Table of Contents  
ORIGINAL ARTICLE
Year : 2014  |  Volume : 7  |  Issue : 2  |  Page : 193-197

Effects of epidural dexmedetomidine and low-volume bupivacaine on postoperative analgesia after total knee replacement


1 Department of Anaesthesia and Surgical Intensive Care, Faculty of Medicine, Menoufiya University, Shebeen Elkoom, Egypt
2 Department of Orthopaedic Surgery, Faculty of Medicine, Menoufiya University, Shebeen Elkoom, Egypt

Date of Submission26-Oct-2013
Date of Acceptance01-Jan-2014
Date of Web Publication31-May-2014

Correspondence Address:
Ashraf M. Eskandar
Department of Anaesthesia and Surgical Intensive Care, Faculty of Medicine, Menoufiya University, Shebeen Elkoom
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1687-7934.133440

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  Abstract 

Background
Postoperative pain after total knee arthroplasty is a major interest. Epidural analgesia is considered the preferable method of postoperative analgesia for total knee arthroplasty in many countries. Dexmedetomidine is an α-2 agonist, which has many beneficial effects when administered epidurally.
Purpose
The aim of the study was to provide effective postoperative analgesia with hemodynamic stability through reduction in the amount of local anesthetic administered epidurally using dexmedetomidine as an adjuvant to epidural bupivacaine.
Patients and methods
A total of 50 patients who were 40-60 years of age, had ASA physical status I-III, and who were undergoing elective total knee arthroplasty were randomly divided into two equal groups: group D received 2.5 ml of a mixture of bupivacaine 0.125% and dexmedetomidine 0.2 μg/kg/h and group B received only 0.125% bupivacaine 5 ml/h for postoperative analgesia. Postoperative pain was scored by visual analogue scale; sedation score and cardiorespiratory parameters were recorded every 6 h for 48 h postoperatively. Data were recorded and statistically analyzed.
Results
The demographic data were comparable in both groups. Visual analogue scale of pain showed a significant reduction between the two groups at both rest and movement, and the total dose of nalbuphine consumption during the study period was significantly reduced (P < 0.002) in group D (5 ± 5.15) than in group B (11 ± 7.63). Sedation scores were significantly higher in group D compared with group B. Heart rate was significantly reduced in group D from 18 h postoperative until the end of the study, and the mean arterial blood pressure was significantly reduced in group B than in group D throughout the study period.
Conclusion
Dexmedetomidine is an ideal adjuvant to epidural bupivacaine for postoperative analgesia in patients undergoing total knee arthroplasty.

Keywords: Bupivacaine, dexmedetomidine, epidural analgesia, knee arthroplasty


How to cite this article:
Eskandar AM, Ebeid AM. Effects of epidural dexmedetomidine and low-volume bupivacaine on postoperative analgesia after total knee replacement. Ain-Shams J Anaesthesiol 2014;7:193-7

How to cite this URL:
Eskandar AM, Ebeid AM. Effects of epidural dexmedetomidine and low-volume bupivacaine on postoperative analgesia after total knee replacement. Ain-Shams J Anaesthesiol [serial online] 2014 [cited 2017 Oct 22];7:193-7. Available from: http://www.asja.eg.net/text.asp?2014/7/2/193/133440


  Introduction Top


Epidural anesthesia is the most commonly used technique for inducing surgical anesthesia and postoperative analgesia in lower abdominal and limb surgeries [1]. Early postoperative mobilization and rehabilitation with minimally associated pain and discomfort is the most desirable quality that has been needed in modern orthopedic surgery [2],[3],[4]. For achieving this effect, large volumes of local anesthetics were used, increasing the possibilities of local anesthetic toxicity and hemodynamic instability [5]. Many adjuvants to epidural injection have been used to decrease such complications. Sedation, stable hemodynamics, and an ability to provide smooth and prolonged postoperative analgesia are the main desirable qualities of an adjuvant in neuroaxial anesthesia [6].

Dexmedetomidine is an opioid-sparing adjuvant to epidural administration. Dexmedetomidine is a potent and highly selective α-2-adrenoceptor agonist [7]. It has a relatively high ratio of α2/α1 activity (1620 : 1). The improved specificity of dexmedetomidine for the α-2 receptor causes it to be a much more effective sedative and analgesic agent, with much less unwanted cardiovascular effects from α-1 receptor activation [8].

The aim of the study was to evaluate the effects of epidural adjuvant dexmedetomidine when added to low-volume bupivacaine on postoperative analgesia after total knee arthroplasty.


