A comparative study of efficacy of fentanyl and dexmedetomidine as adjuvants to bupivacaine in spinal anesthesia for infra umbilical surgeries

 

 

Abstract               Background: To assess the effect of adding adjuvants such as dexmedetomidine or fentanyl to intrathecal bupivacaine for regional analgesia and to compare the efficacy of dexmedetomidine to fentanyl. Methods: Hundred patients were studied between 2014 to 2017 at SVS Mahbubnagar were assigned to two groups, fentanyl was given as adjuvant to intrathecal bupivacaine in group I and Dexmedetomidine was used as an adjuvant in group II, onset of sensory block, motor block, prolongation of analgesia and post-operative side effects were assessed. Results: Mean Time from injection to T10 2.62±0.56 in dexmedetomidine group was significantly less in comparison to 3.38±0.83 in fentanyl group. Regression to bromage was 419.70±16.85, significantly higher in group II compared to group I 152.90±8.31 p <0.05. Mean VAS was significantly less in group II compared to group I starting at 6 hours and up to 24 hrs post-operative period. Conclusion: 5 µg Dexmedetomidine observed to be a good alternative to 25 µg Fentanyl as an adjuvant to intrathecal bupivacaine in infra umbilical surgical procedures as it delivers good quality of intraoperative analgesia, hemodynamically stable condition with minimal side effects, and excellent quality of postoperative analgesia.

Key words: Regional Anesthesia, bupivacaine, dexmedetomidine, adjuvants efficacy

 

INTRODUCTION

Spinal anesthesia is the most preferred regional anesthesia technique as it is easier to perform, economical and results in rapid onset of anesthesia with complete muscle relaxation ¹. The aim of intrathecal local anesthetic is to maintain adequate sensory and motor block necessary for all infra umbilical surgeries.² Hyperbaric Bupivacaine is by far the commonly used intrathecal local anesthetic.³ To avoid any side effects due to higher doses of local anesthetics and to improve the efficacy of blockade adjuvants are commonly used during regional anesthesia.² Adjuvants medications have been added to Bupivacaine to shorten the onset of block and prolong the duration of block and provide adequate post-operative analgesia. Fentanyl, is a lipid soluble opioid agonist used as an adjuvant, it prolongs the duration of spinal block thereby improving the spinal anesthesia and decreases the side effects with local anesthetic solution.⁴ Dexmedetomidine, an α–2 agonist drug, when given through intrathecal route, provides good sedative, analgesic, anxiolytic and anesthesia sparing effects, use of this drug as an adjuvant significantly lengthens the duration of spinal block.⁵ Therefore, in the present study aims is to evaluate the efficacy of 25μg of Fentanyl and 5μg Dexmedetomidine as adjuvants to 0.5% Bupivacaine heavy when administered intrathecally in infra-umbilical surgeries. The efficacy of the adjuvant medications is assessed in terms of speed of onset, duration of motor block, intra operative sedation, post-operative pain and complications such as nausea, vomiting, hypotension, shivering, pruritus, seizures and respiratory depression.

 

 

MATERIAL AND METHODS

After obtaining approval from institutional ethics committee and informed consent from patients, 100 patients between the age group of 18 – 65 years and with ASA I and II, scheduled for major surgeries under spinal anaesthesia were randomly selected during the preanesthetic checkup from department of anaesthesia, S.V.S Medical college Hospital. Patients were evaluated for any systemic diseases and laboratory investigations recorded. Patients with any deformity of spine, hypersensitivity to drugs contraindication to spinal anaesthesia, end organ involvement and patients who have not provide consent were excluded from the study. Patients were prepared with overnight fasting and premedication with ranitidine 150 mg and alprazolam 0.5 mg. The patients were divided randomly into two groups, group I (0.5 % hyperbaric Bupivacaine + fentanyl group ) and Group II (0.5 % hyperbaric Bupivacaine + dexmedetomidine) consisting of 50 patients each. After recording the baseline vitals, under strict asepsis lumbar puncture was done, group I received 3ml of 0.5 % hyperbaric Bupivacaine + 25 µg fentanyl group, group II received 3ml of 0.5 % hyperbaric Bupivacaine + 5 µg Dexmedetomidine. Intraoperatively pulse rate, non-invasive blood pressure, electrocardiogram, SpO2 was recorded, every 2 minutes during the first 10 minutes, every 10 minutes for the next 50 minutes and every 15 minutes till the end of surgery. Time of onset of T10 sensory block and peak sensory block was noted using pin prick method and time of onset of Bromage 3 motor block was also recorded. Occurrence of hypotension, brady cardia, respiratory depression was also recorded. During the post-operative period regression of sensory block and the motor blockade to reach modified Bromage 0 was recorded and postoperative pain was evaluated using Visual analog scale.

