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AMBULATORY ANESTHESIA

The Anesthetic and Recovery Profile of Two Doses (60 and 80 mg) of Plain Mepivacaine for Ambulatory Spinal Anesthesia

Julius Pawlowski, MD^*, Radha Sukhani, MD^*, Ana L. Pappas, MD^*, Ku-Mie Kim, MD^*, Jordan Lurie, MD^*, Helena Gunnerson, MD^*, Andrea Corsino, RN, BSN^*, Kere Frey, DO^*, and Pietro Tonino, MD

Departments of *Anesthesiology and Orthopedics, Loyola University Medical Center, Maywood, Illinois

Address correspondence to Julius Pawlowski, MD, Department of Anesthesiology, Loyola University Medical Center, 2150 S. First Ave., Maywood, IL 60153.

	Abstract

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Reports of transient neurological symptoms with the use of subarachnoid lidocaine has generated interest in alternate local anesthetics of intermediate duration, such as mepivacaine. This prospective randomized, double-blinded, dose-response study examined the anesthetic and recovery profiles of 60- and 80-mg doses of preservative-free plain mepivacaine for ambulatory spinal anesthesia. Sixty patients undergoing ambulatory anterior cruciate ligament repair of the knee under spinal anesthesia were randomized into two groups; Group 1 (29 patients) received 4 mL of 1.5% (60-mg dose) and Group 2 (31 patients) received 4 mL of 2% (80-mg dose) of plain mepivacaine. All patients received a combined spinal-epidural anesthetic technique. The epidural catheter was used only in the event the surgery outlasted the duration of surgical anesthesia with subarachnoid mepivacaine. Epidural supplementation was administered in three patients (12%) in Group 1 and one patient (3%) in Group 2 when the sensory block regressed to L-1 with surgery expected to last longer than 15 min. The cephalad dermatome level of the block and degree of motor block was comparable in the two groups. Times to two-segment and T-10 regression were comparable in the two groups (112 ± 26 min in Group 1 versus 122 ± 28 min in Group 2). Time to L-1 regression was significantly longer in Group 2 (146 ± 28 min in Group 1 versus 159 ± 19 min in Group 2). All of the ambulatory milestones were significantly faster in Group 1. Side effects, such as hypotension and emesis were negligible, severe bradycardia and urinary retention did not occur, and none of the patients in the two groups reported transient neurological symptoms over 24 h. In conclusion, plain mepivacaine in a 60- or 80-mg dose is a suitable local anesthetic choice for ambulatory spinal anesthesia with respect to anesthetic, as well as recovery profiles.

Implications: We evaluated the anesthetic and recovery profiles of 60- and 80-mg doses of plain mepivacaine for ambulatory spinal anesthesia. Both doses produced comparable sensory and motor block. Sensory and motor regression and ambulatory milestones were 20–30 min longer with the 80-mg dose. Side effects were negligible and transient neurological symptoms were not reported during a 24-h follow-up.

	Introduction

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The use of spinal anesthesia has gained popularity in the ambulatory surgery setting. Benefits include rapid onset of anesthesia, excellent surgical conditions, avoidance of airway manipulation, minimal or no postoperative emesis, minimal postoperative nursing care requirements, and a smooth transition to postoperative analgesia (1). Among the drawbacks are backache and prolonged discharge times secondary to delays in voiding (1–6).

Lidocaine, because of its relatively short duration of action, is ideal for ambulatory spinal anesthesia. However, reports of transient neurological symptoms (TNS) occurring in 16% to 40% of the patients associated with the use of spinal lidocaine has generated interest in the alternative local anesthetics of intermediate duration, such as mepivacaine (2–7). One study using mepivacaine versus lidocaine for ambulatory spinal anesthesia demonstrated no TNS with mepivacaine and 22% TNS with lidocaine (5). Although mepivacaine appears to be a promising alternative to lidocaine for ambulatory spinal anesthesia, clinical data on its dose versus anesthetic and recovery profiles in ambulatory patients are limited (5–7). The purpose of this randomized, double-blinded, prospective study was to compare the anesthetic and recovery profiles of two doses of plain mepivacaine (60 mg and 80 mg) in patients receiving spinal anesthesia for ambulatory anterior cruciate ligament (ACL) repair.

	Methods

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After institutional review board approval and informed written consent, 60 patients, 18–50 yr of age, classified as ASA physical status I and II who agreed to having ACL repair done under combined spinal-epidural (CSE) anesthesia technique participated. The epidural catheter was used only in the event the surgery outlasted the duration of surgical anesthesia provided by subarachnoid mepivacaine. A power analysis to determine the number of cases to be studied could not be done because of the lack of published data on the mean time to regression of motor and sensory block and recovery of ambulatory milestones after mepivacaine spinal anesthesia. Therefore, the number of patients, 30 in each group, was selected arbitrarily.

