INTRODUCTION:

Bupivacaine, an amide local anesthetic belonging to the pipecoloxylidide group has been the most widely used longer acting local anesthetic agent. However, accidental intravascular injection or excessive administration of Bupivacaine has substantially produced adverse effect on cardiac functions in the form of increase conduction time, nodal refractoriness and ventricular arrhythmias.¹

Ropivacaine is an enantiomerically pure pipecoloxylidide amide local anesthetic agent with longer duration of action. Ropivacaine and Bupivacaine show differences in toxicity profile but clinically their regional anesthetic actions are quite similar. Ropivacaine appeared to be less cardiotoxic than Bupivacaine.²

Brachial plexus block using supraclavicular approach is one of the common methods followed in upper arm surgeries. There is adequate information available determining the anesthetic efficacy of Bupivacaine and Ropivacaine, either single arm or comparative studies in various approaches such as spinal, epidural, subclavian, interscalene and axillary. The rationale of this study was to compare the efficacy and safety of Bupivacaine and Ropivacaine in supraclavicular brachial plexus block in patients undergoing upper arm surgeries in a tertiary care set up.

MATERIALS AND METHODS:

The study was conducted as a randomized, controlled, double blind study after obtaining approval from the Institutional Ethics Committee. The study was conducted in a tertiary care set up in collaboration with departments of Anesthesia and Orthopedics. Patients admitted in orthopedic wards and elected for upper arm surgeries using supraclavicular branchial plexus block were screened for the study. These patients were evaluated preoperatively by anesthesiologist and screened using inclusion and exclusion criteria. Patients included for the study were adults equal to or above 18 years of age, either sex, scheduled for elective surgery to upper extremities, eligible for anesthesia using supraclavicular brachial plexus block, fulfilling American society of Anesthesiologist (ASA) physical status criteria I and II and those who were willing to give informed consent. Patients with concomitant illness such as diabetes or hypertension were allowed to continue their relevant medications. Patients were excluded from the study if they were suffering from any untreated chronic illness, abnormal ECG findings, pregnant, lactating, bronchopulmonary disease, known allergy to study drugs, smoking or any other form of drug dependence. After screening patients, 60 patients were selected for the study. Sixty patients were randomized into two groups consisting of 30 patients each using computer generated randomization chart. Group A received 40 ml of injection Bupivacaine hydrochloride 0.5% and Group B received 40 ml of injection Ropivacaine hhydrochloride 0.5% through supraclavicular brachial plexus block method.

The supraclavicular location of brachial plexus was identified and confirmed using nerve locator. Each patient was examined from the day of admission till 48 hours post operatively and followed up till one week. Selected patients underwent all the baseline investigations such as complete blood count, liver function tests, renal function tests, chest x – ray and electrocardiogram. These investigations were repeated one day and again one week after the surgery to check for any differences. During the day of surgery, before patient was anesthetized, vital parameters such as pulse rate, blood pressure, ECG parameters such as PR interval, QRS duration and QT interval, and respiratory rate were recorded and preanesthetic medications were given. These patients were administered the study drugs by supraclavicular brachial plexus block method under aseptic precautions. For identifying and specifying the location of brachial nerve plexus in the supraclavicular region, nerve locator (Stimuplex HNS, Braun Medical) was used. After observing the twitches in the upper arm muscles following the stimulation of brachial plexus, 40 ml of the respective study drug was injected after confirming by aspiration that needle was not intravascular while injecting. The time of injection of drug was noted. For determining the onset of sensory loss, patient was assessed constantly for loss of touch sensation in all the dermatomes supplied by brachial plexus. The time at which the loss of touch sensation begins was noted and the difference in the time at the start of loss of touch and dosing time was calculated as onset of sensory loss in minutes. For determining the onset of motor function loss, losses of movement of muscle supplied by nerves of brachial plexus were assessed constantly. The time at which complete absence of movement at elbow and wrist joints occurred was noted. The difference between the noted time at which complete absence of movements occurred and dosing time was calculated as onset of motor loss in minutes. If the procedure failed the rescue medications were given and surgery was continued under general anesthesia. Any requirement for additional dose of local anesthetic agents if needed was recorded.

