Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 9  |  Issue : 2  |  Page : 256-259

Dexmedetomidine and sodium bicarbonate as adjuvants to epidural lidocaine: A comparative study


Department of Anaesthesiology, NRI Medical College, Guntur, Andhra Pradesh, India

Date of Submission06-Jan-2015
Date of Acceptance16-Aug-2015
Date of Web Publication11-May-2016

Correspondence Address:
Srivishnu V Yallapragada
Department of Anaesthesiology, NRI Medical College, Chinnakakani, Guntur 522 503, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1687-7934.179899

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  Abstract 

Context
Efforts to find a better adjuvant in regional anesthesia have been underway since long. Dexmedetomidine and sodium bicarbonate have been proven to be effective in providing the same pharmacological benefit through two different mechanisms of action. In this study, we sought to investigate which is superior between the two.
Aims
The aim of the study was to compare the efficacy of dexmedetomidine and sodium bicarbonate as adjuvants to lidocaine in epidural anesthesia.
Settings and design
This was a prospective, randomized, double-blind study.
Materials and methods
Sixty patients scheduled for lower-limb trauma orthopedic surgeries under epidural anesthesia were divided into two groups group D and group S, with 30 patients in each. Patients in group D received 12.5 ml of 2% lidocaine+dexmedetomidine 0.5 mg/kg in 1.5 ml solution, making a total volume of 14 ml. Patients in group S received 12.5 ml of 2% lidocaine+1.5 ml of 7.5% sodium bicarbonate, making a total volume of 14 ml. Onset, time for peak sensory level, time for two-segment regression, and the total mephentermine consumed to maintain the hemodynamics were recorded, tabulated, and statistically analyzed.
Results
The onset of sensory block was quicker in group D. The time for attaining peak sensory level and the mephentermine consumption was nearly the same in both groups. The time for two-segment regression was more in group D than in group S.
Conclusion
Dexmedetomidine is more effective than sodium bicarbonate in hastening the onset and prolonging the duration of blockade when used as an adjuvant to epidural lidocaine.

Keywords: adjuvant lidocaine, dexmedetomidine, sodium bicarbonate


How to cite this article:
Yallapragada SV, Vutukuri GK, Vemuri NN, Shaik MS. Dexmedetomidine and sodium bicarbonate as adjuvants to epidural lidocaine: A comparative study. Ain-Shams J Anaesthesiol 2016;9:256-9

How to cite this URL:
Yallapragada SV, Vutukuri GK, Vemuri NN, Shaik MS. Dexmedetomidine and sodium bicarbonate as adjuvants to epidural lidocaine: A comparative study. Ain-Shams J Anaesthesiol [serial online] 2016 [cited 2021 Apr 21];9:256-9. Available from: http://www.asja.eg.net/text.asp?2016/9/2/256/179899


  Introduction Top


Interruption of pain is central to anesthetic practice. Development of epidural analgesia has played a significant role in man's triumph over pain, which undoubtedly is one of the most fascinating chapters in the history of medicine. The onset, duration, and quality of neuraxial blockade in epidural anesthesia depend on the type of local anesthetic agent used and are significantly influenced by the addition of an adjuvant. Efforts to find a better adjuvant in regional anesthesia have been underway since long. Sedation, stable hemodynamics, and an ability to provide smooth and prolonged postoperative analgesia are the main desirable qualities of an adjuvant in neuraxial anesthesia. a-2-Adrenergic receptor (AR) agonists have been the focus of interest for their sedative, analgesic, perioperative sympatholytic, anesthetic sparing, and hemodynamic stabilizing properties [1,2]. Dexmedetomidine is a highly selective a-2-AR agonist having all the said properties and is devoid of respiratory depression [3,4]. In anesthetic practice, there has been considerable interest in the effect of pH on the onset, potency, and duration of blockade of local anesthetics. It is said that alkalinization of the local anesthetic improves the quality of block by influencing the portioning coefficient of anesthetic between aqueous solution and biological membranes [5]. Thus, in this study we sought to evaluate the efficacy of dexmedetomidine and sodium bicarbonate as adjuvants to lidocaine in epidural anesthesia.


