Single-dose spinal anesthesia is a simple, highly effective and economic technique, which seems to be very safe (1,2) (3) (4)
For this reason, the incidence of spinal puncture problems should be as infrequent as possible. The need of a spinal needle that combines optimal puncture conditions with an infrequent incidence of side effects resulted in variant needle sizes and designs. However, technical improvements have sometimes killed the advantages of spinal needles. For example, small-bore needles (diameter <0.45 mm), which have been developed to reduce the incidence of PDPH (5–8) (9)
Besides the diameter (10) (11) (12)
For this reason, a new spinal needle was designed that consists of a conical pencil-like tip formed by a stylet, which is withdrawn after penetration of the dura (Fig. 1 ). After removal of the stylet, the spinal needle presents a relatively large hole at the tip of the needle that, theoretically, allows subsequent and unimpaired CSF flow.
Figure 1.:
The Ballpen (B) spinal needle. (A) Stylet in initial position forming the atraumatic needle tip during dural puncture. (B) Withdrawal of stylet after dural penetration. (C) Removed stylet opens the terminal hole and allows free flow of cerebrospinal fluid (CSF) through the needle.
The present prospective, randomized, comparative multicenter study compares this newly designed noncutting needle (Ballpen [B]) with the widely used noncutting Sprotte (S) needle, because spinal needles with a pencil-like tip represent the “gold standard” in spinal anesthesia (13)
Methods
After approval of the local ethics committees and informed written consent, 700 patients were included in the study. In patients younger than 18 yr, both patients and parents gave their written consent. The study was performed in 4 different hospitals: 3 university hospitals (Hamburg H1, Hannover H2, and Mainz H4), and 1 large community hospital (Karlsruhe H3). Three centers (H1, H3, and H4) participated in a pilot study where 100 B needles were used in each hospital. All patients were scheduled for lower abdominal or extremity surgery and underwent the same standardized protocol. Low molecular weight heparin (20 mg) was given once a day in the evening to guarantee an interval of at least 12 h between low molecular weight heparin application and spinal anesthesia, and subcutaneous unfractionated heparin 5000 U was given 4 h before and 2 h after spinal puncture at the earliest. According to the German guidelines, aspirin intake was suspended at least 3 days before surgery unless investigators decided to maintain aspirin therapy until the day before surgery. Exclusion criteria were coagulation abnormalities, mental or spinal abnormalities, acute neurologic disease, local anesthetic allergies, local or systemic infection, and patient refusal.
After oral premedication with midazolam, patients received an IV cannula and 500 mL of Ringer’s lactate solution. Monitoring consisted of electrocardiogram, noninvasive blood pressure measurement, and pulse oximetry. With the patient in the sitting position, a deep skin infiltration with 3–5 mL of lidocaine 1% was performed for local anesthesia at the L3-4 interspace, which was identified by palpating the iliac crest. After three unsuccessful punctures at the first interspace, the fourth puncture was made at the L2-3 or L4-5 interspaces, whichever seemed to be more appropriate, by a more experienced anesthesiologist. There was no limit for the number of attempts or performance time. The moment when the 20-gauge introducer needle was inserted into the skin was assessed as the start of the performance time. The spinal puncture was performed using the midline approach with a 25-gauge B needle (Rüsch, Kernen, Germany) or a 25-gauge S needle (Pajunk, Geisingen, Germany) according to a randomization protocol that was created by a computerized program for each study site. The performance time was terminated when free flow of CSF was detected in the hub of the spinal needle. For subarachnoid anesthesia, 0.5% bupivacaine (AstraZeneca, Plankstadt, Germany) was injected in a dose of 2 mL (height, <160 cm), 2.5 mL (height, 160–170 cm), 3 mL (height, 171–180 cm), or 3.5 mL (height, >180 cm). During injection, the lateral orifice of the S needle was directed cranially. An analgesic level of at least T12 was the target for lower extremity surgery and of ≥T10 for lower abdominal or urologic surgery. In three hospitals (H1–H3), plain bupivacaine was injected as the local anesthetic, whereas in one study center (H4), hyperbaric bupivacaine was also used. Other than the time for technical performance, the number of attempts for spinal puncture, the frequency of bloody taps, paresthesias during spinal puncture and subarachnoid injection, and the number of failures (patients required general anesthesia for surgery) were recorded. Twenty minutes after the local anesthetic injection, the maximal analgesic level was assessed using cold swabs or sprays, and the highest degree of motor block was assessed using the Bromage scale (0 = none, full flexion of both legs against gravity; 1 = partial, patient is able to move feet and knees but is not able to elevate his legs against gravity; 2 = almost complete, patient is able to move feet but not knees; and 3 = complete, patient is unable to move feet or knees). Any requirements for sedatives or analgesics during surgery were recorded. The incidence of bradycardia (heart rate, <50 bpm) and hypotension (mean arterial blood pressure minus 30% from baseline) was also recorded. During postoperative Day 2 and 4, all patients were visited by an anesthesiologist who was blinded to the type of spinal needle. Patients were interviewed about postoperative complaints such as headache, PDPH, backache, transient neurological symptoms, and major neurological deficits. Patients were also asked if they had an earlier experience with spinals, if they remembered any postoperative problems associated with earlier spinals, such as PDPH, backache, or transient neurological symptoms, and if they were satisfied with the actually performed technique of spinal anesthesia (possible answers were “yes” or “no”).
