|Year : 2011 | Volume
| Issue : 1 | Page : 39-42
Effect of addition of fentanyl to local anesthetic in brachial plexus block on duration of analgesia
Shirish G Chavan, Alka R Koshire, Prasad Panbude
Department of Anaesthesia, NDMVPS Medical College, Nashik, Maharashtra, India
|Date of Web Publication||23-Aug-2011|
Shirish G Chavan
22, Senior Staff Quarter, NDMVPS Medical College, Vasantdada Nagar, Adgaon, Nashik
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Introduction/Context: A comparative study was carried out to evaluate the analgesic efficacy and side effects of addition of fentanyl to local anesthetic undergoing surgeries on forearm and elbow. All patients were hemodynamically stable, and there were no serious side effects in any of the patients in both the groups. The difference in the mean duration of analgesia between the groups was statistically significant (P<0.01). So we can conclude- Addition of Fentanyl to local anaesthetic in brachial plexus block increases duration of analgesia.
Materials and Methods: Patients were randomly divided into two groups: group I (control) and group II (study). All the patients were subjected to brachial plexus block with supraclavicular approach. After obtaining paraesthesia, drugs were administered as follows: Group I (control): bupivacaine 0.5% 20 mL + lignocaine 2% 10 mL + NS 1 mL Group II (study): bupivacaine 0.5% 20 mL + lignocaine 2% 10 mL + fentanyl 1 mL (50 microgm). Observations were noted. All the relevant information was recorded on a pretested, predefined, semi-open pro forma sheet. Regular monitoring of PR, BP and RR, side effects,degree of sedation were recorded. Evaluation of pain and pain relief was done according to McGill pain questionnaire (0- no pain to 5- excruciating pain). When patients complained of discomforting pain (McGill grade II), parenteral analgesic was prescribed, and the total number of doses in the 24-hour period was noted.
Results: The duration of analgesia in group II (study) was significantly longer (695±85 min) than those in group I (415±78 min). However, onset time of analgesia was prolonged in group 2. We conclude that the addition of fentanyl to local anesthetics causes an improved success rate of sensory blockade but a delayed onset of analgesia, although this may be accounted for by the decreased pH caused by fentanyl. There was no statistically significant difference in the incidence of side effects between the two groups.
Conclusions: This study has shown that the mean duration of analgesia is extended if fentanyl is added to local anesthetics, without increasing the side effects.
Keywords: Analgesia, brachial plexus, bupivacaine, fentanyl, lignocaine
|How to cite this article:|
Chavan SG, Koshire AR, Panbude P. Effect of addition of fentanyl to local anesthetic in brachial plexus block on duration of analgesia. Anesth Essays Res 2011;5:39-42
|How to cite this URL:|
Chavan SG, Koshire AR, Panbude P. Effect of addition of fentanyl to local anesthetic in brachial plexus block on duration of analgesia. Anesth Essays Res [serial online] 2011 [cited 2019 May 19];5:39-42. Available from: http://www.aeronline.org/text.asp?2011/5/1/39/84183
| Introduction|| |
One of the primary aims of anesthesia is to alleviate the patient's pain and agony, thereby permitting the performance of surgical procedures without any discomfort. Relief of intraoperative and postoperative pain has gained importance in recent years, considering the central, peripheral and immunological stress response to tissue injury. Any expertise acquired in this field should be extended into the postoperative period, which is the period of severe, intolerable pain requiring attention. So there is need of extended analgesia without any side effects in the process of achieving this goal.
The effects of opioids on regional blockade are controversial. The addition of opioids in brachial plexus block is reported to improve success rate and postoperative analgesia, by some authors, ,, whereasothers have found no effect. ,
Nowadays brachial plexus block is routinely used for upper extremity surgeries. Addition of fentanyl (1 μg/kg) to local anesthetic solution is useful to extend the period of analgesia. This study was carried out to study the effect of addition of 1 mL of fentanyl to bupivacaine (0.5%) 20 mL and lignocaine (2%) 10 mL on patients, with following aims and objectives.
| Materials and Methods|| |
Inclusion criteria: 1) ASA grade I to II, posted for operations on elbow, forearm and hand, elective as well as emergency. 2) Age group: 16 to 60 years. 3) Weight: 50 or >50 kg. 4) Sex: Male or female. 5) No known hypersensitivity to local anesthetic drugs and no history of coagulation disorder. 6) Patients who were ready to be included in the study and ready to give written consent.
