|Year : 2015 | Volume
| Issue : 2 | Page : 269-275
Addition of dexmedetomidine to bupivacaine in the lumbar plexus block potentiates postoperative analgesia among hip arthroplasty patients: a prospective randomized controlled trial
Hesham F Soliman MD
Department of Anesthesia, Faculty of Medicine, Ain-Shams University, Cairo, Egypt ; Alnoor Specialist Hospital, Makkah, Kingdom of Saudi Arabia
|Date of Submission||02-Dec-2014|
|Date of Acceptance||22-Mar-2015|
|Date of Web Publication||8-May-2015|
Hesham F Soliman
Alnoor Specialist Hospital, PO Box 6251, Makkah 21955
Source of Support: None, Conflict of Interest: None
Dexmedetomidine is an α2-adrenergic agonist, which prolongs analgesia when administered in neuroaxial and peripheral nerve blocks. The aim of this study was to evaluate the effect of adding dexmedetomidine to bupivacaine in the lumbar plexus block (LPB) as regards analgesic characteristics and opioid consumption.
Materials and methods
Fifty patients scheduled for total hip arthroplasty were divided into two groups: group B patients (N = 25) received LPB with 30 ml of 0.25% bupivacaine and 2 ml of normal saline, while group BD patients (N = 25) received LPB with 30 ml of 0.25% bupivacaine and dexmedetomidine 1 μg/kg diluted in 2 ml of normal saline. Time for first analgesic administration, totally used doses of morphine, pain scores, hemodynamic data, and side effects were recorded.
Demographic and operative characteristics were comparable between the two groups. The time for first analgesic request was longer in group BD than group B [502 vs. 243 min (P < 0.001) and the total morphine consumption in 24 h was less among group BD patients compared with those in group B (19 vs. 32 mg, P < 0.001)]. The visual analogue score was significantly lower in group BD in the first 8 h postoperatively compared with group B (P < 0.001). In group BD a lower heart rate was noticed 120 min postinduction that continued for the first 4 h postoperatively (P < 0.001).
The addition of dexmedetomidine to bupivacaine in LPB prolongs the time for first analgesic requirement and reduces the total postoperative opioid consumption without major side effects.
Keywords: dexmedetomidine, lumbar plexus block, postoperative analgesia, total hip arthroplasty
|How to cite this article:|
Soliman HF. Addition of dexmedetomidine to bupivacaine in the lumbar plexus block potentiates postoperative analgesia among hip arthroplasty patients: a prospective randomized controlled trial. Ain-Shams J Anaesthesiol 2015;8:269-75
|How to cite this URL:|
Soliman HF. Addition of dexmedetomidine to bupivacaine in the lumbar plexus block potentiates postoperative analgesia among hip arthroplasty patients: a prospective randomized controlled trial. Ain-Shams J Anaesthesiol [serial online] 2015 [cited 2019 May 23];8:269-75. Available from: http://www.asja.eg.net/text.asp?2015/8/2/269/156716
| Introduction|| |
Postoperative pain following total hip arthroplasty is severe, especially in the first 24 h, which is aggravated with patient mobilization. The pain-induced stress contributes to a higher incidence of cardiovascular and pulmonary complications, thus, the choice of the anesthetic technique being easy to execute, allowing early patient ambulation, and decreasing perioperative morbidity is crucial , . Effective postoperative pain relief is essential for patient comfort and satisfaction, allows greater mobility, minimizes postoperative morbidity, and promotes faster recovery by preventing or decreasing muscle spasms that hinder early joint mobilization  . Lumbar plexus block (LPB) for hip surgeries reduced both postoperative pain scores and rescue opioid consumption ,,, . Dexmedetomidine is a highly selective α2-adrenergic receptor agonist with a ratio of α2 to α1 of 1620 : 1. α2-Receptor stimulation is responsible for the hypnotic and analgesic effects  . Previous trials demonstrated that addition of perineural dexmedetomidine to bupivacaine enhanced sensory and motor blocks ,,, whereas, the study by Ozalp et al.  found no effect of adding dexmedetomidine to ropivacaine in the interscalene block. Midline search did not reveal any study that describes the addition of dexmedetomidine to bupivicaine for LPB.
