Comparative study between dexamethasone and dexmedetomidine in supraclavicular block

INTRODUCTION

Peripheral nerve block has taken patient care in anaesthesia to a whole new level. Because of the advent of nerve stimulator and peripheral nerve block techniques, even patients in ASA grade 3 and 4 can be taken up for surgery safely. Moreover, with the use of adjuvants in brachial plexus block (BPB), one can extend patient care in the form of extended postoperative analgesia, ensure compliance of patient with physiotherapy and early mobilization of patient with stable haemodynamic variables. Dexmedetomidine is a highly selective α-2 adrenergic agonist with an affinity of 8 times greater than clonidine.¹

Various studies have shown that dexmedetomidine prolongs the duration of sensory and motor block and provide a very good analgesia when used as an adjuvant to local anaesthetics for nerve blocks.^2-5 The anaesthetic and the analgesic requirement are reduced substantially because of its analgesics properties and augmentation of local anaesthetics (LA) effects as they cause hyperpolarization of nerve tissues by altering transmembrane potential and ion conductance at locus ceruleus in brain stem. Dexmedetomidine provides stable haemodynamics and decreases oxygen demand due to enhanced sympathoadrenal stability and hence makes it a very useful pharmacological agent for this purpose.

Steroids have powerful anti-inflammatory as well as analgesic property. Perineurally injected steroids is reported to influence postoperative analgesia. Dexamethasone microspheres have been found to prolong the block duration in animal and human studies and adding methyl prednisolone to local anaesthetic increase the duration of brachial plexus block.^6-9

Because of the above mentioned profiles of the drugs, we have chosen dexmedetomidine along with dexamethasone for our study and evaluate their onset time, duration of sensory - motor blocks and quality of intraoperative as well as postoperative analgesia.

METHODS

This study was conducted in Department of Anaesthesia of our Medical College and Hospital from December 2016 to November 2017. Our study was conducted in 100 ASA grade I and II patients aged between 20 - 60 years of either sex posted for elbow, forearm and hand surgeries using peripheral nerve stimulator guided supraclavicular brachial plexus block after attaining permission from institutional ethical committee and written informed consent.

Group D

Patients received 20ml of 2% lignocaine with adrenaline plus 18ml of 0.5% bupivacaine plus 50μg of dexmedetomidine (0.5ml drug plus 1.5ml NS), a total volume of 40ml.

Group X

Patients received 20ml of 2% lignocaine with adrenaline plus 18ml of 0.5% bupivacaine plus 8mg of dexamethasone (2ml), a total volume of 40ml

Exclusion criteria

ASA class 3, 4 and 5, Infection at the site of injection, Presence of coagulopathies, Hypersensitivity to any of bupivacaine, dexamethasone or dexmedetomidine, Unwilling patient

Patient was taken to OT after starting ringer lactate infusion using 18G I.V cannula in the non – operated hand. Baseline values of heart rate, ECG, non-invasive blood pressure, peripheral oxygen saturation, respiratory rate was noted before execution of block technique. The study drug was prepared by an anaesthesiologist who was not involved in the study. Patient was asked to lie supine and head of the patient was turned to the contralateral side. Interscalene groove was identified and the site was cleaned with povidone iodine solution. A superficial skin wheal was made one finger breadth above clavicle in the interscalene groove with 0.5% lignocaine. A 5cm insulated nerve stimulator needle was attached to a nerve stimulator and the current to be delivered being set at 2.0mA and a pulse width of 100μs. Needle direction was almost perpendicular with slight inclination towards contralateral nipple and desired response in the form of muscle twitch of fingers were seeked. Once the desired response was attained, current was reduced to 0.5mA and if the response still persisted, the drugs were injected after negative aspiration for blood before injecting the drugs in aliquots of 3ml to a total volume of 40ml.

Onset of sensory block was assessed by spirit swab method. Assessment of motor block was done using the Bromage score.

Sedation was assessed using Ramsay sedation score.

Surgery duration was noted. Side effects like dryness of mouth, nausea, vomiting and complications like LA toxicity, pneumothorax and post block neuropathy were monitored.

