|Year : 2015 | Volume
| Issue : 2 | Page : 206-210
Effects of adding low-dose clonidine to a small intrathecal dose of either bupivacaine or ropivacaine on the characteristics of spinal block in elderly patients undergoing primary hip arthroplasty
Amira F Hefni MD
Department of Anesthesia and Intensive Care Medicine, Ain Shams University Hospitals, Cairo, Egypt
|Date of Submission||01-Oct-2014|
|Date of Acceptance||21-Jan-2015|
|Date of Web Publication||8-May-2015|
Amira F Hefni
Department of Anesthesia and Intensive Care Medicine, Ain Shams University Hospitals, Cairo
Source of Support: None, Conflict of Interest: None
The use of an adjuvant with small doses of local anesthetics is a preferred technique for spinal anesthesia in elderly patients. In our study, we compared the characteristics of spinal block after adding 15 µg clonidine to either 8 mg bupivacaine or 12 mg ropivacaine with regard to the anesthetic efficacy and the incidence of side effects in geriatric patients undergoing lower limb orthopedic surgery.
Patients and methods
In a prospective, double-blind randomized study, 60 patients of at least 60 years old undergoing primary hip arthroplasty under spinal anesthesia were randomly allocated into one of the two groups. Group BC received 8 mg bupivacaine with 15 µg of clonidine and Group RC received 12 mg of ropivacaine with 15 µg of clonidine. Onset times to reach the peak sensory and motor levels and the duration of sensory and motor blocks were recorded. Hemodynamic changes and side effects including the level of sedation were also recorded.
The highest levels of sensory blocks were similar (T5) in both groups, but the onset time of sensory block was significantly shorter in Group BC (2.54 ± 0.66 min) than in Group RC (3.19 ± 0.70) (P < 0.01).The onset time of motor block (4.80 ± 1.46 min in the BC Group and 4.95 ± 1.04 min in the RC Group), the time to the maximum motor block (11 ± 2.1 min in the BC Group and 11.5 ± 3.2 min in the RC Group),the mean durations of both the sensory block (149 ± 20 min in the BC Group and 148 ± 15 min in the RC Group) and the motor block (165 ± 25 min in the BC Group 164 and ± 20 min in the RC Group) were all comparable between both groups. Differences in the hemodynamic parameters between both groups were insignificant.
Adding low-dose clonidine (15 µg) to an intrathecal small dose of either bupivacaine (8 mg) or ropivacaine (12 mg) made the difference between both local anesthetics with regard to the motor block and hemodynamic changes insignificant, but did not change the significant difference between them in the onset of sensory block. Either the bupivacaine-clonidine or the ropivacaine-clonidine combination provides sufficient motor and sensory block in elderly patients undergoing major orthopedic surgery without inducing hemodynamic instability.
Keywords: bupivacaine, clonidine, ropivacaine, spinal
|How to cite this article:|
Hefni AF. Effects of adding low-dose clonidine to a small intrathecal dose of either bupivacaine or ropivacaine on the characteristics of spinal block in elderly patients undergoing primary hip arthroplasty. Ain-Shams J Anaesthesiol 2015;8:206-10
|How to cite this URL:|
Hefni AF. Effects of adding low-dose clonidine to a small intrathecal dose of either bupivacaine or ropivacaine on the characteristics of spinal block in elderly patients undergoing primary hip arthroplasty. Ain-Shams J Anaesthesiol [serial online] 2015 [cited 2021 Apr 17];8:206-10. Available from: http://www.asja.eg.net/text.asp?2015/8/2/206/156687
| Introduction|| |
A variety of anatomical and physiological changes related to aging contribute to altered nerve block characteristics after subarachnoid administration of local anesthetics in elderly patients  . With hyperbaric local anesthetic solutions, the maximal height of spinal analgesia achieved has been found to increase with age , . Also, aging changes in the cardiovascular system may lead to more frequent incidence of systemic hypotension and bradycardia associated with spinal anesthesia compared with younger individuals  . Lower doses of local anesthetics along with an adjuvant are preferred for spinal anesthesia in elderly patients  . Of the safe additives, clonidine, dexamethasone, dexmedetomidine, and fentanyl have been tried, with intrathecal comparable doses of local anesthetics , . In previous studies, clonidine was mostly added to hyperbaric bupivacaine  . In our study, we added low-dose clonidine (15 µg) to 12 mg of hyperbaric solution of ropivacaine administrated intrathecally to compare its anesthetic efficacy and side effects with an equivalent dose of heavy bupivacaine (8 mg) added to the same dose of clonidine (15 µg) in elderly patients undergoing major hip surgery.