  Objectives Top


The aim of the study was to compare dexmedetomidine and sodium bicarbonate as adjuvants to epidural lidocaine in terms of onset of sensory block, time for attaining peak sensory level, time for two-segment regression from the peak level, and requirement of vasopressor.


  Materials and methods Top


Approval from the institutional ethics committee was obtained before starting the study. Written informed consent was obtained from all patients who were enrolled in the study. In this randomized, double-blinded prospective study, all adult patients belonging to American Society of Anesthesiologists status 1 or 2 with recent (<48 h) lower-limb trauma scheduled for orthopedic surgeries from January 2013 to December 2013 performed in NRI General Hospital & Medical College, Chinnakakani, Guntur District, Andhra Pradesh, India, were included. Patients with gross spinal abnormality, localized skin infection, neural disease, severe valvular heart disease, shock, hypertension, diabetes mellitus, pulmonary/hepatic/renal diseases, peripheral neuropathy, psychiatric disorders, coagulation abnormalities, and dysrhythmias and patients on b-blockers were excluded from the study. Patients were randomly allocated into two groups, D and S, using a computer-generated randomization program. In the operating room, after connecting standard monitors and securing intravenous access, baseline blood pressure and heart rate were recorded and preloading was done with 500 ml crystalloid solution. The epidural space was engaged in the sitting position in the L4-L5/L3-L4 intervertebral space with an 18 G Tuohy needle using 'loss of resistance to air' technique under strict aseptic precautions. A 20 G epidural catheter was threaded and fixed at 3-5 cm in the epidural compartment after excluding intravascular and intrathecal placement by giving a test dose with 2% lidocaine with adrenaline (1 : 200 000). Patients in group D received 12.5 ml of 2% lidocaine+dexmedetomidine 0.5 mg/kg in 1.5 ml solution, making a total volume of 14 ml. Patients in group S received 12.5 ml of 2% lidocaine+1.5 ml of 7.5% sodium bicarbonate, making a total volume of 14 ml. The study drugs were drawn by an anesthetist who was blinded to the study, and were coded and handed over to another anesthetist who was blinded to the drug for administration. After administering the drug, the time point when the pain at movement of the fracture site disappeared was taken as the time of onset of sensory block. The peak sensory level attained was recorded with a pinprick, and the time was documented. The time for two-segment regression from the peak sensory block was also recorded. Mean arterial pressure and heart rate were documented every 5 min. Hypotension of more than 20% of the baseline was treated with 6 mg boluses of intravenous mephentermine, and the total consumption was documented. All observations were tabulated and analyzed statistically.

Statistical analysis

The overall power of the study was calculated using 'Online Power and Sample Size Calculator for K Means'. Power of the study for comparison between two groups was calculated using an online power calculator for difference between two means. Summarization of data was done with the help of measures of central tendency and dispersion (mean and SD). Differences in average values of different parameters under study were calculated with the help of a t-test of difference between two independent sample means. The Z-test of proportions was used to test the differences in proportions of male and female patients between the groups. The t-test and Z-test were performed with the help of the 'In-Silico Project Support for Life Sciences Online Calculator'. Data are presented in the form of tabular and graphical representation. The critical P-value was taken as 0.05, above which is the area of rejection.


  Results Top


A total of 67 patients were enrolled in the study, out of which three patients encountered accidental dural puncture, one patient refused, and three patients were excluded because of failure of epidural anesthesia. Thus, 60 patients were included in the study, with 30 in each group. Power of the study for the said sample size was calculated to be 99%. The demographic profile was comparable between the two groups [Table 1] and [Table 2]. The average onset of sensory block was quicker in group D (120.32 s) compared with group S (178.67 s), and the difference was statistically highly significant [Table 1]. The average time for attaining peak sensory level or the upper sensory level was nearly the same in both groups (16.45 min for group D and 15.67 min for group S) [Table 1]. The average time for two-segment regression is more in group D (75.16 min) than in group S (55.17 min) [Table 1]. However, the average requirement of mephentermine was nearly the same in both groups (12.19 mg for group D and 9.60 mg for group S) [Table 1]. No complications were observed in either group.
Table 1 Analysis of comparable parameters