  Patients and methods Top


After approval from the institutional ethics committee and obtaining written informed consent, 50 patients who were 40-60 years of age of both sexes, had ASA physical status I-III, were admitted to Menoufiya University Hospitals from March 2011 to March 2013, and who were undergoing elective total knee arthroplasty were included in this prospective, single-blind, randomized controlled study. All patients were assessed in the preoperative visit and underwent complete blood count, ECG, coagulation profile, liver function tests, and renal function tests. Written informed consent forms were obtained from all patients after explaining the study protocol to them. Visual analogue score (VAS) graduated from 0 (no pain) to 10 (worst pain) and the epidural analgesia were also explained to the patients. Exclusion criteria included morbid obese, age more than 60 years, known allergy to bupivacaine or dexmedetomidine, renal or hepatic insufficiency, neurological or psychiatric diseases, and coagulation disorders. Patients were randomly classified into two parallel groups (25 patients in each group) using closed envelope technique: group D (the dexmedetomidine group) and group B (the bupivacaine group). All patients received 0.07 mg/kg intramuscular midazolam half an hour before surgery. A good peripheral intravenous line was accessed by 18-G intravenous cannula in the preoperative room; standard monitors were applied preoperatively including ECG, NIBP, and pulse oximetry; and the baseline measurements were recorded. A combined spinal and epidural technique was used for anesthesia and postoperative analgesia. After local infiltration with 2% lidocaine, the epidural space was identified at the L3-L4 intervertebral level with an 18-G Tuohy needle using the loss of resistance to saline technique. A 20-G epidural catheter was positioned 3 cm into the epidural space and secured in place for postoperative analgesia. No test dose was injected. Subsequently, a 25-G spinal needle was advanced at L4-L5 intervertebral level through an introducer until cerebrospinal fluid was obtained, then 15 mg 0.5% heavy bupivacaine was injected and the spinal needle was withdrawn and the patient was laid in the supine position. At the end of surgery, patients were randomly allocated into one of the two groups: group D (the dexmedetomidine group) received epidural injection at 2.5 ml/h of a mixture of 0.125% bupivacaine and 0.2 μg/kg dexmedetomidine, whereas group B (the bupivacaine group) received only epidural injection of 0.125% bupivacaine 5 ml/h. Postoperative pain was assessed using a 10-point VAS (0 = no pain and 10 = worst pain imaginable). According to the patient's request to analgesia when VAS was greater than 4, postoperative incremental doses of intravenous 2 mg nalbuphine were given and recorded. The patient's level of sedation was assessed using the inverted observer's assessment of alertness/sedation scale [9], with a score of 1 = completely awake, 2 = awake but drowsy, 3 = asleep but responsive to verbal commands, 4 = asleep but responsive to tactile stimulus, and 5 = asleep and not responsive to any stimuli. The postoperative data (e.g. pain, sedation) and cardiorespiratory parameters (heart rate, mean arterial blood pressure, and oxygen saturation) were monitored and recorded every 6 h for 2 days. Hypotension (defined as systolic arterial pressure decreasing more than 20% mmHg) was treated by injecting ephedrine 3-4 mg in bolus doses, and heart rate less than 50 beats/min was treated with 0.3 mg of atropine.

Statistical analysis

A power analysis was performed using a power of 90% and an α-value of 0.05. We assumed that the VAS score during movement would be 40% in group D and 60% in group B, with an SD of 20. The sample size was calculated to be 23 patients; hence, we decided to include 25 patients in each group in the study. We used GraphPad Stat Mate version 2 statistics program for power analysis.

Statistical analysis was performed using SPSS program. Descriptive statistics were expressed as mean + SD unless otherwise stated. Student's t-test was used for comparison of the means of continuous variables and normally distributed data. The Mann-Whitney U-test was used otherwise. P-value less than 0.05 was considered statistically significant.


