Comparison of Intrathecal Clonidine and Fentanyl as Adjuvant to Hyperbaric Bupivacaine in Subarachnoid Block for Lower Limb Orthopedic Surgery.

BACKGROUND: Many studies are there using adjuvants such as clonidine and fentanyl with bupivacaine in the subarachnoid block for prolonging postoperative analgesia. However, literature is divided regarding the dosage and efficacy of both intrathecal adjuvants. Furthermore, these adjuvants have their own side effects. Hence, search for ideal intrathecal adjuvant between clonidine and fentanyl to bupivacaine goes on. AIM: The aim of the present study was to compare the effect of intrathecal clonidine and fentanyl as adjuvant to bupivacaine in the subarachnoid block for lower limb orthopedic surgery.
MATERIALS AND METHODS: It was a prospective randomized study in which eighty patients posted for lower limb orthopedic surgery were divided into two groups of forty each. Group C - Received intrathecal hyperbaric bupivacaine (2.5 ml) +50 μg clonidine (diluted to 0.5 ml). Group F - Received intrathecal hyperbaric bupivacaine (2.5 ml) + fentanyl 25 μg (diluted to 0.5 ml). Duration of postoperative analgesia, sensory and motor block characteristics, hemodynamic parameters, and side effects were recorded and analyzed.
RESULTS: Time for first dose of rescue analgesic was delayed in Group C (510.84 ± 24.10 min) in comparison to Group F (434.95 ± 19.16 min) which was statistically significant (P < 0.001). Duration of sensory and motor block was significantly prolonged in Group C compared to Group F (P < 0.001). Sedation was more in Group C than Group F (P < 0.001). Other block characteristics, hemodynamic, and side effects were comparable in both groups.
CONCLUSION: Intrathecal clonidine as adjuvant to hyperbaric bupivacaine provided prolonged postoperative analgesia with more sedation in comparison to intrathecal fentanyl.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Local anesthetic like bupivacaine is commonly used in spinal anesthesia, but the duration of spinal anesthesia may be short and limited, and higher doses of rescue analgesics may be required in the postoperative period. This can be avoided by using higher doses of bupivacaine which again can produce cardiac toxicity. Studies have shown that duration of analgesia due to bupivacaine in spinal anesthesia can be prolonged by using adjuvants such as midazolam, opioids, neostigmine, dexmedetomidine, and clonidine.[1] Almost all opioids have been used as adjuvants intrathecally.

Most commonly used opioid in regional anesthesia is fentanyl citrate which is a μ1- and μ2-receptor agonist. It is a highly potent drug because of its high lipophilicity. It is preferred as an adjuvant in spinal anesthesia because of its rapid onset and short duration of action with minimal cephalic spread.[23] However, pruritus, nausea, vomiting, respiratory depression, and urinary retention are other common side effects for which search for ideal nonopioid adjuvants goes on.[4] Clinical studies have suggested that intrathecal clonidine, an α2-receptor agonist, prolongs sensory and motor block in spinal anesthesia and provides prolonged postoperative analgesia. Clonidine has beneficial effects such as antiemesis, reduced postspinal shivering, anxiolysis, and sedation, thereby avoiding unwanted opioid-related side effects such as pruritus and respiratory depression.[56]

Literature is divided regarding efficacy of both intrathecal clonidine and fentanyl in providing prolonged postoperative analgesia. Studies by Khezri et al.,[7] Bajwa et al.,[8] Chhabra et al.,[9] and Sharan et al.[10] opined that intrathecal clonidine was more potent in providing prolonged analgesia compared to intrathecal fentanyl. Study by Mahendru et al. concluded that intrathecal fentanyl and clonidine were comparable regarding requirement of first analgesia request.[11] Another study by Bathari et al. concluded that intrathecal fentanyl was superior to intrathecal clonidine in knee arthroscopy.[12] Hence, all the above studies differ in their postoperative sensory and motor block characteristics. Hence, the present study is being undertaken to evaluate and compare the effects of clonidine and fentanyl as intrathecal adjuvants to hyperbaric bupivacaine in patients undergoing lower limb orthopedic surgery. The primary objectives of this study were to evaluate and compare the effects of clonidine and fentanyl on time of request of first dose of rescue analgesic. Secondary objectives were to compare the effects of clonidine and fentanyl on time of onset and duration of sensory and motor block, hemodynamic status, and side effects.