Patients were excluded from the study for the following reasons: 1) if neuraxial block was contraindicated; 2) if there was a known history of hypersensitivity to local anesthetics; 3) if they were morbidly obese (>50% of ideal body weight) or were in extremes of height (<145 cm or >185 cm) or had a history of ₂ adrenergic agonist intake; or 4) if they had neurological deficits that could interfere with data collection for motor and sensory recovery (8).

Patients were randomly assigned by using a computer-generated sequence to receive spinal anesthesia with either 60 mg or 80 mg of preservative-free, plain solution of mepivacaine (Abbott Laboratories, North Chicago, IL). Patients in Group 1 received 4 mL of 1.5% (60 mg) solution of plain mepivacaine and patients in Group 2 received 4 mL of 2% (80 mg) solution of plain mepivacaine. Mepivacaine solutions for subarachnoid injection were prepared by an investigator who did not participate in the anesthetic care of the patient and data collection.

Preoperatively IV infusion of lactated Ringer’s solution was initiated. Patients were sedated with 2–4 mg of midazolam. The total amount of IV fluids for the entire perioperative period was restricted to 1,000 mL. Of this fluid, 200–300 mL was infused before injection of subarachnoid mepivacaine. Routine monitoring was used. In all patients, CSE was performed at L2-3 or L3-4 interspace with patients in a sitting position using a midline approach. An 18-gauge, 3.5 in. epidural needle and a 27-gauge spinal needle assembly was used for CSE. The epidural space was identified and the spinal needle was placed through an epidural needle for lumbar puncture. Once a clear free flow of cerebrospinal fluid (CSF) was identified, an appropriate dose of plain mepivacaine solution was administered. Ability to aspirate CSF was assessed after each 1-mL increment of subarachnoid injection. The spinal needle was then removed and a 20-gauge epidural catheter was inserted 3–4 cm into the epidural space. A test dose was not administered through the epidural catheter.

Supplementation of mepivacaine spinal anesthesia with epidural local anesthetic was instituted according to the following criteria: 1) surgeon observation of inadequate muscle relaxation interfering with surgery; 2) sensory regression to L-1 dermatome with expected surgery completion time exceeding 15 min; or 3) any patient complaint of discomfort at the surgical site. Criterion 2 was based on the institutional experience with the use of 60 mg of spinal mepivacaine. Supplemental epidural local anesthetic consisted of 10–15 mL of preservative-free 3% chloroprocaine (Nesacaine^®-MPF; Astra USA, Westborough, MA) administered in 5 mL increments (maximum 15 mL) 3–5 min apart until a T-10 sensory dermatome level was achieved. Patients who received epidural supplementation were excluded from the early recovery data collection.

Bradycardia was defined as a heart rate of <45 bpm and hypotension, as a systolic blood pressure of 80 mm Hg. Hypotension was treated with 5-mg increments of ephedrine and isolated bradycardia with 0.2-mg increments of atropine. To ensure adequate sedation during surgery, patients received a propofol infusion adjusted (50–75 µg · kg^-1 · min^-1) to an observer’s assessment of alertness/sedation score of 3 (asleep but responsive to verbal/physical stimulation) (9). Narcotics were not used intraoperatively.

All patients had an autograft middle third patellar tendon ACL reconstruction. A medial parapatellar skin incision was used for insolation of the middle third patellar tendon graft and a small lateral incision was used for drilling the femoral tunnel. In each case, a drain was placed at the end of the procedure. On completion of the procedure, all operated knees were placed in cryocuff and knee immobilizer before transfer to the postanesthesia care unit (PACU).

To control postoperative pain, all patients received femoral 3-in-1 nerve block according to the technique described by Winnie et al. (10) by using 25–30 mL of 0.5% bupivacaine with epinephrine 1:200,000 at the conclusion of surgery. In the PACU, patients were ambulated on crutches when they had complete motor recovery (Bromage 0) and sensory recovery of feet and buttocks (unoperated lower extremity). Patients were discharged home when they met the following criteria: stable vital signs; pain score <4; ambulating on crutches; successful voiding; and free of nausea, vomiting, and dizziness. All of the patients were followed up by a research nurse 24 h after their discharge from the PACU to identify delayed complications, such as TNS, postdural puncture headache (PDPH), emetic sequelae, and voiding difficulty. TNS was defined as back pain or dysesthesia that radiated to the buttocks, thighs, hips, or calves by using criteria of Pollock et al. (2).

Data on patient demographics, anesthesia induction time (time interval in minutes between patient arrival at the operating room until surgical preparation), durations of surgery, and onset and regression of sensory and motor block were collected. Level of sensory block was assessed by pinprick and the degree of motor block was assessed by using the Bromage scale: 0 = no paresis, full movement at knee, hip, and ankle, 1 = able to flex knee and ankle only, 2 = able to flex ankle only, 3 = complete paralysis. Assessment of sensory and motor block was done on the unoperated lower extremity every 5 min for the first 20 min and subsequently every 15 min until complete sensory and motor (Bromage 0) recovery.