This prospective, double blinded, randomized study was conducted to evaluate the analgesic effect of adding dexmedetomidine to bupivacaine on LPB for patients undergoing hip arthroplasty.
| Materials and methods|| |
This study was conducted at Al Noor Specialist Hospital, Makkah, Saudi Arabia from June 2011 to August 2013. After approval from the Research and Ethics Committee, 58 patients were screened for eligibility in the preoperative anesthesia clinic to participate in this prospective randomized double blinded study. Written informed consent was obtained from 50 patients over the age of 18 years, for both sexes, and American Society of Anaesthesiologists' (ASA) physical status I or II patients, scheduled for elective unilateral total hip arthroplasty surgery. Exclusion criteria were patient refusal, patients with a history of cardiac, respiratory, renal, or hepatic failure, coagulation disorders, local infection at the site of block, psychological disorders, allergy to study medications, and chronic use of pain medications or adrenoreceptors agonists or antagonists. In postanesthesia care unit (PACU), the LPB technique as well as the 11 points visual analogue scale (VAS) for pain assessment measured 0 as being equal to no pain and 10 being equal to the worst pain imaginable and the use of intravenous patient controlled analgesia (IV-PCA) for postoperative pain control was explained to all patients. In the preoperative holding bay, intravenous midazolam (Dormicum; Roche, Switzerland) 0.03 mg/kg was administered 15 min before pushing patients to the operating theater. Patients were monitored by measuring the noninvasive blood pressure, ECG, pulse oximetry, transcutaneous temperature, and bispectral (BIS) index (Covidien, Lake Forest, IL, Massachusetts, USA). Supplemental oxygen (4-6 l/min) was applied through a face mask. Patients were positioned to lateral decubitus with the operative side up. Under a complete aseptic technique, the puncture site was prepared.
The spinous process of L4 was identified and a line drawn from the center of the L4 spinous process laterally to intersect with a line that passes through the posterior superior iliac spine parallel to the vertebral column on the operative side. The puncture point is at the junction of the lateral one-third and medial two-third of the line joining L4 to the line passing through the posterior superior iliac spine. After subcutaneous infiltration of the entry point with 2-3 ml of 1% lidocaine (Xylocaine Astra Zeneca, Sweden), LPB was performed using an insulated 120-mm, 21-G (17° cutting) bevel needle (Echoplex; Vygon, Ecouen, France). The nerve stimulator (Stimuplex HNS 12; B/Braun, Melsungen, Germany) was connected with the cathode to the insulated needle and with the anode to a solid-gel skin electrode on the ipsilateral mid-thigh. The nerve stimulator was set at a current of 1.5 mA and a 0.1 ms impulse duration with an initial frequency of 1 Hz. The needle was advanced perpendicular to the skin till the quadriceps femoris muscle twitches would be obtained where the frequency was gradually lowered till a motor response was still visible, but not to less than 0.4 Hz. Patients were assigned at random into two groups by a computer generated code enclosed in opaque envelopes. The pharmacy prepared the study medications according to the list of study numbers and sent it to the operating theater with other medications such as antibiotics belonging to the patients. Group B (N = 25) patients received LPB using 32 ml of the study medication, which consisted of 30 ml of bupivacaine 0.25% (Marcaine; Astra Zeneca) and 2 ml of normal saline while group BD (N = 25) patients received LPB with a 32 ml solution in which dexmedetomidine (Precedex; Hospira Inc., Lake Forest, IL 60045, USA) 1 μg/kg was diluted in normal saline to reach a total volume of 2 ml and added to 30 ml of bupivacaine 0.25%. Twenty minutes after completion of the block, the area of incision was tested for sensory block by pinprick discrimination using hypodermic needle 23 G ¾ inch (BD-Microlance, Spain). General anesthesia was standardized for all patients in both groups. Fentanyl (Fentanyl; Janssen-Cilag Pharma, Belgium) 2 μg/kg and propofol (Fresenius Kabi, Bad Homburg, Germany) 2 mg/kg