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Abstract |
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We evaluated the effect of 25 µg of fentanyl added to bupivacaine on sensory and motor block. By using a double-blinded study design, 80 men undergoing urologic surgery were randomized into the following four groups: Group I, bupivacaine 10 mg; Group II, bupivacaine 10 mg + fentanyl 25 µg; Group III, bupivacaine 7.5 mg + fentanyl 25 µg; Group IV, bupivacaine 5 mg + fentanyl 25 µg. The final volume of intrathecal injectate was adjusted to 2.5 mL with sterile distilled water. Spinal anesthesia was administered with the 27-gauge Whitacre needle at the L2-3 interspace with the patient in the sitting position. Neural block was assessed by using pinprick and a modified Bromage scale. The degree of motor block was more profound in Group II compared with Group I at the end of operation. In Group IV, there was no motor block at the end of operation in any of the patients. The median level of the upper limit of the sensory block was higher than T7 in all groups before the start of surgery. The addition of 25 µg of fentanyl to 5 mg of bupivacaine resulted in short-acting motor block. When 25 µg of fentanyl was added to 10 mg of bupivacaine, it increased the intensity and duration of motor block. Only 5 (6.3%) of the patients needed supplemental analgesia during the operation. {abs}
Implications: Bupivacaine 5 mg with 25 µg of fentanyl for spinal anesthesia resulted in short-acting motor block. On the contrary, the addition of 25 µg of fentanyl to 10 mg of bupivacaine resulted in an increase in the motor block intensity and duration.
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Introduction |
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Spinal anesthesia has been widely used for urologic operations because it permits early recognition of symptoms caused by overhydration, transurethral resection of prostate (TURP) syndrome, and bladder perforation. In addition, short-acting spinal anesthesia may help to prevent complications associated with delayed immobilization.
Lidocaine has been a popular anesthetic for urologic procedures. When hyperbaric 2% or 5% lidocaine is used for spinal anesthesia, patients recover rapidly. However, several editorials have questioned the use of lidocaine for spinal anesthesia because of the frequency of transient neurologic symptoms (1–3). These observations generated interest in an alternative local anesthetic solution. Some investigators have examined small doses of spinal bupivacaine to be used in surgical procedures lasting less than an hour (4,5).
Lipophilic opioids (e.g., fentanyl and sufentanil) are increasingly being administered intrathecally as adjuncts to local anesthetics. They enhance spinal anesthesia without prolonging motor recovery and discharge time (6,7). This study was designed to examine whether adding 25 µg of fentanyl to bupivacaine would intensify sensory and motor block without prolonging recovery time.
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Methods |
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Eighty ASA physical status I-III patients scheduled for cystoscopic procedures, TURP, removal of bladder tumors, or other urologic procedures were studied in a double-blinded, randomized prospective manner. Patients with deformities of the spinal column, mental disturbance, or neurological disease were excluded from the study. The investigation was approved by the Ethics committee of Turku University Hospital, and written, informed consent was obtained from all patients. The patients were randomly allocated into four study groups according to a list of random numbers. The study groups according to the anesthetic solution used were as follows: Group I (n = 20), bupivacaine 10 mg; Group II (n = 20), bupivacaine 10 mg with 25 µg of fentanyl; Group III (n = 20), bupivacaine 7.5 mg with 25 µg of fentanyl; and Group IV (n = 20), bupivacaine 5.0 mg with 25 µg of fentanyl (Table 1). All solutions were prepared by using bupivacaine 5 mg/mL and fentanyl 50 µg/mL. The final volume was adjusted to 2.5 mL by using sterile distilled water.
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All patients were premedicated 1–1.5 h before surgery with diazepam 5–10 mg orally, depending on the patient’s age and weight (8). Drug therapy for concomitant medical problems was continued as deemed appropriate by the anesthesiologist. Before lumbar puncture, an IV cannula was inserted, and an infusion of NaCl 0.9% was started. The same anesthesiologist performed all the blocks. Solutions were prepared by an anesthesia nurse so that the anesthesiologist performing the block was unaware of which drug combination was injected. The final density of the solutions was 0.998, 0.999, 0.998, and 0.997 g/mL at 37°C in Groups I to IV, respectively. All solutions were hypobaric relative to spinal fluid (9–11). Spinal anesthesia was performed at the L2-3 interspace (12) with the patient in sitting position by using a 27-gauge Whitacre unidirectional needle with an introducer. Free flow of cerebrospinal fluid was verified before and after injection of the anesthetic solution, which was administered in 10 s without barbotage or aspiration at the end of injection. The direction of the needle aperture was cranial during the injection. All patients remained in the sitting position for 2 min (13) after the injection and were then placed in the lithotomy or supine position for the operation.
Patients were monitored with electrocardiography, automated oscillotonometry, and pulse oximetry. Hypotension (systolic arterial pressure <90 mm Hg or >50 mm Hg decrease from the baseline) was treated with 3-mg increments of etilefrine IV. Bradycardia (heart rate <50 bpm or decreased more than 20% from the initial value) was treated with IV atropine 0.5 mg. If the patient expressed a need for additional analgesia or exhibited an obvious need, alfentanil 0.5 mg was given IV. Respiratory depression was defined as a respiratory rate of 
8 breaths/min and/or oxygen saturation of 85% in room air. Other adverse effects, including pruritus, nausea, and vomiting, were recorded. In the majority of cases, a urinary catheter was inserted after the procedure.