For sample size calculation on the basis of retrospective data from our institution in a comparable patient population, a power analysis was performed by using the time for the technical performance of spinal anesthesia as the primary outcome variable. This time was defined as the time between insertion of the introducer needle and the first identification of CSF in the hub of the spinal needle. We set 100 s as the predicted value for the control (S) group, with an estimated pooled sd of 100 s. For calculation of the sample size, we defined the smallest difference we decided to be clinically significant as 25%. We would permit a type I error of α = 0.05, and with the alternate hypothesis, the null hypothesis would be retained with a type II error of β = 0.1. This analysis reached a power of 0.9 and indicated that a sample size of at least 337 patients per group was required. The randomization was performed by using a Microsoft Excel Makro (Microsoft Corp, Redmond, WA). Computerized statistical analysis was performed using SPSS 9.0 (SPSS Inc, Cary, NC) and Instat 2.1 (Graphpad Inc, San Diego, CA). Data are given as mean ± sd unless otherwise indicated. Statistical analysis included Kolmogorov-Smirnov test and independent sample t -test or analysis of variance with Tamhane’s T2 post hoc test for multiple comparisons. Categorical data were analyzed using Fisher’s exact test. A value of P < 0.05 was considered to be statistically significant.
Results
Twenty-three patients (15 in Group B, and 8 in Group S) were excluded from the final evaluation because of missing data. Of the 677 patients with completed files, 237 were included from Hamburg, 200 from Hannover, 162 from Mainz, and 78 from Karlsruhe, respectively. The demographic and perioperative data did not show significant differences between Groups B and S (Table 1 ). Table 2 gives on overview on the technical details of spinal anesthesia with the respective needle. In seven patients, the spinal puncture was performed in the lateral position, because these patients were not able to sit. CSF flow was obtained after the first puncture in 79.1% with the B and in 79.5% with the S needle. The distribution of the rest of the lumbar puncture attempts was comparable in both groups: 2 attempts in 6.8% versus 8.9%, 3 attempts in 8.8% versus 4.8%, and more than 3 attempts in 5.3% versus 6.8% of Groups B and S, respectively. The time for performance of spinal anesthesia was 98 ± 145 s in Group B and 103 ± 159 s in Group S (P = 0.68), with a range of 30–600 s in Group B and 30–1200 s in Group S. Figure 2 shows the mean time for performance of spinal anesthesia in each hospital. Whereas in two hospitals (H1 and H3) there was a trend for shorter performance times with the B compared with the S needle, no difference was seen in H4, although a trend for a longer performance time was found with the B needle in H2. However, the performance time with the S needle was less in H2 when compared with H1 and H3 (P < 0.01).
Table 1:
Table 2:
Figure 2.:
Performance time (mean ± sem) in single-dose spinal anesthesia with a 25-gauge Ballpen (B) or Sprotte (S) needle, depending on the respective study center (H1–4). Mean = mean performance time over all hospitals. +P < 0.01 versus H1; #P < 0.01 versus H3.
Intraoperative sedation with midazolam was performed in 66% of the patients in Group B and in 62% in Group S (P = 0.38). Intraoperative systemic opioids were required in 6% and 7% of Group B and S, respectively (P = 0.60).
The range of the obtained maximal analgesic level was L1 to T3 (median T10) in Group B and L2 to T5 (median T9) in Group S (P = 0.51), with 54 (B) versus 73 (S) patients presenting analgesic levels more than T8 (P = 0.047). The percentage distribution of the degree of motor block (Bromage 0/1/2/3) was 87%/10%/2%/1% in Group B and 88%/8%/2%/2% in Group S (P = 0.71). The failure rate of spinal anesthesia (general anesthesia required) was 3.8% in Group B and 3.9% in Group S (P = 0.85).