were intravenously administered and rocuronium (Esmeron; N.V. Organon, Oss, the Netherlands) 0.6 mg/kg intravenously was given to facilitate tracheal intubation. A tracheal tube of size 8.0 mm I.D (Portex Tracheal Tube; Smith Medical International Ltd, Ashford, Kent, UK) was used for males and size of 7.0 mm I.D for females. Lungs were ventilated in a pressure controlled mode to maintain normocapnia. Sevoflurane in an O 2 /air mixture was administered to keep BIS values between 40 and 60. All surgical procedures were performed by the same orthopedic team. Fentanyl 1 μcg/kg intravenously was administered for any intraoperative increase in the heart rate (HR) or mean arterial blood pressure (MAP) above 20% of baseline. HR and MAP were recorded at preblock, 5 min postblock, preinduction, 5, 10, 20, 30, 60, 90, and 120 min postinduction. End-tidal (ET) sevoflurane concentration and BIS values in both groups were recorded immediately postinduction, 5, 10, 20, 30, 60, 90, and 120 min Also, the number of intraoperative rescue fentanyl boluses was documented. After completion of the surgical procedure and reversal of the neuromuscular blockade effect, patients' tracheas were extubated. Patients were transferred to the PACU and IV-PCA was commenced with morphine (1 mg bolus, lock out time interval of 10 min, and 4-h limit of 0.25 mg/kg without baseline infusion) and continued for 24 h postoperatively.
The time of first analgesia request was recorded from the completion of LPB to the first demand for the morphine dose. Number of used PCA boluses of morphine at 0-4, 4-8, 8-12, 12-18, 18-24 h postoperatively and total morphine dose consumption in 24 h postoperatively were recorded.
Nausea and vomiting were recorded using a categorical scoring system (0 = none, 1 = nausea, 2 = retching, 3 = vomiting). Intravenous metochlopromide 10 mg bolus was offered for any patient with a score of at least 1. Inverted observer assessment of the alertness/sedation score (1 - awake, 2 - arousable to verbal command, 3 - arousable with gentle tactile stimulation, 4 - arousable with vigorous shaking, and 5 - asleep and unarousable) was used to assess the sedation level in the postoperative period.
MAP, HR, VAS, nausea and vomiting, observer assessment of the alertness/sedation score, were recorded on admission to PACU (0 h), 1, 4, 8, 12, 18, and 24 h postoperatively by an observer who was unaware of the study protocol as well as the number of IV-PCA boluses and total morphine consumption.
| Statistical methods|| |
The required sample size was calculated using the G*Power software version 3.1.7 (Universität Düsseldorf, Germany). The primary outcome measures were the differences between the two groups as regards the pain scores and analgesic consumption. The secondary outcome measures were the hemodynamic parameters and anesthetic requirement. It was estimated that a sample of 25 patients in either study group would achieve a power of 80% to detect a statistically significant difference between the two groups for a large effect size of d = 0.8. This calculation used the unpaired t-test and assumed a two-sided type I error of 0.05. An effect size of d = 0.8 was chosen as it could be regarded as a clinically relevant difference to seek in this exploratory study.
Data were analyzed using IBM© SPSS© Statistics version 22 (IBM© Corp., Armonk, New York, USA) and MedCalc© version 13 (MedCalc Software bvba, Ostend, Belgium). The D'Agostino-Pearson test was used to examine the normality of numerical data distribution. Normally distributed numerical variables were presented as mean and SD, and intergroup differences were compared using the independent-samples unpaired t-test. Discrete data and skewed continuous data were presented as the median and interquartile range, and differences were compared using the Mann-Whitney test. Categorical data were presented as a number and percentage and differences were compared using the Pearson χ2 -test.
Repeated-measures analysis of variance was used to analyze serial measurements. Repeated measures were compared with baseline values using the Bonferroni test.
Mixed linear modeling was used to examine the effect of time, randomization group, and time-group interaction on the changes in intraoperative variables.
