Anesth Analg 2003;96:881-884
© 2003 International Anesthesia Research Society
REGIONAL ANESTHESIA
A Comparison of Hyperbaric 1% and 3% Solutions of Small-Dose Lidocaine in Spinal Anesthesia
Yurie Tohdoh Kawamata, MD,
Koki Nishikawa, MD,
Tomoyuki Kawamata, MD,
Keiichi Omote, MD,
Motohiko Igarashi, MD,
Masanori Yamauchi, MD,
Koichi Sato, MD,
Masayasu Nakayama, MD, and
Akiyoshi Namiki, MD
Department of Anesthesiology, Sapporo Medical University School of Medicine, Japan
Address correspondence and reprint requests to Tomoyuki Kawamata, MD, Department of Anesthesiology, Sapporo Medical University, School of Medicine, S-1, W-16, Chuo-ku, Sapporo, 060–8543, Japan. Address e-mail to kawamata{at}sapmed.ac.jp
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Abstract
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We examined whether the concentration of hyperbaric lidocaine affected the regression of motor block when the dose of lidocaine was kept constant at 30 mg. We also examined the spread, duration, and regression of sensory block. Sixty-five patients (ASA physical status I or II), scheduled for elective perineum or lower limb surgery, were enrolled in this study. Patients received spinal anesthesia with 1 mL of 3% lidocaine or 3 mL of 1% lidocaine. Adequate level of block was obtained for surgery in 63 of 65 patients. Whereas the administration of 3 mL of hyperbaric 1% lidocaine solution produced a level of sensory block similar to that produced by the administration of 1 mL of hyperbaric 3% lidocaine solution in spinal anesthesia, the administration of 3 mL of hyperbaric 1% lidocaine solution resulted in shorter times to full motor recovery and to urination and produced less motor block compared with 1 mL of hyperbaric 3% lidocaine solution. Two patients receiving 1% lidocaine and four patients receiving 3% lidocaine required IV ephedrine because of hypotension. Our results showed the clinical advantages of hyperbaric 1% lidocaine spinal anesthesia compared with hyperbaric 3% lidocaine spinal anesthesia for surgery of short duration.
IMPLICATIONS: When the dose of lidocaine was kept constant at 30 mg, hyperbaric 1% lidocaine solution resulted in shorter times for recovery from motor block and to urination than did hyperbaric 3% lidocaine solution. Levels of sensory block were similar. Therefore, the more dilute lidocaine for spinal anesthesia may be suitable for day-care surgery and short duration surgery.
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Introduction
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Spinal lidocaine has been used for ambulatory anesthesia and for anesthesia of short duration because of the rapid regression of sensory and motor blocks (1). The most important determinant of both successful surgical anesthesia and time to recovery is the total doses of local anesthetic (2,3). Dose-response effects of lidocaine on anesthesia and recovery have been examined (4,5), and the results have indicated that a smaller dose of lidocaine can result in faster recovery from spinal anesthesia. In the postoperative setting, fast motor recovery may be desirable. In addition, the incidence of transient neurological symptoms was reported to be less when small doses (30–45 mg) of 3% lidocaine were used (6). In this study, we used 30 mg of lidocaine, which was a smaller dose than had been used in spinal anesthesia with lidocaine alone in a previous study (3). It has been controversial whether the concentration affects anesthetic effects when the dose is kept constant (7,8). In this study, we examined whether the concentration of lidocaine affected the regression of motor block when the dose of lidocaine was kept constant at 30 mg. We also examined spread, duration, and regression of sensory block and side effects in spinal anesthesia.
