|Year : 2018 | Volume
| Issue : 4 | Page : 275-280
A comparative study between epidural fentanyl, magnesium sulfate, or both for postoperative analgesia in hip surgeries
Hend A Ghoneem, Mohamed A El-Harty, Ahmed A El-Daba, Shaimaa F Mostafa
Department of Anesthesia and Surgical Intensive Care, Faculty of Medicine, Tanta University, Tanta, Egypt
|Date of Submission||20-Mar-2017|
|Date of Acceptance||07-Feb-2018|
|Date of Web Publication||02-Aug-2019|
Hend A Ghoneem
Department of Anesthesia and Surgical Intensive Care, Faculty of Medicine, Tanta University, Garahem St., Kafr El-Zayat, El-Gharbia, Tanta
Background Postoperative analgesia after hip surgeries is important for adequate recovery and early mobilization. Epidural analgesia is one of the most accepted techniques.
Aim The aim was to evaluate the analgesic efficacy of single bolus administration of epidural fentanyl, magnesium sulfate, and a combination of both in patients undergoing hip surgeries under spinal anesthesia.
Patients and methods Ninety patients, 20–65 years, American Society of Anesthesiology I–III, undergoing elective hip surgery under spinal anesthesia were investigated. After wearing off of spinal anesthesia, the patients were allocated into three groups to receive single bolus epidural injection of fentanyl 1 µg/kg in the fentanyl (F) group, magnesium sulfate 75 mg in the magnesium sulfate (M) group, and a combination of both in the fentanyl magnesium sulfate (FM) group. All were diluted to a total volume of 10 ml. Visual analog scale, duration of analgesia, and total consumption of rescue analgesia were recorded.
Results A combination of epidural fentanyl (1 µg/kg) and magnesium sulfate (75 mg) produced a significant reduction of postoperative visual analog scale at 3 and 6 h with a longer duration of analgesia and a lower rescue analgesic consumption without increased side effects.
Conclusion Epidural fentanyl and magnesium sulfate provides adequate postoperative analgesia but with short duration. However, addition of magnesium sulfate as an adjuvant to epidural fentanyl improves the quality of postoperative analgesia, reduces the demand for rescue analgesia, and prolongs the duration of analgesia without additional side effects.
Keywords: epidural analgesia, fentanyl, hip surgery, magnesium sulfate
|How to cite this article:|
Ghoneem HA, El-Harty MA, El-Daba AA, Mostafa SF. A comparative study between epidural fentanyl, magnesium sulfate, or both for postoperative analgesia in hip surgeries. Tanta Med J 2018;46:275-80
|How to cite this URL:|
Ghoneem HA, El-Harty MA, El-Daba AA, Mostafa SF. A comparative study between epidural fentanyl, magnesium sulfate, or both for postoperative analgesia in hip surgeries. Tanta Med J [serial online] 2018 [cited 2020 Feb 29];46:275-80. Available from: http://www.tdj.eg.net/text.asp?2018/46/4/275/263918
| Introduction|| |
Postoperative pain following hip surgeries is often considered moderate to severe and can result in delayed mobilization and prolonged hospitalization. This has been managed by epidural analgesia, peripheral nerve blocks, and parenteral or spinal opioids . Postoperative epidural analgesia is one of the most commonly used and accepted techniques .
Various adjuvants have been added to opioids epidurally to prolong analgesia and reduce the adverse effects observed when opioids are used alone. Owing to its high lipid solubility, fentanyl offers some advantages for epidural analgesia. Owing to rapid onset and short duration of action of fentanyl, it is the drug of choice for postoperative acute pain .
N-methyl-d-aspartate (NMDA) receptors located in the dorsal horn of the spinal cord have a role in the modulation of central sensitization of noxious stimulus .
Magnesium, through a noncompetitive mechanism, blocks the NMDA receptors and results in natural calcium antagonism  and, when administered epidurally, is proved to prolong the duration of spinal opioid analgesia ,.
Aim and objectives
The aim of this study was to compare the postoperative analgesic effects of single bolus epidural administration of fentanyl, magnesium sulfate, and a combination of both in patients undergoing hip surgeries under spinal anesthesia.
| Patients and methods|| |
After approval of Tanta Faculty of Medicine research ethics committee (code: 2849/11/14) and informed written patient consent, this prospective, randomized double-blind study was carried out in the Orthopedic Surgery Department, Tanta University Hospital, on 90 adult patients of either sex, 20–65 years old, American Society of Anesthesiology I–III undergoing elective hip surgery under spinal anesthesia.