MATERIALS AND METHODS

This randomized controlled study was carried out from January 2016 to January 2017, after obtaining approval from the Hospital Ethics Committee and written informed consent from the patients. Eighty patients of the American Society of Anesthesiologists Classes I or II of either sex and of age 20–60 years of age posted for lower limb orthopedic surgery were randomly divided into two groups (n = 40) using computer-generated program. Assigned random group was enclosed in a sealed envelope to ensure concealment of allocation sequence. The anesthesiologist, who was not involved in the study, opened the envelope in operation theater and prepared the drug accordingly. The observation was done by the anesthesiologist who was blinded to the drug. Patients having severe systemic disorders such as diabetes mellitus, hypertension, heart disease, allergy to bupivacaine, spine deformity, increased intracranial pressure, neurological disorders, hemorrhagic diathesis, and infection at the puncture site were excluded from the study. Group C – Received hyperbaric bupivacaine (2.5 ml) +50 μg clonidine (diluted to 0.5 ml) administered intrathecally. Group F – Received hyperbaric bupivacaine (2.5 ml) + fentanyl 25 μg (diluted to 0.5 ml) administered intrathecally. Total volume of study drug was 3 ml. Preanesthetic checkup was done, and visual analog scale (VAS) was explained to all patients. All the patients were kept nil orally for 6 h before surgery. After shifting the patients to operation theater, intravenous (IV) cannula was inserted, and preloading was done with Ringer solution (10 ml/kg). Preoperative parameters such as pulse rate, oxygen saturation, and blood pressure were recorded. Under all aseptic precaution, spinal anesthesia was administered at the level of L3–L4 intervertebral space in sitting position using midline approach by 25-gauge Quincke spinal needle. The anesthesiologist who administered anesthesia was blinded to the group allocation. Pulse rate, respiratory rate, electrocardiogram, SpO2, and blood pressure were monitored. Pulse rate and blood pressure variations more than 20% of baseline were noted in both groups. Bradycardia and hypotension were treated with IV atropine and ephedrine, respectively. Sensory and motor block was monitored at 2, 4, 6, 8, 10, 15 min, and after that at 15 min interval. Sensory block was tested by pinprick method. The motor block was assessed according to the modified Bromage scale: Bromage 0: Patients able to move hip, knee, and ankle, Bromage 1: Patients unable to move hip but able to move the knee and ankle, Bromage 2: Patient unable to move hip and knee but able to move the ankle, Bromage 3: Patient unable to move hip, knee, and ankle.[8] The onset of sensory block was taken from the time of intrathecal injection till loss of pin prick sensation at T10. Duration of sensory block was taken as time from maximum height of block till regression to Level 1. The onset of motor block was defined as time from intrathecal injection to motor blockade Level 2 in Bromage scale. Duration of motor blockade was taken as time from intrathecal injection till no motor weakness (Bromage 0). Duration of analgesia was defined as time from intrathecal injection till administration of first rescue analgesic. Any side effects such as nausea, vomiting, pain, shivering, pruritus, sedation, hypotension, bradycardia, and respiratory discomfort were noted. Patients were assessed for degree of sedation, and scoring was done with Campbell sedation score as: 1: Wide awake, 2: Awake and comfortable, 3: Drowsy and difficult to arouse, and 4: Not arousable.[8] Postoperatively, the pain score was recorded by using VAS between 0 and 10 (0 = no pain, 10 = severe pain).[9] Injection paracetamol (1 gm) was given intravenously as rescue analgesic when VAS was >5. Time of administering the first dose of rescue analgesia was noted.

