European Journal of Cardiovascular Medicine

The  search for a better adjuvant to local anesthetics which prolong the duration of block with minimum adverse effects. 

Clonidine4, a selective alpha2 adrenergic agonist, when combined with local anesthetic agent demonstrated a promising results in lowering the onset time and  prolong analgesic action in the post-operative period without causing much side effects.

Calcium plays an important role in analgesia produced by local anaesthetics1. The activation of NMDA receptors which leads to calcium entry  into the cells which potentiates the spinal cord and plays role in pain formation. Thus, calcium channel blockers6 prevent central sensitization and provide better sensory motor  block characteristics.  Verapamil8 , a synthetic derivative of L-type calcium channel blocker can potentiate the analgesic action of local anesthetics which can reduce post-operative pain and  analgesic consumption. It also have a potent local anesthetic activity reflecting inhibition of  fast sodium channels.

Not  much research done on comparing these two agents as adjuvants3, so the present study aimed to compare the effects  of clonidine4 and verapamil when used with bupivacaine during brachial plexus blockade.

AIMS AND OBJECTIVES:

The primary aim of the study is to know the effect of clonidine and verapamil as a adjuvant to bupivacaine in supraclavicular block.

The objectives of the study is to evaluate the onset of sensory and motor blockade

1). Duration of sensory and motor blockade

2). Need for rescue analgesia in the first 24 hours post-operative period

3). Adverse events if any.

In this double blinded descriptive observational study, after obtaining approval from the institutional ethics committee, this study was carried out in 100 ASA I and ASA II patients undergoing upper limb surgeries under USG guided Supraclavicular brachial plexus block. All patients underwent thorough pre-anesthetic evaluation with detailed history, clinical examination and necessary investigations. Procedure was explained in detail in their own language and after obtaining informed consent. Patient refusal, uncontrolled diabetes mellitus, renal or liver disease, hemodynamic instability, pregnant women, allergy to local anesthetics, coagulation disorder and previous neurological deficit were excluded from the study. Randomization was made using random number table for allocating the patients in the respective groups. Supraclavicular brachial plexus block was performed using a 22G hypodermic needle under USG guidance. Sensory block was assessed using Hollmen scale by pin prick method at 0,2,5,10,25 and 30 minutes. Motor blockade was measured at 0,2,5,10,25 and30 minutes and graded according to 3 point modified Bromage score. The duration of sensory block was defined as the time interval between complete sensory block and the return of normal sensation. Sensory block was assessed hourly for 24 hours in the post-operative period. The duration of motor block was defined as the time interval from the onset of motor blockade to the time where the patient were able to lift their hand and move the fingers with their normal muscle power. Motor block was assessed hourly for 24 hours in the post-operative room. The first onset of pain in the post-operative period was noted. It was assessed using visual analog scale. Duration of post-operative analgesia was taken till the patient asked for rescue analgesia. Incidence of adverse events during intraoperative and post-operative period were recorded and treated accordingly. All the data were entered and analysed using SPSS verison 24. Mean and SD were derived for all the parametric variables and percentage for the frequency variables. Statistical inference was assessed using ANOVA and the difference between the groups was interpreted using post hoc test of Bonferroni, by considering p value of less than 0.05 as statistically significant.

100 patients aged 18-60 years of ASA I and II undergoing elective upper limb surgeries were  selected. Block was successful in all the patients and all the  enrolled patients have completed the study.

TABLE 1: DEMOGRAPHIC DATA OF THE PATIENT STUDIED

FIGURE-1: AGE OF STUDY GROUP

TABLE-2: AGE DISTRIBUTION

The mean age in group A is 39.01 and in a group, B is 38.98 and the p-value is not statistically significant.

FIGURE-2: AGE DISTRIBUTION

FIGURE-3:GENDER DISTRIBUTION

The male is to female ratio in group A is 25:25 and in group, B is 26:24

FIGURE-4: WEIGHT DISTRIBUTION

The mean weight in group A is 74.96 kilograms group B is 78.52 kilograms and the p-value is not statistically significant.