The use of antibiotics and sedatives during anesthesia was permitted. After surgery, patients were followed up in the recovery room for constant assessment of recovery of touch sensation and beginning of movement at elbow and wrist joints and respective times were noted. The difference between the noted times for recovery of touch sensations and motor movement at elbow and wrist joint and the time of onset of sensory loss and motor loss respectively were calculated as the duration of sensory loss and motor loss in minutes respectively. Patients were constantly monitored and vital parameters; ECG parameter and respiratory rate were noted and followed up in ward and a week after they were discharged. Patients were informed to report as soon as they developed any adverse effect after they were discharged. Efficacy of the study drugs were studied by noting the time of onset and duration of sensory loss and motor loss. Onset and duration of sensory loss and motor loss in minutes obtained from group A and group B patients and mean times were calculated and compared using “unpaired T test”. Safety of the study drugs were studied by noting any reported adverse reactions and comparing the occurrence of same as incidence in either group.

RESULTS:

In the present study, sixty patients posted for elective upper arm surgery were selected after the screening process. These patients were equally randomized to either group A (receiving Injection Bupivacaine 0.5%) or group B (receiving injection Ropivacaine 0.5%) using computer generated randomization technique. These baseline parameters didn’t show any significant variations and all the baseline investigations were normal. Mean age of patients in group A was 38 years and in group B was 39 years.

Efficacy Parameters

The mean time taken for onset of action of sensory loss and motor loss in group A (Bupivacaine group) patients are 9.26 minutes and 12.8 minutes respectively. The mean time taken for onset of action of sensory loss and motor loss in group B (Ropivacaine group) patients are 16.86 minutes and 18.9 minutes respectively. On comparing the onset of sensory loss and motor loss between Bupivacaine and Ropivacaine groups using unpaired T – test, it was found that there was high statistical difference between the groups as shown in the table 1. This suggests that Bupivacaine produced significantly quick onset of sensory and motor loss as compared to Ropivacaine.

Table 1: Comparison of time taken for onset (minutes) of sensory and motor loss in both the study groups.

Time taken for onset (min)

Group A

(Mean± SD)

Group B

(Mean± SD)

P value

Sensory Loss

09.26 ± 3.56

16.86 ± 6.51

<0.001*

Motor Loss

12.80 ± 5.14

18.90 ± 6.18

<0.001*

(*P value <0.001 – Highly significantly)

The mean duration time of sensory loss and motor loss in group A (Bupivacaine group) patients was 604.4 minutes and 657.53 minutes respectively. The mean duration time of sensory loss and motor loss in group B (Ropivacaine group) patients was 737 minutes and 724 minutes respectively. On comparing the duration time of sensory loss and motor loss between Bupivacaine and Ropivacaine groups using unpaired T – test, it was found that there was a significant statistical difference between the groups as shown in the table 2. This suggests that duration of sensory loss and motor loss were significantly less in Bupivacaine when compared to Ropivacaine.

Table 2: Comparison of duration (minutes) of study parameters in both the study groups.

Duration Time

(minutes)

Group A

(Mean ± S.D.)

Group B

(Mean ± S.D.)

P value

Sensory Loss

604.40 ± 87.35

737.00 ± 91.35

<0.001**

Motor Loss

657.53 ± 99.24

724.00 ± 71.61

<0.05*

(*P value <0.05 – Significantly; ** P value < 0.001 – highly significant)

Safety Parameters

One patient in Bupivacaine group reported of developing fever on follow up visit after one week of discharge. No adverse reactions were reported by patients receiving Ropivacaine.