Power analysis suggested that a sample size of forty patients per group was required to achieve a power of 80% and a level significance of 0.05 to be able to detect a difference in the mean duration of analgesia by 60 min between the groups. Interpretation of the data was carried out and analyzed using statistical package for social sciences (SPSS version 19, IBM Corp, NY, USA). Data was represented as mean ± standard deviation for continuous data and frequency (percentage) or median (range) for nonparametric (categorical) data. The two groups were compared using analysis of variance. The proportion of adverse effects was compared using Chi-square test. P < 0.05 was considered statistically significant. P < 0.001 was considered highly statistically significant.

RESULTS

Both groups were comparable with respect to their demographic profile, baseline hemodynamic parameters, and duration of surgery [Table 1].

Table 1

Baseline characteristics of the study population

Table 2 compares onset and duration of sensory and motor block and duration of postoperative analgesia. Time for first dose of rescue analgesic was delayed in Group C (510.84 ± 24.10 min) compared to Group F (434.95 ± 19.16 min) which was statistically significant (P < 0.001). Duration of sensory block in Group C was 250.52 ± 18.41 min compared to 205.16 ± 19.55 min in Group F which was statistically significant (P < 0.001). Duration of motor block was 190.19 ± 26.11 min in Group C in comparison to 171.31 ± 24.58 min in Group F which was statistically significant (P < 0.001). There was no statistical difference in onset of both sensory and motor block between the two groups (P > 0.05). There was also no significant difference regarding hemodynamic parameters such as systolic blood pressure, diastolic blood pressure, mean arterial pressure, and heart rate [Graphs 1–4].

Table 2

Comparison of different block characteristics

Graph 1

Change in systolic blood pressure

Graph 4

Change in heart rate

Change in diastolic blood pressure

Change in mean arterial blood pressure

In Group C, sedation score ≥3 was found in nine patients compared to none in Group F which was statistically significant (P < 0.001). There was no significant difference in both groups regarding other side effects [Graph 5].

