumption. Previous studies used an automated closed circuit loop to deliver sevoflurane and state entropy to monitor the depth of anesthesia. We used response entropy, which depicts not only the state of anesthesia but also the state of frontalis activity, representing a reflex response to pain in the event of inadequate analgesia. Response entropy was chosen because it represents not only the state of the brain but also the degree of reflex suppression, which is a component of balanced anesthesia. We believe that entropy monitoring helped us maintain adequate anesthesia depth in the present study, as none of our patients complained of recalling any intraoperative event when assessed 24 h after surgery. The volume of isoflurane consumed was calculated and displayed by an inbuilt algorithm fed into the anesthesia workstation software.

Gürkan et al. evaluated analgesic effect of ultrasound-guided SCPB in patients undergoing thyroid surgery in the postoperative period among 50 patients in a randomized and prospective manner patients allocated to either SCPB using 10 mL 0.25% bupivacaine or control group using 10 mL normal saline for each side. Postoperative morphine consumption was lower in SCPB group compared to control group at postoperative period.[12] In our study, we used the same concentration and volume of the drug on each side and found a reduction in postoperative analgesic requirement.

Kannan et al. performed a prospective randomized study among 50 patients to study the effects of BSCPB on sevoflurane consumption during thyroid surgery under entropy-guided general anesthesia. Preinduction with BSCPB during thyroid surgery significantly reduced sevoflurane consumption and increased the duration of postoperative analgesia.[13] We compared the isoflurane consumption among the two groups in our study and found no significant decrease in isoflurane consumption among both groups.

Steffen et al. did a meta-analysis of randomized controlled trials (RCTs) to evaluate the efficacy and safety of BSCPB as an adjunct to general anesthesia in patients receiving thyroid surgery. Eight RCTs, including a total of 799 patients (463 who underwent BSCPB and 336 controls), were analyzed. The combination of BSCPB and general anesthesia has a significant benefit in reducing pain 6 and 24 h after thyroid surgery.[14] However, in the present study, we observed a significant reduction in median VAS score and prolonged duration of analgesia. We observed a steady increase in VAS score as the patients were not given any analgesics until they demanded them. However, all patients received rescue analgesics once they complained of mild pain (VAS ≥4).

Elbahrawy and El Deeb did a study to assess the effect of adding dexamethasone in SCPB in thyroid surgery among 90 patients scheduled for thyroid surgeries into three groups according to the contents of cervical block in addition to general anesthesia. The control group, received BSCPB with ropivacaine 0.2% which was compared with one group that received BSCPB with ropivacaine 0.2% plus 8 mg dexamethasone and another group which received BSCPB with ropivacaine 0.2% plus 8 mg dexamethazone intravenously. Patients who received dexamethasone needed less postoperative rescue analgesic requirement than in the control group. Pain scores were statistically significantly less test group than in control groups at 6 and 8 h postoperatively. The occurrence of nausea and/or vomiting is statistically significantly less frequent in test groups when compared with the control group postoperatively.[15] In our study, we found that the addition of dexamethasone to BSCPB resulted in decrease in pain scores, mean time of analgesic requirement, and side effects such as vomiting and nausea compared to the other group.

The present study has few limitations as well. End tidal isoflurane concentration was not recorded. We followed up the patient only for first 24 h after administering the drug; hence, the analgesic effect of drug and the total rescue analgesic requirement after 24 h could not be studied. Future studies should assess the effects of this block on long-term benefits of pain relief and assess whether the reduced anesthetic consumption reflects the recovery pattern.

Study design

Type of the study is prospective double-blinded RCT.

CONCLUSION

We conclude that in thyroid surgeries ultrasound guided Bilateral Superficial Cervical Plexus block using 0.25% Bupivacaine 19 mL With Dexamethasone 4 mg on either side before induction of general anesthesia provided longer duration of postoperative analgesia and lesser nausea and vomiting compared to 0.25% Bupivacaine alone.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.