|Year : 2015 | Volume
| Issue : 4 | Page : 639-643
Implication of bupivacaine volume changes in the duration and rate of complications of femoral and sciatic nerve block for lower limb surgery
Raafat Abdel-Azim H Ismail, Mervat M Marzok, Ehab H Abd El Salam, Sahar M Talaat MD , Walid Y Kamel
Department of Anesthesiology, Intensive Care, and Pain Management, Faculty of Medicine, Ain Shams University, Cairo, Egypt
|Date of Submission||21-Dec-2013|
|Date of Acceptance||18-Jan-2014|
|Date of Web Publication||29-Dec-2015|
Sahar M Talaat
Department of Anesthesiology, Intensive Care, and Pain Management, Faculty of Medicine, Ain Shams University, Cairo
Source of Support: None, Conflict of Interest: None
The aim of this study was to study the implication of volume change of bupivacaine in the duration of motor and sensory blocks for early ambulation of the patient and in the rate of complications among patients.
Patients and methods
A total of 80 adult patients of ASA I, II, or III status, scheduled for lower limb surgery under regional anesthesia by femoral and sciatic nerve blocks, were included in this randomized prospective study. Patients were randomly divided into two equal groups (group I and group II). A total volume of 40 ml of bupivacaine 0.3% was used for peripheral nerve blockade in group I: 20 ml for femoral nerve blockade and 20 ml for sciatic nerve blockade; and a total volume of 60 ml of bupivacaine 0.3% was used in group II: 30 ml for femoral nerve blockade and 30 ml for sciatic nerve blockade. Assessment of the sensory and the motor blocks was carried out including onset of anesthesia and duration of both sensory and motor blocks. The assessment was carried out intraoperatively at 10, 20, and 30 min after the establishment of the procedure, and then at 6, 12, and 24 h after performing the block.
The onset of the block was significantly shorter in group II. The sensory block was significantly denser in group II at 12 h. The motor block was less dense in group II at 12 and 24 h. The pain scale was less in group II at 6 and 12 h.
This study revealed that increasing the volume of the local anesthetics hastened the onset of the anesthesia and increased the duration and the density of the sensory block.
Keywords: bupivacaine, motor block, peripheral nerve block, sensory block, volume
|How to cite this article:|
Ismail RAH, Marzok MM, Abd El Salam EH, Talaat SM, Kamel WY. Implication of bupivacaine volume changes in the duration and rate of complications of femoral and sciatic nerve block for lower limb surgery. Ain-Shams J Anaesthesiol 2015;8:639-43
|How to cite this URL:|
Ismail RAH, Marzok MM, Abd El Salam EH, Talaat SM, Kamel WY. Implication of bupivacaine volume changes in the duration and rate of complications of femoral and sciatic nerve block for lower limb surgery. Ain-Shams J Anaesthesiol [serial online] 2015 [cited 2019 Sep 21];8:639-43. Available from: http://www.asja.eg.net/text.asp?2015/8/4/639/172758
| Introduction|| |
A lot of surgical and pain-related cases are managed nowadays with peripheral nerve blocks  . The most important prerequisites for using peripheral nerve blockade in daily clinical practice are success rates and safety. Both issues are closely related to the injected volumes of local anesthetics (LAs)  .
During the past few decades, large volumes of LA have been used for peripheral nerve blockade techniques to compensate for morphometric methods of nerve identification  .
It is assumed that an insensate extremity is best minimized during continuous peripheral nerve blocks, because insensate extremities may be liable to accidental injury  . This concern of injury has resulted in recommendations to protect the surgical limb in a sling and/or brace and use crutches or walkers for the duration of LA infusion  . Some have recommended delaying hospital discharge until sensation returns  .
We hypothesized that lower volumes of LAs might have an impact on decreasing the duration of the blockade and hence early ambulation of the patient. In this study, we compared the effect of two different volumes of bupivacaine on the duration of sensory and motor blockades.
| Patients and methods|| |
This study was carried out in the Orthopedic Department in Ain Shams University Hospitals. The study was conducted on 80 adult patients of ASA I, II, or III physical status undergoing lower limb surgery, after obtaining informed consent and approval of the institutional ethical committee. Patients included were 18-70 years old, 150-190 cm tall, and their weight ranged from 80 to 100 kg. Patients with ASA physical status greater than III, with any contraindication to regional anesthesia, and with neurologic disorders were excluded from the study.
