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Department of Anesthesiology and Reanimation, Atatürk University, Erzurum, Turkey
Address correspondence and reprint requests to Mehmet Cesur, Yunus Emre Mah Tomurcuk Sok, Ikizler Apt. B Blok No: 7/7, 25080 Yenisehir/Erzurum, Turkey. Address e-mail to mcesur{at}atauni.edu.tr.
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Introduction |
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Methods |
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Patients were assigned into two equal groups using a computer-generated randomization list. In the needle group, the epidural catheters were advanced into the epidural space after a single injection of a full dose of local anesthetic (20 mL of 2% lidocaine) through the needle. In the catheter group, the epidural catheters were inserted without injection of any solution and local anesthetic was then injected via the catheter. All procedures were performed by the same experienced anesthesiologist.
On arrival in the operating room, automatic noninvasive arterial blood pressure monitoring, electrocardiograph, and pulse oximetry were commenced, and 10-15 mL/kg of Ringer’s lactate solution was infused before the procedure. Baseline demographic data and vital signs were recorded before surgery. All patients were premedicated with 3 mg of midazolam and 0.5 mg of atropine IM. With the patient in the left lateral position, lumbar epidural punctures were performed at the L4-5 or L3-4 interspace using a midline approach with 18-gauge Tuohy needles and the loss-of-resistance technique with 1-2 mL of saline. In the needle group, after identification of epidural space and a negative aspiration test for blood or cerebrospinal fluid, 3 mL of 2% lidocaine with epinephrine 5 µg/mL was injected through the needle as a test dose. The syringe was then disconnected to observe for drip back. The patients were also observed for any increase in heart rate that would indicate an intravascular injection of epinephrine and were questioned about dizziness, tinnitus, a metallic taste in the mouth, or sudden warmth or numbness in the legs. If these responses were negative after 5 min, the remainder of the full 20 mL of local anesthetic was injected in 3 divided doses. A 20-gauge multiorifice epidural catheter (Minipack; Portex Ltd., Kent, UK) was inserted 3 cm into the epidural space through the cranially directed tip of the epidural needle. After removal of the Tuohy needle, the catheter was fixed to the skin, and the patients were turned to the supine position. In the catheter group, identification of the epidural space, aspiration test, test dose, and incremental injection were performed as before, except that no local anesthetic was injected before catheter placement.
Paresthesia during insertion of the catheter, inability to advance the catheter, and IV and subarachnoid cannulation were noted by the attending anesthesiologist (i.e., not a blinded independent observer). IV or subarachnoid cannulation was detected by aspiration of frank blood or cerebrospinal fluid through the catheter. If intravascular or subarachnoid cannulation occurred, the catheter was withdrawn 1 cm. If this did not lead to withdrawal from the vein or subarachnoid space, the catheter was removed. If it was not possible to thread the catheter, it and the needle were withdrawn together. The procedure was then repeated at a different level; if unsuccessful again, general anesthesia was given. In the needle group, if the catheter could not be advanced and the surgery was of short duration, surgery was commenced under single-injection epidural anesthesia. These patients were excluded from the analysis.
Twenty minutes after the main dose, sensory block levels and the degree of motor block were assessed bilaterally by a blinded independent observer. Sensory block was assessed with ice and motor block by the Bromage scale (0 = no block, 1 = hip movement block, 2 = hip and knee block, and 3 = complete block in hip, knee, and ankle). Complete loss of cold sensation to T8 on both sides was regarded as sufficient for surgery.
The term "failed epidural" was used for situations in which either it was impossible to insert the catheter or there was no sensory block after injection of the local anesthetic (9). Unilateral block, unblocked sacral segments, low level and unblocked segments, or a patchy block were regarded as "incomplete block" before surgery (9). If these situations were observed, an additional 10 mL (5 mL + 5 mL) of anesthetic solution was administered in both groups. If they persisted despite the additional dose, they were accepted as persistent incomplete block before surgery, and general anesthesia was administered. Preoperative bilateral complete loss of cold sensation to T8 and the absence of a patient complaining of discomfort during surgery was defined as "excellent surgical conditions." In patients complaining of discomfort, if the additional dose had not previously been administered, it was now given. Patients complaining of discomfort despite the additional injection already given were asked if they would like sedation. This was given as propofol and fentanyl (bolus induction dose 0.5 mg/kg of propofol and 1 µg/kg of fentanyl IV followed by propofol 1-2 mL/min and 1 µg/kg of fentanyl bolus every half hour). If complaints persisted despite this sedation, they were accepted as inadequate anesthesia, and general anesthesia was given.
Arterial blood pressure, heart rate, and oxygen saturation were measured and recorded every 5 min for the duration of the surgical procedure. Hypotension (systolic blood pressure <70% of baseline), bradycardia, (heart rate <50 bpm), and desaturation (Spo2 <90%) were recorded. Hypotension was treated with IV ephedrine 5-15 mg and bradycardia with 0.5 mg of IV atropine; desaturation was treated with oxygen via a face mask. The type and duration of surgical procedures, and amount of perioperative IV fluid given were documented.
The primary outcome was excellent surgical condition, and a 15% difference in the incidence of the excellent surgical condition was considered to be clinically important. According to a priori power analysis, 114 patients were sufficient to provide 90% power to detect this difference between groups, accepting a two-tailed (
) error of 5%. However, obstetric patients (20 in the needle group and 22 in the catheter group) were excluded because they differ anatomically from other surgical patients. A post hoc power analysis was performed with respect to the observed difference of 89.6%-72.9%, with the sample size of 96 in each group. The power was calculated as 84% with a two-tailed () error of 5%. Catheter-related complications, including paresthesia during catheterization, inability to thread the catheter, and inadvertent intrathecal and IV catheterization were secondary outcomes.