Early recovery variables included times from subarachnoid injection until ambulation with crutches and successful voiding. Patients were considered ready for discharge when they had successfully voided (no feeling of bladder fullness and or dribbling). The voiding time, therefore, is synonymous with the discharge time. Late recovery variables included the incidence of TNS, PDPH, voiding difficulties, and emetic sequelae occurring within the 24-h period after discharge. Patients were excluded from early recovery data collection, if they had a dural puncture with the epidural needle or if supplemental epidural local anesthetic was administered.

One-way analysis of variance was used to compare the sensory and motor regression. Demographic variables, durations of anesthesia and surgery, and times to achieve ambulatory milestones were compared by using unpaired Student’s t-test, ² test, or Fisher’s exact test, as appropriate, to compare the incidence of side effects and complications.

	Results

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Of the 60 patients enrolled in the study, 29 patients received 60 mg of mepivacaine (Group 1) and 31 patients received 80 mg of mepivacaine (Group 2). Two patients (one in each group) were excluded from early recovery data collection because of inadvertent dural puncture with the epidural needle. Four patients (three patients in Group 1 and one patient in Group 2) were given epidural local anesthetic supplementation because they met Criterion 2 for supplementation, i.e., sensory regression to L-1 with expected duration of surgery exceeding 15 min. The times from subarachnoid local anesthetic injection to epidural supplementation in three Group 1 patients ranged between 60 to 80 min. One patient in Group 2 received epidural local anesthetic supplementation before surgical incision because of inadequate anesthesia of L-2. These four patients who received epidural local anesthetic supplementation were also excluded from early recovery data collection. Early recovery data therefore, are representative of 25 patients in Group 1 and 29 patients in Group 2. Late recovery data for delayed complications, such as PDPH, TNS, emetic sequelae, and voiding difficulties were compiled together for the two groups. Of the 60 patients enrolled, three patients were lost to 24-h follow-up. The late recovery data, therefore, are representative of 57 patients (30 patients in Group 1 and 27 patients in Group 2).

Demographic variables were comparable between the two groups. (Table 1) Durations of anesthesia and surgery, cephalad dermatome level of block, and times to the onset of sensory and complete motor block (Bromage 3) did not differ significantly between the two groups. (Tables 1 and 2) Paresthesia during spinal needle placement occurred in one patient and sudden movement in this patient resulted in accidental dural puncture with the epidural needle. Satisfactory surgical anesthesia was achieved in all of the cases. None of the patients in either group had inadequate muscle relaxation or discomfort because of inadequate surgical anesthesia.

View larger version (44K): [in this window] [in a new window]   Figure 1. Times from subarachnoid mepivacaine injection to two dermatome sensory regression, T-10 and L-1 dermatomes, complete sensory recovery, complete motor recovery (Bromage 0), and the fulfillment of ambulatory milestones, ie., ambulation and voiding. = Group 1 (60 mg of mepivacaine); = Group 2 (80 mg mepivacaine). *Statistically significant longer (P < 0.05).

	Discussion

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Reports of TNS have generated an interest in the alternative local anesthetics to lidocaine for ambulatory spinal anesthesia (4–6). Subarachnoid plain mepivacaine produces a rapid, reliable, and dense block of intermediate duration (11–14). Recent studies using mepivacaine for spinal anesthesia have reported no or less incidence of TNS with spinal mepivacaine compared with spinal lidocaine (6,7). The substitution of plain mepivacaine for lidocaine however can be considered for ambulatory spinal anesthesia only after mepivacaine’s anesthetic and recovery profiles are known, including the risk of TNS. We focused primarily on the anesthetic and immediate recovery (ambulatory milestones) profiles of two doses of spinal mepivacaine.

Our results demonstrate that when used for spinal anesthesia, doses of 60 mg or 80 mg plain mepivacaine produce comparable levels of sensory block and a similar degree of motor block. As would be expected, the 60-mg dose resulted in a significantly faster regression of motor and sensory block, and, therefore, a more expeditious recovery of ambulation and voiding. However, because of a significantly faster sensory regression to L-1 dermatome, three patients (12%) in the 60 mg of mepivacaine group versus only one patient (3%) in the 80 mg of mepivacaine group received supplemental local anesthetics through the epidural catheter to ensure surgical anesthesia for knee surgery (L-2-4 innervation). The incidence of hypotension in both groups was minimal. Severe bradycardia, intraoperative emesis, or TNS over a 24-hour follow-up period were not observed in any of the patients in the two groups.