 

OBSERVATION AND RESULTS

Data obtained was entered in excel, statistical tests such as Chi-square test, Anova test and students ‘t’ test was used to asses the efficiency of fentanyl versus Dexmedetomidine as adjuvant to bupivacaine. Significance (p value) < 0.05 was considered as significant In the present study there was no statistically significant difference observed in mean age, gender, height, weight and ASA grading in group I compared to group II (Table I). there was no significant difference observed in the pattern of surgeries performed in both the groups p>0.05 (Table II). 38 % surgeries were obstetrics followed by 32 % orthopedic surgeries, 18 % general surgeries and 12 % were urology surgeries in the group I, compared to 38 % obstetric surgeries 28 % orthopedic surgeries, 22 % general surgeries and 12 % were urology surgeries in the group II, There was no statistically significant difference in the heart rate in between groups P >0.05. there was a significant decrease in the mean SBP at 2 mins and 90 mins in group II compared to group I, no change in SBP was observed in between groups at other time. Significant decease in the DBP was observed in group I at 10 mins, 20 mins and 40 mins, there was no change in DBP observed in between groups at other time. Time from injection and T10 minutes was significantly lower in Group II compared to Group I, there was no statistically significant difference in the time from injection to highest sensory level and onset of Bromage in either of the groups. Regression to bromage was significantly higher in group II compared to group I p <0.05. Highest sensory level of the patient studies was observed to be T8 in 38 % of group II followed by T6 in 28 % cases and T4 in 28 % cases when compared to T6 in 32 % cases followed by T4 in 30 % and T7 in 24 % cases there was a significant difference observed in the groups p <0.05. There was no significant change observed in the respiratory rate and SPo2 in the present study. Occurrence of nausea was seen in 6% of group I patients, pruritus was seem in 6 % group I cases. There was no incidence of nausea or vomiting in the group II cases. Hypotension was seem in 28 % group I compared to 16 % group II patients. 14 % patients in group II had bradycardia. There was no incidence of respiratory depression or urinary retention in the present study. Mean VAS was significantly less in group II compared to group I starting at 6 hours and up to 24 hrs post-operative period p <0.05 The mean sedation score was observed to be significantly lower than group II at 60 mins, 90 mins and 120 mins p <0.05.

 

Table I: Demographics

 

 

Table II: Type of Surgeries

 

Table III: Comparison of Time of Injection to T10, Highest sensory level, onset of Bromage 3 and regression to Bromage 0

 

Table IV: Comparison of Side Effects

 

Table V: Visual analog score for Pain perception

 

Table VI: Comparison of Mean Sedation score in between groups

 