Exclusion criteria: (1) ASA grades III, IV, V. (2) Age below 16 or above 60 years. 3) Patients who were not ready to be included.
Protocol was sent to local ethical committee and approval was obtained. If patients fulfilled inclusion criteria, they were explained about procedure, and written consent was obtained from them. Patients were randomly divided into two groups: group I (control) and group II (study). Sequential design was used for the study. All the patients were subjected to brachial plexus block with supraclavicular approach with all aseptic precautions with a 24-gauge needle, immediately lateral to subclavian artery. After obtaining paraesthesia, drugs were administered as follows: Group I (control): bupivacaine 0.5% 20 mL + lignocaine 2% 10 mL + NS 1 mL Group II (study): bupivacaine 0.5% 20 mL + lignocaine 2% 10 mL + fentanyl 1 mL (50 microgm).
Time of onset of sensory block, time of onset of motor block, duration of motor block and total duration of sensory block were noted. All side effects were also noted. Intraoperatively, all the patients received adequate intravenous fluids. Pulse rate (PR), blood pressure (BP), respiratory rate (RR) were monitored every 5 minutes till the patients were shifted from operating table. Patients were watched for signs of pneumothorax, like tachypnea and respiratory distress. Intraoperative monitoring was done for nausea, vomiting, itching, dryness of mouth and sweating.
After completion of surgery, patients were shifted to the recovery room. A person who was unknown to either of the groups observed the patients, till the patient got movements of fingers of blocked hand and/ or the patient complained about pain. All the relevant information was recorded on a pretested, predefined, semi-open pro forma sheet. All analgesics and sedatives were withheld in the postoperative period, unless the patient complained of pain (grade II). PR, BP and RR were recorded every 30 minutes for 24 hours. Side effects like nausea, vomiting, itching and respiratory depression as well as degree of sedation were noted in the postoperative period.
Evaluation of pain and pain relief was done according to McGill pain questionnaire (0- no pain to 5- excruciating pain). When patients complained of discomforting pain (McGill grade II), parenteral analgesic was prescribed, and the total number of doses in the 24-hour period was noted.
| Results|| |
The two groups were comparable with regard to mean age, sex and weight of the patients, all belonging to ASA I and II. Surgeries in both the groups were also comparable [Table 1]. Of the 100 patients recruited, 7 were withdrawn because of failure of the block.
Sensory and motor blockades were evaluated by using a pinprick technique and by measuring the gripping force, respectively. No patient complained of nerve deficit after surgery.
The time to onset of sensory blockade is shown in [Figure 1]. The addition of fentanyl to brachial plexus block prolonged the onset of analgesia (P=0.01). 
The durations of sensory blockade and analgesia in group II (study) were significantly longer (623±96 and 695±85 minutes, respectively) than those in group I (450±79 and 415±78 minutes, respectively).
The gripping forces significantly decreased 10 minutes after the injections, and there were no significant differences among the two groups [Table 2].
|Table 2: Duration of anesthesia and changes in gripping force after brachial plexus block|
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In a different set of experiments, the pH of local anesthetic solutions was measured. At room temperature, the pH was 6.2±0.1 (n=4). It was decreased to 5.2±0.1 (n=4) by adding 100 μg fentanyl.
However, onset time of analgesia was prolonged in distribution by adding fentanyl to brachial plexus block. We conclude that the addition of fentanyl to local anesthetics results in an improved success rate of sensory blockade but a delayed onset of analgesia, although this may be accounted for by the decreased pH caused by fentanyl.
There was no statistically significant difference in the time required for onset of complete motor block (P>0.05).
[Table 3] shows the incidence of various side effects in both the groups. There was no statistically significant difference in the incidence of side effects between the two groups. This study has shown that the mean duration of analgesia is extended if fentanyl is added to the local anesthetics, without increasing the side effects.
| Discussion|| |
This study demonstrated that the addition of fentanyl to bupivacaine 0.5% 20 mL+lignocaine 2% 10 mL brachial plexus block increased the success rate of sensory blockade and prolonged the duration of blockade.
However, the onset time of analgesia was prolonged by adding fentanyl to brachial plexus block. After comparision, we observed that there is remarkable increase in postoperative analgesia [Table 4]. Opiates have an antinociceptive effect at the central and/ or spinal cord level.  In animals, the presence of peripheral opioid receptors has been reported; ,, however, it is still unclear whether functional opioid receptors exist in human peripheral tissue. Several studies have attempted to determine whether the addition of opioids to local anesthetics would improve the efficacy of peripheral nerve blocks. Morphine and buprenorphine are reported to cause profound analgesia for brachial plexus block with or without local anesthetic. , Similar findings were observed with the perineural injection of morphine. 