ONSET OF SENSORY BLOCK-

Table 3:  Time for Onset Of Sensory Block( time in minutes)

FIGURE 5: Onset Of Sensory Block

The mean time for onset of sensory block in Group A was 2.50 ±0.3747 minutes and 3.50±0.51 seconds in Group B. Hence there was earlier onset of sensory block in Group A which was significant (p value <0.001) statistically significant.

ONSET OF MOTOR BLOCK-

Table 4:  Time for Onset Of Motor Block

FIGURE 7: Time for Onset Of Motor Block

The mean time for onset of motor block in Group A was 8.08±0.459 minutes and 10.02±0.48 minutes in Group B. The difference between the two groups statistically significant. (p <0.001)

DURATION OF SENSORY BLOCK-

Table 5:  DURATION  OF SENSORY BLOCK

FIGURE 7:  Duration of sensory block

The mean time for duration of sensory block was 505.75±18.10 minutes in Group A and 565.75±18.38 minutes in Group B It was statistically significant in Group A with p value <0.001.

DURATION OF MOTOR BLOCK-

Table 6:  Duration Of Motor Block

FIGURE 8:  Duration Of Motor Block

The mean time for duration of motor block was 365.5±9.323 minutes in Group A and 302.6250± 13.15 minutes in Group B. Hence the total duration of motor block was statistically significant (p<0.001).

FIGURE-9: DURATION OF SURGERY

The mean duration of surgery in group A is 140.24 minutes and in a group, B is 142.66 minutes and the p-value is not statistically significant.

TABLE-7: POSTOPERATIVE VAS SCORES

At 0 hours, the mean VAS score in group A is 1.8 and in a group, B is 1.36, and the p-value is not statistically significant. At 2,4,8,12,24, the mean VAS scores in group A were 2.28,3.08,4.18,4.36 and 4.42 in group B were 2.94,3.76,4.6,4.36 and 4.94 and the p-value is statistically significant.

FIGURE-10: POSTOPERATIVE VAS SCORE:

FIGURE 11: AMOUNT OF RESCUE ANALGESIA

The mean amount of rescue analgesia in group A is 0.84 and in group B is 1.22 and the p-value is significant.

There are different types of receptors which mediate  pain in peripheral sensory nerve fibres. The understanding of such receptors is important in administering different adjuncts along with local anesthetics as these adjuncts5  can prolong the duration of analgesia and reduces the amount of systemic analgesics which in turn increase the incidence of side effects.

At present, there are several adjuncts which not only prolong the duration of sensory and motor block it can also increase the duration of analgesia. This study highlights the use of clonidine  and verapamil being an adjunct to local anesthetic bupivacaine in supraclavicular brachial plexus block.

In the early 1990s Cheryl  et al, conducted a study which compares the ropivacaine and bupivacaine for brachial plexus block and concluded that peripheral nerve block patients needs additional analgesia for pain relief and so they used adjuvants such as opioids, clonidine,  verapamil, neostigmine and tramadol during brachial plexus block.

According to Franco CD,Vieira2 et al study, the ideal dosage for brachial plexus block would be  around 20-30ml  depending upon concentration. For our patient, we used 20ml of 0.5% bupivacaine3 combined with either 1ml of clonidine 150mcg or 1ml of verapamil 2.5mg as adjuvants.

Hemodynamic parameters was found to  have no statisitical significant difference between both the groups.

Studies  in the recent past have similar results stating that adjuvants like clonidine or verapamil have no effect on hemodynamics.

In our current study, we found that the clonidine group had substantially longer and earlier sensory and motor block when compared to the verapamil7 group which was similar to major studies.

Limitation of the study was that it was a smaller sample size and pain scale  bias .

In addition to accelerating the onset of sensory block and extending the length of motor block, adding clonidine as an adjuvant to bupivacaine results in stable hemodynamic parameters without side effects. Clonidine was more effective than verapamil when added as an adjuvant to supraclavicular brachial plexus block. Conflicts of interest: None.

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5).Jacques T, YaDeau, Michael A, Gordon, Enrique A, et al, Buprenorphine, Clonidine, Dexamethasone, and Ropivacaine for interscalene nerve blockade: A Prospective, Randomized, blinded, Ropivacaine dose-response study.Pain Med 2016; 17:940-960.

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