A two-sided P-value less than 0.05 was considered statistically significant.
| Results|| |
The flow of patients throughout the trial is shown in [Figure 1]. Demographic and operative data in the two groups were comparable ([Table 1]). None of the patients in both groups required intraoperative rescue fentanyl boluses. Time for first analgesic request was longer in group BD than group B (502 vs. 243 min; P < 0.001) ([Figure 2]). Total consumed morphine in the first 24 h was less among group BD patients compared with those in group B (19 vs. 32 mg; P < 0.001) ([Figure 3]). The number of IV-PCA boluses was significantly higher in group B compared with group BD (P < 0.001) ([Table 2]). As regards the VAS, it was significantly lower in group BD than group B in the first 8 h postoperatively (P < 0.001) ([Table 2]). Regarding hemodynamic changes, there was significant decrease in HR starting 120 min postinduction to 4 h postoperatively within group BD compared with group B (P < 0.001) ([Figure 4]), whereas no changes in perioperative MAP, intraoperative ET sevoflurane concentrations, and BIS values were noticed between study groups. Two patients in group B and one patient in group BD complained of nausea meanwhile patients in group BD experienced significantly higher sedation scores up to 4 h postoperatively (P < 0.001) ([Table 3]). Using the mixed linear modeling statistical method, there was a statistically significant difference between the two groups as regards the trend of change in the HR (P < 0.001) and the MAP (P < 0.001). The effect of time on the HR and the MAP was statistically significant (P < 0.001). Besides, there was statistically significant interaction between the randomization group and time as regards both variables (P < 0.001) ([Table 4]).
|Figure 1: The CONSORT flow chart showing flow of patients through the trial.|
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|Figure 2: The box plot showing the time for fi rst analgesic request in both study groups. The box represents the interquartile range. The horizontal line across the box represents the median. Error bars represent the|
minimum and maximum values excluding outliers (rounded markers) and extreme observations (asterisks).
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|Figure 3: The box plot showing the cumulative morphine consumption in both study groups. The box represents the interquartile range. The horizontal line across the box represents the median. Error bars|
represent the minimum and maximum values excluding outliers (rounded markers) and extreme observations (asterisks).
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|Figure 4: Changes in heart rate in both study groups. Error bars represent 95% confidence interval.|
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|Table 3 Sedation and postoperative nausea and vomiting scores in both groups|
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|Table 4 Mixed linear modeling for the changes in hemodynamic variables, anesthetic requirements, and anesthetic depth|
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On the other hand, there was no statistically significant difference between the two groups as regards the trend of ET sevoflurane concentration (P = 0.190) or the BIS index (P = 0.636). The effect of time on the BIS index was statistically significant (P < 0.001). No such effect was observed for the ET sevoflurane concentration (P = 0.909). There was no statistically significant interaction between the randomization group and time as regards the ET sevoflurane concentration (P = 0.998) or the BIS index (P = 0.947) ([Table 4]).
| Discussion|| |
This prospective randomized trial shows that the addition of dexmedetomidine to bupivacaine in LPB provides better postoperative pain control as the duration of local anesthetic effect was longer, VAS was lower, and the need for rescue morphine administration was less compared with that block done using bupivacaine alone.
LPB with or without perineural catheter placement, is one of the preferred anesthetic options for lower limb surgery either as a sole anesthetic technique or combined with general anesthesia.
Compared with the neuroaxial block, LPB maintains intraoperative hemodynamic stability and decreases the risk of both dural puncture and urinary retention ,,,, .
Dexmedetomidine is a short acting highly selective α2-agonist which preserves the respiratory function even in high doses  . Although its elimination half-life is short (2-3 h), the analgesic-sparing effect observed after preoperative or intraoperative dexmedetomidine administration lasts up to 24 h which was attributed to its anxiolytic, sedative, and thymoleptic properties  . Dexmedetomidine has been used successfully to improve the quality and intensity of the regional anesthesia block  . The mechanism by which dexmedetomidine improves the peripheral nerve block characteristics of local anesthetics is still not clear  . Peripherally, dexmedetomidine produces analgesia by reducing norepinephrine release and increasing the potassium conduction in C and A-delta neurons responsible for passage of pain stimulus, whereas dexmedetomidine produces analgesia and sedation centrally by inhibition of substance P release in the nociceptive pathway at the level of the dorsal root ganglia and locus ceruleus  .