Statistical analysis was performed by SPSS for Windows (version 10.0) statistical package (SPSS Inc., Chicago, IL). Patient characteristics were analyzed using the t-test for independent groups. Block height was compared using Wilcoxon rank sum test. Perioperative anesthesia quality and incidences of catheter-related complications were analyzed using the 
2 test in a 2 x 2 contingency table or Fisher exact test in 2 x 2 contingency table. Values are presented as numbers (%), mean ± sd, or median (range). A P value < 0.05 was considered statistically significant.
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Results |
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Significantly more patients required catheter removal because of IV or subarachnoid cannulation or inability to advance the catheter in the catheter group (13 [13.3%] versus 4 [4%]; P < 0.02). In 13 patients in the catheter group, catheter insertion was attempted through another space. In two of these, IV placement was again detected, and general anesthesia was instituted.
Anesthesia quality is shown in Table 6. Excellent surgical conditions were more frequently encountered in the needle group (86 [89.6%] versus 70 [72.9%]; P < 0.003). The catheters were reinjected during the surgery as required. There was no difference between the groups in the number of patients who required reinjection through the catheter as demonstrated in Table 6. Despite the additional injections, 4 (4.2%) patients in the needle group and 11 (11.5%) in the catheter group complained of discomfort. Therefore, they were accepted as having inadequate anesthesia and were either sedated or underwent general anesthesia.
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Discussion |
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Paresthesia during epidural catheter insertion has been reported in up to 60% of parturients (10), and the frequency of venous and subarachnoid cannulation has been reported between 0.2% and 11% and between 0.26% (11) and 0.6% (12), respectively. Paresthesia may be associated with transient or permanent neurological injury (13) and may be unpleasant for the patient. Unnoticed venous and subarachnoid cannulation may lead to convulsions, total spinal anesthesia, or postdural puncture headache.
Expansion of the epidural space by priming it with local anesthetic before advancement of the catheter may reduce the likelihood of both paresthesia and inadvertent venous or subarachnoid cannulation (14,15). Rolbin et al. (7) and Scott and Beilby (8) reported no advantage in injecting fluid into the epidural space before catheter insertion, but they administered much smaller volumes of fluid (3 and 5 mL, respectively) for priming. However, Mannion et al. (4), Tseng et al. (5), and Gadalla et al. (6) all noted a significant reduction in the incidence of extradural vein cannulation by routinely injecting 10 mL of saline priming fluid into the epidural space before catheter insertion. Saline, however, dilutes the local anesthetic injected; in this study, we therefore administered a single-injection dose of local anesthetic (20 mL) as a priming solution.
Despite a correct technique, some segments may remain unblocked because of inadequate spread of local anesthetic within the epidural space. This may be related to variations in epidural anatomy (16), although a transforaminal or anterior catheter positioning is a more likely explanation (2,7,17). Suboptimal positioning of the epidural catheter is common. Using radiography, Sanchez et al. (18) and Bridenbaugh et al. (19) showed that the intended catheter placement was often not achieved. Lim et al. (20) found that the catheter tip could be advanced without coiling for 4 cm or less in only 13% of cases. Hogan (21) found that lateral catheter deviation is a more common cause of asymmetric block than anatomic barriers to the spread of the local anesthetic solution. When epidural anesthesia is incomplete, additional injections or catheter manipulation may provide reliable surgical anesthesia, suggesting suboptimal positioning of the catheter.
Both the type of catheter (22) and its optimal depth of insertion (3,23) have been questioned. We used a multi-port epidural catheter inserted only 3 cm in the epidural space; these catheters give better anesthesia and require less manipulation than uniport ones (22), and insertion to no more than 3-4 cm into the epidural space minimizes complications and the incidence of inadequate anesthesia, even in obstetric patients (17). Our single-injection dose via epidural needle before catheter placement led to fewer cases of catheter replacement and inadequate anesthesia. Although no imaging method was used in this study, in view of the possibility of the suboptimal positioning and the malfunction of the epidural catheter, as mentioned above, injection through the epidural needle resulted in a more even distribution of local anesthetic solution and a more adequate anesthetic action.
Thus, this single-injection administration before catheter insertion offers the advantages of a single injection technique plus the flexibility of epidural catheterization. The requirement of relatively large volumes of local anesthetic as priming solution in the single-injection/catheter technique may be a disadvantage, and the direct catheter technique is preferable if it is essential to restrict dose and level block in special patients.
In summary, we report that the administration of local anesthetics through the epidural needle before epidural catheter placement improves the quality of epidural anesthesia and decreases the risk of catheter-related complications.
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This article has been cited by other articles:
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  J. M. Mhyre, M. L. V. H. Greenfield, L. C. Tsen, and L. S. Polley A Systematic Review of Randomized Controlled Trials That Evaluate Strategies to Avoid Epidural Vein Cannulation During Obstetric Epidural Catheter Placement Anesth. Analg., April 1, 2009; 108(4): 1232 - 1242. [Abstract] [Full Text] [PDF]
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R. Mahajan, A. Sharma, and R. Gupta A Contraindication to Using Local Anesthetic Solution for Expanding the Epidural Space Anesth. Analg., December 1, 2006; 103(6): 1585 - 1586. [Full Text] [PDF]
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M. Cesur, H. A. Alici, A. F. Erdem, F. Silbir, and M. S. Yuksek A Contraindication to Using Local Anesthetic Solution for Expanding the Epidural Space Anesth. Analg., December 1, 2006; 103(6): 1586 - 1586. [Full Text] [PDF]
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