Epidural anaesthesia is the most commonly used technique for providing perioperative surgical anaesthesia and postoperative analgesia in lower limb orthopaedic surgeries. Early postoperative mobilization with minimal pain is the most desirable feature in modern orthopaedic surgeries.[1]
Bupivacaine, levobupivacaine, and ropivacaine are commonly used local anaesthetic (LA) agents for epidural block and provide good quality of anaesthesia and analgesia. Bupivacaine is used as a racemic mixture of equimolar amounts of R (+) Dextrobupivacaine and S (-) Levobupivacaine. R (+)Dextrobupivacaine is found more toxic to both the central nervous system and the cardiovascular system . Levobupivacaine is an amide type of local anaesthetic agent which is the pure S(-) enantiomer of bupivacaine and because of its significantly less cardiovascular and central nervous system toxicity, levobupivacaine seems to be a better alternative to bupivacaine.[2],[3].[4],[5],[9]
Narcotic analgesics are commonly used as adjuncts to local anaesthetics in epidural anaesthesia. They hasten the onset, improve the quality of the block as well as prolong the duration of analgesia. Opiods like fentanyl is a highly lipid-soluble, strong μ-receptor agonist and phenyl piperidine derivative with a rapid onset and short duration of action.The rationale for adding fentanyl with local anaesthetic drugs is that, the local anaesthetic act at the nerve axon and the opioid at the spinal cord receptor to eliminate pain via a combined and possibly synergistic mechanism. Use of fentanyl is also known to reduce the minimum local analgesic concentration of bupivacaine and levobupivacaine, thereby reducing their side effects.[1],[6],[7]
Various studies have undergone to compare these two drugs in labour analgesia, gynaecological and abdominal surgeries but the review of literature showed limited evidence about comparision of these two drugs in epidural anaesthesia for lower limb orthopaedic surgeries.[8] Therefore this study was undertaken to compare the onset and duration of motor & sensory block, degree of motor block, haemodynamic changes, intra operative and postoperative complications in epidural anaesthesia with levobupivacaine vs bupivacaine using fentanyl as a common adjuvant in patients undergoing lower limb orthopaedic sugeries.
Subjects and Methods:
This prospective randomized study was conducted in department of anaesthesiology after approval from institutional ethical committee and written and informed patient consent including 60 patients of ASA physical status I or II aged 18 to 60 years undergoing elective lower limb orthopaedic surgeries under epidural anaesthesia. Among the selected individuals, those fulfilling the inclusion criteria were included in the study. Exclusion criteria were known hypersensitivity to study drugs, ASA physical status III or above, patient refusal, general contraindications for epidural anaesthesia, morbid obesity and patients with coagulation abnormalities.
After all routine investigations and complete preanaesthetic checkup, all the patients in the study were hydrated with 10ml/kg Ringer’s lactate intravenously before the procedure.
The study population was randomly divided into 2 groups with 30 patients in each group , Group B received 13ml of 0.5% bupivacaine with 2ml (100 mcg) of fentanyl (total volume-15ml) and Group L recieved 13ml of 0.5% levobupivacaine with 2ml (100 mcg) of fentanyl (total volume-15ml) .
Under all aseptic precautions patient’s back was painted and draped. An 18 G Touhy’s epidural needle was introduced into L3-L4 epidural space using loss of resistance to air technique. Epidural catheter was inserted 4 cm into the epidural space and 3ml of 2% lignocaine with adrenaline was given as a test dose. Continuous cardiopulmonary monitoring was done and the study drug was injected into the epidural space. The time of administration of the study drug was considered as zero time to assess the duration of blockade.
The baseline values of haemodynamic parameters( heart rate, systolic blood pressure, diastolic blood pressure) oxygen saturation ( SpO2 ) were recorded and the above parameters were monitored every 5 minutes until 30 minutes of epidural drug administration and every 30 minutes thereafter till the completion of the surgical procedure.The various complications (nausea, vomiting,hypotension,urinary retention,arrhythmia and pruritus) were assessed perioperatively.
Onset of sensory block or analgesic block at T10 dermatome i.e time interval between the end of administration of the anaesthetic drug and the onset of cutaneous analgesia at T10 was evaluated using midline bilateral pin prick every minute till complete loss of cutaneous sensation at T10 level. Motor block was assessed by Modified Bromage scale (0 = no block ,1= inability to raise extended leg ,2=inability to flex the knee,3= inability to flex ankle and foot).[19]
The time of onset and duration of motor blockade was assessed.