The patients were randomly divided by opening sealed envelopes sorted by computer-generated random allocation into two equal groups (group I and group II), with 40 patients each. In group I, a total volume of 40 ml of bupivacaine 0.3% was injected (20 ml for the femoral nerve and 20 ml for the sciatic nerve), and in group II a total volume of 60 ml of bupivacaine 0.3% was injected (30 ml for the femoral nerve and 30 ml for the sciatic nerve).
The procedure as well as the visual analogue scale were explained to the patients.
Routine preoperative assessment was carried out on the patients. The standard monitors were used for the patient.
The needle insertion site for femoral block was identified; the skin was sterilized and infiltrated by 2 ml of 1% lidocaine. A 10 cm insulated Tuohy needle was connected to a nerve stimulator (Plexygon 7501.31 type), starting with intensity of 1-1.5 mA and frequency 2 Hz. After patellar dancing was achieved, the current intensity was reduced to achieve a response at intensity between 0.2 and 0.5 mA, and the LA was injected, as previously mentioned.
Thereafter, the patient was positioned in the modified Sim's position, and the sciatic nerve was identified using Labat technique. The skin was sterilized and infiltrated by 2 ml of 1% lidocaine. The insulated needle was advanced until an evoked motor response was elicited (planter flexion, inversion, dorsiflexion, or eversion). The LA was injected as aforementioned.
Assessment of the sensory block was carried out for onset and extent using pin prick test. Assessment of the motor block was carried out using modified Bromage scale (0 = full movement; 1 = inability to raise the extended leg, can bend the knee; 2 = inability to bend the knee, can flex the ankle; 3 = no movement)  . The assessment was carried out intraoperatively at 10, 20, and 30 min after the establishment of the procedure.
The patients were assessed postoperatively at 6, 12, and at 24 h after the block blindly by another anesthetist for the duration of the sensory block, using pin prick test, for pain using visual analogue scale, and for the motor block using modified Bromage scale. During this period, if the visual analogue scale became greater than 3, the patient was administered paracetamol (1 g) intravenously three times daily, diclofenac sodium intramuscularly twice daily, and pethidine (50 mg) intramuscularly was administered once if the pain was not controlled.
Data management and analysis
On calculating the sample size for the study, it was found that 40 patients would be required in each group to achieve an a-error of 5% and a b-error of 1%. Thus, 40 patients in each group were considered sufficient for such data types.
The collected data were revised, coded, tabulated, and introduced to a computer using Statistical Package for Social Science (2001, SPSS 15.0.1 for Windows; SPSS Inc., Chicago, Illinois, USA). Data were presented and suitable analysis was carried out according to the type of data obtained for each parameter. Student's t-test was used to assess the statistical significance of the difference between two study group means. Mann-Whitney U-test was used to assess the statistical significance of the difference of a nonparametric variable between the two study groups. Wilcoxon rank sum test was used to compare nonparametric data between the two study groups. c2 -Test was used to examine the relationship between two qualitative variables. Fisher's exact test was used to examine the relationship between the two qualitative variables when the expected count was less than five in more than 20% of the cells. Correlation analysis was used to assess the strength of association between two quantitative variables. The correlation coefficient denoted symbolically that 'r' defines the strength and direction of the linear relationship between two variables.
| Results|| |
The patients in both groups were comparable regarding demographic data, ASA physical status, and comorbidities [Table 1].
The onset of the block was significantly shorter in group II [Table 2].
Regarding the duration of the sensory block, all patients in both groups were blocked at 6 h. At 12 h, the difference was highly significant where 77.5% of the patients in group I were blocked, whereas in group II 100% of the patients were blocked. At 24 h, the difference was statistically insignificant [Figure 1].
The motor block scale (MBS) showed nonsignificant difference at 6 h. At 12 h, there was a significant difference between the two groups. At 24 h, the difference was highly significant [Figure 2].
|Figure 2: Box plot comparing median (interquartile range) values of the motor block scale at different times in the two groups|
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Regarding the pain scale, the difference between the two groups was highly significant at 6 and 12 h. The difference was nonsignificant at 24 h [Table 3].
The complications among the two groups were comparable [Table 4].