Exclusion criteria included patient refusal, patients with any contraindication for regional anesthesia such as infection at the puncture site, anatomic deformities or coagulation disorders and patients with hypersensitivity to the study drugs.
Preoperative assessment was done by history taking, clinical examination, laboratory investigations, renal, hepatic, and by cardiac function assessment.
All patients were premedicated using intravenous midazolam 0.05 mg/kg 15 min before surgery. Combined spinal epidural anesthesia was performed in all patients in sitting position at L4–5 level using the needle through the needle technique. Monitoring included 3-lead ECG, pulse oximetry, and noninvasive arterial blood pressure measurement. After an epidural test dose of 45 mg lidocaine and 1 : 200 000 adrenaline in a volume of 3 ml was administered ; spinal anesthesia was initiated using 15 mg (3 ml) of hyperbaric bupivacaine 0.5%.
Intraoperatively, patients who developed hypotension (defined as mean arterial blood pressure <60 mmHg) were managed by intravenous crystalloids, injection of intravenous ephedrine 5–10 mg bolus. Intravenous atropine (0.6 mg) was given to those who developed bradycardia (defined as heart rate <60 beats/min).
Postoperatively, after wearing off spinal anesthesia, patients were randomized by computer-generated random number assignment into three groups of 30 patients each to receive a single bolus dose of either epidural fentanyl, magnesium, or both. The drugs were prepared in identical syringes by an independent investigator who had no subsequent role in the study. Group I is the fentanyl group (F): patients received fentanyl (50 µg/ml) in a dose of 1 µg/kg diluted in isotonic saline to a total volume of 10 ml. Group II is the magnesium sulfate group (M). patients received magnesium sulfate 10% (100 mg/ml) in a dose of 75 ml diluted in isotonic saline to a total volume of 10 ml. Group III is the fentanyl magnesium sulfate group (FM): patients received fentanyl in a dose of 1 µg/kg and magnesium sulfate in a dose of 75 mg diluted in isotonic saline to a total volume of 10 ml.
The primary outcome was the postoperative pain which was assessed using the visual analog scale (VAS) at wearing off spinal anesthesia, 1, 3, 6, 12, and 24 h postoperative. Rescue analgesia in the form of pethidine 20 mg intravenously was given if VAS was greater than or equal to 4. Secondary outcome included a total of 24 h rescue analgesic consumption as well as the duration of postoperative analgesia.
Any postoperative side effects were recorded (e.g. nausea, vomiting, excessive sedation, respiratory depression, shivering, and pruritis). Patient sedation was assessed on a four-point scale  (0: awake and alert, 1: mildly sedated, easily awakened, 2: moderately sedated, awakened by shaking, 3: deeply sedated, difficult to be awakened by physical stimulation). Patient satisfaction was assessed on a three-point scale  (0: dissatisfied, 1: fair, 2: satisfied).
Sample size calculation was based on the reduction of postoperative VAS. Based on the results of previous studies  at least 29 patients in each group were needed to detect a significant reduction of 90% at an α error of 0.05 and a study power of 80%.
We used SPSS 16 software (SPSS Inc., Chicago, Illinois, USA) for statistical analysis. Kolmogorov–Smirnov test was performed for verification of the assumption of normality. Quantitative data were described as mean±SD and one-way analysis of variance with post-hoc Tukey’s Honest Significant Difference (HSD) test was used for comparison between groups. Categorical data were described as number or frequencies (%) and χ2-test was used for comparison between groups. A P value of less than 0.05 was considered significant.
| Results|| |
- 102 patients were investigated for enrollment in the study. Nine patients did not meet the inclusion criteria and three patients refused to participate in the study. Ninety patients were enrolled and were divided into three groups ([Figure 1]).
|Figure 1 Consolidated Standards of Reporting Trials (CONSORT) flow diagram.|
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- Demographic data as regards age, sex, weight, and duration of surgery were comparable between the studied groups (P>0.05) ([Table 1]).
- VAS scores were comparable between groups at 0, 1, and 24 h postoperatively. (P>0.05). At 3 and 6 h postoperative, VAS scores were significantly lower in the FM group compared with F and M groups (P<0.05). No significant changes were detected in VAS scores between F and M groups at any time during the study ([Figure 2]).