Duration of sensory block was defined as the time interval between the end of drug administration and complete resolution of anaesthesia on all nerves.¹⁰ The duration of motor block was defined as the time interval between the end of drug administration and the recovery of complete motor function of hand and forearm.¹⁰

The data was compared using various statistical tools like mean, range and percentage.

RESULTS

Regarding the age and sex distribution, there was no difference among the two groups taken up for study. The youngest patient in dexmedetomidine group (Group D) was of 22 years whereas oldest was of 60 years. In dexamethasone group (Group X) the youngest patient was of 20 years wheres oldest was of 56 years (Table 3).

N- Number of patients

Majority of patients in both groups were males (Figure 1).

Regarding the duration of surgery, no major difference was found in both groups (Figure 2).

The time taken for onset of sensory block was almost same in both groups (Table 4) whereas time taken for onset of motor block was much less when dexmedetomidine was used (Group D) as compared to Group X using dexamethasone (Table 4).

N = Number of patients, % = Percentage of patients

The time taken for onset of motor block was much lesser in group D using dexmedetomidine (mean time – 11.8 minutes) as compared to group X using dexamethasone (mean time - 19.2 minutes) (Table 5).

N = Number of patients, % = Percentage of patients

Regarding the duration of sensory block, the block lasted much longer for dexemedetomidine group as compared to dexamethasone group (Table 6).

N = Number of patients, % = Percentage of patients

Similar results were obtained for duration of motor block where mean time for D group (858.2 minutes) was much greater than X group (684.6 minutes) (Table 7).

N = Number of patients, % = Percentage of patients

Regarding the onset of pain in the postoperative period, it was much later in patients given dexmedetomidine as compared to patients given dexamethasone (Table 8).

N = Number of patients, % = Percentage of patients

DISCUSSION

We observed in our study that patients who underwent upper limb surgery after execution of supraclavicular BPB, addition of dexmedetomidine or dexamethasone to LA solution, shortens the motor block onset time and prolongs the duration of block time. BPB is one of the easiest, safest and most commonly performed peripheral nerve blocks in day to day practice of anaesthesia. Using adjuvants like dexmedetomidine or dexamethasone further enhances the onset, quality and duration of analgesia.¹¹

We chose supraclavicular approach for BPB as the narrowest part of plexus is located there and anaesthesia will be rapid, dense and predictable for the entire upper limb. By using nerve stimulator, we avoided problems associated with conventional technique, like discomfort, nerve injury and higher failure rates.⁵

Dexmedetomidine is a selective α-2 agonist, a pharmacological active d-isomer of medetomidine. One of the highest densities of α-2 receptors have been located in locus ceruleus. The hypnotic and sedative effects of α-2 adrenoreceptor activation have been attributed to this site in CNS. It is also the site of origin of the descending medullospinal noradrenergic pathway, known to be an important modulator of nociceptive neurotransmission. In the region of the brain, α-2 adrenergic and opiodergic system have common effector mechanisms, indicating that dexmedetomidine has a supraspinal site of action. Presynaptic activation of α-2 adrenoreceptor in CNS inhibits the release of norepinephrine, terminating the propagation of pain signals and their postsynaptic activation inhibits sympathetic activity, thereby decreasing the heart rate and blood pressure in higher doses.¹¹

Addition of steroid to LA effectively and significantly prolongs the duration of analgesia as well as producing earlier onset of action.¹² Steroids are very potent anti-inflammatory and immunosuppressive agents. Dexamethasone, a synthetic glucocorticoid derivative is preferred because of its highly potent anti-inflammatory property, about 25-30 times more potent than hydrocortisone and without any mineralocorticoid activity. Preoperative administration of dexamethasone has been shown to reduce overall pain scores and analgesia requirements in the postoperative period without any adverse effects.¹³ The possible mechanism of analgesia and antiemetic actions are due to the anti-inflammatory property of dexamethasone.^9,12

CONCLUSION

Dexmedetomidine and dexamethasone, both are good as adjuvants in peripheral nerve blocks. But the study conducted by us revealed that dexmedetomidine is a better alternative for decreasing the onset of motor block along with enhanced quality and duration of supraclavicular block with safe profile.

ACKNOWLEDGEMENTS

Authors would like to acknowledge medical college and hospital for its support and patients for cooperating with the study protocol.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the institutional ethics committee

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