In group I, the correlation between the age and the onset of the anesthesia revealed that, as age increased, the onset of the anesthesia was delayed [Figure 3]. The correlation between the age and the duration of the sensory block was not significant at 12 h; however, at 24 h, the correlation was significant, with a mean age of 30.4 years among those who were blocked and 40.7 years among those who were not blocked [Table 5]. The correlation between the age and the duration of the motor block showed that, at 24 h, there was a highly significant decrease in the MBS as age increased [Table 6].
|Figure 3: Linear proportional relationship between the age in years and the onset of the anesthesia in minutes among group I patients|
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|Table 5 Relationship between age and sensory block at different durations among group I patients|
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|Table 6 Correlation between age and motor block scale at different durations among group I patients|
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In group II, the correlation between the age and the onset of anesthesia was not significant [Table 7]. There was a highly significant difference between the age of patients who had sensory block and those with no sensory block at 24 h, but not at 6 or 12 h [Table 8]. The correlation between the age and the duration of the motor block was only significant at 24 h, as age increased the density of the block increased [Table 9].
|Table 7 Correlation between age and onset of anesthesia among group II patients|
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|Table 8 Relation between age and sensory block at different durations among group II patients|
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|Table 9 Correlation between age and motor block scale at different duration among group II|
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| Discussion|| |
Outpatient anesthesia has gained popularity nowadays. In outpatient anesthesia, the patient has to be alert, with no nausea and vomiting, and able to move to leave the unit  . In the outpatient setting, excessive reliance on opioids for postoperative analgesia can be associated with dizziness and nausea, which can delay discharge  . The use of local infiltration yields excellent analgesia without the adverse effects of opioids. Peripheral nerve blockade for upper and lower limb procedures provide intraoperative anesthesia and prolonged postoperative analgesia  .
On performing lower limb surgeries under nerve blocks, combined blocks are usually needed  . Combined sciatic-femoral nerve block is technically easy and it can be a possible choice for unilateral blockade of the lower limbs  . However, a transiently insensate extremity is a well-recognized effect of perineural LA injection  , and it is best minimized during continuous peripheral nerve blocks because insensate extremities may be liable for accidental injury  .
Little is known about the relative influence of LA volume versus concentration on peripheral nerve blockade in clinical practice  .
In our study, we investigated the effect of the volume on the duration of the motor block, aiming to study it as one of the factors that may affect the duration of the block and hence allow early ambulation of the patients.
The use of sufficient volumes of LA is an important requirement for the safe performance of regional anesthetic techniques  . The LA dose is the main factor affecting its peak plasma concentration and consequently its toxicity. To avoid this potentially fatal complication, decreasing the LA dose is of great importance  .
In this study, the onset of the block among the two groups was significantly different, where the onset in group II was significantly shorter than group I.
Regarding the duration of the sensory block, at 12 h, the difference was highly significant, as 100% of the patients were blocked in group II in comparison with 77.5% in group I, and at 24 h there was no significant difference.
This result is supported by a study by Pippa et al.  who has shown that increased volume of the LA has provided good analgesic cover. Our results also agree with Ilfeld et al.  who concluded that in continuous popliteal-sciatic nerve blocks, LA concentration, and volume affected block characteristics. Insensate limbs were more common with larger volumes of relatively diluted ropivacaine.
Regarding the motor block, the MBS showed a significant difference at 12 h between the two groups, as in group I the median was higher than in group II. At 24 h, the difference was highly significant among the two groups, where it was 2 for group I and 0.5 for group II.
Regarding the pain scale, the pain scale at 6 h was significantly higher in group I in comparison with group II. This was also the case at 12 h. At 24 h, there was no significant difference between the two groups.
These results showed that increasing the volumes with a fixed concentration provided a denser sensory block and a better pain satisfaction, whereas the motor block was less dense. These results were not investigated by any study before.
Regarding the correlation between the age and the onset of the anesthesia and the duration of the sensory and motor blocks, as age increased, the onset was delayed and the duration of the sensory and motor blocks decreased among group I patients, whereas, as the volume increased in group II, all these relations were abolished. This may signify that increasing the volume may obscure the other factors that may affect the block.
There are well-documented age-related physiologic alterations that occur in the central and peripheral nervous systems. Studies have shown that aging affects the anatomy, pharmacokinetics, and pharmacodynamics of LAs used in central neuraxial blockade  , and also affects the structural and functional properties of the peripheral nervous system. There is loss of both myelinated and unmyelinated nerve fibers  , potentially rendering the peripheral nerves more sensitive to LAs.
This study concluded that increasing the volume of the LAs hastened the onset of anesthesia, increased the duration, and the density of the sensory block.
Age-related physiologic changes in the central and peripheral nervous systems may have a direct effect on the clinical duration of peripheral nerve blocks. This finding needs to be further investigated.
| Acknowledgements|| |
Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9]