The level of sensory block, defined as the loss of sharp sensation by using a pinprick test, was recorded bilaterally at the midclavicular line. Motor block in the lower limbs was assessed with reference to specific myotomes. It was done by testing the power of a specific joint movement of both lower limbs that were regarded as equivalent to the following five myotomes: L2 hip flexion, L3 knee extension, L4 ankle dorsiflexion, L5 great toe dorsiflexion, and S1 ankle plantar flexion. Complete motor block or absent power at a myotome and intensity of motor block was recorded as myotome score, which was the number of myotomes blocked from 0 to maximal 10 (14). The total score was calculated for each side, the maximum score being 5 points for one side, 10 points in total. Measurement of respiratory rate and testing of pinprick analgesia and motor block were performed at 10, 20, and 30 min, at the end of operation, 2 h from the injection, and thereafter at 30-min intervals until the motor block had completely recovered.
The patients were discharged from the recovery room when resolution of motor block was complete. The discharge criteria for the ward were stable vital signs, minimal nausea or vomiting, no severe pain or bleeding, and the motor block completely recovered. In the period after operation, the patients were interviewed regarding their opinion of the anesthetic procedure. Also, the surgeon was asked to estimate the operating conditions on a scale of good, satisfactory, and poor. In addition to testing the sensory block by pinprick, the patients were asked to report to the investigator the time when they had normal sensation in the buttocks and feet (subjective feeling of total recovery).
For postoperative pain, oxycodone 0.1 mg/kg was injected subcutaneously, if needed. The interval from the injection of spinal anesthesia to the request of first dose of analgesic and the total dose of oxycodone required in 24 h were calculated. On the third postoperative day, the patients were interviewed again regarding their opinion of the anesthetic procedure, headache or backache, and whether they would have the same anesthesia next time for a similar operation. The interview was done by telephone if the patient had been discharged from the hospital. Headache was classified as postdural puncture headache (PDPH) if it was aggravated by erect or sitting position, relieved on lying flat, mainly occipital or frontal, and increased on coughing, sneezing, or straining. Transient neurological symptoms (TNS) were defined as pain and/or dysesthesia in the back, buttocks, and legs or pain radiating to the lower extremities after initial recovery from spinal anesthesia, and resolved within 72 h.
The statistical analysis was conducted mainly with nonparametric methods. First, the overall differences among the four groups were tested with Kruskal-Wallis test. If there were significant differences among the four groups, the analysis was continued with post hoc comparisons of differences between pairs of groups by using Mann-Whitney’s U-test. Multiple comparison correction was performed with Bonferroni correction. The comparison of four groups in demographic data and the duration of surgery was done with parametric one-way analysis of variance. P values <0.05 were interpreted as statistically significant. The computations were performed with SAS System for Windows, release 6.12/1996 (SAS, Cary, NC).
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Results |
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Patients’ demographic data and duration of surgery are listed in Table 1. The four groups were comparable with respect to age, height, and weight. However, the operation times in Group IV were shorter than in the other groups (P < 0.01). There was no difference among the other three groups.
The motor block assessments are presented in Figure 1. In Group IV, in which the dose of bupivacaine was the smallest (5 mg), there was no motor block in any of the patients at the end of operation. In this group, there were also six patients (30%) who had no motor block after the injection; yet none of the patients needed supplementation of analgesia during the operation and the surgeons were satisfied with the intensity of the motor block. There were statistically significant differences between groups in the motor block (P < 0.001). Group II resulted in the longest duration of the motor block (P < 0.001) and Group IV the shortest duration (P < 0.001). Between Groups I and III there was no statistically significant difference in the duration of the motor block. The degree of motor block was more intense in Group II compared with Group I at the end of operation. A complete motor block (altogether 10 myotomes blocked, from L2 to S1 at each side) was found in 16 of 20 patients in Group I and 19 of 20 patients in Group II during the anesthesia.
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The sensory block assessments are summarized in Figure 2. The median of the upper limit of the sensory block was greater than T7 in all groups at the 30-min testing time, just before the operation began. The mean duration of subjective block in Group I was 3 h 53 min; in Group II, 4 h 48 min; Group III, 3 h 46 min; and Group IV, 2 h 16 min.
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Two patients in Groups I and III, one patient in Group II, and four patients in Group IV had hypotensive episodes. On each occasion, the blood pressure returned to normal after one or two increments of IV etilefrine 3 mg and an infusion of 500 mL of NaCl 0.9%. Three patients needed treatment for bradycardia. In all patients who received fentanyl, pruritus was the most common complication (30%). There were no spontaneous reports of pruritus. Thirty-two patients (40%) required analgesics postoperatively within the first 24 h. PDPH or TNS were not documented in any patient (Table 2).
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When interviewed on the third postoperative day, 97.5% of the patients rated the anesthesia method as good, and 100% would choose this anesthesia in the future for a similar operation.