Statistical analysis: It was performed using Student’s unpaired t-test and Chi-square test incorporating Fishers exact test. Significance is assessed at 5% level of significance. The value of P < 0.05 was considered as significant .
Results:
Both the groups were comparable in terms of demographic profile and duration of surgery.(Table 1)
The onset of sensory block was 9.54±1.03 and 9.85±0.97 min for group B and group L respectively and onset of motor block for group B was 19.48±1.58 min and for group L was 19.01±1.30 min. Patients in both groups were comparable with respect to onset of sensory and motor block (p value >0.05).(Table 2)
In patients belonging to group L, 63.3% attained T6 level, 30% attained T7 level and 6.7% attained T10 levels, whereas in group B, 60% attained T6 levels, followed by 30% attaining T7 level and 10% attaining T10 level. There was no significant difference in the highest level of sensory block achieved in both groups.(Table 2)
The duration of motor block was 273.0±11.0 min and 274.9±18.45 min in group B and L, respectively and duration of sensory block was 371.33±13.23 min and 366.17±5.83 min in group B and L respectively. Patients in both groups were comparable with respect to duration of motor and sensory block (p value >0.05).(Table 2)
Degree of motor block was assessed by modified bromage scale showed that in group B,46.67% of patients had grade 2 and 33.33% of patients had grade 3 degree of motor block, whereas in group L only 33.33% of patients had grade 2 and 26.67% of patients had grade 3 degree of motor block. The degree of motor block was higher in group B.(Table 2)
Baseline heart rate, systolic blood pressure, diastolic blood pressure and oxygen saturation in group B and group L were comparable. These parameters were also remained stable throughout the duration of block in both the groups.(P>0.05),(Figure 1),(Figure 2) and(Figure 3)
In our study, in group B, 5 patients experienced nausea, 1 patient had vomiting, 4 patients had hypotension and 4 patients had pruritus whereas in group L 4 patients experienced nausea, 1 patient had vomiting, 5 patients had hypotension and 5 patients had pruritus. Thus both groups were comparable regarding complications (p value >0.05). We did not observe arrhythmia, urinary retention and respiratory depression in any of the patient in both groups.(Table 4)
Discussion:
Epidural anaesthesia provides excellent pain relief with early mobilization of patients particularly when a local anaesthetic agent is combined with an adjuvant like opioids. The addition of adjuvants in epidural anaesthesia accelerates the onset of sensory blockade but also decreases the effective dose of local anaesthetic agent. The synergistic effect between local anaesthetic agent and opioids is well established for epidural anaesthesia.[1],[9]
Bupivacaine is associated with a number of side effects like unwanted motor blockade, neurotoxicity and cardiotoxicity which may cause death due to its cardiotoxicity after accidental intravenous injection and warrants continued search for new and safer local anaesthetic agent. Levobupivacaine have been developed as an alternative to bupivacaine after the evidence of its cardiotoxicity and it seems to have less toxic effects on cardiovascular and central nervous system.[10]
The mean time of onset of sensory and motor block was statistically not significant between the two groups, (p>0.05). The previous studies have demonstrated that levobupivacaine and bupivacaine were comparable in terms of onset of sensory blockade, regardless of the type of surgery.[8]
Kara F et al[11] who compared the effects of epidural 0.5% bupivacaine and 0.5% levobupivacaine administration on anaesthesia quality, incidence of side effects in hip and lower extremity surgery and Cox CR et al[12] who compared 0.5% bupivacaine and 0.5 % levobupivacaine administered epidurally for lower limb surgeries found no significant difference in the onset of sensory and motor blockade, which may be due to the same concentration (0.5%) of local anaesthetic used in our study also.
The duration of motor block was assessed by onset of motor block to complete recovery (Bromage scale-0). In our study there was no significant difference in duration of motor block in both the groups(p>0.05). Similar to our study a study done by Casimiro C et al[8] who compared levobupivacaine plus fentanyl and racemic bupivacaine plus fentanyl in epidural anaesthesia for lower limb surgeries and in another study by Kara F et al[11] compared the effects of epidural 0.5% bupivacaine and 0.5% levobupivacaine administration on epidural anaesthesia found that there was no significant difference in duration of motor blockade with both drugs (p>0.05) and Kopacz et al[13] who compared epidural 0.75% levobupivacaine with racemic bupivacaine for lower abdominal surgeries found similar duration of motor block in both groups (p>0.05).