DISCUSSION:

The selection of the optimal long-acting local anesthetic for brachial plexus block must take into consideration, what are the available anesthetics, the time to onset of anesthesia, duration of blockade, and side effects of each drug and dose. A drug that has a fast onset, long duration, and minimal toxicity profile could be an advantage. Ropivacaine, a newer propyl– pipecoloxylidide derivative and an amide local anesthetic agent offers an alternative to Bupivacaine for long-acting neural blockade. ³

Onset:

In the present study, the mean time to onset of sensory anesthesia and complete motor block using 0.5% Bupivacaine was 9.2 minutes and 12.8 ± 5.14 minutes respectively and using 0.5% Ropivacaine, they were 16.86 minutes and 18.9 minutes respectively. There was a highly statistical difference in the mean time to onset of sensory anesthesia and complete motor block when Bupivacaine was compared with Ropivacaine favoring an earlier onset of anesthesia, sensory anesthesia and complete motor block with Bupivacaine as compared to Ropivacaine (P < 0.001).

This finding from present study was in accordance to the finding of studies conducted by Hamaji A et al. ⁴ However, the above finding was not in agreement with the studies conducted by Kaur A et al ⁵, Raeder et al ⁶, and Altintas et al ⁷. In these studies, the onset of sensory loss and motor loss didn’t significantly differ in patients receiving Bupivacaine or Ropivacaine. This disagreement could possibly due to the different approaches to the brachial plexus block and different concentrations of these drugs employed. The use of nerve locator to specify the brachial plexus location could also influence the onset of sensory loss and motor loss in the present study.

Duration:

In the present study, the mean duration of sensory anesthesia and complete motor loss using Bupivacaine was 604.4 minutes and 657.53 minutes respectively and using Ropivacaine, the mean duration of sensory anesthesia and complete motor loss was 737 minutes and 724 minutes respectively. In the present study, there was a statistically significant difference between the duration of complete motor loss (P < 0.05) and sensory anesthesia (P < 0.001; highly significant) when Bupivacaine was compared with Ropivacaine showing that Ropivacaine had longer duration of sensory anesthesia and complete motor loss compared with Bupivacaine. The above finding is not in accordance with the studies comparing Bupivacaine and Ropivacaine carried out by Klein et al ³, Kaur A ⁵, Raeder et al ⁶, and Altintas et al ⁷. In these studies, there was no difference in the mean duration of analgesia, sensory anesthesia and complete motor loss between Bupivacaine and Ropivacaine and both the drugs were equally effective. However, the duration of sensory loss and motor loss with Bupivacaine was comparable to the findings in study conducted by Pandya CJ et al ⁸. The duration of sensory loss and motor loss with Ropivacaine in the present study was comparable to the findings in the studies conducted by Madhusudhan R et al ⁹, Janzen PR et al ¹⁰ and Tripathi D et al ¹¹.

Safety:

One patient receiving Bupivacine developed fever after one week of discharge. However, on examination it was found out to be unrelated to the surgery. Patients receiving Ropivacaine didn’t report any side effects. There was no use of any rescue medication or additional doses of local anesthetics. The risk of development of any significant adverse reaction could be minimized by the use of nerve locator which enhanced the specificity of injection location site and facilitated use of minimum volume of drug solution.

CONCLUSION:

In the present study, Bupivacaine 0.5% showed early onset of sensory anesthesia and motor block as compared to Ropivacaine 0.5% at equal volumes when given by supraclavicular method of brachial plexus block using a nerve locator. However, the duration of sensory anesthesia and motor block was longer with Ropivacaine 0.5% as compared to Bupivacaine 0.5%. Both the drugs were found to be safe in the study.

REFERENCES:

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Received on 05.10.2015 Modified on 16.10.2015

Res. J. Pharmacology & P’dynamics. 7(4): Oct.-Dec., 2015; Page 187-190

DOI: 10.5958/2321-5836.2015.00038.5