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Methods
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Our ethics committee approved the protocol of this study, and informed consent was obtained from each patient. Sixty-five ASA physical status I or II patients, 15–86 yr old, were scheduled for elective perineum or lower limb surgery. Surgical procedures included anal fistulectomy, ultrasonically guided oocyte retrieval, incision and drainage of perianal abscess, knee arthroscopy, and minor urologic surgery. The durations of all surgical procedures were estimated not to exceed 60 min. Each patient was randomly assigned to one of two groups: a 3% lidocaine group (n = 33) in which patients received spinal anesthesia with 1 mL of 3% lidocaine in 8.2% dextrose (Astra Zeneca, Osaka, Japan) and a 1% lidocaine group (n = 32) in which patients received spinal anesthesia with 3 mL of 1% lidocaine in 7.8% dextrose (1 mL of 3% lidocaine in 8.2% dextrose + 2 mL of plain 7.5% dextrose). The specific gravity of each solution was measured at 37.0°C by a refractometer. All patients received 500 mL of IV acetate Ringer’s solution before the induction of anesthesia. Noninvasive blood pressure monitoring, electrocardiogram recording, and pulse oximeter recording were performed during the study. In the lateral position, lumbar puncture was performed at the L3-4 interspace using a 25-guage Quincke spinal needle in all patients. When clear cerebrospinal fluid (CSF) had been obtained and clear CSF had been aspirated, 1 mL of 3% lidocaine or 3 mL of 1% lidocaine solution was injected at the rate of 30 mg/10 s. After the injection of lidocaine, patients were immediately turned to the supine position. The patients received 1–2 mg of IV midazolam for relief of anxiety when required.
The level of sensory block was evaluated using pinprick method. Motor block was evaluated using the Bromage scale (0 = no motor block, 1 = inability to flex knees 30 degrees, 2 = inability to flex knees and ankle, and 3 = complete motor block). Levels of sensory block and motor block scores were recorded at 2.5, 5, 10, 15, 20, 30, and 60 min after the spinal injection and every 20 min thereafter until complete resolution of anesthesia. In addition, the times to full recovery of sensory and motor blocks were recorded. The full motor recovery was defined as 0 on the Bromage scale. If the systolic blood pressure was less than 80 mm Hg, 5 mg of ephedrine IV was administered. Side effects and the amount of supplemental analgesic medication required during anesthesia were noted. After confirmation of stable vital signs, absence of sedative effects, complete resolution of sensory block, and 0 on the Bromage scale, patients were assessed every 20 min for the ability to walk without support (time to ambulation). The time from spinal anesthesia to the first spontaneous urination was also recorded. The observers and patients were all blinded to patient group assignment.
Demographic data are presented as mean ± SD. Data on level of sensory block, degree of motor block, and time are presented as medians. A power analysis was initially conducted to determine the required size of the two groups. We assumed a SD of 27 min for time to full motor recovery (taken from our preliminary study), an  of 0.05, and a ß of 0.2. To show a 20-min difference in time to motor recovery to 0 on the Bromage scale to a power of 80%, the groups would require 29 patients each. Therefore, in the study, 65 patients were divided into two groups (n = 32 in the 1% lidocaine group and n = 33 in the 3% lidocaine group). Data were analyzed by the unpaired t-test and the Mann-Whitney test where appropriate. Data on sex were analyzed using Fisher’s exact test. A P value of <0.05 was considered to be statistically significant.
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Results
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Anesthesia was adequate for surgery in all patients, but one patient in each group did not achieve a sensory block level of anesthesia adequate for surgery because of the accidental leakage of spinal anesthetic solution from the site of the connection between syringe and spinal needle. These two patients were excluded, and 63 patients were enrolled in this study.
There were no differences in sex, age, height, and weight between the two groups (Table 1). The durations of all surgeries were within 60 min. None of the patients required supplemental analgesics during surgery.
The 1% lidocaine solution has a similar specific gravity to the 3% lidocaine solution at 37.0°C (1.040 ± 0.001 and 1.045 ± 0.001, respectively). Table 2 shows the results in this study. The median maximal levels of sensory block in the two groups were similar. The median difference between the 3% lidocaine group and 1% lidocaine group in upper level of sensory block was 0 segment (95% confidence interval [CI], -1–1). In all patients, the sensory block was observed at the first observation time (2.5 min after injection). The sensory block reached maximal level within 15 min in both groups. The median maximal degree of motor block was significantly smaller in the 1% lidocaine group than in the 3% lidocaine group (Bromage scores of 2 and 3, respectively; P < 0.05).
There were no statistically significant differences in times to full sensory recovery and to ambulation between the two groups. The mean difference of full sensory recovery and the mean difference to ambulation were 15 min (95% CI, -1–30) and 100 min (95% CI, -7–162), respectively. The time to full motor recovery was significantly shorter in the 1% lidocaine group than in the 3% lidocaine group (P < 0.05). The mean difference to full motor recovery was 27 min (95% CI, 13–40). The time to urination was also significantly shorter in the 1% lidocaine group than in the 3% lidocaine group (P < 0.05). The mean difference to urination was 86 min (95% CI, 34–137).