However in contrast to our study Garcia et al[14] compared 0.5% levobupivacaine with 0.5% bupivacaine in epidural anaesthesia for caesarean delivery ,found a longer duration of motor block with levobupivacaine. The doses used in our study were same as that used in study by Garcia et al but have longer duration of motor block with levobupivacaine have no clinical significance and could not be explained as far as the dose is concerned.
In our study mean duration of sensory block was comparable in both groups (p value >0.05). The results of our study are similar to the study done by Casimiro C et al[8] who concluded that Levobupivacaine plus fentanyl versus racemic bupivacaine plus fentanyl in epidural anaesthesia for lower limb surgeries produced sensory blockade of similar duration. And also in a study done by Kara F et al[11] who compared the effects of epidural 0.5% bupivacaine and 0.5% levobupivacaine in hip and lower extremity surgery found no significant difference in duration of sensory blockade with both drugs.
In contrast Cox CR et al[12] compared levobupivacaine (two different dosage) with bupivacaine (one dosage) administered epidurally for lower limb surgeries found a significantly longer duration of sensory block with one of dosages of levobupivacaine 0.75% than bupivacaine 0.5%, this may be due to different dosages used in both studies. The concentration of levobupivacaine used in our study was 0.5%, but in Cox`s study the concentration of levobupivacaine used were 0.5% and 0.75%, i.e two different doses. So the results were similar with 0.5% concentration of levobupivacaine in between two groups.
These results regarding mean duration of sensory blockade depicted the association between the dose of local anaesthetic used and duration of blockade.[8],[17]
The degree of motor block was significantly more in group B as compared to group L. Similar to our study Casimiro C et al[8] found that the proportion of patients with motor blockade as determined by the modified Bromage scale was statistically different; patients allocated to levobupivacaine group showed a higher proportion of lack of motor blockade than bupivacaine. The decreased motor block seen with levobupivacaine may be due to decreased potency of levobupivacaine as compared to bupivacaine.[15],16]However in another study, Kara F et al[11] found that there was no statistically significant difference between the groups in terms of quality or degree of motor block for both groups (p>0.05).
Haemodynamic parameters in both groups did not differ significantly with respect to heart rate and blood pressure at any time interval, which is consistent with the study done by Kara F et al[11] on comparison of epidural 0.5% bupivacaine and 0.5% levobupivacaine administration on epidural anaesthesia quality found no significant changes in the hemodynamic variants for bupivacaine and levobupivacaine, and also supported by Casimiro et al[8]. The stable haemodynamic parameters can be explained by lower volume of local anaesthetic agent used along with fentanyl as an adjuvant which has a dose sparing effect. However fentanyl may increase the incidence of pruritus, nausea, vomiting, respiratory depression and urinary retention, which were comparable between two groups.[1]
In contrast Kopacz et al[13], reported that hypotension was the most common side effect and was experienced by a similar proportion of patients in both treatment groups at the start of surgery (21% levobupivacaine, 18% bupivacaine) and during surgery (32% in both treatment groups). This may be due to use of higher concentration (0.75%) of levobupivacaine and bupivacaine in their study.
In another study done by Kara F et al[11] compared the effects of epidural 0.5% bupivacaine and 0.5% levobupivacaine administration on quality of anaesthesia, incidence of side effects, and time for requirement of analgesia in hip and lower extremity surgery found no significant difference in side effect profile in both groups.
In previous studies as by Gristwood RW et al[5] showed levobupivacaine has lesser side effect profile than bupivacaine, demonstrated that levobupivacaine could be a safer alternative local anaesthetic drug to bupivacaine, as far as cardiotoxicity is concerned. Although we were not able to reveal the safety profile of these two drugs in emergent cardiac situations produced as a result of cardiotoxicity. So it is not necessary that a larger sample size than our study could reveal significant differences in the safety profile of these two drugs. This may be the limitation of our study.
CONCLUSION:-
In our study we concluded that combination of levobupivacine and fentanyl is equipotent to bupivacaine and fentanyl in epidural anaesthesia. Rather it seems to be a better alternative local anaesthetic agent in epidural anaesthesia. Although in our study we failed to demonstrate a better safety profile of levobupivacaine than bupivacaine due to smaller sample size.