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Discussion |
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This study suggests that the addition of 25 µg of fentanyl to 10 mg of bupivacaine prolongs and intensifies the motor block. Of interest, 5 mg of bupivacaine with the 25 µg of fentanyl resulted in short-acting motor block but the same level of sensory analgesia as the dose of 7.5 or 10 mg of bupivacaine with the addition of fentanyl or the 10-mg dose of bupivacaine without fentanyl. The patients in Group IV could have been discharged home on the day of surgery according to standard discharge criteria. On follow-up, 97.5% of the patients rated the anesthesia method as good and 100% would choose this anesthesia in the future for a similar operation.
Several investigators have evaluated intrathecal fentanyl with smaller doses of spinal local anesthetics. Liu et al. (15) found that fentanyl 20 µg in combination with spinal lidocaine (50 mg) prolonged sensory anesthesia without prolonging recovery of motor function or time to micturition. Sensory block was prolonged in both thoracic and lumbar dermatomes with the addition of fentanyl. Furthermore, Ben-David et al. (6) found that a small dose of fentanyl (10 µg) added to spinal anesthesia with a small dose of dilute bupivacaine (5 mg) in ambulatory patients undergoing knee arthroscopies intensified and increased the sensory blockade without increasing the intensity of motor block or prolonging recovery of micturition or street fitness.
We added fentanyl to bupivacaine to determine its effect on anesthesia quality, motor block, and sensory block. In this study, the addition of fentanyl (25 µg) to 10 mg of bupivacaine intensified the motor block. A statistical difference was found between Groups I and II in the motor block intensity between time points from two to three hours after the injection. In addition, the motor block seems to be more intense toward the resolution of the entire motor block. With the difference in the mean values and standard deviations of motor block intensity in our study, the sample size should have been approximately 100 in both groups to show a significant difference from three hours forward. Compared with all the other groups, the duration of the motor block was longest in Group II (P < 0.001). One explanation of this observation could be that both the fentanyl and the bupivacaine doses were larger than in the study by Ben-David et al (6).
When large doses of local anesthetics are used, the sensory and motor blocks develop rapidly as a result of an overdosage in relation to the minimum concentration required to block the various nerve fiber types. Even though the motor block was not complete with 5 or 7.5 mg of bupivacaine and fentanyl addition, more intense motor blocks were not requested by the surgeons. However, the shortest and least invasive procedures were performed on the patients with the least dense blocks, which may in part explain the lack of additional need for analgesia. It should also be pointed out that an incomplete motor block might be contraindicated in some urologic procedures in which movements may result in a bladder perforation.
It can be assumed that the recovery and mobilization of the patient could be faster if the motor block was less intense. In the study by Vaghadia et al. (16), a small-dose hypobaric lidocaine-fentanyl spinal anesthesia had advantages over conventional-dose hyperbaric lidocaine, including less hypotension and faster motor and sensory recovery. In our study, the duration of motor block was prolonged in Group II compared with Group I. The dose of bupivacaine was 10 mg in both groups, but in Group II, there was the 25-µg dose of fentanyl added to the anesthetic solution and the duration of subjective block was the longest. This observation is in accordance with earlier studies in which duration of the block is found to be dose-related when using either lidocaine (17) or bupivacaine (18).
Posture, when plain bupivacaine is injected intrathecally, influences the spread of sensory anesthesia (13,19). All patients in the current study had the anesthetic solution injected into the subarachnoid space at the L2-3 interspace while in the seated position. The sitting position was maintained for two minutes, thereby enhancing the spread of the block into the upper thoracic dermatomes. The median level of the upper limit of the sensory block reached T7 in all four study groups. Furthermore, the duration of the block is a function of total milligram dose and the extent of spread (20).
Pruritus is a common complication when intrathecal opioids are used (21). Liu et al. (15) found that the addition of 20 µg of fentanyl intrathecally led to pruritus in all patients. In the current study, pruritus was also the most common adverse effect, occurring in 22.5% of all patients. It was well tolerated; none of the patients needed treatment. In the study by Vaghadia et al. (16), pruritus was also found to be of mild to moderate intensity.
The administration of intrathecal opioids may provide benefits in augmenting intraoperative anesthesia, but carries a risk of respiratory depression (22). Fentanyl is much more lipid-soluble than morphine and hence does not tend to migrate intrathecally to the fourth ventricle in sufficient concentrations to cause respiratory depression. Varassi et al. (23) demonstrated that the subarachnoid administration of 25 µg of fentanyl during spinal anesthesia in nonpremedicated elderly men did not alter respiratory rate, end-tidal tension of CO2, minute ventilation, respiratory drive, respiratory timing, or the ventilatory response to CO2. On the contrary, 50 µg of subarachnoid fentanyl could cause an early respiratory depression in elderly patients.
In conclusion, the addition of fentanyl 25 µg to bupivacaine 5 mg resulted in short-lasting motor block but the same level of sensory analgesia as larger doses of bupivacaine (7.5–10 mg) with or without fentanyl. When fentanyl 25 µg was added to bupivacaine 10 mg it increased the duration and intensity of motor block.
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