Mays et al. reported that perineural morphine provided longer-lasting pain relief than did either intramuscular (IM) morphine or perineural bupivacaine in patients with chronic pain. Conversely, morphine and fentanyl were reported to have had no additional effect when they were added to axillary brachial plexus block. , Racz et al. observed that the addition of morphine to a local anesthetic solution (a mixture of plain lidocaine and plain bupivacaine) for axillary block changed neither the onset time nor the quality of postoperative pain relief. Fletcher et al. suggested that the addition of fentanyl to lidocaine with 1:200,000 epinephrine for axillary brachial plexus block produced no clinical benefit except for faster onset in the musculocutaneous nerve trunk. These conflicting results are probably caused by differences in opioids, anesthetics or techniques for nerve blockade. Most importantly, the lack of comparison between systemic and peripheral opioid administration would cause confusion as to the site of effect of the opioid.
In our study, the addition of fentanyl to local anesthetics for brachial plexus block improved the success rate of sensory blockade.
In contrast, Fletcher et al.  reported that no changes were observed in the success rate, onset time or duration of analgesia by axillary fentanyl administration. Because neither of these reports included an axillary fentanyl-alone group, it is rather difficult to evaluate the pure peripheral opioid receptor-mediated effect. However, local anesthetic is required to obtain surgical anesthesia. Fletcher et al.  used a nerve stimulator to localize the nerve plexus. Although a nerve stimulator is useful to accurately place the needle near the plexus, we did not use one to minimize irritation or discomfort. In addition, Fletcher et al.  did not mention the pH changes in their anesthetic solution. It is widely known that pH plays a role in the duration of onset of local anesthetics; , the changes in pH of an anesthetic solution can alter the quality of brachial plexus block.
These discrepancies may offer an explanation for the differences in results between their study and ours.
We postulate three possible mechanisms of action for the improved analgesia produced by the peripheral application of fentanyl.
First, fentanyl could act directly on the peripheral nervous system. Primary afferent tissues (dorsal roots) have been found to contain opioid-binding sites.  Because the presence of bidirectional axonal transport of opioid-binding protein has been shown,  fentanyl may penetrate the nerve membrane and act at the dorsal horn. This could also account for the prolonged analgesia. However, fentanyl is reported to have a local anesthetic action.  Gormley et al. suggested that alfentanil also prolonged postoperative analgesia by local anesthetic action.
However, it is unlikely that the small dose of fentanyl (50 μg) used in our present study could have a local anesthetic action, because a higher concentration (50 μg/mL) is required in vitro.
Second, fentanyl may diffuse from the brachial plexus sheath to epidural and subarachnoid spaces and then bind with the opioid receptor of the dorsal horn, but it is unclear from this study whether a sufficient dose of fentanyl diffused to the epidural or subarachnoid spaces to cause adequate analgesia. To clarify this issue, the spinal fluid fentanyl concentrations should be measured.
Third, fentanyl may potentiate local anesthetic action via central opioid receptor-mediated analgesia by peripheral uptake of fentanyl to systemic circulation.
In our study, the addition of fentanyl to local anesthetics caused a delayed onset of analgesia. We hypothesized that the changes in pH of anesthetic solutions could be responsible for this effect. The onset time of effect of local anesthetics is greatly influenced by the relative amounts of ionized and nonionized forms present. Only the nonionized form of lignocaine can diffuse through interstitial tissues and nerve membranes. The fraction of the nonionized lignocaine is increased by elevating the pH. Kanaya et al. reported that alkalinized lignocaine solution for brachial plexus block caused a faster onset of analgesia. In the present study, the pH of lignocaine solution was decreased from 6.2 to 5.2 by the addition of fentanyl. This may have reduced the rate of penetration of lignocaine into the nerve membrane, resulting in the slower onset of analgesia.  To confirm this hypothesis, further studies are required comparing the effects of fentanyl on brachial plexus block when using solutions with different pH levels.
| Conclusion|| |
The addition of small-dose fentanyl to lignocaine solution in brachial plexus block can increase the success rate and prolong the duration of analgesia,  but it delays the onset time of sensory blockade as compared with that achieved by the same doses of local anesthetics used in combination.
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[Table 1], [Table 2], [Table 3], [Table 4]