| Patients and methods|| |
After approval by the institutional Ethics Committee, a written informed consent was obtained from 64 patients with American Society of Anesthesiologists (ASA) score II-III, aged 60 years and above and from both sexes, scheduled for primary hip arthroplasty in Saudi German hospital in Riyadh, Saudi Arabia, between February 2012 and February 2014. Patients who suffered from uncontrolled hypertension, uncontrolled diabetes mellitus, and recent myocardial infarction or those who had hypersensitivity to bupivacaine, ropivacaine, or any contraindication to spinal anesthesia were excluded from the study. Patients were randomized in a double-blinded manner using a computer-generated sequence of numbers and the closed envelope method, and the master codes were kept with a person who did not share in the collection or the analysis of the results. Patients were enrolled into two equal groups: in Group BC, patients (n = 32) received 8 mg of 0.5% hyperbaric bupivacaine and 15 µg clonidine in 2 ml volume, whereas in Group RC, patients (n = 32) received 12 mg of 1% plain ropivacaine added to 1.4 ml of 10% dextrose with 15 µg clonidine in an equal volume (2 ml).
Patients were given an antiemetic, ondansetron 4 mg intravenously, and H2 blockers, ranitidine 50 mg intravenous infusion, 30 min before sending them to the operating room. No sedatives were given in the preoperative period. When patients arrived in the operating room, standard monitoring (pulse oximeter, noninvasive blood pressure, and ECG) was applied. A 20-G intravenous cannula was inserted into the forearm and an infusion of lactated Ringer's solution 7 ml/kg was given intravenously. Anesthetic solutions were prepared by an anesthesiologist who was not involved in subsequent patient care or assessment. The patient was positioned in the lateral decubitus position with the side to be operated upon facing downward. After the skin was disinfected, spinal anesthesia was administered at the L3-4 or the L4-5 interspace using a 25-G spinal needle. After needle insertion and aspiration of the cerebrospinal fluid, Group BC patients (n = 32) received 8 mg of 0.5% hyperbaric bupivacaine and 15 µg clonidine in 2 ml volume, whereas Group RC patients (n = 32) received 12 mg of 1% plain ropivacaine and 15 µg clonidine and 1.4 ml 10% dextrose in an equal volume (2 ml). The drugs were injected into the subarachnoid space at a rate of 0.2 ml/s. Patients were kept in this position for 15 min; after that, the patient was turned, with the operated side now uppermost. The sensory block was evaluated using loss of pinprick sensation every 5 min before surgery was commenced, and then every 30 min during surgery. The motor block was evaluated using a modified Bromage scale (no paralysis, able to flex hip/knee/ankle = 0; able to flex knee, but unable to raise extended leg = 1; able to flex ankle, but unable to flex knee = 2; unable to flex ankle, knee, or hip = 3  ). The operation was allowed to start after the level of sensory block had reached the T10 dermatome and a Bromage score at least 2. The systolic and diastolic arterial pressure (SAP, DAP) and the heart rate (HR) were recorded every 5 min for the first 30 min and then at the 45th, the 60th, and the 120th min. Hypotension was defined as a decrease in the systolic blood pressure of more than 30% of the basic value recorded before spinal block. This was treated with 5-10 mg of ephedrine intravenously and further infusion of lactated Ringer's solution as required. Bradycardia was defined as HR less than 50 beats/min. This was treated with 0.02 mg/kg intravenous atropine as required. The time from local anesthetic injection to the onset of sensory and motor block was recorded. The highest level of sensory block, the onset time of sensory block to T10, the time to maximal cephalic spread, and the time to maximal motor block and Bromage scores were also recorded. All patients received 3 l/min oxygen by nasal cannula during surgery. Respiratory rate less than 8 min -1 and SPO 2 less than 90% were considered as respiratory depression. The level of sedation was evaluated intra-operatively and postoperatively every 15 min using the following scores: 0, alert; 1, occasionally drowsy, easy to arouse; 2, frequently drowsy, easy to arouse; 3, somnolent, difficult to arouse. The occurrence of side effects, including nausea/vomiting and headache, was recorded, and these were managed by the attending anesthesiologist as clinically indicated.