  Results Top


The demographic data of the patients in the two groups were comparable with respect to age, sex, weight, and height [Table 1]. VAS of pain showed a significant reduction between the two groups at both rest and movement [Table 2] throughout the study period. [Table 3] shows that the total dose of nalbuphine consumption during the study period was significantly reduced (P < 0.002) in group D (5 ± 50.45) than in group B (11 ± 7.63). Dexmedetomidine is a potent sedative agent, which can be observed in the present study findings, as the sedation score was significantly higher in group D compared with group B [Table 4]. Heart rate was significantly reduced in group D from 18 h postoperative until the end of the study [Table 5]. In contrast to heart rate, the mean arterial blood pressure was significantly reduced in group B than in group D throughout the study period [Table 5]. There was insignificant difference between the two groups with respect to SpO 2 .
Table 1: Demographic data

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Table 2: Visual analogue scale at rest and on flexion of the operated knee

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Table 3: Nalbuphine consumption (mg)

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Table 4: Sedation score

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Table 5: Heart rate (beats/min) and mean arterial pressure (mmHg)

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  Discussion Top


The present study has found that adding dexmedetomidine as an adjuvant to postoperative epidural bupivacaine 0.125% in patients undergoing total knee replacement significantly reduced postoperative pain during both rest and movement, with significant reduction in postoperative nalbuphine consumption and local anesthetic volume with cardiorespiratory stability.

Total knee arthroplasty is associated with intense early postoperative pain. Improving the pain management techniques and rehabilitation programs have significant impact on postoperative outcome [10]. The early ambulation and participation in the physical therapy to restore the range of movement of the knee after total knee replacement are facilitated by excellent early analgesia [11]. Early ambulation and rehabilitation are essential for normal function of the fibroblasts and chondrocytes, which enhance normal healing [12]. Prolonged immobilization can lead to muscle atrophy, cartilage ulceration, and development of connective tissue adhesions [12]. We concluded that the early rehabilitation, which is facilitated with continuous epidural infusion postoperatively in the present study, can help to prevent complications from immobilization and to promote early recovery of the joint function postoperatively. Postoperative pain relief can be achieved by a number of techniques, such as intravenous patient-controlled analgesia [13], epidural analgesia with narcotics and/or local anesthetics [14],[15], lumbar plexus blockade [16], and continuous three-in-one block [17],[18]. The use of epidural analgesia is the preferred technique of analgesia in many European countries for total knee arthroplasty, as revealed by a recent declarative European survey [19]. Epidural analgesia with opioid and/or local anesthetics provides superior pain relief compared with other previous techniques [20],[21],[22],[23]. However, it is associated with side effects, such as nausea, pruritus, urinary retention, and respiratory depression with opiates, and bilateral motor blockade and arterial hypotension with local anesthetics [18],[19],[20],[21],[22],[23]. Hence, in the present study we have tried to reduce these complications and provide suitable postoperative analgesia for patients undergoing total knee arthroplasty by adding dexmedetomidine to low-volume bupivacaine through epidural route. Epidural dexmedetomidine is an α-2 agonist, which has numerous beneficial effects [24]. It acts on both presynaptic and postsynaptic sympathetic nerve terminal and central nervous system, thereby decreasing the sympathetic outflow and norepinephrine release causing sedative, antianxiety, analgesic, sympatholytic, and hemodynamic effects [24],[25]. Epidural dexmedetomidine reduced postoperative VAS at rest and movement as found by Elhakim et al. [8], and it also decreased postoperative analgesic requirement. Dexmedetomidine has a potent sedative effect, which is approved by the present study that showed a significant increase in sedation score in the dexmedetomidine group. The sedative and analgesic effects of dexmedetomidine have been documented in several studies [26],[27],[28], after major surgical surgeries [29], after thoracic surgery [8], after vaginal hysterectomy [24], and after lower limb orthopedic surgery [25]. Dexmedetomidine exerts its sedative and analgesic-sparing effects through central actions in the locus coeruleus and in the dorsal horn of the spinal cord, respectively [30],[31]. Significant decrease in heart rate from the baseline was reported in-between the studied groups when dexmedetomidine was administered, as found by many previous studies [24],[25],[26]. The decrease in heart rate caused by α-2 agonist can be explained by its central action decreasing the sympathetic outflow and norepinephrine release. In contrast to heart rate results, the mean arterial pressure was decreased in both groups from the baseline, with a significant decrease in the bupivacaine group than in the dexmedetomidine group, which can be explained by using lower volume (2.5 ml/h) of local anesthetic in group D than (5 ml/h) in group B. Although the decrease in heart rate and mean arterial blood pressure was reported in the dexmedetomidine group, it never was less than 20% of the baseline values, which proved that the use α-2 agonists provides a hemodynamic stability during the postoperative periods.


  Conclusion Top


Dexmedetomidine is an ideal adjuvant to epidural bupivacaine for postoperative analgesia in patients undergoing total knee arthroplasty because of its stable cardiorespiratory parameters, postoperative analgesia, reduction in epidural local anesthetic volume, and postoperative analgesic requirements.


  Acknowledgements Top


Conflicts of interest

None declared.

 
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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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