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Table 2 Analysis of sex

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  Discussion Top


The advantage of epidural anesthesia using a catheter over single-shot spinal anesthesia is the liberty of being able to titrate the dose of local anesthetic to the effect along with the freedom of extending the duration of anesthesia when surgery is getting prolonged. Absence of dural puncture and postoperative analgesia are the other benefits of epidural anesthesia over spinal anesthesia. Early onset is one important aspect where the subarachnoid block has an edge over epidural anesthesia, which usually takes 20-30 min to act. Addition of an adjuvant to the local anesthetic can minimize this delay. An ideal adjuvant should not only hasten the onset of action of the local anesthetic but also facilitate reduction in its dosage along with providing hemodynamic stability and an optimal sedation. The literature reveals several clinical trials studying the role of various pharmacological agents such as opioids [6], benzodiazepines [7], dexamethasone [8], neostigmine [9], magnesium sulfate [10], sodium bicarbonate, and a-2-AR agonists as adjuvants to local anesthetics in the epidural compartment.

The central a-2-AR agonists inhibit nociceptive impulses by activating postjunctional a-2-adrenoceptors in the dorsal horn of the spinal cord. These types of receptors are located on primary afferent terminals (both at peripheral and at spinal endings), on neurons in the superficial lamina of the spinal cord, and within several brainstem nuclei implicated in analgesia. They block the conduction of C- and A-delta fibers and increase potassium conductance, thus intensifying conduction block. They also cause local vasoconstriction, thereby reducing vascular uptake of the local anesthetic from around the neural structures [11]. Dexmedetomidine was found to be effective in hastening and improving the quality of epidural anesthesia when added to a local anesthetic [12-14].

Adding sodium bicarbonate to lidocaine hastens the onset and enhances the depth of epidural blockade. The increase in pH increases the extraneural amount of nonionized local anesthetic, which is the form that diffuses through the lipid phase of the neural membrane [15]. CO 2 produced by the addition of bicarbonate and bicarbonate per se reduces the margin of conduction safety of the neural membrane [16]. Moreover, CO 2 penetrates into the nerve, where it may determine trapping of the active cationic form of local anesthetic by acidifying the axoplasm [16]. Several studies have shown that addition of sodium bicarbonate hastens the onset of action of lidocaine in the epidural space [17,18], which was not observed in a few other studies [19].

Dexmedetomidine and sodium bicarbonate have been proven to be effective in providing the same pharmacological benefit through two different mechanisms of action. To the best of our knowledge, no study was carried out in the past comparing the role of these two agents as adjuvants in epidural anesthesia.

In our study, we observed that the onset of action in the dexmedetomidine group was quicker (average 120.32 s) than in the sodium bicarbonate group (average 178.67 s). However, the time for attaining peak sensory level did not show much difference between the two groups. On the other hand, the time for two-segment regression was more in the dexmedetomidine group than in the sodium bicarbonate group, suggesting a longer duration of action with dexmedetomidine [Figure 1]. The incidence of hypotension was also similar in both groups. In this study, we used 12.5 ml of 2% lidocaine for epidural anesthesia as all surgeries were on the lower limb. Higher volumes are certainly required for abdominal procedures in which the concentration of the local anesthetic needs to be reduced to avoid toxicity, which may jeopardize the quality of sensory and motor blockade. There is plenty of scope for further research in this area wherein the role of adjuvants in minimizing the local anesthetic dose in epidural anesthesia can be investigated.
Figure 1: Dexmedetomidine versus sodium bicarbonate

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  Conclusion Top


We conclude that dexmedetomidine is more effective than sodium bicarbonate in hastening the onset and prolonging the duration of blockade when used as an adjuvant to epidural lidocaine. However, the influence on hemodynamic stability is nearly the same for dexmedetomidine and sodium bicarbonate.

Acknowledgments

The authors thanks to Saritha for statistical support and to Madhavi for office assistance. They also thank all patients who participated in the study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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Kaur S, Attri JP, Kaur G, Singh TP. Comparative evaluation of ropivacaine versus dexmedetomidine and ropivacaine in epidural anesthesia in lower limb orthopedic surgeries. Saudi J Anaesth 2014; 8:463-469.  Back to cited text no. 14
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