Intraoperative side effects of spinal anesthesia and postoperative complaints are presented in Table 3 . There was a more frequent incidence of hypotension in Group S when compared with Group B (P < 0.01). The incidence of PDPH and other postoperative complications related to spinal anesthesia were comparable between groups. No patient required an epidural blood patch. Earlier experience with spinal anesthesia was stated in 36% and in 40% of Groups B and S, respectively (P = 0.33). Problems with earlier spinal blockades were reported by 34 patients in Group B and 23 patients in Group S (P = 0.18). Ninety-five percent of the patients in Group B and 93% in Group S were content with spinal anesthesia (P = 0.3).
Table 3:
Discussion
This study evaluated the technical characteristics of two noncutting spinal needles, the new B needle and the widely used S needle. The B needle was designed to provide a combination of good puncture conditions with early identification of CSF along with an infrequent incidence of PDPH.
In contrast to the theoretical improvements in the novel needle design, the present data did not reveal significant technical advantages of the B over the S needle. Performance time, technical difficulties, and failure rates were comparable between groups. However, the number of multiple attempts and failure rates were small in both groups when compared with earlier studies showing an incidence of 8%–25%(5–9)
Based on the experience of the pilot study with the new B needle in three centers, we had hypothesized a significantly reduced performance time in the B group because of a possibly more rapid placement of the needle within the subarachnoid space and a faster identification of CSF. There may be several explanations for the lack of significance between the two groups on this point. The performance time, defined as the time between first insertion of the introducer needle in the skin and the first identification of CSF in the hub of the needle, might theoretically have been biased by different insertion times for the placement of the introducer needle itself. However, the variations in time between introducer placement and spinal needle insertion should be negligible and, more importantly, are not related to the different technical characteristics of the examined spinal needles.
Whereas no differences in the time of personal practice in anesthesia were seen between anesthesiologists of the two groups, there was a difference in training time with the new B needle between one hospital and the rest, which possibly may have resulted in different performance times (Fig. 2 ). In three hospitals (H1, H3, and H4), anesthesiologists had the opportunity to use 100 of the B needles in a pilot study before the comparative study was begun. This training may explain the trend to shorter performance times with the B in comparison with the S needle in these hospitals. However, H2 was also the center with the shortest performance time for the B needle. Thus, it is not likely that the preceding pilot study significantly influenced the results obtained in this study.
Increased failure rates in spinal anesthesia have been described with both small-bore (5–8) (14,15) (16) Fig. 1A ). When this area of the B needle penetrates the tented dura, it creates a typical click, allowing identification of correct needle position. Second, when the stylet is withdrawn (Fig. 1C ), the large diameter of the terminal hole allows immediate and free CSF flow, the most important indicator for correct placement of the spinal needle. Other than errors in the judgment of pharmacological factors of the local anesthetic (17,18) (9,18)
Under the assumption that there is technical advantage with a new spinal needle, the infrequent incidence of PDPH, which is obtained with noncutting spinal needles such as the S or Whitacre, even in high-risk patients, such as young patients (19) (20) (21) (13) Fig. 1B ).
Side effects of spinal anesthesia were comparable between groups except for hypotension, which was more frequent in the S group than in the B group. One may speculate that there were more patients with a more profound sympathetic blockade and resultant hypotension in the S group, because in this group, more patients showed an analgesic level higher than T8. However, this result can hardly be attributed to the different needle design.
In conclusion, our study failed to show significant technical advantages of the newly designed B needle over the S needle, a representative of the gold standard of noncutting needles for spinal anesthesia. However, more experience in a larger number of patients may possibly reveal benefits of the B needle, e.g., in patients with difficult anatomy where the dural click during puncture and clear and when unequivocal CSF flow is extremely helpful to identify the correct subarachnoid position of the needle tip.
The authors would like to thank the staff of their departments for their help in performing the study and collecting the patients’ data. The colleagues who were involved in the study at respective centers are: Gerhard Kessler, MD, Rainer Dietz, MD, Fabian Herbst, MD, Khaled Rafiqpoor, MD, from Hamburg, Frederico Latorre, MD, Gunnar Jähnichen, MD, from Mainz, and Stefan Brugger, MD, from Karlsruhe.
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