Numbers of participants in this study were calculated considering a minimum augmentation of sensory block by two segments. A minimum of 18 patients were required in each group to produce a significant difference assuming a type-1 error of 0.05 and a power of 0.8. Results are expressed as means and SDs, medians and ranges, or numbers and percentages. The Kolmogorov-Smirnov test was used for determining the normality and the homogeneity of data distribution. Demographic data, the onset time of sensory and motor block, and hemodynamics (SAP, DAP, HR) were compared between the two groups using Student's t-test. The sex, the ASA score, and side effects were compared using the χ2 -test. HR and blood pressures over time within the groups were compared by repeated-measures ANOVA with post-hoc testing. A P value of less than 0.05 was considered statistically significant. A power analysis was performed on the difference of the blood pressures (20%) between the two groups. Statistical analysis was performed using SPSS (version 12.0; SPSS Inc., Chicago, Illinois, USA) software, and graphs were produced using Microsoft Excel for MAC 2011 (version 14.1.2, Microsoft company, New York, USA).
| Results|| |
Sixty-four patients were enrolled in the study. Two patients in each group were excluded from further analysis (one patient was excluded because of protocol violation, and in the other patient, spinal anesthesia was difficult to be performed because of marked ligament ossification) and two patients were postponed. Hence, only 60 patients completed the study: 30 in each group.
There were no statistically significant differences between the two groups with respect to their age, weight, height, sex, ASA score, and duration of surgery ([Table 1]).
The onset time of sensory block in group BC was shorter than that in group R (P < 0.01). The duration of T10 anesthesia and the duration of motor block were comparable between both groups (BC and RC) (P > 0.01 and P > 0.05, respectively) ([Table 2]).
Regarding the onset time of motor block, the onset time of sensory block to T10, the highest level of sensory block, the time to maximum cephalid spread, and the time to maximum motor block, there were no statistical differences ([Table 2]). The number of patients who had motor Bromage scale 3 in group BC (n = 26) were comparable to those in group RC (n = 25, P > 0.05). However, spinal anesthesia was adequate for the surgical procedures in all patients.
On intragroup comparison, significant decreases in the mean SAP and the mean DAP values in comparison with preoperative levels were observed at the 15th, the 30th, the 45th, the 60th, and the 120th min in both group BC and group RC (P < 0.05).
No significant difference in the trends of the mean diastolic and the mean systolic blood pressure on an intergroup comparison was observed ([Figure 1]and [Figure 2]).
|Figure 1: Comparison of systolic arterial pressure (SAP) between the two groups. Data are expressed as me an ± SD.|
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|Figure 2: Comparison of diastolic arterial pressure (DAP) between the two groups. Data are expressed as me an ± SD.|
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On intragroup analysis, significant reductions in HR were determined in both group BC and group RC at the 30th, the 60th, and the 120th min in comparison with preoperative values (P < 0.05). No significant differences in the reductions in HR were determined between both groups. Bradycardia was observed in four patients in group BC and in two patients in group RC, although no significant difference was determined between the two groups regarding the frequency of bradycardia ([Figure 3]).
|Figure 3: Comparison of heart rate (HR) between the two groups. Data are expressed as m ean ± SD.|
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The respiratory rate decreased to below 8 in two patients in group BC and in one patient in group RC, with the SpO 2 decreasing below 90% in only one of these patients. These patients responded to verbal stimuli and the respiratory rate was increased up to 9 in all patients ([Table 3]).