Two patients in the 1% lidocaine group and four patients in the 3% lidocaine group required IV ephedrine because of hypotension. Patients in the 3% lidocaine group did not have an increased risk of hypotension compared with patients in the 1% lidocaine group (odds ratio, 2.1; 95% CI, 0.3–12.2). None of the patients experienced postspinal headache or difficulty in urination until discharge from the hospital.
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Discussion
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Lidocaine for spinal anesthesia has dose-related effects on anesthesia and recovery (2,3). If adequate analgesia is provided, a smaller dose of spinal lidocaine would be preferable for surgery of short duration because this would enable faster recovery. We used 30 mg of lidocaine, which was a smaller dose than had been used in spinal anesthesia with lidocaine alone in a previous study (3). The results of our study have shown that 30 mg of lidocaine is suitable for spinal anesthesia for surgery of the lower limb and perineum that is estimated not to exceed one hour. Whereas the administration of 3 mL of hyperbaric 1% lidocaine solution produced a level of sensory block similar to that produced by the administration of 1 mL of hyperbaric 3% lidocaine solution in spinal anesthesia, the administration of 3 mL of hyperbaric 1% lidocaine solution resulted in shorter times to full motor recovery and to urination and produced a smaller degree of motor block compared with the administration of 1 mL of hyperbaric 3% lidocaine solution.
In the present study, maximum sensory block levels were similar between the groups. Many factors affect the subarachnoid distribution of local anesthetic solution. Although patient’s characteristics (age, height, and weight), site of injection, patient positioning, and baricity of anesthetics were controlled in the present study, speed of injection, volume, and concentration were different between the groups. The speeds of injection were 0.1 mL/s and 0.3 mL/s in the 3% lidocaine group and the 1% lidocaine group, respectively. Several investigators concluded that the level of sensory block depends on the dosage of anesthetics but not volume and concentration (9–11). However, the influence of injection speed has been controversial (12). In addition, it has been reported that volume of lumbosacral CSF correlates with the extent of sensory block and the duration of anesthesia (13). However, we did not estimate the volume of CSF in each patient in the present study.
Because the total dose of lidocaine given to the two groups was the same, the reasons for these differences in recovery and degree of motor block must depend on other factors such as the volumes and concentrations of the solutions. The effects of concentrations on onset time, extent, and recovery from spinal anesthesia have been examined. Manica et al. (7) examined the anesthetic effects of different concentrations of lidocaine 60 mg in spinal anesthesia. They found that injection of 4 mL of hyperbaric 1.5% lidocaine for spinal anesthesia resulted in shorter time for recovery from motor block and shorter time to void than did an injection of 1.2 mL of hyperbaric 5% lidocaine, whereas the maximum sensory block levels, the times to maximum sensory block level, and the times to full sensory recovery were similar. These findings are consistent with our results. However, Van Zundert et al. (8) reported that neither volume nor concentration affected the durations or degrees of sensory and motor blocks in isobaric lidocaine spinal anesthesia as long as the dose was kept constant (70 mg). These differences in recovery from motor block may depend on the dose administered. The doses of spinal lidocaine used in our study (30 mg) and in the study by Manica et al. (7) (60 mg) were less than that used in the study by Van Zundert et al. (8). In addition, a solution with a small concentration of lidocaine produced a lower degree of motor block than did a solution with a large concentration of lidocaine in our study but not in the study by Manica et al (7). The volume and concentration affect motor block in spinal anesthesia when a relatively small dose of lidocaine is used. However, the mechanisms underlying these effects are not clear. It has been speculated that a smaller volume of more highly concentrated solution of hyperbaric lidocaine would have a tendency to settle initially in the lower part of the spinal canal and produce a more intense motor block in the lower extremities, resulting in a longer regression time (7).
In summary, 3 mL of hyperbaric 1% lidocaine solution resulted in shorter times for recovery from motor block and to urination than did 1 mL of hyperbaric 3% lidocaine solution when injected at the rate of 30 mg/10 s, whereas levels of sensory block were similar. Hyperbaric 1% lidocaine spinal anesthesia may be more suitable for day-care surgery compared with hyperbaric 3% lidocaine.
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References
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Accepted for publication November 7, 2002.
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Abstract
Introduction