CSE serves as an ideal study model to evaluate the anesthetic profile of subarachnoid local anesthetics because an indwelling epidural catheter offers the flexibility of extending the duration of surgical anesthesia from spinal local anesthetics. We opted to use sensory regression to L-1 dermatome as an end point for epidural local anesthetic supplementation (Criterion 2). This criterion was based on the institutional experience with the use of 60 mg spinal mepivacaine that suggested a time lag of approximately 15–20 minutes between L-1 and L-2 sensory regression. Because the sensory innervation of the knee is L2-4 we presumed that Criterion 2 will allow us to prevent patient discomfort from inadequate anesthesia. It is possible that sensory block may have remained at the L-1 level and may have remained long enough for completion of the surgery, especially when a larger dose i.e., 80 mg of spinal mepivacaine was used.

Latency of sensory and motor block, cephalad dermatome level of block, and degree of motor block (Bromage 3) were comparable between the two groups. Previous studies using plain solution of intrathecal mepivacaine have reported a wide variation in the cephalad dermatome levels of the sensory block among patients (11–13). Contrary to these published reports, cephalad dermatome level of the block obtained with both doses of plain mepivacaine was consistent in our study (Table 2). The cephalad dermatome level of block we obtained is comparable to that reported by Urmey et al. (15) using 60 mg (T-2 to T-7) and 80 mg (T-1 to T-5) of 2% plain lidocaine for spinal anesthesia.

Ambulatory milestones i.e., times from subarachnoid injection to ambulation and voiding were 212 ± 25 and 232 ± 25 minutes, respectively, using 60 mg of plain mepivacaine in our study. Increasing the dose to 80 mg prolonged the ambulatory milestones by 20–30 minutes. Ligouri et al. (5) used 45 mg of 1.5% plain mepivacaine for ambulatory spinal anesthesia; times to ambulation and voiding reported by these authors were 180 ± 34 and 201 ± 41 minutes, respectively. The data from our study and that from the study by Ligouri et al. (5) suggest that for each 15–20 mg increase in the dose of subarachnoid mepivacaine there is a prolongation of ambulatory milestones by 20–30 minutes.

Our patient population was relatively young; mean age 33 ± 10 yr. The incidence of hypotension requiring therapeutic intervention was minimal and severe bradycardia did not occur (Table 2). In contrast, Boss and Schuh (14) reported a relatively higher cephalad spread of spinal anesthesia in the elderly (76–87 yrs) when 90 mg isobaric mepivacaine was used for spinal anesthesia. This higher spread may have contributed to a relatively greater decrease of blood pressure in the elderly patients in their study (14).

None of the patients in the present study reported TNS when questioned 24 hours after their surgery by using criteria of Pollock et al. (2). Ligouri et al. (5) reported a 22% incidence of TNS with 2% plain lidocaine in patients undergoing unilateral knee arthroscopy under spinal anesthesia. In contrast, none of the 30 patients in their study who received 1.5% plain mepivacaine for spinal anesthesia developed TNS. Although the authors did not encounter TNS with subarachnoid mepivacaine in their study population, they did report three cases of TNS after spinal anesthesia with mepivacaine at their institution. Additionally, there is a published report (16) of one case of TNS after spinal anesthesia with hyperbaric 4% mepivacaine. The symptoms of TNS in this patient occurred four hours postoperatively and resolved rapidly over the succeeding 24 hours. TNS after lidocaine spinal anesthesia may take up to one week to resolve (3,17).

One of the limitations of our study is that the patients were followed for only 24 hours of the postoperative period. Although published data suggest that most patients with TNS report their symptoms within 24 hours of spinal local anesthetic, the symptoms may occur up to 72 hours (2–5). Based on our data, therefore, we cannot claim that the use of spinal mepivacaine does not cause TNS.

In conclusion, plain mepivacaine in a 60-mg or 80-mg dose appears to be a suitable local anesthetic for ambulatory spinal anesthesia with respect to anesthetic as well as recovery profiles. In patients undergoing ambulatory ACL repair, use of 80 mg of mepivacaine for spinal anesthesia resulted in sensory regression to L-1 dermatome over 159 ± 19 minutes in 97% of the patients. Reducing the plain mepivacaine dose to 60 mg decreased this duration by 20–30 minutes. Discharge criteria (voiding) were also met 20–30 minutes faster in patients receiving 60 mg spinal mepivacaine (232 ± 25 minutes in Group 1 versus 253 ± 35 minutes in Group 2). Doses of 60 mg and 80 mg of plain mepivacaine for ambulatory spinal anesthesia were associated with minimal side effects with no reports of TNS on a 24-hour postoperative follow-up.

	References

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (9) Citing Articles via Google Scholar Google Scholar Articles by Pawlowski, J. Articles by Tonino, P. Search for Related Content PubMed PubMed Citation Articles by Pawlowski, J. Articles by Tonino, P.