| Discussion|| |
After spinal anesthesia, the levels of both sensory blockade and sympathetic nervous system blockade as assessed by the percentage decrease in the blood pressure and the HR from baseline values were higher in the elderly patient group than in young adults  . Age-related degeneration in the central and the peripheral nervous systems, changes taking place in the lumbar and the thoracic spinal cord, and a reduction of cerebrospinal fluid may be listed among the reasons for this  . Hypotension and bradycardia are the most frequently seen complications of neuroaxial blocks, especially in older patients  . A reduction in the dose of the local anesthetic may decrease the degree of motor block and the sensory level. Addition of different adjunct drugs to the low dose of local anesthetic may be a successful way to establish sufficient motor and sensory block while maintaining hemodynamic stability. In our study, adding low-dose clonidine 15 µg to a low dose of either hyperbaric bupivacaine (8 mg) or an equivalent dose of ropivacaine (12 mg) in a hyperbaric solution to achieve unilateral spinal block in elderly patients scheduled for hip arthroplasty achieved sufficient motor and sensory block for surgery without inducing hemodynamic instability. This agrees with Agarwal et al.  , who found that clonidine 15 µg used as an adjunct to hyperbaric bupivacaine (9 mg) for spinal anesthesia in elderly patients undergoing lower limb orthopedic surgery potentiates the sensory block and the duration of analgesia without affecting the trend of systolic blood pressure as compared with bupivacaine alone; however, clonidine in doses of 30 µg facilitated the ascent of the sensory level block to unexpectedly higher dermatomes for a longer time. Also, Kanazi et al.  added low-dose clonidine (15 µg) even to higher doses of hyperbaric bupivacaine (12 mg), showing prolongation in the duration of the motor and sensory block with preserved hemodynamic stability and lack of excess sedation in patients older than 60 years age undergoing transurethral resection of prostate or bladder tumor. Intrathecal ropivacaine was used with low-dose fentanyl in elderly patients by Erturk et al.  , and they found that the addition of 20 µg fentanyl to either 8 mg heavy bupivacaine or an equivalent dose of ropivacaine in a hyperbaric solution (12 mg) provided unilateral spinal block, with sufficient motor and sensory block for major orthopedic surgeries in geriatric patients with mostly stable hemodynamics. However, Erturk et al.  found a significant decrease in the mean diastolic blood pressure in the bupivacaine group compared with the ropivacaine group, which differs from our results, which show the same trends in both groups; this may be due the clonidine additive, which impacts the same hemodynamic effects in both groups equally  . De Kock et al.  used intrathecal ropivacaine (8 mg) and clonidine in different doses for ambulatory knee arthroscopy, and they found that a small dose of intrathecal clonidine (15 µg) plus 8 mg ropivacaine produces adequate, but short-lasting, anesthesia for knee arthroscopy. These differences in results may be due to the low dose of hypobaric ropivacaine used (8 mg) in their study, whereas we used a higher dose of ropivacaine (12 mg) in the hyperbaric solution. Also, our intrathecal drugs were injected to achieve mainly unilateral spinal block. The enhancement and prolongation of motor block by intrathecal clonidine 15 µg in our study was clarified in the ropivacaine 12 mg group also as the bupivacaine 8 mg group was also mentioned by Kanazi et al.  , who used 12 mg hyperbaric bupivacaine with clonidine 15 µg although the spinal block was uniform. In our study, the only significant difference between the intrathecal combination of bupivacaine-clonidine and ropivacaine-clonidine was that the first combination had a significantly shorter onset time of sensory block. The same findings were reported by the Kanazi et al.  .
| Conclusion|| |
Adding low-dose clonidine 15 µg to an intrathecal small dose of ropivacaine (12 mg) did not change the onset of sensory block of ropivacaine compared with an equipotent dose of bupivacaine (8 mg) added to the same dose of clonidine, but it rendered the intensity and the duration of motor block and the associated hemodynamic changes of ropivacaine insignificantly different from that of bupivacaine. Either bupivacaine-clonidine or ropivacaine-clonidine injected intrathecally provides sufficient motor and sensory block in elderly patients undergoing major hip surgery without inducing hemodynamic instability.
| Acknowledgements|| |
Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]