Graph 5

Comparison of side effects

DISCUSSION

Clonidine is an α2-agonist which block the conduction of Aδ and C fibers, thereby prolongs the action of local anesthetics. When used intrathecally, it activates the postsynaptic α2-receptors in substantia gelatinosa of spinal cord and produces analgesia.[1314] We have used intrathecal clonidine with bupivacaine to see whether it provides prolonged analgesia, avoiding side effects of fentanyl. In our study, we found that intrathecal clonidine as adjuvant to bupivacaine provided prolonged analgesia compared to intrathecal fentanyl. Khezri et al. in their study concluded that intrathecal clonidine 75 μg with bupivacaine prolonged the time to first analgesia request compared to fentanyl which was similar to our study.[7] Bajwa et al. in their study concluded that addition of clonidine (50 μg) to intrathecal bupivacaine provided prolonged postoperative analgesia in comparison to fentanyl (25 μg), but clonidine provided more sedation.[8] We have found similar finding in our study. Chhabra et al. in their study concluded that clonidine 60 μg has advantage over fentanyl and it prolonged the duration of the subarachnoid block and postoperative analgesia, similar to our study.[9] Sharan et al. compared intrathecal clonidine 30 μg with fentanyl 25 μg and concluded that clonidine had advantage over fentanyl which is in agreement with our study.[10] However, Mahendru et al. in their study opined that intrathecal 30 μg clonidine is comparable to 25 μg fentanyl regarding sensory and motor block characteristics which was not in agreement with our study.[11] Bathari et al. in their study concluded that intrathecal fentanyl 30 μg was superior to intrathecal clonidine15 μg in knee arthroscopy which was not in agreement with our study.[12] This may be due to the use of low dose of intrathecal clonidine and high dose of intrathecal fentanyl. Benhamou et al. demonstrated higher spread and prolonged postoperative analgesia in lower limb surgery by adding 75 μg of clonidine to intrathecal bupivacaine, and the side effects were not increased with this dose. In our study, intrathecal addition of 50 μg clonidine to bupivacaine produced longer duration of postoperative analgesia with minimal side effects.[15] Lavand’homme et al. showed higher incidence of hypotension and sedation with intrathecal clonidine 150 μg than clonidine 75 μg.[16] The dose of clonidine was limited to 50 μg in our study to decrease the side effects. Kothari et al. compared different doses of clonidine as an adjuvant to intrathecal bupivacaine for spinal anesthesia in patients undergoing cesarian section aiming to find out the lowest possible effective dose and found that the incidence of both hypotension and bradycardia more in bupivacaine group than in bupivacaine with clonidine group which was not in agreement with our study.[17] Bhure et al. demonstrated that addition of clonidine, fentanyl, and midazolam to bupivacaine significantly improves the onset and duration of sensory and motor block with relative hemodynamic stability, prolongs the duration of analgesia, and reduces the consumption of systemic analgesics in comparison to bupivacaine alone. They concluded that clonidine is an excellent additive to bupivacaine in spinal anesthesia and provides prolonged duration of analgesia without any deleterious effects on the mother and baby.[18] Tilkar et al. conducted a prospective study to differentiate between the effects of fentanyl versus clonidine when added to intrathecal bupivacaine in spinal anesthesia. They concluded that addition of intrathecal clonidine to hyperbaric bupivacaine was more advantageous than fentanyl with special regard to its analgesic properties.[19] Singh et al. evaluated the effect of addition of intrathecal clonidine to hyperbaric bupivacaine on postoperative pain after caesarean section and has shown that the duration of postoperative analgesia increases significantly on adding 75 μg clonidine to 2 ml of hyperbaric bupivacaine without any increase in maternal side effects. There was no effect on neonatal outcome. Finding of this study was similar to ours.[20] Shidhaye et al. concluded that intrathecal addition of 25 μg fentanyl to bupivacaine provides good analgesia with less sedation and is a better option when sedation is not desirable. However, intrathecal addition of 60 μg clonidine to bupivacaine provides longer duration of postoperative analgesia than 25 μg of fentanyl and is a preferred option when sedation is acceptable.[21] Bhattacharjee et al. concluded from their study that perioperative analgesia for cesarean section was prolonged by the addition of 75 μg of clonidine and 25 μg fentanyl to bupivacaine. However, prolongation of postoperative analgesia was more with fentanyl compared to clonidine, and side effects such as nausea, vomiting, and hypotension were more with clonidine.[22] This study is not in agreement with our study. Kaur et al. evaluated intrathecal bupivacaine-clonidine combination in lower abdominal surgeries and concluded that intrathecal clonidine 150 μg added to bupivacaine not only fastens onset of sensory and motor block but also prolongs the duration of the same, thereby decreasing the rescue analgesic requirement which is in agreement with our study. However, sedation and bradycardia were more with clonidine 150 μg.[23] Several other studies had opined that intrathecal clonidine is an ideal adjuvant which provided prolonged analgesia with minimal side effects.[24252627] These are in agreement with findings in our study. Singh et al. in their study in patients posted for transurethral resection of prostate concluded that intrathecal clonidine in a combination with bupivacaine provides more satisfactory anesthesia and analgesia and has less side effects compared to fentanyl which was similar to our finding.[28] All above studies have used intrathecal clonidine in doses from 15 μg to 150 μg, but use of intrathecal clonidine in dose of 50 μg provided prolonged postoperative analgesia with minimum side effects compared to fentanyl and other different doses of clonidine.

CONCLUSION

Intrathecal clonidine (50 μg) when added to bupivacaine in spinal anesthesia provides prolonged duration of postoperative analgesia than 25 μg of fentanyl but with higher degree of sedation. Fentanyl (25 μg) may be recommended as a better option when sedation is not desirable.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.