DISCUSSION

Spinal anesthesia is the most favored regional anesthesia technique since it is easy to perform, provides rapid onset of anesthesia and complete muscle relaxation and is also economical. These advantages are sometimes counterbalanced by a relatively short duration of action ^1,2. The aim of intrathecal local anesthetic is to provide adequate sensory and motor block necessary for all infra umbilical surgeries. Hyperbaric Bupivacaine is the widely used intrathecal local anesthetic ³. Various adjuvant medications have been added to intrathecal Bupivacaine so as to decrease the onset of block and prolong the duration of block ^4,5.In our study design Group I received 0.5% of hyperbaric Bupvacaine 3ml with Fentanyl 25µg and Group II received 0.5% hyperbaric Bupivacaine 3ml with Dexmedetomidine 5 µ gms, injected intrathecally in 100 patients undergoing infra umbilical surgeries belonging to ASA grade I and II. Time of onset of block, attaining the highest level of sensory and motor blockade, time of bromage 0, intra operative heart rate, blood pressure, spo2, intra operative sedation, regression to bromage 3 and post-operative analgesia requirement was assessed. Our study has shown that the addition of 5 µg Dexmedetomidine with hyperbaric Bupivacaine significantly extends both sensory and motor block. Both Fentanyl and Dexmedetomidine provided good quality intraoperative analgesia. The analgesia was observed to be clinically better in group II as compared to group I. when small doses of intrathecal Dexmedetomidine (3µg) was used with Bupivacaine, studies have demonstrated that the combination not only shortens the onset of motor block but also prolong the duration of motor and sensory block, augmenting the hemodynamic stability and avoiding sedation ^6,7 In the Dexmedetomidine group there was longer duration of both sensory and motor blockade and good patient satisfaction in present study, our findings confirm with the previous studies where it was reported that 5 µg Dexmedetomidine produces more extended motor and sensory block in comparison to 25 µg Fentanyl ⁸ .Use of Dexmedetomidine 5µg and 10 µg as a combination drug with Bupivacaine in urological procedures it was also reported that duration of spinal anesthesia in a dose-dependent manner with Dexmedetomidine. Visceral pain usually occurs follows abdominal surgeries performed under spinal anesthesia. Intrathecal Fentanyl when added to local anesthetics was observed to alleviate the visceral and somatic pain⁹ . In our study visceral pain was not reported in either of the groups. The mean VAS scores for group II was seen to be significantly lower than group I suggesting longer analgesia with dexmedetomidine compared to fentanyl. In the present study, postoperative analgesic requirements was significantly less in the Dexmedetomidine group than Fentanyl group. The mean sedation score for group I was 2.16 ± 0.37 which was significantly lower than and group II was 3.40 ± 0.49, which was statistically significant ( p <0.001). Respiratory depression was not reported in either of the groups. Hemodynamic stability and reduced demand for analgesics was also reported in concordance with the previous studies ^10,11. In the present study there was faster onset upto T10 level in group II 2.62±0.56 compared to Group I 3.38±0.83 the findings were comparable to previous studies ¹². The benefit of Dexmedetomidine over fentanyl is that it facilitates in better spread of the block and offers extended post-operative analgesia compared to fentanyl ¹³. In present study bradycardia was seen was more in Dexmedetomidine group compared to fentanyl group. Nausea and vomiting were higher in fentanyl group and least in Dexmedetomidine group. It was also not statistically significant on analysis(p>0.05). studies have reported Dexmedetomidine to have minimal side effects, and preeminence in quality of postoperative analgesia compared to Fentanyl which was not in agreement with our study ¹⁴. In our study none of the groups demonstrated any adverse effect on respiratory rate or decrease in O2 saturation. The findings were similar to other studies demonstrated that intrathecal administration of Fentanyl 25μg in non premedicated geriatric patients did not alter respiratory rate, ETCO2, minute ventilation, respiratory drive and ventilator response to CO2. On the contrary, 50µg intrathecal Fentanyl can cause an early respiratory depression in geriatric patients ¹⁵.

CONCLUSION

Addition of 5 µg Dexmedetomidine with hyperbaric Bupivacaine significantly prolongs both sensory and motor block. There was less incidence of side effects with Intrathecal Dexmedetomidine when compared to Intrathecal fentanyl .The post operative 24 hours analgesic requirements was significantly less in the Dexmedetomidine group than group Fentanyl .To conclude, 5 µg Dexmedetomidine seems to be an attractive alternative to 25 µg Fentanyl as an adjuvant to spinal bupivacaine in surgical procedures as it provides good quality of intraoperative analgesia, haemodynamically stable condition with minimal side effects, and excellent quality of postoperative analgesia.

 

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