- Duration of analgesia was significantly longer in the FM group (395±90.54 min) compared with the F group (220±52.46 min) and M group (219±51.02 min) (P<0.05). However, comparison between F and M groups was statistically insignificant (P>0.05) ([Table 2]).
- Total 24 h rescue analgesic consumption was significantly lower in the FM group (28.66±10.08 mg) compared with the F group (36±12.21 mg) and M group (40±14.86 mg) (P<0.05), while the consumption was comparable between F and M groups (P>0.05) ([Table 2]).
- No significant adverse effects were detected in any of the studied groups ([Table 3]).
|Table 3 Postoperative complications, sedation and patients’ satisfaction.|
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- Patient satisfaction was comparable between the studied groups ([Table 3]).
| Discussion|| |
Adequate postoperative analgesia is essential to enhance postoperative recovery and reduce morbidity . Our study showed that a combination of epidural fentanyl and magnesium sulfate resulted in lower VAS scores, longer duration of analgesia, and less rescue analgesic consumption than epidural fentanyl or magnesium sulfate alone ([Figure 2]).
The use of epidural analgesia for pain relief was improved by the use of epidural opioids after the discovery of opioid receptors in the dorsal horn of the spinal cord. Fentanyl is a suitable opioid for infusion into the epidural space. Advantages of fentanyl over other opioids are that it easily crosses the lumbar dura and quickly penetrates the lipid phase of the underlying tissue of the cord .
Various adjuvants have been added to opioids epidurally to prolong analgesia and reduce the side effects observed when opioids are used alone ,.
Magnesium, which is the fourth most plentiful cation in the body, is proved to have antinociceptive effects in animal and human models of pain ,. This effect is based on the regulation of calcium influx into the cell, that is natural physiological calcium antagonism and antagonism of NMDA receptors .
Coadministration of epidural magnesium for postoperative epidural analgesia has provided a pronounced reduction in patient-controlled fentanyl consumption without any side effects .
Our results are in accordance with those of Santhisree et al.  and Sonali et al. , who reported the benificial analgesic effect of epidural magnesium (75 mg) as an adjuvant to epidural fentanyl (50 µg) in patients undergoing hip surgery.
Fentanyl offers some advantages for epidural analgesia because of its greater lipophilic nature and rapid vascular absorption from the epidural space ,.
Magnesium-induced block of calcium influx  blocks central sensitization which is considered to be one of the mechanisms implicated in the persistence of postoperative pain . Noncompetitive NMDA receptor antagonists can have an effect on pain when used alone, but it has also been shown that they can reveal the analgesic properties of opioids ,. In this manner, the coadministration of magnesium and an opioid is expected to allow a significant reduction in opioid administration for postoperative pain alleviation ,. Other studies have reported the analgesic effects of epidural magnesium ,.
As regards the duration of postoperative analgesia, our results agree with those of Shiva et al.  and Morrison et al. , who reported on additive analgesic effects of coadministration of epidural magnesium sulfate.
However, Bilir et al.  studied the effect of epidural fentanyl or fentanyl plus magnesium sulfate (50 mg) as an initial bolus dose followed by a continuous infusion of 100 mg/day for 24 h for hip surgery and found that there was no significant difference between groups in the time to first analgesic requirement. This may be due to the usage of small initial dose of magnesium sulfate (50 mg).Effects of neuroaxial magnesium sulfate on reduction of postoperative rescue analgesia were also reported in many previous studies ,,. Sun et al.  suggested that the addition of magnesium changed the pH of the bupivacaine solution which caused a delayed uptake of bupivacaine from the epidural space and prolonged the period of sensory and motor blockade.
On the contrary, Dayioglu et al.  found no difference in total analgesic consumption in the first 24 h when added intrathecal magnesium to bupivacaine and fentanyl in knee arthroscopy.
No increased incidence of hypotension, nausea, vomiting, or sedation were detected in our results as well as those of other studies ,,.
Limitations of our study included the relatively small number of patients investigated. We recommend further study to evaluate lower doses of magnesium sulfate as an additive to epidural fentanyl.
| Conclusion|| |
Epidural fentanyl (1 µg/kg) or epidural magnesium (75 mg) provide good postoperative analgesia but with short duration; however, coadministration of epidural magnesium (75 mg) with fentanyl (1 µg/kg) improves the quality of postoperative analgesia, reduces the demand for rescue analgesia, and prolongs the duration of analgesia without additional side effects.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]