In the last four decades, different approaches for the LPB have been proposed. In 1989, Parkinson et al.  described the L3 approach (Dekrey's approach) for the LPB, whereas Hanna et al.  described an L2-L3 interspace approach for the psoas compartment block (PCB) in 1993. The Capdevila approach was used in the present study, which is a modified Winnie (L4) approach using a more medial needle insertion point.
Different studies revealed an LPB-induced reduction of both pain scores and consumption of rescue opioids after hip surgeries [3, 5, 6, 24]. The study of Stevens et al.  showed significant lower pain scores and total opioid consumption up to 6 h after total hip arthroplasty in patients receiving a single-injection LPB combined with general anesthesia compared with patients who received general anesthesia only. Touray et al.  described 8 h of postoperative lower pain scores and morphine consumption following single injection LPB for hip arthroplasty, which comes in accordance with the results of the present study where analgesia extended up to 8 h postoperatively in group BD. This analgesic benefit might be extended beyond 8 h by the use of a continuous infusion. Becchi et al.  described the clinical efficacy of a continuous PCB after a total hip arthroplasty where lower pain scores at rest and mobilization together with lower rescue analgesic demands were achieved during the whole study duration (48 h). Also, reduction of rescue opioids by the use of a continuous LPB for hip surgeries has been described by Chelly and Siddiqui et al. , . Furthermore, Chudinov et al.  described a significant reduction of postoperative pain scores up to 32 h using a continuous PCB in patients undergoing hip fracture repair. However, the reduction of the cumulative dose of morphine was extended up to 24 h postoperatively especially in the BD group. Turker et al.  found no significant differences in analgesic properties between a PCB and epidural analgesia for patients undergoing partial hip replacement surgery. This implies a certain preference for an LPB as a postoperative analgesic strategy for hip surgery as undesired side effects of epidural analgesia, like urinary retention, hypotension, and pruritus, can be avoided meanwhile prolonged postoperative analgesia can be offered , .
As a sole anesthetic technique for hip surgery, the LPB is likely to be insufficient. De Visme et al.  described a substantial need for supplemental opioids and sedatives for 27% of the patients undergoing hip fracture repair under PCB with an additional sacral plexus block. Buckenmaier et al.  concluded that an LPB with a perineural catheter and sciatic nerve block combined with intraoperative sedation is an effective alternative to general anesthesia for total hip arthroplasty. A possible explanation of the insufficiency of the PCB as a sole anesthetic technique for hip surgery could be the variable innervations of the surgical site extending from T12 to L1 dermatomes  .
Dexmedetomidine might be associated with some side effects such as hypotension, bradycardia, and sedation particularly at higher doses  . The current study reported a significant fall in the HR 120 min postinduction in the BD group compared with the B group. This effect persisted for 4 h without any hemodynamic instability. The decrease in HR might be related to the postsynaptic activation of central a2-adrenoceptors, leading to decreased sympathetic activity and a slower HR , . Similar to the HR, increased sedation was noticed in the first postoperative 4 h among group BD patients. None of our patients required treatment for the low HR or sedation.
A limitation of this study is the inability to measure dexmedetomidine plasma concentration among group BD patients to determine whether its action was related to partial systemic absorption or to a purely local effect which could be solved by adding a third group of patients who would receive both LPB with bupivacaine and intravenous dexmedetomidine but this design was aborted due to limited availability of dexmedetomidine in our hospital.
| Conclusion|| |
The addition of dexmedetomidine to bupivacaine in LPB helps achieve prolonged postoperative analgesia and reduces the total consumed opioid dose in patients undergoing unilateral hip arthroplasty without any major side effects.
| Acknowledgements|| |
Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]